An Institution-Specific Hypofractionated Radiation Therapy Regimen in the Treatment of Central and Ultracentral Non-small Cell Lung Cancer.

Purpose/objectives: While stereotactic body radiation therapy (SBRT) or hypofractionated radiation therapy (HFRT) is routinely used to treat inoperable 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 0-2 cm of critical mediastinal structures (CMSTs), we employ an institution specific hypofractionated radiation regimen (isHFRT) with a biologically effective dose (BED) of 98.59 using 17 fractions to a dose of 6987 cGy.

Methods: We conducted a single-institution retrospective review of patients with esNSCLC treated with this isHFRT between 2011 and 2020, evaluating both tumor control rates and rates of treatment related toxicity.

Results: Of the 31 patients evaluated, 61.3% of patients had UCTs while 38.7% had cenTs. At 1- and 3 years, local control (LC) was noted to be 93.5% and 86.8% respectively. 1-year overall survival (OS) was 74.2% for all comers, 75.0% for patients with cenTs and 73.7% for patients with UCTs (p = 0.70). 3-year OS was 20.8%. Only 22.6% of patients who expired at 1-year experienced disease progression. At 12 months, adverse event free survival (AEFS) was 67.7%. While 25.8% (n = 8) of patients experienced a Grade 2 (G2) or greater toxicity, no patient experienced a G2 or greater cardiotoxicity. Only 1 patient (3.3%) experienced a Grade 5 toxicity (fatal hemoptysis 12-months following treatment). Review of the case demonstrated that the maximum tracheobronchial tree dose had been exceeded.

Conclusions: Our isHFRT 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 prior studies.