Lung Cancer

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TU_37_3688 - Are Higher Radiation Doses Beneficial in Limited-Stage Small-Cell Lung Cancer? A Propensity Score-Matched Analysis

Tuesday, October 23
2:45 PM - 4:15 PM
Location: Innovation Hub, Exhibit Hall 3

Are Higher Radiation Doses Beneficial in Limited-Stage Small-Cell Lung Cancer? A Propensity Score-Matched Analysis
H. Chen1, E. Ali2, D. A. Palma1, G. Rodrigues1, and A. V. Louie1; 1London Health Sciences Centre, London, ON, Canada, 2Schulich School of Medicine and Dentistry, Western University, London, ON, Canada

Purpose/Objective(s): Hypofractionated thoracic radiotherapy may be advantageous in limited-stage small-cell lung cancer (LS-SCLC) due to short overall treatment times, decreased resource utilization, and patient convenience. However, there are no randomized data comparing hypofractionated radiotherapy (HFRT; defined as 40 Gy in 15 fractions or 45 Gy in 20 fractions) and high dose conventionally-fractionated radiotherapy (CFRT; defined as >= 60 Gy in 2 Gy fractions) in LS-SCLC patients. The objective of this study was to compare the survival outcomes and toxicities of these fractionation schemes using propensity score-matched retrospective data to simulate the setting of a clinical trial. We hypothesize that higher radiotherapy doses were not associated with improved survival and might have led to increased toxicity in patients with LS-SCLC.

Materials/Methods: This retrospective study examined records of patients from our institution diagnosed with LS-SCLC between January 2000 and December 2013 who were treated with HFRT or CFRT. Propensity scores were estimated by logistic regression using age, performance status, concurrent chemoradiation usage and prophylactic cranial irradiation (PCI) usage. Nearest neighbor-matching was performed on a 1:1 basis using a caliper distance of 0.1, without replacement. Overall survival (OS) and progression-free survival (PFS) endpoints were estimated by the Kaplan-Meier method and compared with log-rank tests. Cumulative incidences of esophageal and pulmonary toxicity were compared with Fisher’s exact tests. A two-sided significance level of 0.05 was used.

Results: Among 398 LS-SCLC patients reviewed, 57 patients treated with HFRT and 61 patients treated with CFRT were included in the unmatched analysis. Five-year OS was 26% for the HFRT cohort and 24% for the CFRT cohort (p = 0.82). Five-year PFS was 22% for both cohorts (p = 0.79). Significant differences in age, performance status, concurrent chemoradiation usage and PCI usage were noted in the unmatched cohorts. After propensity score-matching, the balanced cohorts each contained 37 patients. Five-year OS was 25% and 27% (p = 0.72) and 5-year PFS was 25% and 24% (p = 0.63), respectively for the HFRT and CFRT cohorts. Incidence of any esophageal toxicity was not significantly different between the cohorts (92% HFRT, 84% CFRT, p = 0.60), though there was a trend towards a higher incidence of any pulmonary toxicity in the CFRT cohort (59% vs. 38%, p = 0.06).

Conclusion: OS and PFS outcomes were similar between HFRT and CFRT in balanced cohorts. HFRT was associated with a potentially reduced incidence of pulmonary toxicity. These results suggest clinical equipoise and a prospective randomized study is needed to determine the optimal radiotherapy fractionation in patients with LS-SCLC.

Author Disclosure: H. Chen: Employee; North York General Hospital. E. Ali: None. D.A. Palma: Research Grant; Ontario Institute for Cancer Research. Patent/License Fees/Copyright; U.S. Patent Pending. G. Rodrigues: Independent Contractor; George Rodrigues Medicine Professional Corporation. Stock; George Rodrigues Medicine Professional Corporation. Royalty; Demos Medical Publishing. A.V. Louie: None.

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