Researchers in Canada have shown for the first time that the incidence of HPV-related oropharyngeal cancers is increasing among the Canadian population, according to data published recently in Current Oncology. The results of the study indicated that more than half of oropharyngeal cancers are now HPV-positive compared with only about 25% in the mid-1990s.
Anthony C. Nichols, MD, of London Health Science Center, London, Ontario, and colleagues are not the first researchers to show an increased incidence of HPV-related cancers. Maura L. Gillison, MD, of the Ohio State University, and colleagues published data in late 2011 showing that the incidence of HPV-related oropharyngeal cancers had increased 225% in the United States from 1988 to 2004.
According to Nichols, researchers attribute this increased incidence to changes in sexual practices, specifically, an increase in oral sex. HPV infection is often acquired during the more sexually active years of people’s lives, in their late teens and early twenties.
“However, HPV seems to stay latent for long period of time in the tonsils and back of the tongue,” Nichols said. “People are showing up with these cancers in their mid-50s.”
Nichols and colleagues wanted to demonstrate an increased incidence of HPV-related oropharyngeal cancers in Canada.
“The reason that this is important is because in the province where I live, the vaccine is approved for boys and girls, but only funded through social healthcare for girls,” said Nichols, adding that this is because the proof that the vaccine prevents cervical cancer is strong. “Because the lag time from infection to head and neck cancer is so long – it can be up to 30 years -- doing a study will take decades before we know 100% that the [HPV] vaccine prevents head and neck cancer, but there is already emerging evidence that it likely does.”
To conduct the study, the researchers collected data from the London Health Sciences Centre pathology database of all tonsillar cancers between 1993 and 2011. All samples were then tested for the most commonly occurring strains of HPV, HPV-16, and HPV-18.
Of the 160 samples included in the analysis, 57% were found to be positive for HPV 16. No samples were positive for HPV-18.
The cancer cases were then divided by time intervals, showing a significant increase in the number of cases with passing time. From 1993–1999 there were 32 cases of HPV-related tonsillar cancer compared with 68 cases in 2006–2011. That is an increase from 25% of tonsillar cases related to HPV in 1993–1999 to 62% in 2006–2011 (P < .002).
“In the past, most patients who got head and neck cancer were heavy smokers or heavy drinkers, and they had a rate of survival of about half, whereas, about 90% of HPV-positive patients are cured,” Nichols said.
Indeed, the researchers saw an increase in 5-year overall survival from 39% in 1993–1999 to 84% in 2006–2011 (P < .001).
Although this increase in survival is positive, Nichols said that oncologists will have to begin to provide resources to treat these patients over the next few decades if numbers continue to increase.
“Cancer care is extremely costly and resource intensive,” he said. “We will likely need more surgeons and more radiation therapists.”
In addition, although the cure rate in HPV-positive patients is high, many of these patients will have lifelong side effects from treatment for oropharyngeal cancers, such as chronic dry mouth, chronic pain, or disfigurement.
“A young healthy person diagnosed at age 50 will be cured, but will need to live with the side effects for four decades,” Nichols said. “That is going to be a big issue for patients and for the health care system.”