HAMBURG, GermanyRadiotherapy for breast cancer increases the risk of
death from cardiovascular disease (CVD), compared with patients who did not
receive such treatment, according to data from a large retrospective cohort
study. Maartje Hooning, MD, a clinical epidemiologist from the Netherlands
Cancer Institute, Amsterdam, and lead investigator of this study, presented
the findings at the 4th European Breast Cancer Conference (abstract 291).
Dr. Hooning’s research team studied data from 7,247 patients with early
breast cancer, who ranged from 17 to 71 years of age. These patients had been
treated for stage I-III breast cancer and had been admitted to the
Netherlands Cancer Institute or the Daniel den Hoed Cancer Center in
Rotterdam between 1970 and 1987. Patients have been followed for a median of
14 years, and 34% have been followed for more than 20 years. For 92% of the
patients, a complete medical status was available up to January 1998.
The investigators compared mortality from cardiovascular disease in patients
receiving radiotherapy and nonirradiated patients. The study population’s
cardiovascular mortality rates were than compared with those of the general
female population. The team also clearly documented the sites of the radiation
Compared with the general female population, the number of cardiovascular
deaths in the study population was within the normal range of expectancy.
Further analysis showed a 2.2-fold increase in cardiovascular deaths among
patients who had received radiotherapy, compared with those who had not (range
of risk, 1.4 to 3.6). "In terms of absolute excess risk, this means 12 extra
cardiovascular deaths per 10,000 irradiated patients per year," Dr. Hooning
The nonirradiated group actually had a significantly lower cardiovascular
mortality at 0.6-fold (range, 0.3 to 0.8) than the general female population,
suggesting that the risk profile for breast cancer is protective against
cardiovascular disease. Dr. Hooning explained this apparent anomaly by saying
that a healthier life style after breast cancer may play a role.
"When you analyze the data, it is not such an unexpected development after
all," Dr. Hooning said. "Breast cancer is linked with a higher socioeconomic
status, which is associated with better nutrition, a lower risk of
hypertension, and less obesity. So, as a result, breast cancer patients might
indeed have a lower risk profile for cardiovascular disease." The diagnosis of
cancer may also have led patients to improve their lifestyle. "Stopping smoking
and losing weight through exercise and a healthy diet may contribute to the
lower cardiovascular mortality rate," Dr. Hooning said.
The radiation-related risk increased dramatically among patients who had
more than 10 years of follow-up. Patients treated before the age of 45 had an
even greater radiation-related increased CVD risk [Standardized Mortality Ratio
(SMR) = 2.6]. This increased risk is thought to be caused by the lower
background risk of CVD in younger woman, compared with older woman.