ORLANDO – Concomitant treatment with candesartan protects against the early decline in left ventricular ejection fraction associated with adjunct therapy for early breast cancer.
That was the key finding in the PRADA trial (PRevention of cArdiac Dysfunction during Adjuvant breast cancer therapy), the largest study to date looking at prevention of cardiac dysfunction in a breast cancer population.
Another important finding in PRADA was that unlike the angiotensin receptor blocker candesartan (Atacand), metoprolol, a beta blocker, didn’t prevent the early drop in LVEF commonly seen in breast cancer patients treated with anthracyclines and trastuzumab (Herceptin), even though both classes of heart medications are cornerstones of the treatment of ischemic and hypertensive cardiomyopathy, Dr. Geeta Gulati reported at the American Heart Association scientific sessions.
Although the cardiotoxicity of certain breast cancer treatments is widely recognized and has spawned the emerging field of cardio-oncology, the literature in this area is weak. Indeed, a recent meta-analysis identified only four published randomized studies evaluating the possible cardioprotective role for beta blockers and angiotensin antagonists in patients undergoing anthracycline-based chemotherapy (Postgrad Med J doi:10.1136/ postgradmedj-2015-133535). None of the studies was double-blind, all relied upon echocardiographic assessment of changes in LVEF rather than gold-standard cardiac MRI, and the study sizes were small -- just 18-45 breast cancer patients.
Most problematic of all, the studies employed a variety of different definitions of cardiotoxicity, noted Dr. Gulati of Akershus University Hospital in Lorenskog, Norway.
In contrast, PRADA was a double-blind, placebo-controlled, 2 by 2 factorial design, single-center trial, which included 120 patients with early breast cancer. Participants were randomized to candesartan at a starting dose of 8 mg and target dose of 32 mg/day, metoprolol starting at 25 mg with a target of 100 mg/day, or placebo after breast cancer surgery but before the start of anthracycline-containing chemotherapy.
The primary endpoint was change in LVEF from baseline to completion of adjuvant therapy, a period as short as 10 weeks and as long as 64 weeks depending upon whether a woman also underwent courses of trastuzumab, taxanes, and/or radiation therapy.
The overall decline in LVEF was 2.6% in the placebo group and 0.6% in the candesartan group, a significant difference. Metoprolol didn’t put a dent in the LVEF decline.
“Observational studies show early reduction in LVEF is associated with increased risk of developing heart failure later. So if a sustained, long-term effect of angiotensin inhibition can be confirmed in larger multicenter trials, preventive therapy may be indicated as standard care for breast cancer patients,” Dr. Gulati said.
Discussant Dr. Bonnie Ky of the University of Pennsylvania, Philadelphia, called PRADA an important study that moves the field of cardio-oncology forward, yet it’s also a trial that raises more questions than it answers.
PRADA certainly addresses a major problem: “The incidence of heart failure and cardiomyopathy increases over time in breast cancer patients exposed to anthracyclines and trastuzumab. Because patients are living longer because of cancer chemotherapy, their risk of dying of cardiovascular disease actually exceeds that of recurrent cancer in the long term,” she observed.
The study has three major limitations that prevent its findings being implemented in routine clinical practice at this time, Dr. Ky said. One is its relatively small size, even though it’s far bigger than any previous study. Another limitation is that this was an extremely low-cardiovascular-risk patient cohort: the baseline prevalence of diabetes was only 1.5%, fewer than 7% of patients had hypertension, and the baseline LVEF was 63%. That may be why no one developed a substantial decrement in LVEF or actual heart failure.
And since the incidence of cardiomyopathy following breast cancer therapy is known to climb over time, reaching a cumulative 12% at 6 years followup in trastuzumab-treated patients and 20% in those who receive both anthracyclines and trastuzumab (J Natl Cancer Inst. 2012 Sep 5;104(17):1293-305), the lack of extended followup time in PRADA is a significant shortcoming, she added.
The important questions raised by PRADA, Dr. Ky continued, include whether carvedilol or another beta blocker would have generated a positive result where metoprolol failed. Also, should the target population for prevention of cardiotoxicity be more narrowly focused on those at higher baseline cardiovascular risk? And bearing in mind that change in LVEF is a surrogate endpoint, what might be a more clinically meaningful and valid outcome measure? What’s the effect of carvedilol and other cardioprotective medications on cardiac biomarkers in breast cancer patients? And the most important questions of all, she said: What would be the effects of longer followup time and extended therapy?