Nuclear medicine

Multiparametric magnetic resonance imaging (mpMRI) has gained an increasingly large role in the local assessment of prostate cancer; ranging from risk stratification prior to initial prostate biopsy to anatomic assessment of known cancers prior to definitive therapy. PSMA PET/CT has similarly gained an increasingly large role in the assessment of distant prostate cancer metastases, whether to lymph nodes, bone, or viscera, at the time of biochemical recurrence following definitive local therapy.

Biopsy to anatomic assessment

More recently, PSMA PET/CT has been investigate in the pre-operative evaluation of patients with high-risk disease prior to definitive therapy present as a moderate poster at the American Urologic Association Annual Meeting, Dr. Pan and colleagues report their assessment of PSMA PET/CT in the detection and diagnosis of primary prostate cancer, with a comparison to mpMRI.
The authors relied on their locally maintained prospective database of patients who underwent prostate mpMRI between July 2013 and December 2017. Among this group; the authors then identified patients who underwent transperineal biopsy and PSMA PET/CT for initial staging. The indication for PSMA PET/CT was not clearly standardized. The authors assessed diagnostic rates of clinically significant prostate cancer (Gleason Grade Group ≥2).

Significant prostate cancer

Among 2283 patients who underwent prostate mpMRI; 239 patients also underwent both transperineal biopsy and PSMA PET/CT for initial staging. 202 of 239 biopsies (84.5%) demonstrated clinically significant prostate cancer while 21 (8.8%) demonstrated clinically insignificant prostate cancer, indicating that this was a very high risk population.

Of the 202 patients with clinically significant prostate cancer, abnormalities were identified on 189 PSMA PET/CT scans and 174 mpMRIs (Pi-RADs 4 or 5 lesions). MpMRI was associated with a higher false negative rate; but also fewer diagnoses of clinically insignificant prostate cancer. Overall; the authors report a sensitivity and specificity of 93.6% and 64.9%, respectively, for PSMA PET/CT and 87.1% and 70.3%, respectively; for mpMRI.

Transperineal biopsy

Thus, among this highly pre-selecte cohort of men undergoing mpMRI; transperineal biopsy, and PSMA PET/CT for initial prostate cancer evaluation; PSMA PET/CT had higher sensitivity for the diagnosis of clinically significant prostate cancer than mpMRI; at the expense of lower specificity resulting in increase diagnosis of clinically insignificant disease.
MpMRI retains particular value for the planning of definitive treatment owing to its superior soft-tissue resolution and anatomic detail. Presented by: Yen-Cheng Henry Pan, Medical Student at Monash University; South Yarra, Victoria, Australia
Co-authors: Arveen A. Kalapara, Daniel Moon, Uri Hanegbi, Adam Landau, Ross Snow, Richard O’Sullivan, Andrew Ryan, Mark Frydenberg, Jeremy Grummet