Contrast-enhancing Lesions Induced by Central Nervous System-directed Intensity Modulated Proton Therapy:...

Area of Science:

• Radiation Oncology
• Neuro-oncology
• Medical Imaging

Background:

• Intensity modulated proton therapy (IMPT) offers precise radiation delivery for brain tumors.
• Intracranial radiation-induced contrast enhancement (RICE) is a potential side effect of IMPT, but its characteristics are not well-defined.

Purpose of the Study:

• To define the incidence, distribution, kinetics, predisposing factors, and clinical outcomes of RICE following IMPT.
• To investigate the association between radiation dose, linear energy of transfer (LET), and RICE development.

Main Methods:

• Analysis of RICE in 137 brain tumor patients treated with at least 50 Gy IMPT, with 1-year follow-up and 3 MRI scans.
• Classification of RICE distribution relative to the tumor bed and high-dose regions (≤5 mm from 95% isodose line).
• Voxelized dose and LET computation for RICE lesions; risk factor assessment using logistic regression.

Main Results:

• 26% of patients (36/137) developed RICE, with 73 lesions observed at a median of 11 months post-IMPT.
• Most RICE lesions (67%) were in the high-dose region (Group B), and 78% improved or resolved within 5 months.
• RICE risk increased with patient age, larger tumor volume (>30 cc), and proximity of the 95% isodose line to ventricles.

Conclusions:

• RICE is a frequent radiographic finding after IMPT, predominantly in periventricular and high-dose areas.
• RICE is infrequently symptomatic, with most lesions showing improvement over time.
• Consideration of periventricular-sparing techniques during IMPT planning may mitigate RICE risk.