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San Diego, CA. USA (UroToday.com) – Newer and more sensitive radioligands are available for imaging PSMA to detect prostate cancer recurrence and metastasis upon biochemical relapse. Ga-68 labeled PSMA-HBED-CC (or Ga-PMSA-11) is a Ga-68 labeled monoclonal antibody against PMSA while F-18 DCFPyL is a small molecule with high affinity to PSMA at nanomolar range. Both are investigational radiopharmaceuticals with high PSMA-affinity that hold great potential for clinical use. They may be able to provide early diagnostic information for possible curative treatment of recurrent prostate cancers that are limited to the prostate fossa and regional lymph nodes.
This study is to investigate the ability of F-18 DCFPyL to detect recurrent prostate cancer and metastasis in contrast to that of published data of Ga-68 PSMA-HBED-CC.
Alexander E. Drzezga MD from University of Cologne, Cologne, Germany presented new data at the 2016 Society of Nuclear Medicine and Molecular Imaging annual meeting.
WHY: the question is whether PET-CT using newer radioligands of PSMA can detect recurrent disease in post-prostatectomy patients earlier during biochemical relapse when PSA is close to the detection limit of 0.5 ng/ml.
WHAT: 55 of 131 patients who underwent F-18 DCFPyL PET-CT had elevated PSA (0.2-140 ng/ml) after prostatectomy. 39/55 patients had PSMA-positive lesions in the prostate fossa (25%), lymph nodes (42%) and bones (20%). Detection of PSMA-positivity was 45% versus 80% for PSA<1 and PSA>1 respectively.
Further analysis at different range of PSA indicate that the lesion detection rate was 12%, 88% and 83% for serum level of PSA<0.5, 0.5<PSA<3.5 and PSA>3.5, respectively. When compared with data from co-author Dietlein M et al, the detection rate from PET-CT using Ga-68 PSMA-HBED-CC are 11%, 66% and 91%, respectively. The authors conclude that F-18 DCFPyL PET-CT has superior performance to detect PSMA-positive lesion for biochemical relapse with PSA between 0.5-3.5 ng/ml which is relatively low and close to detection limits. Therefore, F-18 DCFPyL PET-CT may be more effective in assisting therapeutic decisions with earlier biochemical relapse.
PSMA-imaging radiopharmaceuticals are becoming available and may provide sensitive detection of recurrent prostate cancer to allow early detection and to assist decisions on curative treatment planning. Prostate cancer patients will certainly benefit when these findings are further confirmed by larger well-controlled trials and when these radiopharmaceuticals gain regulatory approval for clinical use.
A missing link in this study is the histopathologic confirmation of PSMA-positive lesions. However, other abstracts in this meeting such as Abstract #565 on correlation between histopathology and PET-MRI of prostate cancer using Ga-68 PSMA-HBED-CC have filled that gap.
Presented by: Alexander E. Drzezga MD at the 2016 Society of Nuclear Medicine and Molecular Imaging annual meeting in San Diego, CA, USA. Abstract #561.
Written By: Franklin C. Wong, MD PhD JD, Professor of Nuclear Medicine and Neuro Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, USA