Enhancing effect of thoracotomy on tumor growth in rats with special reference to the duration and timing of the operation.

To investigate the influence of operative stress on tumor growth, laparotomy and/or thoracotomy were performed in association with intraperitoneal and intravenous inoculation of Sato lung cancer cells into Donryu rats. Survival time and the number of metastatic nodules on both lungs were examined. Five-hour laparotomy and/or one-hour thoracotomy were performed on day 2 after inoculation. The enhancing effects on tumor growth of a five-hour laparotomy and of a one-hour thoracotomy were similar as regards survival time, the rate of 50-day survivors and the number of metastatic nodules on the lungs. Thoracotomy seems to enhance tumor growth several times more effectively than laparotomy. The addition of a bleeding procedure (4 ml) to these operations had little effect on the tumor growth. As for the operation timing, it was found that the operative stress of thoracotomy or laparo-thoracotomy enhanced tumor growth most markedly when the operation was performed on day -1. The enhancing effects were almost the same, and the difference from the control was still highly significant, when the operation was performed on days -2, 0 or +2.