Radiation for DCIS Does Not Up CV Disease at 10 Years

Encouraging but Not Definitive

Nick Mulcahy

September 05, 2013

Women with ductal carcinoma in situ (DCIS) who receive radiation therapy do not have an increased risk for cardiovascular disease or related death, according to the first-ever large-scale study of this clinical issue.

The Dutch study involved more than 10,000 women with DCIS and had a median follow-up of 10 years.

The study investigators compared rates of cardiovascular disease and mortality in women treated with radiation and surgery for their DCIS with rates in the general population of Dutch women. They also compared rates in women treated with different regimens in the DCIS population.

The results are encouraging but are not the final word on these risks, said lead author Naomi B. Boekel, MSc, a PhD student at the Netherlands Cancer Institute in Amsterdam.

"I think we need another 5 to 10 years before we are sure," she said about the lack of relation between cardiovascular disease and radiation for DCIS.

Boekel spoke to reporters yesterday at a presscast that preceded the 2013 Breast Cancer Symposium, which is being held this week in San Francisco. The presscast was organized by the American Society of Clinical Oncology (ASCO), which is sponsoring the symposium along with 5 other professional bodies.

Boekel pointed out that radiation to the breast sometimes overlaps with the heart area. In the past, this has been shown to increase the risk for cardiovascular disease. However, the radiation currently used to treat DCIS is "relatively low," compared with that used in the past and that used for invasive disease, she explained.

Nevertheless, cardiovascular disease is one of the potential late effects of radiation to a breast with DCIS, she said, and has come into sharper focus because of the growing general concern about the overtreatment of DCIS.

The study results are "reassuring," said Steven O'Day, MD, from the Beverly Hills Cancer Institute in Los Angeles, who moderated the presscast. He is also an ASCO spokesperson.

Dr. O'Day pointed out that "we are very aggressive" in treating the approximately 64,000 new cases of DCIS in the United States each year with available therapies, including radiation, because of the "uncertainty" about which patients will progress to invasive disease.

He highlighted the fact that patients in the study were diagnosed with DCIS between 1989 and 2004, which is "relatively recent" and in the era of more modern radiation therapy techniques.

DCIS Survivors Actually Have Lower Risk for Cardiovascular Mortality

The study investigators collected data on 10,468 Dutch women diagnosed with DCIS before the age of 75. Most (71%) were treated with surgery alone (43% with mastectomy and 38% with lumpectomy). A minority (28%) were treated with surgery and radiotherapy.

Although the median follow-up period is 10 years, nearly one fifth of the women have been followed for 15 or more years.

One of the surprises of the study is that DCIS survivors had a 30% lower risk of dying from cardiovascular disease than women in the general Dutch population. However, the 2 populations had a similar risk for all-cause mortality.

This lower mortality from cardiovascular disease might be explained by a number of factors, said Boekel. It might be due to lifestyle modification or a difference in health consciousness in women after a diagnosis of DCIS. Or it might be from conflicting risk factors, such as age at menopause, for DCIS and cardiovascular disease, she said.

In terms of the treatments studied, radiotherapy did not increase the risk for cardiovascular disease. There was no statistically significant difference in risk between patients treated with surgery alone and those treated with surgery and radiation (9% vs 8%).

The investigators also looked at the side of the body that received radiation, because left-sided radiation is closer to the heart and could be more risky. However, there was no significant difference. In fact, patients who received left-sided radiotherapy had a slightly lower rate of cardiovascular disease than those who received right-sided therapy (7% vs 8%).

Boekel hasd disclosed no relevant financial relationships. Dr. O'Day reports acting as consultant or advisor for Bristol-Myers Squibb, Delcath, Eisai, Genentech, GlaxoSmithKline, and Roche; accepting honoraria from Bristol-Myers Squibb; and receiving research funding from Bristol-Myers Squibb, Eisai, GlaxoSmithKline, Lilly, and Roche/Genentech.

2013 Breast Cancer Symposium: Abstract 58. To be presented September 7, 2013.

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