Glioblastoma (GBM) is an aggressive primary brain tumor with a high recurrence rate despite multimodal treatment approaches. Adaptive radiation therapy (ART) involves adjusting the treatment plan based on tumor and resection cavity changes during radiotherapy, potentially improving treatment precision while reducing radiation exposure to normal brain tissue. However, the clinical outcomes and recurrence patterns associated with ART remain unclear. We aimed to evaluate the efficacy of ART for GBM treatment, focusing on survival outcomes and recurrence patterns.

We retrospectively analyzed a prospectively collected cohort of 59 patients with pathologically confirmed GBM who received postoperative three-dimensional conformal radiotherapy (3D-CRT)–based ART between April 2015 and November 2018. Mid-treatment magnetic resonance imaging was performed after delivery of 34–36 Gy. Based on these images, an offline single-time-point ART boost plan was generated to accommodate changes in tumor size and the resection cavity. Radiotherapy consisted of 40 Gy in 20 fractions to the initial target, followed by a 20 Gy boost in f10 fractions (total 60 Gy in 30 fractions over six weeks). Progression-free survival (PFS) and overall survival (OS) were estimated using the Kaplan–Meier method. Recurrence patterns were classified by the spatial relationship between recurrent tumor volume and the 95% isodose line.

During a median follow-up period of 19.2 (range, 2.1–81.6) months, 36 patients (61.0%) experienced tumor recurrence, and 32 (54.2%) died. The 1- and 2-year OS rates were 93.9% and 54.6%, respectively, with a median OS of 26.6 months. The 6- and 12-month PFS rates were 71.1% and 46.1%, respectively, with a median PFS of 10.5 months. Central recurrence was the most common pattern (29 patients, 78%), followed by distant (5 patients, 14%) and in-field recurrences (3 patients, 8%). Marginal recurrence was not observed. No cases of grade 2 or higher radiation necrosis were observed, and only two cases of grade 1 radiation necrosis were identified.

ART for GBM is associated with favorable survival outcomes and low toxicity. ART does not increase the risk of marginal recurrence, and the incidence of radiation necrosis is low. Further studies are required to optimize ART protocols to maximize their clinical benefits.