Multiple sexual partners and early age at first intercourse have been identified as major risk factors for cervical cancer in earlier epidemiologic studies (Brinton, 1992), implying that sexually transmitted agents might be involved in its etiology. Over the last decade, mounting evidence from laboratory (zur Hausen, 1994) and epidemiologic (Muiioz et al., 1992; Peng et aZ., 1991) studies has shown that sexually transmitted infection with genital types of human papillomavirus (HPV) may be the primary causal agent for cervical cancer worldwide (Bosch et al., 1995). However, the relationship between HPV and cervical intraepithelial neoplasia (CIN) is less well established. Among epidemiologic studies investigating this relationship, few (Schiffman et al., 1993;Bosch et al., 1993;Morrison et al., 1991) have been able to use HPV DNA testing methods with high sensitivity and broad type range (Schiffman, 1992a;Burmer et al., 1990). In particular, epidemiologic studies investigating the relationship of HPV with CIN have been quite limited in Asia, even though cervical cancer is the most common cancer among women in this region (Parkin et al., 1992).Cervical cancer is the leading cancer among women in Taiwan (31% of all incident cancers in women) with an annual age-adjusted incidence rate of 33.5 per 100,000 (Cancer Registry Annual Report in Taiwan Area, 1986), which is about 4 times higher than that in the United States (8.7 per 100,000) (Miller et al., 1993). Reasons for the high risk in Taiwan are unclear, since the reported prevalence of known epidemiologic risk factors for cervical cancer, in particular multiple sexual partners, is quite low compared with Western women (Schiffman et al., 1993;Bosch et al., 1993;Morrison et al., 1991;Shen et al., 1993). However, approximately 90% of the women in Taiwan have never had a Papanicolaou (Pap) smear (Health Annual Report in Taiwan Area, 1993), which might be related to the high risk.As reported in Western countries (Bosch et al., 1995), a clinical report from China and Taiwan has shown that HPV could be detected in over 70% of cervical cancer patients (Pa0 et al., 1993), suggesting that HPV may be an important risk factor for cervical cancer in this monogamous female population. To investigate the role of HPV and other possible etiologic factors in the full spectrum of cervical neoplasia in Taiwan, we conducted a case-control study as part of a community-based cervical neoplasia screening study, using a sensitive HPV testing method that detects a broad range of HPV types (Manos et al., 1989).
METHODS
Study population (screened women)In 1991, a community-based cervical neoplasia screening study was conducted among women aged 30-64 in 4 rural townships in Taiwan with high cancer mortality rates. Women who had never been married or who had a history of cervical neoplasia or a hysterectomy were ineligible for the screening. As of June, 1992, 5,286 women had been recruited into the screening study. Briefly, at screening, Pap smears and cervigrams, magnified photographic imag...
