Background: Platinum-based chemotherapy plus irinotecan or etoposide is the standard of care for first line (1L) treatment of small cell lung cancer (SCLC). Sensitivity to platinum-based chemotherapy has implications for regimen choice in subsequent lines of treatment. The goal of this study was to examine differences in patient characteristics, treatment patterns, and survival associated with the management of SCLC in a Medicare population by platinum sensitivity status, i.e., platinum sensitive (PS) or platinum refractory (PR). Methods: A retrospective analysis was conducted using the Surveillance, Epidemiology, and End Results (SEER)–Medicare linked data. Patients were included if they had a record with a diagnosis of SCLC in the database from 1/1/2007 – 12/31/2017 and were ≥65 years of age at diagnosis. Patients also had continuous enrollment for ≥180 days pre-SCLC diagnosis and platinum-based 1L treatment. Patient characteristics, treatment patterns, and outcomes were stratified by PS status, which was defined as initiating 2L therapy more than 6 months after the last administration of platinum-based chemotherapy in 1L. Median overall survival (OS) was estimated using the Kaplan Meier method. Results: 7,208 patients met the study criteria and one in three (33.6%, N = 2,424) SCLC patients were PS. The PS population was majority female (64.4% vs 35.6% males), younger on average (aged 72.4 yrs vs 72.9 yrs), and more likely to be diagnosed at stage I-III than the PR patient population (50.6% vs 21.1%). Among PS patients, mean time from diagnosis to 1L treatment was 6.1 weeks versus 5.7 weeks among PR patients. Only 29.7% of PS patients initiating 1L went on to second line (2L) versus 40.4% of PR patients. 68.6% of PR patients received monotherapy in 2L, with topotecan (31.7%), paclitaxel (12.1%), and irinotecan (9.9%) being the most common monotherapy regimens. 51.7% of PS patients were retreated with platinum-based chemotherapy in 2L. Median OS from initiation of 1L was 20.2 months (95%CI: 19.3-21.1 months) among PS patients versus 6.4 months (95%CI: 6.2-6.6 months) among PR patients. 5-year survival was 20.0% among PS patients and 1.5% among PR patients. Conclusions: Approximately two-thirds of SCLC patients are refractory to platinum-based chemotherapy. These patients have fewer treatment options and shorter OS than PS patients, underscoring the ongoing need for effective therapies for SCLC.