The role of the size and number of index lesion in the diagnosis of clinically significant prostate cancer in patients with PI-RADS 4 lesions detected by multiparametric MRI of the prostate

44 Background: This study aimed to evaluate the contribution of the size and number of the sampled lesions to the diagnosis of clinically significant prostate cancer (CSPC) in patients who had PI-RADS 4 lesions detected by multiparametric MRI (mpMRI) of the prostate and underwent in-bore biopsy (IB). Methods: In this retrospective study, data of 295 patients who underwent IB for PI-RADS 4-5 lesions between 2012 and 2021 were analyzed, and a total of 159 patients with only PI-RADS 4 lesions were included. Clinical and radiological data, including age, PSA level, previous biopsy information, and the size and the number of PI-RADS 4 lesions were recorded. Patients with a lesion classified as Grade Group 2 and above were considered to have CSPC. Univariate and multivariate regression analyses were used to evaluate the factors affecting the diagnosis of prostate cancer (PCa) and CSPC. Results: A great majority (86.8%) of the patients had undergone a biopsy for the first time. About three-fourths (71.7%) of the patients had PCa, and half (54.1%) had CSPC. In multivariate analysis, the relationship between PCa and age, index lesion size, low PSA levels, and first biopsy patients were found significant, while CSPC exhibited a significant relationship with age and first biopsy patients. When the patients were divided into three groups according to the index lesion size (10 mm), the prevalence of PCa was 64.3%, 67.5%, and 82.4% and the prevalence of CSPC was 42.9%, 51.2%, and 64.7% respectively. Conclusions: While the size of PI-RADS 4 lesions was significant in predicting PCa, it had no significance in detecting CSPC. The number of lesions was insignificant in predicting both conditions. However, the prevalence of PCa was high, especially in patients with PI-RADS 4 lesions larger than 10 mm, which in turn increased the probability of the lesion being Grade Group 2 or above. [Table: see text]