Abstract Details

Title Association of Linear Energy Transfer and Dosimetry With Radiation-induced Contrast Enhancement After Proton Therapy in Adult CNS Tumors

Topic Neuro-oncology

Presentation(s) P6 - Poster Session 6 (5:00 PM-6:00 PM)

Poster/Presentation
Number 6-008

Objective We analyzed the relationship between Radiation Induced Contrast Enhancement (RICE), Relative Biological Effectiveness (RBE) and Linear Energy Transfer (LET) in a retrospective, single institution case-control study.

Background Proton radiation therapy (PRT) is an emerging modality for treatment of adult CNS tumors. PRT may lead to increased toxicity at sites of dose deposition.

Design/Methods

150 consecutive adult patients with a histopathologic diagnosis of a CNS malignancy who underwent PRT between 2019 – 2023 with at >1 year of follow-up imaging were included. RICE was defined as new contrast enhancement lesion within the radiation field with no suspicion of tumor recurrence. Matched control group was selected based on age, gender, follow-up, tumor diagnosis, grade and location. The computed RBE dose and dose averaged LET (dLET) distributions of target and organs at risk (OARs) was performed using the Monte Carlo Method. Maximum, minimum and average RBE and LET were recorded.

Results

RICE was identified in 11 patients. Diagnosis included 5 astrocytoma, 2 meningioma, 2 oligodendroglioma, 1 tectal glioma and 1 high-grade glioma. The median time after radiation for RICE was 9.5 months. Prescription dose was 54 Gy (RBE) (range, 45.0-60.0) with the fraction dose 1.8Gy or 2Gy. The median dose in RICE was 54.48 Gy (range 45.01-61.37 Gy). Median LET values in RICE was 2.8 keV/ μm (range of 2.3 to 4.7 keV/ μm. Median LET was 2.45 keV/ μm with the GTV (range 2.16 - 2.90 keV/ μm). Mean LET values to RICE was higher than to GTV or boost GTV volume in 8 of 11 cases. We are expanding the study to explore the interaction between radiation dose and LET with appearance of RICE.

Conclusions RICE appeared in high RBE and LET at the distal end of beams. Study was limited because of the small sample size and a retrospective cohort.

Authors/Disclosures
Sushant Puri, MBBS (Oregon Health & Science University (OHSU)) PRESENTER	Dr. Puri has nothing to disclose.
Miller Huang, PhD	The institution of Dr. Huang has received research support from NIH.
Sriya Pokala	Mr. Pokala has nothing to disclose.
Anne Li	Ms. Li has nothing to disclose.
Yurika Tarui	Yurika Tarui has nothing to disclose.
Brandi R. Page, MD	Dr. Page has received personal compensation for serving as an employee of Johns Hopkins School of Medicine.
Victoria Croog, MD	Dr. Croog has nothing to disclose.
Kristin Redmond, MD	Dr. Redmond has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for BioMimetix. The institution of Dr. Redmond has received research support from Accuray. The institution of Dr. Redmond has received research support from Canon. The institution of Dr. Redmond has received research support from Icotec. The institution of Dr. Redmond has received research support from GammaTile.
Lawrence Kleinberg, MD	Dr. Kleinberg has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Novocure . Dr. Kleinberg has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Accuray. The institution of Dr. Kleinberg has received research support from Incyte . The institution of Dr. Kleinberg has received research support from BMS . The institution of Dr. Kleinberg has received research support from Novartis .

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