Causes of cervical cancer in the Philippines: a case-control study.

BACKGROUND Among the numerous human papillomavirus (HPV) types, only types 16 and 18 have been formally classified as human carcinogens. To evaluate the associations of 33 HPV types and other risk factors with squamous cell carcinoma and adenocarcinoma of the cervix, we performed a hospital-based, case-control study in the Philippines. METHODS The study included 356 case subjects who had histologically confirmed cervical cancer (323 incident cases of squamous cell carcinoma and 33 incident cases of adenocarcinoma/adenosquamous carcinoma) and 381 control subjects. Information on risk factors was obtained by personal interview. HPV DNA was detected in exfoliated cervical cells and biopsy specimens by use of a polymerase chain reaction assay. RESULTS HPV DNA was detected in 93.8% of case subjects with squamous cell carcinoma and in 90.9% of case subjects with adenocarcinoma/adenosquamous carcinoma compared with 9.2% of control subjects, giving age-adjusted odds ratios of 156 (95% confidence interval [CI] = 87-280) for squamous cell carcinoma and 111 (95% CI = 31-392) for adenocarcinoma/adenosquamous carcinoma. Fifteen different HPV types were detected in squamous cell carcinoma, and six different HPV types were detected in adenocarcinoma/adenosquamous carcinoma. Among HPV types other than types 16 and 18, the associations of HPV with risk of squamous cell carcinoma were strongest for HPV45. In addition to HPV, high parity, low socioeconomic status, and smoking were also associated with both types of cervical cancer. CONCLUSIONS As has been shown for squamous cell carcinoma, HPV is the central cause of adenocarcinoma/adenosquamous carcinoma of the uterine cervix. The observed associations of less prevalent HPV types with cervical cancer have important implications for cervical cancer prevention strategies.