Day-to-day variability of [68Ga]Ga-PSMA-11 accumulation in primary prostate cancer: effects on tracer uptake and visual interpretation

Judith Olde Heuvel,Cornelis H Slump,Maarten L Donswijk,Berlinda J De Wit-Van Der Veen,Marcel P M Stokkel

doi:10.1186/s13550-020-00708-z

Judith Olde Heuvel, Cornelis H Slump + Show 3 more

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https://doi.org/10.1186/s13550-020-00708-z

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Abstract

PurposeProstate-specific membrane antigen (PSMA) agents, such as [68Ga]Ga-PSMA-11, have an unprecedented accuracy in staging prostate cancer (PCa) and detecting disease recurrence. PSMA PET/CT may also be used for response monitoring by displaying molecular changes, instead of morphological changes alone. However, there are still limited data available on the variability in biodistribution and intra-prostatic uptake of PSMA targeting radiotracers. Therefore, the aim of this study was to assess the repeatability of [68Ga]Ga-PSMA-11 uptake in primary PCa patients in a 4-week interval.MethodsTwenty-four primary PCa patients were prospectively included, who already were scheduled for [68Ga]Ga-PSMA-11 PET/CT scan on clinical indication (≥ cT3, Gleason score ≥ 7 or PSA ≥ 20 ng/mL). These patients received two [68Ga]Ga-PSMA-11 PET/CT scans with a 4-week interval. No treatment was started in between the scans. Semiquantitative measurements (SULmax, SULmean, and SULpeak) were determined in the prostate tumor, normal tissues, and blood pool. The repeatability coefficient of every region was determined. All scans were visually analyzed by two nuclear medicine physicians.ResultsWithin-subject coefficient of variation of [68Ga]Ga-PSMA-11 uptake between the two scans was on average 10% in the prostate tumor, normal tissues (liver, kidney, parotid), and blood pool. The repeatability coefficient of the prostate tumor was 18% for SULpeak and 22% for SULmax. Lesion uptake was visually different in 5 patients, though not clinically relevant.ConclusionResults of test-retest [68Ga]Ga-PSMA-11 PET/CT scans in a 4-week interval show that [68Ga]Ga-PSMA-11 uptake is repeatable, with a clinical irrelevant variation in tumor and physiological distribution. Based on the presented repeatable uptake, [68Ga]Ga-PSMA-11 PET/CT scans can potentially be used for disease surveillance and therapy response monitoring. Changes in uptake larger than the RC are therefore likely to reflect actual biological changes in PSMA expression.Trial registration NL8263 at Trialregister.nl retrospectively registered on 03-01-2020. https://www.trialregister.nl/trial/8263

Highlights

Prostate cancer (PCa) is the second most common cancer amongst men in the world, as recorded in 2018 [1]
Based on the pre‐ sented repeatable uptake, [68Ga]Ga-prostate-specific membrane antigen (PSMA)-11 Positron emis‐ sion tomography (PET)/Computed tomography (CT) scans can potentially be used for disease surveillance and therapy response monitoring
Molecular imaging of this malignancy either in primary or metastatic setting is presently dominated by the olde Heuvel et al EJNMMI Res (2020) 10:132 ligands directed to the prostate-specific membrane antigen (PSMA)

Summary

Introduction

Prostate cancer (PCa) is the second most common cancer amongst men in the world, as recorded in 2018 [1] Molecular imaging of this malignancy either in primary or metastatic setting is presently dominated by the olde Heuvel et al EJNMMI Res (2020) 10:132 ligands directed to the prostate-specific membrane antigen (PSMA). This is a membrane-bound enzyme which is overexpressed in PCa cells compared to benign prostatic tissue by approximately 100- to 1000-fold [2, 3]. [18F]FDG PET/CT is usually not suitable in PCa, as most tumors show limited FDG-accumulation, especially in hormonesensitive setting

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