Multiple studies suggest that overall survival (OS) and Merkel cell carcinoma (MCC)-specific 31 survival are worse in the immunosuppressed MCC population, but few have investigated survival 32 stratified by type of immunosuppression. 1–3 These data are important because identifying the most-at risk 33 populations could support more aggressive workup, follow-up, or surveillance strategies. Thus, we 34 conducted a study in the National Cancer Database (NCDB) to investigate MCC in patients with 35 immunosuppression by solid organ transplant (SOT), hematologic malignancy, or other cause. A 36 complete set of methods are included in a supplement (Mendeley Supplemental Material at 37 https://dx. doi. org/10.17632/ddm5bx9npc. 1). 38

Our cohort consisted of 4683 immunocompetent MCC patients, 158 with SOT, and 420 39 immunosuppressed due to other conditions (159 chronic lymphocytic leukemia [CLL], 90 non-Hodgkin 40 lymphoma [NHL], 26 HIV, 5 with more than 1 immunosuppressing condition, and 140 with other 41 causes). SOT patients had a lower proportion of AJCC stage I/II disease upon initial diagnosis and higher 42 distribution of AJCC stage III disease compared to immunocompetent patients (Mendeley Supplementary 43 Table 1). 44