Complete consolidative radiotherapy improves progression-free survival (PFS) and overall survival (OS) among patients with extensive-stage small cell lung cancer (ES-SCLC), according to research presented at the 2024 American Society of Radiation Oncology (ASTRO) Annual Meeting. The retrospective study compared outcomes with complete versus incomplete consolidative radiotherapy in ES-SCLC patients, revealing the potential benefits of targeting all residual disease sites outside the thorax. These findings highlight the importance of disease burden and the extent of local therapy in driving outcome differences.
Efficacy of Complete vs. Incomplete Consolidative Radiotherapy
The study retrospectively analyzed 70 patients treated at Yale School of Medicine from 2013 to 2020. Among these, 28 received complete consolidation, while 42 received incomplete consolidation. Of the 70 patients, 36 had oligometastatic disease, and 24 of these underwent complete consolidation therapy. The results indicated that patients receiving complete consolidation therapy had better PFS and OS. The 1-year OS rate was 89.3% in patients who received complete consolidation versus 52.5% in those who received incomplete consolidation (p=0.012). At 2 years, the OS rates were 48.4% and 19.7%, respectively.
Impact on Oligometastatic Disease
When the analysis was limited to patients with oligometastatic disease, a statistically significant PFS benefit was observed with complete consolidation (41.7% vs. 0% at 1 year, p=0.005). However, these patients did not show a statistically significant OS benefit compared to those receiving incomplete consolidation. This suggests that while targeting all sites of disease improves progression-free survival, it may not always translate to improved overall survival in patients with limited metastatic burden.
Ongoing Research and Future Directions
An ongoing clinical trial, RAPTOR (NRG-LU007), is prospectively evaluating whether patients who receive complete consolidation have better OS or PFS than those who get incomplete consolidation. This phase 2/3 trial is crucial for validating the retrospective findings and understanding the impact of consolidated radiotherapy in the era of immunotherapy. The primary purpose of this trial is to see whether the benefits of consolidated thoracic radiation that were observed in the CREST trial still apply in this era now where many patients with SCLC are getting immunotherapy with atezolizumab.
Considerations for Patient Subgroups
While the study did not identify specific patient subgroups that particularly benefit from complete consolidative radiotherapy, multivariate analysis indicated that patients with brain metastases or pleural involvement at diagnosis had worse outcomes after receiving complete consolidation radiation. These findings suggest that disease characteristics may influence the effectiveness of complete consolidation, and further research is needed to identify optimal treatment strategies for different patient subgroups.
Implications for Clinical Trial Design
James Ninia, MD, a third-year resident of radiation oncology at the Yale School of Medicine, emphasized the importance of considering disease burden in future clinical trials involving SCLC. "For future clinical trials involving SCLC...[researchers] should consider stratifying their analysis based on overall disease burden or completeness of consolidated radiotherapy to help us better elucidate which of these [factors] is driving these observed differences in patient outcomes that we’re seeing," Ninia stated.
