- Smilow Cancer Hospital at Waterbury1075 Chase ParkwayWaterbury, CT 06708
Daniel O'Neil, MD, MPH
Biography
Daniel O’Neil, MD, MPH, is a medical oncologist who specializes in breast cancer.
“It’s incredibly rewarding to work with breast cancer patients,” Dr. O’Neil says. “I meet people during one of the most stressful moments in their lives, usually shortly after they've been diagnosed, and I have the opportunity to give them the information they need to make the best decisions about how to take care of their disease. I try to reassure them that they are making a good choice for themselves and for their families.”
Dr. O’Neil says he enjoys getting to know his patients and their families. “In many cases, breast cancer patients are cured completely. I get to see my patients for years afterwards as they've continued to live their lives and everything has returned to normal,” he says. “And even in cases where there is more aggressive or advanced disease, there is still an opportunity to help patients choose the right treatment to maintain their quality of life, to help them live with their disease for as long as possible, and to help them make good choices about what's important to them.”
At Smilow Cancer Hospital, a team approach is beneficial to patients, Dr. O’Neil says. “When you're being treated for breast cancer, there are the physicians you interact with directly, such as your surgeon, medical oncologist, and radiation oncologist. And then there are the doctors who are behind the scenes, like pathologists and radiologists, who interpret many of the tests that you're undergoing and are hugely important to your care,” he says.
Dr. O’Neil’s research is focused on understanding the quality of breast cancer care delivered in low- and middle-income countries. He is also interested in how HIV affects breast cancer mortality in women.
Titles
- Assistant Professor
- Affiliated Faculty, Yale Institute for Global Health
- Clinical Member, Yale Cancer Center
Education & Training
- Internal Medicine Intern/ResidentBrigham and Women's Hospital (2023)
- Global Health Equity ResidentBrigham and Women's Hospital (2023)
- Hematology/Oncology FellowColumbia University Irving Medical Center (2019)
- MPHHarvard T.H. Chan School of Public Health (2016)
- MDAlbert Einstein College of Medicine
Additional Information
- AB of Internal Medicine, Medical Oncology (2019)
- AB of Internal Medicine, Internal Medicine (2017)
- . The impact of HIV on non-adherence for tamoxifen among women with breast cancer in South Africa. Breast Cancer Research And Treatment 2022, 197: 647-659. PMID: 36538247, PMCID: PMC10149344, DOI: 10.1007/s10549-022-06835-6.
- . Impact of HIV infection on survival among women with stage I‐III breast cancer: Results from the South African breast cancer and HIV outcomes study. International Journal Of Cancer 2022, 151: 209-221. PMID: 35218568, PMCID: PMC9133061, DOI: 10.1002/ijc.33981.
- . The Impact of Breast Cancer Treatment Delays on Survival Among South African Women. The Oncologist 2022, 27: e233-e243. PMID: 35274708, PMCID: PMC8914482, DOI: 10.1093/oncolo/oyab054.
- . Validating an Instrument for Direct Patient Reporting of Distress and Chemotherapy-Related Toxicity among South African Cancer Patients. Cancers 2021, 14: 95. PMID: 35008258, PMCID: PMC8750185, DOI: 10.3390/cancers14010095.
- . Breast Cancer Early Detection in Eswatini: Evaluation of a Training Curriculum and Patient Receipt of Recommended Follow-Up Care. JCO Global Oncology 2021, 7: go.21.00124. PMID: 34491814, PMCID: PMC8423396, DOI: 10.1200/go.21.00124.
- . Impact of HIV infection on overall survival among women with stage IV breast cancer in South Africa. Breast Cancer Research And Treatment 2021, 189: 285-296. PMID: 34125339, PMCID: PMC9034410, DOI: 10.1007/s10549-021-06265-w.
- . Quality of Histopathological Reporting in Breast Cancer: Results From Four South African Breast Units. JCO Global Oncology 2021, 7: go.20.00402. PMID: 33434068, PMCID: PMC8081479, DOI: 10.1200/go.20.00402.
- . Identifying Breast Cancer Care Quality Measures for a Cancer Facility in Rural Sub-Saharan Africa: Results of a Systematic Literature Review and Modified Delphi Process. JCO Global Oncology 2020, 6: go.20.00186. PMID: 32997538, PMCID: PMC7529520, DOI: 10.1200/go.20.00186.
- . A comparison of complete pathologic response rates following neoadjuvant chemotherapy among South African breast cancer patients with and without concurrent HIV infection. Breast Cancer Research And Treatment 2020, 184: 861-872. PMID: 32875480, PMCID: PMC7658037, DOI: 10.1007/s10549-020-05889-8.
- . Breast Cancer Care Quality in South Africa’s Public Health System: An Evaluation Using American Society of Clinical Oncology/National Quality Forum Measures. Journal Of Global Oncology 2019, 5: jgo.19.00171. PMID: 31770052, PMCID: PMC6882520, DOI: 10.1200/jgo.19.00171.
- Joffe M, Chen W, Craig A, O'Neil D, Neugut A, Jacobson J, Ruff P, Mathiba R, Murugan N, Cubasch H, Blanchard C, Nietz S, Edge J, Buccimazza I, Čačala S, McCormack V, Pumpalova Y, Norris S. Overall survival, poverty differentials and mediating pathways among women with breast cancer: South African Breast Cancer and HIV Outcomes Cohort. The Oncologist 2025, oyaf408. PMID: 41389285, DOI: 10.1093/oncolo/oyaf408.
- Ream M, Taub C, Amonoo H, Walsh E, Popok P, Plotke R, Jacobs J, Gudenkauf L, Penedo F, O'Neil D, Ironson G, Safren S, Antoni M. Brief Post‐Surgical Stress Management Intervention Effects on Positive Psychological Well‐Being and Self‐Efficacy in Women Being Treated With Adjuvant Endocrine Therapy for Hormone‐Receptor Positive Breast Cancer. Psycho-Oncology 2025, 34: e70267. PMID: 40846861, PMCID: PMC12373568, DOI: 10.1002/pon.70267.
