PRIMARY Score Superior to MRI for Detecting Clinically Significant Prostate Cancer

In a retrospective cohort study, the PRIMARY score was found to be superior to MRI in detecting clinically significant prostate cancer, demonstrating added diagnostic value in patients with negative or equivocal MRI results.

The current standard for detection of clinically significant prostate cancer is multiparametric MRI. Due to concerns about false-negative results, though, patients with negative or equivocal MRI results often undergo unnecessary biopsies. The PRIMARY score is based on PSMA PET/CT introduced into prostate cancer molecular imagining standardized evaluation (PROMISE) criteria. Shikuan Guo, MD, Xijing Hospital, Xi’an, Shaanxi, China, and coauthors wrote, “This score combines anatomic localization (peripheral, central, or transition zone), intraprostatic PSMA activity patterns (none, diffuse, or focal), and a very high [maximum standardized uptake volume] SUV_max (>12) to enhance the accuracy of primary tumor diagnosis.”

A retrospective cohort study was conducted to externally validate the PRIMARY score and evaluate its added diagnostic value to MRI triage in detecting clinically significant prostate cancer. This study included 431 patients who underwent both PSMA PET/CT and MRI prior to biopsy. The PRIMARY score and MRI was considered positive for either a PRIMARY score of 3 to 5, or Prostate Imaging Reporting and Data System (PI-RADS) 4/5.

Of the 431 patients included, 223 had clinically significant prostate cancer (51.7%). The area under the receiver operative characteristic curve of the 5-level PRIMARY score was significantly higher than that of MRI (0.873 vs 0.786; P < .001). The sensitivity and specificity of the PRIMARY score was 90.6% and 61.1%. The positive predictive value was 71.4%, and the negative predictive value was 85.5%. These values outperformed those of the PI-RADS on MRI (87.9%, 49.0%, 64.9%, and 79.1%, respectively).

Combining PRIMARY score and MRI improved the sensitivity (96.0%) and negative predicting value (91.5%) compared with MRI alone, without compromising specificity and positive predictive value. The combined approached avoided 24.6% of unnecessary biopsies, and missed 4.0% of clinically significant prostate cancer cases. While adding the PRIMARY score for patients with PI-RADS 1-3 showed a net benefit, it did not in patients with PI-RADS 4/5.

Dr Guo et al concluded, “The PRIMARY score was superior to MRI in detecting [clinically significant prostate cancer], and its added diagnostic value was in men with negative or equivocal MRI results.”

“The PRIMARY score plus MRI improved negative predictive value and sensitivity for [clinically significant prostate cancer] compared with MRI alone,” they added.

Source:

Guo S, Kang F, Ma S, et al. The PRIMARY Score: Diagnostic performance and added value compared with MRI in detecting clinically significant prostate cancer. Clinical Nuclear Medicine. 2024;49(1):37-44. doi:10.1097/RLU.0000000000004951