Trans-CHER-Lob: A Biomarker Analysis of the Randomized Phase II Study of Neoadjuvant Chemotherapy Plus Trastuzumab, Lapatinib or Combined Trastuzumab and Lapatinib in HER2 Positive Operable Breast Cancer.

Introduction: The CHER-Lob study is a randomized phase II trial of preoperative sequential taxanes-anthracyclines in combination with trastuzumab, lapatinib, or combined trastuzumab and lapatinib in HER2 positive, stage II-IIIA breast cancer patients. A translational program to evaluate predictors of response as well as treatment effects on tissue biomarkers was pre-planned. Methods: The CHER-Lob translational program includes the central evaluation of HER2, p95HER2, PTEN, pAKT, Ki67 on pre and post-therapy samples. All these biomarkers have been evaluated by immunohistochemistry. FISH analysis was performed in case of HER2 IHC 2+, and in all the discordant cases between central and local laboratories. Biomarkers change from baseline to surgery has been evaluated with the Wilcoxon signed-ranks matched-pair test. Results: 121 patients have been randomized. The pathologic complete response rate (breast and axillary lymphnodes) was 26% in Arm A (chemotherapy + trastuzumab), 28% in arm B (chemotherapy + lapatinib) and 44% in arm C (chemotherapy + trastuzumab and lapatinib). The concordance between central and local HER2 assessment on pre-treatment biopsy was 97%. The mean (min;max) PTEN expression pre- and post-therapy were 66% (0;100) and 68.4% (0;100) respectively. The mean (min;max) pAKT expression pre- and post-therapy were 23.3% (0;100) and 8.8% (0;90) respectively. A significant decrease was observed in the overall samples (p=0.01). When analyzing the lapatinib alone arm, the difference was no longer significant (p=0.06), while it maintained significance when evaluating the two trastuzumab containing arms (p=0.0013). The mean (min;max) ki67 expression pre- and post-therapy were 29.5% (4;90) and 16.6% (1;50) respectively. A significant decrease was observed when looking at the whole population (p<0.0001). A significantly higher ki67 inhibition was observed in the dual vs single anti-Her2 therapy (p= 0.003). Conclusions: The central HER2 retesting showed a high concordance with local laboratories. Treatment induced a suppression in pAKT expression, that was higher in patients receiving trastuzumab. The dual anti-HER2 blockade induced a higher KI67 inhibition as compared to single anti-Her2 blockade. The evaluation of the predictive and prognostic role of these biomarkers is ongoing. Supported by GlaxoSmithKline