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Treatment choices, not cardiac risk, appeared to drive decisions regarding pretreatment cardiac imaging in women with early breast cancer, a large retrospective study suggested.

Women with heart failure risk factors at baseline had a significantly higher incidence of major adverse cardiac events (MACE) during follow-up. Nonetheless, pretreatment cardiac imaging occurred significantly less often (P<0.001) when patients with risk factors received anthracycline-based chemotherapy than when those with or without risk factors received trastuzumab (Herceptin).

"Logistic regression indicated that most variation in baseline imaging was related to chemotherapy, followed by physician-level factors," Paaladinesh Thavendiranathan, MD, of Toronto General Hospital, and co-authors reported online in the . "Patient-specific factors, including heart failure risk factors, made minimal contribution to variation in imaging."

"This risk-imaging mismatch is an impetus to reconsider current cardiac imaging practices in patients who receive chemotherapy for breast cancer."

The authors of a pointed out that the results corroborated those of a conducted in the United States, showing that physician-related factors dominated decision-making regarding pretreatment cardiac imaging for patients with breast cancer.

"The authors appropriately stated that risk-imaging mismatch existed possibly because of a lack of validated risk-prediction models and absence of prospective data linking guideline adherence to heart failure outcomes," Chau T. Dang, MD, of Memorial Sloan Kettering Cancer Center in New York City, and co-authors wrote.

"Moving forward, we should conduct trials tailored toward patient and treatment risks that could influence guidelines. A strong collaboration between the cardiology and oncology communities will enable optimal cardiac and cancer care, providing patients with the most effective and life-extending cancer therapy with minimal interruption, while hopefully achieving improved cardiac outcomes."

Therapy-related heart failure constitutes a major source of morbidity and mortality in cancer survivors. Baseline left ventricular ejection fraction (LVEF) is a key predictive factor for heart failure risk in patients treated with anthracyclines or trastuzumab, Thavendiranathan and coauthors noted in their introduction. Pretreatment cardiac imaging can detect subclinical LV dysfunction, which occurs in .

Several studies showed poor adherence to published recommendations for use of pretreatment cardiac imaging to guide cancer treatment decisions, the authors continued. Reasons for the lack of adherence remain poorly understood, and Thavendiranathan and colleagues sought to add information to the issue.

They retrospectively reviewed the records of women who received chemotherapy for early-stage breast cancer in Ontario during 2007-2012. The team further identified patients who had cardiac imaging before chemotherapy or within 30 days after completing treatment and evaluated the rates of MACE on the basis of baseline heart failure risk and chemotherapy received.

The analysis involved 18,444 women who had a median age of 55 at the time of treatment for breast cancer. The records showed that 10,160 patients received anthracyclines alone, 832 received trastuzumab alone, 3,154 received sequential therapy, and 4,298 received other chemotherapy regimens. The records also showed one or more heart failure risk factors for 4,522 patients in the anthracycline group, 581 in the trastuzumab group, 1,349 in the sequential group, and 2,961 in the other-chemotherapy group.

Overall, patients with heart failure risk factors underwent cardiac imaging less often than those without risk factors (61.2% versus 64.7%, P<0.001), and imaging rates varied substantially by treatment group. A total of 67.3% of patients treated with anthracyclines alone underwent cardiac imaging, as compared with 95.7% of those who received sequential chemotherapy, 93.6% of those treated with trastuzumab alone, and 22.6% of patients who received other regimens.

Patients treated with anthracyclines alone were significantly more likely to undergo cardiac imaging if they had heart failure risk factors (73.3% versus 62.6%, P<0.001), whereas the imaging rate in the trastuzumab-only subgroup was identical in patients with or without heart failure risk factors.

Patients with heart failure risk factors had higher rates of MACE across all four treatment groups. In the anthracycline-only group, patients with heart failure risk factors had a 5-year MACE rate of 4.5% versus 1.7% for those without risk factors. In the trastuzumab-only subgroup, the 5-year cumulative MACE rate was 8.2% in patients with risk factors and 2.6% in those without. Corresponding rates were 11.3% and 5.8% among patients who received sequential therapy and 6.5% versus 1.0% for those who received other chemotherapy.

The authors noted that anthracycline-treated patients with risk factors underwent cardiac imaging significantly less often than did trastuzumab-treated patients without risk factors (73.3% versus 93.6%, P<0.001).

Multivariable analysis showed that baseline risk factors influenced decisions regarding cardiac imaging (OR 1.15-2.40, P=0.014 to P<0.001). In contrast, the choice of therapy had a dominant impact on the imaging decision: anthracyclines only (OR 6.59, 95% CI 4.97-8.74, P<0.001); sequential therapy (OR 88.02, 95% CI 55.51-142.13, P<0.001); and trastuzumab only (OR 67.78, 95% CI 40.12-114.51, P<0.001).