Survival analysis of malignant melanoma in Japan--multivariate analysis of prognostic factors.

Background: The prognostic factors of cutaneous melanoma reported in Japan were different from those in US and Europe in evaluating the prognostic values of the biopsy types, sex, anatomic location and so on. The aim of this study was to identify the prognostic factors for survival in cutaneous melanoma in Japan by performing univariate and multivariate analyses.

Methods: We studied a total of 103 patients with cutaneous melanoma, treated in Osaka City University Hospital during the period 1991-2003. Eleven factors were evaluated by uni- and multivariate analyses. Kaplan-Meier analyses were performed to estimate and compare five-year survival rates. After checking for independence, prognostic factors were then evaluated applying a Cox proportional hazards model in localized melanoma patients and in all invasive melanoma patients.

Results: On univariate analysis, anatomic location, ulceration, tumor thickness, Clark's level, lymph node metastasis, distant metastasis and TNM staging were significantly related to five-year survival rates. Clark's level and TNM staging were excluded after checking for independence. Multivariate analysis revealed that significant prognostic factors were tumor thickness and anatomic location in localized melanoma patients, and distant metastasis, tumor thickness, sex and anatomic location in all invasive melanoma patients.

Conclusions: Thinner tumors, female gender and location on the extremity are favorable prognostic features in malignant melanoma. Tumor thickness whose best cut-off point is 4 or 5 mm is the most important prognostic factor in predicting survival in the melanoma patient. These results were similar to those in U.S. and Europe.