INFECTION with human papillomavirus (HPV) is linked to a threefold greater chance of oesophageal cancer, say Australian scientists.
"This doesn’t mean it is present in all (oesophageal cancers), but it may be a factor in a certain proportion of cases," says Dr Surabhi Liyanage, the lead author of a new review of previous research.
HPV is a common sexually transmitted virus that is known to cause cervical cancer (the most common cause of cancer-related death in Southern Africa, according to the World Cancer Research Fund International), anal cancer and some cancers of the reproductive organs and the upper throat.
Dr Liyanage, of the University of New South Wales in Sydney, Australia, says there has been a lot of debate among researchers about the role of HPV in cancer of the oesophagus because most of the studies to date have been small and used disparate methods, making them hard to compare.
Worldwide, oesophageal cancer is the eighth most common cancer and responsible for about 400,000 deaths a year, according to World Health Organisation data.
The World Cancer Research Fund International says incidence rates for oesophageal cancer are highest in South Africa and Eastern Asia (China, Japan and Korea), and lowest in Central America and Western and Middle Africa.
The rate per 100, 000 population is 16 in South Africa, the fund says. This is 16 times the rate in the regions with the lowest incidence.
In the US, nearly 18,000 people — roughly four out of every 100,000 — are diagnosed with oesophageal cancer each year, and 15,000 Americans die from it annually.
To get a better handle on the relationship between HPV and oesophageal cancer, Dr Liyanage and her colleagues gathered results from all of the studies that have compared patients with the cancer to people without it.
The studies focused on oesophageal squamous cell carcinoma, one type of oesophageal cancer that affects the lining of the oesophagus.
In each study, oesophageal tissue samples from cancer patients and from patients without the cancer were examined to see whether HPV was present.
The 21 studies Liyanage’s group analysed included 1,223 people with oesophageal cancer and 1,415 people without cancer.
HPV was found in the oesophageal tissue of 35% of the cancer patients, compared with 27% of the people without oesophageal cancer.
Taken together, the studies link HPV infection of oesophageal tissue to a threefold greater risk of oesophageal cancer, the researchers report in the online journal Public Library of Science (PLOS) ONE.
If the general population’s rate of oesophageal cancer is 4.4 out of every 100,000 people, a threefold risk increase would raise those chances to 13.2 out of every 100,000.
Two vaccines, Cervarix and Gardasil, have been developed to prevent infection with HPV. In South Africa, the vaccines cost between R500 and R750 a dose. Three doses are needed for full coverage.
If HPV indeed causes oesophageal cancer — and that remains to be determined — it’s possible the vaccines could help prevent the cancer, Dr Liyanage says.
"However, this needs to be studied further. The benefits of cancer-preventing vaccines are not seen immediately, but after many years following vaccination," Dr Liyanage says.
South African Health Minister Aaron Motsoaledi recently announced that the government hoped to be able to negotiate lower prices for the vaccine, and intended to start administering cervical cancer vaccines in schools from February 2014.
Some of Dr Liyanage’s co-authors serve on advisory boards for the companies that make these vaccines and have received research funding from them.
US health officials would like 80% of teenage girls to receive the HPV vaccine, but last week they reported that rates of vaccination appeared to be lingering closer to 53%.
Dr Liyanage says there are also other ways to reduce the risk of developing oesophageal cancer, including avoiding smoking and excessive drinking, and controlling weight.
Reuters, with Marika Sboros
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