patient care perspectives

Newer PET/CT Imaging Techniques Promise to Improve Detection of Metastatic Prostate Cancer

by Peter R. Carroll, MD, MPH, Neal D. Shore, MD, FACS

Overview

The question of defining metastatic disease with available imaging techniques is an important one. Globally, current standard imaging techniques include standard CT with and without contrast, or MRI, and standard Tc-99m bone scans.

 Newer imaging techniques may allow for improved detection of recurrent disease and may better define the metastatic disease state in patients with advanced prostate cancer. Imaging advances, along with expanding science on molecular subsets of disease and rapidly emerging therapies, all promise to reshape the conventional approach to select cases of advanced prostate cancer, lending support to the concept of oligometastatic disease.

Expert Commentary

Peter R. Carroll, MD, MPH

Ken and Donna Derr – Chevron Distinguished Professor
Taube Family Distinguished Professor in Urology
Department of Urology
UCSF – Helen Diller Comprehensive Cancer Center
University of California, San Francisco
San Francisco, CA

This is an area that is moving relatively quickly. We have been doing the gallium PET imaging now for probably 1-2 years here at UCSF, scanning hundreds of people. In my opinion, novel forms of PET imaging will replace the standard imaging. Obviously, we’ll have to get the FDA’s views on this, but it is clear in my mind that there is value.

A flurry of abstracts at the 2017 ASCO-GU reflected the growing interest in these newer imaging techniques, including but not limited to the following:

  • Prostate-specific membrane antigen (PSMA) gallium (68Ga-PSMA)-PET/CT
  • Sodium fluoride (Na/F) PET/CT
  • 18-F DCFBC (a radiolabeled PET agent that binds with high affinity to PSMA) PET/CT
  • Fluciclovine F18 (brand name, Axumin) PET/CT
  • 18F-choline PET/CT
  • C11-choline PET/CT
  • C11-acetate PET/CT
  • Whole-body MRI

Neal D. Shore, MD, FACS

Medical Director and CPI Carolina Urologic Research Center Managing Partner, Atlantic Urology Clinics
Myrtle Beach, SC

Over the years, we have seen fluorodeoxyglucose (FDG)-PET, carbon-11 acetate (C-11 acetate), C-11 choline radiotracers, and Na/F PET scanning, and all of these have demonstrated some improved accuracy in detecting either soft tissue or bone lesions, depending upon their targeted focus.

 Most recently, there has been tremendous interest in gallium PSMA scanning, as well as a new test known as the FACBC (anti-1-amino-3-[18F]fluorocyclobutane-1-carboxylic acid) or Axumin (fluciclovine F 18) test, one that was recently approved in the United States by the FDA.

Peter R. Carroll, MD, MPH

Ken and Donna Derr – Chevron Distinguished Professor
Taube Family Distinguished Professor in Urology
Department of Urology
UCSF – Helen Diller Comprehensive Cancer Center
University of California, San Francisco
San Francisco, CA

Indeed, findings from the CHAPPP study presented at ASCO-GU 2017 suggested that PSMA is more sensitive in the detection of prostate cancer metastases for patients being evaluated for primary treatment or looking for recurrence following local treatment. Results of this study showed clinically meaningful changes in management with avoidance of local treatment because of enhanced detection of metastases.

These newer techniques have also identified isolated pockets of metastatic disease – cases of the so-called oligometastatic disease state – in patients who have rising PSA levels and no lesions identifiable using standard imaging.

 What is remarkable to me is that, using gallium, you’ve identified these patients who have pockets of metastatic disease that are not widely metastatic – again the concept of the oligometastatic state, either lymph nodes or bone. But we have seen some remarkable cases of patients (whom we might have operated on 20 years ago) where PSA rises but we can’t find the disease with standard imaging. We perform a gallium PET and find that the patient has a mediastinal lymph node. We can target that.

 Best practices for the use of newer imaging techniques continue to be developed and defined as experience expands. Fakhrejahani and colleagues, for instance, presented findings at ASCO-GU 2017 from their study comparing the uptake of DCFBC in bone with NaF PET/CT in metastatic prostate cancer patients. DCFBC had added capability to detect soft tissue metastasis, whereas NaF was confined to secondary effects of bone disease. The group found that DCFBC uptake in bone metastasis does not routinely correspond to focal NaF uptake, leading them to believe that distinct mechanisms of tracer uptake and tumor biology may be in play. There was an inverse association in focal bone findings when comparing each tracer on antiandrogen therapy.

References

Fakhrejahani F, Lindenberg ML, Bargvall ES, et al. Imaging metastatic prostate cancer with 18F-DCFBC PET/CT (DCFBC) and 18F-NaF PET/CT (NaF). J Clin Oncol. 2017;35(suppl 6S; abstract 231).

Jadvar H. Prognostic utility of PET in prostate cancer. PET Clinics. 2015;10(2):255-263.

Rieves D, Jacobs P. The use of published clinical study reports to support U.S. Food and Drug Administration approval of imaging agents. J Nucl Med. 2016 Dec;57(12):2022-2026.

Schmidt A, Goh JC, Bhatt M, et al. The CHAPPP study: Changing care with PSMA-PET for prostate cancer – a retrospective study of the role of PSMA imaging in altering treatment pathways. J Clin Oncol. 2017;35(suppl 6S; abstract 13).

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