Rotterdam and Brussels CT-based neck nodal delineation compared with the surgical levels as defined by the American Academy of Otolaryngology-Head and Neck Surgery.

PURPOSE/
OBJECTIVE: Rotterdam and Brussels have independently published guidelines for the definition and delineation of CT-based neck nodal Levels I-VI. This paper first reports on the adequacy of contouring of the Rotterdam delineation protocol. Rotterdam and Brussels differed slightly in translating the original surgical level definitions as proposed by the 2002 American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) to CT guidelines. To adapt to the surgical level definitions to come to a unifying concept, adjustments of both CT-based classifications are proposed. METHODS AND MATERIALS: The clinical neck nodal target volumes of patients irradiated in Rotterdam by three-dimensional conformal radiotherapy (3D-CRT) between December 1998 and March 2001 were reviewed. Thirty-four patients with N0 and 27 patients with N+ disease with primary tumors located in the oral cavity (n = 1) oropharynx (n = 24), hypopharynx (n = 7), and larynx (n = 29) were evaluated. Seven patients underwent unilateral (3 N0 patients, 4 N+ patients) and 54 underwent bilateral (31 N0 patients, 23 N+ patients) irradiation of the neck. In 11 N+ patients, 3D-CRT of the neck was followed by unilateral neck dissection. The dose to the primary and nonresected N+ necks was 70 Gy and to the N0 neck was 46 Gy. Neck levels were analyzed for adequacy of contouring, dose distribution, and patterns of relapse. The mean dose and the percentage of the volume receiving a minimum of 95% (V95) or >107% (V107) of the prescribed dose was computed.
RESULTS: In 4 patients treated with bilateral 3D-CRT, contouring was not in concordance with the guidelines of the protocol. The V95 and V107 in the 81 adequately contoured N0 necks (63 irradiated N0 necks from 33 N0 patients, 18 irradiated N0 necks from 24 N+ patients) was 95.6% and 6.3%, respectively. For the 26 N+ necks (15 N+ necks from 13 N+ RT-only patients, 11 N+ necks from 11 preoperatively irradiated patients), the V95 and V107 was 94.6% and 6.7%, respectively. With a median follow-up of 29 months, in 4 (8.6%) of 46 patients treated by 3D-CRT only, regional relapse was found. An actuarial regional and locoregional relapse-free survival and disease-free survival rate at 3 years of 90%, 78%, and 68%, respectively, was observed. All regional relapses were observed in the N0 necks of patients with supraglottic laryngeal carcinoma. Taking the surgical 2002 AAO-HNS classification as a reference, adjustments are proposed for the Rotterdam and Brussels delineation protocols to arrive at a unified CT-based neck nodal classification.
CONCLUSION: Adequate dose coverage for the Rotterdam CT-based contours of the neck nodal levels was found. In the RT-only patients, only four failures were observed: one regional and three locoregional relapses. As a next step in optimizing the current Rotterdam and Brussels CT-based delineation protocols, adaptations are proposed to resolve the discrepancies compared with the 2002 AAO-HNS surgical classification.