Screening for cancer. Is it useful?
Screening is a diagnostic activity applied to whole populations, or defined sections of populations, with the aim to detect the signs of disease before there are symptoms. The rationale of screening is the assumption that disease detected early is likely to be curable. When setting up a screening programme, the epidemiology and the natural history of the condition to be screened for, the sensitivity and specificity of the screening method, its acceptability, its dangers and its costs need to be taken into account. Examining in the light of these criteria, the screening programmes advocated for the six commonest cancers one comes to the following conclusions: skin cancers can be detected by regular inspection early; for colorectal cancer, the best screening method seems to be to offer one colonoscopy at the age of 55 and so identify those at risk; there is no useful screening method for bronchial carcinoma; serum prostate specific antigen estimation augmented by rectal ultrasound examination of the prostate will detect most prostatic cancers early but it is difficult to know what the therapeutic consequences are; carcinoma of the uterine cervix has been eliminated in middle class western society possibly with the help of cytological screening and; the early detection of cancer of the female breast by means of mammography has proven to benefit women between the ages 50 and 65. In conclusion, some present cancer screening programmes are of definite but limited value.