Outcomes and Toxicity Following Three or More Definitive Courses of Thoracic Radiation Therapy

Abstract

<h3>Purpose/Objective(s)</h3> Lung cancer patients are living longer but remain at risk for developing new or recurrent disease. Salvage re-irradiation can be considered for definitive management, but balancing efficacy with associated toxicity poses difficulty with retreatment. <h3>Materials/Methods</h3> This retrospective study evaluates patients who underwent three or more courses of definitive RT for thoracic malignancies at our cancer center from 2012 through 2021. All patients underwent multidisciplinary evaluation and restaging prior to retreatment. Toxicity was scored via CTCAE v5.0, and outcomes were estimated via Kaplan-Meier. <h3>Results</h3> Fifty-nine patients underwent a total of 190 definitive courses (13 having received 4 courses) for new or recurrent thoracic malignancies (88% non-small cell lung cancer). Of these courses, 141 (74%) entailed SBRT for localized lesions (most commonly to 50-Gy in 4-fractions), while the remaining 49 (26%) consisted of conventional fractionation (most often delivered with concurrent chemotherapy), with 22 patients (37%) receiving SBRT for every course. Median follow-up time was 7-years and 20-months from initial diagnosis and last RT course, respectively. All patients maintained excellent performance status (ECOG 0-2 or KPS 70-90) from first to last treatment. Median age at initial diagnosis and at last course of thoracic RT was 68.5 and 71 years, respectively, corresponding to median interval from initial RT to last RT course of 4 years. Twenty-eight patients (47%) had history of pulmonary disease, while 19 (32%) had history of prior lobectomy. Following last thoracic RT, median overall survival (OS) and progression-free survival (PFS) were still 2.4 years (95% CI: 1-4) and 12-months (95% CI 7-18), respectively. Actuarial OS at 1-year and 2-years was 73% and 54%, corresponding to PFS of 50% and 27%. However, 47 patients (80%) ultimately had evidence of progression, including distant metastases among 20 (43%), isolated locoregional recurrences in 19 (40%), and both as first progression for 8 (17%). Following last RT, the incidence of Grade 3 toxicity was only 5% (pulmonary and esophageal), with no Grade 4-5 events. There were no cardiac, neurological, or vascular toxicities directly attributable to RT. <h3>Conclusion</h3> Re-RT often remains a safe and effective local control modality (despite prior treatment) and should be considered as a potential option when planning multidisciplinary salvage therapy. For isolated failures, multiple courses of thoracic RT (notably SBRT) can be delivered sequentially with minimal toxicity.