A retrospective study of Merkel cell carcinoma treated at The Ohio State University (OSU) in the last 20 years

e21586 Background: Merkel cell carcinoma (MCC) is a rare but aggressive neuroendocrine cutaneous malignancy. The analysis of interventions and benefits of treatments remain limited. In this retrospective study, we analyzed the clinical features and outcomes of MCC patients treated at the OSU Comprehensive Cancer Center (OSUCCC). Methods: Electronic medical records of MCC patients who were treated from 2000 to 2021 at OSUCCC were reviewed. 179 patients were enrolled. 153 patients were analyzed for overall survival (OS) after excluding 26 patients due to loss of follow-up or insufficient data. Clinical features were collected. The first patient was treated with immunotherapy (IO) on 2/24/2015. The period after this date was defined as the IO era (87 patients). Results: Among 179 patients (median age 73, male 64.8%), 41.9% died, 13.4% were lost to follow-up and 44.7% were alive by 12/31/2022. Primary tumor locations were head (50.8%), upper & lower extremities (21.2% & 10.6%), unknown primary (6.1%), trunk (5%) and neck (4.5%). Patients with stage I, II, III and IV were 41.9%, 12.8%, 36.9% and 8.4%, respectively. Sentinel lymph node biopsy (SLNB) was performed in 73.8% of patients; tumor involvement in SNL was confirmed in 38.5% and SLNB attempts failed in 15.1%. Patients who received surgery, local radiation, IO, chemotherapy and targeted medication were 92.7%, 66.5%, 27.4%, 10.1% and 2.8%, respectively. All 75 stage I patients had wide excision, and 50.7% received local radiation. 12% of stage I patients developed tumor recurrence, with IO administered in 55.6% of those patients. Most patients with stage II (52.2%) and stage III (34.8%) received surgery followed by radiation. 20% of patients with stage IV received surgery followed by radiation and IO. The median OS was 95 months (95% CI 67-123), the 3-year survival rate was 70%, and the 5-year survival rate was 61% for the 153 assessable patients. The median OS in stage I, II, III and IV was 149, not reached, 65 and 20 months, respectively ( P< 0.05). Survival in tumors on the head/neck was similar to the upper and lower extremities (median OS 102 vs. 71 vs. 99 months, P> 0.05) but slightly superior to the trunk disease (median OS 102 vs. 15 months, P= 0.072). The outcome of never-smokers was superior to former smokers (median OS 156 vs. 71 months, P< 0.01). The median OS of stage IV patients with IO was superior to those without IO (95 vs. 10 months, P< 0.05). Among dead patients in the IO era, the median OS of patients with IO was longer than those without IO (22 vs. 6 months, P< 0.01). Conclusions: Most MCC occur in the elderly, local or regional disease, and commonly on the head with a good outcome after multidisciplinary therapies. Former smokers and stage IV disease relate to a poorer prognosis. IO shows benefits with prolonged survival, especially in metastatic disease.