Assessing double product derived from stress echocardiography as a prognostic indicator of major adverse cardiac events in patients with breast cancer treated with radiotherapy.

Background: Breast cancer survivors treated with radiotherapy (RT) face elevated long-term risk of cardiovascular complications. Double product (DP), the product of systolic blood pressure and heart rate, reflects myocardial workload and may serve as a simple prognostic marker. We evaluated whether peak DP during exercise or dobutamine stress echocardiography predicts major adverse cardiovascular events (MACE) and all-cause mortality (ACM).

Methods: We retrospectively studied patients who had breast cancer treated with RT and underwent follow-up testing with ESE or DSE from 2000 through 2022. Univariate and multivariate Cox regression models were used to evaluate the association between MACE/ACM and risk factors in each group. Kaplan-Meier analysis was used to compare ACM and MACE-free survival among the different DP quartiles.

Results: Our study included 696 patients. ESE (n = 425) or DSE (n = 271) was performed at a median of 4.4 (IQR, 2.2-7.5) years after RT. For the ESE group, the rate of MACE was higher in the lowest quartile. Patients in the 3rd and 4th quartile had a decreased risk of MACE and ACM (hazard ratio [HR] per 1,000-mm Hg/min increase, 0.92 [95% CI, 0.88-0.97]; P < .001 and HR, 0.91 [95% CI, 0.87-0.96]; P < .001) respectively. Advanced age (> 60 years) was also seen to be a predictor of MACE in this group (HR, 5.22 [95% CI, 2.13-12.75]; P = < .001). Additionally, treatment with doxorubicin-based chemotherapy was associated with an increased risk of ACM but not MACE (HR, 1.78 [95% CI, 1.04-3.05]; P = .03). For the DSE group, rate of MACE was similar among DP quartiles, indicating that this is not a prognostic indicator. However, a history of diabetes and dyslipidemia were shown to be predictors of MACE (HR, 1.58 [95% CI, 1.05-2.37]; P = .02; and HR, 1.77 [95% CI, 1.12-2.79]; P = .01).

Conclusions: DP achieved during ESE but not DSE is an excellent tool for the prediction of MACE and ACM in this patient population; therefore, ESE should be recommended as the test of choice when possible. A history of atrial fibrillation, diabetes and dyslipidemia were identified as significant predictors of adverse cardiovascular outcomes in the DSE group, highlighting individualized monitoring and early intervention for patients at higher risk.