Abstract
Abstract The selection of chemotherapies is guided by the analysis of molecular targets in solid tumors for well-known somatic mutations identified in microdissected FFPE tissue. Combining a molecular targeting panel with select pharmacogenomic targets provides additional clinical information useful in customized patient management. We have developed a combined pharmacogenomic/molecular target approach using FFPE tissue from colon cancer patients. Our test, based on FDA guidance for Irinotecan administration to metastatic colorectal cancer (CRC) patients, is a recommended prescreening assay for UGT1A1 [TA] promoter variations to mimimize neutropenia. Meta-analysis of Irinotecan treated CRC patients has demonstrated an association between the [TA]7 allele (UGT1A1*28) and elevated levels of neutropenia in both homozygous and heterozygous carriers suggesting lowered dosing regimens (Liu, et al Pharmacogenomics J, 2013). Additional alleles, while uncommon in Caucasians, contribute to decreased levels of UGT1A1 enzymatic activity, and are restricted to genetic subgroups. Collectively these alleles influence the pharmacodynamic t1/2 of Irinotecan but are often not widely screened. Thus, a screening palate encompassing multiple ethnic-specific variants provides improved predictive information in a cosmopolitan population of cancer patients. As these polymorphisms are germline changes, UGT1A1 genotypes can be derived from either traditional whole blood assessment or more conveniently from FFPE surgical tissue at the time of diagnosis. We have screened paired blood/tumor samples from CRC patients to examine potential loss of heterozygosity in tumor specimens at this locus. In parallel, we screened microdissected tumor and adjacent normal tissue from FFPE samples to verify the potential of using tumor specimens as a routine alternative to blood. The use of FFPE tissue from CRC patients as part of a molecular work-up can provide genotypes for multiple UGT1A1 alleles of reduced activity (including *28), and may be better at predicting neutropenia in distinct Caucasian, Asian or other genetically distinct patient populations. The development of FFPE-based tests for pharmacogenomic tests such as UGT1A1 premised on genetic ancestry provides actionable information that can be used to maximize patient responses. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A211. Citation Format: Jack Hsiang, Rita El-Khoueiry, Heinz-Josef Lenz, Stephanie H. Astrow, Garrett P. Larson. Multiethnic screening for irinotecan sensitivity in FFPE tissue from colorectal cancer patients. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A211.
Published Version
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