Conflicting Studies on Radiation for Breast Cancer
A controversial article in the British medical journal The Lancet recently trumpeted that the risks from radiation therapy may sometimes outweigh its benefits for certain breast cancer patients. This conclusion pertained to women who are at low risk for recurrence-especially older women whose cancer has not spread to their lymph nodes. However, this limiting caveat was lost on many women in the subsequent wash of media attention.
In fact, for most other breast cancer patients, the article further confirmed the benefits of radiation therapy. And new studies published in the past few months have added additional weight to the clinical body of research supporting radiation therapy for breast and other cancers
The British study, led by Dr. Rory Collins of the Clinical Trial Service Unit at Radcliff Infirmary in Oxford, evaluated 40 randomized radiotherapy trials that involved 19,582 women. All of the trials began before 1990.
Overall, the researchers found that radiotherapy for breast cancer resulted in a dramatic reduction in local recurrence. Collins noted that this preventive benefit was more significant for younger women with node-positive cancers (cancers that had spread to the lymph nodes).
During the first two years after treatment, mortality rates were comparable for women who received or did not receive radiation therapy. However, after that, the annual breast cancer mortality was about 13 percent lower in women who had undergone radiotherapy.
Nonetheless, the researchers found that while radiation therapy significantly reduced deaths from breast cancer, this "cancer benefit" may have been offset by other factors, resulting in only a minor difference in overall survival-about 1 percent-after 20 years. The reason, they speculated, "appeared chiefly to involve an excess of vascular deaths, perhaps due to inadvertent irradiation of the coronary, carotid or other major arteries."
However, in an accompanying editorial, Dr. John Kurtz of University Hospital in Geneva, Switzerland, cautioned that the radiation techniques used today differ greatly from those used in the pre-1990 studies that were evaluated by Collins' group. Major advances in radiation technology are now minimizing the risk of vascular damage, he said.
"Clinicians should not be dissuaded from continuing to favor conservation surgery and to provide patients with the advantages of breast irradiation," he wrote.
In contrast to The Lancet study, a report in the Journal of Clinical Oncology noted that local and regional radiation does improve survival, at least in women who undergo surgery and standard chemotherapy for breast cancer.
While previous studies have shown that radiation therapy prevents cancer from recurring, said Dr. Timothy Whelan of the Hamilton Regional Cancer Centre in Ontario, there has been little concrete research into its impact on long-term survival. To evaluate this impact, his team reviewed the results of 18 clinical trials that took place between 1973 and 1984. They included 6,367 women who underwent modified radical mastectomy for node-positive breast cancer. All of the women received systemic chemotherapy as well.
Radiation resulted in a 31 percent reduction in the overall risk of recurrence, they found, due largely to a 75 percent reduction in the risk of local recurrence. Importantly, the combined results showed that locoregional radiation was associated with a 17 percent reduction in mortality. Whelan's team concluded that radiation therapy, when combined with systemic chemotherapy, results in a "reduction in locoregional recurrence that may prevent secondary system spread from regional sites and thus prolong survival."
In a presentation at the recent annual meeting of the American Society of Clinical Oncology in New Orleans, Whelan further theorized that a shorter course of radiation for breast cancer may be just as effective as a longer one. He reported on a study involving 1,200 women, half of whom underwent radiation therapy 5 days a week for 3 weeks, while the other half received weekday radiation for the traditional 5-week schedule.
At the end of a five-year follow-up period, about 94 percent of the women on each schedule were still alive. Sixteen women on the shorter schedule had local breast cancer recurrence, compared with 17 on the longer schedule. This confirmed, according to Whelan, that the shorter treatment regimen was just as effective as the longer one. Furthermore, the total radiation dose for each patient was significantly reduced and the time impact on their daily lives was much less intrusive.
In another study published in the Journal of Clinical Oncology, researchers from the Yale University School of Medicine concluded that women with breast cancer who undergo lumpectomy followed by radiation do not have an increased risk of a second malignancy compared with women who undergo mastectomy without radiation.
In a study of 2,416 women with early-stage breast cancer, Dr. Bruce Haffty and colleagues found that the risk of developing a new cancer in the other breast during a 15-year follow up period was about 10 percent in both treatment groups. "These findings should be reassuring to women considering lumpectomy followed by irradiation as a treatment option," Haffty wrote. (Interestingly, the researchers found that smoking was a major factor resulting in an increased risk of a second malignancy.)
While some older women with node-negative breast cancer may want to weigh the benefits of radiation therapy with the risk vascular damage, new advances in radiation technology should make this decision more clear-cut. For the vast majority of women with breast cancer, however, radiation therapy remains an extremely effective-and safe-treatment option.
SOURCES:
The Lancet, May 20, 2000; 1739-1740, 1757-1770
Journal of Clinical Oncology, March, 2000; 18: 1220-1229
Journal of Clinical Oncology, June, 2000; 18: 2406-2412
American Society of Clinical Oncology (http://www.asco.org)
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