There are indications that the test sensitivity of the Pap smear changes with age. The incidence of clinical cervical cancer after a negative test result reflects the sensitivity of the test. In this study, we examined the risk of cervical cancer after a negative Pap smear by different age groups.
Screening history data (from the Dutch nationwide registry of histo- and cytopathology (PALGA)) have been linked on an individual level to cervical cancer incidence data from the Netherlands Cancer Registry (NKR). All primary negative screening smears taken from 1996 to 2007 were analyzed, stratified by seven age groups (29-33, 34-38, …, 59-63 years). The follow-up period after a negative smear was 72 months. Cox regression analyses were performed to assess the hazard ratio (HR) for cervical cancer after a negative smear, adjusted for calendar time and screening history.
792 cervical cancers were diagnosed in 17,247,925 women-years after a negative test result. We found that older women have a significantly decreased risk to be diagnosed with cervical cancer after a negative Pap smear compared to younger women. With increasing age, the risk of cervical cancer after a negative smear decreased. Compared to women of 29-33 years, the HR was 0.84 (95% CI: 0.66-1.07) for 34-38 years, 0.65 (95% CI: 0.50-0.84) for 39-43 years, 0.43 (95% CI: 0.32-0.58) for 44-48 years, 0.37 (95% CI: 0.27-0.51) for 49-53 years, 0.42 (95% CI: 0.31-0.58) for 54-58 years, and 0.33 (95% CI: 0.23-0.48) for 59-63 years.
Older women have a significantly lower risk to be diagnosed with cervical cancer after a negative Pap smear compared to younger women. The lower risk might be caused by a higher test sensitivity in older women to detect relevant cervical lesions by cytological screening, or by less rapid development of cancer in older women. Our results indicate that a longer interval at older ages might be more (cost-)efficient to prevent cervical cancer in the population.