Some tests, such as the Pap test, directly examine cellular
shape, or histological analysis, to look for abnormal cells.
The Pap test has contributed significantly to the 99%
reduction in deaths from cervical cancer in the U.S. by
identifying the precancerous cells to allow for their removal,
thus preventing the progression to cancer. The PSA
screening for prostate cancer has resulted in earlier
detection and intervention. This approach leads to fewer
severe side effects from treatment and a better quality
Imaging technologies have also improved our ability to
detect and screen for cancer. Routine mammography
screening, although the results have been variable, has been
shown to reduce breast cancer deaths by as much as 29%
for women in their 40s. Likewise, colonoscopy detects pre-cancerous polyps so that they can be removed before they
develop into advanced disease. This early intervention is
estimated to have reduced colorectal cancer deaths by 50%.
Finally, earlier this year, researchers reported that, among
current and former heavy smokers, spiral CT screening
reduced lung cancer mortality by 20% by identifying small
tumors; however, this is an early result and more work
needs to be done before it is applied population wide.
New imaging technology will make identifying premalignant
lesions and early disease more effective, thus providing
opportunities for chemoprevention strategies, more effective