2094 - Assessing the Safety and Efficacy of a Hypofractionated Regimen in the Treatment of Early-Stage Non-Small Cell Lung Cancer Patients with Central or Ultracentral Tumors

M. Lubas¹, S. S. Kumar², and J. Fredette³; ¹Fox Chase Cancer Center, Philadelphia, PA, United States, ²University of Kentucky, Lexington, KY, ³Fox Chase Cancer Center, Philadelphia, PA

Purpose/Objective(s): While stereotactic body radiation therapy (SBRT) or hypofractionated radiation therapy (HFRT) is routinely used to treat early-stage non-small lung cancer (esNSCLC) patients with peripheral tumors, SBRT or HFRT for central (cenT) and ultracentral tumors (UCT) remains controversial. To treat patients with tumors located within 0.5 cm to 2 cm of critical mediastinal structures, we often utilize an institution-specific hypofractionated regimen (isHFR) using 17 fractions to a dose of 6987 cGy. Our study seeks to evaluate the safety and efficacy of this fractionation scheme, while comparing patients’ adverse-event free survival (AEFS), overall survival (OS), and progression free survival (PFS) outcomes to historical data. Materials/

Methods: We conducted a single-institution retrospective review of patients with eNSCLC treated with isHFR between 2011 and 2019, evaluating rates of Grade 2 or higher hemoptysis (HP), bronchial stricture or necrosis (BSN), radiation pneumonitis and cardiotoxicity (CardT) based on CTCAE criteria. Kaplan Meier survival models were created to assess OS, AEFS and PFS in cenTs and UCTs. Differences were assessed using log-rank tests. Relative frequencies for categorical variables of interest were also dichotomized by tumor centrality and then compared using Fisher’s Exact tests while continuous variables of interest were compared using Wilcoxon Rank Sum Tests.
Results: Of the 32 patients evaluated, 62.5% of patients enrolled had UCTs while 37.5% of enrolled patients had cenTs. The rate of locoregional control was noted to be 87.5% while rate of distant control was 78.1%. The probability of survival at 1 year was noted to be 75.0% while median OS was 19.3 months, 95% CI [13.94, 29.42]. Median OS for cenTs was 21.2 months and 18.2 months for UCTs, 95% CI [5.13, 31.76] and [11.77, 31.43] (p=0.7706). AEFS at 12 months was 68.8%. 2 patients (6.3% of the cohort) experienced Grade 5 toxicity with 1 UCT patient experiencing Grade 5 BSN and the other cenT patient experiencing Grade 5 HP. Our patient who experienced BSN did so about 9 months following treatment and had noted PET avid recurrent disease in the mediastinum. The second patient experienced G5 hemoptysis approximately 1 year following treatment. The patient’s most recent CT scan demonstrated post-radiation changes, although recurrent disease could not be excluded. She was scheduled for a PET CT but expired shortly before this study was performed. Only 1 patient (3.1% of the cohort) experienced CardT, a myocardial infarction, approximately 3 years following treatment. While this patient did not have a known coronary artery disease, he did have significant risk factors including hypertension and hyperlipidemia, as well as a strong family history.
Conclusion: Our isHFR for patients with esNSCLC proves a safe and effective treatment for medically inoperable esNSCLC patients with cenTs and UCTs with comparable rates of toxicity when compared to historical norms, as well as notably low rates of cardiotoxicity.