Locoregional extension patterns of nasopharyngeal carcinoma and suggestions for clinical target volume delineation

Abstract

Clinical target volume (CTV) delineation is crucial for tumor control and normal tissue protection. This study aimed to define the locoregional extension patterns of nasopharyngeal carcinoma (NPC) and to improve CTV delineation. Magnetic resonance imaging scans of 2366 newly diagnosed NPC patients were reviewed. According to incidence rates of tumor invasion, the anatomic sites surrounding the nasopharynx were classified into high-risk (>30%), medium-risk (5%–30%), and low-risk (<5%) groups. The lymph node (LN) level was determined according to the Radiation Therapy Oncology Group guidelines, which were further categorized into the upper neck (retropharyngeal region and level II), middle neck (levels III and Va), and lower neck (levels IV and Vb and the supraclavicular fossa). The high-risk anatomic sites were adjacent to the nasopharynx, whereas those at medium- or low-risk were separated from the nasopharynx. If the high-risk anatomic sites were involved, the rates of tumor invasion into the adjacent medium-risk sites increased; if not, the rates were significantly lower (P < 0.01). Among the 1920 (81.1%) patients with positive LN, the incidence rates of LN metastasis in the upper, middle, and lower neck were 99.6%, 30.2%, and 7.2%, respectively, and skip metastasis happened in only 1.2% of patients. In the 929 patients who had unilateral upper neck involvement, the rates of contralateral middle neck and lower neck involvement were 1.8% and 0.4%, respectively. Thus, local disease spreads stepwise from proximal sites to distal sites, and LN metastasis spreads from the upper neck to the lower neck. Individualized CTV delineation for NPC may be feasible.

Comorbidity predicts poor prognosis in nasopharyngeal carcinoma: Development and validation of a predictive score model

“…Details of the radiotherapy techniques applied at Sun Yat-sen University Cancer Center have been reported previously [17][18][19]. Among the 1968 patients, 1238 (62.9%) underwent two-dimensional radiotherapy (2D-CRT) and 730 (37.1%) underwent threedimensional conformal radiotherapy (3-DCRT) or intensity-modulated radiotherapy (IMRT).…”

Comparison of the treatment outcomes of intensity-modulated radiotherapy and two-dimensional conventional radiotherapy in nasopharyngeal carcinoma patients with parapharyngeal space extension

“…The target volumes were delineated using an institutional treatment protocol as previously described [11], in accordance with the International Commission on Radiation Units and Measurements reports 50 and 62. The clinical target volumes (CTVs) were individually delineated on the basis of the tumor invasion pattern [12]. The contoured images were transferred to the Corvus version 3.0 inverse IMRT planning system (Peacock; Nomos Corp., Deer Park, IL, USA).…”

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“…Li et al [14] analyzed 1920 NPC patients with positive LNs. The incidence rates of LN metastasis in the upper (RP and level Ⅱ), middle (levels Ⅲ and Ⅴ a), and lower neck (levels Ⅳ , Ⅴ b, and supraclavicular fossa) were 99.6%, 30.2%, and 7.2%, respectively.…”