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Background: This report updated previous findings, at the 15-year mark, of the National Surgical Breast and Bowel Project (NSAPB) Protocol B-06 with respect to the treatment of invasive breast carcinoma and the effects of pathologic features and the effects of some clinical features on its natural history., Methods: Thirty-one pathologic and 6 clinical features that were observed in a pathologic subset of 1039 evaluable patients were assessed as to their value in predicting survival, in predicting ipsilateral breast tumor recurrence (IBTR), and in predicting the necessity for local breast irradiation after lumpectomy. The patients had been randomly assigned to treatment by lumpectomy without local irradiation or to treatment by lumpectomy with local irradiation of the breast. A traditional and another statistical method were used for this purpose., Results: Multivariate analyses revealed that the presence of IBTR, race, histologic tumor type, nodal status, nuclear grade, and blood vessel invasion affected survival independently. Treatment, patient age, nuclear grade, presence of intraductal carcinoma, and a lymphocytic tumor infiltrate were features that predicted IBTR by multivariate analyses. Irradiation reduced IBTR from 36% to 12% in the analyzed cohort. A test of interaction failed to reveal any pathologic or clinical feature that might have allowed for the omission of local irradiation of the breast after lumpectomy., Conclusions: In addition to the influence of pathologic and clinical features on patient survival and IBTR, the site, histopathologic features, and time of occurrence of the latter allowed for insights into some important biologic considerations concerning invasive breast carcinoma., (Copyright 2001 American Cancer Society.)

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 (approximately 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.]