1,721,875 research outputs found
Oral contraceptives and ovarian cancer
No full textThe protection conveyed by oral contraceptives against ovarian cancer risk is one of the best established and most important features of epithelial ovarian cancer on a public health scale. Ovarian cancer incidence and mortality rates have been declining in most developed countries for women born after 1920, and the decline was greater in countries where oral contraceptive use has been more widespread. Thus, data from descriptive epidemiology are consistent with a favourable effect of oral contraceptives on ovarian cancer risks. The overall estimated protection from cohort and case-control studies is approximately 40% in ever oral contraceptive users, and increases with duration of use to more than 50% for users of 5 years or longer. The favourable effect of oral contraceptives against ovarian cancer risk persists for at least 10-15 years after use has ceased, and it is not confined to any particular type of oral contraceptive formulation. However, available data do not provide definite evidence for more recent low-dose formulations and for longer periods of latency or recency of use. The protection is also observed on borderline malignancy ovarian neoplasms, and probably on benign epithelial cysts as well. There is suggestive evidence of some protection for sex-cord-stromal cancers, but not for germ cell neoplasms. In terms of biological mechanisms, oral contraceptives are thought to act on ovarian cancer risk by affecting the lifetime number of ovulations. The protection attributable to oral contraceptives on ovarian cancer risk is one of the major issues on any individual risk/benefit assessment and public health evaluation of this type of contraceptive use
Oral contraceptives and colorectal tumors : a review of epidemiologic studies
No full textOver the last two decades, the mortality rates of colorectal cancer in many developed countries have declined in women but not in men. One of the explanations of this difference between the genders may be the favorable influence of the spread of exogenous female hormone use (i.e., oral contraceptives [OC] and hormone replacement therapy) Reduced risk in ever-users of OC was found in three of four cohort studies available on this topic, and was significant in the one based on colorectal cancer mortality. The fourth one showed no difference. Of 11 case-control studies (or groups of studies), none showed significantly elevated risk. Five reported lowered colorectal cancer risk among ever-users, with a significant inverse association in the largest investigation available. Recent OC use, more than long duration use, seemed to be related to some risk reduction. One cohort study and three case-control investigations suggested that OC use was not related to the risk of colorectal adenomatous polyps. Thus, at present, it seems that OC use does not increase and may even have a favorable effect on either incidence or mortality of colorectal cancer
[Exogenous estrogens and carcinoma of the endometrium: a critical analysis of the literature]
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Nutrition and gastric cancer
No full textThe reasons for the worldwide decline in stomach cancer incidence and mortality rates are not fully understood, but dietary changes are clearly implicated. While the possible mechanisms of gastric carcinogenesis and the impact of Helicobacter pylori eradication remain open to debate, at least two practical recommendations - to increase fruit and vegetable intake, and to reduce consumption of salt - are already supported by epidemiological evidence. These dietary recommendations may also be beneficial in the prevention of other cancers and chronic diseases. Promising evidence of a favourable effect of certain vitamins, such as vitamin C and E and beta-carotene, and minerals, such as selenium, justifies additional investigation
Alcohol and the risk of cancers of the stomach and colon-rectum
No full textAlcohol drinking is strongly related to cancer of the upper digestive tract, but the pattern of risk with alcohol drinking is clearly different for cancer of the stomach and colon-rectum. All twelve cohort studies and three-quarters of 40 case-control investigations on the topic weigh against the possibility of a substantial effect of alcohol consumption on the risk of stomach cancer. Evidence is still insufficient to establish whether cancer of the cardiac region of the stomach is related to alcohol intake to any different extent than the rest of the stomach. With reference to colorectal cancer, different types of epidemiological studies are consistent in suggesting some direct relations with alcohol drinking. The association, however, is moderate, and an elevated risk of a factor 2--or even of a factor 1.5--for both cancers of the colon and rectum can now be excluded even for the highest levels of alcohol consumption
The clinical relevance of epidemiology: an overview
No full textEpidemiology is one of the areas of medical research which by definition should have immediate clinical implications, since its inferences are based on and apply to humans and should in theory be directly transferable to clinical and preventive measures. However, interchange of information has not always been easy, and this has constituted a substantial drawback to both the epidemiologist and the clinician. This review paper will provide some points for discussion, with special emphasis on cancer epidemiology and aspects of specific interest to the clinician, i.e., quantification and risk assessment for primary prevention and cost/benefit evaluation for secondary prevention and cancer treatment. Quantitative assessment is of major importance for the oncologist in at least three areas: cancer trends (descriptive epidemiology), cancer risks (analytical epidemiology), and preventive and therapeutic measures (clinical epidemiology)
Reproductive factors and colorectal cancer
No full textDescriptive and analytical epidemiology have suggested that cancer of the colorectum may have reproductive correlates similar to those of breast cancer (e.g., protection by parity and early age at first birth), but the evidence is still controversial. We therefore reviewed published data from 15 case-control investigations, two cohort studies, and one cancer registry-based study from seven different countries. With reference to parity, statistically significant protection for colorectal cancer was found in three case-control studies; in four other studies, significant inverse relationships of parity were observed with colon cancer, but not with rectal cancer. Among the remaining 12 studies, relative risks below unity for parous or multiparous women were observed in four. There was no appreciable trend in risk in four others; in two, there was nonsignificant increased risk with parity; and in one, a significant increased risk. Information on age at first birth was available from 12 studies. Three reported significant trends of increased risk with increasing age at first birth--one found a direct association of borderline significance; six indicated no evidence of association; and two reported an inverse trend in risk of borderline significance. Findings on age at menarche were inconsistent and mostly negative, although an inverse significant association was reported, especially regarding colon cancer, in one investigation. In all the six studies, which provided information on age at menopause, there was a hint of protection, although nonsignificant, for women who underwent natural menopause at an older age. Two studies reported a direct association of colorectal cancer with use of oral contraceptives, and another showed an inverse relationship with the use of menopausal estrogens
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