Clinical outcomes and lung toxicities after lung SABR using dynamic conformal arc therapy: a single-institution cohort study

Abstract

Background: Stereotactic ablative radiotherapy (SABR) is a validated treatment for early stage lung cancer and pulmonary metastases. It provides a high local control rate with low symptomatic toxicities. Recently, Dynamic Conformal Arc Therapy (DCAT), a delivery option that differs from conventional DCA, has been implemented in the Monaco Treatment Planning System for SABR. The aim of the study was to report clinical outcomes and toxicities for patients treated for lung SABR with this new technique. Methods: We retrospectively identified adult patients treated for primary or secondary lung tumors with DCAT-SABR and reported their clinical, radiological, histological characteristics and dosimetric parameters. Total dose was delivered in 3 or 5 fractions for 95% of patients and prescribed on the 80% isodose line to the PTV periphery. Results: 145 patients met inclusion criteria for a total of 152 lesions with a median follow up of 12 months. Local control for the irradiated site was 96.7% at 1 year. Overall survival was 93.1% at 1 year. Mean prescription dose in BED10 was 110 Gy. 92% of patients had a prescribed dose superior to 100 Gy BED10. Mean PTV coverage was 95.1%. There were 66 cases of grade 1 radiation pneumonitis (RP) (43%) and only 7 cases of symptomatic grade 2 RP (4.6%). Conclusion: Lung SABR for primary or metastatic lung tumors using dynamic conformal arc therapy provides efficient results of local control and low lung toxicities, similar to other SABR techniques. Advances in knowledge: SABR using DCAT is a safe technique to treat lung lesions, allowing intra-fraction motion limitation, potentially higher OARs protection and a shortened beam delivery.