Long term efficacy and toxicity after stereotactic ablative reirradiation in locally relapsed stage III non-small cell lung cancer

Background In stage III non-small cell lung cancer (NSCLC) treated with concomitant chemoradiotherapy, there is a high rate of relapse. Some of these relapses are only local and can be treated by stereotactic ablative radiation therapy (SABR). Previous studies reporting outcome after SABR reirradiation of the thorax consisted of a heterogeneous population of various lung cancer stages or even different types of cancer. The purpose of study is to evaluate toxicity and outcome of this strategy in locally relapsed stage III NSCLC only. Methods From February 2007 to November 2015, 46 Stage III NSCLC patients treated with SABR, for lung recurrence following conventionally fractionated radiation therapy (CFRT), were retrospectively analyzed. Results Median follow-up was 47.3 months (1–76.9). The 2 and 4-year progression-free survival (PFS), and overall survival (OS) were of 25.5%/8.6 and 48.9%/30.8%, respectively. Highest presenting toxicity in patients (grade 1 through 5) was: 13 (28.3%), 7 (15.2%), 1 (2.2%), 0 and 2 (4.4%), with deaths due to hemoptysis ( n = 1) and alveolitis ( n = 1). Although the Biological Effective Dose (at Planning Tumor Volume isocenter) was lower for central tumors treated for an in-field relapse ( n = 21, 116 Gy versus 168 Gy, p = 0.005), they had no significant difference in OS than the remaining cohort, but with a higher rate of grade 2–5 toxicities (OR = 0.22, [0.06–0.8], p = 0.02). Conclusion Reirradiation with SABR for local relapse in patients previously treated for stage III NSCLC, is feasible and associated with good outcome. This is also true for central tumors treated for an in-field relapse, but should be radiated with caution to mitigate toxicity.