Testing for cancer is controversial in cases when it's not yet known if the actual test actually saves lives. The controversy arises when it's not clear if the advantages of screening outweigh the risks associated with follow-up diagnostic tests and most cancers treatments. For example: when testing for prostate cancer, the PSA test may detect small cancers that could never become life threatening, but once detected will result in treatment.
This situation, called overdiagnosis, puts men in danger for complications from unnecessary treatment for example surgery or radiation. Follow up procedures accustomed to diagnose prostate cancer (prostate biopsy) could cause side effects, including bleeding as well as infection. Prostate cancer treatment could cause incontinence (inability to manage urine flow) and erection dysfunction (erections inadequate for sexual intercourse). Similarly, for breast most cancers, there have recently been criticisms that breast screening programs in certain countries cause more problems compared to they solve. This is because screening of women within the general population will result in a lot of women with false positive outcomes which require extensive follow-up research to exclude cancer, leading to using a high number-to-treat (or number-to-screen) to avoid or catch a single situation of breast cancer early.
Cervical cancer screening via the Pap smear has got the best cost-benefit profile of all of the forms of cancer screening from the public health perspective as, being largely the result of a virus, it has clear danger factors (sexual contact), and the natural progression of cervical cancer is it normally spreads slowly over quite a few years therefore giving more time for that screening program to catch this early. Moreover, the test itself is simple to perform and relatively inexpensive.
For these reasons, it is important that the advantages and risks of diagnostic procedures and treatment be taken into consideration when considering whether to take on cancer screening.
Use of medical imaging to find cancer in people without obvious symptoms is similarly marred along with problems. There is a significant danger of detection of what may be recently called an ''incidentaloma'' - a benign lesion which may be interpreted as a malignancy and encounter potentially dangerous investigations. Recent studies of CT scan-based testing for lung cancer in smokers have experienced equivocal results, and systematic screening isn't recommended as of July 2007. Randomized clinical trials of plain-film upper body X-rays to screen for lung cancer in smokers show no benefit for this strategy.
