Association of multiple primary melanomas with malignancy risk: A population-based analysis of entries from the Surveillance, Epidemiology, and End Results program database during 1973-2014.

Background: Genetic and environmental risk factors have been associated with the development of multiple primary melanomas (MPMs). We hypothesized that individuals with MPMs might have an increased incidence of internal malignancies.

Objective: To identify the risk for subsequent malignancies in MPM patients.

Methods: Multiple primary standardized incidence ratios were analyzed for individuals with ≥1, ≥2 and ≥3 primary melanomas (PMs) recorded in the Surveillance, Epidemiology, and End Results database during 1973-2014.

Results: We identified 223,799 individuals with ≥1 PM, 19,709 with ≥2 PMs, and 3,995 with ≥3 PMs. Risks of subsequent internal malignancy increased with number of PMs, with observed:expected ratios of 0.99, 1.14, and 1.23 (P < .05) for patients with ≥1 PM, ≥2 PMs, and ≥3 PMs, respectively. Internal malignancy was higher in younger MPM patients and those with superficial spreading melanoma. The most common malignancies among MPM patients included breast, prostate, thyroid, soft tissue, brain, kidney, non-Hodgkin lymphoma, and chronic lymphocytic leukemia. Risk for subsequent cutaneous melanoma increased with observed:expected ratios of 8.09, 22.52, 41.03 (P < .05) for patients with ≥1 PM, ≥2 PMs, and ≥3 PMs, respectively.

Limitations: Surveillance, Epidemiology, and End Results records limited information about pigmentation phenotypes, histology, and treatments.

Conclusion: Patients with MPMs have an increased risk for subsequent internal and cutaneous malignancies and might benefit from tight adherence to age-specific cancer screening.