HPV POSITIVE OROPHARYNGEAL CANCER IS DISTINCT DISEASE ENTITY

May 19, 2009 —Oropharyngeal cancer is a distinct disease entity when it is positive for human papillomavirus (HPV), with a better prognosis than oropharyngeal cancer that is HPV negative. Although these findings have been suggested in smaller trials, evidence now comes from the largest and most definitive study of the subject to date, in which patients were randomized according to HPV status.

The results were previewed in a presscast on May 14 and will be presented at the upcoming 2009 Annual Meeting of the American Society of Clinical Oncologists.

"HPV status may have important prognostic implications," said lead author Maura Gillison, MD, PhD, professor of medicine, epidemiology and otolaryngology at the Ohio State University in Columbus.

Tumor HPV status should now be part of the routine assessment of oropharyngeal cancer patients, she added.

Investigators are already using this information in designing clinical trials and are stratifying patients by HPV status, Dr. Gillison said. In the future, this might also guide treatment decisions, she noted, because it appears that patients with HPV-positive status have better outcomes with whatever therapy they receive. The National Cancer Institute is requesting proposals for trials to address this issue, she added.

Marked Association With Overall Survival

The latest findings come from a phase 3 trial conducted by the Radiation Therapy Oncology Group involving 206 patients with oropharyngeal cancer containing HPV (mostly HPV subtype 16), and 117 patients with cancers that were HPV negative. All patients received a combination of radiotherapy (either standard or accelerated fractionation radiotherapy) and chemotherapy with high-dose cisplatin.

HPV-positive status was "markedly associated with overall survival," Dr. Gillison reported.

At 2 years, 88% of patients who were HPV positive were alive, compared with only 66% of those who were HPV negative (P < .001). The difference increased over time; at 5 years, the difference in survival had increased to 29%, she said.

"Patients with HPV-positive status had less than half the risk of dying from their cancer at 5 years than HPV-negative patients, even after considering the effects of 6 other important factors, including treatment assignment," she said. Similarly, patients who were HPV positive had about half the risk for tumor progression or death. Further analysis showed that this was due in part to lower recurrence rates in the radiation field, she added.

After 5 years, the incidence of second primary cancers among the HPV-positive patients was less than half that of HPV-negative patients (9.0% vs 18.5%, respectively), she noted.

"Our findings showed that HPV status is as strong and independent a predictor of outcome as cancer stage for patients with oropharyngeal cancers, even after considering other factors, such as age and smoking history," Dr. Gillison explained in a statement. "We're still not exactly sure why this is, but these data provide further evidence that HPV-positive oropharyngeal cancer is a distinct disease entity."

2009 Annual Meeting of the American Society of Clinical Oncologists (ASCO): Abstract 6003. To be presented May 30, 2009