Cachexia is a syndrome in patients with cancer that reduces life quality and prognosis, characterized by severe weight loss, muscle atrophy, and anorexia. How cachexia adversely affects older patients with small cell lung cancer (SCLC) remains uncertain.

This study aimed to determine the effect of cachexia on prognosis, treatment delivery, and efficacy in older patients with advanced SCLC receiving first-line platinum-based chemotherapy. We retrospectively analyzed older patients (≥ 70 years) with advanced SCLC treated with carboplatin and etoposide between January 2015 and June 2020 at the Shizuoka Cancer Center.

Cachexia was diagnosed based on the % weight loss and body mass index. After excluding patients with no documented weight change and those who relapsed after radiotherapy, we examined the effect of cachexia on treatment delivery, progression-free survival (PFS), and overall survival (OS).

Cachexia was identified in 57% (28 of 49) of patients. The cachexia group experienced more frequent treatment interruptions and dose reductions than the non-cachexia group (46% vs. 10% for dose reductions, p < 0.05; 61% vs. 90% for completion of four chemotherapy courses, p < 0.05).

Median PFS and OS were significantly shorter in the cachexia group compared to those in the non-cachexia group (PFS: 3.3 vs. 5.4 months; OS: 6.3 vs. 15.1 months). Older patients with advanced SCLC and cachexia undergoing carboplatin and etoposide therapy exhibited shorter PFS and OS than those without cachexia.

Treatment delivery was less effective in the cachexia group than in the non-cachexia group, suggesting that their vulnerabilities affected treatment efficacy.