SC279- The pathway of isolated seminal vesicle invasion has a different impact on biochemical recurrence after radical prostatectomy and pelvic lymphadenectomy

Author of the study: Prostate cancer with seminal vesicle invasion (SVI) has been considered an aggressive cancer and an independent predictor of overall mortality. PCa can invade seminal vesicles through different routes. In 1993, Ohori et al. described three types of invasion: i) type 1: direct spread along the ejaculatory duct from inside; ii) type 2: seminal vesicle invasion outside the prostate, through the capsule; iii) type 3: the presence of cancer island(s) in the seminal vesicle with no continuity from the primary tumor (discontinuous metastases). Evidence from published studies showed controversial data about the prognostic significance of the different patterns of seminal vesicle invasion. The current study aimed to evaluate the prognostic significance of the different patterns of isolated SVI in patients undergoing RP and lymph nodes dissection.Materials and methods: We retrospectively analysed all patients who underwent surgery between 2007 and 2019. Inclusion criteria: localized prostate adenocarcinoma, isolated SVI at RP (no metastasis to lymph node), at least 24-month follow-up, no adjuvant treatment. Patterns of SVI were following Ohori’s classification. Patients with type 3 SVI (isolated or in association with other types of invasion) were included in the same group. Biochemical recurrence (BCR) was defined as any postoperative PSA > 0.2 ng/ml. Time to BCR was investigated using the Kaplan-Meier analysis with the log-rank test.Results: 1356 men underwent RP and lymph node dissection during the study period. Among these, 61 patients met the inclusion criteria and were included. Median age was 67(7.2) years. Median PSA was 9.4 (8.92) ng/ml. Mean follow-up was 85.28 ± 45.27 months. BCR occurred in 28(45.9%) patients. Non-focal extraprostatic extension and positive surgical margin were present in 7 (11.5%) and 39(63.9%), respectively. The median number of examined lymph nodes was 18(4) and did not differ between patients with and without BCR ( p = 0.821). Logistic regression analysis showed that a positive surgical margin (OR: 19.964, 95% CI: 1.172 29.322, p = 0.038) was predictor of BCR. Kaplan-Meier analysis demonstrated that patients with pattern 3 SVI had a significantly shorter time to BCR compared to other groups (log- rank, p = 0.016). The estimated time to BCR was 48.7 months in Ohori type 3, 60.9 months in pattern 1 + 2, 74.8, and 100.8 months in isolated patterns 1 and 2, respectively. In patients with negative surgical margins, pattern 3 SVI confirmed a shorter time to BCR compared to other types of invasion, with an estimated time to BCR of 30.8 months. Conclusions: In this study we found that surgical margin status was the only predictor of BCR in patients with SVI and negative lymph nodes at RP. Nevertheless, type 3 SVI was correlated to poorer prognosis and had a significantly shorter estimated time to BCR compared with other types of SVI, which was confirmed in the subgroup of patients with negative surgical margins.