M. Bouchard1, A. Caron2, G. A. Turgeon1, S. Provencher1, H. Lavoie-Gagnon1, D. Amzallag1,3, I. Soucy1, S. Lemaire-Paquette4, and M. E. Plourde1; 1Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, QC, Canada, 2Université de Sherbrooke, Sherbrooke, QC, Canada, 3Jewish General Hospital, Montreal, QC, Canada, 4Centre de Recherche du Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, QC, Canada
Purpose/Objective(s): Single-fraction stereotactic ablative body radiation (SF-SABR) has been recognized in consensus guidelines as a treatment option for Stage I non-small cell lung cancer (NSCLC). However, concerns regarding toxicity and local control have limited its use. We present data on toxicity and disease control from our institution’s SF-SABR experience delivering up to 34 Gy for peripheral NSCLC. We hypothesized that the SF-SABR long-term toxicity profile and oncological outcomes are comparable to traditional fractionated approaches. Materials/
Methods: We conducted a retrospective review of 203 consecutive patients treated with SF-SABR for a total of 230 NSCLC lesions between May 16, 2018, and May 31, 2023. Patients had a minimum follow-up of 6 months. We analyzed patient and cancer characteristics, physician-reported toxicity, site of relapse, progression-free survival (PFS), cancer-specific survival (CSS) and overall survival (OS). Research ethics board approval was obtained for this study. Survival rates were assessed using Kaplan-Meier curves, and subgroup comparisons were made using the log-rank test. Results: The median [IQR] follow-up duration for the 203 patients enrolled in the study was 28.1 months [20.3-35.9]. The median age was 74 [68-79] years. Lesions analyzed comprised stage I-II (91.3%) and oligometastatic disease (8.7%). Pathological diagnosis was obtained in 30.6% of cases. Reasons for omitting biopsy included poor pulmonary function tests (39.8%), patient refusal (13.3%) and other reasons (46.9%). Median tumor size was 1.4 cm (range 0.5-4.2 cm). Doses administered were < 30 Gy (13.5%), 30 Gy (54.8%), or 34 Gy (31.7%). Ninety-one lesions (40.6%) had an ITV located = 0.5 cm from the chest wall. Chest pain was reported in 10.5% of cases, with only 4.5% classified as grade 2 and no grade 3 or higher. Rib fractures occurred in 3.2% of cases. Lung toxicities were limited to 3.2% grade 2 and 0.9% grade 3, with no grade > 3 treatment-related toxicities. Two-year local, regional, and distant control rates were 94.0%, 94.8%, and 93.3%, respectively. Median PFS was 39.2 months, with 2-year PFS, OS, and CSS rates of 66.7%, 75.0%, and 85.6%, respectively. Predictors of local control were low SUV max (p = 0.05), and dose = 30 Gy (p = 0.008) but no difference was found between 30 and 34 Gy (p = 0.4). The percent of local recurrence for lesions receiving < 30 Gy, 30 Gy and 34 Gy were respectively 19%, 3% and 5.7%. Local control did not significantly vary with tumor location, biopsy-proven status or histology. Conclusion: This 5-year experience confirms previously published data suggesting that SF-SABR for peripheral NSCLC is a suitable treatment option with a favorable toxicity profile and effective disease control. It highlights the significance of a dose of at least 30 Gy to optimize the likelihood of local control. The low rate of pathological diagnosis of cancer may have contributed to the favorable oncological outcomes observed.
