The Prostate Imaging Reporting and Data System (PI-RADS) is a five-point scale to assess potential prostate cancer in MR images. PI-RADS category 3 which offers an unclear suggestion of clinically significant prostate cancer continues to be a diagnostic challenge. Under current guidelines, a biopsy is advised for PI-RADS 3 lesions, though clinically significant prostate cancer is found in fewer than 20% of these cases. Now, new research has shown applying the PRIMARY scoring system to PET/MRI results can substantially improve diagnostic precision for patients with prostate cancer, potentially reducing unnecessary biopsies.

Researchers from Nanjing University Medical School (Nanjing, China) demonstrated that employing the PRIMARY scoring system, which integrates 68Ga-PSMA pattern, localization, and intensity data, could eliminate over 80% of unnecessary biopsies, albeit at the expense of missing one in eight significant prostate cancer cases. In the study, 56 men with PI-RADS 3 lesions underwent 68Ga-PSMA PET/MRI evaluations. The PRIMARY system was applied to interpret the prostate 68Ga-PSMA PET/MRI findings. Post imaging, each patient received a systematic prostate biopsy coupled with a targeted biopsy to ascertain the presence of clinically significant prostate cancer. Of the 56 men, eight (14.3%) were found to have clinically significant prostate cancer via biopsy. By applying a minimum PRIMARY score of four as the criterion for biopsy in men with PI-RADS 3 lesions, 40 out of 48 men (83.3%) could have avoided unnecessary biopsies, though this would involve missing 12.5% (one in eight) of clinically significant prostate cancer cases.

“PI-RADS 3 lesions present a dilemma to both urologists and patients because immediate biopsy could be unnecessary; however, a monitoring strategy could lead to some missed diagnoses of clinically significant prostate cancer,” said Hongqian Guo, MD, a urologist at Nanjing Drum Tower Hospital at the Affiliated Hospital of Nanjing University Medical School. “Hence, specifically ruling out clinically significant prostate cancer among PI-RADS 3 lesions has significant clinical implications.”

“By demonstrating the additive value of 68Ga-PSMA PET/MRI in classifying PI-RADS 3 lesions, this study provides new insight into the clinical indication for 68Ga-PSMA PET/MRI,” added Guo. “In the future, PI-RADS 3 patients could be referred for 68Ga-PSMA PET/MRI before prostate biopsy.” 

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