For women older than age 55, a single human papillomavirus (HPV) DNA test that results in a negative diagnosis as well as routine cytology screening are indicative of a low remaining lifetime risk of cervical cancer, according to a study published in the Lancet Oncology.1
Researchers developed a transitional model by using Canadian health data to estimate the lifetime risk of cervical cancer in women who had not been vaccinated for HPV. A new cohort of 236,564 women (reflecting approximately 20% of Canadian women aged 20-24 years in 2012) entered the model every year; successive cohorts entered every 10 years for a final age-structured population model of women aged 10 to 100 years. Cervical cancer status was categorized into 7 stages: uninfected, transient infection, persistent infection, cervical intraepithelial neoplasia (CIN)1, CIN2, CIN3, and cervical cancer. HPV infections were modelled into 4 high-risk groups: HPV16 and HPV18; HPV31, HPV33, HPV45, HPV52, and HPV58; HPV35, HPV39, HPV51, HPV56, HPV59, HPV66, and HPV68; and a generic group of other potentially cancerous HPV infections.
To assess for cervical cancer screening attendance, the researchers calculated a base case scenario using actual screening adherence data reflecting that 53% to 68% of women aged 20 to 69 years were screened at least once in the previous 42 months. The base case was compared to the following scenarios: no screening; perfect screening adherence (100% of women screened once every 3 years from ages 20-69, no screening in other age groups); and typical screening adherence (screening based on age and/or having a negative screen test). Screening consisted of cytology, HPV test, or cytology/HPV co-testing.
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The researchers found the cumulative lifetime risk of cervical cancer for women without history of screening or vaccination to be 1 in 45. A woman with typical cytology screening adherence who stops screening at age 55 are predicted to have a risk of cervical cancer at 1 in 138, and a woman with typical cytology screening adherence who stops screening at age 70 years reduces her lifetime cervical cancer risk to 1 in 160. Perfect adherence to cytology screening from age 25 to 69 is predicted to reduce the risk to 1 in 532 for women without HPV vaccination.
The investigators further predict that women without a previous hysterectomy who test HPV DNA negative and stop screening at age 55 have a remaining lifetime cervical cancer risk of 1 in 1940, which is lower than those of the same age who test cytology negative (1 in 440). A single negative HPV test in patients who had never been screened resulted in a low risk of cervical cancer after 55 years of age (1 in 1096). For those aged 70 years with no exit screen test, remaining lifetime cervical cancer risk was determined to be 1 in 588; those who underwent an exit screen test had a risk of 1 in 1206 after a negative cytology test, 1 in 6525 after a negative HPV test, and 1 in 9550 after a negative co-test for both cytology and HPV.
The researchers conclude that “most of the prevention of cervical cancer in later life is due to screening before the age of 55 years, but continued cytology screening up to around age 75 can still lead to incremental decreases in cancer risk in later life.”
In an accompanying news release,2 lead author Talia Malagón, PhD, states, “Our study does not necessarily suggest that all screening should stop at age 55, since the benefits of continued screening depend on the type of screening used. For countries that still use cytology screening, screening at older ages should further reduce the risk of cervical cancer. However, our results suggest that for countries that use HPV testing as part of their screening, it might be possible to stop screening earlier than we are currently doing, provided women have a negative HPV test.”
References
- Malagón T, Kulasingam S, Mayrand MH, et al. Age at last screening and remaining lifetime risk of cervical cancer in older, unvaccinated, HPV-negative women: a modelling study [published online November 1, 2018]. Lancet Oncol. doi: 10.1016/S1470-2045(18)30587-4
- For new HPV DNA test, study finds there may be little benefit in screening women aged 55 with a negative test [news release]. London, UK: Lancet Oncology. October 31, 2018. Accessed November 1, 2018.
