Mortality and major adverse cardiac events in women with breast cancer receiving radiotherapy: a 10-year cohort study of patients and population controls

Background

Treatment for breast cancer (BC) frequently involves radiotherapy. Guidelines recommend screening for cardiac adverse events starting 10 years after radiotherapy. The rationale for recommending this interval is unclear and informed the objective of this study.

Objectives

Study cardiovascular event rates in the first decade following curative radiotherapy for breast cancer, the time frame before guidelines recommend screening.

Methods

We performed a monocentric, retrospective study enrolling all women with unilateral BC in 2007–2008, who received radiotherapy as part of their curative treatment. We compared event rates during 10 years follow-up with an age and risk factor-matched control population (FLEMENGHO population).

Results

We included 1095 BC patients (median age 55y, IQR: 47–66y). Two hundred and eighteen (19.9%) women died. Cancer and cardiovascular mortality accounted for 107 (49.1%) and 22 (10.1%) deaths, respectively. The incidence of coronary artery disease was similar compared to age and risk-matched women [risk ratio 0.75 (95% CI 0.48–1.18)], yet heart failure (HF) [risk ratio 1.97 (95% CI 1.19–3.25)] and atrial fibrillation or flutter (AF) (risk ratio 1.82 (95% CI 1.07–3.08) occurred more often. Age [HR 1.040 (95% CI 1.012–1.069)], tumor grade [HR 1.646 (95% CI 1.103–2.458)], and neo-adjuvant treatment setting [HR 3.079 (95% CI 1.432–6.620)] were risk factors for mortality; hormonal therapy [HR 0.007 (95% CI 0.001–0.042)] proved protective. Risk factors for MACE were mean heart dose [HR 1.079 (95% CI 1.012–1.151], hormonal therapy, history of cardiovascular disease [HR 2.771 (95% CI 1.253–6.126)], and Mayo Clinic Cardiotoxicity Risk Score [HR 2.547 (95% CI 1.538–4.217)]. While mean heart dose [HR 1.141 (95% CI 1.017–1.282)] and cardiovascular history [HR 3.374 (95% CI 1.259–9.043] clearly associated with new onset HF, only a trend towards higher AF burden with increasing mean heart dose could be observed.

Conclusions

Ten-year mortality following curative treatment for unilateral BC was mainly cancer-related. HF and AF constituted significantly increased risks in the first decade following irradiation. Mean heart dose, pre-existing cardiovascular diseases, and Mayo Clinic Cardiotoxicity Risk Score were risk factors for early cardiac mortality and adverse events and should guide early dedicated cardio-oncological follow-up.

Funding Acknowledgement

Type of funding sources: None.

P695Impact of atrial fibrillation on 10y all-cause mortality in curatively treated breast cancer patients

Background

Contemporary treatment options for breast cancer have significantly improved survival during the last two decades. To estimate cancer survival, current practice typically relies on cancer size and the presence of metastases, whereas cardiovascular comorbidities such as atrial arrhythmias are typically not taken into account.

Aim

To evaluate the incidence of atrial fibrillation and flutter among curatively treated breast cancer patients and assess its impact on survival in an all-comer population at a tertiary care centre.

Methods

In a large, single centre, retrospective study we enrolled all patients with a diagnosis of breast cancer in 2007 and 2008 who received radiation therapy as part of their curative treatment regimen. We performed Kaplan-Meier and Cox survival analyses to calculate mortality risk over 10-year follow up.

Results

We included 1338 patients, 1326 (99.1%) of whom were women. Mean age (± standard deviation) at diagnosis was 57.6±13.4 years and the distribution of left sided breast cancer versus right sided or bilateral breast cancer was 655 (49.0%) patients versus 645 (48.2%) and 38 (2.9%) patients, respectively. A total of 805 (60.1%) patients had at least one ECG recorded during the 10 year follow up. In this subgroup, atrial fibrillation or flutter was present in 70 (8.7%); 23 patients had pre-existing atrial fibrillation or flutter (32.9%), 26 patients had had radiation therapy for left sided breast cancer (37.1%) versus 21 patients for right sided breast cancer (30%; p=0.375 for left versus right sided radiation therapy). Of the total cohort, 327 (24.4%) patients died during 10 year follow-up. In the subgroup with at least a single ECG recording, mortality equaled 44.3% (31/70) in patients with one or more documented episodes of atrial fibrillation or flutter during follow-up, compared to 21.9% (161/735) in patients who remained in sinus rhythm (p<0.0001). In patients with pre-existing atrial fibrillation or flutter, mortality equaled 47.8% (11/23) versus 42.6% (20/47) in patients with atrial fibrillation or flutter manifesting after treatment initiation (p=0.683).

Survival Atrial Fibrillation/Flutter

Conclusion

Atrial fibrillation and flutter are common in patients with curative breast cancer treatment and have a significant impact on overall survival. Our study highlights the impact of cardiac comorbidities on overall survival following cancer treatment and emphasizes the importance of a dedicated cardiac follow-up in cancer survivors.