Radiation Therapy for DCIS Does Not Increase Risk of Cardiovascular Disease

Naomi B. Boekel, MSc

Women with ductal carcinoma in situ (DCIS) treated with radiation therapy had no increased risk of cardiovascular disease (CVD) compared with women in the general population or women with DCIS treated with surgery, according to results of a study in The Netherlands. The study was presented at the 2013 Breast Cancer Symposium, held September 7-9 in San Francisco, California.

“Doctors have been worried about late effects of breast radiation therapy, particularly cardiovascular disease,” said Naomi B. Boekel, MSc, the study’s lead author and a PhD student at The Netherlands Cancer Institute in Amsterdam. “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.”

The researchers collected data on 10,468 women in The Netherlands diagnosed with DCIS before the age 75 years between 1989 and 2004. About 71% of the women were treated with surgery alone (43% had a mastectomy and the rest underwent lumpectomy) and 28% were treated with surgery and radiotherapy. The median follow-up was 10 years; 19% of the women were followed for 15 years or more. The study compared the risk of CVD in women treated with radiotherapy with that of the general population of Dutch women and to different treatment groups of women with DCIS.

Compared with the general population, women with DCIS had a similar risk of dying from any cause (standardized mortality ratio [SMR] = 1.04; 95% CI, 0.97-1.11) and a 30% lower risk of dying of CVD (SMR = 0.77; 95% CI, 0.67-0.89). No difference was found in the risk of CVD in women treated with radiotherapy versus surgery alone (8% of patients treated with surgery plus radiation were diagnosed with CVD vs 9% treated with surgery alone). Likewise, no significant differences in the risk of CVD were observed in patients who received left-side radiotherapy (7%) versus right-side (8%; hazard ratio [HR] = 0.93; 95% CI, 0.67-1.30).

The findings are important in light of current concerns about overtreating patients with DCIS, said Boekel. Radiation therapy following lumpectomy for DCIS approximately halves the rate of cancer recurrence in the same breast. However, previous studies in breast and other cancers have shown that radiation to the heart region can increase the long-term risk of CVD, and in recent years, radiation therapy protocols have been adjusted to decrease exposure of the heart to radiation.

The slightly lower risk of dying from CVD in women with DCIS might be the result of those women being more health conscious than the general population, so that they underwent breast cancer screening or adopted a healthier lifestyle after DCIS diagnosis, Boekel said. In addition, factors such as education, socioeconomic status, and conflicting risk factors between CVD and DCIS (eg, age at menopause) may also play a role. “Studies with longer follow-up after breast radiation therapy are needed before definitive conclusions about cardiovascular disease risk can be drawn,” she said.