Childhood Rhabdomyosarcoma Treatment (PDQ®): Treatment - Health Professional Information [NCI] - Previously Untreated Childhood Rhabdomyosarcoma
Table 5. Radiation Therapy (RT) Dose According to Rhabdomyosarcoma Group, Histology, and Site of Disease (Children's Oncology Group [COG])
|Group I|| |
|Alveolar||36 Gy to involved (prechemotherapy) site. The use of RT is under investigation.|
|Group II|| |
|N0 (microscopic residual disease after surgery)||36 Gy to involved (prechemotherapy) site.|
|N1 (resected regional lymph node involvement)||41.4 Gy to involved (prechemotherapy) site and nodes.|
|Group III|| |
|Orbital and nonorbital tumors||50.4 Gy with volume reduction after 36 Gy if excellent response to chemotherapy and noninvasive pushing tumors; no volume reduction for invasive tumors.|
|Group IV|| |
| ||As for other groups and including all metastatic sites, if safe and possible.Exception:lung (pulmonary metastases) treated with 15 Gy if aged 6 years or older, 12 Gy if younger than 6 years.|
- The RT dose depends predominantly on the amount of residual disease, if any, following the primary surgical resection. In general, patients with microscopic residual disease (Group II) receive RT to 36 Gy if they do not have involved lymph nodes and 41 Gy in the presence of involved nodes.[8,20,21] Low-risk patients (embryonal histology and favorable sites with microscopic residual disease) treated on a COG study had local control with 36 Gy, which was comparable to historic controls who received 41.4 Gy.IRS-II patients with gross residual disease (Group III) who received 40 Gy to more than 50 Gy had locoregional relapse rates greater than 30% but higher doses of radiation (>60 Gy) were associated with unacceptable long-term toxic effects.[23,24] Group III patients on the IRS-IV standard treatment arm received 50.4 Gy, with 5-year progression-free survival of 55% to 75%. Experience supports using a somewhat reduced dose of RT in patients with Group III disease who have delayed gross total resection with negative margins. In the recent COG-D9602 study, these patients had a greater than 85% likelihood of local control with 36 Gy.
- The treated volume should be determined by the extent of tumor at diagnosis prior to surgical resection and prior to chemotherapy. A margin of 2 cm is generally used, including clinically involved regional lymph nodes. While the volume irradiated may be modified on the basis of guidelines for normal tissue tolerance, gross residual disease at the time of radiation should receive full-dose treatment.
- The timing of RT generally allows for chemotherapy to be given for 1 to 3 months before RT is initiated. RT is usually given over 5 to 6 weeks (e.g., 1.8 Gy once per day), during which time chemotherapy is usually modified to avoid the radiosensitizing agents dactinomycin and doxorubicin.
The IRS-IV trial included a randomized study that reported the administration of RT twice a day, 6 to 8 hours apart, at 1.1 Gy per dose (hyperfractionated schedule), 5 days per week, was feasible but difficult to accomplish in small children who required sedation twice daily. Patients with localized, gross residual tumors were randomly assigned to receive conventional, once-daily RT (total dose of 50.4 Gy) versus the twice-daily hyperfractionated schedule (total dose of 59.4 Gy). There was no demonstrated advantage in terms of local control. Conventional RT remains the standard for treating patients who have rhabdomyosarcoma with gross residual disease.