Lung stereotactic body radiation therapy (SBRT) delivered over 4 or 11 days: a comparison of acute toxicity and quality of life.

Purpose: The optimal duration over which lung SBRT should be delivered is unknown. We conducted a randomized pilot study in patients treated with four fractions of lung SBRT delivered over 4 or over 11 days.

Methods: Patients with a peripheral solitary lung tumor (NSCLC or pulmonary metastasis) ≤ 5 cm were eligible. For NSCLC lung tumors ≤ 3 cm, a dose of 48 Gy in 4 fractions was used, otherwise 52 Gy in 4 fractions was delivered. Patients were randomized to receive treatment over 4 consecutive days or over 11 days. The primary end-point was acute grade ≥ 2 toxicity. Secondary end-points included quality of life (QOL) assessed using the EORTC QLQ-C30 and QLQ-LC13 questionnaires.

Results: Fifty four patients were enrolled. More patients in the 11 day group had respiratory symptoms at baseline. 55.6% patients treated over 4 days and 33.3% of patients treated over 11 days experienced acute grade ≥ 2 toxicity (p=0.085). Dyspnea, fatigue and coughing domains were worse in the 11 day group at baseline. At 1 and 4 months, more patients in the 4 day group experienced a clinically meaningful worsening in the dyspnea QOL domain compared to the 11 day group (44.5% vs 15.4%, p=0.02; 38.5% vs 12.0%, p=0.03, respectively). However, raw QOL scores were not different at these time-points between treatment groups.

Conclusions: Grade 2 or higher acute toxicity was more common in the 4 day group, approaching statistical significance. More patients treated on 4 consecutive days reported a clinically meaningful increase in dyspnea, although interpretation of these results is challenging due to baseline imbalance between treatment groups. Larger studies are required to validate these results.