Oropharyngeal squamous cell carcinomas caused by human papillomavirus (HPV) is a strong and independent prognostic factor for survival among patients with oropharyngeal cancer, according to research from the Radiation Therapy Oncology Group (RTOG) published on June 7 in the New England Journal of Medicine and presented at the American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago.
K. Kian Ang, MD, PhD, radiation oncologist at the University of Texas MD Anderson Cancer Center in Houston, and colleagues said that while oropharyngeal cancer caused by HPV is associated with favorable survival, the independent prognostic significance of tumor HPV status remains unknown.
The researchers retrospectively analyzed the association between tumor HPV status and survival in patients with stage III or IV oropharyngeal squamous cell carcinoma who were enrolled in a randomized trial comparing accelerated-fractionation radiotherapy with standard-fractionation radiotherapy, combined with cisplatin therapy, in patients with squamous cell carcinoma of the head and neck.
The authors said that proportional hazards models were used to compare the hazard of death among patients with HPV-positive cancer and those with HPV-negative cancer.
According to Ang and colleagues, the three-year overall survival rate was similar in the group receiving accelerated-fractionation therapy (70.3 percent) and the group receiving standard-fractionation radiotherapy (64.3 percent). Also determined to be similar were the rates of high-grade acute and late toxic events.
In addition, the 63.8 percent of patients that had HPV-positive tumors displayed better three-year rates of overall survival, at 82.4 percent, compared to the 57.1 percent in the cohort of patients with HPV-negative tumors. Moreover, when adjusted for age, race, tumor and nodal stage, tobacco exposure and treatment assignment, 58 percent of patients with HPV-positive tumors showed a reduction in risk of death.
These factors may be used to classify patients as having a low, intermediate or high risk of death, explained the authors.
The researchers also noted that other published data indicate tumor HPV status to be a strong and consistent determinant of superior survival, regardless of treatment strategy, including surgery, radiation therapy, concurrent chemoradiation therapy or induction chemotherapy plus concurrent chemoradiation therapy for the five-year survival rates among patients with HPV-positive tumors (75 to 80 percent), compared to patients with HPV-negative tumors (45 to 50 percent).
“On the basis of our data,” concluded Ang and colleagues, “we believe that future clinical trials should be designed specifically for patients with HPV-positive or HPV-negative squamous cell carcinoma of the head and neck or patients who have been stratified according to HPV status.”