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Researchers evaluate predictors of re-excision, residual disease in women with close, positive margins following partial mastectomy

Friday, October 17 2008 | Comments
Evidence Grade 7 What's This?
By Courtneay Parsons

Among women who present with a close or positive margin following partial mastectomy for ductal carcinoma in situ (DCIS) or invasive cancer, histology and margin status strongly predict a surgeon's decision to re-excise tissue. However, in these patients, neither of these variables seems to predict the presence of residual disease, according to a recent study.

Drs. Laurence McCahill and Alicia Privette and their colleagues from the University of Vermont and Fletcher Allen Health Care evaluated predictors of the decision to re-excise close (<1 mm) or positive margins following partial mastectomy as well as predictors of residual disease.

Using their prospectively collected breast cancer surgical outcomes database, they identified 201 patients who had close or positive margins following partial mastectomy for either DCIS or invasive cancer. Of these patients, 105 had tissue re-excised. Of the re-excised specimens, 54 contained residual disease.

Potential predictors of both re-excision and residual disease included age, histology, margin distance (positive or close), margin direction (anterior/posterior, radial, or multiple margins), tumor size, surgeon case volume, dual histology at the margin edge, and the presence of axillary disease.

Re-excision rates for close margins varied significantly by diagnosis, Dr. Privette noted. Although positive margins were almost universally re-excised, only 3.6% of close invasive cancer margins were re-excised compared with 50% of close DCIS margins.

In a univariate analysis, age, histology (DCIS), margin distance, margin direction, DCIS size, and the presence of dual histology were significant predictors of re-excision. In a multivariate analysis, all but DCIS size remained significant. The presence of positive margins was the strongest predictor of re-excision (OR, 78.6).

Interestingly, Dr. Privette noted, the presence of residual disease in re-excised specimens was not predicted by DCIS histology or by positive (vs close) margin status.

Predictors of both re-excision and residual disease included the presence of radial or multiple margins and the presence of dual histology. DCIS size >25 mm predicted residual disease, but not re-excision.

These data suggest that residual disease is no less likely with close margins than with positive margins, Dr. Privette explained. As a result, she said close margins may need to be excised more frequently, perhaps as frequently as positive margins, to better control residual disease.

"Histology and margin status may need to be re-evaluated as reasons for re-excision due to the fact that, although they were highly significant predictors of the decision to re-excise, in comparison to each other (positive vs close, DCIS vs invasive), they were not correlated with the presence of residual disease on re-excision," she concluded. (Part of: Surgical Forum 19.)

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