Background: Cervical cancer is the third most malignancy among Thai women. Cervical intraepithelial neoplasia(CIN) 2/3 is precancerous of cervical cancer that could be conservatively treated. A precise recurrent investigation tool is an important method.

Objective: The aim of this retrospective study is to investigate the regression and recurrence rate of CIN2/3 after three years of treatment.

Materials and Methods: Ninety cases of CIN2/3 from participants who underwent cervical cancer screening and treated between July 2013 and June 2016 at Gynecologic Clinic, Thammasat University Hospital, Pathumthani, Thailand and affiliated clinics were recruited. Demographic data, method of treatment and co-testing report of participants were recorded for three consecutive years.

Results: A total of 2,144 women during the period were recruited. After those excluded, 1,505 cases were enrolled in this study. Cases who had abnormal cervical cytology had less mean age, more sexual partners and sexual transmitted diseases than those who had normal cervical cytology. Ninety-nine percent of the negative testing group had negative co-testing at the end of the three-year period. Ninety cases were diagnosed with CIN2/3. The regression rates of CIN2/3 at two and three years follow-up after treatment were 97.8% (88/90) and 95.6% (86/90), respectively. An additional four cases that had negative co-testing at first and second year were diagnosed of CIN2/3 at third year of follow-up period.

Conclusion: The regression and recurrence rates of CIN2/3 at three-year follow-ups are 95.6 and 4.4 percent, respectively. Overextending by three consecutives co-testing follow-ups of CIN2/3 after treatment should be of concern.

Keywords: CIN, Pap smear, High grade, Follow-up, Excision procedure, Ablation