Prostate cancer biochemical recurrence occurs in 20 to 80 percent of patients within 10 years after radical prostatectomy and is difficult to treat. Salvage radiotherapy is the main option for treatment, but the imaging modalities currently used are not sensitive enough to identify the location of recurrence until it is too late, leading to a “best-guess” approach for targeting the radiotherapy.
“Based on European data, we believe that PSMA PET/CT, an imaging technique that is not yet approved by the U.S. Food and Drug Administration, is sufficiently sensitive to detect and localize the recurrent prostate cancer early enough to potentially guide salvage radiotherapy,” explains Jeremie Calais, MD, at UCLA. “The first sign of prostate cancer recurrence is a rising PSA. For salvage radiotherapy to be successful, it should be initiated before the PSA rises above 1 ng/mL, and ideally, closer to 0.2 ng/mL or lower.”The study included 270 well-documented patients from databases established at four institutions (UCLA and three in Germany: Technical University of Munich, Ludwig-Maximilians-University of Munich, and University of Essen). All patients had a biochemical recurrence of prostate cancer after radical prostatectomy but had not received prior radiotherapy. They underwent PSMA PET/CT at a serum PSA level of less than 1 ng/ml.
Nearly half (132 patients or 49 percent) had a positive PSMA PET/CT, and 52 (19 percent) had at least one PSMA-positive lesion that was not covered by the consensus clinical target volume (CTV). The two most common PSMA PET–positive lesion locations outside the consensus radiation fields were bone (23/52, 44 percent) and perirectal lymph nodes (16/52, 31 percent).
Calais points out, “Salvage radiotherapy is only curative if recurrent disease is completely encompassed by the radiotherapy fields. Therefore, in almost 20 percent of these patients, the addition of PSMA PET/CT would have a potentially major impact on the outcome of salvage radiotherapy.”
He elaborates, “Visualizing sites of prostate cancer recurrence accurately, and early enough to guide therapy, enables truly precision radiation therapy. This is, in fact, the definition of individualized medicine. We believe that PSMA PET/CT imaging will ultimately be incorporated into the standard of care for prostate cancer patients with biochemical recurrence.”
Toward that end, the suggested next step is a randomized imaging trial of salvage radiotherapy with or without PSMA PET/CT to investigate further its potential beneficial impact on treatment outcome.
FIGURE: A 3-dimensional map of the PSMA–positive lesions outside the standard radiation fields.
This is a 3-dimensional map of the PSMA–positive lesions (yellow) of all 52 patients with recurrence outside consensus CTVs (23 patients with recurrence outside only and 29 patients with recurrence outside and inside consensus CTVs), created by rigid registration of each patient’s CT image to template patient’s CT image, followed by transfer of each PSMA–positive lesion contour to template patient CT image (MIM, version 6.7.5; MIM Software Inc.). On right side, 3-dimensional prostate bed consensus radiation fields is shown in orange and 3-dimensional pelvic LN consensus radiation fields in green. Credit: Jeremie Calais, Nicholas G. Nickols et al., UCLA, Los Angeles, Calif.
J Nucl Med February 1, 2018 vol. 59 no. 2 230-237
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Written By:
Jeremie Calais1, Johannes Czernin1, Minsong Cao1, Amar U. Kishan1, John V. Hegde1, Narek Shaverdian1, Kiri Sandler1, Fang-I Chu1, Chris R. King1, Michael L1 , Steinberg and Francesco Ceci1 , Isabel Rauscher2 Nina-Sophie Schmidt-Hegemann3, Thorsten Poeppel4 , Philipp Hetkamp4, Ken Herrmann5, Wolfgang P. Fendler6, Matthias Eiber7, and Nicholas G. Nickols8
Author Affiliation:
1. UCLA, Los Angeles, California
2. Technical University of Munich, Munich, Germany
3. University Hospital, LMU Munich, Munich, Germany
4. Universitätsklinikum Essen, Essen, Germany
5. UCLA and Universitätsklinikum Essen
6. UCLA and Ludwig-Maximilians-University, Munich, Germany
7. UCLA and Technical University of Munich
8. UCLA and VA Greater Los Angeles Healthcare System, Los Angeles, Calif.