Risk of pacemaker or implantable cardioverter defibrillator after radiotherapy for early-stage breast cancer in Denmark, 1982-2005.

BACKGROUND AND PURPOSE: To examine the risk of cardiac conduction abnormalities or severe ventricular arrhythmias requiring implantation of a cardiac implantable electronic device (CIED), either a pacemaker or an implantable cardioverter-defibrillator, subsequent to breast cancer (BC) radiotherapy (RT).

MATERIAL AND METHODS: All women treated for early-stage BC in Denmark from 1982 to 2005 were identified from the Danish Breast Cancer Cooperative Group. By record linkage to the Danish Pacemaker and ICD Registry information was retrieved on CIED implants subsequent to RT. Standardized incidence ratios (SIR) of CIED implantation were estimated for women receiving RT and compared to women not receiving RT for BC. Uni- and multivariate Poisson regression models were used to estimate incidence rate ratios (IRR) among irradiated women compared to non-irradiated.

RESULTS: Of 44,423 BC patients, 179 had a CIED implanted among 18,251 women who received RT, and 401 had a CIED in 26,172 who did not receive RT. The unadjusted IRR was 1.09 (0.91-1.30 95% CI) for CIED implants among women receiving RT compared to non-irradiated women and the IRR was 1.13 (0.93-1.38 95% CI) when adjustments were made.

CONCLUSIONS: BC RT as practiced in Denmark in 1982-2005 did not increase the risk of CIED implants. This indicates that RT for BC does not increase the risk of severe ventricular arrhythmias or cardiac conduction abnormalities.