Dutch Study Shows that Radiation Therapy for Ductal Carcinoma In Situ Does Not Seem to Increase Cardiovascular Disease Risk

The first large study to evaluate long-term effects of radiotherapy for DCIS on cardiovascular morbidity and mortality

A large population-based study in the Netherlands found that women who had received radiation therapy to treat ductal carcinoma in situ of the breast (DCIS) have no increased risk of cardiovascular disease compared to the general population of Dutch women, nor compared to DCIS patients treated with surgery only. These results may be helpful to women who are deciding on their treatment plan and seem reassuring for DCIS survivors treated with radiotherapy. This is the first large study to evaluate long-term effects of radiotherapy for DCIS on both the incidence of cardiovascular disease and associated death rates.

The study was presented in the poster discussion session during the 2013 Breast Cancer Symposium (7-9 September, San Francisco, USA). The 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 over-treating patients diagnosed with DCIS, according to a lead study author Naomi Boekel, MSc, a PhD-student at the Netherlands Cancer Institute in Amsterdam, Netherlands. However, studies with longer follow-up after breast radiation therapy are needed before definitive conclusions.

DCIS is a precursor of breast cancer, and if left untreated, may progress to invasive breast cancer. DCIS is typically treated with surgery. In the past, many women with DCIS underwent mastectomy but today the majority undergo lumpectomy. Following a lumpectomy, many women nowadays also receive radiation therapy, which approximately halves the rate of cancer recurrence in the same breast. Previous studies in breast and other cancers, however, have shown that radiation to the heart region can increase long-term risks of cardiovascular disease, so in recent years doctors have adjusted protocols to decrease exposure of the heart to radiation.

Researchers collected data on 10,468 women in the Netherlands diagnosed with DCIS before the age of 75 years between 1989 and 2004. About 71% of women were treated with surgery alone (of whom 43% underwent mastectomy and the rest underwent lumpectomy) and 28% were treated with surgery and radiotherapy. The median follow-up period was 10 years and about 19% of women were followed for 15 or more years. Risk of cardiovascular disease was compared to that of the general population of Dutch women. Additionally, comparisons were made between different treatment groups.

After a median follow-up of 10 years, DCIS survivors had a similar risk of dying of any cause but a 30% lower risk of dying from cardiovascular disease compared to the general population of Dutch women. No differences in cardiovascular disease risks were found between patients who received surgery alone and those that received surgery plus radiation (9% of patients treated with surgery alone vs. 8% of the patients treated with surgery plus radiation were diagnosed with a cardiovascular disease), or between patients who received left- vs. right-sided radiotherapy (7 vs. 8% of the patients were diagnosed with a cardiovascular disease).

The authors stated that the fact that DCIS survivors had a slightly lower risk of dying from cardiovascular disease might be due to those women being more health conscious than women in the general population, which possibly prompted them to undergo breast cancer screening or that they assumed a healthier lifestyle after DCIS diagnoses. Education, socioeconomic status, or conflicting risk factors between cardiovascular disease and DCIS, such as age at menopause, may also play a role.