Different risk factors seen for HPV-positive and -negative head and neck cancer

March 11, 2008

NEW YORK (Reuters Health) - Certain sexual behaviors and marijuana use increase the risk of human papillomavirus type-16 (HPV-16)-positive head and neck cancer, whereas tobacco smoking, alcohol use, and poor oral hygiene up the risk of HPV-16-negative disease, US researchers report.

Sexual behaviors associated with HPV-16-positive head and neck cancer included increasing numbers of lifetime oral or vaginal sex partners, casual sex, infrequent use of condoms and other barriers during sex, and a history of sexually transmitted disease. Frequent and long-term use of marijuana also greatly increased the risk.

The link identified between HPV-16-negative disease and tobacco/alcohol use is consistent with prior research that did not classify cases by HPV status, according to the report in the March 19th issue of the Journal of the National Cancer Institute.

Previous research has identified pathologic differences between HPV-positive and HPV-negative head and neck squamous cell carcinomas. In addition, clinically, HPV-positive disease carries a better prognosis than HPV-negative disease, due in part to an improved response to chemoradiotherapy. Whether the risk factors for these two types of disease also differ was unclear.

"This is the first study to compare and contrast the risk factors for HPV-positive and HPV-negative head and neck cancers by separating out the two types of cancers prior to analysis," lead author Dr. Maura L. Gillison told Reuters Health.

"We were surprised to find that the risk factors for the two types of cancers were so distinct from one another," said Dr. Gillison, from The Johns Hopkins Kimmel Comprehensive Cancer Center in Baltimore. "I used to think of head and neck cancers caused by HPV as a subset of 'traditional' head and neck cancers. Now, I realize this is actually a completely different disease."

The findings are based on a comparison of potential risk behaviors in 240 patients with head and neck cancer and in 322 matched control subjects. Ninety-two of the case subjects tested positive for HPV-16.

"Practicing clinicians need to realize that individuals who have never picked up a cigarette or a drink nevertheless may be at high risk for head and neck cancer because of their sexual behavior and possibly from marijuana use," Dr. Gillison said.

She added that her group is now planning a study to confirm the association between HPV-16-positive disease and marijuana use.