Early detection of a disease is the goal of screening for it.
Early detection can reduce mortality. Early detection, however, does not imply mortality reduction. For instance, if there is no effective therapy, then early detection — including treatment — will not reduce mortality.
The American Cancer Society lays down guidelines every year on screening for early detection of colorectal, prostate, breast, endometrial, and cervical cancers.
The goal of cancer screening is to detect tumors at an early stage so that treatment is more likely to be successful.
The screening tool must be noninvasive, inexpensive, and specific for the tumor screened. Fecal occult blood test, flexible sigmoidoscopy, colonoscopy, prostate specific antigen test, breast self examination, mammography, and Pap test are some examples of tests or procedures done for early detection of cancers.