Prevalence and clinical significance of incidental findings on multiparametric prostate MRI

Purpose: To assess the prevalence and clinical significance of incidental findings (IFs) detected at multiparametric prostate MRI examination. Materials and methods: Multiparametric prostate MRIs of 647 consecutive patients (mean age 67.1 ± 8.0 years) were retrospectively evaluated by two radiologists recording the presence of all extra-prostatic IFs. Findings were classified as related to or not related to genitourinary system and divided into three classes, according to their clinical significance, as follows: group 1, not significant or scarcely significant; group 2, moderately or potentially significant; and group 3, significant. Differences in distribution of IFs between patients ≤ 65 years old and patients > 65 years old were assessed using Pearson’s χ2 or Fisher’s exact test. Statistical significance level was set at p < 0.05. Results: Incidental findings (n = 461) were present in 341 (52.7%) patients, while 306 (47.3%) patients did not have any extra-prostatic IF. Overall, IFs were significantly more common in patients > 65 years old (n = 225, 57.0%) compared to patients ≤ 65 years old (n = 116, 46.0%, p = 0.007). There were 139 (30.2%) IFs related to genitourinary system and 322 (69.8%) IFs not related to genitourinary system. Group 3 IFs were almost exclusively present in patients > 65 years old (2.8%, p = 0.034) and included 7 (1.1%) bladder carcinomas, 3 (0.5%) testicle tumors, 2 (0.3%) rectal cancers. Twenty-seven (4.2%) of the 647 patients underwent surgical treatment for IFs not directly related to prostate cancer. Conclusion: IFs not related to prostate cancer may be frequently encountered on multiparametric prostate MRI, and they are significantly more common in patients > 65 years old.