Ipsilateral Radiation for Squamous Cell Carcinoma of the Tonsil: Summary of Findings and Controversies from the ARS Appropriate Use Criteria Expert Panel on Tonsil Cancer

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Conference Proceeding

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International Journal of Radiation Oncology Biology Physics


Background: In 2012 the American College of Radiology (ACR) published the Appropriateness Criteria for Ipsilateral Radiation for squamous cell carcinoma (SCC) of the tonsil. Since then there have been additional advancements and publications pertinent to this topic.

Objectives: We performed an updated literature review and summarize the findings as well as potential controversies.

Methods: We performed a PubMed search of articles published between January 2000 and June 2019 using various combinations of 25 pre-determined keywords and restricted to articles having the full text available, written in the English language, and on human subjects. Of the 46 citations returned from the search, the authors added 3 citations from bibliographies, websites or books not found in this literature search. Of the 49 citations, 30 citations were retained for further detailed review, and 14 of them were added to the evidence table. Articles were removed from the bibliography if they were not relevant or generalizable to the topic, focused on unknown primary disease, or they were no longer cited in the revised narrative text. Each study was graded using the Oxford Centre for Evidence-Based Medicine 2011 Levels of Evidence Table.

Results: For clinically staged patients undergoing primary (chemo)radiotherapy, we identified 11 new articles published since the initial ACR guideline. Similar to the recommendation in the earlier guideline, unilateral radiotherapy was most often recommended for patients with tumors that were tonsil-confined or either > 1 cm from midline or involving ≤ 1 cm of the mucosa of the base of tongue and/or soft palate. The published experiences demonstrated low rates of contralateral failure in both p16+ and p16- subsets. For patients undergoing primary tumor surgery and being considered for adjuvant radiotherapy, 3 new articles were identified. Multi-disciplinary evaluation is highly recommended before surgery or radiation, since surgical considerations for tonsil cancer may differ from those relevant to ipsilateral RT. The definitions of “well-lateralized” tonsil cancer from a surgical perspective could differ from that of a radiation oncologist. Consequently, whether all surgically resected T1-T2 tonsil SCC with a clinically node-negative contralateral neck are candidates for ipsilateral adjuvant RT warrants further discussion. Collectively among all of the literature reviewed, 1,031 patients were selected for either primary or adjuvant ipsilateral radiotherapy; 26 of 1,031 cases experienced contralateral disease progression. Of these, 19 were reported to have successful salvage and disease control at time of publication. Less than 1% (7 of 1,031) of patients managed unilaterally experienced contralateral progression that was not successfully salvaged. Other factors that might impact the selection for unilateral therapy but remain controversial include: patient age, performance status, number and size of ipsilateral nodes, number of involved ipsilateral nodal stations, clinical/pathological extranodal extension, and p16 status.

Conclusions: This updated literature search provided additional information relevant to selection of patients for ipsilateral tonsil radiotherapy in the primary and adjuvant setting. Areas of controversies identified will require further reconciliation and investigation. Updated voting and committee recommendations will be presented.





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