Design and methods of a population-based natural history study of cervical neoplasia in a rural province of Costa Rica: the Guanacaste Project.

This paper reports on the enrollment phase of a population-based natural history study of cervical neoplasia in Guanacaste, a rural province of Costa Rica with consistently high rates of invasive cervical cancer. The main goals of the study are to investigate the role of human papillomavirus (HPV) infection and its co-factors in the etiology of high-grade cervical neoplasia, and to evaluate new cervical cancer screening technologies. To begin, a random sample of censal segments was selected and enumeration of all resident women 18 years of age and over was conducted with the aid of outreach workers of the Costa Rican Ministry of Health. Of the 10738 women who were eligible to participate, 10049 (93.6%) were interviewed after giving written informed consent. After the interview on cervical cancer risk factors was administered, a pelvic examination was performed on those women who reported previous sexual activity. The pelvic examination included a vaginal pH determination and collection of cervical cells for cytologic diagnosis using three different techniques. Additional cervical cells were collected for determination of the presence and amount of DNA from 16 different types of HPV, and two photographic images of the cervix were taken and interpreted offsite by an expert colposcopist. Finally, blood samples were collected for immunologic and micronutrient assays. Women with any abnormal cytologic diagnosis or a positive Cervigram, as well as a sample of the whole group, were referred for colposcopy, and biopsies were taken when lesions were observed. The enrollment screening will serve as the basis for a prevalent case-control study, and the members of the cohort free from serious disease will be followed actively, at intervals of no more than a year, to study the natural history of HPV infection and the origins of high-grade squamous intraepithelial lesions (HSIL). Details of the field operation are outlined, with particular reference to the realization of this kind of study in developing countries. Descriptive data on the prevalence of disease and exposure to various risk factors are also presented.

Human papillomaviruses and other influences on survival from cervical cancer in Panama.

OBJECTIVE: To determine the influence on survival from cervical cancer of human papillomaviruses (HPVs) and other factors including age, herpes simplex virus type 2 (HSV-2) antibody status, and number of pregnancies. METHODS: We followed 196 women diagnosed with invasive cervical cancer in Panama for an average of 32 months. Clinical and risk-factor information was obtained from these women through an interview and review of medical records. We assessed HPV DNA status by testing tumor specimens using polymerase chain reaction, Southern blot, and slot blot techniques. Kaplan-Meier survival curves and Cox proportional hazards model were used to assess the risk of mortality associated with selected variables. RESULTS: Eighty-one percent (N = 144) of the women tested for HPV were positive. Absence of HPV DNA was associated with a 1.9-fold excess risk of mortality (95% confidence interval [CI] 1.1-3.3) after controlling for age, clinical stage at diagnosis, number of pregnancies, and HSV-2 seropositivity. Women diagnosed with cervical cancer before the age of 30 had a ninefold excess risk of dying compared with those diagnosed at age 50 or older (relative risk [RR] 9.3, 95% CI 3.4-25.5). Parity was also an independent prognostic factor. Women with six or more pregnancies had a 2.5-fold excess risk of dying compared with women with three or fewer (95% CI 1.2-5.3). Years of education, presence of HSV-2 antibodies, age at first intercourse, number of sexual partners, oral contraceptive use, and cigarette smoking were not significantly associated with prognosis. CONCLUSION: These findings suggest that women negative for HPV DNA, those who are diagnosed at an early age, and those who have multiple pregnancies might have more aggressive tumors.

Determinants of the geographic variation of invasive cervical cancer in Costa Rica.

The incidence of cervical cancer in Costa Rica is about twice as high in the coastal regions as in the interior. To study these regional variations, we used data from a 1986-1987 case-control study of 192 Costa Rican women with invasive cervical cancer and 372 controls. Risk factors identified included the following: The study participant's (1) number of sexual partners, (2) age at first sexual intercourse, (3) number of live births, (4) presence of type 16/18 human papillomavirus (HPV) DNA, (5) venereal disease (VD) history, (6) Pap smear history, and (7) socioeconomic status. The adjusted relative risks (RR) and 95% confidence intervals (CI) for each of these risk factors were as follows: (1) > or = 4 vs. 1 sexual partner: RR = 2.0, 95% CI = 1.1-3.5; (2) age of initiation < or = 15 vs. > or = 18 years: RR = 1.5, 95% CI = 0.9-2.5; (3) > or = 6 vs. < or = 1 live birth: RR = 1.7, 95% CI = 0.7-3.9; (4) HPV 16/18 DNA in cervix: RR = 2.8, 95% CI = 1.9-4.2; (5) VD history: RR = 2.2, 95% CI = 1.2-4.0; (6) no Pap smear: RR = 2.4, 95% CI = 1.5-3.8; and (7) low socioeconomic status: RR = 2.0, 95% CI = 1.2-3.2. The population-attributable risks related to HPV detection, four or more sexual partners, six or more live births, no prior Pap smear, and low socioeconomic status were 39%, 38%, 29%, 23%, and 22%, respectively. Several of the sexual and reproductive risk factors were relatively more prevalent in the high-risk region, but Pap screening and detection of HPV were equally prevalent in the high-risk and low-risk regions. Though differences in screening quality (laboratory and follow-up) may have been involved, we conclude that the observed regional differences reflect behavioral more than screening differences. This suggests that screening programs should be more aggressive in the high-risk area, given the more frequent occurrence of the disease there. Failure to detect a higher prevalence of HPV in the high-risk region could reflect weaknesses in the in situ hybridization test employed. Alternatively, cofactors may have to be present in order for HPV to exert its role in cervical carcinogenesis.

