To analyze the link between cachexia and prognosis among patients with extensive-stage small-cell lung cancer (ES-SCLC) following first-line immunotherapy, investigators assessed date on 123 such patients at a single center between June 2019 and February 2021. They also evaluated the prognostic values of several systematic inflammatory and nutritional indexes. Patients with more than 5% weight loss during the previous 6 months or more than a 2% weight loss and a BMI less than 20 kg/m2 were defined as having cachexia after the initiation of immunotherapy. Response rate, progression-free survival (PFS), and overall survival (OS) were the study endpoints, with univariate and multivariate survival analysis conducted to determine factors correlated with OS and PFS. At 6 months following initial treatment, 41.5% of patients presented with cachexia, among whom treatment response and survival were worse than those without cachexia. Among all participants, the median OS was 14.4 months and the median PFS was 8.1 months. Median PFS was significantly longer in patients without cachexia (HR, 1.802), without bone metastases (HR, 2.362), and with lower change of total protein (HR, 1.799). Patients with poor Eastern Cooperative Oncology Group performance status had significantly shorter OS (HR, 1.904), as did those with higher baseline systemic immune-inflammation index (SII) score (HR, 2.135), cachexia (HR, 2.020), advanced metastases stage (HR, 3,111), and higher post-treatment systemic inflammation response index (SIRI) score (HR, 2.135). “ES-SCLC patients who develop cachexia after first-line immunotherapy have a poor prognosis,” wrote the study authors. “Our study also confirms that baseline SII and SIRI at 6 weeks after treatment appear to be promising predictors for OS [in patients with] ES-SCLC who [were] treated with first-line immunotherapy.”