Risk factors for cervical cancer by histology.

A case-control study in four Latin American countries enabled assessment of risk factors for different histologic types of invasive cervical cancers, with the main analyses focusing on 667 patients with squamous cell cancers and 43 with adenocarcinomas. The epidemiology of the squamous cell tumors resembled that found in other studies, namely a high risk associated with multiple sexual partners (RR = 1.5 for > or = 2 vs 1), early ages at first intercourse (RR = 2.3 for < 16 vs > or = 20), history of a sexually transmitted disease (RR = 1.8), multiple births (RR = 2.2 for > or = 7 vs 1-3), absence of prior Pap smear screening (RR = 3.0 vs Pap within 24 months), detection of HPV DNA (RR = 3.6), and limited years of schooling (RR = 1.9 for < 4 vs > or = 7). The adenocarcinomas appeared less affected by sexual, reproductive, or socioeconomic factors. There was no relationship with age at first intercourse, history of a sexually transmitted disease or education, and only marginal associations with number of sexual partners or parity. Absence of prior Pap smear screening as well as detection of HPV DNA, however, were associated with relationships equally strong as those for the squamous cell tumors. Oral contraceptive use distinctly affected risk of the adenocarcinomas, increasing risk by approximately two-fold. Analyses of the 18 subjects with adenosquamous cancer suggested some resemblance to the squamous cell tumors, especially with respect to the role of sexual and sociodemographic variables. These findings support the need for detailed studies of etiologic differences between the different histologic types of cervical cancers, with an emphasis on careful pathologic review and precise measurement of HPV.