Abstract
Objectives: In the pre-human papillomavirus (HPV) era, unilateral radiation therapy (URT) for tonsil cancer was associated with low contralateral failure rates and had less toxicity than bilateral radiation therapy (BRT). This study explores the validity of URT in HPV-positive tonsil cancers.Methods: Tonsil squamous cell carcinomas (SCC) treated (typically with 70 Gy radiation and Cisplatin-based chemotherapy) between 2001 and 2007 were reviewed. Retrospective p16 immunohistochemistry staining was undertaken. Baseline, treatment, and response data were collected.Results: Of 182 patients, 78% were p16-positive, were younger (predominantly male), mostly former or non-smokers, and had a more advanced nodal stage. With a median follow-up of 68 months, contralateral recurrence (CLR) rates were low (3.5% p16-positive versus 2.5% p16-negative, p=0.63). Overall survival (OS) was 74% for p16-positive versus 54% for p16-negative subjects (p=0.01), but all other outcomes were similar. Analysis amongst only p16-positive subjects revealed URT was delivered to 37%, with CLR rates of 7.5% versus 1.1% for those treated with BRT, p=0.05. Of the four p16-positive subjects treated with URT who developed contralateral recurrences, three were managed with neck dissection (two disease-free and one died of lung metastases) and one received palliative radiation to the neck and distant metastatic site. All disease control and survival outcomes were similar between those treated with URT versus BRT.Conclusion: While CLRs remain rare overall, there appears to be a slightly increased rate among HPV-positive subjects treated with URT. However, overall outcomes do not appear to be impacted, suggesting that URT remains a reasonable approach in HPV-positive subjects.
Highlights
There is known recognition of the role of human papillomavirus (HPV) in the etiology of head and neck cancers, notably those arising from the tonsil, base of tongue or elsewhere in the oropharynx [1]
Our findings confirm the relatively good prognosis associated with p16-positive squamous cell carcinomas of the tonsil compared to malignancies that are p16-negative
The rate of contralateral recurrence following unilateral radiation therapy was low, and there was no difference in the rates of disease control and overall survival when compared to patients who received bilateral treatment
Summary
There is known recognition of the role of human papillomavirus (HPV) in the etiology of head and neck cancers, notably those arising from the tonsil, base of tongue or elsewhere in the oropharynx [1]. Oropharyngeal cancer incidence has increased, in men, over a similar time period [2,3]. Compared with HPV-negative oropharyngeal cancers, HPVpositive patients tend to be younger and use less alcohol and tobacco. HPV-positive cancers tend to present with a small, or occult, primary tumour, but frequently with large nodal involvement [4,5]. As a group, they have a relatively favourable response to therapy with improved locoregional tumour control, improved disease-specific survival, and improved overall survival following radiotherapy (RT) or surgery when compared to HPV-negative cancers [6,7,8,9]
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