Tumor doubling time of cutaneous melanoma and its metastasis

Tumor doubling time, estimated using clinical data, is one factor used to determine who will benefit from surgery for patients with pulmonary metastatic melanoma. Reported herein are the tumor doubling times of four primary cutaneous melanomas in which the diagnosis of melanoma had been delayed, and their metastases (3 of 4). The median/mean tumor doubling times for primary melanoma and metastatic melanoma was 94/144 days (range 50-377) and 33/64 days (range 8-212), respectively. By paired t test, metastatic tumor doubling time was significantly faster than primary tumor doubling time (P = 0.01). Extrapolating the growth curves of metastatic melanoma to the point of onset of metastasis revealed that dissemination of tumor cells occurred well before first clinical presentation and symptoms in two cases, and in one case, during the interval between clinical presentation and complete excision of the primary. At the opposite pole, extrapolated growth curves for slow tumor doubling time melanoma demonstrated that long-term follow up (>10 years) is required to determine whether patients have been cured of melanoma or not. Overall, these estimates of melanoma tumor doubling time validate the concept of tumor progression, reinforce the tenet of early detection and curative excision, and can explain the phenomenon of late onset of metastases, respectively.