Recent concerns about potential overdiagnosis and overtreatment of ductal carcinoma in situ of the breast (DCIS) led researchers in the Netherlands to study late effects of treatment, such as cardiovascular disease, morbidity, and mortality in a large population-based cohort of DCIS patients. “After a median follow-up of 10 years, we did not find an increased risk for cardiovascular morbidity or mortality after radiotherapy for DCIS when comparing surgery and radiotherapy vs surgery only, nor when comparing radiotherapy for left-sided vs right-sided DCIS,” the investigators reported in the Journal of the National Cancer Institute. Patients with DCIS had a decreased risk of cardiovascular death, independent of treatment, when compared to the general population.
The researchers collected data on 10,468 women diagnosed with DCIS as their first neoplasia before the age of 75 years in the Netherlands between 1989 and 2004 and matched that data to cardiovascular disease data acquired through linkage with population-based registries. Patients were treated with surgery, either mastectomy or wide local excision. In the later years of the study, “wide excision [was frequently] followed by tangential breast field irradiation to a prescribed dose equivalent of 50 Gy in 25 fractions,” noted Naomi B. Boekel, MSc, of the Netherlands Cancer Institute, Amsterdam, and colleagues. “The percentage of DCIS patients treated with radiotherapy changed considerably during the study period, from 20% in 1989 to 46% in 2004.”
The median follow-up time was 10 years, but 8 years when restricted to patients who had received radiation. A total of 1,319 patients died and 2,214 were diagnosed with a second neoplasm during follow-up. Although 950 patients experienced cardiovascular events, only 684 events occurred 5 or more years after diagnosis, and 204 of those events were cardiovascular deaths.
When compared with the general population, 5-year survivors of DCIS had a similar all-cause mortality (standardized mortality ratio [SMR] = 1.04; 95% confidence interval [CI] = 0.97–1.11) but a lower risk of dying of cardiovascular disease (SMR = 0.77; 95% CI = 0.67–0.89). “No difference in [cardiovascular disease] risk was found when comparing 5-year survivors treated with radiotherapy with those treated with surgery only. Left-sided vs right-sided radiotherapy also did not increase this risk (hazard ratio [HR] = 0.94; 95% CI = 0.67–1.32),” the researchers reported.
“Importantly, radiotherapy after breast-conserving surgery for DCIS approximately halves the rate of ipsilateral breast events during the subsequent decade with little effect on contralateral or distant events,” the investigators concluded. “Although our results are reassuring, studies with longer follow-up after breast irradiation are needed before definitive conclusions regarding [cardiovascular disease] risk can be drawn.” ■
Boekel NB, et al: J Natl Cancer Inst 106(8):dju156, 2014.