- Joffe M, Chen W, Craig A, O'Neil D, Jacobson J, Neugut A, Ruff P, Mathiba R, Murugan N, Cubasch H, Nietz S, Edge J, Buccimazza I, Čačala S, Stopforth L, Phakathi B, McCormack V, Norris S. Determinants of overall survival in the South African Breast Cancer and HIV Outcomes cohort. Journal Of Clinical Oncology 2025, 43: 11158-11158. DOI: 10.1200/jco.2025.43.16_suppl.11158.
- Bhangdia K, Natarajan A, Rudolfson N, Verguet S, Castro M, Dusengimana J, Shyirambere C, Schleimer L, Shulman L, Umwizerwa A, Kigonya C, Butonzi J, MacDuffie E, Fadelu T, O’Neil D, Nguyen C, Mpunga T, Keating N, Pace L. The association of travel distance and other patient characteristics with breast cancer stage at diagnosis and treatment completion at a rural Rwandan cancer facility. BMC Cancer 2025, 25: 146. PMID: 39865262, PMCID: PMC11771020, DOI: 10.1186/s12885-025-13489-2.
- Dubner J, Neugut A, Joffe M, O’Neil D, Ayeni O, Chen W, Buccimazza I, Čačala S, Stopforth L, Farrow H, Nietz S, Murugan N, Phakathi B, Jacobson J, Crew K, McCormack V, Ruff P, Cubasch H, Pumpalova Y. The association of HIV status with triple-negative breast cancer in patients with breast cancer in South Africa: a cross-sectional analysis of case-only data from a prospective cohort study. The Lancet Global Health 2024, 12: e1993-e2002. PMID: 39577973, PMCID: PMC11584318, DOI: 10.1016/s2214-109x(24)00376-0.
- O'Neil D, Blanchard C, Ream M, Mmoledi K, Mkwanazi N, Shandukani V, Ruff P, Antoni M, Joffe M. Associations between HIV infection status, psychosocial factors, and adjuvant endocrine therapy adherence among South African women with early-stage breast cancer. Journal Of Clinical Oncology 2024, 42: 522-522. DOI: 10.1200/jco.2024.42.16_suppl.522.
- O’Neil D. Breast Cancer Survival in Sub-Saharan Africa—Diversity Across Disparities. JAMA Network Open 2024, 7: e2410204. PMID: 38743427, DOI: 10.1001/jamanetworkopen.2024.10204.
- Macintyre J, D'Aoust R, Baker D, Hanson G, Gjolaj L, Negret L, O'Neil D. Fostering Oral Chemotherapy Understanding and Safety (FOCUS) Project: Interventions for Improving Knowledge and Compliance With National Safety Standards. Journal Of The Advanced Practitioner In Oncology 2024, 15: 1-7. PMID: 39563964, PMCID: PMC11572705, DOI: 10.6004/jadpro.2024.15.8.1.
- O’Neil D, Martei Y, Crew K, Castillo B, Costa P, Lim T, Michel A, Rubin E, Goel N, Hurley J, Lopes G, Antoni M. Time to Cancer Treatment and Chemotherapy Relative Dose Intensity for Patients With Breast Cancer Living With HIV. JAMA Network Open 2023, 6: e2346223. PMID: 38051529, PMCID: PMC10698616, DOI: 10.1001/jamanetworkopen.2023.46223.
- Mapanga W, Ayeni O, Chen W, Jacobson J, Neugut A, Ruff P, Cubasch H, O’Neil D, Buccimazza I, Čačala S, Stopforth L, Farrow H, Nietz S, Phakathi B, Chirwa T, McCormack V, Joffe M. The South African breast cancer and HIV outcomes study: Profiling the cancer centres and cohort characteristics, diagnostic pathways, and treatment approaches. PLOS Global Public Health 2023, 3: e0002432. PMID: 37874786, PMCID: PMC10597516, DOI: 10.1371/journal.pgph.0002432.
- O'Neil D, Blanchard C, Joffe M, Ream M, Tshabalala G, Diaz A, Chen W, Mkwanazi N, Blomberg B, Antoni M. Characterizing the mental health of South African women living with comorbid HIV and breast cancer. Journal Of Clinical Oncology 2023, 41: e12549-e12549. DOI: 10.1200/jco.2023.41.16_suppl.e12549.
- Dubner J, Neugut A, Joffe M, O'Neil D, Ayeni O, Chen W, Buccimazza I, Čačala S, Stopforth L, Farrow H, Nietz S, Phakathi B, Jacobson J, Crew K, Ruff P, Cubasch H, Pumpalova Y. The association of HIV and other risk factors with triple-negative breast cancer in South African women. Journal Of Clinical Oncology 2023, 41: 6583-6583. DOI: 10.1200/jco.2023.41.16_suppl.6583.
- Tshabalala G, Blanchard C, Mmoledi K, Malope D, O'Neil D, Norris S, Joffe M, Dietrich J. A qualitative study to explore healthcare providers’ perspectives on barriers and enablers to early detection of breast and cervical cancers among women attending primary healthcare clinics in Johannesburg, South Africa. PLOS Global Public Health 2023, 3: e0001826. PMID: 37159437, PMCID: PMC10168575, DOI: 10.1371/journal.pgph.0001826.
- Chiwambutsa S, Ayeni O, Kapungu N, Kanji C, Thelingwani R, Chen W, Mokone D, O'Neil D, Neugut A, Jacobson J, Ruff P, Cubasch H, Joffe M, Masimirembwa C. Effects of Genetic Polymorphisms of Drug Metabolizing Enzymes and co‐Medications on Tamoxifen Metabolism in Black South African Women with Breast Cancer. Clinical Pharmacology & Therapeutics 2023, 114: 127-136. PMID: 37042388, PMCID: PMC11016593, DOI: 10.1002/cpt.2904.
- O’Neil D, Ayeni O, Farrow H, Chen W, Demetriou G, Buccimazza I, Čačala S, Stopforth L, Joffe M, Antoni M, Lopes G, Pumpalova Y, Mapanga W, Jacobson J, Crew K, Neugut A, Ruff P, Cubasch H. The Impact of HIV Infection on Neoadjuvant and Adjuvant Chemotherapy Relative Dose Intensity in South African Patients with Breast Cancer. The Oncologist 2023, 28: e921-e929. PMID: 36943395, PMCID: PMC10546819, DOI: 10.1093/oncolo/oyad056.
