RADT-03. CONTRAST-ENHANCING LESIONS INDUCED BY CNS-DIRECTED INTENSITY MODULATED PROTON THERAPY: DEMOGRAPHIC AND CARDIOVASCULAR RISK FACTORS ANALYSIS

Abstract INTRODUCTION Lesions exhibiting radiation-induced contrast enhancement (RICE) may develop following cranial intensity modulated proton therapy (IMPT). The mechanisms underlying their development may be shared or amplified by existing patient comorbidities. The objective of this study was to assess a potential relationship between individual or composite cardiovascular risk criteria and RICE development, independent of dosimetric considerations. METHODS Data were reviewed for patients treated at a single tertiary care institution between 2017-2023. Time to RICE development was assessed using Kaplan-Meier. Cox regression analysis was used to determine hazard ratios (HRs) with 95% confidence intervals (CIs). Host-related risk factors for RICE development were assessed in a univariable analysis (UVA). A binary logistic regression model was built to ascertain the effects of age and cardiovascular risk factors on the likelihood of developing RICE (expressed as QRISK3 relative risk). RESULTS The study cohort included 137 patients; the median age was 40 years (range: 1-85), 51% female, and 53% Hispanic. Cardiovascular risk factors included smoking (18% past, 6% current), diabetes (7%), hypertension (22%), dyslipidemia (15%) and high body mass index (BMI, 50% were obese with BMI>25). At a median follow-up of 3 years, RICE developed in 36 (26%) patients. On UVA, RICE development was only associated with age ≥18 compared to <18 (HR 3.3, 95% CI: 1.2-9.4, p=0.024). None of the other evaluated risk factors were significantly associated with RICE (p>0.05). Additionally, logistic regression analysis showed increasing age was associated with likelihood of developing RICE (χ2=6.95, p=0.031), while QRISK3 score was not. CONCLUSIONS In this contemporary series of patients treated with IMPT, age was the only host factor associated with RICE, while other cardiovascular risk factors, evaluated individually or using established composite risk scores (QRISK3) were not associated with RICE. Additional research is needed to identify potential patient characteristics associated with RICE.