An in situ method for estimating cell survival in a solid tumor.

The response of the murine Meth-A fibrosarcoma (a methylcholanthrene-induced tumor) to single and fractionated doses of X-irradiation, actinomycin D chemotherapy, and/or concomitant local tumor hyperthermia was assayed with the use of an in situ method for estimating cell kill within a solid tumor. The cell survival assay was based on a standard curve plotting number of inoculated viable cells (10(1) to 10(7)) with and without radiation (10 kilorads)-inactivated homologous tumor cells (heavily irradiated) versus the time required for i.m. tumors to grow to 1.0 cu cm. The time for post-treatment tumors to grow to 1.0 cu cm was cross-referenced to the standard curve, and the number of surviving cells contributing to tumor regrowth was estimated. The resulting surviving fraction curves closely resemble those obtained with in vitro systems. The advantages and limitations of this technique are discussed as a method for evaluating treatment effectiveness.