Despite advances in breast cancer detection and treatment that have helped many women keep more of their own breast tissue, in about 40 percent of cases, U.S. surgeons re-operate to get a cancer-free margin.
The optimal size of the "clean margin" – a rim of healthy tissue beyond the tumor – was a hot topic at last week's annual meeting of the Society of Surgical Oncology in Orlando, Fla., especially in the most survivable breast cancer, ductal carcinoma in situ (DCIS).
As they debated surgical margins , the Journal of the National Cancer Institute published a review of 21 DCIS studies dating to 1970, from which University of Minnesota public health researchers concluded that surgeons should aim for "margins as wide as possible" for all DCIS. In an accompanying commentary, co-author Dr. Monica Morrow, chief of the breast cancer service at Memorial Sloan-Kettering Cancer Center in New York, called the study conclusion surprising and "a major change in the current standard surgical approach to DCIS."
Morrow, who on Friday became president of the Society of Surgical Oncology, said only five of the reviewed studies reported using margins of at least 10 millimeters (slightly more than a third of an inch). "Any net benefit of more widely clear margins on the overall health of women with DCIS would be extremely small or negligible," she said.
Morrow suggested research could be better directed toward "identifying those factors that result in the progression of DCIS to invasive cancer," which she called critical to tailoring treatment.
Although the rate of invasive breast cancer diagnoses has dropped since 2000, likely reflecting reduced hormone replacement therapy, the number of annual DCIS diagnoses has risen steadily to 60,000, from 4,900 in 1983, before widespread screening.
"It's not that it's become an epidemic," but that digital mammograms and MRIs are picking up more DCIS at a smaller, earlier stage, said Dr. Mehra Golshan, the director of breast surgical services at the Dana-Farber Cancer Institute in Boston, who was not involved in the JNCI study.
Regardless of whether a DCIS patient chooses lumpectomy followed by radiation, lumpectomy alone, mastectomy or nipple-sparing mastectomy, "survival is over 98 percent," Golshan said in an interview from the Orlando meeting. Rates of DCIS recurrence in the same breast range from less than 1 percent after mastectomy to 5 to 6 percent after lumpectomy plus radiation--which destroys microscopic cancer cells doctors cannot see, he said. With estrogen-positive DCIS, tamoxifen can further reduce that rate. As a result "you may not need an exact millimeter number to say what a clear margin is."
Target surgical margins vary, with institutions aiming for 2, 3, 5 or 10 millimeters of clean tissue, none demonstrated "specifically better than the others," Golshan said.
At Dana-Farber, "we like 3 mm. Massachusetts General across the street likes 2 mm. What our pathologists would consider 'clear' is a millimeter different." Both institutions do good surgery and care, he said.
Golshan called a 10 mm margin "way too much" for DCIS patients, who likely will live long enough to die from some other condition like heart disease. A 10 mm margin may take away so much of the breast -- as much as half -- that it defeats the goal of breast conservation, he said.