TAT-11: Small Scale Modeling and Dosimetry for the Salivary Gland: Application to 177Lu- and Ac-225-PSMA Therapy

Ottawa, ON, Canada (UroToday.com) Xerostomia is a serious side effect in Lu177-PSMA and Ac225-PMSA treatment of metastatic castration-resistant prostate cancer. This has been somewhat puzzling since the damage seems disproportionate to the salivary gland absorbed dose, even considering the higher RBE of alpha radiation. Dr. Hobbs reported on a Monte Carlo study to understand the micro-distribution within the salivary glands. Most of the radioactive uptake occur striated epithelialization ducts where PSMA is expressed. The geometry of these ducts was taken from the literature and input to the GEANT4 Monte Carlo program as elements of spheres of various sizes to mimic the salivary glands as a whole. Lu177 and Ac225 were modeled and doses calculated for both the ducts and the spheres as a whole. They found a ratio of duct to the whole gland absorbed a dose of 5.1 – 5.3 for 177Lu and 13.4 – 13.8 for 225Ac.

Presented by: Robert Hobbs, PhD, Johns Hopkins University, Baltimore, Maryland

Written by: William Carithers, Lawrence Berkeley National Laboratory at the 11th International Symposium on Targeted Alpha Therapy (TAT-10) April 1 - April 4, 2019 - Ottawa, ON, Canada

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