Analysis of patients with parotid recurrence after parotid-sparing IMRT for nasopharyngeal carcinoma: case series and review of the literature.

Purpose: Intensity-modulated radiotherapy (IMRT) is the standard treatment approach for nasopharyngeal cancer (NPC). IMRT enables effective sparing of the parotid glands and reduces the risk of xerostomia, a common complication of head and neck irradiation. Nevertheless, it is essential to determine whether the parotid-sparing IMRT (ps-IMRT) technique yields increased intra-/periparotid recurrence rates, which constitutes the main purpose of this study.

Methods: Patients with a diagnosis of NPC that received definitive chemoradiotherapy/radiotherapy (CRT/RT) between 1991 and 2021 were evaluated retrospectively. Patients with intra-/periparotid recurrence were detected and prognostic factors for recurrence were sought.

Results: A total of 746 patients were evaluated. Two-dimensional (2D)-RT was applied to 541, 3D conformal RT (3D-CRT) to 10, and ps-IMRT to 195 patients. After a median 85-month follow-up, one (0.18%) patient who received 2D-RT and four (2%) patients who received ps-IMRT experienced an intra-/periparotid recurrence. The median time to intra-/periparotid recurrence was 11.9 months. All patients had been diagnosed with a metastatic lymph node > 2 cm at level II of the ipsilateral neck. In addition, all recurrences occurred on the same side as the positive neck at the time of diagnosis. The 3‑year overall survival, locoregional recurrence-free survival, and distant metastasis-free survival rates were 80%, 40%, and 60%, respectively.

Conclusion: Intra-/periparotid recurrence is extremely rare in NPC. However, it is still possible to identify and characterize particular risk factors, which include a metastatic lymph node at level II, particularly > 2 cm, and multinodal disease at the time of diagnosis.