Risk factors for progression of squamous cell cervical carcinoma in-situ to invasive cervical cancer: results of a multinational study.

OBJECTIVE: Human papillomaviruses (HPVs) are probably necessary causes of cervical carcinoma, but few infected women develop invasive cervical cancer, suggesting a role for cofactors. The purpose of this study was to identify cofactors associated with progression of carcinoma in-situ to invasion.
METHODS: Data from in-person interviews of women included in a multinational, hospital-based case-control study of in-situ and invasive squamous cell cervical carcinoma were analyzed. In-situ cases and controls were compared to identify risk factors for carcinoma in-situ, and invasive and in-situ cases were compared to identify risk factors for progression to invasive disease.
RESULTS: Risk of invasion was decreased in women with a history of cytologic screening, and in relation to other variables that likely represent enhanced opportunities for screening or clinical evaluation of symptomatic disease. No other risk or protective factors for progression were convincingly demonstrated. Risk of progression was not associated with multiple incidences of promiscuous sexual behavior, or use of steroid contraceptives, although there was a possible association with high parity.
CONCLUSIONS: Possible cofactors that have been considered in this study alter the carcinogenicity of an HPV infection primarily prior to the development of cervical carcinoma in-situ. Women with a history of this condition need not avoid use of steroid contraceptives.