Intra-individual comparison of 68Ga-PSMA-11 and 18F-DCFPyL normal-organ biodistribution

Abstract

Purpose Detailed data comparing the biodistribution of PSMA radioligands is still scarce, raising concerns regarding the comparability of different compounds. We investigated differences in normal-organ biodistribution and uptake variability between the two most commonly PSMA tracers in clinical use, 68 Ga-PSMA-11 and 18 F-DCFPyL. Methods This retrospective analysis included 34 patients with low tumor burden referred for PET/CT imaging with 68 Ga-PSMA-11 and subsequently 18 F-DCFPyL. Images were acquired with 4 cross-calibrated PET/CT systems. Volumes of interest were placed on major salivary and lacrimal glands, liver, spleen, duodenum, kidneys, bladder, blood-pool and muscle. Normal-organ biodistribution of both tracers was then quantified as SUV peak and compared using paired tests, linear regression and Bland-Altman analysis. Between-patient variability was also assessed. Clinical and protocol variables were investigated for possible interference. Results For both tracers the highest uptake was found in the kidneys and bladder and low background activity was noted across all scans. In the quantitative analysis there was significantly higher uptake of 68 Ga-PSMA-11 in the kidneys, spleen and major salivary glands ( p < 0.001), while the liver exhibited slightly higher 18 F-DCFPyL uptake ( p = 0.001, mean bias 0.79 ± 1.30). The lowest solid-organ uptake variability was found in the liver (COV 21.9% for 68 Ga-PSMA-11, 22.5% for 18 F-DCFPyL). There was a weak correlation between 18 F-DCFPyL uptake time and liver SUV peak (r = 0.488, p = 0.003) and, accordingly, patients scanned at later time-points had a larger mean bias between the two tracers’ liver uptake values (0.05 vs 1.46, p = 0.001). Conclusion Normal tissue biodistribution patterns of 68 Ga-PSMA-11 and 18 F-DCFPyL were similar, despite subtle differences in quantitative values. Liver uptake showed an acceptable intra-patient agreement and low inter-patient variability between the two tracers, allowing its use as a reference organ for thresholding scans in the qualitative comparison of PSMA expression using these different tracers. Electronic supplementary material The online version of this article (10.1186/s40644-019-0211-y) contains supplementary material, which is available to authorized users.

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

“…Previous studies looked at metastatic patients or [ 18 F]DCFPyL instead of [ 68 Ga]Ga-PSMA-11. Given the similar bio-distribution, findings for [ 68 Ga]Ga-PSMA-11 may probably be generalized to [ 18 F]DCFPyL [ 22 ]. Noteworthy is that [ 18 F]PSMA-1007 has a distinctly different bio-distribution than the latter radiotracers [ 23 ].…”

Prostate Cancer Theranostics - An Overview

“…Multiple doses of Fluorine-18 radiolabeled inhibitor are available at institutions with a medical cyclotron, with the ability to ship agent at greater distances. Lower upfront costs are required for Gallium-68 isolation on a 68 Ge/ 68 Ga generator system, however fewer doses are produced with lower specific activity, and decreased resolution (46)(47)(48)(49).…”

Robotic surgery using a DROP-IN beta probe – feasibility study with 68Ga-PSMA in prostate cancer specimens

“…These patients were mostly redirected to our clinical institute for prostate cancer treatment, while diagnostics was performed at the referring hospital. Therefore, based on local availability and preferences, diagnostic PSMA-PET/CT was performed with 18 F labelled PSMA. This should however provide comparable uptake as 68 Ga-PSMA-11 (18).…”

“…Therefore, based on local availability and preferences, diagnostic PSMA-PET/CT was performed with 18 F labelled PSMA. This should however provide comparable uptake as 68 Ga-PSMA-11 (18). SUV mean measurements were performed using OsiriX medical imaging software (Pixmeo SARL).…”