*Purpose:
To assess the efficacy of multiparametric magnetic resonance imaging (mpMRI) in the measurement of the dominant nodule greatest dimension (GD) in patients with clinically significant prostate carcinoma (PCa) when compared to post-prostatectomy (PP) measurement.

*Methods and Materials:
This single-institutional, retrospective study included patients who had a mpMRI and radical prostatectomy between January 1, 2017 and January 1, 2022. The average time period between MRI and prostatectomy was 5.06 months (154 days). Data on patients with aggressive PCa with Gleason Score greater than or equal to 7 and PI-RADS Score greater than or equal to 4 was reviewed. Of 166 patients, 96 met the criteria for inclusion (mean age, 65 years; age range, 50-77). Pearson correlation was used to determine the relationship between measurement of GD on mpMRI and PP. In order to illustrate the degree of agreement between measurement of GD on mpMRI and PP, a Bland-Altman plot was created. Next, linear regression was run to determine if statistically significant proportional bias existed. Exploration of mpMRI overestimation and underestimation was also performed.

*Results:
Pearson correlation between mpMRI and PP GD revealed a significant positive relationship to exist (r = 0.397, p < 0.001). Linear regression of Bland-Altman results revealed a statistically significant proportional bias to exist (p = 0.015) with a small-medium effect size (r = 0.249). Further comparative analysis revealed that 47/96 (48.96%) patient mpMRIs overestimated (>10%), 27/96 (28.13%) underestimated (<-10%), and 22/96 (22.91%) were on target (-10%≤x≤10%) regarding the GD when compared to PP. Median percentage overestimation and underestimation were 50.0% and 23.1%, respectively.

*Conclusions:
MRI measurement of the GD in patients with clinically significant PCa was significantly different when compared to the gold standard of PP measurement, with a tendency to overestimate tumor size. Further research is needed to understand the etiology and impact of this overestimation on clinical decision-making.

Caleb Gilberg

SUNY Upstate Medical University

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