The battle against cervical cancer is no small success. Routine screening for cervical cancer, begun over 50 years ago, has helped slash rates of the one-time No. 1 cancer killer of women in the U.S. Two recently developed vaccines can also protect women against HPV, the virus that causes the vast majority of cervical cancer cases.
But, each year, 12,000 new cases of the disease are still diagnosed, and nearly 4,300 women die of the cancer. So, increasingly, researchers are looking for better ways to detect the cancer early — and the latest study shows that women who get HPV testing in addition to standard cervical cancer screens could lower risk of the disease by as much as three fold.
Current guidelines recommend that women over age 30 get a pap smear, which involves scraping and analyzing the cells in the cervix, to check for cervical cancer every year, and if the cells are normal for three years in a row, and if she has no family history of cervical cancer, then she can wait for three years before her next screen. Because HPV is a sexually transmitted virus, and women aged 21 to 30 are more likely to be sexually active, public health experts advise that younger women get pap smears annually. Abnormalities in these cells are a red flag for potential tumors.
Three influential U.S. cancer groups recommend, however, that women over 30 get HPV tests in addition to pap tests, since the HPV tests, available since 2003, have proven to be quite sensitive in detecting the presence of high-risk viruses in the cervix that could go on to become cancerous. But because the test may also pick up many HPV infections that would resolve on their own, without causing cancer, most doctors in the U.S. have continued to rely on the pap test as the more definitive screen for potential cancerous changes.
For its part, the U.S. Preventive Services Task Force (USPSTF), an independent government panel that issues cancer screening guidelines, reviewed the existing evidence on the risks and benefits of HPV testing and decided it was insufficient to recommend routine use of the test in women over 30. For younger women, who are more likely to have HPV infections that clear on their own, the task force recommended against HPV screens.
The lingering question is, how many cancers are pap smears missing, and can HPV test fill the gap without leading to overtreatment? In the latest study, published in the journal Lancet Oncology, researchers studied more than 45,000 women aged 29 to 56 in the Netherlands, randomly assigning them to get either a combination of the pap test and the HPV test, or the pap test alone. Five years after their screening, the women were tested again using both methods.
The study found that the dual screen initially picked up more potentially cancerous lesions — 25% more — than the pap test alone. But five years on, those who had had the dual screen had fewer cancers. What’s more, both groups had roughly the same rate of high-grade precancerous lesions, suggesting that HPV testing wasn’t picking up infections that would have cleared on their own.
Previous studies had looked at cancer rates among women after three years of HPV testing, but this study provides additional data on cancer incidence out to five years. In fact, the results suggest that some women getting both tests might be spared from being tested again for up to five years. If women have a negative HPV test and a normal pap smear, then the likelihood that they will develop cervical cancer is very low, so instead of getting more frequent pap tests in the interim, they may be able to wait five years before getting screened again.
For women who test positive for HPV but still have a normal pap result, however, the options get more complicated. They could be on the road to developing cervical cancer, or they could be among those whose HPV infection simply goes away without causing any tumors. The trial’s lead author Dr. Chris Meijer at the VU University Medical Center in Amsterdam and his colleagues recommend a conservative approach for following these women.
They propose using HPV testing as primary screen for cervical cancer, and then using the pap test as triage to separate out high-risk women who test positive for the virus: so if women test positive for HPV, they should then get a follow-up pap test; if the cervical cells are normal, they should repeat the pap smear in six months. If those results are negative, the woman is likely to have a low risk of developing cervical cancer from HPV, and can go back to getting screened in another five years. But if the second pap shows abnormal cells, then she should be referred for potential treatment.
Cancer experts working on the USPSTF’s updated guidelines are currently reviewing the latest information on HPV and pap screening to come up with more detailed advice for picking up and treating cervical lesions. They will certainly weigh a number of different factors, including the latest data from Meijer and his team’s trial, which suggest that after age 30, it may be beneficial to take advantage of the added information from HPV testing.