RESULTS OF IRRADIATION OF SOFT-TISSUE SAR COMAS WITH FAST-NEUTRONS

Surgery belongs to the standard treatment of soft-tissue sarcomas. By adjuvant radiotherapy with photons, local control could be improved af ter less radical resection. In incompletely resected low- and intermed iate-grade tumors, good tumor control could be achieved by irradiation with fast neutrons compared with adjuvant photon irradiation after co mplete resection. Because of minor experiences in neutron therapy of s oft-tissue sarcomas, the gathered at the University of Munster experie nces with fast neutron irradiation are presented. At the Department of Radiotherapy and Radiation Oncology of the University of Munster, 42 patients with soft-tissue sarcomas were irradiated with fast neutrons, Mainly tumors of low or intermediate malignancy were postoperatively treated (R0: 22.5%, R1: 27.5%, R2: 50%). Histologically malignant fibr ous histiocytoma, liposarcomas and neurogenic sarcomas dominated. 29 p atients were irradiated with fast neutrons alone and 13 patients were treated with mixed beam therapy (photons and neutrons). The average fo llow-up period was 20 months, during this period twelve patients died. Overall five-year survival probability analyzed by the Kaplan-Meier m ethod was 53 %. The actuarial five-year survival rate for G1-tumors wa s 71 %. for G2-tumors 68 %. Three out of four patients with G3-tumor d ied within the first year after irradiation. Patients with R2-resectio n had a five-year survival probability of 33 %, those with RO- resp. R 1-resection had a five-year survival probability of 73 % (p < 0.05). T umor regression was observed in 71 % of all treated tumors. Local recu rrence occurred in 4 out of 38 patients with available follow-up data. Two of these recurrences developed at the borders of the irradiation field. G2-tumors showed a higher incidence of recurrence than G1-tumor s. Probability of metastatic disease after five years was 31 %. Only 4 out of 35 patients (11,4 %) showed side effects Grade III-IV during t he neutron irradiation. These side effects included skin ulceration, b ullous skin reaction, cystitis and erosive lesions of the rectal mucos a. Efficacy of neutron radiation of highly and intermediately differen tiated soft tissue sarcomas was shown. The result of surgical resectio n seems to be the most important prognostic factor for patients with s oft tissue sarcomas.