MP09-01\u2003HOW LONG SHOULD PROSTATE-MRI BE DELAYED AFTER PROSTATE BIOPSY TO MINIMIZE HEMATOMA ARTIFACT?

Abstract

INTRODUCTION AND OBJECTIVES: Prostate MRI is commonly used to evaluate a rising PSA after a prostate biopsy. However, the optimal timing of post-biopsy MRI is debated due to conflicting reports on the incidence of post-biopsy hematoma. Here we query a large institutional cohort to determine the optimal timing of post-biopsy prostate MRI. METHODS: Men undergoing a multiparametric prostate MRI (with T1, T2, diffusion weighted, and dynamic contrast enhanced sequences) between 2002-2013 at our institution prior to radical prostatectomy were identified. Men without a prior prostate biopsy and men with prior prostate cancer treatment were excluded. Endorectal coils were used with both 1.5T and 3T scanners. Hemorrhage was identified primarily using T1 sequences. Time from biopsy was modeled as a continuous variable in univariable and multivariable logistic regression. Youden′s J statistic was calculated to determine the time point after biopsy associated with the most discriminative value in terms of hematoma on MRI. RESULTS: In a cohort of 396 men undergoing a staging prostate MRI, median time from prostate biopsy to MRI was 61 days (IQR 31-125) and 27% (N=107) had prostate hematoma artifact on MRI. Increasing time from prostate biopsy to MRI was significantly associated with a reduced rate of visible prostate hematoma (Figure 1). On univariate logistic regression, each month between prostate biopsy and MRI was associated with reduced odds of visible prostate hematoma (OR 0.90, 0.84-0.97, p<0.01). On multivariable logistic regression, time from prostate biopsy remained the only significant association with visible prostate hematoma, despite adjusting for number of prior biopsy cores, age, cT stage, T3 vs T1.5 magnet, and PSA. A threshold of 51 days after prostate biopsy maximized the Youden index and had the most discriminative value with respect to visible hematoma rates. Patients undergoing an MRI within 51 days of MRI had a 37% chance of hematoma compared to 19.5% for those undergoing MRI after at least 51 days from biopsy (p<0.01). CONCLUSIONS: Time from prostate biopsy was the only determinant of visible hematoma on MRI in our dataset. Waiting more than 50 days from biopsy to MRI was the optimal threshold to minimize hematoma rates. This data can assist with patient counseling for the timing of MRI after a prostate biopsy. Figure. No caption available. Source of Funding: none