Comparison of subsequent malignancies after first diagnosis of merkel cell carcinoma between white and non-white Hispanic patients

Summary: Abstract Body: Subsequent malignancies following Merkel cell carcinoma (MCC) have been documented. However, little is known about the trends of subsequent malignancies among ethnic groups, especially in non-white Hispanic (NWH) patients. Therefore, the aim of this study is to describe the differences of subsequent malignancies following the first diagnosis of MCC in NWH patients, taking their white counterparts as control group. This retrospective cohort study included MCC cases diagnosed in white and NWH patients from 2000 through 2021 in the SEER-22 registry. Categorical variables were reported as counts and percentages. Two-tailed Chi-square was used to assess the association between categorical variables. P-values < 0.05 were considered significant. A total of 19,118 MCCs were identified, of which 0.2% (n=39) were in NWH patients. A total of 2,677 subsequent malignancies was found in the white cohort while 5 cases in NWH patients. While melanoma was the most common subsequent malignancy (n=323, 12.0%) in white patients, no subsequent cases of melanoma was registered in the NWH cohort (p>0.05). Furthermore, MCC was the second most common subsequent malignancy in white patients (n=278, 10.4%) followed by lung/bronchus cancer (n=275, 10.3%); no MCC was found as subsequent malignancy in the NWH cohort (p>0.05). The malignancies found in the NWH group included gallbladder/sigmoid colon adenocarcinoma, squamous cell carcinoma of tonsils, angiosarcoma, and breast cancer. Although statistical significance was not achieved, these results carry substantial clinical/ epidemiological relevance. Our findings may suggest that UV radiation could play a bigger role in the development of MCC in white patients than NWH patients since more UV-related malignancies occurred in the white cohort. Despite the small sample size in the NWH group, these observations highlight potential differences in the biological behavior for subsequent malignancies between ethnic groups, warranting further investigation into the role of genetic and environmental factors of MCC and associated cancers. Luis J. Borda¹, Melissa A. Pugliano-Mauro¹ 1. Dermatology, UPMC, Pittsburgh, PA, United States. Clinical Research: Epidemiology and Observational Research