Cumulative incidence and risk factors of brain metastasis for acral and mucosal melanoma patients with stages I-III

Purpose: Few studies focused on the incidence of brain metastasis in patients with acral and mucosal melanoma, and a better understanding of the incidences and predictors of brain metastasis is needed in these patients.

Method: A prospectively accrued cohort of 799 patients with acral and mucosal melanoma in stages I-III from July 2011 to December 2015 at Peking University Cancer Hospital were included in this study. Competing risk models (Fine and Gray) were used to estimate the cumulative incidence of brain metastasis and compare the differences in cumulative incidence curves between different primary lesions, stages, and molecular types.

Results: At a median follow-up time of 68.0 months, 60 of the 779 patients (7.7%) developed brain metastasis, and 261 (33.5%) patients developed extracranial metastasis. Considering the risk of competition, the cumulative incidence of brain metastasis at one year, two years, and five years after diagnosis were 5.1%, 10.2%, and 19.5%, respectively. Stage III, BRAF mutations, and NRAS mutations were associated with a high risk of brain metastasis in univariable analysis. Multivariate analysis showed BRAF mutations, and NRAS mutations had statistically correlated with an increased cumulative incidence of brain metastasis at diagnosis and all-time point of one year and two years after diagnosis.

Conclusion: This study is the first to report the cumulative incidence and risk factors of brain metastasis for patients with acral and mucosal melanoma in stages I-III. Patients with BRAF and NRAS mutations had a higher incidence at diagnosis and all-time point, providing the basis for surveillance guidelines and further mechanic exploration.