Human papillomaviruses and cervical cancer in Bangkok. II. Risk factors for in situ and invasive squamous cell cervical carcinomas

To identify risk factors for progression of intraepithelial cervical lesion s, 190 women with invasive cervical cancer were compared with 75 women with in situ disease diagnosed in Bangkok, Thailand, between September 1991 and September 1993. Polymerase chain reaction-based assays for type-specific h uman papillomavirus (HPV) DNA in cervical scrapings revealed oncogenic type s in 79% of invasive and 57% of intraepithelial tumors. Types 16 and 18, bu t not types 31/33/35/39, were more common in invasive than intraepithelial tumors, and untyped HPV DNA was found more commonly in the in situ lesions, suggesting that in situ disease is four times more likely to become invasi ve if due to type 16 or 18 than to other causes, and that tumors with only untyped HPV are not at increased risk of progression. After controlling for HPV type, the risk of developing invasive diseases, compared with the risk of developing intraepithelial lesions, was not related to any of a large n umber of sexual and hormonal factors considered or to smoking, suggesting t hat any cofactors these variables represent act before the development of i n situ carcinoma. Two indices of socioeconomic status were associated with a reduced risk of only invasive disease, suggesting the existence of unknow n protective factors that operate after intraepithelial lesions develop.