68Ga-PSMA-11 PET imaging triggers major changes in management of biochemically recurrent prostate cancer

Justin Ferdinandus, MD

Imaging with ⁶⁸Ga-PSMA-11 PET led to major management changes in patients with biochemically recurrent prostate cancer, according to findings from a prospective, single-arm trial presented during the 2020 European Association of Urology Virtual Congress.

In a cohort of 136 patients, referring physicians implemented recommended management changes in 72% (n = 98) of patients. ⁶⁸Ga-PSMA-11 PET also led to the prevention of unnecessary diagnostic tests and a decline in the proportion of patients with unknown sites of disease.

“We [observed] high rates of altered management in patients receiving PSMA PET for biochemical recurrence, justifying its implementation in clinical practice,” said lead study author Justin Ferdinandus, MD, department of Nuclear Medicine, University Hospital Essen, Essen Germany.

The study included patients with prostate adenocarcinoma and biochemical recurrence who were recruited at the University of California, Los Angeles and the University of California, San Francisco. Recurrence was defined as a PSA level of ≥0.2 ng mL at more than 6 weeks following prostatectomy or a PSA increase of ≥2 ng/mL above nadir following radiation therapy. The imaging results were interpreted using an image-based TNM staging system (PROMISE).

The study consisted of 3 questionnaires completed by the treating physicians: a pre-PET questionnaire completed upon the patient being scheduled for PSMA PET; a post-PET questionnaire completed when the PSMA PET report was received; and a 3- to 6-month follow-up questionnaire filled out by the referring physician inquiring whether the intended management was implemented.

Overall, 635 patients were initially recruited; however, after excluding patients who were missing the pre- and/or post-PET questionnaires, the remaining “intended” management population consisted of 382 patients. Almost half of these patients were then missing the questionnaire from the referring physician, leaving an “implemented” management population of 206 patients.

Across the intended and implemented cohorts, the median age was 70.1 years (range 43.8 to 95.3). In the 382-patient intended cohort, the median PSA was 1.86. Regarding Gleason score, 62% had a score <8, 29% had a score ≥8 and data were missing for 9%.Initial therapy in this cohort was prostatectomy only (44%), radiotherapy only (26%), and prostatectomy plus salvage radiotherapy (30%). Other prior treatments included androgen-deprivation therapy (38%), local salvage therapy (15%), abiraterone acetate or enzalutamide (3%), chemotherapy (3%), and bone-targeted treatment (1%).

The median PSA in implemented cohort was 1.75 ng mL. Regarding Gleason score, 61% had a score <8, 30% had a score ≥8 and data were missing for 9%.Initial therapy in this cohort was prostatectomy only (42%), radiotherapy only (24%), or prostatectomy plus salvage radiotherapy (34%). Other prior treatments included androgen-deprivation therapy (39%), local salvage therapy (9%), abiraterone acetate or enzalutamide (2%), and chemotherapy (1%).

In the intended cohort, there was an intended management change in 68% of the patients, with the intended change being considered “major” in 46% of the patients. Overall, 150 diagnostic tests were prevented, comprising mostly CT (n = 43) and bone scans (n =52); however, ⁶⁸Ga-PSMA-11 PET results did trigger 73 tests per the study protocol. Over half (n = 44) of these tests were biopsies. The imaging outcomes also lead to a decline from 68% to 29% in the proportion of patients with unknown sites of disease.

For the intended management cohort, management pathway recommendations “predominantly aligned with PSMA PET disease stages: focal or salvage therapy for local disease, and systemic treatment for distant metastases,” said Ferdinandus.

For patients with unknown disease site, it was recommended that 47% change toward active surveillance; for patients with locoregional disease, it was recommended that 56% change toward local/focal therapy; for patients with metastatic disease, it was recommended that 69% of patients with M1a and 43% of patients with M1bc change toward systemic therapy.

The 206-patient implementation cohort included 136 patients for whom changes were intended and 70 patients for whom changes were not intended. For the first group, the referring physician survey results showed that 72% of the changes were implemented. In the “no-change” intended population, the referring physician followed the recommendation in 89% of the patients.

Regarding next steps, Ferdinandus said, “Future randomized trials need to evaluate the impact of management changes on oncologic outcomes.”

Reference

Ferdinandus J, Fendler WP, Calais J, et al. Impact of ⁶⁸Ga-PSMA-11 PET on the management of biochemically recurrent prostate cancer in a prospective single-arm clinical trial. 2020 European Association of Urology Virtual Congress. July 17-26, 2020. Abstract 800.

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