Quantitating Interfraction Target Dynamics During Concurrent Chemoradiation for Glioblastoma: A Prospective Serial...

Area of Science:

• Oncology
• Radiotherapy
• Medical Imaging

Background:

• Magnetic resonance image (MRI) guided radiation therapy offers potential for improved glioblastoma treatment outcomes.
• Adapting radiation therapy to real-time tumor changes can enhance treatment efficacy.

Purpose of the Study:

• To quantify interfraction dynamics, including tumor size, position, and geometry, during standard 6-week chemoradiation for glioblastoma.
• To assess temporal changes in gross tumor volumes (GTVs) and clinical target volumes (CTVs) using sequential MRI scans.

Main Methods:

• Prospective imaging of 61 patients using T1-weighted contrast-enhanced and T2/FLAIR sequences at multiple time points during chemoradiation.
• Contouring of GTVs and CTVs at planning, fraction 10, fraction 20, and 1 month post-treatment.
• Quantification of target dynamics using absolute volume, relative volume (Vrel), and migration distance (dmigrate), analyzed with a linear mixed-effects model.

Main Results:

• Median GTV volume significantly decreased from planning scans to 1 month post-treatment (P < .001).
• Significant interfraction migration distances (>5 mm) were observed in over 40% of patients for both GTV and CTV at various treatment points.
• Forty percent of patients showed decreased GTV with significant migration (>5 mm), indicating dynamic tumor changes during therapy.

Conclusions:

• Clinically significant tumor dynamics occur during glioblastoma chemoradiation.
• These findings support the evaluation of daily MRI-guided radiation therapy and adaptive treatment planning for glioblastoma.