Clinical characteristics and patterns of failure in the parotid region after intensity-modulated radiotherapy for nasopharyngeal carcinoma

Objective: To discuss the clinical characteristics and patterns of failure in the parotid region after intensity-modulated radiotherapy for nasopharygeal carcinoma.Materials and Methods: We retrospectively reviewed the charts of 716 patients with nasopharygeal carcinoma who underwent intensity-modulated radiotherapy in our centre from January 2005 to December 2010. Disease recurred in a spared parotid gland in 10 patients (1.4%). There were 2 females and 8 males with a median age of 38.5 (34-53) years. The most common presenting symptom was a swelling in pre-auricular region (7/10). Parotid glands were spared bilaterally in these patients. None of these patients had undergone previous radiotherapy or surgical treatment of the head and neck. The location of periparotid failures were transferred to the pretreatment planning computed tomography for dosimetry analysis.Results: The median time from day 1 of radiotherapy to periparoid recurrence was 17.4 (4.4-40.5) months. The median survivial after periparoid recurrence was 25.1 (5.0-74.5) months. There were 9 (90%) patients with lateral retropharyngeal lymphadenopathy. Seven of the periparotid failures were marginal. Of the 7 marginal failures, 6 occurred at the ipslateral parotid of the primary tumor centre. The average mean dose of the ipslateral parotid was 38.1 (32.3-44.1) Gy. Conclusion: Periparotid recurrence is an uncommon pattern of failure after definitive intensity-modulated radiotherapy for nasopharygeal carcinoma. To reduce the risk of periparotid recurrence,one possible strategy is to lessen the dose constraint criteria to ipslateral parotid of the primary tumor centre especially for nasopharygeal carcinoma with lateral retropharyngeal lymphadenopathy.