- Mapanga W, Norris S, Craig A, Ayeni O, Chen W, Jacobson J, Neugut A, Ruff P, Cubasch H, O’Neil D, Buccimazza I, Čačala S, Stopforth L, Farrow H, Nietz S, Phakathi B, Chirwa T, McCormack V, Joffe M. Drivers of disparities in stage at diagnosis among women with breast cancer: South African breast cancers and HIV outcomes cohort. PLOS ONE 2023, 18: e0281916. PMID: 36795733, PMCID: PMC9934316, DOI: 10.1371/journal.pone.0281916.
- Ayeni O, Jofe M, Mapanga W, Chen W, O’Neil D, Phakathi B, Nietz S, Buccimazza I, Čačala S, Stopforth L, Jacobson J, Crew K, Neugut A, Ramiah D, Ruf P, Cubasch H, Chirwa T, McCormack V, Micklesfeld L, Norris S. Correction: Multimorbidity and overall survival among women with breast cancer: results from the South African Breast Cancer and HIV Outcomes Study. Breast Cancer Research 2023, 25: 14. PMID: 36721167, PMCID: PMC9890739, DOI: 10.1186/s13058-023-01611-w.
- Ayeni O, Joffe M, Mapanga W, Chen W, O’Neil D, Phakathi B, Nietz S, Buccimazza I, Čačala S, Stopforth L, Jacobson J, Crew K, Neugut A, Ramiah D, Ruff P, Cubasch H, Chirwa T, McCormack V, Micklesfield L, Norris S. Multimorbidity and overall survival among women with breast cancer: results from the South African Breast Cancer and HIV Outcomes Study. Breast Cancer Research 2023, 25: 7. PMID: 36691057, PMCID: PMC9872426, DOI: 10.1186/s13058-023-01603-w.
- MacIntyre J, D'Aoust R, Baker D, Hanson G, Gjolaj L, Simpson C, Negret L, O'Neil D. Fostering Oral Chemotherapy Understanding and Safety (FOCUS) Project: Interventions for improving knowledge and compliance with national safety standards. Journal Of Clinical Oncology 2022, 40: 370-370. DOI: 10.1200/jco.2022.40.28_suppl.370.
- O'Neil D, Demetriou G, Mmoledi K, Antoni M, Joffe M, Lopes G, Ruff P, Blanchard C. Validating an instrument for direct patient reporting of chemotherapy toxicity among South African cancer patients. Journal Of Clinical Oncology 2021, 39: 172-172. DOI: 10.1200/jco.2020.39.28_suppl.172.
- Pumpalova Y, Ayeni O, Chen W, O'Neil D, Nietz S, Phakathi B, Buccimazza I, Cacala S, Stopforth L, Farrow H, Joffe M, Mapanga W, Jacobson J, Crew K, Cubasch H, Ruff P, Neugut A. The impact of HIV infection on overall survival among women with stage IV breast cancer in South Africa. Journal Of Clinical Oncology 2021, 39: 6559-6559. DOI: 10.1200/jco.2021.39.15_suppl.6559.
- Nietz S, Ruff P, Chen W, O’Neil D, Norris S. Quality indicators for the diagnosis and surgical management of breast cancer in South Africa. The Breast 2020, 54: 187-196. PMID: 33120084, PMCID: PMC7593621, DOI: 10.1016/j.breast.2020.09.012.
- O’Neil D, Nxumalo S, Ngcamphalala C, Jacobson J, Nuwagaba-Biribonwoha H, Harripersaud K, Dlamini X, Pace L, Neugut A, Harris T. Evaluation of a Breast Cancer Early Detection Curriculum Among Nurses Working in 5 Antiretroviral Clinics in Eswatini. JCO Global Oncology 2020, 6: 14-14. DOI: 10.1200/go.20.80000.
- Natarajan A, Rudolfson N, O'Neil D, Schleimer L, Dusengimana J, Keating N, Shulman L, Mpunga T, Sebahungu F, Nguyen C, Umwizerwa A, Fadelu T, Shyirambere C, Kigonya C, Butonzi J, Pace L. Sociodemographic factors associated with cancer treatment completion among women with breast cancer at Butaro Cancer Center of Excellence (BCCOE) in Rwanda. Journal Of Clinical Oncology 2020, 38: e19220-e19220. DOI: 10.1200/jco.2020.38.15_suppl.e19220.
- Ratshikana-Moloko M, Ayeni O, Tsitsi J, Wong M, Jacobson J, Neugut A, Sobekwa M, Joffe M, Mmoledi K, Blanchard C, Mapanga W, Ruff P, Cubasch H, O'Neil D, Balboni T, Prigerson H. Spiritual Care, Pain Reduction, and Preferred Place of Death Among Advanced Cancer Patients in Soweto, South Africa. Journal Of Pain And Symptom Management 2020, 60: 37-47. PMID: 32045675, PMCID: PMC7311268, DOI: 10.1016/j.jpainsymman.2020.01.019.
- Ayeni O, Norris S, Joffe M, Cubasch H, Nietz S, Buccimazza I, Singh U, Čačala S, Stopforth L, Chen W, McCormack V, O'Neil D, Jacobson J, Neugut A, Ruff P, Micklesfield L. The multimorbidity profile of South African women newly diagnosed with breast cancer. International Journal Of Cancer 2019, 147: 361-374. PMID: 31600408, PMCID: PMC7649092, DOI: 10.1002/ijc.32727.
- O'Neil D, Accordino M, Wright J, Law C, Nitta S, Buono D, Abbott M, Ustoyev Y, Hu J, Neugut A, Hur C, Patel K, Hershman D. Use of nonclinical staff to coordinate oral anticancer drug prescriptions. Journal Of Clinical Oncology 2019, 37: 72-72. DOI: 10.1200/jco.2019.37.27_suppl.72.
- Brown J, Hershman D, O'Neil D, Brafman L, Fuentes D, Graafland L, Law C, Trivedi M, Kalinsky K, Crew K, Accordino M. A standardized workflow to improve the consent process among patients initiating an oral anticancer drug. Journal Of Clinical Oncology 2019, 37: 259-259. DOI: 10.1200/jco.2019.37.27_suppl.259.
