The promising role of PSMA-PET CT scan for patients diagnosed with prostate cancer

(UroToday.com) Most of Thursday’s “Advances in Prostate Cancer Diagnosis” session of the Society of Urologic Oncology (SUO) Annual Meeting 2020 was devoted to imaging with a strong focus on membrane antigen specific prostate (PSMA). The United States Food and Drug Administration (FDA) has approved Gallium 68 PSMA-11 as the first PET imaging drug that uses a prostate-specific membrane antigen tracer for men with prostate cancer. The tracer was specifically approved in the context of suspected prostate cancer metastases.

Dr. Declan Murphy’s talk began with a brief description of the history of PSMA, noting that interest dates back to 2014, when we began seeing compelling cases of PSMA imaging detecting otherwise occult sites of extraprostatic disease. He then spent the rest of the time reviewing the recent proPSMA study results, PET-CT-specific prostate membrane antigen in patients with high-risk prostate cancer before surgery or radiotherapy (proPSMA) with curative intent: a prospective, randomized, multicentre study.

The proPSMA study was published last spring in The Lancet ¹ and is a multicenter, two-arm, randomized study in Australia investigating the role of PSMA in the newly diagnosed high-risk prostate cancer patient. The study was initially launched in 2017, with an outline as shown below (Figure 1). Patients with biopsy-proven high-risk prostate cancer were randomized to conventional imaging or PSMA-PET. As long as fewer than 3 metastatic lesions were identified, the participants crossovered and imaged using the other modality. At each point, diagnosis, first imaging and second imaging, the treatment plan was recorded.

Figure 1:

The main outcome of the study was the accuracy of first-line imaging for pelvic nodal or distant metastatic disease at 6 months. Extraprostatic disease was defined by a predefined reference standard that included histopathology and / or changes in imaging and biochemistry at follow-up. In their cohort, 30% of patients had evidence of extraprostatic disease and within the patient population PSMA PET was 27% more accurate than conventional imaging (Figure 2). Subgroup analysis found that this was true for both nodal and distant disease.

Figure 2:

Next, Dr. Murphy looked at the numerous secondary outcomes (Figure 3). The PSMA had a major impact on the change in the management plan in both the first and second lines. In particular, when conventional imaging followed PSMA, little additional information was obtained. This was in direct opposition to when PSMA followed conventional imaging, where a change in management plan occurred 27% of the time. In addition, the PSMA reduced the number of ambiguous studies, improved agreement among reporters, and reduced patients’ radiation exposure.

Concluding his talk, Dr. Murphy highlighted the promising role he believes PSMA-PET CT will play in the future for patients diagnosed with prostate cancer, while acknowledging the need for long-term cancer outcome studies.

Presented by: Declan Murphy, MB, BCH, BaO, FRACS, FRCS, Urol, Professor, Consultant Urological Surgeon at Peter MacCallum Cancer Center and Royal Melbourne Hospital, Melbourne, Australia and Director of Outcome Research at Australian Prostate Cancer Research Center.

Written by: Adrien Bernstein, MD, Society of Urologic Oncology Fellow, Fox Chase Cancer Center, Fox Chase Cancer Center, Philadelphia, PA, at the 21st Annual Meeting of the Society of Urologic Oncology (SUO), December 3-5, virtual conference

References:

1. Hofman MS, Lawrentschuk N, Francis, RJ, et al. PET-CT-specific prostate membrane antigen in patients with high-risk prostate cancer prior to surgery or radiotherapy (proPSMA) with curative intent: a prospective, randomized, multicenter study. Lancet 2020 April 11; 395 (10231): 1208-1216.

Relative content:
PSMA PET / CT Imaging for Staging High-Risk Prostate Cancer Before Surgery or Curative Radiation Therapy (proPSMA) – Michael Hofman and Declan Murphy
The Lancet Abstract: PET-CT of prostate-specific membrane antigen in patients with high-risk prostate cancer before surgery or radiotherapy (proPSMA): a prospective, randomized, multicenter study