Previously Untreated Childhood Rhabdomyosarcoma
Table 7. Characteristics of Low-Risk Patients with High Survival Rates Using Three-Drug Therapy with Vincristine, Dactinomycin, and Cyclophosphamide With or Without Radiation Therapy (Subset B) continued...
Standard treatment options
- In IRS-IV, intermediate-risk patients had survival rates at 3 years from 84% to 88%. This category includes patients with embryonal rhabdomyosarcoma at unfavorable sites (Stages 2 and 3) with gross residual disease (i.e., Group III), and patients with nonmetastatic alveolar rhabdomyosarcoma (Stages 2 and 3) at any site (Groups I, II, and III). The IRS-IV study randomly assigned intermediate-risk patients to receive either standard VAC therapy or one of two other chemotherapy regimens using ifosfamide as the alkylating agent. Outcomes with VAC were as good as the other two regimens and easier to administer. Because there was no difference in outcome between these three treatments, confirming VAC as the standard chemotherapy combination for children with intermediate-risk rhabdomyosarcoma.
A comparison of survival in patients with tumors of embryonal histology treated on IRS-IV (who received higher doses of alkylating agents) compared with similar patients treated on IRS-III (who received lower doses of alkylating agents) suggested a benefit with the use of higher doses of cyclophosphamide for certain groups of intermediate-risk patients. These included patients with tumors at favorable sites and positive lymph nodes, patients with gross residual disease, or patients with tumors at unfavorable sites who underwent grossly complete resections, but not patients with unresected embryonal rhabdomyosarcoma at unfavorable sites. For other groups of intermediate-risk patients, an intensification of cyclophosphamide was feasible but did not improve outcome.
- The COG has also evaluated whether the addition of topotecan and cyclophosphamide to standard VAC therapy improved outcome for children with intermediate-risk rhabdomyosarcoma. Topotecan was prioritized for evaluation on the basis of its preclinical activity in rhabdomyosarcoma xenograft models as well as its single-agent activity in previously untreated children with rhabdomyosarcoma, particularly those with alveolar rhabdomyosarcoma.[110,111] Furthermore, the combination of cyclophosphamide and topotecan demonstrated substantial activity both in patients with recurrent disease and in newly diagnosed patients with metastatic disease.[112,113] The COG-D9803 clinical trial for newly diagnosed patients with intermediate-risk disease randomly assigned patients to receive either VAC therapy or VAC therapy with additional courses of topotecan and cyclophosphamide. However, patients who received topotecan and cyclophosphamide fared no better than those treated with VAC alone; 4-year FFS was 73% with VAC and 68% with VAC/VTC (vincristine, topotecan, and cyclophosphamide).[Level of evidence: 1iiA] Thus, VAC is still the standard form of multiagent chemotherapy for intermediate-risk patients.
- In a limited-institution pilot study, a combination of vincristine/doxorubicin/cyclophosphamide (VDC) alternating with ifosfamide/etoposide (IE) was used to treat patients with intermediate-risk rhabdomyosarcoma. The relative efficacy of this approach versus the standard approach would require further investigation.[Level of evidence: 3iiiA]
- Approximately 20% of Group III patients will have a residual mass at the completion of therapy. The presence of a residual mass had no adverse prognostic significance.[115,116] Aggressive alternative therapy may not be warranted for rhabdomyosarcoma patients with a residual mass at the end of planned therapy. For Group III patients, best response to initial chemotherapy had no impact on overall outcome. While induction chemotherapy is commonly administered for 9 to 12 weeks, 2.2% of patients with intermediate-risk rhabdomyosarcoma on the IRS-IV and COG-D9803 studies were found to have early disease progression and did not receive their planned course of RT. COG investigators are now studying the value of early administration of RT in patients of intermediate risk.
- In a European trial (SIOP-MMT-95) of 457 patients with incompletely resected embryonal rhabdomyosarcoma, alveolar rhabdomyosarcoma, undifferentiated sarcoma, or soft tissue primitive neuroectodermal tumor, the addition of carboplatin, epirubicin, and etoposide to standard ifosfamide, vincristine, and dactinomycin (IVA) therapy did not improve outcome (3-year OS for IVA was 82%; 3-year OS for IVA plus carboplatin, epirubicin, and etoposide was 80%).