[Clinical observation of hypoxic radiotherapy for nasopharyngeal carcinoma]

The clinical application of hypoxic radiotherapy (RT) was developed at a high speed in China in recent years. The protective effect of hypoxic RT on normal tissues has been proved. However, there was not an affirmative answer whether hypoxic RT had any protective effect on tumor. This study was designed to analyze this question by comparing clinical results of hypoxic RT with regular RT in nasopharyngeal carcinoma (NPC) patients.

A series of 117 patients with NPC who underwent hypoxic RT or regular RT between March 1992 and June 2000 in PLA 309 Hospital was enrolled. The cancers were staged as I, II, III, and IV in 11, 30, 57, and 19 cases, respectively. Of these, 69 received hypoxic RT, and 48 received regular RT. There was no significant difference in age, sex, TNM staging, pathological type, adjuvant therapy between two groups (P>0.05). All patients underwent 6MV X-ray and 8-12 MeV electronic beam. The nasopharyngeal areas received dose of 72 Gy (range, 68 to 82 Gy), and neck positive lymph node regions received dose of 64 Gy (range, 60 to 70 Gy).

The incidence rates of 2-3 degree early irradiation toxicity of oropharynx mucous membrane, salivary gland, and II- III degree late dry mouth were 23.2%, 26.1%, 37.7% in hypoxic RT group and 77.1%, 62.5%, 91.7% in regular RT group, respectively(P 0.05). The 1-, 3-, 5-, 7-year survival rates were 97.1%, 83.7%, 74.4%, 54.5% in hypoxic RT group and 97.9%, 86.8%, 70.2%, 54.7% in regular RT group, respectively (P>0.05).

Hypoxia could alleviate irradiation toxicity and reduce complication rate of NPC patients. There is no significant difference between hypoxic RT and regular RT in tumor recurrence and metastasis and the survival rate of NPC. Further study is needed.