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Abstract 4593: Genomic profiling of cell free DNA (cfDNA) from patients with inflammatory breast cancer (IBC)

Inflammatory breast cancer (IBC) currently accounts for 2% to 6% of all breast cancer cases in the United States and up to 20% of all breast cancer cases globally. IBC exhibits distinctively aggressive clinical features compared to all breast cancers, and accounts for a disproportionally high mortality rate—15% of breast cancer-related deaths in U.S. In addition, the survival rates between stage-matched IBC and non-IBC differ drastically. Therefore, we are in need of better understanding the molecular abnormalities driving IBC aggressive phenotype. We performed a study to evaluate the genomic alterations in cell free DNA (cfDNA) from plasma from 13 IBC patients, including 9 with triple-negative disease. In 6 patients, mutation analyses were also studied in tumor samples (tumor tissue or tumor cells from pleural effusions). Mutation analysis was performed by next-generation sequencing (NGS) using a unique molecular identifiers (UMI) assay and a panel of 93 breast cancer-related genes (Qiagen). The data were analyzed using the Qiagen9s GeneGlobe portal and Biomedical Genomics Workbench and interpretation was performed with Qiagen9s QCI. Somatic mutations detected in cfDNA samples were seen in: TP53 (7/13), RB1 (2/13), GEN1 (2/13) and EP300 (2/13); additional somatic mutations were found in PIK3CA (1/13), ERBB2 (1/13), PALB2 (1/13) and MUC16 (1/13). In 4 patients with plasma and tumor samples taken at the same time of the disease progression, complete concordance was not found in the somatic mutations detected in cfDNA and tumor cells DNA. Interestingly, in 12 of 13 IBC patients some variants were observed with high variant allele frequencies (VAF), ~50% or ~100% at a total coverage depth ≥230 reads, in the following genes: BRCA2 (1/13), RAD51D (2/13), PALB2 (1/13), RAD51C (1/13), AR (1/13) and MUTYH (1/13), which were classified as pathogenic or likely pathogenic, and BARD1 (3/13), SYNE1 (2/13), KMT2C (2/13), BRIP1 (1/13), XRCC3 (1/13), RET (1/13), APC (1/13), RAD50 (1/13) and MUC16 (1/13), classified as variants of uncertain significance. Moreover, 11 of these patients had a family history of different cancers including breast, colon, prostate, stomach, bladder, cervical cancers, and melanoma and myeloma. In the 6 patients where cfDNA and tumor samples were available, mutations with high VAF were found in both samples (100% concordance), suggesting that variants with high VAF are germline variants. These results suggest that the described germline variants could increase the risk of IBC and somatic mutation information obtained from cfDNA is complementary to that obtained from tissue samples. Studies on more samples are in progress. Citation Format: Jianming Pei, Jacqueline Talarchek, Jennifer S. Winn, Katherine Alpaugh, Massimo Cristofanilli, Sandra V. Fernandez. Genomic profiling of cell free DNA (cfDNA) from patients with inflammatory breast cancer (IBC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4593.