Comorbidity in limited disease small-cell lung cancer: Age-adjusted Charlson comorbidity index and its association with overall survival following chemoradiotherapy.

Abstract

Combined, platinum-based thoracic chemoradiotherapy (TCR) is the current state-of-the-art treatment for patients with limited disease (LD) small-cell lung cancer (SCLC). There is only limited data available regarding the effect of comorbidities on survival following TRC. The purpose of this study is to assess the age-adjusted Charlson comorbidity index (ACCI) as a predictor of overall survival in LD-SCLC patients undergoing TCR. We retrospectively analyzed 367 SCLC patients diagnosed with LD-SCLC who received TCR between 2003 and 2017. We evaluated the ACCI (n=348) as a predictor of overall survival (OS). In this cohort, 322 patients (88%) received platinum-based TCR (either cisplatin or carboplatin), and 37 (10%) patients received vincristine based TCR. Median radiation dose was 60Gy (range 24-66Gy). Additionally, 83% of patients (n=303) received prophylactic cranial irradiation (PCI, 30Gy in 2Gy fractions). Kaplan-Meier survival analysis was performed for OS. For comparison of survival curves, Log-rank (Mantel-Cox) test was used. Univariate and multivariate Cox proportional-hazards ratios (HRs) were used to assess the influence of cofactors on OS. Patients with an ACCI>6 had a significantly shorter OS compared with patients with an ACCI≤6 (median 11 vs. 20months; p=0.005). Univariate analysis for OS revealed a statistically significant effect for ACCI>6 (HR 1.7; 95% CI 1.2-2.4; p=0.003), PCI (HR 0.5; 95% CI 0.3-0.7; p<0.001), and Karnofsky performance status≤70% (KPS) (HR 1.4; 95% CI 1.1-1.90; p=0.015). In multivariate analysis, OS was significantly associated with PCI (HR 0.6; 95% CI 0.4-0.9; p=0.022) and ACCI>6 (HR 1.5; 95% CI 1.0-2.1; p=0.049). Comorbidity is significantly associated with survival in patients with LD-SCLC undergoing TCR. The ACCI may be a valuable tool to identify patients with a shorter survival and thus might be used for risk stratification and oncological decision making.