The presence of human papillomavirus (HPV) in tumors is the most important predictor of survival for people diagnosed with oropharyngeal cancer, according to a new study in the New England Journal of Medicine (June 7, 2010) and reported this week at the American Society of Clinical Oncology annual meeting in Chicago.
It is the first study large enough to show that the presence of HPV in tumors accounts for better response to therapy, rather than other favorable factors that may be present, such as young age and small tumors. The second leading predictor of survival is lifetime smoking history, followed by cancer stage, the researchers noted.
The findings suggest that the HPV status of the tumor and the patient's smoking history may be used in the future, in addition to cancer stage, to determine the aggressiveness of a patient's therapy.
"Previous studies indicated a relationship existed between the presence or absence of HPV in oropharyngeal tumors and patient survival, but they couldn't determine if other favorable factors present in these patients were responsible for their better outcome," said study leader Maura Gillison, M.D., Ph.D., a medical oncologist and head and neck cancer specialist at the Ohio State University Comprehensive Cancer Center-Arthur G. James Cancer Hospital and Richard J. Solove Research Institute.
Dr. Gillison and her colleagues analyzed the tumors and outcomes of 323 patients with stage III or IV oropharyngeal cancer who were part of a radiation therapy oncology group clinical trial. Of these patients, 206 had HPV-positive tumors and 117 had HPV-negative tumors.
At three years after treatment, 82% of patients with HPV-positive tumors were still alive, compared with 57% of patients with HPV-negative tumors. Rates of cancer relapse at three years for the groups were 43% and 74%, respectively.
The investigators determined that HPV presence in tumors accounted for most of the difference in therapy response and survival between patients with HPV-positive and HPV-negative tumors, while factors such as younger age, white race, better energy level, absence of anemia, and smaller tumors were responsible for only about 10% of the difference.
Smoking history emerged as the second most important independent predictor of survival and cancer relapse for patients with oropharyngeal cancer. The risk of cancer relapse or death increased by 1% for each additional pack year of tobacco smoking (one pack year being equivalent to smoking one pack a day for a year).
The investigators found that at three years about 93% of patients with HPV-positive tumors who were never smokers or light smokers were alive, compared to about 70% of patients with HPV-positive tumors who were smokers and about 46% of patients with HPV-negative tumors who were smokers.
"The two risk factors that place an individual at risk for oropharyngeal cancer are also the most important factors determining patient survival," Dr. Gillison said. "This is probably because these factors determine the genetic profile of these cancers and how they respond to treatment."
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