FOR DECADES the reported disappearance or regression of malignant tumors, without significant therapy to explain it, has intrigued the profession, and has given rise to controversy as to whether or not the phenomenon actually exists. Spontaneous regression of cancer may be defined as the partial or complete disappearance of a malignant tumor in the absence of all treatment or in the presence of therapy which is considered inadequate to exert a significant influence on the growth of neoplastic disease. Indeed, spontaneous regression is a somewhat inaccurate term for this phenomenon because any change in the growth pattern of malignant tissue must have a biological explanation.
Efforts to find an explanation of this phenomenon have been thwarted by the fact that, fortunately, only a small fraction of patients with malignant disease go untreated. Thus, spontaneous regression of cancer has been mainly reported in patients in whom the cancer was beyond the