Nuclear DNA content, an adjunct to p53 and Ki-67 as a marker of resistanceto radiation therapy in oral cavity and pharyngeal squamous cell carcinoma

Factors of prognosis and radioresistance in oral cavity and pharyngeal squa mous cell carcinoma (OCPSCC) are limited. In the present study, the usefuln ess of tumor DNA content in predicting radioresistance in patients with OCP SCC has been investigated. Radioresistance has been defined as local recurr ence or tumor persistence after radiation therapy. DNA-ploidy analysis was performed by static cytometry on smears of cell suspensions obtained from f ormalin-fixed paraffin-embedded material and stained with Feulgen. DNA-ploi dy was correlated with the proliferation rate (Ki-67) and p53 protein accum ulation obtained by immunohistochemistry. The follow-up of patients ranged from 8 to 62 months. Radioresistance was more common in non-diploid tumors; 14/28 (50%) non-diploid tumors recurred, whereas only 3 (10.7%) out of 28 diploid tumors had local failure (P = 0.0019). Proliferation rate and p53 a ccumulation, evaluated by immunohistochemistry, also added prognostic infor mation. Twelve out of 14 failures were from non-diploid tumors with a low p roliferation rate (Ki-67<20%), whereas none of 20 p53-negative diploid tumo rs developed recurrences. This study showed that non-diploid tumors respond ed poorly to radiotherapy. DNA content appeared, therefore, as a significan t prognostic marker for the evaluation of OCPSCC in patients receiving radi ation therapy This study also showed that DNA content adds information to p 53 accumulation and the proliferation rate (Ki-67) for the purposes of dete rmining patient management.