Most women who are diagnosed with breast cancer have surgery. How much of their breast is removed depends on a number of factors, and many women have the choice to undergo lumpectomy (also called “breast-conserving surgery” or “partial mastectomy”). With a lumpectomy, the surgeon removes only the tumor and a small amount of normal surrounding tissue. A majority of women who are diagnosed with breast cancer—up to 90% by some estimates—are candidates for lumpectomy followed by radiation (which reduces the risk of recurrence in the same breast.) The overall survival rates for these women are similar to those who choose mastectomy.
Following a lumpectomy, samples of the tissue removed during surgery are examined by pathologists. If no cancer cells are found at the edge of the tissue, it is said to have “clear” or “negative” margins. (Conversely, if cancer cells are found at the edge of the removed tissue, it is said to have “positive” margins.) For women in the U.S. who undergo lumpectomy, 20-40% have positive margins and doctors advise many of these women to have a second surgery to remove more tissue in an attempt to ensure negative margins. For women who are choosing breast-conserving surgery, the hope is to remove as little normal tissue as possible and because every surgery comes with risks, many women would like to avoid a second surgery.
A new study by the Yale Cancer Center presented at the 2015 Annual Meeting of the American Society of Clinical Oncology (ASCO) in Chicago explored the impact of removing more tissue all the way around the tumor site during the initial surgery, a practice called cavity shave margins (CSM). The goal is to avoid a second surgery by reducing the potential for positive margins. In this small study of 235 patients with breast cancer, patients who underwent a lumpectomy were randomized in the operating room to either have additional CSM removed or not. The results indicated that those patients with CSMs were half as likely to have positive margins.
However, there is a growing consensus that a second surgery is not necessary after most lumpectomies because the goal of surgery is not to eradicate every single cancer cell. While the Yale study focuses on the question of how much tissue is optimal to remove in a lumpectomy, the real-world impact of this study remains to be seen because it rests upon whether finding some residual cancer cells after lumpectomy justifies a second surgery, and by extension whether it’s necessary to remove more healthy tissue during the initial surgery.
As Dr. Susan Love so clearly makes clear in a recent Facebook post:
“The story in the news about breast cancer surgery is misleading. After a lumpectomy, showing clean margins, if surgeon takes out more tissue they can find microscopic cancer cells in the additional tissue. On first blush (the media rarely goes beyond first blush) this sounds like you should have more tissue removed. The key, however, is that the goal is NOT removing ALL of the breast cancer prior to radiation therapy but most of it. The goal of the radiation therapy is to take care of those microscopic cells. We have long term data showing that it does exactly that! This study focused on the wrong endpoint!”
In early 2014, a multidisciplinary panel of breast cancer experts released results from a review of the available scientific evidence. After a systematic review of 33 studies that included 28,162 patients, the recommendation was against re-excision, or performing a second procedure following lumpectomy. This consensus recommendation found that removing additional tissue did not significantly decrease the risk of recurrence in the same breast. This guideline has been expected to save patients from unnecessary surgery while still minimizing the risk of the cancer returning.