Predictors of Late deaths among patients with clinical stage I melanoma who have not had bony or visceral metastases within the first 5 years after diagnosis

We studied fourteen prognostic factors in 340 patients with clinical stage I malignant melanoma who were free of bony or visceral metastases 60 months following diagnosis. The malignant melanoma survival rate (MMSR) was 95% for these patients during the ensuing 40 months (i.e., 100 months following diagnosis). Deaths from malignant melanoma occurred exclusively in the subset of patients with primary lesions 1.70 mm through 3.64 mm thick. The seventy-four patients in this thickness group who were free of bony or visceral metastases at 60 months had a 100-month MMSR of 73%. Patients in the other thickness groups, including nineteen patients with melanomas ≥23.65 mm thick, had a 100-month MMSR of 100% (if bony or visceral metastases had not occurred in the first 60 months following diagnosis). Within the 1.70 through 3.64 rnm thickness group, a Cox multivariate analysis found no other significant prognostic factors among the remaining thirteen variables. As a result of the continuing deaths after 60 months in the 1.70 through 3.64 rnrn thickness group, these patients had a cumulative 100-month MMSR (i.e., 1 through 60 months plus 61 through 100 months) that was only 17% higher than that for the thicker (≥3.65 mm) group. These data, when combined with published 1- through 60-month results, indicate that most melanomas do not become lethal until a critical volume is reached (indicated by a thickness of ≥1.70 mm), Inasmuch as primary melanomas continue to grow and increase in size after they attain this critical volume, the thickness measurement parallels the metastatic tumor burden. In other words, thickness is an index not only of the lethal potential but also of the survival interval (or rate of death) after surgical removal of the tumor.