Next generation sequencing of breast cancer in the neoadjuvant setting.

INTRODUCTION: Many patients with locally advanced breast cancer are proposed to neoadjuvant chemotherapy (NAT) before surgery. Only some of them achieve a pathological complete response (pCR). The determination of gene somatic alterations using Next Generation Sequencing (NGS) in the non-pCR tumors is important, in order to identify potential opportunities of treatment for the patients, if targeted therapies are available.

METHODS: Breast cancer tissue samples of 31 patients, collected before NAT, were analyzed by NGS using the Oncomine™ Comprehensive Assay Plus (OCA-Plus) panel.

RESULTS: 12 patients achieved pCR after NAT. ERBB2 gene alterations were the most frequent in this cohort of pCR patients, followed by BRCA 1 and 2, MYC, TP53, PIK3CA and MET alterations. Tumours that did not achieve a pCR were mainly triple negative. In this subgroup some BRCA 1 and 2 and PIK3CA gene alterations were identified, as well as TP53 mutations. The NGS panel employed in this study also allowed for the determination of tumor mutation burden (TMB).

DISCUSSION/CONCLUSION: This study showcases the significance of employing comprehensive genomic testing in breast cancer cases, primarily due to the scarcity of specific target assays. The detection of somatic mutations, coupled with the availability of targeted therapies, holds promise as a potential therapeutic avenue to enhance tumor response rates during NAT, or as a complementary treatment following surgery. Moreover, evaluating the TMB in non-pCR samples could serve as a valuable criterion for selecting patients suitable for immunotherapy. Further exploration through clinical trials is imperative to investigate these prospects.