Stereotactic ablative radiotherapy: A potentially curable approach to early stage multiple primary lung cancer

Background: Surgical resection has been the standard treatment for early stage multiple primary lung cancer (MPLC). However, a significant proportion of patients with MPLC cannot undergo surgery. For this report, the authors explored the role of stereotactic ablative radiotherapy (SABR) for patients with MPLC. Methods: Patients with MPLC who received SABR (50 grays [Gy] in 4 fractions or 70 Gy in 10 fractions) for the second tumor were reviewed. Four-dimensional, computed tomography-based, planning/volumetric image-guided treatment was used for all patients. Treatment outcomes/toxicities were analyzed. Results: For the 101 patients who received SABR, at a median follow-up of 36 months and with a median overall survival (OS) of 46 months, the 2-year and 4-year in-field local control rates were 97.4% and 95.7%, respectively. The 2-year and 4-year OS rates were 73.2% and 47.5%, respectively; and the progression-free survival (PFS) rates were 67% and 58%, respectively. Patients who had metachronous tumors had better OS and PFS than patients who had synchronous tumors (2-year OS: 80.6% metachronous vs 61.5% synchronous; 4-year OS: 52.7% vs 39.7%, respectively; P =.047; 2-year PFS: 84.7% vs 49.4%, respectively; 4-year PFS: 75.6% vs 30.4%, respectively; P =.0001). For patients who either underwent surgery or received SABR for an index tumor, the incidence of grade ≥3 radiation pneumonitis was 3% (2 of 71 patients); however, this increased to 17% (5 of 30 patients) for those who received conventional radiotherapy for an index tumor. Other grade ≥3 toxicities included grade 3 chest wall pain (3 of 101 patients; 3%) and grade 3 skin toxicity (1 of 101 patients; 1%). Conclusions: SABR achieves promising long-term tumor control and survival and may be a potential curative treatment for early stage MPLC.