Purpose: Elevated levels or increases in circulating tumor cells (CTC) portend poor prognosis in patients with epithelial cancers. Less is known about CTCs as surrogate endpoints or their use for predictive biomarker evaluation. This study investigated the utility of CTC enumeration and characterization using the CellSearch platform, as well as mutation detection in circulating tumor DNA (ctDNA), in patients with advanced non-small cell lung cancer (NSCLC).Experimental Design: Forty-one patients were enrolled in a single-arm phase II clinical trial of erlotinib and pertuzumab. Peripheral blood was analyzed for CTC enumeration, EGFR expression in CTCs, and detection of oncogenic mutations in CTCs and ctDNA. Changes in CTC levels were correlated with 2[18F]fluoro-2-deoxy-D-glucose-positron emission tomographic (FDG-PET) and computed tomographic (CT) imaging and survival endpoints.Results: CTCs were detected (1 CTC) at baseline in 78% of patients. Greater sensitivity for mutation detection was observed in ctDNA than in CTCs and detected mutations were strongly concordant with mutation status in matched tumor. Higher baseline CTC counts were associated with response to treatment by Response Evaluation Criteria in Solid Tumors (RECIST, P ¼ 0.009) and decreased CTC counts upon treatment were associated with FDG-PET and RECIST response (P ¼ 0.014 and P ¼ 0.019) and longer progression-free survival (P ¼ 0.050).Conclusion: These data provide evidence of a correlation between decreases in CTC counts and radiographic response by either FDG-PET or RECIST in patients with advanced NSCLC. These findings require prospective validation but suggest a potential role for using CTC decreases as an early indication of response to therapy and ctDNA for real-time assessment of mutation status from blood.

BackgroundEvaluation of cancer biomarkers from blood could significantly enable biomarker assessment by providing a relatively non-invasive source of representative tumor material. Circulating Tumor Cells (CTCs) isolated from blood of metastatic cancer patients hold significant promise in this regard.Methodology/Principal FindingsUsing spiked tumor-cells we evaluated CTC capture on different CTC technology platforms, including CellSearch® and two biochip platforms, and used the isolated CTCs to develop and optimize assays for molecular characterization of CTCs. We report similar performance for the various platforms tested in capturing CTCs, and find that capture efficiency is dependent on the level of EpCAM expression. We demonstrate that captured CTCs are amenable to biomarker analyses such as HER2 status, qRT-PCR for breast cancer subtype markers, KRAS mutation detection, and EGFR staining by immunofluorescence (IF). We quantify cell surface expression of EGFR in metastatic lung cancer patient samples. In addition, we determined HER2 status by IF and FISH in CTCs from metastatic breast cancer patients. In the majority of patients (89%) we found concordance with HER2 status from patient tumor tissue, though in a subset of patients (11%), HER2 status in CTCs differed from that observed in the primary tumor. Surprisingly, we found CTC counts to be higher in ER+ patients in comparison to HER2+ and triple negative patients, which could be explained by low EpCAM expression and a more mesenchymal phenotype of tumors belonging to the basal-like molecular subtype of breast cancer.Conclusions/SignificanceOur data suggests that molecular characterization from captured CTCs is possible and can potentially provide real-time information on biomarker status. In this regard, CTCs hold significant promise as a source of tumor material to facilitate clinical biomarker evaluation. However, limitations exist from a purely EpCAM based capture system and addition of antibodies to mesenchymal markers could further improve CTC capture efficiency to enable routine biomarker analysis from CTCs.

Inhibitors of Bruton's tyrosine kinase (BTK) have established therapeutic activity in patients with Waldenström macroglobulinemia (WM). Zanubrutinib, a potent and selective BTK inhibitor, was evaluated in a phase 1/2 study in patients with WM who were either treatment-naïve (TN) or had relapsed/refractory (R/R) disease. Patients had disease requiring treatment per International Workshop on Waldenström Macroglobulinemia (IWWM) criteria. Treatment was oral zanubrutinib 160 mg twice daily (n=50) or 320 mg once daily (n=23). Efficacy endpoints included overall response rate (ORR) and very good partial response/complete response (VGPR/CR) rates per IWWM-6 criteria (with modification of VGPR definition based on Treon 2015). Between September 2014 and March 2018, 77 patients (24 TN and 53 R/R) began treatment. At a median follow-up of 36.0 months for patients with R/R disease and 23.5 months for TN, 72.7% remained on treatment. Reasons for treatment discontinuation included any adverse events in 13.0% of patients (1 treatment related), disease progression (10.4%), and other (3.9%). The ORR was 95.9%, and the VGPR/CR rate was 45.2%, which increased over time: 20.5% at 6 months, 32.9% at 12 months, and 43.8% at 24 months. Estimated 3-year progression-free survival rate was 80.5%, and overall survival rate was 84.8%. Adverse events of interest included contusion (32.5%, all grade 1), neutropenia (18.2%), major hemorrhage (3.9%), atrial fibrillation/flutter (5.2%), and grade 3 diarrhea (2.6%). Long-term treatment with single-agent zanubrutinib resulted in deep and durable responses in some patients with WM. The safety profile of long-term zanubrutinib therapy in these patients was acceptable.