Katie Robinson

A study presented at the Radiological Society of North America (RSNA) 2022 Annual Meeting showed that compared with prostate-specific antigen (PSA)-based screening for prostate cancer, the use of biparametric prostate magnetic resonance imaging (MRI) could potentially reduce unnecessary biopsies without increasing the risk of underdiagnosis.

Beyond the clinical benefit, a simplified cost-effectiveness analysis found that “despite the high cost, MRI was expected to reduce unnecessary costs for prostate cancer diagnosis," according to the authors.

“MRI-based screening showed lower proportions of screening-positive cases, lower false positive rates, and higher PPVs [positive predictive values] than those of PSA-based screening,” noted Taek Min Kim, MD, an assistant professor in the Department of Radiology at Seoul National University Hospital in Seoul, Korea, and colleagues.

While the PSA test is utilized for prostate cancer screening, Kim and colleagues maintained that questions linger about the evidence of the test’s benefits and risks. Accordingly, the researchers compared the performance of biparametric prostate MRI and PSA testing in a large paired-cohort study.

In their retrospective review, the study authors reviewed data from 1793 men (mean age 59.7) who had biparametric prostate MRI and PSA testing for prostate cancer screening from January 2018 to June 2021. A urology consultation at a tertiary medical center was requested if the PSA level was 3 ng/mL or greater, or if prostate cancer was suspected based on MRI. The urologist in each center determined whether the patient needed follow-up or biopsy.

The researchers compared the proportion of men with a positive MRI, based on a Prostate Imaging Reporting & Data System [PI-RADS] score of 3-5 or 4-5, with those with a PSA level of 3 ng/mL or greater. The cancer detection rates, false positive rates, and PPVs were compared between the two screening tests. The PPVs were calculated from all screening-positive cases (PPV1) or biopsied cases (PPV2).

Overall, 150 men (8.4 percent) had a positive PSA test, a finding that was significantly greater than the proportion of men with a positive MRI result with 62 men (3.5 percent) with PI-RADS 3-5 and 41 men (2.3 percent) with PI-RADS 4-5.

The cancer detection rates were similar at 1.1 percent for PSA, PI-RADS 3-5, and PI-RADS 4-5. The false positive rate was significantly higher with the PSA test (7.4 percent) in comparison with that of MRI PI-RADS 3-5 scores (2.4 percent) and MRI PI-RADS 4-5 scores (1.2 percent). The PPVs were significantly lower with the PSA test (PPV1, 12.7 percent; PPV2, 36.5 percent) than that for PI-RADS 3-5 (PPV1 32.3 percent, PPV2 58.8 percent) or PI-RADS 4-5 (PPV1, 46.3 percent; PPV2, 87.5 percent).

For patients who underwent a biopsy, the sensitivity for detecting castration-sensitive prostate cancer was 95.2 percent for PI-RADS 3-5 and 90.4 percent for PI-RADS 4-5, according to the study. However, the researchers noted that a low proportion of the patients underwent a biopsy after positive screening results, at 54.8 percent to 58.5 percent with MRI and 35.3 percent with PSA, a factor that may contribute to overestimation of false positive rates for both tests.

A simplified cost-effectiveness analysis found that “despite the high cost, MRI was expected to reduce unnecessary costs for prostate cancer diagnosis,” according to the study authors.

1. Kim TM. The Role of Magnetic Resonance Imaging in Prostate Cancer Screening: Does it Perform Better than the Prostate-specific Antigen Test? Presented at: 2022 RSNA Annual Meeting. November 27-December 2, 2022. Chicago, IL.

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“MRI-based screening showed lower proportions of screening-positive cases, lower false positive rates, and higher PPVs [positive predictive values] than those of PSA-based screening,” noted Taek Min Kim, MD. 

MRI-based screening emerging as viable alternative to PSA testing

Ga-PSMA-11 PET imaging may miss small pelvic nodal metastases in men with intermediate- to high-risk prostate cancer.

“A PSMA PET scan negative for pelvic nodal metastasis does not indicate that a pelvic nodal dissection is not required,” wrote Thomas Hope, MD, of the University of California in San Francisco, and colleagues.

While pelvic nodal metastases detected at radical prostatectomy are associated with biochemical recurrence after prostatectomy, improved detection of metastatic disease is needed prior to definitive therapy.

This prospective phase 3 trial included 764 patients, median age 69, with intermediate- to high-risk prostate cancer considered for prostatectomy from December 2015 to December 2019. The primary end point was the sensitivity and specificity of 

Ga-PSMA-11 PET imaging for the detection of pelvic lymph nodes compared with histopathology on a per-patient basis. Each scan was read by three blinded independent readers.

Ga-PSMA-11 PET scan for primary staging, 277 (36%) underwent prostatectomy with lymph node dissection. Based on pathology reports, 75 of 277 men (27%) had pelvic nodal metastasis. For pelvic nodal, extra-pelvic nodal and bone metastatic disease, 

Ga-PSMA-11 PET results were positive in 40 of 277 (14%), two of 277 (1%), and seven of 277 (3%) of patients, respectively. The sensitivity and specificity for pelvic nodal metastases were 0.40 and 0.95, respectively, compared with histopathology.

“This study is the largest prospective study using PSMA PET at time of initial staging,” the authors said. The results of this study were used to support the recent U.S. Food and Drug Administration approval of 

In invited commentary, Joseph Osborne, MD, PhD, of Weill Cornell Medicine in New York, and colleagues wrote that the results are similar to those from the prior OSPREY trial evaluating PSMA PET diagnostic performance of 18F-DCFPyL.

 “There is a clear message from both trials: clinicians taking care of patients with high-risk prostate cancer being assessed for prostatectomy can use a positive PET scan as a true positive,” they wrote. “Whereas a negative scan cannot be used to exclude disease or inform nodal dissection (both studies had a diagnostic sensitivity near 40%).”

Osborne and colleagues added that the latest study “has provided a road map for how preintervention PSMA PET imaging will guide the appropriateness of radical prostatectomy for the referring urologists. As such, these results are practice changing for the nuclear medicine physicians, urologists and medical oncologists who will manage this cohort of patients.”

1. Hope TA, Eiber M, Armstrong WR, et al. Diagnostic accuracy of 

Ga-PSMA-11 PET for pelvic nodal metastasis detection prior to radical prostatectomy and pelvic lymph node dissection: a multicenter prospective phase 3 imaging trial [published online ahead of print September 16, 2021]. 

2. Osborne JR, Bander NH, Tagawa ST, et al. Prostate-specific membrane antigen positron emission tomography and the new algorithm for patients with prostate cancer prior to prostatectomy [published online ahead of print September 16, 2021]. 

"Clinicians taking care of patients with high-risk prostate cancer being assessed for prostatectomy can use a positive [PSMA] PET scan as a true positive, whereas a negative scan cannot be used to exclude disease or inform nodal dissection," wrote Joseph Osborne, MD, PhD, and colleagues. 

Katie Robinson

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MRI-based screening emerging as viable alternative to PSA testing

PSMA-PET imaging may miss small pelvic nodal metastases in men with prostate cancer