PSA-stratified performance of 18F- and 68Ga-labeled tracers in PSMA-PET imaging of patients with biochemical recurrence of prostate cancer

Several studies outlined the sensitivity of (68)Ga-labeled PET tracers against the prostate-specific membrane antigen (PSMA) for localization of relapsed prostate cancer in patients with renewed increase in the prostate-specific antigen (PSA), commonly referred to as biochemical recurrence. Labeling of PSMA tracers with (18)F offers numerous advantages, including improved image resolution, longer half-life and increased production yields. The aim of this study was to assess the PSA-stratified performance of the (18)F-labeled PSMA tracer (18)F-DCFPyL and the (68)Ga-labeled reference (68)Ga-PSMA-HBED-CC.

We examined 191 consecutive patients with biochemical recurrence according to standard acquisition protocols with (18)F-DCFPyL (N = 62, 269.8 MBq, PET scan at 120 minutes p.i.) or (68)Ga-PSMA-HBED-CC (N = 129, 158.9 MBq, 60 minutes p.i.). We determined PSA-stratified sensitivity rates for both tracers and corrected our calculations for Gleason scores using iterative matched-pair analyses. As an orthogonal validation, we directly compared tracer distribution patterns in a separate cohort of 25 patients, sequentially examined with both tracers.

After prostatectomy (N = 106), the sensitivity of both tracers was significantly associated with absolute PSA levels (P = 4.3x10-3). Sensitivity increased abruptly, when PSA values exceeded 0.5µg/L (P = 2.4x10-5). For PSA <3.5µg/L, most relapses were diagnosed at a still limited stage (P = 3.4x10-6). For PSA of 0.5-3.5µg/L, PSA-stratified sensitivity was 88% (15/17) for (18)F-DCFPyL and 66% (23/35) for (68)Ga-PSMA-HBED-CC. This significant difference was preserved in the Gleason-matched-pair analysis. Outside of this range, sensitivity was comparably low (PSA <0.5µg/L) or high (PSA >3.5µg/L). After radiotherapy (N = 85), tracer sensitivity was largely PSA-independent. In the 25 patients examined with both tracers, distribution patterns of (18)F-DCFPyL and (68)Ga-PSMA-HBED-CC were strongly comparable (P = 2.71x10-8). However, in 36% of the PSMA-positive patients we detected additional lesions on the (18)F-DCFPyL scan (P = 3.7x10-2).

Our data suggest that (18)F-DCFPyL is non-inferior to (68)Ga-PSMA-HBED-CC, while offering the advantages of (18)F-labeling. Our results indicate that imaging with (18)F-DCFPyL may even exhibit improved sensitivity in localizing relapsed tumors after prostatectomy for moderately increased PSA levels. Although the standard acquisition protocols, used for (18)F-DCFPyL and (68)Ga-PSMA-HBED-CC in this study, stipulate different activity doses and tracer uptake times after injection, our findings provide a promising rationale for validation of (18)F-DCFPyL in future prospective trials.

Journal of nuclear medicine : official publication, Society of Nuclear Medicine. 2016 Jan 01 [Epub ahead of print]

Felix Dietlein, Carsten Kobe, Stephan Neubauer, Matthias Schmidt, Simone Stockter, Thomas Fischer, Klaus Schomäcker, Axel Heidenreich, Boris D Zlatopolskiy, Bernd Neumaier, Alexander Drzezga, Markus Dietlein

University Hospital of Cologne, Germany., West-German Prostate Center, Germany., University of Cologne, Germany.


Newsletter subscription

Free Daily and Weekly newsletters offered by content of interest

The fields of GU Oncology and Urology are rapidly advancing. Sign up today for articles, videos, conference highlights and abstracts from peer-review publications by disease and condition delivered to your inbox and read on the go.