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Viral screening test effective against cervical cancer

Every year, some half a million women develop cervical cancer and a quarter of a million of them die of the disease across the world. One in five of those women live in India and three out of five in other developing countries. In these countries, it is the most common form of cancer afflicting women.

Now a paper published in the New England Journal of Medicine has shown that even if women are screened just once in their lifetime, it can substantially reduce their risk of later developing cervical cancer. The large-scale trial, which was carried out in rural Maharashtra, has demonstrated the efficacy of a test that looks for the presence of high-risk types of human papillomavirus (HPV) in cervical cells. Persistent infection with such types of the sexually-transmitted virus is the primary cause of cervical cancer.

Just a single round of HPV testing produced "a significant reduction in the numbers of advanced cervical cancers and deaths from cervical cancer," say Rengaswamy Sankaranarayanan of the International Agency for Research on Cancer at Lyon in France and colleagues from the Nargis Dutt Memorial Cancer Hospital at Barshi in Maharashtra and the Tata Memorial Centre in Mumbai in their paper.

Hitherto, the standard procedure adopted in rich countries is for women to undergo what is known as the “Pap smear” every few years. The Pap smear checks cells scraped from the cervix for abnormalities. If precancerous lesions are found, they can be easily treated. Such preventive screening and early treatment has dramatically reduced the levels of cervical cancer in the developed world.

“However, Pap smear screening has not been uniformly successful in preventing cervical cancer deaths in many parts of the world, particularly in low- and medium-resource countries, due to several challenges in providing good quality testing and following up women testing positive”, according to Christopher Wild, director of the World Health Organisation’s International Agency for Research on Cancer.

Besides, regular Pap smears and related interventions don’t come cheap. The U.S. alone is estimated to spend about $6 billion a year on these procedures.

To examine how effective HPV testing would be, Dr. Sankaranarayanan and his colleagues studied over 130,000 healthy, married women in 497 villages in Osmanabad district of Maharashtra.

The women were between the ages of 30 and 59 years. This age group was selected because cervical cancer was uncommon below the age of 30, explained Dr. Sankaranarayanan in an email. Screening was likely to detect more pre-cancerous lesions and early cancers among women in the 30-59 age group. Moreover, HPV infections in such women were likely to be persistent.

The women were randomly assigned to four groups. One group received a single round of screening with HPV testing. Another group got a Pap smear. A third group was screened with visual inspection after the cervix had been daubed with vinegar, a technique that has been shown to aid detection of precancerous changes. The last group of women was given advice on cervical cancer and how to seek screening at local hospitals. Women who tested positive in any of the three screening tests were further investigated and appropriate treatment was provided where needed.

Over the next few years it was found that the rates of advanced cervical cancer and death among those who received HPV testing were half that in the unscreened group of women. The HPV-tested group also fared far better on both counts than those who underwent Pap smears and visual screening with vinegar.

The efficacy of HPV screening may lie in its ability to better detect precancerous lesions that have a high potential of turning into cancer, according to Dr. Sankaranarayanan.

The HPV testing had another advantage as well. “We found that HPV testing was the most objective and reproducible of all cervical screening tests and was less demanding in terms of training and quality assurance,” noted Dr. Sankaranarayanan and his colleagues in their paper.

“One of the reasons that I find the HPV test to be the most promising is that it can be used on swabs that women collect themselves,” pointed out Patti Gravitt, a researcher at the Johns Hopkins Bloomberg School of Public Health in the U.S., who has studied HPV and cervical cancer in India and other developing countries. But “promising technologies will make an impact only if high coverage of screening and provision of effective treatment is reached,” she emphasized

“I think the ability for HPV testing to be almost as good, if not as good, using a self-collected swab compared to a physician-collected swab offers better opportunities for broad coverage, said Dr. Gravitt. “To be effective at a population level and actually show a dramatic reduction in cervical cancer mortality in countries, many, many women need to be screened.”

‘Hybrid Capture 2,’ the HPV test used in the Maharashtra trials, costs $20 to $30 (about Rs. 1,000 to Rs. 1,500) a test. But a new test, careHPV, is already in field trials. Trials in China, the results of which were published last year in the Lancet Oncology, showed that careHPV was quicker to perform and just as accurate.

When it becomes commercially available, the careHPV test is expected to be much cheaper than the Hybrid Capture 2 test, said Dr. Sankaranarayanan. With increasing demand, the cost could further go down.

“We have shown that a single round of screening in women between the ages of 30 and 59 really helps to reduce cervical cancer incidence and deaths fairly quickly,” observed Dr. Sankaranarayanan. The way to test and treat women with safe methods has been demonstrated. “We would like to see countries adopting large-scale programmes so that cervical cancers are detected very early” and women don’t suffer, he added.

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