- Schleimer L, Vianney Dusengimana J, Butonzi J, Kigonya C, Natarajan A, Umwizerwa A, O'Neil D, Costas-Chavarri A, Majyambere J, Shulman L, Keating N, Shyirambere C, Mpunga T, Pace L. Barriers to timely surgery for breast cancer in Rwanda. Surgery 2019, 166: 1188-1195. PMID: 31466858, PMCID: PMC6861658, DOI: 10.1016/j.surg.2019.06.021.
- Raab G, O’Neil D, Kiran R, Feingold D, Lee-Kong S, Horowitz D, Neugut A. Elevation of Serum CEA in Patients with Squamous Cell Carcinoma of the Anus. Cancer Investigation 2019, 37: 288-292. PMID: 31319725, DOI: 10.1080/07357907.2019.1636388.
- Raab G, Lin A, Hillyer G, Keller D, O'Neil D, Accordino M, Buono D, Hur C, Kiran R, Wright J, Hershman D, Neugut A. Use of Bevacizumab for Elderly Patients With Stage IV Colon Cancer: Analysis of SEER-Medicare Data. Clinical Colorectal Cancer 2019, 18: e294-e299. PMID: 31266707, DOI: 10.1016/j.clcc.2019.05.008.
- O'Neil D, Accordino M, Wright J, Law C, Nitta S, Buono D, Abbott M, Ustoyev Y, Cole E, Hu J, Neugut A, Hur C, Patel K, Hershman D. Delay in receipt of newly prescribed oral anticancer drugs. Journal Of Clinical Oncology 2019, 37: 6541-6541. DOI: 10.1200/jco.2019.37.15_suppl.6541.
- Neugut A, Lin A, Raab G, Hillyer G, Keller D, O'Neil D, Accordino M, Kiran R, Wright J, Hershman D. FOLFOX and FOLFIRI Use in Stage IV Colon Cancer: Analysis of SEER-Medicare Data. Clinical Colorectal Cancer 2019, 18: 133-140. PMID: 30878317, PMCID: PMC7379162, DOI: 10.1016/j.clcc.2019.01.005.
- Blanchard C, Ayeni O, O'Neil D, Prigerson H, Jacobson J, Neugut A, Joffe M, Mmoledi K, Ratshikana-Moloko M, Sackstein P, Ruff P. A Prospective Cohort Study of Factors Associated With Place of Death Among Patients With Late-Stage Cancer in Southern Africa. Journal Of Pain And Symptom Management 2019, 57: 923-932. PMID: 30708125, PMCID: PMC6531674, DOI: 10.1016/j.jpainsymman.2019.01.014.
- O'Neil D, Nietz S, Buccimazza I, Singh U, Čačala S, Stopforth L, Joffe M, Jacobson J, Neugut A, Crew K, Ruff P, Cubasch H. Neoadjuvant Chemotherapy Use for Nonmetastatic Breast Cancer at Five Public South African Hospitals and Impact on Time to Initial Cancer Therapy. The Oncologist 2018, 24: 933-944. PMID: 30518615, PMCID: PMC6656461, DOI: 10.1634/theoncologist.2018-0535.
- O’Neil D, Francescone M, Khan K, Alobeid B, O’Connor O, Sawas A. Erratum to “A Case of Bing–Neel Syndrome Successfully Treated with Ibrutinib”. Case Reports In Hematology 2018, 2018: 7610201. PMID: 30510817, PMCID: PMC6231375, DOI: 10.1155/2018/7610201.
- Schleimer L, Keating N, Shulman L, Anderson B, Duggan C, O’Neil D, Pace L. Review of Quality Measures for Breast Cancer Care by Country Income Level. Journal Of Global Oncology 2018, 4: 41s-41s. DOI: 10.1200/jgo.18.10480.
- O'Neil D, Francescone M, Khan K, Alobeid B, Bachir A, O'Connor O, Sawas A. A Case of Bing–Neel Syndrome Successfully Treated with Ibrutinib. Case Reports In Hematology 2018, 2018: 8573105. PMID: 30228918, PMCID: PMC6136466, DOI: 10.1155/2018/8573105.
- Sackstein P, O'Neil D, Neugut A, Chabot J, Fojo T. Epidemiologic trends in neuroendocrine tumors: An examination of incidence rates and survival of specific patient subgroups over the past 20 years. Seminars In Oncology 2018, 45: 249-258. PMID: 30348533, DOI: 10.1053/j.seminoncol.2018.07.001.
- O'Neil D, Prigerson H, Mmoledi K, Sobekwa M, Ratshikana-Moloko M, Tsitsi J, Cubasch H, Wong M, Omoshoro-Jones J, Sackstein P, Blinderman C, Jacobson J, Joffe M, Ruff P, Neugut A, Blanchard C. Informal Caregiver Challenges for Advanced Cancer Patients During End-of-Life Care in Johannesburg, South Africa and Distinctions Based on Place of Death. Journal Of Pain And Symptom Management 2018, 56: 98-106. PMID: 29604380, PMCID: PMC6082019, DOI: 10.1016/j.jpainsymman.2018.03.017.
- Schleimer L, Dusengimana J, Butonzi J, Kigonya C, Natarajan A, Umwizerwa A, O’Neil D, Shulman L, Keating N, Shyirambere C, Mpunga T, Pace L. Barriers to Timely Surgery for Breast Cancer in Rwanda. Journal Of Global Oncology 2018, 4: 28s-28s. DOI: 10.1200/jgo.18.22000.
- . Quality of Breast Cancer Treatment at a Rural Cancer Center in Rwanda. Journal Of Global Oncology 2017, 4: jgo.2016.008672. PMID: 30241207, PMCID: PMC6180813, DOI: 10.1200/jgo.2016.008672.
- . Evaluation of care access and hypertension control in a community health worker driven non-communicable disease programme in rural Uganda: the chronic disease in the community project. Health Policy And Planning 2016, 31: 878-883. PMID: 26962122, DOI: 10.1093/heapol/czw006.
