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The WHO Collaborative Study of Neoplasia and Steroid Contraceptives: the influence of combined oral contraceptives on risk of neoplasms in developing and developed countries.
CONTRACEPTION. 1991 Jun; 43(6):695-710.A hospital-based case-control study was conducted in 8 developing and 3 developed countries to determine whether use of combined oral contraceptives (OCs) alters risks of various cancers. An observed trend of increasing risk of invasive cervical cancer with duration of use may not represent a causal relationship and is the subject of further study. Decreased risks of ovarian and endometrial carcinomas in users likely indicate a protective effect of OCs, the degree of which was similar in developing and developed countries. A small increase in risk of breast cancer in recent and current users was found to be somewhat greater in developing countries. Both causal and noncausal interpretations of this finding have been offered. No associations were found between OCs and in situ cervical, hepatocellular, cholangio, or gallbladder carcinomas, or uterine sarcomas. However, the ability of this study to detect alterations in risks for these neoplasms in longterm users was low. (author's)
BULLETIN OF THE WORLD HEALTH ORGANIZATION. 1986; 64(3):375-82.This memorandum from a World Health Organization (WHO) meeting held in 1985 summarizes available epidemiologic data from human studies, including the WHO Collaborative Study of Neoplasia and Steroid Contraceptives, on the association between depot-medroxyprogesterone acetate (DMPA) use and neoplasia. The WHO Collaborative Study is collecting data on cases and controls from 14 collaborating centers in 11 countries. Analysis of preliminary findings regarding cancers of the endometrium, ovary, liver, and breast suggest that there is no increased risk in DMPA users. The relative risk estimates for these sites are 0.3 for endometrial cancer, 0.7 for ovarian cancer, 1.0 for liver cancer, and 1.0 for breast cancer. The issue of a causal association between DMPA use and cervical cancer is less clear. The adjusted relative risk for cervical cancer was a nonsignificant 1.2; however, somewhat higher risks were noted in subgroups of longterm (over 4 years) users. Although the WHO study is the 1st to provide reliable data on DMPA and neoplasia, its findings must be regarded as tentative. At this point the data are insufficient to assess the influence of DMPA on risk among longterm users or risk long after initial exposure.
Bulletin of the Pan American Health Organization. 1983; 17(3):323.A World Health Organization (WHO) Consultative Group on Hepatitis met during July 1983 to draft a global program for viral hepatitis control. At this time, hepatitis viruses infects tens of millions of people every year. These viruses can be transmitted by the fecal-oral route, in blood or certain blood products, and through intimate personal contact. Of the various forms (heptitis A, hepatitis B, and hepatitis non-A, non-B) hepatitis B arouses particular concern because it can produce chronic liver disease and premature death. Currently, there are over 200 million persistent carriers of this virus, many of whom will die of chronic liver damage. Firm evidence recently shows a clear cause and effect relationship between infection with hepatitis B virus and primary liver cancer, a common cancer that claims hundreds of thousands of lives a year. The July meeting made recommendations to improve the situation. One of the most important recommendations was to strengthen national capabilities to control viral hepatitis. The group also reviewed available diagnosis and control methods and suggested areas where action by the WHO would be most effective. The group agreed that the availability of safe and effective vaccines against hepatitis B provides a unique opportunity to break the chain of transmission and to prevent acute and chronic liver disease, including primary liver cancer. There has been concern that the plasma-derived hepatitis B vaccines could contain transmissible agents that might be implicated in the acquired immune deficiency syndrome (AIDS). It was felt that much care needs to be taken in selecting plasma donors and in purifying the immunizing component of the vaccine, known as hepatitis B surface antigen, so as to ensure a very high degree of purity and freedom from all infectious agencts. No evidence exists at this time of AIDS transmission by any hepatitis B vaccine.
Bulletin of the Pan American Health Organization. 1983; 17(2):212.A World Health Organization (WHO) sponsored scientific meeting concludes that hepatitis B vaccine presents unique opportunities for preventing a common type of human cancer by vaccination. Should these prospects be realized, it would be the 1st time an important human cancer has been prevented in this way. The 5-day meeting, held in February 1983, brought together specialists in biostatistics, epidemiology, molecular biology, pathology, virology, and vaccine development and production from 16 countries. The topic at the meeting was liver cancer, one of the 10 most common cancers in the world and one of the most prevalent cancers in developing countries. The evidence for the implication of hepatitis B virus in the etiology of primary liver cancer is based upon epidemiologic and geographic observations of a strong association between hepatitis B infection and this form of cancer and also upon recent results of molecular biology studies showing integration of hepatitis B viral DNA into the host's genetic material. About 80% of all liver cancers are thought to occur as a result of infection with hepatitis B virus. Actual development of such cancers is believed to proceed through a series of intermediate stages, including establishment of a persistent infection with the virus, the hepatitis B carrier stage, and integration of the virus into the host genome. Worldwide, survival, and persistence of the hepatitis B virus depends on a huge reservoir of human carriers, estimated conservatively to number over 200 million. Prolonged "shedding" of the virus by a portion of these carriers and its transmission to others by various routes helps to account for the high incidence of the disease. In many parts of the world perinatal infection and infection in early life play a very important role in transmission and often lead to continuing infection. Feasibility studies conducted in recent years in several countries with 2 newly developed hepatitis B vaccines demonstrated that immunization of babies can prevent natural infection with hepatitis B virus and also can prevent development of a persistent hepatitis B infection. It seems an appropriate time to take international action to plan and initiate a number of field intervention trials with the new vaccines among populations known to have high prevalence of hepatitis B infection, the hepatitis C carrier state, and liver cancer.