99mTc-HYNIC-PSMA-11 whole-body SPECT/CT: a clinically viable alternative to 68Ga-PSMA PET/CT in patients with prostate cancer.

OBJECTIVES

The diagnostic performance of 99mTc-HYNIC-PSMA-11 whole-body SPECT/CT versus 68Ga-PSMA PET/CT was evaluated in prostate cancer patients.

METHODS

As a part of the diagnostic workup, all the prostate cancer (PCa) patients (n = 10; mean age 66.4 ± 9.6 years) underwent whole-body 68Ga-PSMA-11 PET/CT followed by serial whole-body (anterior and posterior) 99mTc-HYNIC-PSMA-11 imaging The serial whole-body imaging was performed at multiple time points of 10 minutes, 2 hours, 4 hours, 6 hours, 24 hours and the whole-body SPECT/CT was acquired at 3 hours. The whole-body SPECT/CT data was analysed for lesions detection and to calculate the standardized uptake values (SUVmax) for 99mTc-HYNIC-PSMA-11 avid lesions using the Q-Metrix software. These values were compared with the corresponding SUVmax values obtained from 68Ga-PSMA-11 PET/CT. The serial whole-body imaging data were used for estimating the radiation absorbed doses (mSv/MBq) to various organs using the MIRD schema and the OLINDA/EXM software.

RESULTS

68Ga-PSMA-11 PET/CT identified a total of 64 metastatic lesions, while 99mTc-HYNIC-PSMA-11 SPECT/CT detected 49/64 metastatic lesions, presenting a sensitivity of 76.6%. Notably, the mean SUVmax values for 68Ga-PSMA-11 PET/CT and 99mTc-HYNIC-PSMA-11 were comparable and a highly significant positive correlation (r > 0.93; P < .01) The average absorbed doses to the salivary glands, lungs, kidneys, urinary bladder, and liver were found to be comparable with 99mTc-MDP bone scanning.

CONCLUSIONS

The diagnostic performance of whole-body 99mTc-HYNIC PSMA-11 SPECT/CT is fairly comparable to 68Ga-PSMA PET/CT and offers a favourable dosimetry indicating its potential for PCa evaluation.

ADVANCES IN KNOWLEDGE: 99mTc-PSMA-11 SPECT/CT may be an alternative and cost-effective tool for evaluation of initial PSMA disease burden as well as for response evaluation to PSMA targeted therapies.