The role of 68Ga-PSMA-I&T PET/CT in the pretreatment staging of primary prostate cancer

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Abstract

Objectives

This retrospective study aimed to evaluate the role of 68Ga-PSMA-I&T PET/CT in the primary staging of newly diagnosed prostate cancer (PCa), with a focus on the detection of metastatic nodal disease. Correlation of the rate of detection of metastatic disease by 68Ga-PSMA-I&T PET/CT with the Gleason score (GS) and serum prostate-specific antigen (PSA) was performed to determine the GS and PSA criteria defining patients who would benefit from 68Ga-PSMA-I&T PET/CT imaging for staging, risk stratification and therapy optimization.

Patients and methods

Patient data and images from 70 patients with a recent diagnosis of prostate cancer who had undergone 68Ga-PSMA-I&T PET/CT were analysed retrospectively. Data and images were analysed for the rate of detection of primary and metastatic PCa, and correlation with PSA and GS.

Results

The rate of detection of primary tumour by 68Ga-PSMA-I&T for patients with serum PSA less than 5 ng/ml was 73%. The corresponding rate was 90% for patients with PSA 5–10 ng/ml and 97% for patients with PSA more than 10 ng/ml. Metastatic PCa and/or infiltrative disease was detected in 24/70 study patients in total: 1/11 patients with PSA less than 5 ng/ml and 23/59 patients with serum PSA at least 5 ng/ml. The rate of detection of metastatic PCa was greater in patients with GS 9 or more (48%) relative to those with GS 8 (32%) or GS ≤7 (18%).

Conclusion

A role for 68Ga-PSMA-I&T PET/CT in primary PCa staging of high-grade disease (GS 8 or more and PSA >10 ng/ml) has been shown. There was a low rate of detection of PSMA-avid metastases in low-grade disease (GS 7 or less and PSA <5 ng/ml), suggesting that there is a limited role for this modality in such cases.

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