Chemosensitivity of human melanoma xenografts in immunocompetent mice and its histological evaluation.

In the subrenal capsule assay, the immuno-competent mice used have a host immune response to the graft which may introduce a bias in the determination of tumour size. A study was therefore conducted to verify the quality of the correlation that could exist between "macroscopical" and "microscopical" evaluation. A histological study of 12 different tumours treated with cis-Pt, L-PAM, DTIC, vindesine, BCNU or TGU demonstrated that a cellular host immune response was observed in 11 out of the 12 control groups and was uneven in the treated groups. The "microscopical" and "macroscopical" evaluations of tumour-take were 100 and 95% respectively. Although there was a fair correlation between the "microscopic" and "macroscopic" parameters, tumour variations in absence of host reaction--which reflect pure chemosensitivity of the treated tissue--could be measured in 50% of the cases. It was possible to determine a base-line for rejection of the test results when the control group showed a decrease in mean tumour size exceeding 20% of its initial size on day 0. If the decrease is less than 20%, then the histological evaluation appears to be of considerable additional value.