Circulating tumor cells and response to neoadjuvant paclitaxel and HER2-targeted therapy: A sub-study from the NeoALTTO phase III trial

Abstract

BackgroundThe role of circulating tumor cells (CTCs) in HER2-positive breast cancer patients receiving neoadjuvant therapy is unclear. Patients & methodsWe describe the CTC detection rate, HER2 phenotyping and pathological complete response (pCR) in patients enrolled in the NeoALTTO phase III trial. Participation in the CTC sub-study was optional. CTC evaluation was performed centrally using CellSearch® at baseline, week 2 and week 18 (prior to surgery) of neoadjuvant therapy. ResultsSamples for CTC analysis were available for 51/455 patients randomized. At baseline, week 2 and week 18, we detected ≥1 CTC/22.5 ml in 5/46 (11%), 4/41 (10%), and 5/31 (16%) patients and ≥1 HER2-positive CTC/22.5 ml in 2/46 (4%), 2/41 (5%), and 3/31 (10%) patients with evaluable samples, respectively. 11/51 patients (21%) had ≥1 CTC/22.5 ml in at least one time point. pCR was observed in 3/11 (27.3%) versus 17/40 (42.5%) patients with detectable and no detectable CTCs, respectively (p = 0.36). No pCR was observed in the three patients with detectable HER2-positive CTCs prior to surgery. ConclusionNumerically lower pCR rates were observed in patients with detectable CTCs, yet the study remains underpowered. A meta-analysis of CTC studies in this setting is warranted.