Session Item

We aimed to explore a potential individualized elective prophylactic neck irradiation (iEPNI) to optimize the current strategy by investigating the distribution of metastatic lymph nodes (LNs) in nasopharyngeal carcinoma (NPC).

Magnetic resonance imaging (MRI) and clinical data of 870 non-metastatic NPC patients admitted to the Hunan Cancer Hospital between January 2019 and December 2019 were reviewed. All patients were staged using the 8th TNM staging system, and the LN location was assigned based on the 2013 guidelines. According to the distribution patterns of the LNs in NPC, the intra-regional lymphatic drainage levels were categorized into the following three stations: Station 1 of level VIIa and II; Station 2 of level III and Va; and Station 3 of level IV, Vb, and Vc. Other levels were defined as extra-regional areas.

The incidence of LN metastasis was 822/870 (94.5%), including 198 cases of unilateral metastasis and 624 cases of bilateral metastasis. Among the 870 patients, the most frequently involved intra-regional lymphatic drainage was level II (89.3%), followed by level VIIa (80.0%), II (59.5%), Va (30.6%), IV (21.3%), Vb (8.9%), and Vc (1.1%). In the extra-regional areas, the detailed LN distribution was: level Ia (0.2%), level Ib (7.7%), level VI (0.1%), level VIIb (5.6%), level VIII (5.5%), level IX (0.3%), and level X (0.2%). The rate of LN metastasis in Station 1, Station 2, and Station 3 was 820/870 (94.3%), 532/870 (61.1%), and 199/870 (22.9%), respectively. Only four patients were considered to be skipping metastasis among the three stations (4/870, 0.5%). Additionally, in 203 patients with unilateral Station 1 LN metastasis, there were 86 (42.4%) and 37 (18.2%) patients with ipsilateral Station 2 and Station 3 metastasis, respectively, and 3 (1.5%) and 1 (0.5%) patients with contralateral Station 2 and Station 3 LN metastasis, respectively.

LN spread in an organized manner from Station 1 to Station 3 with rare skipping metastasis. A potential iEPNI strategy of prophylactical neck irradiation to the ipsilateral latter node-negative station might be feasible, which is detailed as follows: irradiation to Station 1 in patients with no LN metastasis, irradiation to Station 2 in patients with only Station 1 metastasis, and irradiation to Station 3 in patients with Station 2 metastasis but without Station 3 metastasis. Further prospective investigations are expected to validate the strategy.