NEW YORK (GenomeWeb) – A new study published online today in Lancet Oncology suggests it may be possible for older women to stop receiving screens for cervical cancer somewhat earlier than is now recommended if they take an HPV DNA test and receive negative results for oncogenic strains of the virus.
"[O]ur 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," first and corresponding author Talia Malagón, a cancer epidemiology researcher at McGill University, said in a statement.
Cervical cancer rates remain high in older women, she and her co-authors explained, and there is debate around the appropriate age for screening to subside, if at all. In some places, cervical cancer screening is not recommended over the age of 50, while in other instances it continues until 70.
The researchers reasoned that risks and benefits of screening may differ with age depending on the screening method used. With that in mind, they set out to estimate screening method-related cervical cancer risk over five years, 10 years, and remaining lifetime years in women from different age groups who had not received HPV vaccination.
"We have long used cytology to detect the precancerous lesions caused by HPV, which can then be treated before they ever progress to cervical cancer," 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."
Using a simulated, age-structured population model representing women between the ages of 10 and 100 years old, they predicted that cytology-based screening every three years from the ages of 25 to 69 could decrease cervical cancer risk to one in 532, compared with a one in 45 risk in never-screened, unvaccinated women.
When the team focused on older women, it estimated that the average 70-year-old woman with an "unknown" screening history had a roughly one in 588 chance of being diagnosed with cervical cancer in her remaining years. That risk dipped to one in 1,206 for 70-year-old women with negative cytological screening for pre-cancerous cervical intraepithelial neoplasia, and declined still further — down to one in 6,525 — after testing negative for DNA from oncogenic forms of HPV.
For a 70-year-old woman with both neoplasia-free cytological screens and negative HPV DNA tests, the researchers put the lifetime risk of cervical cancer at just one in 9,550.
The same model — established with provincial registry and survey data for hundreds of thousands of Canadian women, Statistics Canada information on cancer incidence — indicated that HPV-unvaccinated, hysterectomy-free women had an average, predicted lifetime risk of cervical cancer of one in 138 when screened with standard cytological methods until the age of 55.
But after screening for 14 high-risk HPV types with DNA testing until the age of 55, the researchers reported, the estimated the lifetime risk of cervical cancer declined to one in 1,940, hinting that it might be possible to cease screening far earlier in settings where HPV DNA tests are part of the cervical cancer screening system.
"Our results suggest 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 years can still lead to incremental decreases in cancer later in life," the authors wrote. "However, women who have a negative high-risk HPV test or co-test after the age of 55 years were predicted to be at low risk for cervical cancer for the rest of their lives, with lower risk than women who continued cytology screening with typical adherence."
In a related commentary article in the Lancet Oncology, Local Health Unit of Reggio Emilia (AUSL-IRCCS di Reggio Emilia) epidemiologist Paolo Giorgi Rossi noted that "no data have been previously reported to support the chosen upper age limit to stop HPV-based cervical cancer screening."
He added that "a decision about when to stop cervical cancer screening must be made soon," noting that Malagón and her co-authors "provide us with the data, and surrounding uncertainty, that are useful to guide decision making on the basis of the evidence, resources, and values we have."