The effect of fibrosis in the upper neck on radiation-related cranial nerve palsy in patients with nasopharyngeal carcinoma

Objective: To analyse the effect of fibrosis in the upper neck on the development of radiation-induced cranial nerve palsy (CNP) in nasopharyngeal carcinoma (NPC) patients after radiation treatment. Methods: Between Feb. 2000 and Feb. 2002, 317 consecutive patients with NPC who survival at least 5 years came to our radiotherapy center for follow-up, who were analyzed in this study. Patients who received re-irradiation were excluded. All patients received definitive external beam radiotherapy (EBRT) with either Cobalt-60 or megavoltage linear accelerators. The median radiotherapy dose was 71 Gy (range 55-86 Gy) to the primary disease, 61 Gy (range 34-72 Gy) to the upper neck. High-dose-rate brachytherapy with Ir-192 source was used in 24 patients either as part of definitive treatment or as a boost for residual disease in the nasopharynx. Forty-five patients also received chemotherapy with various regimens. Results: The median follow-up was 11.4 years (range 5.1-38.0 years). A total of 81 patients (25.5%) developed radiation-induced posterior CN group (CN IX-XII) palsy with an average annual rate of 1.8%. The cumulative incidence of CNP was 5.7%, 17.4% and 37.3% at 5-, 10- and 20-year respectively. Fifty-four (17%) patients showed severe fibrosis (G3-4) in the upper neck. Univariate and multivariate analysis showed that the total dose of radiation to the nasopharynx and upper neck fibrosis were independent risk factors for developing CNP after RT for NPC. Neck severe fibrosis was associated with approximately two-fold risk of developing CNP (RR=1.936, 95% CI: 1.521-2.466, P<0.001). Radiation technique with pre-anric field and a total dose of >70 Gy to the nasopharynx were associated with increased risk of developing CNP. Other factors, including gender, age, N classifications, chemotherapy, unconventional fractionation radiation, total radiation dose to the upper neck, and brachytherapy did not influence the risk of CNP. Conclusions: Patients who had severe fibrosis in the upper neck may be at increased risk of radiation-induced posterior group CNP. Perhaps the fibrosis of the surrounding tissues led to damaging to the CN nerve. It should be prudent when pre-anric radiation field were used. (authors)