Human papillomavirus (HPV)-positive head and neck cancer is more sensitive to the initial effects of radiation therapy than HPV-negative head and neck cancer, suggest study findings.
These data indicate that treatment should be individualized for the subgroup of patients with HPV-related oropharyngeal cancer, write the researchers.
The team, led by Allen Chen from the University of California in Sacramento, USA, compared the response rates to irradiation among patients with HPV-positive and negative oropharyngeal cancer.
A total of 10 patients treated for locally advanced HPV-positive squamous cell carcinoma of the oropharynx were included in the study. They were matched to one HPV-negative control by age, gender, performance status, T-category, tumor location, and the use of concurrent chemotherapy.
All patients received intensity-modulated radiotherapy (IMRT) to a dose of 70 Gy in 33 daily fractions for 7 weeks.
As reported in The Laryngoscope, the mean reduction in tumor size between baseline and week 7 was 48% in HPV-negative patients and 58% in HPV-positive patients, with no significant difference between the two groups.
However, the authors note that HPV-positive oropharyngeal cancers exhibited an enhanced response to radiation between day 1 of IMRT and the beginning of week 2, compared with HPV-negative cancers.
Indeed, the rate of tumor regression, as measured by the gross tumor volume, over this time period was 33% for patients with HPV-positive tumors compared with just 10% for their HPV-negative counterparts.
"While limited by its relatively small patient size, these findings are among the first to show an in vivo response difference to radiation therapy among actual head and neck cancer patients stratified by HPV status," write Chen et al.
"The results of the present study add to the growing body of literature, suggesting that HPV-related head and neck cancer have a distinct biology compared to HPV-negative humors arising in the setting of traditional environmental exposures such as tobacco smoking," they conclude.
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