A long-term follow-up of women treated for early-stage HER2-positive breast cancer has found that prophylactic beta-blocker therapy, given in the hope of protecting the heart during anti-HER2 treatment, was not associated with better cardiovascular outcomes years later. The analysis, published in the journal Cardio-Oncology, followed 109 participants from the PROTECT HER2 randomized controlled trial for a median of seven years after the original study ended, with follow-up ranging from five to ten years. During that extended observation window, only eight patients experienced any major adverse cardiovascular event, and the rates were not meaningfully different between women who had received the cardioprotective drug carvedilol and those who had received standard monitoring.
Anti-HER2 therapies such as trastuzumab have transformed the outlook for HER2-positive breast cancer, dramatically improving disease-free and overall survival over recent decades. That success, however, comes with a well-documented cardiac price: these treatments can cause changes in global longitudinal strain, an echocardiographic measure of heart muscle deformation, and in some patients progress to asymptomatic left ventricular systolic dysfunction or outright heart failure. To counter this, oncologists and cardiologists have explored cardioprotective therapy, typically beta-blockers or renin-angiotensin system inhibitors, started before or alongside cancer treatment to prevent cancer therapy-related cardiac dysfunction.
Most trials of this preventive strategy have been conducted in patients receiving anthracyclines, a class of chemotherapy with particularly notorious cardiac toxicity, or in sequential regimens combining anthracyclines with anti-HER2 agents, where the evidence is strongest. PROTECT HER2 was the first randomized controlled trial to test the approach specifically in early-stage breast cancer patients treated with non-anthracycline anti-HER2 regimens. In that original trial, conducted at Northwestern Memorial Hospital in Chicago between June 2015 and February 2020, 110 women with stage I to III HER2-positive breast cancer were enrolled. Patients with normal left ventricular ejection fraction but a decline in global longitudinal strain were randomized in a one-to-one ratio to receive carvedilol or to standard-of-care monitoring. The trial found no short-term benefit of the beta-blocker, whether measured by strain stability, cardiac dysfunction, or the need to hold cancer therapy.
The new report extends that question into survivorship. Because the long-term cardiovascular effects of prophylactic cardioprotection in this population remained unknown, the researchers performed a post hoc analysis of the trial cohort, collecting longitudinal data from electronic medical records after the randomized study ceased. One patient who suffered a non-fatal stroke during the trial itself was excluded, leaving 109 women with a mean age of 51 years. Of these, 83 had maintained normal ejection fraction and strain throughout the original study, 10 were randomized to carvedilol, 10 to observation, and 6 had reduced ejection fraction at baseline and received guideline-directed medical therapy.
The primary outcome was the incidence of major adverse cardiovascular events, a composite defined as all-cause and cardiovascular mortality, non-fatal stroke, non-fatal myocardial infarction, heart failure hospitalization, and the development of significant arrhythmias. Across the entire cohort, just 10 events occurred in 8 patients, or 7.3 percent. These comprised three deaths from non-cardiovascular causes, one non-fatal stroke, and six new diagnoses of arrhythmia. Notably, no non-fatal myocardial infarctions, no cardiovascular deaths, and no heart failure hospitalizations were recorded at all. In the two randomized arms of direct interest, neither deaths nor stroke occurred in either group.
The survival statistics reinforce how low the cardiac risk was in this cohort. Overall survival at eight years was 95.2 percent, with a 95 percent confidence interval of 87.9 to 99.2 percent. The five-year cumulative incidence of major adverse cardiovascular events was 5.6 percent, and the eight-year figure was 9.7 percent, roughly in line with the ten-year risk expected in the general adult population of the United States. Among the ten women randomized to carvedilol, the median duration of therapy after leaving the trial was 285 days, and only one patient continued the drug to the present day. Just one of the ten, or 10 percent, was transitioned to an ACE inhibitor or angiotensin receptor blocker to continue cardioprotection after stopping carvedilol. Nine of the ten discontinued the medication altogether, with a median total exposure of 650 days, a pattern the authors note likely limits any ability to detect a durable protective effect.
