Baseline Cardiac Imaging in Breast Cancer Needs to Change

Fran Lowry

September 18, 2018

Current cardiac imaging practices in breast cancer patients treated with chemotherapy need to be reconsidered, say Canadian researchers.

Cardiac imaging to detect baseline subclinical left ventricular dysfunction in women undergoing chemotherapy for early-stage breast cancer (EBC) should be based on a woman's specific risk factors for cardiovascular disease, rather than on the treatment she is receiving, they suggest.

"This is not what we are doing today," Paaladinesh Thavendiranathan, MD, Toronto General Hospital, University of Toronto, Canada, told Medscape Medical News.

"Instead we are doing imaging based on the drug treatment that the patient is being given. So, if she is receiving trastuzumab, she will automatically be imaged. Yet, there is a subgroup of women who are at extremely low risk for heart failure [HF].

"For example, I'm seeing a 30-year-old today who is receiving trastuzumab. She is completely healthy otherwise, has no cardiovascular risk factors. We know her risk of running into trouble is extremely low, and perhaps imaging her may not be the best thing to do," Thavendiranathan said. "Whereas, if I see a 71-year-old woman who has hypertension, I would want to make sure her cardiac function was normal before starting treatment."

In research that was published earlier this year in the Journal of Clinical Oncology, Thavendiranathan and his team found that virtually all women who received trastuzumab-containing regimens underwent cardiac imaging, whereas 67.3% of patients who received only anthracyclines underwent imaging.

The population-based retrospective cohort study included 18,444 women (median age, 55 years) who had been treated with chemotherapy for EBC in the province of Ontario between 2007 and 2012.

Patients with at least one risk factor for HF underwent imaging less frequently (61.2%) than patients with no risk factors (64.7%; P < .001).

Additionally, the odds of being screened were doubled if the treating physician was a woman.

The study also assessed the 5-year incidence of major adverse cardiac events (MACE) and found that across all treatment regimens, the incidence was two to six times higher among patients who had risk factors for HF.

For patients with HF risk factors who received anthracyclines without trastuzumab, the 5-year incidence of MACE (4.5%) was higher than for patients with no HF risk factors who received trastuzumab without anthracyclines (2.6%).

However, cardiac imaging was performed less frequently in the group who had risk factors for HF (73.3%) than in the group who had no HF risk factors (93.6%) (P <. 001).

"Patient-specific factors, including HF risk factors, made very little contribution to variation in imaging," said Thavendiranathan. "This risk-imaging mismatch should make us reconsider current cardiac imaging practices in breast cancer patients treated with chemotherapy."

The reasons for this disconnect in risk imaging are several, says a team of researchers from Memorial Sloan Kettering Cancer Center (MSKCC), New York City, in a linked editorial.

"For one thing, there is scepticism about the relevance of existing guidelines that do not factor in patients' cardiovascular risk factors," commented Richard Steingart, MD, a cardiologist at MSKCC, who is a coauthor of the editorial.

"There are recommendations about how patients should be monitored from a cardiovascular perspective, but they paint with a very broad brush, meaning that you need to screen a lot of patients before you'll find those that you're interested in, and this poses a burden for the patient and the treating oncologist," Steingart told Medscape Medical News.

Then there is uncertainty as to whether an asymptomatic decline in left ventricular ejection fraction in EBC patients predicts subsequent risk for overt HF.

"The crucial question is, once you have done this imaging and risk stratification, what is the proof that in fact you improve the outcome of the women from a cardiovascular perspective? And to date, there is no well-controlled, scientific study that has proven that," Steingart noted.

"There's a reasonable expectation that it will, but to design and conduct a study to prove the point is quite challenging," he added.

A decade of follow-up has shown that the incidence of HF during therapy for EBC is low, and new-onset symptomatic HF, at least in patients taking part in clinical trials, is extremely rare after completion of adjuvant chemotherapy, he commented.

In addition, primary prevention trials that have evaluated the potential role of cardioprotective medicines in all patients with breast cancer treated with drugs that are potentially cardiotoxic have not demonstrated a clear, clinically meaningful result.

Steingart said that package inserts for the drugs used in chemotherapy say nothing about a patient's risk.

"They just make blanket statements that you should do this monitoring. And the difficulty is that the people who have to make decisions about these patients' cardiovascular risks are not internists or cardiologists; they are oncologists, and they may not have the comfort level with making that assessment," he said.

The study was supported by the Heart and Stroke Foundation/University of Toronto Polo Chair in Cardiology Young Investigator Award, the Canadian Institute of Health Research New Investigator Award, and the Ontario Ministry of Health. Dr Thavendiranathan has financial relationships with Takeda Canada and Janssen Canada. Dr Steingart has disclosed no relevant financial relationships.

J Clin Oncol. 2018;May23:JCO2018779736; Aug 31:JCO2018789354. Abstract, Editorial

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