The early detection of cancer could lead to vastly improved patient outcomes. We aim to identify cancer biomarkers within the body at early disease stages, permitting detection before symptoms arise. We are developing implantable nanosensors, using the unique optical properties of carbon nanotubes, to facilitate non-invasive detection via optical detection through living tissues. The sensors could enable early detection of cancer in people at high risk for the disease, in successfully treated patients to monitor recurrence, or in patients who are undergoing treatment to inform clinical decisions.