Circulating tumor cells

Statement of the Problem: Currently, low dose CT (LDCT) screening for lung cancer is recommended for high-risk individuals, defined as current or former smokers (quit within the past 15 years) with a 30-or-more pack-year smoking history, 55 to 74 years of age, and with no evidence of lung cancer. However, uptake of LDCT screening has been impeded by high rates of false-positive results, which in turn add significant physical and emotional stress to patients as well as additional healthcare costs. Since LDCT is now commonly available, lung nodules detected in LDCT scans are plentiful, but imprecise guidelines for care make it a challenge to ensure quality follow-up and expedited diagnoses for those with lung cancer. Furthermore, screening is not available for those who don’t meet the screening criteria (younger age or low smoking history) when they are the exact population among whom lung cancer rates are rising.

Proposed Solution: Leveraging expertise of academic research centers (Massachusetts General Hospital, Broad Institute, and Stanford University) and a non-profit managed-care consortium (Kaiser Permanente), the Dream Team will develop a test called the Lung Cancer Interception Assay (LCIA) to complement LDCT screening.

The proposal is novel in that it will develop complex computational algorithms to combine high-sensitivity/high-accuracy blood-based molecular biomarkers with image-based biomarkers to create the  LCIA assay. At the end of the award period, a streamlined product, the LCIA, will be ready to use in population-level definitive trials for the early detection of lung cancer.

Circulating tumor cells (CTCs) are cancer cells that break away from either the primary tumor or metastatic sites. Increasingly, CTCs have been used as a readily accessible source of tumor cells (“liquid biopsy”). However, shortcomings in current CTC technologies limit downstream analyses to assessment of a selected set of nucleic acid markers. Genome and transcriptome-wide analyses of CTCs have been hampered by the low purity of CTC isolates. The complex and protracted nature of CTC capture protocols further impedes analysis.

Dr. Kulkarni and his group have developed a CTC capture technology known as Vortex Chip, which allows for rapid isolation of highly purified CTCs. In addition to standard immunofluorescence, they have generated proof-of-principle evidence that their capture technology allows for analysis of genetic material. Moreover, because the Vortex Chip isolates CTCs based on their size, their chip does not require antibody-based capture that can potentially bias isolation of CTC subpopulations. Serial CTC analyses performed in the context of treatment changes can characterize the mutational landscape of tumors as they evolve in response to therapy and thereby identify molecular predictors and drivers of treatment resistance and sensitivity to novel anti-tumor therapies.

Their project has two goals: 1) validate use of CTCs as biomarker in lung cancer and 2) explore use of CTC analysis to obtain genetic information about the tumor. They hypothesize that the unique microfluidic characteristics of lung CTCs will drive rapid isolation of pure CTC populations for analysis to characterize heterogeneity and profile therapeutic responsiveness.

Better methods are required to accurately risk stratify patients with a solitary pulmonary nodule (SPN) who may undergo unnecessary procedures to exclude a cancer diagnosis. 18F-FDG Positron Emission Tomography (PET) is a widely available clinical test used to evaluate concerning SPNs and stage malignant lung nodules. It therefore facilitates clinical assessment but remains an imperfect tool for the diagnosis, localization, and prognostication of SPNs, be they infectious or malignant in nature. Furthermore, it performs well for staging lung cancer, but inaccurately categorizes patients in some cases who receive futile thoracotomies for disseminated disease, or conversely, are undertreated for localized disease. The applicant therefore plans on investigating whether circulating molecular biomarkers can increase the utility of 18F-FDG-PET imaging in clinical practice using statistical models that incorporate in vivo and in vitro diagnostics The concept here is “one-stop shopping,” where a patient can obtain routine molecular imaging and molecular diagnostics from routine blood work during an appointment that in combination increase the accuracy of a clinician’s diagnosis and facilitate the appropriate decision-making process. For this proposal we will develop a model that incorporates a circulating microRNA profile to discriminate infectious from malignant SPNs for patients along with clinical and FDG-PET data and, secondly, identify patients with malignant nodules and detectable circulating tumor cells to determine whether these cells upstage or augment clinical staging or prognosis post-operatively when compared to FDG-PET alone.