Abstract
PurposeSince the introduction of PSMA PET/CT with 68Ga-PSMA-11, this modality for imaging prostate cancer (PC) has spread worldwide. Preclinical studies have demonstrated that short-term androgen deprivation therapy (ADT) can significantly increase PSMA expression on PC cells. Additionally, retrospective clinical data in large patient cohorts suggest a positive association between ongoing ADT and a pathological PSMA PET/CT scan. The present evaluation was conducted to further analyse the influence of long-term ADT on PSMA PET/CT findings.MethodsA retrospective analysis was performed of all 1,704 patients who underwent a 68Ga-PSMA-11 PET/CT scan at our institution from 2011 to 2017 to detect PC. Of 306 patients scanned at least twice, 10 had started and continued ADT with a continuous clinical response between the two PSMA PET/CT scans. These ten patients were included in the current analysis which compared the tracer uptake intensity and volume of PC lesions on PSMA PET/CT before and during ongoing ADT.ResultsOverall, 31 PC lesions were visible in all ten patients before initiation of ADT. However, during ongoing ADT (duration 42–369 days, median 230 days), only 14 lesions were visible in eight of the ten patients. The average tracer uptake values decreased in 71% and increased in 12.9% of the PC lesions. Of all lesions, 33.3% were still visible in six patients with a complete PSA response (≤0.1 ng/ml).ConclusionContinuous long-term ADT significantly reduces the visibility of castration-sensitive PC on PSMA PET/CT. If the objective is visualization of the maximum possible extent of disease, we recommend referring patients for PSMA PET/CT before starting ADT.
Highlights
Materials and methodsThe detection of recurrent prostate cancer (PC) has always been challenging using conventional imaging modalities such as computed tomography (CT) and magnetic resonance imaging
31 PC lesions were visible in ten patients on the positron emission tomography (PET)/CT scan before initiation of androgen deprivation therapy (ADT)
Multivariate analyses including larger patient cohorts with prostate-specific membrane antigen (PSMA) ligand PET/CT published so far [6, 7] suggest that 68Ga-PSMA-11 PET/CT significantly more often shows pathological findings in patients receiving ADT
Summary
The detection of recurrent prostate cancer (PC) has always been challenging using conventional imaging modalities such as computed tomography (CT) and magnetic resonance imaging. There has been a need for new imaging tools with improved sensitivity and specificity in diagnosis. In this context, nuclear imaging targeting prostate-specific membrane antigen (PSMA) has received increased attention. Positron emission tomography (PET) using 68Ga-PSMA-11 and alternative PSMA ligands has been regarded as a significant step forward in the diagnosis of recurrent PC. The first studies indicated that this novel method is superior to alternative imaging modalities used for the detection of recurrent PC [4,5,6]. Later studies including larger patient cohorts confirmed the high sensitivity and specificity of 68Ga-PSMA11 PET/CT [7,8,9,10]
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