Head to head comparison performance of 99m Tc-EDDA/HYNIC-iPSMA SPECT/CT and 68 Ga-PSMA-11 PET/CT a prospective study in biochemical recurrence prostate cancer patients.

Positron emission tomography (PET) with prostate-specific membrane antigen (PSMA) has found widespread use for the diagnosis of biochemical recurrence of prostate cancer (PCa). Unfortunately, PET/CT is not as widely available; thus a PSMA-targeting compound for scintigraphy is of special interest. The aim of this study was to compare 99m Tc-EDDA/HYNIC-iPSMA and 68 Ga-PSMA-11 PET/CT qualitatively and semi-quantitatively. Twenty-three patients with metastatic PCa were underwent 99m Tc-EDDA/HYNIC-iPSMA SPECT/CT followed by 68 Ga-PSMA-11 PET/CT. Gleason score in all patients was obtained. Maximal standardized uptake value (SUVmax) and counts per organ, including the primary and metastatic tumor, were normalized and compared using Pearson's correlation test. Sites considered as positive have increased SUVmax and tumor-to-background ratio (TBR) in comparison with non-diseased organs/tissues (SUVmax =25.2±4.7, 18.4±1.6, 11.4±1.2 (P=0.037) from prostate, bone and lymph nodes versus TBR =35.9±45.2, 15.4±18.9, 19.1±51.7 (P=0.035) for prostate, bone and lymph nodes. 99m Tc-HYNIC-iPSMA and 68 Ga-PSMA-11 uptake values in the evaluation of the affected nodes were very similar, although their ranges ranged from 5-21 mm (12±7.6). Correlation coefficient was normalized between SUVmax and TBR, demonstrating r values for prostate of r2 =0.731; for bone of r2 =0.720; and lymph nodes of r2 =0.864 (P<0.05 in all cases). Values and confidence interval at the 95% are supporting the equivalency of both parameters in primary tumor and metastases (prostate 95% CI=4.61, 4.38; bone tissue 95% CI=-2.21, 3.41 and lymph node 95% CI=4.67). We conclude that 68 Ga-PSMA-11 PET/CT and 99m Tc-EDDA/HYNIC-iPSMA SPECT/CT were comparable, supporting the use of 99m Tc-EDDA/HYNIC-iPSMA in patients with progressive metastatic castration-resistant PCa.