Impact of Rheumatoid Arthritis on the Mortality of Elderly Patients Who Develop Cancer: A Population-Based Study.

Objective: Comorbidity among cancer patients poses additional risks for mortality. The possible impact of rheumatoid arthritis (RA) on cancer patient survival is unclear. Our objective was to examine survival among elderly patients with RA who develop cancer.

Methods: Patients diagnosed with breast, prostate, colorectal, or lung cancer between 2001 and 2010 were identified from the Texas Cancer Registry and Medicare-linked databases. The cohort was categorized into 3 groups according to the number of claims patients had with a diagnosis of RA in the year prior to the cancer diagnosis: 2-RA (patients with ≥2 claims), 1-RA (1 claim), and no claims. Overall survival was estimated for these groups and for each cancer, using Cox proportional hazards models adjusting for covariates.

Results: The cohort included 139,097 patients with cancer (35,026 breast, 43,181 prostate, 31,103 colorectal, and 29,787 lung); 1.7% had 1 RA claim, and 1.1% had 2 or more. Adjusted hazard ratios for patients in the 2-RA group were 1.41 (95% confidence interval [95% CI] 1.21-1.65) for breast and 1.53 (95% CI 1.26-1.85) for prostate. No significant differences were observed for those with colorectal or lung cancer.

Conclusion: Mortality was increased by 40% and 50%, respectively, in elderly patients with RA who developed breast or prostate cancer, after controlling for other comorbidities. This association was not seen in cancers with shorter survival time (colorectal or lung). Research is needed to determine whether the increased risk is related to comorbid burden or to differential utilization of cancer or rheumatoid therapies in patients with both diseases.