Combination effects of radiotherapy and Bestatin on C3H/He mouse N-Fibrosarcoma

The effects of Bestatin, a kind of biological response modifiers (BRM), and local irradiation were studied experimentally using N-Fibrosarcoma transplanted in the hind legs of C3H/He femal mice. They were evaluated by tumor growth delay time and control of lung metastasis. Remarkable tumor growth delay was revealed in the group treated with 20 Gy of 60Co-γ-rays and a single administration of Bestatin (0.05 mg/g. b. w.) intraperitoneally at 30 minutes before irradiation compared with irradiation alone. TGT50/x3 value was 14.50 (SD: 0.64) in the former case, and 11.48 (SD: 1.26) in the latter case. TGT50/x3 value is defined as the time required for 50% of the tumors to grow into the 3 times as large value as its initial volume. It was calculated by logit analysis method. While, in the groups medicated Bestatin not only before irradiation but also daily for the next five consecutive days, tumor growth was remarkably delayed in the range 10∼25 Gy compared with irradiation alone. Dose modifying factor was 1.23∼1.29 from correlation between radiation doses and TGT50/x3 values. These results suggested that the combination of radiotherapy and Bestatin may be useful in the cancer therapy. The lungs of mice were extirpated on day 30, and Bestatin could not suppress the lung metastasis. (author)