- Smilow Cancer Hospital at Waterbury1075 Chase ParkwayWaterbury, CT 06708
Biography
Daniel O’Neil, MD, MPH, is a medical oncologist who specializes in breast cancer.
“It’s incredibly rewarding to work with breast cancer patients,” Dr. O’Neil says. “I meet people during one of the most stressful moments in their lives, usually shortly after they've been diagnosed, and I have the opportunity to give them the information they need to make the best decisions about how to take care of their disease. I try to reassure them that they are making a good choice for themselves and for their families.”
Dr. O’Neil says he enjoys getting to know his patients and their families. “In many cases, breast cancer patients are cured completely. I get to see my patients for years afterwards as they've continued to live their lives and everything has returned to normal,” he says. “And even in cases where there is more aggressive or advanced disease, there is still an opportunity to help patients choose the right treatment to maintain their quality of life, to help them live with their disease for as long as possible, and to help them make good choices about what's important to them.”
At Smilow Cancer Hospital, a team approach is beneficial to patients, Dr. O’Neil says. “When you're being treated for breast cancer, there are the physicians you interact with directly, such as your surgeon, medical oncologist, and radiation oncologist. And then there are the doctors who are behind the scenes, like pathologists and radiologists, who interpret many of the tests that you're undergoing and are hugely important to your care,” he says.
Dr. O’Neil’s research is focused on understanding the quality of breast cancer care delivered in low- and middle-income countries. He is also interested in how HIV affects breast cancer mortality in women.
Titles
- Assistant Professor
- Affiliated Faculty, Yale Institute for Global Health
- Clinical Member, Yale Cancer Center
Education & Training
- Internal Medicine Intern/ResidentBrigham and Women's Hospital (2023)
- Global Health Equity ResidentBrigham and Women's Hospital (2023)
- Hematology/Oncology FellowColumbia University Irving Medical Center (2019)
- MPHHarvard T.H. Chan School of Public Health (2016)
- MDAlbert Einstein College of Medicine
Additional Information
- AB of Internal Medicine, Medical Oncology (2019)
- AB of Internal Medicine, Internal Medicine (2017)
- . The impact of HIV on non-adherence for tamoxifen among women with breast cancer in South Africa. Breast Cancer Research And Treatment 2022, 197: 647-659. PMID: 36538247, PMCID: PMC10149344, DOI: 10.1007/s10549-022-06835-6.
- . Impact of HIV infection on survival among women with stage I‐III breast cancer: Results from the South African breast cancer and HIV outcomes study. International Journal Of Cancer 2022, 151: 209-221. PMID: 35218568, PMCID: PMC9133061, DOI: 10.1002/ijc.33981.
- . The Impact of Breast Cancer Treatment Delays on Survival Among South African Women. The Oncologist 2022, 27: e233-e243. PMID: 35274708, PMCID: PMC8914482, DOI: 10.1093/oncolo/oyab054.
- . Validating an Instrument for Direct Patient Reporting of Distress and Chemotherapy-Related Toxicity among South African Cancer Patients. Cancers 2021, 14: 95. PMID: 35008258, PMCID: PMC8750185, DOI: 10.3390/cancers14010095.
- . Breast Cancer Early Detection in Eswatini: Evaluation of a Training Curriculum and Patient Receipt of Recommended Follow-Up Care. JCO Global Oncology 2021, 7: go.21.00124. PMID: 34491814, PMCID: PMC8423396, DOI: 10.1200/go.21.00124.
- . Impact of HIV infection on overall survival among women with stage IV breast cancer in South Africa. Breast Cancer Research And Treatment 2021, 189: 285-296. PMID: 34125339, PMCID: PMC9034410, DOI: 10.1007/s10549-021-06265-w.
- . Quality of Histopathological Reporting in Breast Cancer: Results From Four South African Breast Units. JCO Global Oncology 2021, 7: go.20.00402. PMID: 33434068, PMCID: PMC8081479, DOI: 10.1200/go.20.00402.
- . Identifying Breast Cancer Care Quality Measures for a Cancer Facility in Rural Sub-Saharan Africa: Results of a Systematic Literature Review and Modified Delphi Process. JCO Global Oncology 2020, 6: go.20.00186. PMID: 32997538, PMCID: PMC7529520, DOI: 10.1200/go.20.00186.
- . A comparison of complete pathologic response rates following neoadjuvant chemotherapy among South African breast cancer patients with and without concurrent HIV infection. Breast Cancer Research And Treatment 2020, 184: 861-872. PMID: 32875480, PMCID: PMC7658037, DOI: 10.1007/s10549-020-05889-8.
- . Breast Cancer Care Quality in South Africa’s Public Health System: An Evaluation Using American Society of Clinical Oncology/National Quality Forum Measures. Journal Of Global Oncology 2019, 5: jgo.19.00171. PMID: 31770052, PMCID: PMC6882520, DOI: 10.1200/jgo.19.00171.
- Joffe M, Chen W, Craig A, O'Neil D, Neugut A, Jacobson J, Ruff P, Mathiba R, Murugan N, Cubasch H, Blanchard C, Nietz S, Edge J, Buccimazza I, Čačala S, McCormack V, Pumpalova Y, Norris S. Overall survival, poverty differentials and mediating pathways among women with breast cancer: South African Breast Cancer and HIV Outcomes Cohort. The Oncologist 2025, oyaf408. PMID: 41389285, DOI: 10.1093/oncolo/oyaf408.
- Ream M, Taub C, Amonoo H, Walsh E, Popok P, Plotke R, Jacobs J, Gudenkauf L, Penedo F, O'Neil D, Ironson G, Safren S, Antoni M. Brief Post‐Surgical Stress Management Intervention Effects on Positive Psychological Well‐Being and Self‐Efficacy in Women Being Treated With Adjuvant Endocrine Therapy for Hormone‐Receptor Positive Breast Cancer. Psycho-Oncology 2025, 34: e70267. PMID: 40846861, PMCID: PMC12373568, DOI: 10.1002/pon.70267.
- Joffe M, Chen W, Craig A, O'Neil D, Jacobson J, Neugut A, Ruff P, Mathiba R, Murugan N, Cubasch H, Nietz S, Edge J, Buccimazza I, Čačala S, Stopforth L, Phakathi B, McCormack V, Norris S. Determinants of overall survival in the South African Breast Cancer and HIV Outcomes cohort. Journal Of Clinical Oncology 2025, 43: 11158-11158. DOI: 10.1200/jco.2025.43.16_suppl.11158.