Screening for cervical cancer in Latin America: a case-control study.

The beneficial effect of cervical cytology in reducing the incidence of invasive cervical cancer is well accepted, but many issues regarding specific patterns of screening remain to be resolved, and preventive programmes need to be adapted to regional characteristics. In a case-control study conducted in Latin America, we investigated cytological screening histories of 759 cases of invasive cervical cancer and 1430 controls, with participation rates of 99% and 96%, respectively. Fifty per cent of the cases and 29% of the controls reported never having been screened. Screening was less common among older, less educated and less parous women; non-users of oral contraceptives and women without histories of venereal diseases. There was also evidence that older women and those with multiple partners had longer intervals between examinations. The relative risk (RR) associated with no prior screening was approximately 3 and was not modified by other risk factors. Women reporting a Pap smear within 24-47 months before interview had the same RR as those examined within 12-23 months. Women tested longer ago had higher risks, but still much lower than women never examined. There was evidence that one examination is associated with less reduction in risk than two, regardless of the interval since last Pap smear. Screening appeared to reduce risk of both squamous cell carcinomas and adenocarcinomas. As expected, cases presenting at advanced stages were less likely to have been screened and reported longer intervals since their last examination. These results support the need to concentrate limited resources in the groups that need screening most, mainly older and less educated women who have never been screened.

A case-control study of nutrient status and invasive cervical cancer. I. Dietary indicators.

A study of 748 cases and 1,411 hospital and community controls in four Latin American countries evaluated the association between certain elements of diet and invasive cervical cancer. Subjects were interviewed about their adult consumption of 58 food items, including the major sources of putative protective agents (vitamin A, carotenoids, vitamin C, and folacin) as well as other behavioral and medical characteristics related to cervical cancer. Participation rates were above 95% for both cases and controls. After adjustment for age, study site, sexual and reproductive behavior, socioeconomic status, screening practices, and detection of human papillomavirus 16/18 by filter in situ hybridization, a slightly lower risk was observed for the highest quartiles of consumption of fruit and fruit juices, while no reductions in risk were associated with vegetables, foods of animal origin, complex carbohydrates, legumes, or folacin-rich foods. When nutrient indices were derived, significant trends of decreasing risk were observed for vitamin C (adjusted odds ratio (OR) = 0.69 for the highest vs. the lowest quartile; p for trend = 0.003), beta-carotene (OR = 0.68; p = 0.02), and other carotenoids (OR = 0.61; p = 0.003). Inclusion of vitamin C and beta-carotene in the same model attenuated the association with beta-carotene, while the association with vitamin C remained unchanged. The results are consistent with those of other investigations and provide support for a protective effect of vitamin C, carotenoids, and other substances found in the same fruits and vegetables against the development of invasive cervical cancer. However, the fact that the associations were driven by relation in two of the study sites and among women of higher socioeconomic status leaves open the possibility of selection bias or effects of unidentified aspects of dietary patterns.

A case-control study of serum folate levels and invasive cervical cancer.

Although small intervention trials have suggested that folate supplementation reduces cervical dysplasia, the association of blood folate concentrations with invasive cervical cancer risk has not been investigated in well-controlled epidemiological studies. A study was conducted with newly diagnosed Stage I and II invasive cervical cancer cases and controls in 4 Latin American countries. Ninety-five% of subjects donated blood samples, resulting in 330 case and 565 control serum samples analyzed for folate concentrations by radioassay. Cases did not differ significantly from controls in mean levels of folate (5.00 and 4.90 ng/ml, respectively). No associations were observed between quartiles of serum folate and risk of cervical cancer after adjustment for other risk factors, and no interactions with established risk factors were observed. Folate levels were also unrelated to risk among women who might have compromised folate status because of recent or extended oral contraceptive usage or multiple pregnancies. Further, mean levels of folate were similar by stage of disease, arguing against an effect of disease progression on serum values. These results do not support a role for serum folate in the etiology of invasive cervical cancer.

