Main Session
Sep
29
PQA 07 - Head and Neck Cancer, Lung Cancer/Thoracic Malignancies, and Nursing and Supportive Care
3604 - Radiation-Elicited Structural and Post-Treatment Observations Necessitating Sophisticated Evaluation after RadioTherapy (RESPONSE-RT) in Stage III NSCLC Treated with Chemoradiotherapy and Consolidation Immunotherapy
Presenter(s)
Clifford Robinson, MD, FASTRO - Washington University in St. Louis, St. Louis, MO
C. G. Robinson1, M. M. Farhangi2, R. R. Gill3, T. Stromp2, M. Zhou4, S. Raza2, B. Laxmanan2, I. Kalsekar2, T. Hao2, and K. Devisetty2; 1WashU Medicine, Department of Radiation Oncology, St. Louis, MO, 2Interventional Oncology, Johnson & Johnson, New Brunswick, NJ, 3Columbia University Irving Medical Center, New York, NY, 4Global Epidemiology, Johnson & Johnson, New Brunswick, NJ
Purpose/Objective(s):
Concurrent chemoradiotherapy (CCRT) followed by consolidation immunotherapy (cIT) is the standard of care for Stage III unresectable non-small cell lung cancer (NSCLC). Follow-up CT scans after radiotherapy (RT) often reveal radiation-induced pneumonitis and fibrosis. Compounded by cIT-induced immune changes, such post-RT changes could impact RECIST 1.1-based lesion measurements for objective response rate (ORR). The objectives of this study are to characterize the pattern and temporal evolution of post-RT changes and quantify their impact on lesion measurability and ORR.Materials/Methods:
Longitudinal clinical and imaging data, including RT plans, were collected from Stage III NSCLC patients treated with CCRT and cIT (with no evidence of progression or toxicity post-RT) at three European centers (2017–2022). Majority agreement from three independent US board-certified radiologists was used to classify the pattern of post-RT change (pneumonitis, fibrosis or no change) and assess the measurability of RT-treated lesions. To quantify the impact of post-RT changes on ORR, we evaluated whether patients that developed non-measurable lesions (before disease progression) had already achieved a complete or partial response (CR or PR) at any prior assessment. Conversely, patients who had stable disease (SD) at all prior assessments and subsequently became non-measurable were classified as having the potential for post-RT changes to confound the determination of their best overall response (BOR).Results:
Among 81 eligible patients across three centers, median age was 60 years (range, 37–78), and 59.3% were male. Median follow-up was 26.7 months (range, 2.4–72.9) and median time to first post-RT change was 2.6 months (range, 0.1-36.7). Within the first six months, 88% of patients exhibited post-RT changes (57% pneumonitis, 49% fibrosis), increasing to 93% by 12 months (62% pneumonitis, 84% fibrosis). The median time to at least one lesion becoming non-measurable was 10.9 months (range, 2.5-45.5). At six months, 9 patients (11.1%) had non-measurable lesions, of which 6 patients (7.4%) were prior responders, leaving 3 patients (3.7%) for which BOR was confounded. At 12 months, 22 patients (27.2%) had non-measurable lesions, of which 16 patients (19.8%) were prior responders, leaving 6 patients (7.4%) for which BOR was confounded.Conclusion:
Post-RT radiographic changes were prevalent and impacted lesion measurability in Stage III unresectable NSCLC patients treated with CCRT and cIT. However, the incidence of missed responders remains low due to the ability to assess BOR prior to onset, highlighting that post-RT changes have a low impact on ORR but underscore the need for refinements in RECIST to enable more accurate response assessment.