, according to a population-level cohort study published in Cancer.
While patients with lymph node–negative stage III disease had superior overall survival at 5 years, survival rates were similar between patients with node–positive stage III disease and stage IV disease. This supports reclassifying stage III node-positive RCC to stage IV, according to researchers.
“Prior institutional studies have indicated that, among patients with stage III disease, those with lymph node disease have worse oncologic outcomes and experience survival that is similar to that of patients with American Joint Committee on Cancer (AJCC) stage IV disease,” wrote Arnav Srivastava, MD, of Rutgers Cancer Institute of New Jersey, New Brunswick, and colleagues.
The researchers used data from the National Cancer Database to identify patients with AJCC stage III or stage IV RCC who had undergone nephrectomy and lymph node dissection.
The cohort included 8,988 patients, 6,587 of whom had node–negative stage III disease, 2,218 of whom had node–positive stage III disease, and 183 of whom had stage IV metastatic disease. The researchers compared relative survival between staging groups.
The 5-year overall survival rate was 61.9% in patients with node–negative stage III RCC (95% confidence interval, 60.3%-63.4%), 22.7% in patients with node-positive stage III RCC (95% CI, 20.6%-24.9%), and 15.6% in patients with stage IV RCC (95% CI, 11.1%-23.8%).
“Patients with lymph node–positive stage III disease and those with stage IV disease were found to have overlapping 95% CIs when measuring 5-year survival; both demonstrated similar mortality,” the researchers reported. They further noted that these findings remained unchanged when patients were stratified by clear cell and non–clear cell histology.
In an accompanying editorial, Daniel D. Shapiro, MD, of the University of Texas MD Anderson Cancer Center, Houston, and E. Jason Abel, MD, of the University of Wisconsin–Madison, said the study results suggest the clinical phenotype of patients with isolated lymph node metastases is different from other stage III RCCs.
“Future editions of the AJCC staging system [should] recognize the increased risk with [lymph node–positive stage III] tumors and consider reclassification of [these] tumors as stage IV tumors so that baseline risks are more accurately measured in these rare populations,” they recommended.
Dr. Srivastava and colleagues acknowledged that two key limitations of the study were the retrospective design and the absence of data on other survival measures, such as metastasis-free and cancer-specific survival.
“Despite these limitations, we believe the current study was able to significantly build on prior work recommending the reclassification of lymph node–positive RCC as stage IV cancer,” they concluded.
The National Cancer Institute supported the study. Some study authors disclosed relationships with pharmaceutical companies and other organizations for work performed outside of the current study. The editorial authors disclosed no conflicts of interest.
SOURCE: Srivastava A et al. Cancer. 2020 Jul 1;126(13):2991-3001.