Screening for lung cancer.

The survival from bronchogenic carcinoma is highly dependent upon stage at the time of treatment. This is particularly true for squamous cell carcinoma, adenocarcinoma, and large cell carcinoma, but holds true for small cell carcinoma as well. The problem presented to the medical profession has been to find a practical means of detecting lung cancer while it is still at an early stage. Three studies in progress have indicated that a larger proportion of the patients may be found to have early stage lung cancer when screened with a combination of chest X-rays and sputum cytology. However, the detection of these early stage cases has not yet been translated into an improvement in the overall mortality rate from lung cancer.     

Screening for cancer.

Screening has proved effective for only two cancer sites, the breast and the cervix uteri. Only for these, therefore, should screening be a part of routine clinical practice. The degree to which screening is effective depends on whether appropriate groups are screened. For cancer of the breast, current evidence justifies mammographic screening every two years only from the age of 50, continuing at least to the age of 70. The place of breast self-examination and physical examination of the breasts is under investigation, but these procedures should probably be used in all women after the age of 40. For cancer of the cervix, nearly maximal efficacy is obtained by screening sexually active women every three years from the age of 25 to 60. Older women who have not been screened regularly should be screened. Other screening techniques to detect cancers, such as the rectal examination, sigmoidoscopy, and fecal occult blood tests for colorectal cancer, are still experimental. Organizational and other difficulties will prevent screening programs from making a major contribution to reducing overall cancer mortality by the year 2000. If organizational problems can be overcome, however, screening may control invasive cancer of the cervix and make a major contribution in reducing breast cancer mortality in the future.     

Screening for colorectal cancer.

In the United Kingdom there are almost 31,000 new cases of colorectal cancer each year and nearly 20,000 deaths. It is the second most common cause of all deaths from cancer in the United Kingdom. The efficacy of screening with faecal occult blood tests to detect and treat tumours at an early stage, and thereby to reduce mortality, is currently being assessed in several randomised controlled trials. In general, faecal occult blood tests have a low sensitivity and only moderate levels of uptake among the population invited for screening. Until the studies in Denmark, Sweden, and Nottingham report their findings, there is no case for providing such screening routinely to an asymptomatic population. Detecting and removing premalignant adenomas by flexible sigmoidoscopy could be more effective than detecting early localised, asymptomatic cancers in reducing deaths from colorectal cancer. It is estimated that screening people at about the age of 60 by a single flexible sigmoidoscopy examination with appropriate colonoscopic surveillance could prevent 5500 cases of colorectal cancer and 3500 deaths in the United Kingdom each year. A randomised controlled trial to confirm these observations should be seen as a priority.     

Screening for breast cancer. Report from Edinburgh Breast Screening Clinic.

As part of a trial to determine the feasibility of screening for breast cancer, 3952 women aged 40--59 years were screened once or more over two years. They represented 82% of those invited by a personal letter from their GPs. Each woman underwent mammography, two clinical examinations, and, usually, thermography. Further investigations included needle aspiration of cysts, xeromammography, and biopsy. Of the 125 women who underwent biopsy, 18 proved to have cancer. Because of the high response rate and consequent large sample of normal women the biopsy and cancer detection rates were low. Clinical examination and mammography together were more effective in detecting significant lesions than either procedure alone, and knowledge of the mammographic findings enabled the examiner to detect more abnormalities. Screening was expensive: each cancer detected cost about 6000 pounds, excluding data processing, surgical, and pathological costs. The clinic has now adopted a more simplified screening regimen, which should reduce costs, but more accurate imaging techniques and ways of identifying high-risk cases are needed.