The utilization of roentgen rays in cancer therapy obviously is dependent upon their capacity to destroy the malignant growth without producing destruction of the surrounding normal tissue. However, in basal- and squamous-cell cancer of the skin, the margin of difference between what is generally regarded as "the tumor lethal dose" and that which will produce permanent destruction (necrosis) of the normal skin and subcutaneous tissues, is a somewhat narrow one. It should not be surprising, therefore, that if the normal tissue tolerance were for any reason slightly lowered, it might approach that of the tumor lethal dose. Consequently, surrounding tissue, as well as the tumor, might be destroyed.
Although these basic principles have been known for years, there appears to be a tendency to associate the phenomenon of tissue necrosis solely with excessive overdosage. The late radiation changes resulting from total dosages far in