Pathologic findings from the National Surgical Adjuvant Breast Project (NSABP) eight-year update of Protocol B-17

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Abstract
BACKGROUND This report is an 8‐year update of the authors' previous findings from National Surgical Adjuvant Breast Project (NSABP) Protocol B‐17, which relates to the influence of pathologic characteristics on the natural history and treatment of intraductal carcinoma (DCIS). METHODS Nine pathologic features observed in a pathologic subset of 623 of 814 evaluable women enrolled in this randomized clinical trial were assessed for their role in the prediction of second ipsilateral breast tumors (IBT), other events, and selection of breast irradiation (XRT) following lumpectomy. RESULTS The frequency of subsequent IBT was reduced from 31% to 13% (P = 0.0001) by XRT. The average annual hazard rates for IBT were reduced by XRT for all pathologic features examined. Four characteristics were individually noted to be significantly related to IBT, but only moderate‐to‐marked and absent‐to‐slight comedo necrosis were found to be independent high and low risk predictors, respectively, for such an event in patients of both treatment groups. XRT effected a 7% absolute reduction at 8 years in the low risk group. Despite a relatively high incidence (≈40%) of IBT consisting of invasive cancer, mortality due to breast carcinoma after DCIS for the entire cohort was found to be only 1.6% at 8 years. CONCLUSIONS The degree of comedo necrosis in patients with DCIS appears to be sufficient for discriminating between high and low risks for IBT following lumpectomy for DCIS. Although margin status, unlike in our previous report, was found to have only a slight or borderline influence on the frequency of IBT at 8 years, excision of DCIS with free margins is advised. The low risk group exhibits a statistically significant reduction of IBT from XRT. The decision to forgo XRT in the treatment of this singular subset of patients would appear to depend on clinical considerations and the input of informed patients rather than being standard practice. [See editorial on pages 375–7, this issue.] Cancer 1999;86:429–38. © 1999 American Cancer Society.