Clearance of ctDNA in triple negative and Her2 positive breast cancer patients during neoadjuvant treatment is correlated with pathological complete responses

Contributors

Nikaoly Ciriaco¹, Esther Zamora³, Santiago Escrivá³, Rosa Somoza¹, Javier Hernández-Losa¹, Santiago Ramón y Cajal¹, Martín Espinosa-Bravo², Kaja Wieghardt⁴, Hillary Sloane⁴, Anna Starus⁴, Frank Holtrup⁴, Johannes Fredebohm⁴, Daniel L. Edelstein⁴, Lucy Georgieva⁵, Graham Speight⁵, Frederick S. Jones⁴, and Vicente Peg¹

¹Pathology Department, Hospital Universitario Vall d’Hebron, Barcelona, Spain; ²Breast Surgical Oncology Department, Hospital Universitario Vall d’Hebron, Barcelona, Spain; ³Oncology Department, Hospital Universitario Vall d’Hebron, Barcelona, Spain, ⁴Sysmex Inostics, Baltimore , USA, ⁵Oxford Gene Technology, Oxford, UK

Background

Neoadjuvant treatment (NAT) is being used widely to eliminate tumor burden in breast cancer (BC) patients; the primary goal of such treatments is to reduce the cancer prior to surgery. Although the standard of care is to perform surgery of primary BC after NAT, it is well known that for certain patients achieving clinical complete response (cCR) and pathological complete response (pCR), surgery following such treatment may be unnecessary.

Previous studies have shown that levels of circulating tumor DNA (ctDNA) during therapy and post-surgery can stratify patients that exhibit effective responses vs. those showing minimal residual disease. In this study, we performed longitudinal tracking of plasma TP53 and PIK3CA mutations pre-specified from NGS analysis of tumor tissue specimens from HER2-positive (HER2) and triple negative (TN) BC patients. The primary objective of this study was to assess ctDNA clearance during NAT as a correlate to effective response to treatment, as benchmarked by clinical complete response (cCR) and pathological complete response (pCR). To accomplish this, a prospective study was conducted to identify patient-specific PIK3CA and TP53 mutations in tissue using SureSeq NGS technology, which could then be used to track the presence/absence of mutations prior to, during, and following NAT using Sysmex SafeSEQ technology.