Association between Tumor Multifocality on Multi-parametric MRI and Detection Rate of Clinically-Significant Prostate Cancer in Lesions with Prostate Imaging Reporting and Data System (PI-RADS) Score 4
Kamyar Ghabili Amirkhiz, MD1, Matthew Swallow, MD1, Rachael Sherrer, MD2, Jamil Syed, MD1, Michael Leapman, MD1, Soroush Rais-Bahrami, MD2, Preston Sprenkle, MD1
1Yale School of Medicine, New Haven, CT, 2University of Alabama at Birmingham, Birmingham, AL
Background
Magnetic resonance imaging (MRI)/ultrasound fusion targeted biopsy of a lesion with prostate imaging reporting and data system (PI-RADS) score 4 (P4) is associated with a high positive predictive value (~ 45%) for clinically-significant prostate cancer. However, it is unknown if multifocality on multi-parametric MRI (mpMRI) could further risk stratify P4 lesions. We sought to assess the detection of the clinically-significant prostate cancer in P4 lesions stratified by tumor multifocality on mpMRI.
Methods
Using the MRI-ultrasound fusion prostate biopsy databases at two institutions, we identified patients with at least one PI-RADS 4 (P4) lesion on mpMRI who underwent targeted biopsy of those lesions. Each patient meeting the above criteria was grouped into one of four lesion MRI classifications - group 1 (an index lesion with P4 and an additional PI-RADS 2 or 3 lesion), group 2 (single lesion with P4), group 3 (two or more P4 lesions), or group 4 (a lesion with P4 and an index lesion with PI-RADS 5). The rate of grade group (GG)≥2 pathology on targeted biopsy of the P4 lesions was compared between the MRI classification groups. The clinical and radiological factors associated with finding GG ≥2 in P4 lesions were also evaluated.
Results
In a combined cohort, 645 patients with at least one lesion with P4 were identified. The studied MRI classification groups 1, 2, 3, and 4 included 184, 267, 112, and 82 men, respectively. For the combined cohorts, the rate of GG≥2 biopsy pathology in the groups 1, 2, 3, and 4 was 21.7%, 36.3%, 49.1%, and 42.7%, respectively (p<0.001, Figure 1). On multivariable analysis, age (OR 1.06, 95%CI 1.03-1.09, p<0.001), clinical T2 (OR 1.59, 95%CI 1.03-2.47, p=0.03), PSA density (OR 1.43 per 0.1 unit, 95%CI 1.22-1.67, p<0.001), peripheral zone lesion (OR 1.62, 95%CI 1.01-2.59, p=0.04), and MRI lesion group (group 2 vs. 1, OR 1.93, 95%CI 1.21-3.08, p=0.006; and group 3 vs. 1, OR 3.28, 95%CI 1.88-5.72, p<0.001) were significantly associated with the risk of GG≥2 pathology on targeted biopsy of the P4 lesion.
Conclusions
Our data indicated that the rate of clinically-significant prostate cancer detection in P4 lesions located within peripheral zone might be increased with the presence of additional high-grade lesions on imaging (PI-RADS 4 or 5). By contrast, men with a P4 lesion and an additional low-grade lesion (PI-RADS 2 or 3) showed the lowest rate of aggressive pathology. Overall, detection of clinically-significant prostate cancer on biopsy of the P4 lesions might be influenced by tumor multifocality on imaging. 
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