Meeting Highlights: International Consensus Panel on the Treatment of Primary Breast Cancer

TL;DR: A case can be made for adjuvant tamoxifen to prevent a second primary breast cancer by analogy with the Breast Cancer Prevention Trial (National Surgical Adjuvant Breast and Bowel Project P-1) and the overview by the EBCTCG.

Abstract: a series of guidelines and recommendations for selection of adjuvant systemic treatments in specific patient populations. The Panel reviewed and modified its previous guidelines and recommendations based on new evidence that has emerged from clinical research. Overall, the Panel developed a simplified classification of risk and highlighted the factors governing selection of adjuvant endocrine and cytotoxic therapies. Considerations on postoperative radiation therapy as well as aspects of preoperative systemic treatments and use of biologic compounds were also discussed. PROGNOSIS AND PREDICTION OF RESPONSE An important change from previous years is that the Panel no longer defines a group of patients who should not be offered adjuvant systemic therapy. Even among patients who are at minimal or low risk of recurrence (10% recurrence at 10 years; Table 2), a case can be made for adjuvant tamoxifen to prevent a second primary breast cancer by analogy with the Breast Cancer Prevention Trial (National Surgical Adjuvant Breast and Bowel Project P-1) 17 and the overview by the EBCTCG. 3 Reduced incidence of second breast cancers in women receiving tamoxifen was confined to the cohorts with tumors expressing steroid hormone receptors, whereas no reduction in incidence was observed for patients who had tumors without such receptors. The most relevant factors for the estimation of risk of recurrence remain the nodal status and the number of nodes involved. For patients with node-negative presentation, pathologic tumor size, histologic and nuclear grade, and age are factors considered to define differential prognosis (Table 2). Although all patients with involved nodes are at high risk, there remains a gradient of absolute risk of recurrence and therefore of absolute benefit from adjuvant therapy as the number of involved axillary lymph nodes increases. An additional fundamental change from the previous consensus is that treatment selection is based primarily on assessment of endocrine-responsive or endocrine-nonresponsive disease according to the presence of estrogen and progesterone receptors in the primary tumor. The threshold defining endocrine-responsive disease has also changed in that tumors containing as few as 1% of cells staining for steroid hormone receptors are regarded as potentially endocrine-responsive (ie, might benefit from the addition of endocrine therapies to the adjuvant treatment program). Selection of endocrine therapy alone, chemotherapy alone,