Pathobiology of small invasive breast cancers without metastases (T1a/b, N0, M0): National Surgical Adjuvant Breast and Bowel Project (NSABP) protocol B-21.

Abstract

Uncertainties continue to exist concerning the outcomes and management of small (T1a/b N0 M0) invasive breast cancers. A central pathology review was performed of 638 such lesions from National Surgical Adjuvant Breast and Bowel Project (NSABP) clinical trial B-21. Univariate analysis revealed a high risk for ipsilateral breast tumor recurrence with tumors exhibiting a ductal carcinoma in situ component or poor nuclear grade. The converse (protective effect) was found with tumors arising in radial scars, those of tubular histologic type, and those with moderate/marked tumor stroma. The correlations were generally similar for disease-free survival. However, only nuclear grade was found to be independently significant for both of these outcomes. Only lymphatic tumor extension was univariately and multivariately significant for overall survival. The long-term results of follow-up (median, 11.2 years) from the current trial continue to support the need for local breast irradiation and adjuvant therapy in the management of patients with these small cancers.