Relationship of causative factors in spontaneous regression of cancer to immunologic factors possibly effective in cancer.

In a book written by Everson and Cole (1966) on spontaneous regression 176 examples of the phenomenon were encountered in the medical literature from 1900 to 1964, supplemented by cases referred by friends. No common denominator of explanations were found. Various types of trauma (e.g., biopsy, incomplete excision), transfusions, infection, hormone changes, drugs, etc. were encountered as possible causative factors. Most significant of all factors was encountered in the 13 examples of spontaneous regression of the bladder; in this series regression of the tumor occurred in 10 after transplantation of the ureters out of the bladder. A consideration and discussion of various reactions in human beings associated with therapeutic regressions have been reviewed hoping to develop a correlation between the two types of regression. At the time of publication of our monograph 9 years ago we were unable to suggest any mechanisms which might explain the regressions. However, since that time so many advances have been made in immunology that it appears now that a stimulation of the immune process might explain most of the regressions. We are just beginning to learn a few methods of stimulating the immune process. Use of BCG is one of the best examples of this stimulating process; other bacterial agents, or fractions, are known to have this action. No doubt there are innumerable others unknown, some of which might explain spontaneous regressions. It would appear that hormonal changes might be responsible for many of the regressions but this author doubts it explains many. More is known at the present time about cellular immunity than humoral immunity, but greater possibilities surely lie in humoral immunity. The blocking and unblocking activities developed by the Hellströms and associates are no doubt important. Immunoglobulins exert a very important role in the immune process; antibodies may consist of immunoglobulins but much more needs to be known before this relationship can be understood. The recent report (Amery, 1975) that levamisole (given at the time of resection of the lung for carcinoma) improves patient survival is exciting. Amery believes the drug may prevent the hematogenous spread of the tumor during surgery and/or may decrease the immunosuppression caused by a major operation.