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- [Narrator] Cancer treatment has made real strides over the years, improving some existing therapies, and even developing brand new approaches. This is possible because our knowledge of cancer continues to grow. One thing we've learned is that doctors often need more information about each patient's disease. Imaging like CT scans can reveal tumors only after they've developed, but subtler science can enable earlier diagnosis and identify the most effective treatments. These signs are called biomarkers, and they include things like genes, proteins and chemicals that tell doctors what's going on inside cancerous cells. Imagine you are monitoring a virus spreading through a city. It's not feasible to visit every person to see how they're feeling and test everyone with symptoms, but you could easily test samples from the sewage system, identifying viruses and tracking their spread in the community. In a similar way, biomarkers can indicate the presence of cancer without looking at the cancer directly. Wherever the tumor may be hiding, it can cause changes that can be seen elsewhere by looking at a small blood sample, for example. Beyond the possibility of detecting an early stage cancer, biomarkers can help doctors diagnose exactly what type of cancer you have. Even for a single organ, there are multiple types of cancer, and they behave differently and demand different treatments. Even after treatment starts, biomarkers can still be helpful, showing how the cancer is responding. Take lung cancer for example. It often isn't caught until it has progressed enough to cause significant symptoms. At that point, a tissue sample will be used to find out if it's a small cell cancer or one with much more common non-small cell cancers, which include adenocarcinoma, squamous cell carcinoma, and large-cell carcinoma. Different types require different chemotherapy, which may or may not be combined with radiation treatment and surgery, but high levels of one specific enzyme in a blood sample can indicate the presence of small-cell lung cancer rather than another type of cancer. One example of a biomarker that aids diagnosis. Tumor biopsy samples and blood samples are now commonly tested for a growing list of genetic mutations. Each mutation is involved in the cells out of control growth processes. Targeting these mutations provides a way to uniquely disrupt the function of only the cancer cells since healthy cells do not have these mutations. It's a bit like the way your car key can't start other people's cars. The targeted therapies that focus on these mutations are much more selective about which cells they harm. They avoid the problems that come from chemotherapy drugs that do collateral damage to the other cells in the body. Biomarkers also enable new immunotherapy approaches that help the body's immune system to attack cancer cells. One such biomarker is a protein found on the surface of some cancer cells. This protein can shut down immune responses, acting a bit like kryptonite to Superman. We've made antibodies that bind to the protein, blocking its ability to shut down immune cells. If we use the protein as a biomarker, then we can know these antibodies are more likely to work against the cancer. Each of these biomarkers provides a valuable glimpse inside cancer cells providing useful information. They aren't perfect though. We could always use bigger collections of biomarkers that can paint a more complete picture. That takes research to identify new and important biomarkers as well as new tests sensitive enough to measure them using a small sample of blood or tissue. Advances in biomarker testing could lead to earlier and easier detection of cancer, catching it when it's easier to treat. As the list of available treatment options expands, biomarkers will enable doctors to better predict which treatment will be the most successful for each patient. [bright music] [air whooshing]