For certain cancers, including prostate, breast and colorectal, many of the cases are detected through screening. People with cancers diagnosed through screening may have a better prognosis than people whose cancer was not detected through screening—but instead was found clinically as a result of symptoms. The “screen-detected” people have a better prognosis even if detecting the cancer by screening did not affect their age at death from cancer. This is because screen-detected cases are often found earlier in the natural course of their disease than cases that are not screen-detected (known as lead time bias) and slower-growing tumors are more likely to be detected by screening than faster-growing tumors (known as length bias). In most cases, SEER data do not indicate the way in which the cancer was detected (i.e, as part of a routine test, or by the patient and/or physician when noticing signs or symptoms). The data in the oral cancer survival calculator are not suspected to be affected by issues related to screening bias.
The U.S. Preventive Services Task Force has found poor evidence on whether screening exams can accurately detect oral cancer. They also, in their most recent review, found very little clear evidence on whether screening or early treatment improves long-term health among adults in general or adults at high risk of developing oral cancer in the United States. Therefore, they determined that there was insufficient evidence for or against oral cancer screening. See the Final Recommendation Statement.