Gallium-68 (Ga-68)-prostate-specific membrane antigen (PSMA)-11 PET/CT can reduce the need for biopsies in men with suspected high-risk prostate cancer, according to a study published June 10 in Lancet Oncology.
The finding is from a multicenter phase III trial (PRIMARY2) that enrolled 660 biopsy-naïve men across seven Australian hospitals who had non-suspicious MRI scans but high clinical risk, noted lead author James Buteau, MD, of the Peter MacCallum Cancer Centre in Melbourne, Australia, and colleagues.
"The addition of PSMA-PET to non-suspicious MRI with high clinical risk or equivocal MRI halved the number of men requiring biopsy without reducing the detection of clinically significant malignancy," the group wrote.
Prostate MRI has become the standard of care in men with suspected prostate cancer. In those with equivocal or non-suspicious MRI findings but high clinical risk -- defined by factors including prostate specific antigen (PSA) above 0.1 ng/mL/mL, or a family history of disease, for instance -- invasive biopsies are performed. Yet most of these men are found on biopsy to have either no cancer or clinically insignificant disease, the authors noted.
Ga-68 PSMA-11 PET/CT is approved and widely used for staging people with intermediate-risk to high-risk disease, biochemical recurrence, as well as for determining patient eligibility before lutetium-177 PSMA radioligand therapy, the authors added. Therefore, in this study, the group investigated whether the scans could reduce the number of people requiring biopsy without compromising diagnosis.
Among the 660 participants, the median age was 61 years old, median PSA was 5.2 ng/mL, and median PSA density was 0.13 ng/mL/mL. There were PI-RADS 2 categories in 335 (51%) participants and PI-RADS 3 in 325 (49%) participants. The researchers randomly assigned 329 (50%) to a control group with systematic transperineal prostate biopsy, and 331 (50%) to an experimental group with Ga-68 PSMA-11 PET/CT.
According to the analysis, the proportion of participants with clinically significant prostate cancer in the experimental group (39 of 331 [12%]) was noninferior to the control (51 of 329 [16%]). The use of Ga-68 PSMA-11 PET/CT avoided biopsy in 163 (49%) of 331 participants (p < 0.0001), the researchers reported.
“The PRIMARY2 trial is the first randomized trial to our knowledge to show that the addition of Ga-68 PSMA-11 PET/CT to MRI in these men halves the number of men requiring prostate biopsy without compromising the detection of clinically significant malignancy,” the group wrote.
In addition, Ga-68 PSMA-11 PET/CT cut the detection of clinically insignificant malignancies from 32% in the systematic biopsy group to 14%, which the authors described as a clinically meaningful outcome.
“Addressing the overtreatment of men with clinically insignificant cancer is still a major unmet need in prostate cancer, and even if they are safely on active surveillance, this can be a source of anxiety for men and require substantial resources over time,” the researchers wrote.
Follow-up is ongoing, with full two-year outcomes and health economic analyses planned, they noted.
"Future work should consider the cost-effectiveness of incorporating Ga-68 PSMA-11 PET/CT into the prostate cancer diagnostic pathway," the team concluded.
The full study is available here.
