A prospective comparison of adaptive and fixed boost plans in radiotherapy for glioblastoma

• Published in: Radiation oncology (London, England) Vol. 17; no. 1; p. 40
• Main Authors: Matsuyama, Tomohiko, Fukugawa, Yoshiyuki, Kuroda, Junichiro, Toya, Ryo, Watakabe, Takahiro, Matsumoto, Tadashi, Oya, Natsuo
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 22-02-2022; BioMed Central; BMC
• Subjects: Adaptive radiotherapy; Aged; Care and treatment; Comparative analysis; Excision (Surgery); Female; Glioblastoma; Glioblastoma - diagnostic imaging; Glioblastoma - radiotherapy; Glioblastoma multiforme; Humans; Magnetic Resonance Imaging; Male; Methods; Middle Aged; Patient outcomes; Prospective Studies; Radiotherapy; Radiotherapy - methods; Japan; Glioblastoma; Adaptive radiotherapy
• ISSN: 1748-717X; 1748-717X
• DOI: 10.1186/s13014-022-02007-4

To analyze the efficacy of adaptive radiotherapy (ART) for glioblastoma.
Sixty-one glioblastoma patients who received ART were prospectively evaluated. The initial clinical target volume (CTVinitial) was represented by T2 hyperintensity on postoperative MRIs (pre-RT MRI [MRIpre])plus 10 mm. The initial planning target volume (PTVinitial) was the CTVinitial plus a 5-mm margin. The PTVinitial received 40 Gy. An MRI and a second planning CT were performed during radiotherapy (MRImid). Two types of boost CTVs (the resection cavity and residual tumor on enhanced T1-weighted MRI plus 10 mm) were created based on the MRIpre and MRImid (CTVboost-pre and -mid). The boost PTV (PTVboost) was the CTVboost plus 5 mm. Two types of boost plans (fixed and adaptive boost plans in the first and second planning CT, respectively) of 20 Gy were created. The PTV based on the post-RT MRI (PTVboost-post) was created, and the dose-volume histograms of the PTVboost-post in the fixed and adaptive boost plans were compared. Additionally, the conformity indices (CIs) of the fixed and adaptive boost plans were compared.
The median V95 of the PTVboost-post of the fixed and adaptive boost plans (V95pre and V95mid) were 95.6% and 98.3%, respectively (P < 0.01). The median V95pre and V95mid of patients after gross total resection (GTR) were 97.4% and 98.8%, respectively (P = 0.41); in contrast, the median values of patients after non-GTR were 91.9% and 98.2%, respectively (P < 0.01). The median CIs of the fixed and adaptive boost plans in all patients were 1.45 and 1.47, respectively (P = 0.31). The median CIs of the fixed and adaptive boost plans in patients after GTR were 1.61 and 1.48, respectively (P = 0.01); in contrast, those in patients after non-GTR were 1.36 and 1.44, respectively (P = 0.13).
ART for glioblastoma improved the target coverage and dose reduction for the normal brain. By analyzing the results according to the resection rate, we can expect a decrease in normal brain dose in patients with GTR and an increase in coverage in those with partial resection or biopsy.