Influence of high-pressure oxygen and chemotherapy on the AMel 4 hamster melanoma.

The effect of hyperbarie oxygen (HPO) on tumor growth and a possible synergism with chemotherapeutic agents (mechlorethamine, amethopterin, and cyclophosphamide) were tested with the use of the AMel 4 hamster melanoma. HPO alone prolonged survival (P < 0.001), but neither sur vival nor size of the primary tumor was modified by the addition of chemotherapy beyond that observed when these drugs were given alone. Hence the combined effects seem additive and not truly synergistic. Although weight loss was significantly greater in the HPO-treated animals, diet-restricted controls that lost more weight than the HPO groups had no increase in survival. Striking differences were evident in the gross and histologie appearance of pulmonary métastases,the extent of tumor being far less in the HPO-treated groups. The experimental results indicate that HPO delays the death of animals having this tumor and suggest that this prolongation of survival is particularly a function of restraint of pulmonary métastases.HPO did not potentiate the effect of chemotherapy by the agents tested.