Thoracic reirradiation with SBRT for residual/recurrent and new primary NSCLC within or immediately adjacent to a prior high-dose radiation field

Purpose: Local failure following concurrent chemoradiation and in-lobe failures following stereotactic body radiation therapy (SBRT) are common. We evaluated our institutional experience using SBRT as salvage in this setting. Methods and materials: Seventy-two patients were reirradiated with SBRT for residual, locally recurrent, or new primary non-small cell lung cancer within or adjacent to a high-dose external beam radiation therapy or SBRT field. Kaplan-Meier analysis with log-rank test were used to estimate endpoints and differentiate cohorts. Results: Median follow-up was 17.9 months. Patients had residual or recurrent disease (54.2%); 45.8% had new lung primaries. Median reirradiated T size was 2.5 cm (range, 0.8-7.8 cm). Median pre-retreatment maximum standardized uptake value (SUV_max) was 7.15 (range, 1.2-37.6). The most common SBRT reirradiation regimen was 48 Gy in 4 fractions (range, 17-60 Gy in 1-5 fractions). Median progression-free survival was 15.2 months, and median overall survival was 20.8 months. Two-year local failure was 21.6%. Patients with SUV_max at reirradiation <7.0 had a 2-year local control of 93.1% versus 61.1% above the median (P <.001). The 2-year rate of distant metastases was 10.4% versus 54.1% in patients treated for a new primary versus residual or recurrent disease (P <.001). Median progression-free survival was 31.9 months versus 8.4 months, respectively (P =.037). Median survival of patients treated for new primary was 25.2 months versus 16.2 months with residual or recurrent disease (P =.049), and median survival for patients with reirradiation SUV_max below the median was 42.0 months versus 9.8 months above the median (P <.001). Acute any-grade toxicity was seen in 29.2% of patients, acute grade 3 toxicity in 11.1%, and late grade 3 toxicity in 1.4% with no treatment-related deaths. Conclusions: SBRT appears to be a safe and effective means of salvaging recurrent, residual, or new primary NSCLC in or adjacent to a previous high-dose radiation field.