P2.05-051 Safety of Lung Stereotactic Body Radiotherapy (SBRT): A Single Institution Prospective Study Based on RTOG 0915 Protocol Constraints: Topic: Toxicities

Abstract

To evaluate toxicity of RTOG 0915 protocol’s constraints in lung SBRT for patients treated with 60Gy in 5 fractions. Between 2010 and 2015, 77 pts were treated with SBRT for single or multiple lung lesions, 43 pts (55.8%) for primary tumor and 34 pts (44.2%) for metastatic lesion. A total of 80 lesions were treated. Four dimensional CT images were acquired; maximum intensity CT reconstruction was used for ITV delineation and average CT reconstruction for OAR contouring and dosimetric calculation.We prescribed 57Gy to 95% of PTV volume and OAR constraints are reported in table 1. Dose calculation was performed in 70% of the cases with collapsed cone convolution algorithm and 7 fields 3D technique and the remaining 30% with Monte Carlo dose calculation and intensity modulated fields (dynamic MLC and VMAT tecniques). Treatments were delivered in 28% of the cases on Elekta-Precise accelerator with electronic portal films on-line setup verifications and the remaining 72% on Elekta-Agility accelerator with cone beam CT. We evaluated pre-treatment respiratory function and we treated only pts with %FEV1 > 40%. We reported toxicity following CTCAE v3.0 score. All the dose/constraints were respected except for the chest wall dose that was higher than 30 Gy in 8 pts (10.3%). Toxicity was evaluated in all the patients except one that was lost in follow-up. We found only lung or chest wall toxicity: 11 pts (14.2%) with a G2 dyspnea, one patient with a G3 dyspnea; 8 pts with a G2 chest wall pain and 1 with a symptomatic rib fracture. We find more lung toxicity in patients with primary tumor because of more chronic lung disease prior to the treatment. The use of these SBRT constraints is safe in both metastatic and primary lung lesions, with a particular attention on pre-treatment respiratory function.