(dailyRx News) During breast cancer surgery, the surgeon takes some healthy tissue to make sure all the cancer is removed. The area between the tumor bed and healthy tissue is known as the margin, a key outcome measurement.
Ductal carcinoma in situ (DCIS) are breast cancers that are contained and have not invaded nearby tissue. New research suggests that negative margins, where no cancer cells are found, should be wide - 10mm - following DCIS lumpectomies to limit risks of the cancer returning.
Margins after breast conserving surgery (BCS) are characterized as follows:
- Negative, clear or clean – no cancer cells are seen at the outer edge of the removed tissue
- Positive – cancer cells are right at the edge of the tissue removed and may require more surgery
- Close – cancer cells are close to the edge, but not right at the edge, and could mean more surgery
Patrick D. Maguire, M.D., a radiation oncologist in North Carolina, told dailyRx, "The goal of breast conservation surgery with DCIS or invasive breast cancer is to remove tumor with 'negative surgical margins' (no tumor at inked edge of specimen), while retaining the optimal cosmesis for the patient."
In this meta-analysis study, led by Shi-Yi Wang, M.D., MS of the Division of Health Policy and Management at the University of Minnesota School of Public Health, researchers sought to determine the link between different width margins and local recurrence of breast cancer.
The women with DCIS were divided into two groups - BCS with radiotherapy or BCS without radiotherapy.
Researchers found 21 studies involving 7,564 patients treated over 25 years that linked wider margins with lower risk of the breast cancer returning in the same breast, a condition known as ipsilateral breast tumor recurrence (IBTC). Radiotherapy didn't impact these findings.
Margins of at least 10mm were associated with even smaller risks of recurrence, regardless of whether or not radiation therapy was given after surgery.
The authors conclude from these findings suggest that radiation can't be relied upon to be sufficient to overcome the possible dangers of positive margins.
They add that "given that BCS is subject to cosmetic constraint and not all surgeries can guarantee 10mm free margins, RT should always be considered the top priority."
Dr. Maguire says, "More widely negative surgical margins indicate that the residual microscopic tumor burden after surgery is low. However, Wang and co-authors are correct in warning readers about the hazards of placing too great a faith in 'widely negative' surgical margins (5mm, 1cm, more?)," said Dr. Maguire, who is the author of When Cancer Hits Home: An Empowered Patient is the Best Weapon Against Cancer.
He adds, "Postoperative RT (radiotherapy) remains the standard of care for the best chance for cure, based on randomized clinical trials, the best available medical evidence."
An accompanying editorial points out study limitations and potential biases. "In any observational study, there is concern that the results could be influenced by important confounding factors. This is a particularly challenging problem in this meta-analysis incorporating the results of many observational studies where patients were not randomly assigned to the different margin widths," write Monica Morrow, M.D., of the Department of Surgery at the Memorial Sloan-Kettering Cancer Center and Steven J. Katz, M.D., MPH, of the Department of Medicine and Health Management and Policy at the University of Michigan.
They say that another study disputes these findings and that making 10mm a standard may preclude women with DCIS having lumpectomies at all, and would likely increase the need for additional surgeries to achieve these margins.
This meta-analysis was published March 22, 2012 in the Journal of the National Cancer Institute.
The Agency for Healthcare Research and Quality, US Department of Health and Human Services funded this research.
The authors declare no conflict of interest.