Effect of Pap smear screening on cervical cancer stage at diagnosis: results from the Korean National Cancer Screening Program

OBJECTIVE: We aimed to determine the differences in stage at diagnosis of cervical cancer among Korean women according to screening history. METHODS: Using linkage data from the Korean Central Cancer Registry and Korean National Cancer Screening Program (KNCSP), we included 18,388 women older than 30 years who were newly diagnosed with cervical cancer between 2013 and 2014 and examined their screening history. Between individuals, age group and socioeconomic status were matched to control for potential confounders. RESULTS: Significantly more cases of carcinoma in situ (CIS) were diagnosed in the ever-screened (71.77%) group than in the never-screened group (54.78%), while localized, regional, distant, and unknown stage were more frequent in the never-screened group. Women in the ever-screened group were most likely to be diagnosed with CIS than with invasive cervical cancer (adjusted odds ratio [aOR]=2.40; 95% confidence interval [CI]=2.18–2.65). The aOR for being diagnosed with CIS was highest among women who were screened 3 times or more (aOR=5.10; 95% CI=4.03–6.45). The ORs were highest for women screened within 24 months of diagnosis and tended to decrease with an increasing time since last screening (p-trend <0.01). CONCLUSION: The KNCSP for cervical cancer was found to be positively associated with diagnosis of cervical cancers at earlier stages among women aged 30 years or older. The benefit of screening according to time was highest for women screened within 24 months of diagnosis.