Use of Immunosuppression and the Risk of Subsequent Overall or Cancer Mortality

Abstract

Purpose: To determine the incidence of all-cause and cancer mortality (CM) in association with immunosuppression.

Design: Retrospective cohort study at ocular inflammatory disease (OID) subspecialty centers. We harvested exposure and covariate data retrospectively from clinic inception (earliest in 1979) through 2010 inclusive. Then we ascertained overall and cancer-specific mortalities by National Death Index linkage. We constructed separate Cox models to evaluate overall and CM for each class of immunosuppressant and for each individual immunosuppressant compared with person-time unexposed to any immunosuppression.

Participants: Patients with noninfectious OID, excluding those with human immunodeficiency infection or preexisting cancer.

Methods: Tumor necrosis factor (TNF) inhibitors (mostly infliximab, adalimumab, and etanercept); antimetabolites (methotrexate, mycophenolate mofetil, azathioprine); calcineurin inhibitors (cyclosporine); and alkylating agents (cyclophosphamide) were given when clinically indicated in this noninterventional cohort study.

Main outcome measures: Overall mortality and CM.

Results: Over 187 151 person-years (median follow-up 10.0 years), during which 15 938 patients were at risk for mortality, we observed 1970 deaths, 435 due to cancer. Both patients unexposed to immunosuppressants (standardized mortality ratio [SMR] = 0.95, 95% confidence interval [CI], 0.90-1.01) and those exposed to immunosuppressants but free of systemic inflammatory diseases (SIDs) (SMR = 1.04, 95% CI, 0.95-1.14) had similar mortality risk to the US population. Comparing patients exposed to TNF inhibitors, antimetabolites, calcineurin inhibitors, and alkylating agents with patients not exposed to any of these, we found that overall mortality (adjusted hazard ratio [aHR] = 0.88, 0.89, 0.90, 1.11) and CM (aHR = 1.25, 0.89, 0.86, 1.23) were not significantly increased. These results were stable in sensitivity analyses whether excluding or including patients with SID, across 0-, 3-, or 5-year lags and across quartiles of immunosuppressant dose and duration.

Conclusions: Our results, in a cohort where the indication for treatment was proven unassociated with mortality risk, found that commonly used immunosuppressants-especially the antimetabolites methotrexate, mycophenolate mofetil, and azathioprine; the TNF inhibitors adalimumab and infliximab, and cyclosporine-were not associated with increased overall and CM over a median cohort follow-up of 10.0 years. These results suggest the safety of these agents with respect to overall and CM for patients treated with immunosuppression for a wide range of inflammatory diseases.

Financial disclosure(s): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Keywords: Cancer mortality; Immunosuppression; Mortality; Tumor necrosis factor inhibitor; antimetabolite.