Sexual link to throat cancer
RATES of throat cancer have increased sharply in New Zealand since the 1980s and part of the rise may result from a widespread sexually transmitted infection.
Smoking and heavy drinking are the more well established risk factors for throat cancer - and for cancer of the mouth, whose rates have not changed significantly.
Although it is still an uncommon disease, the rate of throat cancer - which affects the upper throat, back of the mouth and lower tongue - has increased most among men, doubling between 1995 and 2010, following a decade in which the rate was static or declined slightly.
Survival rates for throat or mouth cancers are reported internationally at between 40 and 65 per cent at five years after diagnosis, and higher if the disease is detected early.
Several overseas studies which have also found a rise in throat cancer rates have attributed this mainly or entirely to an increase in cancers associated with human papilloma virus (HPV), say the authors of the new research, Dr Carol Chelimo and Professor Mark Elwood, of Auckland University.
Most people who are sexually active acquire one or more strains of HPV at some point in their lives. Most clear the virus from their systems and in many cases it is without symptoms but in some cases it can persist.
A vaccine is available to protect against two strains of HPV that cause most cases of genital warts and two that are found in the majority of cervical cancers and in many cancers of the anus and genitals - and the tongue and throat.
The actor Michael Douglas said in 2013 that following chemotherapy and radiation he had remained clear of what he had earlier identified as throat cancer linked to oral sex, although he later stated it was actually cancer of the tongue.
The Auckland University researchers, writing in today's Australian and New Zealand Journal of Public Health, say the development of throat or "oro-pharyngeal" cancer from HPV is poorly understood.
"Sexual activity and oral sexual behaviours have been linked to the prevalence of oral HPV infections. It is not clear whether associations with HPV can explain all the increase and particularly the greater increase in males."
"It is hypothesised that the rise in oral HPV infection is due to oro-genital sex and co-habiting with multiple partners, especially when this begins at a younger age, as well as oral-oral contact."
They call for future research on rates of oral HPV infection in New Zealand.
• An uncommon illness
• Also called oro-pharyngeal cancer
• 1389 cases in New Zealand from 1981 to 2010
• Per capita rates rose for men from 1.28 to 3.01 per 100,000 from 1981-86 to 2006-10 - a 135% increase
• Women's rates rose from 0.34 to 0.65 per 100,000 - a 90% increase