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New test could mean cervical cancer screening could stop sooner

Women with negative HPV DNA test may not need ongoing screening

Adrian O'Dowd

Friday, 02 November 2018

Women aged 55 who receive a negative result from a human papillomavirus (HPV) DNA test may not need to undergo continuing cervical screening, suggests a study* published today in The Lancet Oncology journal.

Canadian researchers found that the new HPV DNA test could mean there is little benefit in continued screening of women aged 55 with a negative test as they were predicted to be at low risk of cervical cancer.

The HPV vaccine has great potential to decrease cervical cancer incidence in the long-term, and vaccine programmes have been introduced in many countries, but older women who have not benefited from vaccination still depend on regular screening for cervical cancer prevention.

There is a lack of strong evidence to inform the age at which to stop cervical cancer screening. The recommended age to stop generally varies between age 50–70 years worldwide, but cervical cancer incidence and mortality remain high in older women.

Regular cytology screening (pap or smear test) is still the most commonly used HPV screening method, and can prevent cancers up to age 75 years although the benefits decline with age.

The UK still uses cytology, while in the USA, both cytology and HPV testing are available for screening, and cytology is still used in Canada, but there are pilots for implementation of HPV testing.

Researchers led by Dr Talia Malagón from McGill University in Montreal, Canada, used a mathematical model to estimate the lifetime risk of cervical cancer in older women who had not been vaccinated.

They developed and validated their model using Canadian health data, including cervical cancer incidence rates from Statistics Canada and HPV prevalence from the screening programme in British Columbia (data from 236,564 women).

The researchers predicted lifetime risk of cervical cancer both assuming women perfectly follow screening guidelines (screening every three years), and assuming a more typical adherence to cervical screening (closer to how often women actually screen in real life, which could be longer than every three years).

The model predicted that without screening or vaccination, one in 45 women would be diagnosed with cervical cancer in their lifetime. Perfect adherence to cytology screening every three years between the ages of 25 and 69 reduced the lifetime risk of cervical cancer to one in 532 women.

For unvaccinated women with usual adherence to cytology screening, stopping screening at age 55 years was associated with a lifetime risk of cervical cancer of one in 138, compared to one in 160 when screening was stopped at age 70 years.

Although increasing the age at which women stopped cytology screening from 55 to 75 led to incremental decreases in cancer risk later in life, the findings suggested that a substantial part of the reduction in risk is due to screening before age 55.

However, the remaining lifetime risk after a woman stops screening depended on the type of screening used.

The researchers found that unvaccinated women who stop screening at age 55 with a negative HPV test were predicted to have a remaining lifetime cervical cancer risk of one in 1,940, lower than the remaining lifetime risk for women who test negative on a cytology test at 55 – 1 in 440.

Dr Malagón said: “While cytology screening has reduced the number of women who get cervical cancer, it is far from perfect because it does not always detect the precancerous lesions which develop into cancer.

“We have known for some time that directly screening instead for the HPV types that cause cervical cancer performs just as well if not better than cytology for screening in women below the age of 60.

“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.”

*Malagón, T; Kulasingam, S; Mayrand, M H; Ogilvie, G; Smith, L; Bouchard, C; Gotlieb, W; and Franco, E L. Age at last screening and remaining lifetime risk of cervical cancer in older, unvaccinated, HPV-negative women: a modelling study. DOI:10.1016/S1470-2045(18)30536-9

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