Ten years outcomes after SABR in central and ultracentral primary lung tumors.

Purpose: SABR performed for central and ultracentral lung tumors is associated with increased toxicity but limited data is available on late toxicities. We studied toxicity in patients followed-up ≥ 2 years post-SABR at a single-institution.

Methods: All patients were treated using VMAT for a primary or recurrent central lung cancer between 2008-2015. 60 Gy was delivered in 8 or 12 fractions. Grade ≥ 3 clinical and radiological bronchial toxicity was scored. Multivariable Cox regression models were used to estimate hazard ratios.

Results: Of 127 eligible patients, 63% were treated with 8 fractions. Median tumor diameter was 4.4 cm (range 1.3-12.0). Median overall survival was 25.0 months (95% CI 16.5-33.5); 4% developed isolated local recurrences. The actuarial 5-year rate for severe clinical toxicity was 34.1% (95% CI 21.2-44.9). Both clinical toxicity and fatal lung haemorrhage were most observed when tumors were located ≤ 1 cm from the trachea or main bronchi (46% of all cases). The 5-year actuarial rate of radiological bronchial toxicity was 37.5% (95% CI 21.5-50.2). Multivariable analysis revealed that a performance score of 2 or 3 (HR 3.6; 95% CI 1.7-7.8), and tumor location ≤ 1 cm from the trachea or main bronchi (HR 4.3; 95% CI 1.2-14.9) were significant predictors for severe clinical toxicity.

Conclusion: The actuarial rates for both severe clinical and radiological bronchial toxicity after central SABR was approximately 35% in patients surviving 5 years. Patients with tumors located ≤ 1 cm from the trachea or main bronchus were at the highest risk for severe clinical toxicity.