Still, both treatments work well, with about 93% of 62,770 women who had lumpectomy followed by radiation -- and 87% of 51,507 women who had a mastectomy -- alive more than four years after diagnosis.
"We found that lumpectomy followed by radiation therapy is very safe for women of all ages with early-stage breast cancer," says E. Shelley Hwang, MD, MPH, a breast cancer surgeon at the University of California, San Francisco.
Studies done over two decades ago established breast-conserving therapy (BCT) as a standard option for women with early breast cancer, showing it worked just as well as mastectomy.
Since then, other studies suggested that certain women -- those who have not yet reached menopause and those whose tumors are not fueled by hormones -- may be slightly more likely to have a recurrence if they have breast-conserving therapy than if they have mastectomy, Hwang tells WebMD.
As a result, more and more women are choosing mastectomy these days, she says.
"Our question was, is there a difference in survival when breast-conserving therapy and mastectomy are performed using modern techniques?" Hwang says. "The results were the opposite of what we expected."
BCT beat out mastectomy regardless of whether a woman was under 50 or over 50 and regardless of whether the tumor was fueled by hormones, the study showed.
The findings were presented at the San Antonio Breast Cancer Symposium.
Breast-Conserving Therapy vs. Mastectomy
Using the California Cancer Registry, Hwang and colleagues reviewed the records of women diagnosed with early-stage breast cancer between 1990 and 2004 who were treated with either BCT (lumpectomy plus radiation) or mastectomy.
About one-fourth of the women were younger than 50 when they were diagnosed and 82% had hormone-receptor-positive tumors. The women were followed for about nine years, on average.
Results showed that:
Among women who were under 50 and had hormone-driven tumors, those who had BCT were about 12% less likely to die than those who had mastectomy.
Among women who were under 50 and had hormone-receptor-negative tumors, those who had BCT were 13% to 29% less likely to die than those who had mastectomy, depending on tumor size.
Among women who were 50 and over and had hormone-driven tumors, those who had BCT were about 20% less likely to die than those who had mastectomy.
Among women who were 50 and over and had hormone-receptor-negative tumors, those who had BCT were about 17% less likely to die than those who had mastectomy.
All the analyses took into account race, the size and aggressiveness of the tumors, and whether the cancer had spread to the lymph nodes.