A Scalp Dose Threshold for Preventing Permanent Alopecia in Scalp-Avoidance Whole-Brain Irradiation With Volumetric Modulated Arc Radiation Therapy for Pediatric Patients With Medulloblastomas
Daichi Torizuka, Megumi Uto, Katsutsugu Umeda, Tatsuya Kamitori, Atsushi Iwai, Satoshi Saida, Itaru Kato, Yohei Mineharu, Yoshiki Arakawa, Junko Takita, Takashi Mizowaki
Abstract
Purpose: Although the overall survival of patients with medulloblastoma has dramatically improved, permanent alopecia significantly affects their quality of life. Therefore, we performed scalp-avoidance whole-brain irradiation with volumetric-modulated arc therapy (SAWB-VMAT) as a component of craniospinal irradiation (CSI). We retrospectively estimated the cutoff dose to prevent permanent alopecia in patients treated with SAWB-VMAT according to the St. Jude Medulloblastoma-96 protocol.Methods and Materials: Eight pediatric patients (median age 8.0 years, range 4.7–12.8 years) with medulloblastoma at our institution who we could take photographs following completion of the St. Jude Medulloblastoma-96 protocol treatment from May 2011 to August 2018 were enrolled in this study. All patients underwent CSI and boost radiotherapy followed by four cycles of dose-intensive chemotherapy. We defined permanent alopecia as hair loss persisting for 1 year after radiotherapy completion and 9 months after chemotherapy completion, as graded by two reviewers for each patient using the Severity of Alopecia Tool (SALT) score. Grades 3 and 4 alopecia were considered severe.Results: Equivalent doses in 2-Gy fractions (assuming α/β = 2) to 50༅ of the scalp (EQD 50%) of SAWB-VMAT was significantly reduced compared to conventional WBRT (16.6 ± 3.6 vs. 20.2 ± 5.5 Gy, P = 0.038). The optimal EQD 50% cutoff was 19.9 Gy for severe permanent alopecia (area under the curve, 84%; sensitivity, 88%; specificity, 78%). The severe alopecia area was markedly reduced based on a 19.9 Gy cutoff (15.7 vs. 84.6 %, P = 0.0001). None of the patients who received SAWB-VMAT showed disease progression 5 years after starting radiotherapy.Conclusions: SAWB-VMAT significantly reduced the scalp EQD 50% and the estimated cutoff EQD 50% was 19.9 Gy.Summary: Scalp-avoidance whole-brain irradiation with volumetric-modulated arc therapy (SAWB-VMAT) remarkedly reduced equivalent doses in 2-Gy fractions (assuming α/β = 2) to 50༅ of the scalp (EQD 50%) comparing with conventional WBRT. None of the patients who received SAWB-VMAT showed disease progression 5 years after starting radiotherapy. The optimal EQD 50% cutoff was 19.9 Gy for severe permanent alopecia.