Helical Tomotherapy for Whole-Brain Irradiation with Integrated Boost to Multiple Brain Metastases: Dosimetric Analysis and Clinical Outcomes

Abstract

A retrospective study was conducted to analysis the dose distribution characteristics, and evaluate the feasibility and toxicities of Tomotherapy for whole brain irradiation (WBRT) with simultaneously integrated boost (SIB) to multiple brain metastases (BMs). From 2014 to 2017, 43 patients with three or more BMs were analyzed. WBRT and SIB were delivered with 40 Gy and 60 Gy in 20 fractions by Tomotherapy. Patients were reexamined by magnetic resonance imaging (MRI) during treatment. The radiation field would be shrunk if the gross target volume (GTV) reduced. Target Coverage (TC), conformation number (CN), prescription isodose/ target volume ratio (PITV) and homogeneity index (HI) was accessed. Clinical endpoints included local recurrence- free survival (LRFS), intracranial progresstion- free survival (IPFS), progression- free survival (PFS), overall survival (OS) and toxicities. The median lesion number was 6 (3-36) and median total volume of GTV was 8.74 cc (0.37-120.32 cc). Median GTV Dmean was 63.1 Gy (50.2-72.58 Gy). Mean± standard deviation for GTV amounted to TC= 0.96±0.028, CN= 0.51±0.164, PITV= 2.09±1.245, and HI= 0.12±0.066, respectively. TC and HI for whole brain were 0.95±0.033 and 0.43±0.161, respectively. A total of 25.6% of patients got replanned and the mean dose of normal tissue reduced by 0.7-2.0 Gy. One-year LRFS, IPFS, PFS and OS were 95.7%, 79.9%, 39.4%, and 85.6%, respectively. There were no grade 3-5 toxicities. Tomotherapy for WBRT and SIB showed excellent conformity and homogeneity, and it’s efficient and safe for patients with multiple BMs. Lesions that got shrunk during treatment should be replanned to reduce the dose of normal tissue.