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.

Injectable contraceptives and risk of invasive cervical cancer: evidence of an association.

In a case-control study conducted in Latin America, the relationship of injectable contraceptive (IC) use to risk of invasive cervical cancer was analyzed while controlling for a variety of other risk factors, including female and spouse sexual behavior and infection with human papillomaviruses (HPV). Thirty-two cases and 82 controls reported ever having used IC. Women reporting use of IC for less than 5 years had an adjusted RR of 0.5 (95% Cl = 0.3-0.9), but users for 5 or more years had an RR of 2.4 (95% Cl = 1.0-5.7). The effect of prolonged IC use was stronger for women reporting first use 10 or more years before interview (adjusted RR = 3.4, 95% Cl = 1.1-24.9) and more than 5 years since last use (adjusted RR = 5.3, 95% Cl = 1.1-10.0). Cervical cancer risk associated with prolonged IC use was particularly high among women who reported never having had a Pap smear or having had one 2 or more years before interview (adjusted RR = 6.3, 95% Cl = 2.1-18.7). The reduced cervical cancer risk associated with short-term use of IC may reflect intensive Pap smear screening as the method is initiated. Although hampered by small numbers, these results suggest an adverse effect of prolonged IC use on cervical cancer risk, particularly among women who cease participation in screening programs after terminating usage, and indicate that long-term IC users should be monitored for cervical disease until more conclusive results are available.

[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.

Oral contraceptive use and risk of invasive cervical cancer.

A case-control study of 759 invasive cervical cancer patients and 1430 controls in Panama, Costa Rica, Colombia and Mexico enabled an evaluation of risk in relation to oral contraceptive use. Overall use was associated with a 21% nonsignificant elevation in risk, with some further increases in risk for more extensive durations of use. Although risks were similar for recent and non-recent users (RRs = 1.3 versus 1.2), recent long-term users were at highest risk (RR for 5+ years use = 1.7, 95% Cl 1.1-2.6). Relationships were similar for women with and without a recent Pap smear, arguing against detection bias. There was little evidence that other risk factors, including smoking and detection of human papillomaviruses (HPV), altered the effects of oral contraceptives. The risk associated with oral contraceptives was significantly increased for adenocarcinomas (RR = 2.2), whereas for squamous cell tumours the effect was minimal (RR = 1.1). These results provide some support for an adverse effect of oral contraceptives on cervical cancer risk, although possibly limited only to a subpopulation of cases.

Sexual behavior, venereal diseases, hygiene practices, and invasive cervical cancer in a high-risk population.

A case-control study of 759 women with invasive cervical cancer and 1430 controls in four Latin American countries evaluated risk in relation to sexual behavior, histories of specific venereal diseases, and hygiene practices. Early age at first sexual intercourse and increasing number of sexual partners were associated with significantly increased risks even after adjustment for their mutual effects. Risk increased to a twofold excess among women reporting first intercourse at 14 to 15 years of age compared with 20+ years. The number of steady sexual partners was a more important predictor of risk than the number of nonsteady partners, particularly before age 30, possibly reflecting the need for prolonged or repeated exposures to a transmissible agent, or different methods of protection against sexually transmitted diseases or pregnancy. Reported frequency of intercourse was not generally associated with risk, except among women reporting increased frequencies before 20 years of age. Histories of gonorrhea or crab lice were associated with increased risk, but histories of other venereal diseases were not significant predictors. No consistently increased risks were detected for women reporting specific hygiene or douching habits, except the practice of washing the genitalia infrequently during menstruation. These results provide support for a period of increased susceptibility to carcinogens during adolescence, and suggest that this may be an important determinant of the high incidence of cervical cancer in Latin America.

Human papillomavirus infection and cervical cancer in Latin America.

To evaluate a possible association between infection with human papillomavirus (HPV) and cervical cancer, we performed a multicenter case-control study in Latin America of 759 cases of invasive cervical cancer and 1467 randomly selected age-matched controls. Demographic, sexual, behavioral, and other clinical data were obtained by interview, and HPV DNA was assayed in cervical-swab specimens with use of filter in situ hybridization. Cervical infection with HPV 16 or 18 or both was strongly associated with cervical cancer. HPV DNA was detected in 62 percent of the cases but only 32 percent of the controls, and the relative risk of cancer increased from 2.1 (95 percent confidence interval, 1.6 to 2.8) to 9.1 (6.1 to 13.6) with hybridization reactions of increasing strength. Although the number of sexual partners, age at first intercourse, number of live births, and Pap-smear history were also significant risk factors, the strong associations between infection with HPV 16 or 18 or both and cervical cancer persisted after we adjusted for these variables. These observations are consistent with the hypothesis that genital infection with HPV 16 or 18 may have a role in the pathogenesis of cervical cancer. Other well-known risk factors were also identified in the study, but they did not affect the association between HPV and cervical cancer.

