What could such symptoms as a bulging mass growing behind an eye, a growth on the testicles, and a painless lump on the leg have in common? Each may be a sign of rhabdomyosarcoma, a rare form of cancer that that affects children more often than adults—about 60% of all people who are diagnosed with rhabdomyosarcoma are children, and most are under age 7.
Rhabdomyosarcoma accounts for about 3% of cancer cases among children. It’s very rare, with only 400 or so cases diagnosed in the United States each year.
The prognosis for rhabdomyosarcoma varies, depending on the age of the person at diagnosis, the location of the tumor and how advanced the cancer is. Treatment is typically more successful among children than adults.
“Treatment of rhabdomyosarcoma varies depending on the location, size, and genetic features of the tumor,” says Juan Vasquez, MD, assistant professor of pediatrics (hematology/oncology) at Smilow Cancer Hospital. “Determining the best course of treatment for an individual requires a coordinated effort among highly trained specialists, including oncologists, surgeons, and radiation oncologists. Chemotherapy is an important part of treatment to help cure disease and prevent the cancer from coming back. For rhabdomyosarcoma that is located in the arms or legs, surgery is often used to remove the tumor. After surgery, radiation therapy may be used to help kill any remaining cancer cells. In cases when surgery is not possible, radiation therapy, in conjunction with chemotherapy, may be used to eliminate the tumor.”
What is rhabdomyosarcoma?
Rhabdomyosarcoma is a type of soft tissue cancer that develops in cells that were intended to develop into skeletal muscle tissue. However, rhabdomyosarcoma tumors appear—in most cases, actually—in body parts that don’t normally have skeletal muscle, such as the bladder.
In about 31% of cases, the cancer is located within the urinary tract, including the bladder, prostate, or vagina. Roughly 25% of the time, rhabdomyosarcoma is found in the head or neck. About 20% percent of the time, the cancer is located in an arm or leg. The remaining cases may be elsewhere, including within the trunk of the body.
What causes rhabdomyosarcoma?
In healthy people, tumor suppressor genes stop abnormal cells from multiplying uncontrollably. When a person has rhabdomyosarcoma, however, a tumor suppressor’s “on/off” switch may have been thrown into the “on” position, so that cells multiply when they shouldn’t, leading to the formation of a tumor.
Doctors aren’t sure what causes rhabdomyosarcoma. Most cases arise for unknown reasons. However, people may be more likely to develop this form of cancer if they have inherited gene mutations such as:
- Li-Fraumeni syndrome
- Neurofibromatosis type 1
- DICER1 syndrome
- Costello syndrome
- Beckwith-Wiedemann syndrome
- Noonan syndrome
- Cardio-facio-cutaneous syndrome
The genetic mutations associated with these conditions may allow abnormal cells to multiply, leading to tumor development. In some cases, a mutation to the p53 tumor suppressor gene allows cells to continue dividing when they shouldn’t, leading to the formation of a tumor. Other times, people with rhabdomyosarcoma may have portions of their DNA switch between chromosomes. This change, known as the PAX/FOX01 fusion gene, may lead to uncontrolled cell division and tumor formation.
What are the symptoms of rhabdomyosarcoma?
People experience different symptoms of rhabdomyosarcoma, depending on the location of the tumor.
When rhabdomyosarcoma is located in the urinary tract, an individual may experience:
- Difficulty urinating
- Blood in the urine
- A vaginal mass growing within the vagina (in females) or around the testicles (in males)
- An abdominal mass
When rhabdomyosarcoma is located in the head or neck, an individual may experience:
- Sinus infections/nasal congestion
- A change in the sound of the voice
- Discharge or bleeding from within the ear
- A growth developing within the ear canal
- One eye that bulges, due to a growth behind the eye
- Eye pain
- Becoming cross-eyed
When rhabdomyosarcoma develops on an arm or leg, an individual may develop:
- A painless or painful bulge or mass
- Swelling in the affected limb
If the cancer is located within the trunk, an individual may experience:
- Abdominal pain
How is rhabdomyosarcoma diagnosed?
To diagnose rhabdomyosarcoma, doctors will obtain a medical history, do a physical exam, and order imaging tests, as needed.
During a physical examination, doctors will examine the body part that has been exhibiting symptoms and feel any mass, if present, to note its size and texture.
Doctors may order blood tests or a cerebrospinal fluid test to rule out other conditions.
If they suspect that the mass may be cancerous, doctors will order one or more of the following imaging tests:
- CT scan
- PET scan
If the imaging study confirms the presence of a mass or lump, the doctors will biopsy the tissue to make a formal diagnosis. Tissue analysis and cancer staging can confirm the presence of rhabdomyosarcoma and also whether the cancer is classified as low, intermediate, or high risk.
Risk level is determined by finding out whether—and how far—the cancer has spread in the body and whether doctors believe that they will be able to surgically remove all of the cancer with a margin of healthy (non-cancerous) tissue.
How is rhabdomyosarcoma treated?
Treatment for rhabdomyosarcoma may vary, based on the location, size, and type of the tumor. Options include:
- Surgery. Doctors almost always recommend surgery to remove the tumor, plus a margin of healthy tissue. This isn’t always possible, because the tumor may be too large or located in a place where it can’t easily be removed (such as the eye, bladder, or vagina). In those cases, doctors typically prescribe chemotherapy to shrink the tumor. The cancer may later be removed surgically.
- Radiation therapy. After surgery, doctors may order radiation therapy to kill any remaining cancer cells. When surgical removal of the cancer isn’t feasible, radiation therapy may be used to help shrink the tumor, by itself or after a course of chemotherapy.
- Chemotherapy. Chemotherapy is nearly always prescribed after surgery for rhabdomyosarcoma—it helps to kill off any cancer cells that may have been left behind in the body. It may also be used to shrink the size of a larger tumor so that it may be surgically removed.
Other treatments may be available via clinical trials at Yale, such as the use of precision medicine to guide target and biologic therapies.
What is the outlook for people with rhabdomyosarcoma?
Between 70 and 90% of children with low-risk rhabdomyosarcoma survive 5 years or more after diagnosis. For those with intermediate risk, the 5-year survival rate goes down to about 50 to 70%. Among children with high risk, only 20 to 30% survive 5 years or longer, highlighting the importance of early diagnosis and treatment.
Adults who are diagnosed with rhabdomyosarcoma tend to have a poorer outcome than children do, often because the cancer grows more quickly and may be located in difficult-to-treat body parts. The 5-year survival rate adults with low-risk rhabdomyosarcoma is 47%.
What makes Yale unique in its treatment of rhabdomyosarcoma?
“At Yale, we treat children and adults with rhabdomyosarcoma through our Solid Tumor Program, which includes oncologists specializing in the treatment of sarcoma, along with surgeons, radiation oncologists, pathologists, and specialized radiologists,” says Dr. Vasquez. “We work together closely to make the diagnosis and determine the best course of treatment individualized to each patient’s disease and with the most advanced options possible.”
“At Yale, we also play an active role in several consortiums that run clinical trials for rhabdomyosarcoma, including the Children’s Oncology Group. Clinical trials for rhabdomyosarcoma may involve the study of new drugs or examine the most effective treatments with the least amount of side effects. For any patient with rhabdomyosarcoma, we will determine if there are clinical trials open and help patients and families understand the variety of treatment options available.”