Clinical significance of the cachexia index in patients with small cell lung cancer

BACKGROUND: Cancer cachexia worsens the treatment outcomes of patients with small-cell lung cancer (SCLC). However, no reliable biomarker of cancer cachexia is yet known. METHODS: We retrospectively evaluated male SCLC patients who received induction chemotherapy or concurrent chemoradiotherapy. The cachexia index (CXI) was calculated as skeletal muscle index × serum albumin level (g/dL)/neutrophil-to-lymphocyte ratio. The CXI cutoff according to tumor stage was determined based on a time-dependent receiver operating characteristic curve, and all patients were divided into low- and high-CXI groups. RESULTS: Of 267 patients, 83 and 24 patients with limited-stage disease (LD) and 123 and 37 patients with extensive-stage disease (ED) were assigned to the high- and low-CXI groups, respectively. Only one of 24 patients (4.2%) with LD in the low-CXI group achieved a complete response (CR), whereas 30 of 83 patients (36.1%) with LD in the high-CXI group achieved CRs (p = 0.004). More low-CXI patients required early discontinuation of treatment because of treatment-related toxicity compared to the high-CXI patients (37.5% vs. 16.9%, respectively, p = 0.030, for LD patients; 27.0% vs. 11.4%, respectively, p = 0.019, for ED patients). The median progression-free survival (PFS) and overall survival (OS) were significantly shorter in the low-CXI group than the high-CXI group (6.3 vs. 11.1 months and 7.5 vs. 20.6 months, respectively, both p < 0.001 for LD patients; 2.9 vs. 6.3 months and 5.8 vs. 12.8 months, respectively, both p < 0.001, for ED patients). On multivariate analysis, low-CXI status was an independent poor prognostic factor for both PFS and OS regardless of the tumor stage. CONCLUSION: A low CXI was associated with treatment intolerance, poor treatment response rate, and poor prognosis in SCLC. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12885-021-08300-x.