Restraint and promotion of tumor growth

Abstract

At a previous meeting of this society, we reported upon the promoting influence of heated tumor emulsion upon tumor growth in rats. 1 This evening we wish to report briefly the results obtained upon the re-inoculation of rats having tumors or having recovered spontaneously from them as affected by the injection of the heated emulsion of tumor cells and other substances.

The rats were grouped into several series as follows:

(a) Rats with tumors undergoing spontaneous absorption.

(b) Rats from which tumors after a degree of growth had disappeared spontaneously.

(c) Rats which failed to develop tumors on primary inoculation.

At the time these experiments were carried on, the sarcoma was at maximum virulence and gave approximately one hundred per cent. of successful implantations. Of these a certain number later underwent retrogression, as always happens with this tumor. Before the effects of tumor and other emulsions are described, it is desirable to give the results of a control series of observations.

Into 249 rats already having one tumor were implanted second tumor fragments; 59 per cent. of these rats developed a second growing tumor, It was subsequently found that at the time of the second implantations some of the tumors were already undergoing retrogression, and as the rats which have recovered spontaneously are more refractory than rats with growing tumors, this percentage of successful secondary transplantations should properly be stated still higher.

Into each of 70 rats which had recovered spontaneously from growing tumors, a second implantation of tumor particles was made; 17 per cent. of these were successful.

Into 201 rats which had been inoculated once unsuccessfully with the tumor while its virulence was below the maximum, second implantations of the virulent tumor were made; 49 per cent. were successful.

With this series is to be compared the next to be given.