Rationale: Lung cancer is the leading cause of cancer and cancer-related deaths in the United States and worldwide. Despite recent advances in early detection and treatment, most patients with lung cancer ultimately die of their disease. That said, patients who present with early-stage lung cancer that has not spread to lymph nodes or other tissues are often curable by surgery or radiotherapy. However, approximately one-third of early-stage patients will eventually experience recurrence and spread of their cancer, even though all known tumor had been removed or destroyed. Currently, there are no tests that allow doctors to identify which lung cancer patients are likely to develop recurrence, and developing such tests is an important goal for lung cancer research.

It is well known that blood contains a small amount of genetic material, or DNA, that is outside of cells (i.e., "cell free") and that circulates throughout the body. Lung cancers continuously release some of their DNA into the blood and therefore the blood of lung cancer patients contains a mixture of tumor and normal DNA. Cell free tumor DNA in blood could potentially be used as a sensitive, personalized biomarker to test if cancer is present somewhere in the body.

Objective: The objective of our study is to develop new methods for detecting the presence of cell free lung cancer DNA in the blood of lung cancer patients. Detection of tumor DNA in blood requires being able to differentiate between normal and tumor DNA, since both are present. This can be accomplished by identifying specific mutations that are present in tumor but not normal DNA. Indeed, in a small subset of lung cancer patients in which specific mutations can be identified, circulating cancer DNA can be detected in blood using sensitive assays. Unfortunately, the majority of lung cancer patients do not have one of the few mutations that are routinely tested for in the clinic, and this makes it impossible to test for the presence of cancer DNA in their blood. We propose to develop a method for detecting cancer DNA in blood that will allow doctors to create personalized biomarkers for every lung cancer patient.

Our method is made possible by the recent development of new sequencing technologies that allow the rapid and relatively inexpensive sequencing of cancer genomes, thus identifying all of the genetic mutations that are contained within the cancer but not the normal cells of a given patient. The new sequencing technologies make it possible to design personalized tests of circulating tumor DNA that will be unique to each patient. Dr. Diehn's laboratory maintains a repository of blood samples from lung cancer patients, and samples from this repository will be used to compare two different techniques for measuring tumor DNA in blood. The technique that we find to be superior will then be tested on new lung cancer patients treated at Stanford in order to evaluate its clinical usefulness. Our hypothesis is that lung cancer patients at highest risk for recurrence will have detectable cancer DNA in their blood even after all known tumor lesions have been removed or destroyed.

Applicability of the Research: Our proposal is directly applicable to lung cancer patients since we will study tumor and blood samples collected from patients rather than relying on animal models or cultured cell lines. Given that our method uses small volumes of blood, the risks to patients will be negligible. For this study, we will focus specifically on early-stage lung cancer patients in order to develop a test to identify which of these patients are most likely to experience recurrence. Such a test would have immediate clinical applications. For example, if doctors could identify the high-risk patients early on, they could design clinical studies testing new treatment approaches that could cure a larger fraction of these patients. Measuring circulating tumor DNA could also be helpful for patients with more advanced lung cancers, since it could help identify patients who have responded completely to chemotherapy and/or radiotherapy or could detect recurrence of tumor before it becomes visible on CT (computer tomography) or PET (positron emission tomography) scans. Thus, this proposal has a significant chance of decreasing deaths from lung cancer to improve the health and welfare of the military and the American public. Additionally, while we will focus on lung cancer, our approach could be applied to most other cancers and could thus have even broader clinical impact.