Double product derived from exercise stress echocardiography (ESE) or dobutamine stress echocardiography (DSE) in patients with a history of breast cancer and radiotherapy (RXT) exposure and MACE

Abstract Background Breast cancer survivorship has markedly improved in the last two decades due to improved therapies. Among these, adjuvant chest radiotherapy stands out as an integral part of the current treatment. Chest radiotherapy can trigger accelerated atherosclerosis, which, coupled with cardiovascular (CV) risk factors common to this population, can lead to increased rates of coronary artery disease (CAD). ESC 2022 guidelines have established both Exercise Stress Echocardiography (ESE) and Dobutamine Stress Echocardiography (DSE) as cost-efficient and reliable tools for screening this patient population. Recommendations include ESE or DSE 5 years after radiotherapy as a screening tool. Double product (DP), an index common to both tests, parallels myocardial oxygen consumption. It has been used to predict major adverse cardiovascular events (MACE) in other cohorts. Purpose We sought to evaluate if DP could be used as a prognostic indicator for MACE (myocardial infarction, stroke, cardiovascular death, and heart failure) in this population. Methods Breast cancer patients treated with adjuvant radiotherapy from 2000 to 2022 were included. ESE or DSE was done after a mean of 5.4 years (1Q-2.2, 3Q-7.5) post-radiotherapy. Uni and multivariable adjusted Cox regression models were performed to evaluate the association between DP quartiles achieved and the risk of MACE in DSE and ESE groups. MACE-free survival among different quartiles was plotted with the Kaplan Meier method. Results 696 patients were included, with a mean age of 65 (SD 10.0) and 72 (SD 9.4) in ESE and DSE respectively. 61% of patients had ESE. In ESE, we observed increased rates of MACE in the 1st quartile when compared to the other quartiles (Figure 1a). On the other hand, univariate and multivariate Cox models established that for every increase of 1000 units of DP achieved during ESE, there is a risk-reduction of 9% [HR=0.91 (0.86-0.95); p=<0.01] in the future incidence of MACE, thus establishing DP as a protective marker. Additionally, advanced age was shown to be a major risk factor as well [HR=4.58 (1.91-10.9); p=<0.01]. In the DSE cohort however, the development of MACE was equally distributed across DP quartiles even after adjusting for existing comorbidities (Figure 1b). Cox analysis did not establish DP as a prognostic tool in this cohort (Table 1). Conclusion DP is established as an excellent prognostic tool for the detection of MACE in patients who underwent ESE. Patients who achieve higher DP quartiles during these tests have lower future rates of MACE. Regarding DSE, DP is not a good prognostic tool. This could be explained by higher burden of cardiovascular risk factors in this patient population. ESE should be recommended when possible.