Ideal Age of Last Cervical Cancer Screening Depends on Test Type

With the adoption of cotesting—human papillomavirus (HPV) plus Pap cytology—cervical cancer screening methodology has focused primarily on the preferred frequency of combined testing.

However, a new study, published Nov. 1 in The Lancet Oncology, is re-examining the recommended age of last cervical cancer screening. The Canadian study concludes age at last cervical cancer screening depends on the type of test used. With cytology,  lifetime cervical cancer risk reduction might be achieved by screening up to age 75 years, rather than age 65 years as is currently recommended in the United States. However, a single negative exit HPV test at age 55 years provides “strong reassurance” and indicates a very low remaining lifetime risk of cervical cancer.

“The introduction of a test with a higher sensitivity and longer lead time should necessarily drive the establishment of a lower stopping age than for the Pap test,” writes Paolo Giorgi Rossi, Ph.D., from the epidemiology unit at Azienda Unità Sanitaria Localein in Italy, in an accompanying editorial.

Cervical cancer incidence and mortality remain high in older, unvaccinated women and may actually be underestimated because women who have had a total hysterectomy are no longer at risk for cervical cancer, but are generally not from denominators for age-specific cancer incidence. This underestimation of risk may also underestimate the benefits of screening in older women with a cervix.

The Canadian researchers developed a Markov model of cervical cancer screening to estimate the remaining lifetime risk of cervical cancer at different ages and with different exit screening tests. They calibrated and validated the model using Canadian provincial registries and survey data. The model used HPV infection and cancer incidence data from Statistics Canada. The model also reflected typical cervical cancer screening adherence and rate of hysterectomy, with stopping ages varying from age 55 years through age 80 years.

The researchers found that cervical cancer incidence excluding women with hysterectomies underestimated the incidence of cervical cancer in women with a cervix by up to 71 percent in women aged 80–84 years. The model predicted that women without HPV vaccination who were never screened have a 1 in 45 lifetime risk of cervical cancer, whereas unvaccinated women with perfect adherence to cytology screening every 3 years between the ages of 25 years and 69 years could reduce the lifetime risk of cervical cancer to 1 in 532 women.

“Our results suggest that most of the prevention of cervical cancer in later life is due to screening before the age of 55 years, ” write the authors led by Talía Malagón, Ph.D., from McGill University in Canada.

Assuming no differences in screening practice up to stopping age, the researchers found that increasing the age at which women stopped cytology screening from

55 years to 75 years led to incremental decreases in cancer risk later in life. A woman with a cervix who stopped cytology screening at age 55 years will have twice the 5-year risk of cervical cancer at age 70–85 years versus a woman who continued screening with typical screening adherence.

A woman with a cervix who tested HPV DNA negative to 14 high-risk HPV types and stopped screening at age 55 years will have a remaining lifetime cervical cancer risk of 1 in 1,940), which is lower than the remaining lifetime risk for women who stopped screening at the same age with a final negative cytology test (1 in 440) and is also lower than a woman who ends screening with a negative cytology screening at age 70 years (1 in 1,206).

“Our results might not be applicable to future cohorts with high vaccination coverage or who will have been screened for most of their lives with HPV testing,” acknowledge the authors. “However, as it will be many decades before cohorts vaccinated as adolescents reach the age of 50–70 years, our results are likely to be applicable to older cohorts of women for years to come.”

Takeaway: The ideal age to stop cervical cancer screening depends upon test type, with a negative high-risk HPV test at age 55 years yielding a lower lifetime risk of cervical cancer than women who continue cytology through age 70 years.