Parotid Gland Metastasis of Nasopharyngeal Carcinoma: Case Report and Review of the Literature

Clinical treatment considerations in the intensity-modulated radiotherapy era for parotid lymph node metastasis in patients with nasopharyngeal carcinoma

PURPOSE

No specific irradiation guidelines have been proposed for parotid lymph node (PLN) metastasis in patients with nasopharyngeal carcinoma (NPC). This study aimed to explore the dose prescription and target delineation for PLN metastasis in patients with NPC.

METHODS

With the NPC database from a big-data platform, 10,685 patients with primarily diagnosed, non-distant metastatic, histologically proven NPC and treated with intensity modulated radiotherapy (IMRT) at our center from 2008 to 2019 were reviewed and those with PLN metastasis were enrolled in this study. Dosimetry parameters were collected from the dose-volume histograms (DVH). The primary endpoint was overall survival (OS). Least absolute shrinkage and selection operator regression (LASSO) was operated for variable selection. Multivariate Cox regression analysis was applied to identify the independent prognostic factors.

RESULTS

PLN metastases were identified in 275/10685 (2.5%) patients. Of 367 positive PLN, 199 were in superficial intra-parotid, followed by 70 in deep intra-parotid, 54 in subparotid and 44 in subcutaneous pre-auricular. Better survival outcome was observed in PLN-radical IMRT group, compared with PLN-sparing group. In 190 patients received PLN-radical IMRT, multivariate analysis revealed that D95% of level VIII > 55 Gy was an independent beneficial prognostic factor for overall survival (OS), progression-free survival (PFS), distant metastasis-free survival (DMFS), and parotid relapse-free survival (PRFS).

CONCLUSION

Based on the distribution pattern of PLN metastasis in NPC and the result of dose-finding study, involving the ipsilateral level VIII into low-risk clinical target volume (CTV2) is recommended for NPC with PLN metastasis.

Intraparotid lymph node metastasis from a nasal septal carcinoma: an unusual source of the unknown primary

Metastatic disease to the parotid lymph nodes typically occurs secondary to head and neck and cutaneous squamous cell carcinomas (SCC). Nasal septal SCC is an exceedingly rare primary cancer that rarely spreads to regional lymph nodes. A 39-year-old man presented with left-sided cervical lymphadenopathy and nasal polyposis. Initial assessment suggested that he may have a head and neck SCC of unknown origin with nodal deposits in close proximity to the parotid gland. Cross-sectional imaging did not reveal the primary source. After further review of imaging and examination under anaesthetic, the primary SCC was found on the left nasal septum. The patient ultimately required a type 1 craniofacial resection and adjuvant chemoradiotherapy to treat the disease. Thorough investigation of the 'unknown primary' SCC including cross-sectional imaging and endoscopic examination is essential for the diagnosis of rare and unusual primary SCCs. Nasal septal SCC can be successfully managed with combined modality treatment in the form of surgical resection and chemoradiotherapy.

Nasopharyngeal carcinoma metastatic to the mandible

Nasopharyngeal carcinoma (NPC) is one of the most common malignancies in the head and neck region, especially among those of Chinese origin. NPC has multifactorial aetiologies including genetic susceptibility, consumption of food with high salt content, and the Epstein-Barr virus. The primary tumour usually arises from the lateral walls of the nasopharynx and is characterized by a rich sub-mucosal lymphatic structure, often leading to cervical lymph node metastasis. Distant metastasis has been recognized to be a major cause of treatment failure in patients with nasopharyngeal carcinoma. Bone, liver and lung are the most frequent sites of NPC metastases.