Comparison of ^99mTc-HYNIC-PSMA-11, bone scan and post radioligand therapy images in mCRPC patients: A single center...

Prostate-Specific Membrane Antigen is overexpressed in primary and metastatic prostate cancer tissues. While PSMA PET agents have gained their role in the prostate cancer guidelines, Technetium-based PSMA agents have left behind. Given the novelty of ^99mTc-HYNIC-PSMA-11, we conducted this study to compare its detection rate in tracing skeletal metastases in comparison to bone scans and also compared the number of metastatic lesions which showed PSMA uptake in the diagnostic scan with those detected in post-treatment scans after radioligand therapy (RLT) with ¹⁷⁷Lu-PSMA-617-617.

Bone and ^99mTc-HYNIC-PSMA-11 scans with a maximum interval of 90 days were performed in thirty-nine patients with widespread bone metastases. If the PSMA scan was positive, patients were treated with ¹⁷⁷Lu-PSMA-617 and post treatment scan was also obtained. For negative PSMA results, ⁶⁸Ga-PSMA PET/CT was performed to compare its results with the bone scan. In patients with PSMA expression, detection of metastatic lesions in three consecutive whole-body scans in different regions were compared (^99mTc-HYNIC-PSMA-11 with bone and post treatment scans, separately).

37 (94.9%) showed adequate ^99mTc-HYNIC-PSMA-11 uptake in the metastatic regions. Compared to bone scan, ^99mTc-HYNIC-PSMA-11 showed additional lesions in 13 (35.1%) participants which were mostly located in the appendicular skeleton and pelvic bones. Inversely, the bone scan detected more lesions in 12 (32.4%) patients. Both scans in 12 (32.4%) patients showed the exact same results. Comparison between the ^99mTc-HYNIC-PSMA-11 scan and ¹⁷⁷Lu-PSMA-617 showed completely similar results in 29 (78.4%) patients; however, ¹⁷⁷Lu-PSMA-617 detected more lesions in eight (21.6%) participants.

The ^99mTc-HYNIC-PSMA-11 scan demonstrates comparable results to bone scans in evaluating skeletal metastases in prostate cancer patients. It serves as a cost-effective modality for identifying suitable candidates for radioligand therapy, particularly beneficial in resource-limited countries.