Main Session
Sep
29
PQA 06 - Radiation and Cancer Biology, Health Care Access and Engagement
3033 - Correlation between Linear Energy Transfer and Adverse Events in Intensity-Modulated Proton Therapy
Presenter(s)
Daniela Branco, PhD, MS - University of California at San Diego, La Jolla, CA
D. Branco1,2, V. Moiseenko2, P. Sanghvi2, I. MacEwan1,2, J. J. Urbanic1,2, J. A. Hattangadi-Gluth2, and C. Chang1,2; 1California Protons Cancer Therapy Center, San Diego, CA, 2Department of Radiation Medicine and Applied Sciences, University of California San Diego, La Jolla, CA
Purpose/Objective(s):
High Linear Energy Transfer (LET) in proton therapy may lead to unexpected adverse events despite adherence to standard Organ-at-Risk (OAR) dose constraints. This study aimed to investigate the relationship between LET distribution and clinically observed adverse events in patients treated with Intensity-Modulated Proton Therapy (IMPT).Materials/Methods:
Sixteen patients treated with IMPT between 2019-2022 for various cancer sites (prostate, base of tongue, nasal cavity, esophagus, glioma, and liver) who experienced adverse events were retrospectively analyzed. All treatment plans had met institutional OAR dose constraints. Monte Carlo simulations were performed to calculate LET distributions throughout the treatment volumes. Regions of high LET (6-8 keV/µm) and intermediate LET (3-5 keV/µm) were correlated with high-dose regions (=80% of prescription dose) and mapped against the locations of clinically observed adverse events, which included radiation necrosis, gastrointestinal bleeding, trismus, fistulas, and ulcers.Results:
Only one case demonstrated overlap between high LET (6-8 keV/µm) and high-dose regions that correlated with gastrointestinal bleeding. However, all 16 cases (100%) exhibited overlap between intermediate LET values (3-5 keV/µm) and high-dose regions.Conclusion:
This preliminary analysis suggests that even intermediate LET values (3-5 keV/µm), when combined with high doses, may be associated with unexpected adverse events in proton therapy. While high LET regions (>6 keV/µm) remain a concern, the prevalence of intermediate LET associations warrants further investigation. Future work will include specific contouring of affected tissues to enable precise spatial correlation between LET distributions and adverse events.