- Bhangdia K, Natarajan A, Rudolfson N, Verguet S, Castro M, Dusengimana J, Shyirambere C, Schleimer L, Shulman L, Umwizerwa A, Kigonya C, Butonzi J, MacDuffie E, Fadelu T, O’Neil D, Nguyen C, Mpunga T, Keating N, Pace L. The association of travel distance and other patient characteristics with breast cancer stage at diagnosis and treatment completion at a rural Rwandan cancer facility. BMC Cancer 2025, 25: 146. PMID: 39865262, PMCID: PMC11771020, DOI: 10.1186/s12885-025-13489-2.
- Dubner J, Neugut A, Joffe M, O’Neil D, Ayeni O, Chen W, Buccimazza I, Čačala S, Stopforth L, Farrow H, Nietz S, Murugan N, Phakathi B, Jacobson J, Crew K, McCormack V, Ruff P, Cubasch H, Pumpalova Y. The association of HIV status with triple-negative breast cancer in patients with breast cancer in South Africa: a cross-sectional analysis of case-only data from a prospective cohort study. The Lancet Global Health 2024, 12: e1993-e2002. PMID: 39577973, PMCID: PMC11584318, DOI: 10.1016/s2214-109x(24)00376-0.
- O'Neil D, Blanchard C, Ream M, Mmoledi K, Mkwanazi N, Shandukani V, Ruff P, Antoni M, Joffe M. Associations between HIV infection status, psychosocial factors, and adjuvant endocrine therapy adherence among South African women with early-stage breast cancer. Journal Of Clinical Oncology 2024, 42: 522-522. DOI: 10.1200/jco.2024.42.16_suppl.522.
- O’Neil D. Breast Cancer Survival in Sub-Saharan Africa—Diversity Across Disparities. JAMA Network Open 2024, 7: e2410204. PMID: 38743427, DOI: 10.1001/jamanetworkopen.2024.10204.
- Macintyre J, D'Aoust R, Baker D, Hanson G, Gjolaj L, Negret L, O'Neil D. Fostering Oral Chemotherapy Understanding and Safety (FOCUS) Project: Interventions for Improving Knowledge and Compliance With National Safety Standards. Journal Of The Advanced Practitioner In Oncology 2024, 15: 1-7. PMID: 39563964, PMCID: PMC11572705, DOI: 10.6004/jadpro.2024.15.8.1.
- O’Neil D, Martei Y, Crew K, Castillo B, Costa P, Lim T, Michel A, Rubin E, Goel N, Hurley J, Lopes G, Antoni M. Time to Cancer Treatment and Chemotherapy Relative Dose Intensity for Patients With Breast Cancer Living With HIV. JAMA Network Open 2023, 6: e2346223. PMID: 38051529, PMCID: PMC10698616, DOI: 10.1001/jamanetworkopen.2023.46223.
- Mapanga W, Ayeni O, Chen W, Jacobson J, Neugut A, Ruff P, Cubasch H, O’Neil D, Buccimazza I, Čačala S, Stopforth L, Farrow H, Nietz S, Phakathi B, Chirwa T, McCormack V, Joffe M. The South African breast cancer and HIV outcomes study: Profiling the cancer centres and cohort characteristics, diagnostic pathways, and treatment approaches. PLOS Global Public Health 2023, 3: e0002432. PMID: 37874786, PMCID: PMC10597516, DOI: 10.1371/journal.pgph.0002432.
- O'Neil D, Blanchard C, Joffe M, Ream M, Tshabalala G, Diaz A, Chen W, Mkwanazi N, Blomberg B, Antoni M. Characterizing the mental health of South African women living with comorbid HIV and breast cancer. Journal Of Clinical Oncology 2023, 41: e12549-e12549. DOI: 10.1200/jco.2023.41.16_suppl.e12549.
- Dubner J, Neugut A, Joffe M, O'Neil D, Ayeni O, Chen W, Buccimazza I, Čačala S, Stopforth L, Farrow H, Nietz S, Phakathi B, Jacobson J, Crew K, Ruff P, Cubasch H, Pumpalova Y. The association of HIV and other risk factors with triple-negative breast cancer in South African women. Journal Of Clinical Oncology 2023, 41: 6583-6583. DOI: 10.1200/jco.2023.41.16_suppl.6583.
- Tshabalala G, Blanchard C, Mmoledi K, Malope D, O'Neil D, Norris S, Joffe M, Dietrich J. A qualitative study to explore healthcare providers’ perspectives on barriers and enablers to early detection of breast and cervical cancers among women attending primary healthcare clinics in Johannesburg, South Africa. PLOS Global Public Health 2023, 3: e0001826. PMID: 37159437, PMCID: PMC10168575, DOI: 10.1371/journal.pgph.0001826.
- Chiwambutsa S, Ayeni O, Kapungu N, Kanji C, Thelingwani R, Chen W, Mokone D, O'Neil D, Neugut A, Jacobson J, Ruff P, Cubasch H, Joffe M, Masimirembwa C. Effects of Genetic Polymorphisms of Drug Metabolizing Enzymes and co‐Medications on Tamoxifen Metabolism in Black South African Women with Breast Cancer. Clinical Pharmacology & Therapeutics 2023, 114: 127-136. PMID: 37042388, PMCID: PMC11016593, DOI: 10.1002/cpt.2904.
- O’Neil D, Ayeni O, Farrow H, Chen W, Demetriou G, Buccimazza I, Čačala S, Stopforth L, Joffe M, Antoni M, Lopes G, Pumpalova Y, Mapanga W, Jacobson J, Crew K, Neugut A, Ruff P, Cubasch H. The Impact of HIV Infection on Neoadjuvant and Adjuvant Chemotherapy Relative Dose Intensity in South African Patients with Breast Cancer. The Oncologist 2023, 28: e921-e929. PMID: 36943395, PMCID: PMC10546819, DOI: 10.1093/oncolo/oyad056.
