J. G. Ninia1, N. Verma1, J. H. Laird Jr1, T. J. Hayman1, C. A. Knowlton1, G. W. Peters1, A. M. Campbell1, N. Housri1, K. Feghali2, D. de Jong2, and H. S. M. Park1; 1Department of Therapeutic Radiology, Yale School of Medicine, New Haven, CT, 2RefleXion Medical, Inc., Hayward, CA
Purpose/Objective(s): While our previous work suggested that patients with oligometastatic extensive-stage small cell lung cancer (ES-SCLC) may have improved outcomes compared to those with polymetastatic ES-SCLC, it is unknown whether complete consolidative (CC) radiotherapy to all sites of disease involvement is independently associated with improved outcomes compared to incomplete consolidation (IC). Materials/
Methods: We identified patients treated with consolidative thoracic radiotherapy following platinum-doublet chemotherapy-based treatment for ES-SCLC from 2013-2020 at a single institution. Patients undergoing CC had radiotherapy to all residual sites of active malignancy following first-line systemic therapy. All others underwent IC. Oligometastatic disease was defined at the time of diagnosis as =3 organs with distant disease, and with each organ having =3 metastatic lesions. All others were polymetastatic. The Kaplan-Meier estimator, log-rank test, and stratified Cox proportional hazards regression were used to compare progression-free survival (PFS) and overall survival (OS) between patients undergoing CC vs. IC. Results: Among 70 included patients, 28 (40%) underwent CC and 42 (60%) underwent IC. Additionally, 36 (51%) were defined as oligometastatic, among whom 24 underwent CC. 13 (19%) patients received chemo-immunotherapy, among whom 5 underwent CC. Patients with oligometastatic disease were statistically significantly more likely to undergo CC than those with polymetastatic disease (odds ratio 14.3, 95% confidence interval [CI] 3.8-69.0, p<0.001). Median follow-up time was 38.2 months. Patients undergoing CC had higher PFS (hazard ratio [HR] 0.49, 95% CI 0.29-0.81, p=0.005, 1-year 39.3% vs. 7.4%, 2-year 10.7% vs. 2.5%) and OS (HR 0.49, 95% CI 0.28-0.86, p=0.012, 1-year 89.3% vs. 52.5%, 2-year 48.4% vs. 19.7%) than those undergoing IC. When stratified by disease burden, patients with oligometastatic disease receiving CC had higher PFS (HR 0.29, 95% CI 0.12-0.69, p=0.005, 1-year 41.7% vs. 0.0%, 2-year 12.5% vs. 0.0%) but not OS (HR 0.81, 95% CI 0.34-1.98, p=0.65, 1-year 91.7% vs. 75.0%, 2-year 53.2% vs. 32.8%) compared to those receiving IC. Conclusion: ES-SCLC patients treated with CC had superior PFS and OS when compared to patients who underwent IC. Superior PFS but not OS persisted when limiting the cohort to oligometastatic patients. Given the need to prospectively examine the value of CC and IC radiotherapy following chemo-immunotherapy, we encourage continued enrollment on the NRG LU007/RAPTOR randomized trial and consideration of stratification based on disease burden or completeness of consolidation in future trials.
