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Radiation therapy for DCIS did not increase risk for cardiovascular disease
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Women who underwent radiation therapy for ductal carcinoma in situ of the breast demonstrated no additional risk for cardiovascular disease, according to results of a large population-based study presented at the Breast Cancer Symposium.
“We know from previous studies that radiation to the heart increases the risk for cardiovascular disease; however, the radiation to the heart during treatment of ductal carcinoma in situ is relatively low,” Naomi B. Boekel, MSc, a PhD student Netherlands Cancer Institute in Amsterdam, said during a press conference. “Therefore, the question is raised whether ductal carcinoma in situ patients treated with radiation therapy are at increased risk for cardiovascular disease.”
Boekel and colleagues evaluated data from 10,468 patients in the Netherlands diagnosed with ductal carcinoma in situ (DCIS) from 1989 to 2004. All patients were aged younger than 75 years at the time of diagnosis.
The researchers used population registries to obtain data on cardiovascular disease (CVD) morbidity and mortality.
Median follow-up was 10 years.
Results showed 5-year survivors of DCIS had similar all-cause mortality rates (standardized mortality ratio [SMR]=1.04; 95% CI, 0.97-1.11) and a reduced risk for mortality from CVD (SMR=0.77; 95% CI, 0.67-0.89) compared with women in the Netherlands’ general population.
“This lower risk might be due to lifestyle adaption after DCIS diagnosis or conflicting risk factors between DCIS and CVD, such as age at menopause,” Boekel said. “Or, it could be due to differences in health consciousness. We think DCIS patients are probably more health conscious than the general population.”
Researchers also found the risk for mortality from CVD was not statistically different between women with DCIS who underwent radiation therapy compared with those who were treated with surgery only.
In addition, patients who received left- vs. right-sided radiotherapy had similar CVD outcomes (HR=0.93; 95% CI, 0.67-1.30). Differentiating between these treatment groups in a subgroup of patients diagnosed with DCIS between 1997 and 2005 did not produce statistically significant results (HR=0.95; 95% CI, 0.69-1.30).
Patients diagnosed with CVD 2 years before DCIS diagnosis demonstrated an increased risk for mortality from CVD (HR=1.84; 95% CI, 0.45-7.50), but the difference was not statistically significant, according to researchers.
“Doctors have been worried about the late effects of breast radiation therapy, particularly cardiovascular disease,” Boekel said in a press release. “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 with DCIS. However, studies with longer follow-up after breast radiation therapy are needed before definitive conclusions about cardiovascular disease risk can be drawn.”
Disclosure: The researchers report no relevant financial disclosures.
For more information:
Boekel NB. Abstract #58. Presented at: Breast Cancer Symposium; Sept. 7-9, 2013; San Francisco.
Perspective
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Steven O’Day, MD
This is an important study for a number of reasons. A mainstay of trying to reduce mortality from breast cancer has been increasing screening on a number of fronts. Screening picks up both invasive and noninvasive cancers. Some noninvasive cancers, or DCIS cancers, will — if left untreated — progress to invasive cancer, but we’re not absolutely sure in what percentage this would occur. We are very aggressive with treatment in DCIS in terms of surgical resection and then radiation therapy if breast conservation is attempted to control the DCIS. There’s been concern for any morbidity and mortality related to treatment, particularly to radiation therapy. Older radiation studies clearly showed a correlation between radiation and cardiovascular toxicity when the fields were overlapping with the heart. Radiation therapy has been refined over the years.
A strength of this study was that this was a large cohort study from the Netherlands over 15 years, occurring relatively recently from 1989 to 2004, so it accounts for the more modern techniques of radiation therapy. Then there was a healthy follow-up of 10 years, although we will need to follow this cohort longer to be able absolutely sure.
What’s reassuring about this study is that, with aggressive radiation therapy for DCIS, there was not an increased risk for death overall — and, in particular, there was not an increased risk for cardiovascular death. In fact, there was a decreased risk for cardiovascular death in the radiated patients, although this may be unrelated to the radiation as there may be other factors and lifestyle changes that may explain this decrease. But most importantly, there does not appear to be an increased risk for overall mortality, and specifically, cardiovascular mortality. This is an important study that allows us to feel comfortable continuing our aggressive treatment of DCIS with efforts of screening and trying to reduce overall mortality from breast cancer.
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