Radiation Therapy Is Associated with Improved Overall Survival in Non-Metastatic Merkel Cell Carcinoma: A Surveillance, Epidemiology and End Results (SEER) Analysis

Abstract

To determine factors associated with overall survival (OS) in non-metastatic Merkel cell carcinoma. Materials/Methods: 2689 patients with pathologically confirmed nonmetastatic Merkel cell carcinoma (AJCC 6 th ed. Stage I-III) who were diagnosed in 2004-2015 were identified in the SEER 18 database. Patients who survived less than 4 months from diagnosis were excluded (nZ183), as well as patients who did not receive local therapy (surgery and/or radiation therapy (RT); nZ59). 2447 patients who met inclusion and exclusion criteria were included in this analysis. Median age was 75 years (range 34-98), and median follow-up was 31 months (range 4-143). 60.2% male, 39.8% female. Surgery was performed in 92.6% of patients. There were 58.6% patients (nZ1435) received RT; 46.3% in stage I (502 of 1085), 58.2% in stage II (270 of 464), and 73.8% in stage III (663 of 898). There were 11.4% patients (nZ279) received chemotherapy; 2.6% in stage I (28 of 1085), 6.9% in stage II (32 of 464), and 24.4% in stage III (219 of 898). Overall survival (OS) from the date of diagnosis was estimated using Kaplan-Meier survival analysis. Logistic regression multivariate analysis was performed for comparisons of hazard ratio (HR) among subgroups. Results: The P value Z0.006), and stage II (5 yr OS: 60.3% vs 41.6%; pZ0.0002), but not in stage III (5 yr OS: 43.1% vs 41.9%; pZ0.17). However there was no association between chemotherapy and overall survival in stage I (5 yr OS: 45.0% vs 62.2%; pZ0.055), stage II (5 yr OS: 51.1% vs 63.5%; pZ0.23), or stage III (5 yr OS: 41.3% vs 43.0%; pZ0.71). Multivariate analysis demonstrated improved overall survival was associated with later year of diagnosis (0.75 per year, range 0.72-0.77), female sex (HR 0.52, range 0.42-0.64) and Asian race (HR 0.47, range 0.24-0.92). Worse overall survival was associated increasing stage (