Is prophylactic neck irradiation indicated for patients with cN0 adenoid cystic carcinoma of the paranasal sinuses?

Abstract

To study the prevalence of nodal metastases in sinonasal adenoid cystic carcinoma (SNACC) and to evaluate whether prophylactic neck irradiation (PNI) should be performed in patients with clinical N0 (cN0) disease. Between April 1992 and November 2020, 166 patients with SNACC who had undergone radiotherapy at our department were retrospectively analyzed. The median follow-up time was 71.3 months. Among 166 cases of SNACC, a total of 13 (7.8%) had retropharyngeal or cervical nodal metastasis and 93% (12/13) cases occurred in patients with advanced T stage (T3-T4). Levels VIIa, Ib, and IIa were the most common sites of initial nodal involvement. Only 1.2% (2/166) of patients presented late neck recurrence. Lymph node metastasis independently predicted a poor progression-free survival (PFS) (P = 0.017) but had no impact on overall survival (OS) (P = 0.38). PNI was performed on 36% (55/153) of cN0 patients. The OS (P = 0.42), PFS (P = 0.59), nodal recurrence-free survival (NRFS) (P = 0.46) and distant metastasis-free survival (DMFS) (P = 0.63) rates showed no significant difference between cases with and without PNI. Furthermore, cN0 patients with T4b (P = 0.53; P = 0.61), tumor origin from maxillary sinus (P = 0.55; P = 0.53) or nasopharynx involvement (P = 0.56; P = 0.60) showed no extended OS or PFS associated with PNI. Regardless of the T stage or the site of origin, prophylactic neck irradiation (PNI) for cN0 patients did not provide any benefit on OS and PFS, suggesting that its application on such patients is not warranted unless there is clinical suspicion.