Nasopharyngeal carcinoma: correlation of histopathology with radiation response

Forty-nine cases of NPC were evaluated histopathologically and the radiation responses of the tumor types were assessed. The overall radiation response were as follows: CR 40.8%, PR 14.3%, NC 42.9%, PD 2.0%. The distribution of tumor types were: Squamous cell carcinoma (WHO type I) 4.08%; Non-keratinizing carcinoma (WHO type II) 4.08%; Undifferentiated carcinoma (WHO type III) 91.84% var. Lympho-epitheliomatous (LE), Anaplastic (A), Spindle cell (SC), Clear cell (CC). 94.38% of the cases were classified as clinical stage II, III and IV (tumor found beyond the nasopharyngeal space). The radiation response rate of the tumor in the lymphnode was reversed to the clinical stage and extent of node involvement, namely the higher stage and node involvement, the less rate of radiation response. Twelve cases received radiation dose of less than 4000 cGy, which comprised 11 NC cases and 1 PD case. Of the 37 cases who got 4000 cGy and over, the response rate was 72.97%. Of these WHO type I was not evaluated because of insufficient radiation dose; WHO type II showed 50% response rate; WHO type III showed 74.29% response rate. Radiation response (as assessed from the cervical lymphnode involvement) of NPC was influenced by tumor burden and histologic type of the tumor, namely the less differentiated tumor responded better than the more differentiated one. No definite conclusion can be drawn yet of the different behaviour (if any) of the variants of undifferentiated carcinoma (WHO type III) toward irradiation.