[Improved local tumor control by early and risk-adjusted use of radiotherapy in primary non-resectable rhabdomyosarcomas: results of CWS 81 and 86 studies].

Since the lack of local tumor control was a major cause of therapy failure in the CWS-81 Study, the concept of the definitive local tumor control in patients with primary non-resectable RMS has been changed. In the CWS-81 Study RT was stratified according to the results of SL surgery at week 16-20 (after 2 cycles of CT), given only to patients who at this time stage had still microscopic or macroscopic tumor residuals. In the CWS-86 Study irradiation was given prior to SL surgery after one cycle of CT (7-10 weeks). The cumulative dose was stratified according to the degree of tumor volume reduction (32 Gy and 54.4 Gy) and given simultaneous to the second CT. The single dose was reduced (1.6 Gy) and given twice a day (accelerated hyperfractionation). This analysis excluded patients with parameningeal and extremity primaries since this group had special RT recommendation in both studies. 62% of patients had been irradiated in the CWS 81 Study and 70% in the CWS 86. The local tumor control improved dramatically in the CWS-86 Study in the group of patients who had been irradiated prior to SL surgery and still had macroscopic residues at the start of RT (rate of local tumor control 25% vs. 95%, p < .001). The average RT dose for this group was even lower in the CWS-86 Study (38.8 vs. 40 Gy). In the patients who were irradiated in clinical remission, no major change in local tumor control between studies was observed (CWS 81 82% vs. 75% CWS 86).(ABSTRACT TRUNCATED AT 250 WORDS)