Gender and other survival predictors in patients with metastatic melanoma on Southwest Oncology Group trials

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Abstract
Some studies have suggested that women with metastatic malignant melanoma have a better survival rate than men. However, little is known about the effect of gender on survival in combination with other clinical variables and treatment variables. Thus, an analysis of 813 eligible patients from 15 consecutive Southwest Oncology Group (SWOG) Phase II or III trials evaluating chemotherapy or chemoimmunotherapy for metastatic melanoma was performed. A multivariate Cox regression model was used. Poor performance status (P < 0.001), more organ sites with metastases (OSM) (P < 0.001), liver involvement (P < 0.001), and nonliver visceral involvement (P = 0.01) were highly significant predictors of worse survival, whereas the disease free interval (P = 0.08) had borderline significance. After adjustment for all factors, there was no difference in overall survival between men and women (P = 0.19). Women had a longer disease free interval (P = 0.003) and fewer OSM (P = 0.004) at study registration than men. The current study found that performance status, OSM, and type of visceral involvement were independent predictors of survival in patients with metastic malignant melanoma and should be used as stratification factors in future Phase III trials. However, the current study also found that gender did not appear to be a significant independent predictor of survival for this stage of disease. A longer disease free interval from initial diagnosis and fewer OSMs may partly explain the improved outcome reported for women in selected trials. The study concluded that further investigation of the biologic differences at early stage diagnosis should be undertaken to determine whether women truly have a different pace of disease progression and a different metastatic pattern.