Margin Width the Key to Controlling DCIS of the Breast

Patients with one of the most common and curable forms of breast cancer may be undergoing radiation therapy unnecessarily, according to a University of Southern California (USC) study published in the May 13, 1999, issue of The New England Journal of Medicine. The study, headed by Melvin J. Silverstein, MD, medical director of the Harold E. and Henrietta C. Lee Breast Center at the USC/Norris Comprehensive Cancer Center, examined ductal carcinoma in situ (DCIS).

At present, DCIS accounts for as many as 40% of new breast cancer cases diagnosed by mammography, and estimates suggest that approximately 40,000 new cases of DCIS will be diagnosed in 1999 in the United States. Of these patients, 70% to 80% are eligible for lumpectomy rather than mastectomy, but opinion on whether radiation therapy is necessary for all DCIS patients who choose lumpectomy is currently divided.

Margin Widths Govern Need for Radiation Therapy

In the article, Dr. Silverstein, a surgical oncologist, and his colleagues found that radiation therapy does not appear to benefit patients in whom the margin width is 10 mm or more. “Wide margin width makes complete excision more likely,” said Dr. Silverstein. “Since DCIS is a noninvasive cancer that does not spread, complete excision should cure the patient. These findings will have important ramifications for thousands of women with the disease. These data suggest that radiation therapy may not be the best option for some subgroups of patients with DCIS who choose to preserve their breast.”

The USC data, which were derived from an analysis of 469 patients choosing breast preservation, suggest that eradication of the cancer can be achieved when margin widths are sufficiently wide. For the purposes of the study, tumors were divided into three groups by margin width: close or involved (< 1 mm), intermediate (1 to < 10 mm), and wide (³ 10 mm).

“The fact that there were only 3 recurrences among 133 patients with 10 mm or greater margins makes it unlikely that radiation therapy could have any significant impact on this subgroup,” said Dr. Silverstein.

When the margin widths are less than 10 mm, radiation therapy should remain a treatment option. The benefit of radiation therapy increases as the margin width decreases, so that patients in whom the margin width is less than1 mm benefit the most from postoperative radiation therapy. In the intermediate margin width subgroup, there was an 8% reduction in local recurrence when postoperative radiation therapy was used, but the trend was not statistically significant, he said.

Redefining Patients Who Benefit From Radiation Therapy

Part of the controversy over treatment for DCIS stems from the fact that to date only one prospective, randomized study has been published—protocol B-17, conducted by the National Surgical Adjuvant Breast and Bowel Project (NSABP). That study strongly advocates excision plus radiation therapy for all patients with DCIS who elect to preserve their breast. This is a recommendation that Dr. Silverstein and colleagues consider too broad. “It is like treating every patient with an infection with antibiotics—it simply isn’t necessary,” said Dr. Silverstein.

“In defense of the NSABP, its trial was designed more than 14 years ago. At that time, researchers were asking a single broad question: Does radiation therapy benefit patients with ductal carcinoma in situ treated with breast preservation? The answer to that question is clearly, yes. However, the NSABP study was not designed to answer the more sophisticated and discriminating questions we ask today of exactly which subgroups might benefit from radiotherapy and by how much. If the benefit in a given subgroup is small, the advantage gained by radiation therapy will probably be more than offset by its cost and side effects,” he said.

Doctors must weigh the benefits of radiation therapy, in terms of a decrease in local recurrence, against the side effects, complications, inconvenience, and cost of radiation therapy. Dr. Silverstein argues that for many women, the small or nonexistent benefits are not worth the drawbacks, and he urges all patients with DCIS who are considering radiation therapy to seek a second opinion.

Integrated Teamwork in Specialized Centers—Best Treatment

Closely integrated teamwork is the key to complete excision of DCIS. To achieve sufficiently wide margins, breast cancer surgery is best performed by an integrated, experienced team including a surgeon, pathologist, and radiologist—with long-term follow-up by a team consisting of a radiologist, surgical, and medical oncologist, said Dr. Silverstein.

More than 90% of DCIS cases are found by mammography. This cancer is not palpable or visible in the operating room. “The initial excision offers the best chance to remove the cancer with adequate margins while achieving the best possible cosmetic result. “At USC, we use multiple guide wires in surgeries to localize all DCIS lesions followed by complete and sequential tissue processing,” said Dr. Silverstein. “It’s very difficult to remove a DCIS and achieve an adequate margin using a single wire, which is the current standard throughout the United States.”

“The balance between adequate margins and a good cosmetic result is a difficult one to achieve,” he said. “Although most of these technologies are available in the community, they are not often well integrated. For now, the best treatment options lies with specialized multidisciplinary breast centers. They have the all the resources in terms of skilled radiologists, surgeons, and pathologists, working as an integrated team.”

“The current paradigm requires radiation therapy for all patients with DCIS who elect breast preservation,” said Dr. Silverstein. “This paper may change such thinking in that it allows clinicians to identify patients for whom there will be little or no benefit from radiation therapy.”