- Mapanga W, Norris S, Craig A, Ayeni O, Chen W, Jacobson J, Neugut A, Ruff P, Cubasch H, O’Neil D, Buccimazza I, Čačala S, Stopforth L, Farrow H, Nietz S, Phakathi B, Chirwa T, McCormack V, Joffe M. Drivers of disparities in stage at diagnosis among women with breast cancer: South African breast cancers and HIV outcomes cohort. PLOS ONE 2023, 18: e0281916. PMID: 36795733, PMCID: PMC9934316, DOI: 10.1371/journal.pone.0281916.
- Ayeni O, Jofe M, Mapanga W, Chen W, O’Neil D, Phakathi B, Nietz S, Buccimazza I, Čačala S, Stopforth L, Jacobson J, Crew K, Neugut A, Ramiah D, Ruf P, Cubasch H, Chirwa T, McCormack V, Micklesfeld L, Norris S. Correction: Multimorbidity and overall survival among women with breast cancer: results from the South African Breast Cancer and HIV Outcomes Study. Breast Cancer Research 2023, 25: 14. PMID: 36721167, PMCID: PMC9890739, DOI: 10.1186/s13058-023-01611-w.
- Ayeni O, Joffe M, Mapanga W, Chen W, O’Neil D, Phakathi B, Nietz S, Buccimazza I, Čačala S, Stopforth L, Jacobson J, Crew K, Neugut A, Ramiah D, Ruff P, Cubasch H, Chirwa T, McCormack V, Micklesfield L, Norris S. Multimorbidity and overall survival among women with breast cancer: results from the South African Breast Cancer and HIV Outcomes Study. Breast Cancer Research 2023, 25: 7. PMID: 36691057, PMCID: PMC9872426, DOI: 10.1186/s13058-023-01603-w.
- MacIntyre J, D'Aoust R, Baker D, Hanson G, Gjolaj L, Simpson C, Negret L, O'Neil D. Fostering Oral Chemotherapy Understanding and Safety (FOCUS) Project: Interventions for improving knowledge and compliance with national safety standards. Journal Of Clinical Oncology 2022, 40: 370-370. DOI: 10.1200/jco.2022.40.28_suppl.370.
- O'Neil D, Demetriou G, Mmoledi K, Antoni M, Joffe M, Lopes G, Ruff P, Blanchard C. Validating an instrument for direct patient reporting of chemotherapy toxicity among South African cancer patients. Journal Of Clinical Oncology 2021, 39: 172-172. DOI: 10.1200/jco.2020.39.28_suppl.172.
- Pumpalova Y, Ayeni O, Chen W, O'Neil D, Nietz S, Phakathi B, Buccimazza I, Cacala S, Stopforth L, Farrow H, Joffe M, Mapanga W, Jacobson J, Crew K, Cubasch H, Ruff P, Neugut A. The impact of HIV infection on overall survival among women with stage IV breast cancer in South Africa. Journal Of Clinical Oncology 2021, 39: 6559-6559. DOI: 10.1200/jco.2021.39.15_suppl.6559.
- Nietz S, Ruff P, Chen W, O’Neil D, Norris S. Quality indicators for the diagnosis and surgical management of breast cancer in South Africa. The Breast 2020, 54: 187-196. PMID: 33120084, PMCID: PMC7593621, DOI: 10.1016/j.breast.2020.09.012.
- O’Neil D, Nxumalo S, Ngcamphalala C, Jacobson J, Nuwagaba-Biribonwoha H, Harripersaud K, Dlamini X, Pace L, Neugut A, Harris T. Evaluation of a Breast Cancer Early Detection Curriculum Among Nurses Working in 5 Antiretroviral Clinics in Eswatini. JCO Global Oncology 2020, 6: 14-14. DOI: 10.1200/go.20.80000.
- Natarajan A, Rudolfson N, O'Neil D, Schleimer L, Dusengimana J, Keating N, Shulman L, Mpunga T, Sebahungu F, Nguyen C, Umwizerwa A, Fadelu T, Shyirambere C, Kigonya C, Butonzi J, Pace L. Sociodemographic factors associated with cancer treatment completion among women with breast cancer at Butaro Cancer Center of Excellence (BCCOE) in Rwanda. Journal Of Clinical Oncology 2020, 38: e19220-e19220. DOI: 10.1200/jco.2020.38.15_suppl.e19220.
- Ratshikana-Moloko M, Ayeni O, Tsitsi J, Wong M, Jacobson J, Neugut A, Sobekwa M, Joffe M, Mmoledi K, Blanchard C, Mapanga W, Ruff P, Cubasch H, O'Neil D, Balboni T, Prigerson H. Spiritual Care, Pain Reduction, and Preferred Place of Death Among Advanced Cancer Patients in Soweto, South Africa. Journal Of Pain And Symptom Management 2020, 60: 37-47. PMID: 32045675, PMCID: PMC7311268, DOI: 10.1016/j.jpainsymman.2020.01.019.
- Ayeni O, Norris S, Joffe M, Cubasch H, Nietz S, Buccimazza I, Singh U, Čačala S, Stopforth L, Chen W, McCormack V, O'Neil D, Jacobson J, Neugut A, Ruff P, Micklesfield L. The multimorbidity profile of South African women newly diagnosed with breast cancer. International Journal Of Cancer 2019, 147: 361-374. PMID: 31600408, PMCID: PMC7649092, DOI: 10.1002/ijc.32727.
- O'Neil D, Accordino M, Wright J, Law C, Nitta S, Buono D, Abbott M, Ustoyev Y, Hu J, Neugut A, Hur C, Patel K, Hershman D. Use of nonclinical staff to coordinate oral anticancer drug prescriptions. Journal Of Clinical Oncology 2019, 37: 72-72. DOI: 10.1200/jco.2019.37.27_suppl.72.
- Brown J, Hershman D, O'Neil D, Brafman L, Fuentes D, Graafland L, Law C, Trivedi M, Kalinsky K, Crew K, Accordino M. A standardized workflow to improve the consent process among patients initiating an oral anticancer drug. Journal Of Clinical Oncology 2019, 37: 259-259. DOI: 10.1200/jco.2019.37.27_suppl.259.
