Stereotactic boost on residual disease after external-beam irradiation in clinical stage III non-small cell lung cancer: mature results of stereotactic body radiation therapy post radiation therapy (SBRTpostRT) study

Purpose: To evaluate the role of stereotactic body radiation therapy (SBRT) delivered after external-beam fractionated irradiation in non-small-cell lung cancer (NSCLC) patients with clinical stage III A, B. Materials and methods: All patients received three-dimensional conformal radiotherapy (3D-CRT) or intensity modulated radiation therapy (IMRT) (60–66 Gy/30–33 fractions of 2 Gy/5 days a week) with or without concomitant chemotherapy. Within 60 days from the end of irradiation, a SBRT boost (12–22 Gy in 1–3 fractions) was delivered on the residual disease. Results: Here we report the mature results of 23 patients homogeneously treated and followed up for a median time of 5.35 years (range 4.16–10.16). The rate of overall clinical response after external beam and stereotactic boost was 100%. No treatment-related mortality was recorded. Radiation-related acute toxicities with a grade ≥ 2 were observed in 6/23 patients (26.1%): 4/23 (17.4%) had esophagitis with mild esophageal pain (G2); in 2/23 (8.7%) clinical radiation pneumonitis G2 was observed. Lung fibrosis (20/23 patients, 86.95%) represented a typical late tissue damage, which was symptomatic in one patient. Median disease-free survival (DFS) and overall survival (OS) were 27.8 (95% CI, 4.2–51.3) and 56.7 months (95% CI, 34.9–78.5), respectively. Median local progression-free survival (PFS) was 17 months (range 11.6–22.4), with a median distant PFS of 18 months (range 9.6–26.4). The 5-year actuarial DFS and OS rates were 28.7% and 35.2%, respectively. Conclusions: We confirm that a stereotactic boost after radical irradiation is feasible in stage III NSCLC patients. All fit patients who have no indication to adjuvant immunotherapy and presenting residual disease after curative irradiation could benefit from stereotactic boost because outcomes seem to be better than might be historically assumed.