Session: LBA03: Late-Breaking Abstracts III - Cancer
LBA03-02: Survival of lymph-node-positive prostate cancer patients after radical prostatectomy on dichotomization using a maximal lymph-node-metastasis diameter of 2 mm
Introduction: Pelvic lymph node (LN) dissection (PLND) during radical prostatectomy (RP) is recommended by various guidelines addressing patients with high-risk prostate cancer (PCa). Histopathological evidence of LN metastasis (LN+) is prognostic of a poor oncological outcome, although the optimal treatment for such patients remains unclear. As previously suggested for breast cancer and melanoma, the American Joint Committee on Cancer (AJCC)/Union for International Cancer Control (UICC) eighth edition describes micrometastasis as LN+ of diameter = 2 mm, but supporting data are lacking. We evaluated LN+ patients’ survival after radical prostatectomy (RP) by the LN maximum tumor diameter (MTD). Methods: We retrospectively enrolled patients pathologically diagnosed as LN+ status after PLND during RP performed without neoadjuvant therapy between 2006 and 2019 at the 33 institutions. Of 561 eligible patients, those evaluated in terms of LN+ maximum tumor diameter were included. Patients were stratified by a LN+ MTD cutoff of 2 mm, and data for 301 patients were analyzed. The outcomes included castration resistance-free survival (CRFS), metastasis-free survival (MFS), cancer-specific survival (CSS), and overall survival (OS). Results: In total, 301 patients were divided into two groups [LN+ MTD > 2 mm (n = 222) and = 2 mm (n = 79)]. The median follow-up time was 5.2 years (IQR 2.8–9.0 years). The median age was 68 years and the median PSA value at diagnosis was 14.7 ng/mL. Patients of LN+ status > 2 mm exhibited significantly decreased CRFS and MFS (P < 0.001 and P = 0.017, respectively), and inferior CSS and OS (P = 0.098 and 0.062, respectively). In patients with a PLND number = 10, those of LN+ > 2 mm status evidenced significantly decreased CRFS, MFS, and OS (P = 0.003, 0.009, and 0.035, respectively), but for patients with a PLND number < 10, there was no significant survival difference by the maximum LN+ tumor diameter. Finally, few patients of LN+ = 2 mm status died from prostate cancer during follow-up. Multivariate Cox’s regression analysis showed that the PSA level at diagnosis, a biopsy Gleason pattern 5, clinical N1 stage, and LN+ > 2 mm status significantly predicted CRFS. Conclusions: We found that patients of LN+ = 2 mm status experienced more favorable outcomes after RP with a PLND number = 10. Postoperative observation only can be considered for such patients. Our findings support the utility of the pN substaging proposed by the AJCC/UICC eighth edition, which will enable precision medicine for patients with advanced PCa. SOURCE OF Funding: none
