After Radiation for DCIS, No Increase in Cardiovascular Mortality, Morbidity

SAN FRANCISCO-The exposure of the heart to radiation during radiotherapy for ductal carcinoma in situ (DCIS) did not increase cardiovascular mortality or morbidity, according to a study by researchers in the Netherlands. In fact, compared to the general population, these women had a decreased risk of cardiovascular death.

The data, taken from a study of more than 10,000 women with DCIS, were presented by Naomi M. Boekel, PhD candidate at the Netherlands Cancer Institute, Amsterdam, at the American Society of Clinical Oncology (ASCO) Breast Cancer Symposium 2013.

“After a median follow-up duration of 10 years, DCIS patients had a lower risk of cardiovascular mortality, independent of treatment and had no increased risk for cardiovascular morbidity or mortality after radiotherapy for DCIS compared to surgery only,” Dr. Boekel said.

Women with DCIS interested in breast conservation often undergo both surgical resection of their cancer and radiation therapy. When patients undergo left-sided radiotherapy, the heart is in the radiation field; whereas, right-sided radiotherapy only exposes the heart to scattered radiation.

Although previous studies have shown that radiation to the heart increases the risk of cardiovascular diseases, radiation to the heart during DCIS is relatively low, Dr. Boekel said. However, the question of whether patients with DCIS have increased cardiovascular mortality or morbidity was worth exploring.

Dr. Boekel and colleagues conducted a large population-based study of 10,468 women with incident DCIS diagnosed between 1989 and 2004. All women were aged younger than 75 years and had a median follow-up of 10 years.

All-cause mortality was similar between patients with DCIS and the general population. In contrast, 5-year survivors of DCIS had a 30% lower risk of dying of cardiovascular disease compared with the general population (standardized mortality ratio = 0.77; 95% CI, 0.67–0.89).

“This lower risk might be due to lifestyle adaption after DCIS diagnosis,” Dr. Boekel posited. “It could also be due to conflicting risk factors between DCIS and cardiovascular disease such as age at menopause, or it could be due to differences in health consciousness.”

The researchers also compared cardiovascular outcomes among the women with DCIS by treatment group: surgery, right-handed radiotherapy and left-sided radiotherapy. Similar results were seen for mortality and morbidity from cardiovascular diseases between all treatment groups.

“Although these results are reassuring, longer follow-up is necessary before definite conclusions can be drawn,” Dr. Boekel said.

Commenting on the study, Steven O’Day, MD, director of clinical research at the Beverly Hills Cancer Institute, said that older radiation studies clearly showed a correlation between radiation and cardiovascular toxicity when the fields were overlapping with the heart.

“However, since then, radiation therapy has been refined,” he said.

This study should be reassuring to oncologists and should allow them to feel comfortable continuing aggressive treatment of DCIS, O’Day added.