Stereotactic radiation therapy for recurrent nasopharyngeal carcinoma

Abstract

: Radiation therapy is the mainstay treatment modality for nasopharyngeal carcinoma. Recurrent disease affects about 10% of patients, and reirradiation is the most common treatment for recurrent nasopharyngeal carcinoma. Serious complications are not uncommon during the second course of radiation therapy because of the full-tolerance radiation dose applied to normal tissue. Catastrophic toxicity may be induced by treatment for recurrent nasopharyngeal tumor. Salvage surgery has a 3-year overall survival of 85.8% with a 5% incidence of late fatal toxicity. However, the surgical approach is still relatively new with limited information and experience regarding its optimal implementation. Another technique used for recurrent nasopharyngeal carcinoma is stereotactic radiation therapy (SRT), which delivers radiation to a specific target with a rapid dose fall-off to adjacent normal tissue that can reduce the risk of complications. Single-shot radiation therapy for nasopharyngeal carcinoma has a local control rate of up to 72% for 2 years, although there is a 10% chance of cranial neuropathy and temporal lobe necrosis. Conventional fractionated SRT has shown a 3-year control rate of 56% with complications of 11% nasopharyngeal necrosis and 8.3% nasal bleeding. Hypofractionation SRT with a large fraction dose has demonstrated a 5-year control rate of 78% with a 12.5% to 16% incidence of fatal complications. Local recurrent nasopharyngeal carcinoma with a limited volume should be treated with SRT. For reirradiation, the dose constraints in organs at risk (OARs) of recurrent nasopharyngeal carcinoma are critical. Despite the lack of data regarding SRT, the radiation doses of OARs in SRT may be converted to a biologically equivalent dose and summed with doses of primary radiation therapy for evaluation. Hypofractionation may have an optimal treatment response rate with acceptable complications. For recurrent nasopharyngeal carcinoma, SRT has shown certain therapeutic advantages, but conventional fractionation radiation therapy may still be the appropriate setting for reirradiation. Patients undergoing SRT should be counseled carefully before initiation of therapy, especially if the targets are close to a critical organ that may cause serious side effects. The treatment decision of recurrent nasopharyngeal carcinoma should be based on the patient’s overall condition and disease status.