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

Objective 177 Lu‐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 177 Lu‐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.