Prostate cancer patients with lymphatic node involvement detected by immunohistochemistry. Is the effort worthwhile?

Introduction: Lymph node (LN) status is one of the main prognostic factors in localized prostate cancer (CaP) patients after surgery. Examining palpable lymph nodes with hematoxylin and eosin (HE) is the most common approach in clinical practice; however, immunohistochemistry (IHC) has been reported to increase the LN detection rate. We reviewed the oncological results of patients with LN metastasis detected by IHC. Methods: Retrospective study of CaP patients who underwent lymphadenectomy at the time of the prostatectomy. Extended lymphadenectomy was performed with complementary indocyanine green (ICG) guidance. Three groups were considered according to LN status. Definition of the pN+ group was made if LNs were detected by HE, occulted lymph node-positive (OLN+) was considered when ≥ 1 LN was identified with IHC and occulted lymph node-negative (OLN-) if no metastatic nodes were found. Oncological outcomes were reported regarding PSA kinetics, biochemical recurrence (BCR), need for secondary treatments and metastasis-free survival (MFS). Results: A total of 283 patients with a median follow-up of 69 months were included in the study. Immunohistochemical assessment revealed metastatic LNs in 8.9% of patients. The rate of locally advanced disease and positive surgical margins was higher in the OLN + and pN + groups vs the OLN - group (P < 0.05). At the end of follow-up, 19%, 44% and 52% of patients from the OLN -, OLN + and pN + groups experienced BCR (P < 0.001), respectively. Additionally, 2.6%, 17% and 22% of patients developed metastatic progression from the OLN -, OLN + and pN+ group (P < 0.001), respectively. In the multivariate analysis, the OLN + group had a higher risk HR: 12 (95% CI, 2.4-56; P = 0.002) of metastatic progression in comparison with OLN - patients. This difference was not observed in the risk of biochemical recurrence HR 1.8 (95% CI, 0.9-3.8; P = 0.09). Conclusion: Conventional HE histological analysis underdiagnosed nearly 10% of patients. IHC-detected patients were at higher risk of metastasis development than OLN - patients. This report highlights the importance of optimizing the anatomopathological analysis properly.