Neck cancers are less likely to be fatal if caused by HPV, studies find
Cancers of the neck and throat are much less likely to be fatal if they are caused by the human papilloma virus (HPV) rather than alcohol and smoking, researchers reported Monday. But if the tumor is caused by HPV and the patient also smokes, survival is significantly impaired, they found.
The study provides another good argument for vaccination of both men and women with the HPV vaccine, which has previously been targeted primarily at women because the virus causes cervical cancer, researchers from the National Institutes of Health and Harvard Medical School wrote in an editorial accompanying the report in the New England Journal of Medicine. About 90% of HPV-positive cases of the cancers, known as oropharyngeal cancer, contain HPV type 16 and 5% contain HPV type 18, two of the strains of the virus that are targeted by the two commercial vaccines against HPV. It hasn't been proved that vaccination will prevent the tumors, the editorialists wrote, but it seems likely.
A decade or two ago, alcohol and tobacco were the most common causes of oropharyngeal tumors, but changes in sexual mores and the spread of HPV have been tilting the equilibrium. As of 2003, about 5,800 of 12,000 cases of the cancer were caused by HPV. Now, according to Dr. K. Klan Ang of the University of Texas M.D. Anderson Cancer Center, more than 70% of cases are caused by the virus.
Ang, Dr. Maura Gillison of the Ohio State University Comprehensive Cancer Center and their colleagues studied 323 patients with advanced oropharyngeal cancer, all of whom received a combination of radiation and chemotherapy; 206 of the patients were HPV-positive and 117 were HPV-negative.
The team reported in the New England Journal of Medicine and at a Chicago meeting of the American Society of Clinical Oncology that, after three years of follow-up, 82% of the HPV-positive patients were still alive, compared to 57% of those who were HPV-negative. Taking other factors into account, they calculated that those with HPV-positive tumors were 58% less likely to die within the study period.
Smoking was the second most important predictor of death from the cancer. The risk of cancer relapse or dying increased 1% for each pack-year of smoking. For example, a two-pack-a-day smoker who had smoked for 20 years would have a 40% increased risk. After three years, 93% of HPV-positive patients who were non-smokers survived, compared to 70% of those who smoked. Only 46% of patients who were HPV-negative and who smoked survived.
In another report presented Friday at the meeting of the American Society of Clinical Oncology, Dr. Marshall Posner of the Dana-Farber Cancer Institute in Boston and his colleagues reported similar results from a group of 111 patients. Posner speculated that the better survival rate relates to two factors: The virus itself is sensitive to chemotherapy, so tumor cells are more likely to die, and the DNA of HPV-infected cancer cells is less severely damaged than that of cells exposed to cigarette smoke and alcohol. Typically, those whose tumors are caused by the virus are also younger and thus more able to withstand therapy.
Bottom line: Stay away from cigarettes and whiskey and, if your partner is HPV-positive, avoid oral sex.
-- Thomas H. Maugh II