The feasibility of contralateral lower neck sparing intensity modulation radiated therapy for nasopharyngeal carcinoma patients with unilateral cervical lymph node involvement

To investigate the feasibility of contralateral lower neck sparing intensity modulation radiated therapy (IMRT) for nasopharyngeal carcinoma patients (NPC) with unilateral cervical lymph node metastasis. Retrospective review of 546 patients with unilateral cervical lymph node metastasis treated between November 2009 and February 2012 at one institution. All patients were staged using magnetic resonance imaging and received radical IMRT. Patients were classified into two groups: the inferior border of the negative neck irradiation field only covered Levels III to Va in Group 1; the inferior border covered entire neck down to Levels IV to Vb in Group 2. Median follow-up was 49.9 months (range, 1.3–69.2 months). Four-year overall survival (OS:89.3% vs. 88.9%, P = 0.91), disease-free survival (DFS:81.7% vs. 81.0%, P = 0.91), distant metastasis-free survival (DMFS:88.2% vs. 87.9%, P = 0.95), local relapse-free survival (LRFS:96.7% vs. 94.7%, P = 0.70) and nodal relapse-free survival (NRFS: 96.1% vs. 95.9%, P = 0.94) were not significantly different between Group 1 and Group 2. Twenty-two patients developed cervical lymph node relapse; of whom 20/22 (91.0%) developed unilateral relapse within pretreatment positive neck. Only one patient developed out-of-field relapse, though this patient also relapsed within the neck irradiation field (Level II). No clinicopathological feature tested had significant prognostic value for NRFS in multivariate analysis. In the IMRT and MRI era, contralateral lower neck sparing IMRT seems to be feasible for NPC patients with unilateral cervical lymph node metastasis.