P2.12-10 Novel Prognostic Model for Limited-Stage Small-Cell Lung Cancer

Abstract

There is currently no prognostic model designed specifically for patients with limited-stage small cell lung cancer (SCLC). The objective of this study was to construct a novel prognostic model for this patient population using baseline characteristics readily available in clinic. An institutional retrospective consecutive patient database was constructed by reviewing the charts of patients diagnosed with limited-stage SCLC between January 2000 and December 2013. Baseline patient characteristics, treatment details and outcomes were extracted. The primary endpoint for the prognostic model was overall survival (OS) and the secondary endpoint was progression-free survival (PFS). Univariable and multivariable Cox regression analyses were performed to identify variables associated with OS and PFS. Prognostic models were generated using recursive partitioning analysis (RPA). A total of 398 patients were eligible for analysis. Median follow-up was 8.2 years. The median age was 67 (range: 40-87). Overall, 94% of patients received chemotherapy, 82% received radiotherapy and 65% received both concurrently. Both hypofractionated (40 Gy in 15 fractions) and conventionally-fractionated (50-66 Gy in 25-33 fractions) radiotherapy were used. Prophylactic cranial irradiation was used in 45% of patients. The median OS for the entire cohort was 15.4 months, with a 5-year OS of 19.7%. Overall median PFS was 9.3 months, with a 5-year PFS of 14.1%. On multivariable Cox regression, age, Eastern Cooperative Oncology Group (ECOG) performance status, tumor location and baseline presence of any pleural effusion (non-malignant or unknown status) were prognostic of OS, while performance status and T-stage were prognostic of PFS. RPA model of OS divided patients into favorable (ECOG 0-2, no pleural effusion, middle/upper lobe location: 5-year OS 31%), intermediate (ECOG 0-2, no pleural effusion, non-middle/upper lobe location: 5-year OS 21%) and unfavorable (ECOG 3-4 or any pleural effusion: 5-year OS 5-8%) groups (log-rank p < 0.001). RPA for PFS divided patients into favorable (ECOG 0-2, <=T3: 5-year PFS 21%) and unfavorable (ECOG 3-4 or T4: 5-year PFS 5-9%) groups (log-rank p < 0.001). Novel prognostic factors for OS and PFS based on baseline patient characteristics were successfully identified for patients with limited-stage SCLC. RPA prognostic models were able to separate patients into distinct risk groups for OS and PFS. Our results will benefit from further external validation and can be useful in stratifying patients in future prospective studies.