Adaptive Lung Radiotherapy in the Era of Immunotherapy: A Single Center Retrospective Review

Abstract

<h3>Purpose/Objective(s)</h3> Treatment with concurrent chemoradiation and immune checkpoint inhibition (ICI) in patients (pts) with locally advanced or stage III/IV non-small lung cancer (NSCLC) is associated with improved PFS and OS. However, treatment is limited by the development of pneumonitis and esophagitis, toxicities associated with both chemoradiation and ICIs. <h3>Materials/Methods</h3> We conducted a single center retrospective review of pts with locally advanced or stage III/IV NSCLC who received chemoradiation with concurrent or subsequent ICI. Pts were excluded if the relevant structure contours were missing or if the tumor location was not matched by both groups. Pneumonitis and esophagitis were assessed with CTACE V5. <h3>Results</h3> From 2015-2020, 49 pts were identified and 25 were included in the analysis. One patient was excluded due absent contours. Ten pts were adapted and 15 were non-adaptive controls. Mean age at onset was 728 years, 12F, 13 M; 13 adenocarcinoma, 9 squamous, 3 poorly differentiated; mean BMI 28.3 6.1, 1 IIB, 9 IIIA, 15 IIIB; 4 T1, 6 T2, 9 T3, 6 T4; 1 LLL, 8 LUL, 4 RLL, 12 RUL. Twenty and 77.7% of pts in the adaptive group had pneumonitis and esophagitis respectively, while 20% and 80% in the non-adapted group had pneumonitis and esophagitis respectively. Due to the number of DVH parameters sampled, bivariate analysis was performed; values with <i>P</i> < 0.05 were included for multiple regression analysis. Wilcoxon Rank Sum test was performed for the GTV of adapted and non-adaptive pts with <i>P</i> = 0.0213, indicating a significant difference between the GTV sizes of the adaptive pts (346.2 +/- 284.3 cm³) and non-adapted (153.1 +/-103.1 cm³). Multiple regression analysis was performed for esophagitis vs. plan adaptation (<i>P</i> = 0.58) adjusting for covariates of BMI (<i>P</i> = 0.14), age at onset (<i>P</i> = 0.019), and esophagus dose max (<i>P</i> = 0.07), did not distinguish a difference in toxicity between pts. Multiple regression analysis of pneumonitis vs. plan adaptation (<i>P</i> = 0.64) adjusting for covariates of both lung dose max (<i>P</i> = 0.28), R lung volume (<i>P</i> = 0.67), BMI (<i>P</i> = 0.23), and age at onset (<i>P</i> = 0.74) did not demonstrate a significant difference in toxicity between the adapted and non-adaptive pts. <h3>Conclusion</h3> Both the adaptive and non-adaptive groups had statistically equivalent toxicities; however, GTV volumes between the 2 groups were significantly different in size. By using adaptive therapy techniques, pts with large tumor sizes can be treated with an equivalent level of toxicity to patients with smaller tumors treated with traditionally.