Association between chronic kidney disease and mortality in stage IV cancer

Background Chronic kidney disease (CKD) is known to be associated with cancer mortality. However, no study has considered the well-known cancer prognostic factors, ECOG Performance Status (PS) and cancer treatment, as confounding factors. We assessed the independent relationship between CKD and cancer death in stage IV cancer patients. Methods In this retrospective observational study, we included stage IV cancer patients diagnosed from 2009 to 2014 in a single center. We collected baseline clinical and laboratory variables, and cancer-specific variables, and assessed the presence of CKD. Our primary outcome was all-cause mortality. The secondary outcome was cancer-specific mortality and site-specific cancer mortality. Results Among 961 eligible stage IV cancer patients (median age 69 years, 51.8% male), 150 patients had CKD. During follow-up (median 9.8 months), 638 patients died, of whom 526 patients died from cancer. After adjusting for prognostic variables, including ECOG PS and cancer treatment, all-cause mortality and cancer-specific mortality were significantly higher in CKD patients than in non-CKD patients (HR 1.41, 95% CI 1.13-1.77 and HR 1.43, 95% CI 1.12-1.83, respectively). In patients with breast and kidney and urinary tract cancers, CKD was associated with a significantly increased risk of death (HR 7.01, 95% CI 1.47-33.4 and HR 3.33, 95% CI 1.42-7.78, respectively). Conclusions CKD at the time of stage IV cancer diagnosis was associated with all-cause mortality and cancer-specific mortality. Moreover, the association between CKD and cancer-specific death was site specific for breast cancer and kidney and urinary tract cancer.