Distribution of regional lymph nodes metastasis in 870 cases of nasopharyngeal carcinoma and the suggestions for individualized elective prophylactic neck irradiation with intensity-modulated radiotherapy

Abstract

Purpose: To explore the feasibility of individualized elective prophylactic neck irradiation (iEPNI) for optimizing current approach by investigating metastatic lymph nodes (LNs) distribution in nasopharyngeal carcinoma (NPC).

Materials and methods: Records of 870 NPC patients without distant metastasis in Hunan Cancer Hospital from January 2019 to December 2019 were reviewed. LNs' locations were identified based on the 2013 guidelines. The intra-regional lymphatic drainage (IRLD) areas included Station 1st (level VIIa and II), Station 2nd (level III and Va), and Station 3rd (level IV, Vb, and Vc). Other levels were categorized as extra-regional areas.

Results: Among the 870 patients, 94.5% cases exhibited LNs metastasis, including unilateral metastasis in 198 patients and bilateral metastasis in 624 patients. In the whole cohort, the most common involved IRLD areas were level IIb (87.1%), VIIa (80.0%), IIa (61.8%), Va (30.6%), IV (21.4%), Vb (8.9%), and Vc (1.1%). Besides, rates of LNs metastasis in Station 1st, 2nd, and 3rd were 94.3%, 61.1%, and 22.9%, respectively. Only four patients (4, 0.5%) revealed skipping metastasis among the three stations.

Conclusions: Lymph node metastasis follows an organized pattern from Station 1st to 3rd with scarce skipping metastasis. A potential iEPNI strategy of prophylactic neck irradiation to the ipsilateral latter node-negative station appears promising in NPC patients. Further prospective investigations are warranted to validate the approach.

Keywords: elective prophylactic neck irradiation; intensity-modulated radiotherapy; lymph nodes distribution; nasopharyngeal carcinoma.

FIGURE 1

Distribution of metastatic lymph nodes. Station 1st includes level VIIa and II, Station 2nd includes level III and Va, and Station 3rd includes level IV, Vb, and Vc.

FIGURE 2

Examples and schematic diagram of individualized elective prophylactic neck irradiation. (A) In node‐negative nasopharyngeal carcinoma (NPC), only bilateral Station 1st is required to be prophylactically irradiated. (B) In NPC with unilateral lymph nodes (LNs) metastasis (Station 1st only in this example), prophylactical irradiation to ipsilateral latter node‐negative station (Station 2nd) and contralateral Station 1st is required. (C) In NPC with bilateral LNs metastasis (Station 1st and Station 2nd involved on the right side and only Station 1st involved on the left side), prophylactical irradiation to ipsilateral latter nodenegative station (irradiation to Station 3rd on the right side and Station 2nd on the left side) is required. The red, pink, yellow, orange, and white lines represent the primary gross tumor, the metastatic retropharyngeal LNs, the metastatic neck nodes, the prophylactically irradiated areas, and the boundaries among the three stations, respectively.