Women receiving radiation for breast cancer may no longer face an increased risk of potentially deadly heart damage from the treatment.
More than 40 percent of women with breast cancer undergo radiation following surgery.
Studies in the 1970s indicated that radiation therapy for breast cancer also exposed the heart to radiation and increased the woman’s long-term risk of dying from cardiac disease. Radiation was kept in use because the benefit of reduced cancer recurrence was greater than the heart risk.
Over the years radiation therapy has been improved to deliver doses much more accurately, and a new study, published in Wednesday’s Journal of the National Cancer Institute, indicates the heart risk has been sharply reduced, perhaps eliminated.
'Radiation is safe'
“I would like this to be reassuring to women with breast cancer who are going to receive radiation, that radiation is safe,” lead researcher Dr. Sharon Giordano of the University of Texas M.D. Anderson Cancer Center said in a telephone interview.
Giordano and colleagues studied the records of women treated for breast cancer between 1973-1979, 1980-1984 and 1985-1989. Long-term follow-up is needed because the effects of radiation on the heart may not show up for more than a decade.
The researchers compared 13,998 women with cancer in the left breast — near the heart, meaning treatment could potentially expose the heart to more radiation — to 13,285 women with cancer in the right breast.
They found that among the women treated in the 1970s the 15-year death rate for heart disease in women with left-breast cancer was 13.1 percent, compared with 10.2 percent for those with right-breast cancer.
For the group treated in the early 1980s the heart death rates fell to 9.4 percent for left-breast cancer and 8.1 percent for right-breast cancer.
And by the late 1980s, 5.8 percent of women with left-breast cancer died of heart disease within 15 years compared with 5.2 percent with right-breast cancer, nearly eliminating the difference between the groups.
Heart disease is No. 1 killer
While the study does not compare rates with women who did not have radiation, heart disease remains the No. 1 cause of death in women overall.
In 1989 the death rate for heart disease in women age 20 and over was 397 per 100,000, according to the Centers for Disease Control and Prevention. Projecting that over 15 years would result in an overall death rate of 5.79 percent.
Jack Cuzick of Cancer Research-UK in England, who was not part of the study team, commented in an accompanying editorial that the converging heart death rates strongly indicate that the excess heart risk from radiation is being eliminated.
“Radiotherapists have heeded this call,” Cuzick said, though he urged follow-up research to make it clear if the excess risk has been completely eliminated.
Giordano’s research was supported by the National Institute of Health.
In a separate study in the same issue of JNCI, a team of researchers led by Dr. Rowan T. Chiebowski of the Los Angeles Research Institute in Torrance, Calif., report that rates of breast cancer for most minority women are lower than for white women, but that despite the lower rates, black women are more likely to die from the cancer.
Several factors may contribute to this higher mortality, including poorer socio-economic status with reduced access to health care, lower frequency of mammography with delayed diagnosis and reduced chemotherapy.
In addition, the researchers noted that black women were nearly twice as likely as white women to be obese and they had a higher rate of more aggressive cancers than whites. They urged further study to determine if genetic differences also are a factor.