P2-12-09: Prediction of Residual Risk of Recurrence after 5 Years of Follow-Up by Clinicopathologic Variables and 4 IHC Markers: A TransATAC Study.

Abstract Background Adjuvant endocrine therapy beyond 5 years is known to be of benefit to some ER+ patients but it is unclear which patients have sufficient residual risk (RR) to merit this. We have previously shown that 4 immunohistochemical markers (ER, PgR, Ki67, HER-2), both alone and combined into the IHC4 score (Cuzick et al, JCO 2011) are significantly correlated with time to recurrence (TTR) in the overall follow up of a cohort of 1125 patients from the monotherapy arms of the Arimidex, Tamoxifen, Alone or in combination (ATAC) trial. We have now assessed the relationship of each of these parameters and common clinical variables (nodal status, grade, tumour size, age and treatment option) for predicting outcome beyond 5 years. Material and Methods: We determined the univariate and multivariate prognostic value of clinical variables and the 4 IHC variables separately and as the IHC4 score for TTR separately in years 0–5 and 5–10 of follow up for all patients, separately for anastrozole and tamoxifen and only in the node-negative patients. Results: Results in years 5–10 are summarized in the Table. Nodal status, tumour size and grade were at least as strong in years 5–10 as in years 0–5. Ki67 and the overall IHC4 score were the only significant IHC biomarkers related to TTR univariately in this period, but both lost significance in a multivariate model including clinical variables. There were no significant interactions with treatment. Similar results were seen for the node-negative population. Conclusions: None of the IHC4 markers provided significant additional prognostic information in the 5–10 year period, but nodal status, tumour size and grade continued to be strong prognostic factors. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-12-09.