Immune‐related conditions and cancer‐specific mortality among older adults with cancer in the United States

Immunity may play a role in preventing cancer progression. We studied associations of immune-related conditions with cancer-specific mortality among older adults in the United States. We evaluated 1 229 443 patients diagnosed with 20 common cancer types (age 67-99, years 1993-2013) using Surveillance Epidemiology and End Results-Medicare data. With Medicare claims, we ascertained immune-related medical conditions diagnosed before cancer diagnosis (4 immunosuppressive conditions [n = 3380 affected cases], 32 autoimmune conditions [n = 155 766], 3 allergic conditions [n = 101 366]). For each cancer site, we estimated adjusted hazard ratios (aHRs) and 95% confidence intervals (CIs) for cancer-specific mortality associated with each condition, applying a Bonferroni cutoff for significance (P < 5.1 × 10-5 ). Bayesian metaanalysis methods were used to detect patterns across groups of conditions and cancers. We observed 21 associations with cancer-specific mortality at the Bonferroni threshold. Increased cancer-specific mortality was observed with rheumatoid arthritis for patients with melanoma (aHR 1.51, 95% CI 1.31-1.75) and breast cancer (1.24, 1.15-1.33)), and with hemolytic anemia for bladder cancer (2.54, 1.68-3.82). Significant inverse associations with cancer-specific mortality were observed for allergic rhinitis (range of aHRs: 0.84-0.94) and asthma (0.83-0.95) for cancers of the lung, breast, and prostate. Cancer-specific mortality was nominally elevated in patients with immunosuppressive conditions for eight cancer types (aHR range: 1.27-2.36; P-value range: 7.5 × 10-5 to 3.1 × 10-2 ) and was strongly associated with grouped immunosuppressive conditions using Bayesian metaanalyses methods. For older patients with several cancer types, certain immunosuppressive and autoimmune conditions were associated with increased cancer-specific mortality. In contrast, inverse associations with allergic conditions may reflect enhanced immune control of cancer.