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.