Risk factors for cervical cancer in Thailand: a case-control study.

BACKGROUND Human papillomaviruses (HPV) types 16 and 18 are clearly involved in the etiology of cervical cancer, but the evidence for the carcinogenicity of other HPV types is limited. Cofactors involved in the progression from infection with HPV to high-grade precursors and cancer have not been clearly defined by the results of previous studies. METHODS We conducted a hospital-based, case-control study of invasive cervical cancer to investigate risk in relation to HPV infection and its epidemiologic cofactors in Hat-Yai, Thailand. A total of 338 patients with squamous cell carcinoma, 39 patients with adenocarcinoma/adenosquamous carcinoma, and 261 control subjects were included in the study and were interviewed to obtain information with regard to cervical cancer risk factors. HPV DNA presence in cervical exfoliated cells or frozen biopsy specimens was determined by a polymerase chain reaction assay. RESULTS HPV DNA was detected in 95% of patients with squamous cell carcinoma, 90% of those with adenocarcinoma/adenosquamous carcinoma, and 16% of control subjects. For patients with squamous cell carcinoma, the most common types of HPV found were type 16 (60% of the positives), type 18 (18%), type 58 (3%), type 52 (3%), and type 31 (2%). For patients with adenocarcinoma/adenosquamous carcinoma, the most common HPV types found were type 18 (60% of the positives), type 16 (37%), and type 45 (3%). The risk factors that remained associated with risk of both histologic types after adjustment for HPV and their mutual confounding effects were limited education, increasing number of sexual partners, history of venereal diseases, and interval since last Pap smear (i.e., cytologic) test. Among patients with squamous cell carcinoma, some association with smoking was also observed. CONCLUSION New preventive strategies for cervical cancer will require the consideration of multiple HPV types.