Epidemiology of genital papillomaviruses and cervical cancer.

Cervical cancer is an extremely common disease. Its natural history has been well described, and individual risk factors have been defined. It is clear from the epidemiologic evidence that cervical cancer has a multifactorial etiology involving infection with sexually transmitted agents such as genital papillomaviruses and cofactors such as pregnancy, smoking, use of hormonal contraceptives, and diet. The evidence implicating papillomavirus as an etiologic agent of cervical cancer has come from a variety of observational laboratory studies. Genital papillomaviruses induce dysplastic lesions. Most invasive cervical cancers contain papillomavirus DNA, as do cell lines derived from cervical cancers. Viral DNA, appears to be integrated into cellular DNA, and integration involves highly conserved, transcriptionally active regions of the viral DNA.

Invasive cervical cancer and smoking in Latin America.

A case-control study of 667 patients with invasive squamous cell carcinoma of the cervix and 1,430 controls from four Latin American countries showed an age-adjusted relative risk (RR) of 1.2 [95% confidence interval (CI) = 1.0-1.4] for women who had ever smoked, with risk rising to 1.7 (95% CI, 0.8-3.6) for women who smoked greater than or equal to 30 cigarettes per day. The associations were practically eliminated after adjustment for the number of sexual partners and alcohol consumption, probably a surrogate for an unidentified life-style risk factor. Some excess risk persisted among women who smoked for extended periods (RR = 1.5 for greater than or equal to 40 yr), as well as those who began smoking at older ages (RR = 1.7 for greater than 30 yr), which suggests a late-stage effect. In addition, among women who tested positive for human papillomavirus (HPV) type 16 or 18 by filter in situ hybridization, there was an increased risk for women who had ever smoked and a dose-response relationship with the number of cigarettes smoked (adjusted RRs compared with HPV-negative nonsmokers = 5.0 for HPV-positive nonsmokers, 5.5 for less than 10 cigarettes/day, and 8.4 for greater than or equal to 10 cigarettes/day). In contrast, HPV-negative women had no increased risk associated with smoking. These results, from a high-incidence area where intensive smoking among women is still relatively rare, suggest that smoking has a limited effect on cervical cancer risk, possibly only among women with specific types of HPV.

A case-control study of tobacco-related cancers in Colombia.

The work reported here examined the effects of smoking cigarettes made predominantly of dark tobacco, alcohol consumption, and coffee drinking upon the risk of developing cancers of the bladder, larynx, lung, and oral cavity/hypopharynx in Medellín, Colombia. For this purpose 439 subjects with newly diagnosed cancers at the indicated sites were selected. Each subject was then matched by age, sex, and socioeconomic status with at least one control. Data from interviews with the selected subjects, upon analysis, showed both the intensity and duration of cigarette smoking to be statistically significant predictors of cancer at all four sites. In addition, heavy alcohol consumption and coffee drinking in excess of seven cups daily were associated with some elevation of cancer risk at most of the sites studied. Multivariate analyses of cigarette smoking, alcohol consumption, and coffee drinking showed that adjustment for coffee and alcohol consumption did not change the observed associations between elevated cancer risks and cigarette smoking. However, adjustment of the coffee and alcohol consumption data for cigarette smoking reduced most of the observed relative risks of coffee and alcohol consumption and eliminated the statistical significance of certain associations.

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.

Case control study of cervical cancer in Herrera Province, Republic of Panama.

A previous survey found the average annual age-adjusted incidence of cervical cancer in Herrera Province, Panama, to be 79/100,000, exceeding any other reported world rate. In an effort to clarify the reasons for this excessive occurrence, a case-control study was conducted among patients diagnosed between 1974-1980. Sixty-six percent of cervical cancer patients from Herrera Province were alive and were contacted by the study team; of these 91% were successfully interviewed and provided serum specimens. The total study encompassed 156/169 surviving patients and 309 age-neighborhood matched controls. Sexual promiscuity was uncommon, but it exerted a major effect, with those reporting 4 or more life-time sex partners being at a 4-fold excess risk compared to those reporting only one partner. First intercourse at a young age was common (21% began sexual activity prior to age 16) but it failed to alter risk once number of partners was taken into account. Oral contraceptive use was associated with a 2-fold excess risk and this was not substantially affected by controlling for sexual parameters. Thirty-three percent of the study subjects had anti-herpes-simplex type-2 antibody as measured by both neutralization and radioimmunoassays. Although results of the neutralization test were not predictive of risk, women with a radioimmunoassay indicative of HSV-2 infection were at a 40% excess risk for cervical cancer after adjustment for sexual characteristics.