A Demonstration of the Curability of Malignancy in Rats by a Low Pressure Environment

Previous workers who have carried out experiments on the effect of lowered oxygen tension on malignant neoplasms have reported a retarded growth and an extensive necrosis but no positive cures. They evidently missed the time when the factors which ultimately may annihilate the cancer reach their highest potency. Our success is attributable to (1) an adequate period of exposure, (2) a gradual adaptation to successive steps of decreasing oxygen tension, and (3) an uninterrupted maintenance of the final pressure throughout the experiment. We are not prepared to emphasize the superiority of our method, the reduction of the total pressure, as compared with the adjustment of the oxygen tension at normal atmospheric pressure. We believe, however, that it is technically more convenient and that it affords a greater margin of safety. Our low pressure chambers are improved models of the apparatus described previously by one of us. The pressure is controlled automatically and is disturbed neither by any manipulation in the care of the animals nor by the removal and the replacement of individual rats. A series may therefore be continued for almost an unlimited time, although the maximal exposure time in our cancer work has been 6 weeks exclusive of the one week adaptation period. Our results for the first 2 weeks have closely corresponded to those of other investigators and we shall, therefore, in this report consider mainly those series which have lasted longer. We have employed 2 pressure levels: 300 and 360 mm., corresponding in altitude to 25,000 and 20,000 feet respectively. With a few exceptions, adapted rats continue to do quite well in both of these environments and we believe that even the lower pressure level would also be endurable to patients.