Whole-brain radiotherapy with simultaneous integrated boost using volumetric modulated arc therapy (VMAT) for patients of recursive partitioning analysis (RPA) class I and II suffering from 1-3 brain metastases

Abstract

Objective: We evaluated the feasibility and treatment outcomes of recursive partitioning analysis (RPA) Class I and II patients with 1-3 brain metastases treated with whole-brain radiotherapy with simultaneous integrated boost using volumetric modulated arc therapy (VMAT). Materials and methods: 11 patients (9 with lung cancer, 1 with breast cancer and 1 with renal cell carcinoma), of which 3 and 8 belonging to RPA Class I and II respectively), were treated with VMAT for their brain metastases (mean volume 2.45cm3, range 0.07 – 14.48cm3). After immobilization by thermoplastic casts, they underwent planning computed tomography (CT) scan of the whole brain with 2.5mm slice thickness. The whole brain (WB), all brain metastases (BM) and organs at risks were contoured manually. A 4-mm margin was created for the whole brain and each of the brain metastases to generate the planning target volumes (PTV-WB and PTV-BM respectively). A VMAT plan with 2 modulated arcs was generated for all patients. 30Gy and 40Gy all in 10 fractions over 2 weeks were delivered simultaneously to PTV-WB and PTV-BM by a linear accelerator with a dose rate of 600 MU/minute. Serial CT scans of the brain were performed every 2-3 months after VMAT until progression or death. Overall local response rate, local brain control rate, distant brain control rate, brain progression-free survival (BPFS), progression-free survival (PFS), overall survival (OS) and toxicities were assessed. Results: After a median follow up of 7.6 months, 6 (54.5%) patients died and all succumbed to progressive disease of their underlying malignancies. Overall local response rate, local brain control rate and distant brain control rate were 81.9%, 100% and 81.9% respectively. Median BPFS, PFS and OS were 12.6 months, 10.0 months and 14.3 months respectively whereas 1-year BPFS, 1-year PFS and 1-year OS were 75.0%, 30.0% and 58.3% respectively. 2 (18.2%) and 3 (27.3%) patients developed acute grade 1 and grade 2 treatment-related toxicities during VMAT with subsequent complete resolution. Mean monitor units was 713.4 MU (range 392-891 MU) and mean beam-on time was 1.2 minutes (range 0.7-1.5 minutes). Conclusion: VMAT for 1-3 brain metastases in RPA class I and II patients seemed promising with a favorable treatment outcome as well as well-tolerated and self-limiting toxicities.