Post-Therapeutic Dosimetry of Metastatic Castration-Resistant Prostate Cancer With ¹⁷⁷Lu-PSMA: Experiences From Two University-Based Hospitals in Thailand

Abstract

Objective: 177Lu-PSMA radioligand therapy (RLT) is increasingly used to treat metastatic castration-resistant prostate cancer (mCRPC). Posttreatment dosimetry is essential for assessing normal organ absorbed doses. Therefore, this study aims to evaluate normal organs dosimetry in mCRPC patients undergoing 177Lu-PSMA-RLT from two university-based hospitals in Thailand. Methods: We retrospectively analyzed 61 treatment cycles in 36 patients who underwent posttreatment whole-body planar imaging at three time points (1, 24, and 168 h postadministration). Absorbed doses were computed using organ based MIRD (Medical Internal Radiation Dosimetry) method with OLINDA/EXM v.2.2 in Hermes dosimetry software. Results: The median treated activity was 5.79 GBq (range 5.00–7.29 GBq). Normal organ absorbed doses, from lowest to highest, were red marrow (0.03 ± 0.03 Gy/GBq), total body (0.04 ± 0.03 Gy/GBq), liver (0.13 ± 0.33 Gy/GBq), salivary glands (0.65 ± 0.42 Gy/GBq), and kidneys (0.72 ± 0.36 Gy/GBq). Conclusion: Absorbed doses to normal organs remained within an acceptable range and not exceed the tolerance limits.