Evaluating the Rationality of the International Guideline's Recommendations Regarding Selective Coverage of Level Ib in Node Clinical Target Volume With Nasopharyngeal Carcinoma: Results From a Real-World Series

Abstract

<h3>Purpose/Objective(s)</h3> Although the International Guideline for the delineation of clinical target volume (CTV) in nasopharyngeal carcinoma (NPC) patients has provided practical reference for the elective coverage of level 1b, there are marked variations in practice among different institutions, and the rationality of the recommendations remained proven. The purpose of this study was to evaluate its rationality in real-world data and provide clinical evidence for the refinement of nodal CTV delineation in nasopharyngeal carcinoma (NPC). <h3>Materials/Methods</h3> Patients with histologically-proven NPC who received definitive Intensity-modulated radiation therapy (IMRT) with or without chemotherapy at Dr. SJ Lin's attending group in our institution between June 2005 and December 2012 were candidates for this retrospectively study. Other main eligible criteria including the following five situations: 1) level Ib metastasis;2)involvement of the submandibular gland;3) involvement of structures that drain to level Ib as the first echelon site (the oral cavity, anterior half of nasal cavity involvement);4) involvement of level II LNs with extracapsular extension (ECE); 5) level II nodal involvement with maximum nodal axial diameter (MAD) greater than 2 cm. Survival outcomes focused on regional recurrence-free survival (RRFS) and incidence rate of Ib recurrence were analyzed. <h3>Results</h3> A total of 451 patients were finally included according to the above criteria. There were 27, 37, 6, 12, 285 and 414 cases be classified as level Ib metastasis, submandibular gland involvement, oral cavity involvement, anterior half of nasal cavity involvement, level II LNs involvement with ECE and level II nodal involvement with MAD greater than 2 cm, respectively. Among these 451 patients, 60 patients received level Ib-covering IMRT due to the first three principles of the International Guideline according to our attending group's protocol. Of note, patients who had Ib involvement would receive ultrasound guided puncture, only those who had positive pathological results would undergo Ib-covering IMRT in our attending group. For the remaining 391 patients who only fulfilled the last two criteria and/or Ib involvement with negative pathological results, they all received level Ib-sparing IMRT, reported 6-year RRFS was 94.3%. For the 22 patients who had regional recurrence at censorship, only 3 (3/391, 0.78%) were recorded as Ib recurrence. <h3>Conclusion</h3> Level Ib-sparing IMRT should be safe and feasible for patients who only had involvement of level II LNs with ECE, and/or had a MAD of greater than 2 cm in level II LNs, and/or Ib involvement with negative pathological results. Further well-designed multi-center prospective trials should be conducted to confirm our results.