SCREENING FOR CANCER - IS IT USEFUL

Screening is a diagnostic activity applied to whole populations, or de fined sections of populations, with the aim to detect the signs of dis ease before there are symptoms. The rationale of screening is the assu mption that disease detected early is likely to be curable. When setti ng up a screening programme, the epidemiology and the natural history of the condition to be screened for, the sensitivity and specificity o f the screening method, its acceptability, its dangers and its costs n eed 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 r egular inspection early; for colorectal cancer, the best screening met hod seems to be to offer one colonoscopy at the age of 55 and so ident ify those at risk; there is no useful screening method for bronchial c arcinoma; serum prostate specific antigen estimation augmented by rect al ultrasound examination of the prostate will detect most prostatic c ancers early but it is difficult to know what the therapeutic conseque nces are; carcinoma of the uterine cervix has been eliminated in middl e class western society possibly with the help of cytological screenin g 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.