Cell proliferation patterns in human malignant melanoma, in vivo.

Cell kinetics were studied, in vivo, in 19 patients with metastatic melanoma by autoradiographic technics. Multiple tumor labeling indices (L.I.) were determined with intralesional H3-TdR in 19 patients and were correlated with the presence of melanin. Serial biopsies were obtained to derive percent labeled mitoses (PLM) curves for 9 individual patients. Duration of the S and G2 phases were calculated using 50 and 37% intercepts from the PLM curves, as well as by two computerized cell-cycle analysis programs, and the results were compared. Tumor L.I.s were found to be reproducible for distant metastases of similar size in the same patient. Tumor L.I.s had a bimodal distribution for the 19 patients examined. The two significantly distinct subgroups had L.I.s of 18.2 +/- 3.4% and 6.7 +/- 2.1%. The presence of melanin correlated with the higher L.I. subgroup. The difference in L.I. may reflect a higher growth fraction or a shorter germinative cycle in melanotic tumors. However, the presence of melanin did not correlate with a change in the duration of S or G2 phases. The sum of Ts and Tg2 was approximately 24 hours, regardless of the analytic method. These kinetic parameters are being monitored during chemotherapy for prognostic indicators.