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The occurrence of extrahepatic malignancy was studied in 195 unselected patients who satisfied predetermined biochemical, immunological, and histological criteria for the diagnosis of primary biliary cirrhosis. The incidence of breast cancer in women with primary biliary cirrhosis was found to be significantly higher than in an age and sex matched control population from the same well defined geographical area (p less than 0.0015). The association of breast cancer and primary biliary cirrhosis remains unexplained, though diminished immunological surveillance, fat soluble vitamin deficiency, or endocrine dysfunction may play a part.

Data from a hospital based case-control study of lung cancer in Western Europe were used to examine changes in the risk of developing lung cancer after changes in habits of cigarette smoking. Only data for subjects who had smoked regularly at some time in their lives were included. The large size of the study population (7181 patients and 11 006 controls) permitted precise estimates of the effect of giving up smoking. Risks of developing lung cancer for people who had given up smoking 10 or more years before interview were less than half of those for people who continued to smoke. The reduction in risk was seen in men and women and in former smokers of both filter and non-filter cigarettes but varied by duration of smoking habit before giving up. The protective effect of giving up became progressively greater with shorter duration of smoking habit. The risks after not smoking for 10 years for both men and women who had previously smoked for less than 20 years were roughly the same as those for lifelong non-smokers. Reducing the number of cigarettes smoked a day or switching from non-filter to filter cigarettes also lowered the risk of developing lung cancer but not to the extent associated with giving up smoking.