Considerations for conducting epidemiologic case-control studies of cancer in developing countries.

The challenges involved in conducting epidemiologic studies of cancer in developing countries can be and often are unique. This article reports on our experience in performing a case-control study of invasive cervical cancer in four Latin American countries (Columbia, Costa Rica, Mexico, and Panama), the summary medical results of which have been published in a previous issue of this journal (1). The study involved a number of principal activities--mainly selecting, conducting interviews with, and obtaining appropriate biologic specimens from 759 cervical cancer patients, 1,467 matched female controls, and 689 male sex partners of monogamous female subjects. This presentation provides an overview of the planning and methods used to select the subjects, conduct the survey work, and obtain complete and effectively unbiased data. It also points out some of the important advantages and disadvantages of working in developing areas similar to those serving as locales for this study.

[The risk factors of invasive carcinoma of the cervix uteri in Latin America]. / Factores de riesgo de carcinoma invasor del cuello uterino en América Latina.

A study of 759 patients with invasive cervical cancer, 1,430 controls, and 689 sexual partners of the participants who declared that they were monogamous was conducted in Colombia, Costa Rica, Mexico, and Panama from January 1986 to June 1987, to evaluate the risk factors associated with this neoplasm. The principal risk factors identified were: initiation of sexual relations by the woman at an early age, number of stable sexual partners (relationships of more than three months' duration), number of liveborn children, presence of DNA from human papilloma virus (HPV) types 16 or 18, history of venereal disease, lack of exposure to early detection programs, deprived socioeconomic conditions, and number of sexual partners of the partners of the monogamous women. Smoking increased the risk in those women who were shown to have DNA from HPV types 16 or 18. Fifty percent of the patients and 29% of the controls said they had never had a cytological examination (Papanicolaou test). No association was observed between the presence of HPV and sexual behavior. The study showed the need for further research on the possible mechanisms involved in carcinogenesis and infection. The common denominators of the risk factors mentioned are underdevelopment and poverty, which affect broad sectors of these populations. Mass detection programs targeting high-risk groups can reduce the high incidence of cervical cancer in Latin America.

Risk factors for invasive carcinoma of the uterine cervix in Latin America.

A study of 759 cervical cancer patients, 1,430 controls, and 689 sex partners in four Latin American countries has made it possible to assess the influence of multiple factors upon the risk of invasive cervical cancer. The principal risk factors identified were the woman's age at first coitus, the number of her steady sex partners, her number of live births, the presence of DNA from human papillomavirus (HPV) types 16 or 18, a history of venereal disease, nonparticipation in early detection programs, and low socioeconomic status. There is good reason to believe that extensive detection programs directed mainly at high-risk groups in the Americas can reduce the high incidence of cervical cancer in this Region.

PIP: Risk factors for invasive carcinoma of the cervix were analyzed in 759 cancer patients from Mexico City, Costa Rica, Panama and Bogota, Colombia, in comparison with 1430 controls and 689 male partners, by interview and analysis for human papilloma virus (HPV) types 16 and 18. Community and hospital controls were combined for the analysis, since they did not differ significantly. Average age is 1st coitus was 17.4 years for patients and 18.8 for controls. A relative risk of 1.8 resulted for women with coitus at age 14-15 compared to age 20 or more. Those with 6 or more sex partners had a risk of 1.7 compared to monogamous women, with a significant trend (p0.0001). Anal sex conferred a risk of 1.5-1.9 depending on frequency. There was a significant trend toward increasing risk for number of pregnancies up to 5.1 for 14 or more pregnancies, and especially for number of live births, with a risk of 3.7 for 12 of more. No relationship was found between risk and stillbirths, or spontaneous or induced abortions. Cesarean sections and prenatal care reduced risks. DNA from HPV types 16 or 18 was found in 62% of patients and 32% of controls. A relative risk of 1.7 was found in women who had HPV and who smoked. Risks decreased with rising educational level, and with increasing socioeconomic status. Neither oral contraception nor condoms affected risks. Factors associated with male partners related to increased risk were his number of sex partners (25 vs 5 of less) and lower education. Not having Pap smears increased risk to 2.5. Providing cervical cytology to women at risk is an obvious intervention needed to reduce the several-fold higher incidence of cervical cancer in Latin American compared to that in developed countries.

Case-control study of human papillomaviruses and cervical cancer in Latin America.

Human papillomavirus (HPV) types 16 and 18 have been implicated as risk factors for cervical dysplasia and neoplasia. However, most studies have been observational, uncontrolled and conducted in populations at low risk for invasive cancer. We report a pilot case-control study of incident invasive cervical cancer in Panama, Costa Rica and Bogota, Colombia. Between July and September 1985 we enrolled 46 consecutive newly diagnosed invasive cervical cancer cases and 51 age-matched control women. Subjects were interviewed and samples collected for HPV DNA assays. HPV infection was defined by a filter in situ DNA hybridization technique under non-stringent and stringent conditions against HPV-6/11, 16 and 18 DNA probes. More cases (91%) than controls (63%) had HPV DNA detected (non-stringent) and more cases than controls had HPV-16 or 18 DNA (67% vs. 43%, p = 0.02). Age at first intercourse was the most significant risk factor for HPV 16/18 infection in all subjects. Smoking was significantly associated with cervical cancer (52% of cases vs. 27% controls) but was not associated with HPV infection.