- Schleimer L, Vianney Dusengimana J, Butonzi J, Kigonya C, Natarajan A, Umwizerwa A, O'Neil D, Costas-Chavarri A, Majyambere J, Shulman L, Keating N, Shyirambere C, Mpunga T, Pace L. Barriers to timely surgery for breast cancer in Rwanda. Surgery 2019, 166: 1188-1195. PMID: 31466858, PMCID: PMC6861658, DOI: 10.1016/j.surg.2019.06.021.
- Raab G, O’Neil D, Kiran R, Feingold D, Lee-Kong S, Horowitz D, Neugut A. Elevation of Serum CEA in Patients with Squamous Cell Carcinoma of the Anus. Cancer Investigation 2019, 37: 288-292. PMID: 31319725, DOI: 10.1080/07357907.2019.1636388.
- Raab G, Lin A, Hillyer G, Keller D, O'Neil D, Accordino M, Buono D, Hur C, Kiran R, Wright J, Hershman D, Neugut A. Use of Bevacizumab for Elderly Patients With Stage IV Colon Cancer: Analysis of SEER-Medicare Data. Clinical Colorectal Cancer 2019, 18: e294-e299. PMID: 31266707, DOI: 10.1016/j.clcc.2019.05.008.
- O'Neil D, Accordino M, Wright J, Law C, Nitta S, Buono D, Abbott M, Ustoyev Y, Cole E, Hu J, Neugut A, Hur C, Patel K, Hershman D. Delay in receipt of newly prescribed oral anticancer drugs. Journal Of Clinical Oncology 2019, 37: 6541-6541. DOI: 10.1200/jco.2019.37.15_suppl.6541.
- Neugut A, Lin A, Raab G, Hillyer G, Keller D, O'Neil D, Accordino M, Kiran R, Wright J, Hershman D. FOLFOX and FOLFIRI Use in Stage IV Colon Cancer: Analysis of SEER-Medicare Data. Clinical Colorectal Cancer 2019, 18: 133-140. PMID: 30878317, PMCID: PMC7379162, DOI: 10.1016/j.clcc.2019.01.005.
- Blanchard C, Ayeni O, O'Neil D, Prigerson H, Jacobson J, Neugut A, Joffe M, Mmoledi K, Ratshikana-Moloko M, Sackstein P, Ruff P. A Prospective Cohort Study of Factors Associated With Place of Death Among Patients With Late-Stage Cancer in Southern Africa. Journal Of Pain And Symptom Management 2019, 57: 923-932. PMID: 30708125, PMCID: PMC6531674, DOI: 10.1016/j.jpainsymman.2019.01.014.
- O'Neil D, Nietz S, Buccimazza I, Singh U, Čačala S, Stopforth L, Joffe M, Jacobson J, Neugut A, Crew K, Ruff P, Cubasch H. Neoadjuvant Chemotherapy Use for Nonmetastatic Breast Cancer at Five Public South African Hospitals and Impact on Time to Initial Cancer Therapy. The Oncologist 2018, 24: 933-944. PMID: 30518615, PMCID: PMC6656461, DOI: 10.1634/theoncologist.2018-0535.
- O’Neil D, Francescone M, Khan K, Alobeid B, O’Connor O, Sawas A. Erratum to “A Case of Bing–Neel Syndrome Successfully Treated with Ibrutinib”. Case Reports In Hematology 2018, 2018: 7610201. PMID: 30510817, PMCID: PMC6231375, DOI: 10.1155/2018/7610201.
- Schleimer L, Keating N, Shulman L, Anderson B, Duggan C, O’Neil D, Pace L. Review of Quality Measures for Breast Cancer Care by Country Income Level. Journal Of Global Oncology 2018, 4: 41s-41s. DOI: 10.1200/jgo.18.10480.
- O'Neil D, Francescone M, Khan K, Alobeid B, Bachir A, O'Connor O, Sawas A. A Case of Bing–Neel Syndrome Successfully Treated with Ibrutinib. Case Reports In Hematology 2018, 2018: 8573105. PMID: 30228918, PMCID: PMC6136466, DOI: 10.1155/2018/8573105.
- Sackstein P, O'Neil D, Neugut A, Chabot J, Fojo T. Epidemiologic trends in neuroendocrine tumors: An examination of incidence rates and survival of specific patient subgroups over the past 20 years. Seminars In Oncology 2018, 45: 249-258. PMID: 30348533, DOI: 10.1053/j.seminoncol.2018.07.001.
- O'Neil D, Prigerson H, Mmoledi K, Sobekwa M, Ratshikana-Moloko M, Tsitsi J, Cubasch H, Wong M, Omoshoro-Jones J, Sackstein P, Blinderman C, Jacobson J, Joffe M, Ruff P, Neugut A, Blanchard C. Informal Caregiver Challenges for Advanced Cancer Patients During End-of-Life Care in Johannesburg, South Africa and Distinctions Based on Place of Death. Journal Of Pain And Symptom Management 2018, 56: 98-106. PMID: 29604380, PMCID: PMC6082019, DOI: 10.1016/j.jpainsymman.2018.03.017.
- Schleimer L, Dusengimana J, Butonzi J, Kigonya C, Natarajan A, Umwizerwa A, O’Neil D, Shulman L, Keating N, Shyirambere C, Mpunga T, Pace L. Barriers to Timely Surgery for Breast Cancer in Rwanda. Journal Of Global Oncology 2018, 4: 28s-28s. DOI: 10.1200/jgo.18.22000.
- . Quality of Breast Cancer Treatment at a Rural Cancer Center in Rwanda. Journal Of Global Oncology 2017, 4: jgo.2016.008672. PMID: 30241207, PMCID: PMC6180813, DOI: 10.1200/jgo.2016.008672.
- . Evaluation of care access and hypertension control in a community health worker driven non-communicable disease programme in rural Uganda: the chronic disease in the community project. Health Policy And Planning 2016, 31: 878-883. PMID: 26962122, DOI: 10.1093/heapol/czw006.
- Smilow Cancer Hospital at Waterbury1075 Chase ParkwayWaterbury, CT 06708
- Smilow Cancer Hospital at Waterbury1075 Chase ParkwayWaterbury, CT 06708