Relationship between the number of lymph nodes dissected and prognosis in muscle‐invasive bladder cancer in the era of neoadjuvant chemotherapy

OBJECTIVES: Many studies have shown a good prognostic association with a large number of lymph node dissections. However, most of these studies did not include patients who have received neoadjuvant chemotherapy. The purpose of this study was to verify the relationship between survival outcomes and the number of lymph nodes removed during radical cystectomy in patients with muscle-invasive bladder cancer in the era of neoadjuvant chemotherapy. METHODS: This retrospective study considered patients who were diagnosed with clinical ≥T2N0M0 muscle-invasive bladder cancer and treated with radical cystectomy at the Nagoya University Hospital and affiliated hospitals from January 2004 to December 2019. We excluded patients who had a history of upper tract urothelial cancer or non-urothelial carcinoma. The association between prognosis and the number of lymph nodes removed was investigated. RESULTS: We retrospectively enrolled a total of 477 patients. The mean number of lymph nodes dissected was 14. Two hundred and twenty-six patients (47.4%) received neoadjuvant chemotherapy. More extensive lymphadenectomy (≥15 lymph nodes) correlated with better 5-year overall survival across all patients (68% vs. 57%, p = 0.01). In patients who received neoadjuvant chemotherapy, there was no difference in overall survival according to the number of dissected lymph nodes (66% vs. 71%, p = 0.433). In patients who did not receive neoadjuvant chemotherapy, ≥15 lymph nodes dissected was associated with significantly better overall survival (70.3% vs. 46.9%, p < 0.01). CONCLUSIONS: No association between more aggressive lymph node dissection and prognosis was found in patients who underwent neoadjuvant chemotherapy. Conversely, extended lymph node dissection is desirable for patients who have not received neoadjuvant chemotherapy.