Abstract PD05-03: What is the appropriate sample (s) on which to perform sequencing for mutational analysis to guide the selection of targeted therapy?

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Abstract BACKGROUND: Success of targeted therapy requires expression of the protein. Tumor tissue source can include diagnostic biopsy, surgical samples from initial or follow-up surgeries, fluids e.g. pleural or ascites and circulating tumor cells (CTC). The goal of using CTCs was 1. To determine whether CTC can be used as a “liquid” tumor biopsy and enable gene sequence information at the single cell level and 2. To determine the heterogeneity represented in the circulation compared to that seen in solid tumor by examining single cells (or a small cluster of cells) for the presence of a specific mutation which was detected in tissue tumor source. METHODS: We performed sequencing for mutational analysis on tissue(s) from patients with inflammatory breast cancer (IBC). Tumor sources varied from mastectomy tissue, metastatic site(s) e.g. liver or skin from chest wall disease, pleural fluid and CTC isolated into pure single cell populations (or groups of cells) using Silicon Biosystems DEPArray. Ampli1™ WGA kit was used for CTC amplification. Of the 22 patients sequenced, mastectomy primary tumor was examined in 3, metastatic site skin chest wall disease in 15, other metastatic site in 4, pleural fluid in 2 and CTC collected to investigate p53 mutations in 8. RESULTS: To date 22 patients have had mutational data performed, 14/22 had mutations in p53, 4/22 in RB1, 2/22 in each PI3K and ERBB2, 1/22 in each of BRAC1, BRAC2, ATM, KRAS, Notch 1, MEN1 and ESR1. Numerous amplifications were noted including AKT1, RPTOR, MLC1, MYC, CCND1 and ERBB2. For one patient's chest wall biopsy compared to two single CTCs and a cluster of 10 CTCs the same TP53C229fs*10 mutation was detected revealing the same 2bp deletion. No 2bp deletion was found in single white blood cells. Whereas, another patient which showed a TP53 S215G mutation in her skin biopsy of chest wall disease, only amplifications of AURKA, CCND1, IGF1R, MDM2 and SRC in pleural tumor cells were detected and no mutations in three single CTC, two single pleural tumor cells and in single white blood cells were seen. Primary tumor tissue is being sort for both of these patients. Mutational data reviewed to date suggest that IBC is not one disease but a multiplicity of diseases, revealing a variety of target(s). Aberrations are not consistent across tissue source. CONCLUSIONS: Successful treatment outcomes using standard of care chemotherapy combined with target therapies will require not one, but a panel, of tissue sources for sequencing to guide the selection of appropriate targeted therapies. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr PD05-03.