Regression in Melanoma

New Orleans—According to an analysis of the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) program from 1973 through 2006, patients with regressing melanoma had a higher survival rate than those with nonregressing melanoma. The findings were consistent when controlling for all prognostic factors. However, the authors indicated there were likely many more cases of regressing melanoma than were included in the SEER program. The results were presented during an oral abstract session at the AAD meeting titled Spontaneous Regression in Melanomas and in a poster titled Characterizing Regression in Melanomas: A Population-Based Study. The study’s authors were Kathryn J. Martires, BA, and Jill Barnholtz-Sloan, PhD, from Case Western Reserve University School of Medicine in Cleveland, Ohio, and Jeremy S. Bordeaux, MD, MPH, from the University Hospitals Case Medical Center in Cleveland, Ohio. The authors defined regression as partial or complete resolution of a tumor without treatment or therapy that changes the course of malignancy. Signs of regression include loss of intraepidermal melanocytes, effacement of rete ridges, neovascularization, wispy fibrosis, and a dense infiltrate of lymphocytes and melanophages. The authors indicated that wound-healing mechanisms could be responsible for partial regression after biopsy in nonmelanoma skin cancers, although the mechanism is unclear. They also said there have been conflicting reports in studies related to the prognosis for regressed tumors. This study focused on the epidemiology of regressed melanomas. Using the SEER program, the authors identified primary, malignant, histologically confirmed melanomas and compared the cases with malignant melanoma of the skin. They excluded cases that were identified by autopsy or death certificate. Because of a large sample size, the authors used parametric measures, including chi-square and Wilcoxon tests for categorical variables and a t-test for continuous variables when analyzing comparisons. To evaluate survival, they used the Kaplan-Meier method and Cox proportional hazards models. The study included 32,051 cases of malignant melanoma and 375 cases of regressing melanoma. Patients with regressing melanoma differed from the malignant melanoma group in terms of an older age of diagnosis (P<.0001), higher percentage of males (P<.0001), primary presentation on extremities versus trunk (P<.0001), lower mean Breslow’s depth (P<.0001), and a lower percentage of patients with ulceration (P=.0436). Based on the Kaplan-Meier method, the odds of survival in cases of regressing melanomas were 37.2% higher than the odds of survival in patients with malignant melanomas (P=.0007). The authors indicated that they did not know why regressing tumors led to higher survival rates, although they hypothesized that regression leads to a strengthened immune response.