Perhaps the most striking finding concerns not the drug but the patients themselves: 40 percent of the cohort, 44 of 109 women, developed at least one new cardiovascular risk factor during follow-up that had not been present during the trial period. Eleven patients, 10 percent, were newly diagnosed with hypertension, another 11 with hyperlipidemia, three, or 2.7 percent, with type 2 diabetes, and 15, or 14 percent, showed an increase in body mass index averaging 5.1 kilograms per square meter. Twenty-six percent of patients initiated at least one new cardiovascular medication prescription, including ACE inhibitors, angiotensin receptor blockers, calcium channel blockers, diuretics, or statins. Yet despite this accumulation of risk, the analysis found no significant associations between the development of cardiovascular risk factors and major adverse cardiovascular events overall.
The echocardiographic data add further reassurance about the underlying cancer therapy. Among the 53 patients who had at least one post-trial echocardiogram, obtained at the discretion of each patient’s care team, no cancer therapy-related cardiac dysfunction was observed when referenced against baseline measurements from the original randomized trial. Moreover, all six patients in the reduced-ejection-fraction arm who developed cardiac dysfunction during the trial itself showed rapid recovery of ejection fraction by their three-month echocardiogram, and none re-developed dysfunction in subsequent assessments. This pattern is consistent with earlier evidence that trastuzumab-related declines in ejection fraction in early-stage patients are often transient; one seven-year study cited in the report found that 84 percent of such drops recovered, with only 2 percent of patients experiencing a new cardiac event after therapy.
The authors are careful about what these results do and do not prove. With a small sample, particularly in the randomized carvedilol arms of ten patients each, and very few clinical events, the study was substantially underpowered, and the absence of statistically significant differences should not be read as evidence that prophylactic cardioprotection is ineffective. The post hoc design relied on retrospective chart review, introducing potential bias and incomplete data, and all patients were treated at a single center, limiting generalizability. Breast cancer recurrence, which occurred in seven patients, and receipt of additional potentially cardiotoxic therapies were not adjusted for given the tiny number of events, and continuation of carvedilol after the trial was not protocolized, restricting causal inference. The authors also caution that some new risk factors may simply reflect normal aging over a long follow-up period. Their conclusion is that the findings are hypothesis-generating and support larger, adequately powered studies to identify which patients, if any, benefit from preventive therapy.
The practical message aligns with existing expert consensus, which does not endorse routine cardioprotective therapy for all patients on anti-HER2 regimens. For women with early-stage HER2-positive breast cancer treated with non-anthracycline protocols, major cardiovascular events appear rare over roughly seven years of follow-up, and universal prophylaxis in this low-risk group offers no demonstrated long-term advantage. Instead, the researchers argue, clinical attention should shift toward survivorship care and the modifiable risk factors that so many survivors acquire over time, a burden consistent with other breast cancer survivor cohorts, where one study of women completing HER2 therapy reported 33 percent developing hypertension and 58 percent developing hypercholesterolemia over roughly eight years. All breast cancer survivors, the authors conclude, regardless of their cardiotoxicity risk, should be counseled on cardiovascular risk factor screening and prevention strategies.
Subject of Research: Long-term cardiovascular outcomes of prophylactic beta-blocker cardioprotection in early-stage HER2-positive breast cancer survivors treated with non-anthracycline anti-HER2 therapy
Article Title: Long-term outcomes of prophylactic cardioprotection in early-stage breast cancer patients on non-anthracycline anti-HER2 therapy
Article References: McClelland, T. Q., Bolakale-Rufai, I. K., Zhiying, M., Baldridge, A. S., & Akhter, N. (2026). Long-term outcomes of prophylactic cardioprotection in early-stage breast cancer patients on non-anthracycline anti-HER2 therapy. Cardio-Oncology, 12(1), Article 119. https://doi.org/10.1186/s40959-026-00581-0
Image Credits: AI Generated
DOI: 10.1186/s40959-026-00581-0
Keywords: HER2-positive breast cancer, cardiotoxicity, beta-blockers, carvedilol, PROTECT HER2 trial, major adverse cardiovascular events, global longitudinal strain, cardiovascular risk factors, breast cancer survivorship, trastuzumab, cardioprotection, post hoc analysis
News Source: Nathaniel Bowman. (October 29, 2026). Prophylactic beta-blockers show no long-term heart benefit in early breast cancer survivors. Scienmag.
