(ChemotherapyAdvisor) – Despite widespread concerns about the late cardiovascular effects of breast radiotherapy, women who have been administered radiation for ductal carcinoma in situ (DCIS) do not face an increased risk of cardiovascular disease, according to a large population-based study by researchers in the Netherlands, who presented their findings during the 2013 Breast Cancer Symposium held in San Francisco, CA.

“After a median follow-up of 10 years, we did not find an increased risk for cardiovascular morbidity or mortality after radiotherapy for DCIS when comparing surgery and radiotherapy versus surgery only, nor when comparing radiotherapy for left- versus right-sided DCIS,” reported lead study author Naomi Boekel, MSc, of the Netherlands Cancer Institute in Amsterdam, the Netherlands.

“Doctors have been worried about late effects of breast radiation therapy, particularly cardiovascular disease,” noted Boekel. “Our findings suggest that routine radiation therapy for women with DCIS does not appear to increase the risk of developing cardiovascular disease later in life. This is especially important in light of the current concerns about overtreating patients diagnosed with DCIS.”

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However, longer follow-up is needed “before definitive conclusions about cardiovascular disease risk can be drawn,” she cautioned.

The study included data for 10,468 women diagnosed with DCIS before age 75, between the years of 1989 and 2004.

Regardless of treatment, DCIS survivors had a slightly lower risk of dying from cardiovascular disease—but this was not likely a direct result of treatment, Boekel was quick to note.

“Compared with the general population, 5-year survivors of DCIS had a similar risk of dying due to any cause (standardized mortality ratio (SMR) = 1.04; 95% CI: 0.97-1.11), but a lower risk of dying of CVD (SMR=0.77; 95% CI: 0.67-0.89),” Boekel reported.

Women treated for DCIS might be “more health conscious” and better educated than women in the general public, and menopause might also represent a conflicting risk factor for DCIS and cardiovascular disease. Factors such as these, rather than treatment, likely account for the reduced cardiovascular mortality noted among DCIS survivors, she said.

Untreated, DCIS can progress into invasive breast cancer. In most cases, it is treated with lumpectomy and frequently, radiotherapy. Radiation cuts the risk of recurrence by half, Boekel noted.