A new study published in Cancer Epidemiology, Biomarkers & Prevention, finds that the risk of detecting cervical precancer eight years after a negative HPV screening is similar to the risk three years after a negative Pap smear.
In the last two decades, the U.S. has been shifting from traditional Pap smear tests to HPV-based screenings for cervical cancer. The U.S. Preventive Services Task Force recommends three options for routine cervical cancer screening: cytology (Pap smear) every three years, HPV screening every five years, or co-testing (both HPV and cytology) every five years.
“There is a global shift from Pap smears to HPV-based screening because it’s better at detecting precancerous lesions,” said lead author Anna Gottschlich, PhD, MPH, Assistant Professor at Wayne State School of Medicine and the Barbara Ann Karmanos Cancer Institute, USA.
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“Some worry that longer intervals between HPV screens might increase cancer risk, but our findings show that five-year intervals for HPV screening are even safer than three-year intervals for Pap smears,” said Gottschlich.
Gottschlich and her team wanted to find the best interval between screenings, especially as more countries adopt HPV testing. They studied data from four groups:
- 5,546 women with one negative HPV test
- 6,624 women with two negative HPV tests four years apart
- 782,297 women with one negative Pap smear
- 673,778 women with two negative Pap smears two to three years apart
Data came from the Canadian HPV For Cervical Cancer Prevention (HPV FOCAL) trial and the British Columbia Cervix Screening Program. Participants were 25-65 years old at their first screen.
The study calculated the risk of developing cervical precancer (CIN2 or CIN3) for each group. The risk eight years after a negative HPV test was similar to the risk three years after a negative Pap smear. Specifically, the risk of CIN2+ was:
- 3.2/1,000 after one negative HPV test
- 2.7/1,000 after two negative HPV tests
- 3.3/1,000 after one negative Pap smear
- 2.5/1,000 after two negative Pap smears
HPV screening showed lower or similar risk even after eight years compared to Pap smears after three years. Although the risk was slightly higher after eight years for HPV, it was still low over the 14-year study period.
“HPV screening is better than cytology for early detection and treatment of precancer,” Gottschlich said. “Our study shows that even one negative HPV test results in a very low risk of cervical precancer for many years.”
These results can help update screening guidelines. However, each region needs to consider their own resources and population needs. Gottschlich also mentioned the need to ensure continued patient follow-up, especially with longer intervals between screenings.
Longer intervals could help reallocate resources to reach under-screened populations and ensure that those with abnormal results get the necessary follow-up and treatment.
Future studies will continue to follow these cohorts to refine HPV screening strategies, including the best ages to start and stop screening and how to manage abnormal results.
The study had some limitations, such as differences in dropout and screening rates, but overall, the follow-up was good. Also, two cases of precancer were missed by HPV tests but caught by Pap smears during exit screens, which did not affect the main findings.
Source: American Association for Cancer Research
