Clinical data that is routinely available in electronic medical records of all patients is particularly valuable, since it is inexpensive and can be easily included in retroactive modeling studies. Such clinical data is summarized in the following table. It should be noted that there are many exceptions to these rules; for example, while elderly age is an important risk factor for most cancers, bone cancers and some leukemias tend to occur most commonly in children (National Cancer Institute, 2015). The National Cancer Institute is an excellent resource for a more detailed breakdown of clinical risk factors for cancer (www.cancer.gov):