Health Problem: Rhabdomyosarcoma (RMS) is the most common soft-tissue sarcoma diagnosed in children and the third most common pediatric extracranial solid tumor. Although progress in the treatment for RMS has led to improved survival, some children have nonresponsive or recurrent disease, and current treatment modalities can lead to long-term complications in survivors. Each year in the United States, approximately 340 children are newly diagnosed with RMS. The 5-year survival rate for persons 19 years of age or older improved from 49% in the late 1970s to 64% in the 2000s. The head and neck is the most common site for RMS, occurring in 36% of patients.
Technology Description: A form of external beam radiation treatment (EBRT), proton beam therapy (PBT) uses a sophisticated 3-dimensional stereotaxic planning and delivery system to precisely target protons (positively charged, heavy subatomic particles) to bombard a specific tumor mass. Whereas proton and photon techniques should have similar tumor control abilities, PBT is believed to improve sparing of normal tissues, reducing acute and late toxicities, which is especially important in children whose growing tissues and organs would be especially sensitive to radiation damage. Treatment planning for each patient who undergoes PBT requires computed tomography simulation, diagnostic magnetic resonance imaging scans, and custom immobilization. Anesthesia is used for patients who are too young or otherwise unable to tolerate the simulations and daily treatments while awake. Usually, PBT is delivered daily, 5 days a week, for 4 to 6 weeks. Daily pretreatment imaging guidance ensures the reproducibility of patient positioning during PBT.
Controversy: Since 1997, when U.S. pediatric oncology cooperative groups first began to incorporate PBT into their clinical trial protocols, the technology has been used to treat patients with RMS. The rationale for this use is that, compared with EBRT delivered as photons, PBT should reduce the risk of some short-term (acute) and long-term (late) toxicities by decreasing/eliminating radiation dose to the delicate normal tissues surrounding some tumors. However, the clinical data to support the theoretical benefits of PBT in children with cancer and, specifically, with RMS of the head and neck are limited.
Key Questions:
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Is PBT effective for treating children with RMS in the head and neck region?
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Is PBT safe in children with RMS in the head and neck region?
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Have definitive patient selection criteria been identified for PBT in children with RMS in the head and neck region?
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