The findings are the final conclusions of a pair of NSABP studies that began in the mid-1980s and early 1990s to compare the effectiveness of breast-conserving surgery alone with surgery plus additional cancer-fighting treatments. They are a reassuring confirmation that lumpectomy plus additional treatments can be a safe, effective way to combat some types of breast cancers.
“Now we can see the natural history of this disease in a large patient population over a period of up to two decades,” said associate professor of surgery Irene Wapnir, MD, chief of breast surgery at the Stanford Cancer Center. “These are landmark trials with mature data.”
Wapnir is the lead author of the research, published online March 11 in the Journal of the National Cancer Institute. The NSABP is an NCI-sponsored cooperative oncology group headquartered in Pittsburgh. It is known for conducting large clinical trials comparing treatments for breast and colorectal cancers. The senior author of the research is Norman Wolmark, MD, professor of human oncology at the Drexel University College of Medicine.
Long-term survival statistics for any study by definition take years to compile. During the intervening time, the standard of care can change dramatically. However, lumpectomy, which removes only a portion of the breast, has continued to be favored as a way to treat the cancer within the breast while preserving a woman’s appearance.
Ductal carcinoma in situ, or DCIS, describes the presence of cancerous cells inside the lining of the milk ducts of the breast. Because the cells are confined to the duct and have not spread to other breast tissue, the condition rarely causes a palpable lump. It is primarily diagnosed through mammography, and the increasing use of this cancer-screening technique is likely why DCIS or stage-0 breast cancer accounts for about 25 percent of all newly diagnosed breast cancers today. Women with DCIS have an increased risk of invasive breast cancer.
One of the two studies included in Wapnir’s recent analysis included the NSABP B-17 trial, which enrolled 813 women with DCIS during October 1985 and the end of 1990 to randomly receive either a lumpectomy alone or a lumpectomy followed by radiation therapy. Five-year outcomes (first reported in 1993), demonstrated that women who received radiation therapy had a 60 percent lower risk of experiencing tumor recurrence in the same breast within that time period.
The B-24 trial enrolled 1,799 women between May 1991 and April 1994 to investigate whether the addition of the cancer-fighting drug tamoxifen to the lumpectomy and radiation treatment would be beneficial. The study found that women who received tamoxifen experienced a 31 percent reduction in risk of tumor recurrence compared with those who received lumpectomy and radiation alone.
The current study looked at the trial participants approximately 15 years after their initial diagnosis to determine the long-term risk of invasive cancer in the same breast. It found that 19 percent of the women who received a lumpectomy alone went on to develop invasive breast cancer, but only 8.5 percent of the women who also received radiation therapy plus tamoxifen did so. However, although women with subsequent invasive cancers did have a higher mortality rate than those who did not develop the cancers, the overall risk of death from breast cancer during the 15-year period was relatively low: 4.7 percent or less across all treatment arms.
“Critics will point out that the majority of patients with lumpectomy alone didn’t have a recurrence. We were not able to identify a group that did not benefit from either radiation or radiation plus tamoxifen,” said Wapnir. “I tell my patients when discussing treatment options that I don’t know how to identify which patients will be in that category.”
Wapnir pointed out that the women enrolled in the two studies had relatively small DCIS tumors, and that the study findings might not apply to a woman diagnosed today with a larger tumor or with other complicating factors.
“A mastectomy may still be indicated in a woman with a very large DCIS,” said Wapnir, who pointed out that ongoing studies testing specific molecular markers in DCIS or investigating the efficacy of partial breast radiation may define new treatment strategies in the near future. “In the end, we want to treat each patient in such a way as to minimize the chance of that woman developing a subsequent invasive cancer,” she said.
The study was supported by the Public Health Service and the National Cancer Institute. Tamoxifen for the trials was provided by AstraZeneca. More information about the Department of Surgery, which also supported this research, is available at http://surgery.stanford.edu.
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