The role of neutrons in the treatment of soft tissue sarcomas.

Two-hundred twenty-one patients with soft tissue sarcoma were treated from 1978 to 1983. Treatment was nonrandomized and consisted of neutron irradiation in 94 cases with gross tumor. Treatment was nonrandomized and consisted of neutron boost irradiation after photon-irradiation or electron-irradiation in 127 cases with no gross tumor after surgery. Patient distribution according to UICC (1978) criteria was 15, 100, and 106 of T1, T2, and T3 respectively. Distribution by pathologic grade was 54, 107, and 60 for Grade 1, Grade 2, and Grade 3 tumors. Distribution by tumor residuum after surgery was 23 cases without microscopic disease (R0), 104 with microscopic disease (R1), and 94 with gross residuum (R2) or nonoperative disease. Five-year follow-up reveals a significant difference (P = 0.024) in disease-free survival (DFS) for T1 (60%), T2 (71%), and T3 (29%, P = 0.016) tumors. Similarly, there are significant DFS differences among G 1 (74%), G 2 (48%, P = 0.035), and G 3 lesions (22%, P = 0.024). The impact of tumor bulk or residuum on DFS after operation is significant when comparing R0 (87%) and R1 (65%) disease (P = 0.042). The 5-year survival of patients who had gross residuum (R2) after surgery was significantly worse (26%, P = 0.003). Ninety percent of patients failed treatment locally and distally within 2 years. The late morbidity rate was 27% for neutron and 7% for neutron-boost irradiation. In our series and reported photon data, local control rates for tumors 5 to 10 cm with neutrons were 76% and 53%, respectively. Low energy (d(14) + Be) neutrons are considered beneficial in the postoperative treatment of well-differentiated soft tissue sarcomas where gross tumor remains. Neutron-boost irradiation is of potential benefit in the treatment after operation of T2-3, and G 1-2 tumors if there is microscopic residual tumor.