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.

“Doctors have been worried about late effects of breast radiation therapy, particularly cardiovascular disease. 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 over-treating patients diagnosed with DCIS,” said lead study author Naomi B. 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 about cardiovascular disease risk can be drawn.”

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 percent of women were treated with surgery alone (of whom 43 percent underwent mastectomy and the rest underwent lumpectomy) and 28 percent were treated with surgery and radiotherapy.

The median follow-up period was 10 years and about 19 percent 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 percent 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 percent of patients treated with surgery alone vs. 8 percent 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 percent of the patients were diagnosed with a cardiovascular disease).

Source: ASCO