The battle rages on in the war against breast cancer, and yet every day we learn more about how to effectively combat the enemy. By capturing structured data, physicians are able to more efficiently and precisely research the methods and outcomes of treatment. By studying the results of the past, we are able to have a better understanding of our present, and make more accurate predictions of our future. Thus are we able to know the efficacy of certain surgical approaches, or medicinal routines, or radiation schedules, and in what combination can we best hope to treat the patient successfully. Using 33 studies from 1965 to 2013 that covered 28,160 women, the American Society for Radiation Oncology (ASTRO) and the Society of Surgical Oncology (SSO) have issued new guidelines that change the standard of care for lumpectomies.
Lumpectomy is a procedure performed to treat breast cancer — part of the breast containing the tumorous cells is excised, along with a rim of healthy tissue around it to ensure that all of the disease has been taken out. There are approximately 160,000 lumpectomies performed every year in the United States, as about 60-70% of breast cancer patients elect to have this breast conserving surgery instead of mastectomy (in which the vast majority of breast tissue is removed). One critical aspect of the lumpectomy is the discussion of "margins" — that is, the rim of healthy tissue around the cancer being taken out. As breastcancer.org expertly explains:
The tumor and surrounding tissue is rolled in a special ink so that the outer edges, or margin, are clearly visible under a microscope.
During or after surgery, a pathologist looks at the tissue that’s been removed to make sure there are no cancer cells in the margin. A clear, negative, or clean margin means there are no cancer cells at the outer edge of tissue that was removed. A positive margin means that cancer cells come right out to the edge of the removed tissue and have ink on them. In some cases, a pathologist may classify the margins as close, which means that cancer cells are close to the edge of the healthy tissue, but not right at the edge and don’t have ink on them.
There has been debate as to how wide these margins have to be in order to feel confident that all of the cancer was removed. For if some of the tumor has been left behind, it will begin to grow again in the breast and lead to re-excision or complications for the patient. Some physicians feel that the size of the margins isn't as important as the fact that there is no ink on the tumor. Others believe that the margins should be more than 2mm in order to be secure that no aspect of the tumor was missed and allowed to regrow in the breast. Other medical personnel have different numbers that they are comfortable and believe is 'safe' enough for the patient.
ASTRO and SSO, based on all of those studies and decades of data, have weighed in on this discussion and issued new guidelines on how physicians should proceed. When taking margins, the most important aspect is that they are clear, not how wide (or narrow) those margins are. That means that as long as there's no ink on the tumor, then the surgeon is adhering to the guidelines. Furthermore, the two societies concluded that there is no evidence that a wider margin has any bearing on reducing the likelihood of recurrence of cancer. The societies have published other, fascinating findings from their review of these studies — like adjuvant treatments after surgery reduce the risk of recurrence in that same breast — that you should read about further. But this particular conclusion will help shape the behavior and approach of physicians (surgeons, pathologists, oncologists) as well as the treatment patients receive for many years to come.