Has the use of pap smears reduced the risk of invasive cervical cancer in Guadalajara, Mexico?

In Mexico, cervical cancer is the leading cause of death due to cancer among women 35 years of age and older. Although cytologic screening for cervical cancer was introduced as a national program 24 years ago, the mortality rate for this disease has been increasing. A case-control study was undertaken. Cases were women younger than 70, with newly diagnosed invasive cervical cancer (ICC), who had been residing for at least the past year in the metropolitan area of Guadalajara. They were selected from 5 hospitals belonging to the Mexican National Health System. Controls were women without cervical cancer who were treated in the same health center as the corresponding case. Analysis included 143 cases and 311 controls. Information on risk factors for cervical cancer and prior cervical cytologic screening was obtained through a standardized personal interview. Overall, 54% of the cases reported having had a cervical cytology compared with 82% of controls. When compared with unscreened women, those who had ever had a Pap smear had a significantly lower risk of cervical cancer (OR = 0.3, 95% CI 0.2-0.4), and the protective effect persisted for over 5 years. Utilization of Pap smears in the metropolitan area of Guadalajara exerted a protective effect on ICC. Of the 65 women who reported a negative history of Pap smears, 45 would not have contracted cancer if they had ever had a Pap smear.