Adams, Daniel

Abstract Purpose: Activation of the RAS/MAPK pathway is associated with reduced tumor-infiltrating lymphocytes and poor outcomes in triple-negative breast cancer. Previous studies demonstrated that inhibition of the MAPK pathway with a MEK inhibitor is synergistic with immune checkpoint inhibitors. Patients and Methods: We conducted a phase I/II trial of pembrolizumab and binimetinib in patients with metastatic triple-negative breast cancer with ≤3 prior lines of therapy. There were two dose levels (DL) with binimetinib at 45 mg at DL 0 and 30 mg at DL −1. Results: The recommended phase II dose was the standard dose of pembrolizumab with binimetinib 30 mg twice daily. The objective response rate (ORR) was 30.4%, with a numerically higher ORR in patients without liver metastasis at 45.5%. Among patients who achieved objective responses, 80% had a duration of response >12 months and ongoing even after stopping treatment (5.4–69.0 months). Patients with PD-L1–positive tumors (modified proportion score ≥10) were more likely to respond with an ORR of 66.7%. However, clinical benefit was observed in 25% of patients with PD-L1–negative tumors. Consistent with preclinical studies, four of six patients with clinical benefit had either increased PD-L1 or decreased p-ERK expressions in serial circulating cancer-associated macrophage-like cells after starting binimetinib. Conclusions: Pembrolizumab and binimetinib at 30 mg are safe with manageable toxicities. Promising activity was observed in patients without liver metastases. Future larger clinical trials are warranted to further evaluate the efficacy of this chemotherapy-free combination.

AbstractRecent studies reporting hundreds, to thousands, of circulating tumor cells (CTCs) in the blood of cancer patients have raised questions regarding the prevalence of CTCs, as enumerated by the CellSearch® CTC Test. Although CellSearch has been shown to consistently detect clinically relevant CTCs; the ability to only capture EpCAM positive cells has led to speculation that it captures limited subsets of CTCs. In contrast, alternative approaches to CTC isolation are often cited as capturing large numbers of CTCs from patient blood. Not surprisingly the number of cells isolated by alternative approaches show poor correlations when compared to CellSearch, even when accounting for EpCAM presence or absence. In an effort to address this discrepancy, we ran an exploratory method comparison study to characterize and compare the CTC subgroups captured from duplicate blood samples from 30 breast and prostate cancer patients using a microfiltration system (CellSieve™) and CellSearch. We then categorized the CellSieve Cytokeratin(CK)+/CD45−/DAPI+ cells into five morphologically distinct subpopulations for correlative analysis. Like other filtration techniques, CellSieve isolated greater numbers of CK+/CD45− cells than CellSearch. Furthermore, analysis showed low correlation between the total CK+/CD45− cells captured by these two assays, regardless of EpCAM presence. However, subgrouping of CK+/CD45−/DAPI+ cells based on distinct cytokeratin staining patterns and nuclear morphologies elucidated a subpopulation correlative to CellSearch. Using method comparison analyses, we identified a specific CTC morphology which is highly correlative between two distinct capture methods. These data suggests that although various morphologic CTCs with similar phenotypic expressions are present in the blood of cancer patients, the clinically relevant cells isolated by CellSearch can potentially be identified using non‐EpCAM dependent isolation. © 2014 The Authors. Published by Wiley Periodicals, Inc.