One in four women who undergo breast-conserving surgery to remove cancer will be called back for more surgery, a new study finds.
Moreover, the chance that a woman will have additional surgery varies greatly depending on where she gets it done and the surgeon that performs it, the researchers said. This suggests that some of these surgeries are unnecessary.
Because each surgery takes a physical, psychological and economic toll on patients and affects the course of cancer therapy, doctors need to come to better agreement on which patients require additional surgery and which do not, said study researcher Dr. Laurence McCahill, a surgeon at Michigan State University.
The study will be published tomorrow (Feb. 1) in the Journal of the American Medical Association.
About 60 to 75 percent of breast cancer patients undergo a partial mastectomy, which aims at conserving as much breast tissue as possible while still removing the tumor.
After an operation, doctors examine the edges of the excised tissue under a microscope, looking for clues as to whether they "got it all." If cancerous cells are found all the way up to the edge of the removed tissue, known as "positive margins," then it could be that some cancer is still inside the patient and she may require more surgery.
On the other hand, doctors can feel more comfortable that the cancer was completely removed if they see "negative margins," meaning there is a border of normal tissue, completely free of cancer cells, around the cancer they removed.
Exactly how big this border needs to be to prevent recurrence of the cancer is not known. And doctors can't tell at the time of surgery whether the margins on the tumor are positive or negative. "Our eyes are not microscopes," McCahill said.
McCahill and colleagues analyzed information from 2,206 women with invasive breast cancer who underwent a partial mastectomy at four hospitals between 2003 and 2008.
Of these, about 23 percent (509 patients) underwent re-excision surgery.
Surgeons seemed to agree that patients needed additional surgery if the tissue removed from them had cancer cells up to its edges — of these patients, 85.9 percent had re-excision surgery.
However, among patients with clear borders of cancer-free tissue, the chance that they had additional surgery varied greatly. Some surgeons performed repeat surgeries for 70 percent of their patients; others never did re-excisions for these patients.
That may be because surgeons differ in how big of a cancer-free border they want their patients to have. Some may feel comfortable with a 1-millimeter border of cancer-free tissue, while others want a larger border, perhaps 2 or even 5 millimeters, and so would re-operate on patients with smaller borders.
There is "no evidence" that these repeat surgeries prevent cancer from coming back, or bring longer lives for patients, said Dr. Monica Morrow, chief of breast surgery at Memorial Sloan-Kettering Cancer Center in New York City, who was not involved in the study.
In the absence of data indicating the benefit of repeat surgeries, a number of women may be having additional surgery unnecessarily, Morrow said.
If doctors accepted any cancer-free border as adequate and did not aim for a specific size border, the number of re-excisions could be significantly reduced, Morrow said.
More studies are needed to see if bigger margins do in fact provide a clinical benefit, Morrow said.
Pass it on: The chance that a woman will require additional breast cancer surgery to remove more of the tumor varies widely, depending on where she has the surgery done.
Live Science newsletter
Stay up to date on the latest science news by signing up for our Essentials newsletter.
Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.