Conference Coverage

Therapy ups breast cancer survivors’ cardiac risks



– Oncologists and cardiologists need to work hand-in-hand when managing the care of women with breast cancer whose treatment plan includes cardiotoxic therapies and breast irradiation, reported specialists.

Dr. Jennifer E. Liu, director of cardiovascular laboratories at Memorial Sloan Kettering Cancer Center, New York Neil Osterweil/MDedge News

Dr. Jennifer E. Liu

Depending on the cancer subtype, women with breast cancer may receive chemotherapy with a cardiotoxic anthracycline such as doxorubicin or epirubicin, or a HER2-targeted agent such as trastuzumab (Herceptin), pertuzumab (Perjeta), or ado-trastuzumab emtansine (Kadcyla).

“The cardiotoxicity related to breast cancer has been a well publicized issue, and chances are your patients know about it and are concerned as well,” Jennifer E. Liu, MD, director of cardiovascular laboratories at Memorial Sloan Kettering Cancer Center in New York, said at the American College of Cardiology’s Advancing the Cardiovascular Care of the Oncology Patient meeting.

Anthracyclines, trastuzumab, and HF

In large adjuvant therapy trials of anthracyclines and trastuzumab in women with breast cancer, doxorubicin alone was associated with an asymptomatic decline in left ventricular ejection fraction (LVEF) of 4% to 11%, and a less than 1% incidence of heart failure (HF), Dr. Liu noted.

When patients received an anthracycline followed by trastuzumab, the incidence of asymptomatic LVEF decline ranged from 4% to 19%, the incidence of clinical HF was 2% to 4%, and the rate of trastuzumab interruption for cardiac adverse events ranged from 5% to 18%.

In comparison, in trials with trastuzumab in combination therapy that did not contain an anthracycline, the risk of cardiovascular complications was lower, with asymptomatic decline in LVEF ranging from 3.2% to 9.4%, and class III/IV HF occurring in just 0.5% of patients. In trials combining trastuzumab and pertuzumab, there were no increases in cardiac toxicity over trastuzumab alone.

Although with longer follow-up, the approximately 4% rate of HF in patients treated with anthracycline-based chemotherapy, paclitaxel, and trastuzumab in the NSABP B-31 trial has not changed significantly; retrospective claims-based studies reflecting daily practice have shown significantly higher rates of HF and or cardiomyopathy, Dr. Liu said.

She cited a 2012 study showing that among 45,537 women with a mean age of 76 years who were treated for breast cancer, the 3-year incidence rates of HF and/or cardiomyopathy were 32% for patients treated with trastuzumab alone, and 41.9% for those treated with an anthracycline followed by trastuzumab. Other, smaller studies also showed lower but significantly elevated risks for the drugs.

The discrepancy between clinical trial and “real world” results may be chalked up to the fact that claims-based data rely on diagnostic codes that may not accurately reflect the actual cardiac diagnosis, and by the fact that clinical trials have strict entry criteria that exclude patients with cardiovascular disease, she said.

Radiation risks

Radiation therapy is associated with a more than 7% increase in major coronary events per Gy of mean heart dose, Dr. Liu noted, citing a 2013 study (N Engl J Med. 2013;368:987-98).

Paul Nguyen, MD, a radiation oncologist at the Dana-Farber/Brigham and Women’s Cancer Center in Boston, said that risk factors for radiation-induced heart disease include anterior or left chest irradiation, cumulative doses above 30 Gy, patient age younger than 50 years, doses of more than 2 Gy per fraction, presence and extent of tumor in or near the heart, lack of radiation shielding, concomitant chemotherapy (especially with anthracyclines), and preexisting cardiovascular disease or risk factors.

Dr. Paul Nguyen, a radiation oncologist at Dana-Farber/Brigham and Women’s Cancer Center in Boston Neil Osterweil/MDedge News

Dr. Paul Nguyen

For patients with breast cancer, the risk of developing radiation-induced heart disease has diminished considerably with the adoption of heart-sparing techniques over the last several decades, including 3-D conformal techniques, intensity-modulated radiation therapy, proton beam therapy, novel patient positioning techniques that allow radiation only to the cancer-involved breast, and deep inspiration breath holds in which the radiation beam is gated to turn on only when the patient is holding a deep breath, Dr. Nguyen noted.


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