Whole-brain irradiation with simultaneous integrated boost by helical tomotherapy for multiple brain metastases: dosimetric and clinical analyses

Objective To retrospectively analyze the dosimetry and efficacy of whole-brain irradiation (WBRT) with simultaneous integrated boost (SIB) by helical tomotherapy (HT) in the treatment of multiple brain metastases (BMs), and to evaluate the feasibility, efficacy, and safety of HT. Methods From 2014 to 2017, a total of 43 patients with multiple BMs (no less than 3 lesions) were enrolled as subjects. A dose of 40 Gy was delivered to the whole brain in 20 fractions, while a dose of 60 Gy was delivered to the gross target volume (GTV) in 20 fractions. Patients were reexamined by magnetic resonance imaging during treatment. The radiation field would be shrunk if GTV was reduced. Target coverage (TC), conformity index (CI), prescription isodose/target volume (PITV) ratio , and homogeneity index (HI) were assessed. Clinical indices included local recurrence-free survival (LRFS), intracranial progression-free survival (IPFS), progression-free survival (PFS), overall survival (OS), and toxicities. Results The median lesion number was 6(3-36) and the median total volume of GTV was 8.74 cm3. The TC, CI, PITV, and HI for GTV were 0.96±0.028, 0.51±0.164, 2.09±1.245, and 0.12±0.066, respectively, while the TC and HI for the whole brain were 0.95±0.033 and 0.43±0.161, respectively. In all the patients, 26% had replanning during treatment. The two-stage treatment reduced the radiation dose to organs at risk. The 1-year LRFS, IPFS, PFS, and OS rates were 96%, 80%, 39%, and 86%, respectively. No grade ≥3 toxicities were observed. Conclusions WBRT with SIB by HT achieves satisfactory conformity, homogeneity, efficacy, and safety, which is a recommended treatment plan for multiple BMs. Replanning during treatment can better protect normal tissue. Key words: Brain neoplasms metastases, brain/helical tomotherapy; Whole brain radiation; Simultaneously integrated boost