569 Background: Taxane and platinum (TP) NAC regimens, e.g. Carboplatin and Docetaxel (CbD), in TNBC are currently of great interest, having good pathologic complete response (pCR) rates but with a significantly more manageable toxicity profile compared to anthracycline-based NAC regimens. Forkhead Box C1 (FOXC1), a transcriptional driver of cell plasticity/partial EMT/metastasis is an established mesenchymal marker diagnostic of basal-like breast cancer having proven prognostic value, but of uncertain predictive value. We sought to evaluate the potential of FOXC1 in predicting pCR to neoadjuvant TP regimens in patients diagnosed with TNBC. Methods: Pre-NAC tumor biopsy FOXC1 mRNA expression status was correlated with rate of pCR in a pooled, ambispective cohort (prospective cohort GEICAM/2006-03, NCT00432172 pooled with multi-institutional retrospective cohort, n = 119). A specific FOXC1 mRNA expression cutoff value was derived to maximize Negative Predictive Value (NPV) and Sensitivity for pCR prediction. The pCR-predictive ability of FOXC1 mRNA expression was then assessed in two validation cohorts of evaluable patients who had been enrolled in prospective clinical trials (UCONN/FIOCRUZ, n = 222, HGUGM, NCT01560663, n = 221). All evaluated patients had been diagnosed with TNBC and had received a Taxane plus Platinum-based NAC regimen. Results: FOXC1 mRNA expression was associated with pCR in CbD/TP treated TNBC patients with pCR rates of 43.48%, 47.89% and 52.73% observed in the discovery and two validation cohorts (two tailed T-test p-values of 0.0005, 0.002, 0.009, respectively). FOXC1 expression above the pre-determined cutoff value was associated with pCR to CbD/TP NAC in patients diagnosed with TNBC in both validation cohorts (OR 4.894, 1.504-15.924; p = 0.004 and OR 2.293, 1.208-4.352; p = 0.006). Conclusions: We report the retrospective validation of pre-NAC breast cancer biopsy FOXC1 mRNA expression for predicting efficacy of CbD/TP NAC in two independent, prospectively accrued TNBC patient cohorts. The described strategy may be acceptable for patient stratification to guide CbD/TP NAC recommendations in TNBC. FOXC1 mRNA or protein expression, assessed using qRT-PCR or routine immunohistochemistry (IHC), respectively, could potentially be utilized in future fixed-arm/adaptive clinical trials to further optimize NAC efficacy, in terms of achieved pCR rates, and to extend disease-free survival in patients diagnosed with TNBC.
<p>Supplemental Methods, Tables and Figures Tables Table S1. CES association with chemotherapy sensitivity (measured as pCR) in the MDACC-based dataset. Table S2. CES association with chemotherapy sensitivity (measured as Residual Cancer Burden [RCB]) in the MDACC-based dataset. Model A. Table S3. CES association with chemotherapy sensitivity (measured as Residual Cancer Burden [RCB]) in the MDACC-based dataset. Model B. Table S4. Univariate association of CES and various signatures with chemotherapy sensitivity in HR+/HER2-negative disease from the MDACC-based dataset. Table S5. Association of CES and PAM50 Proliferation Signature with chemotherapy sensitivity in HR+/HER2-negative disease from the MDACC-based dataset. Table S6. Association of CES and CHEMOPRED Signature with chemotherapy sensitivity in HR+/HER2-negative disease from the MDACC-based dataset. Table S7. Association of CES and the proliferation component of the Genomic Health Index (GHI; OncotypeDX Recurrence Score) with chemotherapy sensitivity in HR+/HER2- negative disease from the MDACC-based dataset. Table S8. Association of CES and Genomic Grade Index (GGI) Signature with chemotherapy sensitivity in HR+/HER2-negative disease from the MDACC-based dataset. Table S9. Association of CES and SET index Signature with chemotherapy sensitivity in HR+/HER2-negative disease from the MDACC-based dataset. Table S10. Association of CES and RCBPRED Signature with chemotherapy sensitivity in HR+/HER2-negative disease from the MDACC-based dataset. Table S11. Association of CES and DLDA30 Signature with chemotherapy sensitivity in HR+/HER2-negative disease from the MDACC-based dataset. Table S12. Association of CES and ROR-P Signature with chemotherapy sensitivity in HR+/HER2-negative disease from the MDACC-based dataset. Table S13. Association of CES and Ki67 by IHC with chemotherapy sensitivity in HR+/HER2-negative disease of the Malaga cohort. 7 Table S14. Association of CES and PAM50 ROR with chemotherapy sensitivity in HR+/HER2-negative disease of the Malaga cohort. Table S15. CES association with endocrine sensitivity in the Marsden dataset (n=103). Table S16. CES association with endocrine sensitivity in the Marsden dataset within HER2-negative disease (n=89). Figures Fig. S1. Association of CES with Miller-Payne following chemotherapy in HR+/HER2- negative disease from the Malaga-based cohort. Fig. S2. CES association with endocrine sensitivity in the Edinburgh dataset (n=120). (A) Tumor volume changes of each patient and response classification. (B) Association of CES and other variables with response (defined as at least 70% reduction by 90 days) in the overall population. (C) Association of CES and other variables with response within HER2-negative disease. Fig. S3. Association of CES with pCR in the combined dataset from the MDACC- and Malaga-based cohorts.</p>
<p>Supplementary Figure S4 shows a forest plot of the exploratory categorical analysis of selected (meta)gene expression and their association with disease free survival on the capecitabine arm vs. observation.</p>
<p>Supplementary Table 1. List of the 21 genes included in the breast cancer panel used for sequencing, and the targeted coding regions in each case.</p>
<p>Supplementary Table 12. Baseline genomic landscape of mutations distribution for the CDR population (n=120), by number of mutations or presence/absence, across treatment arms.</p>