P2-12-19: Nomogram To Predict Recurrence and To Avoid Unnecessary Adjuvant Chemotherapy Based on Ki67 Index and ER Status in Hormone Receptor (HR)-Positive Breast Cancers with Low Number of Nodal Metastases (≤3) (NCT01273415).

Abstract Background Hormone receptor (HR) positive breast cancers characterized with ER-associated genes are differentiated luminal B from luminal A tumors mainly by proliferation genes. According to NCCN guideline 2011, node positivity has been a main determinant to decide adjuvant chemotherapy with category 1. However, the experts’ panel at the St. Gallen Consensus in 2009 do not provides definite indications to give or withhold chemotherapy in patient group with intermediate criteria including low numbers (1-3, N1) of involved lymph nodes. Thus, in cases of limited number of nodal metastases, the role of biologic factors including Ki67 index needs to be defined. The aims of this study are to evaluate of Ki67 index as a useful surrogate marker to predict recurrence and to avoid unnecessary adjuvant chemotherapy and to develop nomogram based on Ki67 index to determine adjuvant therapeutic options in HR-positive in N0 and N1 breast cancers. Patients and Methods We retrospectively analyzed the clinicopathologic characteristics and outcomes of 953 postoperative HR-positive N0 and N1 breast cancer patients between 2004 and 2007 at the Samsung Medical Center. We constructed nomogram based on Cox regression model using independent factors demonstrated in multivariate analysis and validated externally in a cohort of 895 patients treated at Seoul National University Hospital. Results: In Cox regression multivariate analysis, ER-ve/PgR+ve and Ki67 index were identified as independent factors. Nomogram base on Cox-regression model showed an AUC of 0.75 (95% CI, 0.72−0.77) in the training set. The validation set showed a good discrimination with an AUC of 0.63 (95% CI, 0.60−0.66). We defined low nomogram score as less than 53, and high nomogram score as 53 or more from the cut-off value of the nomogrma ROC curve. Patients who received anthracycline-containing adjuvant chemotherapy with high nomogram scores showed better RFS with statistical significance than those who did not receive anthracycline-containing adjuvant chemotherapy with high nomogram scores (p<0.0001). In contrast, the patients with low nomogram scores did not show any benefit from anthracycline-containing adjuvant chemotherapy (p=0.804). When the patients with high nomogram scores divided into two groups according to Allred ER scores (0-4 vs 5–8), the patients with high ER Allred scores (5-8) and high nomogram scores did not show any benefit from anthracycline-containing chemotherapy (p=0.283). Main benefit from adjuvant chemotherapy is focused on the patients with low ER Allred scores (0-4) and high nomogram score (p=0.022). Conclusion: Ki67 index is useful as a valuable surrogate marker to predict recurrence and to avoid unnecessary chemotherapy. Nomogram based on Ki67 index is constructed and validated to determine adjuvant therapeutic options in HR-positive N0 and N1 breast cancers. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-12-19.