Adjuvant Radiation in the TORS Era – Is There a Benefit to Omitting the Tumor Bed?

Publication date: Available online 9 August 2016
Source:Practical Radiation Oncology
Author(s): Stanislav Lazarev, Blagoja Todorov, James Tam, Vishal Gupta, Brett A. Miles, Nancy Lee, Richard L. Bakst
PurposeTrans-oral robotic surgery (TORS) followed by adjuvant radiotherapy (RT) is becoming popular in treating node-positive tonsillar squamous cell carcinoma (SCC). One potential benefit is eliminating irradiation of the primary site when the tumor is widely resected, and targeting the neck only. This study assessed whether omitting the tumor bed provides any dosimetric or clinical advantage.Methods and MaterialsWe identified 21 patients with primary tonsillar SSC that were treated with TORS followed by RT to the ipsilateral neck and primary site. We subsequently re-planned each case to allow target coverage to the neck only, excluding the tumor bed. For each case, we created 2 plans: neck only (NO) and neck plus primary (N+P). Additionally, we identified patients (n=7) with primary SSC tonsil who did receive neck only irradiation in order to compare their dosimetry and toxicity profile with those treated to both the primary site and ipsilateral neck. Contralateral neck radiation was not administered in any of these cases.ResultsDespite excluding the primary site in the NO plans, the mean dose to the tumor bed was high - 53.9Gy. The only significant differences in omitting the primary site were lower doses to the oral cavity, 29.8Gy in NO plan versus 34.6Gy in N+P plan, p=0.002, and superior constrictors, 42.9Gy in NO plan versus 46.1Gy in N+P plan, p=0.01. No appreciable differences in toxicities were noted in the limited cohort treated with neck only irradiation.ConclusionsSparing the primary site after TORS in node-positive tonsillar SSC does not appear to provide any significant dosimetric or clinical advantage. Furthermore, the tumor bed receives a significant but potentially sub-therapeutic dose, limiting options for irradiation in a salvage setting. At this time, we do not recommend omitting the tumor bed from the radiation target volume following TORS.



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