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SAN FRANCISCO -- Re-excision after breast-conserving surgery occurred 50% less often with intraoperative margin assessment by a device that distinguishes cancer cells from normal tissue, results of a randomized study showed.

Patients who underwent surgery and typical pathologic assessment for ductal carcinoma in situ (DCIS) had a re-excision rate of 37% compared with 13% among women whose surgeons used the MarginProbe to examine tissue in the operating room.

Among patients with both DCIS and invasive cancer, the re-excision rate was 17% with the device and 33% without, Susan K. Boolbol, MD, reported at a press briefing in advance of the Breast Cancer Symposium.

"The difficult part, as a surgeon in the operating room, is we don't have a lot of information to go on to determine whether the edge of the tissue is cancer free," Boolbol, of Brigham and Women's Hospital in Boston, said.

"The device gives us feedback in the operating room, gives us information as to whether there are cancer cells close to one of the margins," she added.

Breast-conserving surgery, or lumpectomy, has become the initial treatment for 60% to 70% of women with early breast cancer, including DCIS. Under usual circumstances, the surgical specimen is removed and sent to a pathology lab for assessment, which can take a week or more.

In 20% to 40% of cases, the pathology results show residual tumor cells in or near the surgical margin surrounding the tumor, and the patient has to return to the operating room for removal of more tissue. Even when the pathology report shows clear margins, the patient must endure several days of anxiety awaiting the results, said Boolbol.

The MarginProbe emits a biomagnetic signal and assesses tissue response to the signal. Cancer cells and normal tissue have different bioelectric signatures, which the device can distinguish. In June an FDA advisory committee recommended that the agency approve the device for clinical use.

Boolbol summarized findings from a randomized trial conducted at 22 sites in the U.S. and Israel. The study involved 596 women with early-stage breast cancer, including 161 patients with pure DCIS. The investigators randomized the patients to standard pathologic assessment after lumpectomy or to evaluation of tissue specimens in the operating room with the MarginProbe, followed by standard pathologic evaluation.

The primary outcomes were the rate of re-excision and comparison of tissue volume removed during standard lumpectomy and procedures that included tissue assessment in the operating room.

The 24% absolute reduction in the re-excision rate for DCIS achieved statistical significance (P=0.004), as did the 16% absolute difference among women with a mix of DCIS and invasive breast cancer (P=0.001).

The mean tissue volume removed did not differ significantly between the two groups (83 cc with the device versus 76 cc without).

Breast medical oncologist Andrew Seidman, of Memorial Sloan-Kettering Cancer Center in New York City, said patients and physicians alike stand to benefit from use of the device to assess lumpectomy tissue.

"This sounds like very welcome news that can reduce anxiety, cost, and perhaps time and effort for patients by getting it more right the first time," said Seidman, who moderated the press briefing.

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