Toxicity of Patients with Ultra-Central Thoracic Tumors Treated with Stereotactic Body Radiotherapy (SBRT) with Dose of 50 Gy in 5 Fractions

Abstract

The ideal regimen for stereotactic body radiotherapy (SBRT) in ultra-central lung tumors is still to be defined, mostly due to the risk of unacceptable or fatal toxicity. There is not much information on outcomes after SBRT for this group of patients. We summarize here our experience with ultra-central lung cancer patients treated with the dose of 50 Gy delivered in 5 fractions. This study is a retrospective review of all cases of ultra-central thoracic tumors treated with SBRT with the dose of 50 Gy in 5 fractions, delivered every other day, at our institution. In all cases, as we defined ultra-central lung tumor, the PTV overlapped or touched one or more of the following structures: bronchial tree, trachea, great vessels, heart, and esophagus. Metastatic and primary lung lesions were included. The volumes of treatment were defined by 4D-CT to consider breathing motion. Normal organs constraints followed the recommendations of the RTO 0813 trial as follows: Spinal cord: max 30 Gy. Lung right or lung left: V13 Gy[cc] < 1500. Esophagus: max 52 Gy and nonadjacent esophagus: V27.5 Gy[cc] < 5. Heart: V32 Gy[cc] < 15; max 52 Gy. Great vessels: max 52 Gy and non-adjacent great vessels V47 Gy[cc] < 10. Trachea plus bronchus: max 52 Gy and non-adjacent V18 Gy[cc] < 4. Follow-up, at the discretion of the treating MD, included periodic CT scans of the thorax after SBRT and assessment of radiation-induced toxicity scored with CTCv3.0. Between December 2015 and February 2022, 86 patients were eligible for this review. Median follow-up was 17 months (range: 1-76 months); the median age was 74 years (range: 37-98 years). Histology was as follows: 50 patients had biopsy proved NSCLC, 16 had no biopsy, and 20 had metastatic non-lung primaries. Overlapped structures were as follows: with great vessels in 46 cases, heart in 20 cases, trachea/branchial tree in 18 cases, and esophagus in 2 cases. In 16 patients the overlap was present in more than one structure. Overall, 68.6% did not report acute toxicity. The most common acute side effects were fatigue (15.1%), coughing (8.1%), shortness of breath (6.9%), esophagitis (2.3%), and dysphagia (1.1%). No grade 3 or more significant toxicity was described. As acute side effects, many patients had exacerbations of the previous condition, such as shortness of breath (16 pts) or coughing (4 pts) during follow-up. Pneumonitis was found as a late side effect in four cases. One patient had empyema associated with a fistula in the non-irradiated lung, where the patient had previous surgery, but in the irradiated lung no severe complication was detected. There were no deaths attributed to the SBRT treatment. 67.5% of 86 patients were alive at the time of the review; 87.2% had local control, and 65.1% had metastases-free survival. In this cohort of patients, no death or even severe acute or chronic toxicity was attributed to SBRT. SBRT seems safe for ultra-central lesions using the regimen of 50 Gy in 5 fractions with the constraints of the RTOG 0813 trial.