Risk factors of fast growing melanomas in a French prospective cohort.

Abstract

e21042 Background: Rate of growth (ROG) of the primary tumor is a known prognostic factor in melanoma (MM). Fast growing melanomas (FGMM) could account for an important part of the thick tumors which still exist despite earlier and earlier detection. Methods: All patients referred for a primary mm to two French Dermatology Department from the period 2012-2016 were prospectively enrolled in an observational case control study. ROG was calculated as the ratio of Breslow thickness to time to mm development according to patient, following a well-established process. FGMM were defined as those with a ROG > 0.5 mm/month and MMs with a ROG ≤05mm/month were used as controls. Differences in epidemiological, clinical and pathological features were evaluated with univariate and multivariate analysis. Results: 464 patients were enrolled. 149 mm (32.1%) were FGMM. Factors associated with FGMM in univariate analysis were age > 70 years (p = 0.006), tumor location (p = 0.032), histological subtype (p = 0.021), median thickness (p < 0.001), ulceration (p < 0.001), high mitotic rate ( > 1/mm2 )(p = 0.002), sentinel node involvement (p = 0.008), hair color at the age of 20 (p = 0.011), lower NSAIDS consumption (p = 0.012) and lower number of sunburns (p = 0.002). Age > 70 years (OR 1.88 95%CI 1.19-2.98, p = 0.007), ulceration (OR 3.70 95%CI 2.05-6.61) p < 0.001), sentinel node involvement (OR 1.93 95%CI 1.01-3.69 p = 0.046), regression (OR 0.37 95%CI 0.15-0.94) p = 0.037) and NSAIDS exposure (OR 0.29 95%CI 0.11-0.78, p = 0.014) remained associated with FGMM in multivariate analysis. OS and PFS were significantly lower in the FGMM group (HR 1.98 (95%CI 1.11-3.54, p = 0.02) and HR 1.79 (95%CI 1.17-2.73, p = 0.007), respectively). Conclusions: Fast growth characterizes a subset of primary mm which are intrinsically more aggressive and have different risk factors than other MM, namely more frequent in the elderly and with no association with skin type, nevus count or sun exposure. Association with ulceration could reflect a specific immune context. Negative association with NSAIDS exposure warrants more investigation, since it may have therapeutic implications.