Abstract OT1-1-11: DETECT III - A multicenter, randomized, phase III trial to compare standard therapy alone versus standard therapy plus lapatinib in patients with initially HER2-negative metastatic breast cancer and HER2-positive circulating tumor cells

Abstract

Abstract Background: In metastatic breast cancer (MBC) patients, HER2 status may be subject to change and it has been shown that 20-30% of initially HER2-negative patients have HER2-positive metastases. The discordance of the HER2 status between primary tumor and circulating tumor cells (CTCs) may be an important factor affecting the response to HER2-targeted treatments; however, it is unclear if therapy based on the HER2 status of CTC offers a clinical benefit for patients. Trial Design: DETECT III is a recruiting prospective, multicenter, open-label, two-arm, phase-III study for patients with HER2-negative MBC. Patients with HER2-positve CTCs are randomized to receive either a standard therapy of the physician's choice alone or a standard therapy plus additional HER2-targeted treatment with Lapatinib. Main Eligibility criteria: - Metastatic breast cancer; - HER2-negative primary tumor tissue and/or biopsies from metastatic sites; - Evidence of at least 1 HER2-positive CTC out of 7.5 ml blood; - Indication for systemic treatment - ≥1 lesion evaluable according to RECIST Specific aims: The objective of the DETECT III trial is to estimate the clinical efficacy of standard therapy plus lapatinib as assessed by progression free survival (PFS) in patients with initially HER2-negative MBC and HER2-positive CTCs. Additional research will be performed on CTC dynamic and characteristics. Present accrual and target accrual: The DETECT III – trial started February 2012 and has analyzed so far (2013-06-06) 506 patients. We found CTCs in 336 (66.4%) patients (median 7 CTCs, range 1-35078). 67 of these patients (19.9%) had at least one HER2 positive CTC. Estimated patient enrollment is 228. Methods: The primary endpoint progression-free survival will be estimated using the Kaplan-Meier method. Prevalence and number of CTCs at various time points as well as the HER2 status of CTCs will be determined using the FDA-approved CellSearch System (Veridex, USA). In addition, different measures of CTC dynamics and their value for evaluating therapy efficacy or as a prognostic tool will be examined in detail by explorative data analyses. Perspectives: The DETECT III-Trail is the first study where treatment is based on phenotypic characteristics of CTCs. If this trial succeeds in proving efficacy of lapatinib in patients with initially HER2-negative primary tumor but HER2-positive CTCs, it may lead to a new strategy for the treatment of metastatic breast cancer. Contact information: nikolaus.de-gregorio@uniklinik-ulm.de. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr OT1-1-11.