DNA content in nasopharyngeal carcinoma

DNA analysis by flow cytometry was performed on tissue blocks from 41 patients with nasopharyngeal carcinoma. The histologic slides were reviewed by a pathologist and blindly classified according to the World Health Organization classification. The paraffin-embedded blocks were processed to obtain individual nuclei, which were then stained with propidium iodide. The nuclei were analyzed on a flow cytometer. Excluding 10 uninterpretable histograms, the remainder were interpreted blindly and classified as diploid or aneuploid. The Cox proportional hazards survival model was used to analyze stage, histology, radiation dose, and ploidy. We observed more diploids (23 of 31; 74%) than aneuploids (eight of 31; 26%). The 2-year survival rate of diploids was 55%, compared with 25% of aneuploids (P less than .05). We conclude that ploidy status is an independent prognostic factor in nasopharyngeal carcinoma.