Atrial fibrillation and anticoagulation in patients with breast cancer

Objectives. To examine the long-term risk of thromboembolism and bleeding in patients with atrial fibrillation comparing patients with and without recent breast cancer in subgroups with or without anticoagulation therapy, respectively. Design. Using nationwide registries, patients with breast cancer from 1998–2015 and subsequent atrial fibrillation within 3 years were stratified on anticoagulation and matched 1:3 on age, sex and comorbidities with atrial fibrillation patients without breast cancer. Risks of thromboembolism and bleeding were estimated by Aalen-Johansen and multivariable cox regression models. Results. Atrial fibrillation patients with and without anticoagulation were matched, respectively (201 and 525 with breast cancer matched with 603 and 1,575 without breast cancer). In patients with CHA2DS2-VASc-score >1 and anticoagulation the three years risks of thromboembolism were 4.2% (95% confidence interval (CI) 1.1–7.3) and 3.2% (CI 1.5–4.9) in patients with and without breast cancer. The risks of bleeding were 5.3% (CI 1.7–8.9) and 5.1% (CI 3.0–7.1), respectively. Breast cancer was associated with a similar risk of thromboembolism in patients with and without anticoagulation, respectively (Hazard ratio (HR) 1.10, CI 0.63–1.92 and HR 1.11, CI 0.82–1.50) and a similar risk of bleeding in patients with and without anticoagulation, respectively (HR 1.01, CI 0.56–1.84 and HR 0.85, CI 0.57–1.27) compared with the matched controls. Conclusions. Breast cancer was not associated with altered risk of thromboembolism or bleeding in patients with atrial fibrillation irrespective of treatment with anticoagulation. Our analyses suggest that atrial fibrillation diagnosed in patients with breast cancer should be considered as primary atrial fibrillation.

研究目的
旨在探讨心房颤动（atrial fibrillation）患者中，分别按抗凝治疗与否分层后，合并近期乳腺癌与未合并近期乳腺癌者的血栓栓塞与出血长期发病风险。

研究设计
本研究依托全国性登记数据库，纳入1998年至2015年确诊乳腺癌且3年内新发心房颤动的患者，按抗凝治疗情况分层，并以1:3的比例匹配年龄、性别与合并症匹配的无乳腺癌心房颤动患者。采用Aalen-Johansen法（Aalen-Johansen）与多变量Cox回归模型评估血栓栓塞与出血风险。

研究结果
最终匹配得到接受抗凝治疗的乳腺癌合并心房颤动患者201例，匹配无乳腺癌心房颤动患者603例；未接受抗凝治疗的乳腺癌合并心房颤动患者525例，匹配无乳腺癌心房颤动患者1575例。在CHA₂DS₂-VASc评分（CHA₂DS₂-VASc）＞1且接受抗凝治疗的患者中，乳腺癌组与对照组的3年血栓栓塞风险分别为4.2%（95%置信区间（Confidence Interval, CI）1.1~7.3）与3.2%（95%CI 1.5~4.9）；出血风险分别为5.3%（95%CI 1.7~8.9）与5.1%（95%CI 3.0~7.1）。校正后分析显示，无论是否接受抗凝治疗，乳腺癌组的血栓栓塞风险与匹配对照组均无显著差异：接受抗凝组的风险比（Hazard Ratio, HR）为1.10（95%CI 0.63~1.92），未接受抗凝组HR为1.11（95%CI 0.82~1.50）；出血风险亦与对照组无显著差异：接受抗凝组HR为1.01（95%CI 0.56~1.84），未接受抗凝组HR为0.85（95%CI 0.57~1.27）。

研究结论
无论是否接受抗凝治疗，乳腺癌均不会改变心房颤动患者的血栓栓塞或出血风险。本研究结果提示，乳腺癌患者确诊的心房颤动可被视为原发性心房颤动。