Implications of p53 over-expression in the outcome with radiation in head and neck cancers.

BACKGROUND Abnormalities in the p53 tumor suppressor gene and in the expression of its protein are commonly seen in several tumors. The prognostic implication of these p53 abnormalities was studied in 55 patients with advanced head and neck cancers. PURPOSE To identify p53 as a prognostic factor in assessment of response and survival outcome to radiotherapy in head and neck malignancies. MATERIALS AND METHODS This prospective study was carried out from April 1998 to December 1999. Fifty five patients with proven squamous cell carcinoma of the head and neck region were treated by radiotherapy (RT) (n=34) with or without chemotherapy (CT) (n=21). A dose of 70 Gy/35#/7 weeks was given with or without concurrent administration of weekly cisplatin (35 mg/m2). Paraffin sections obtained at the time of diagnosis, were examined immunohistochemically for p53 overexpression with monoclonal antibody DO-7 (DAKO). The scoring of p53 positive cells was carried out by a trained pathologist. Selected areas of p53 positive cells were viewed under high power field for quantitative assessment of the p53 over expression. A minimum of 1000 cells were counted and the labeling index (LI) was calculated in terms of percentage of p53 positive cells over the total number of cells counted. A 10% nuclear reactivity exhibiting chromogen positivity cutoff point was established. OBSERVATIONS The data was analyzed as of January 2006. Median follow-up of all the patients was eight months (1-95 months). The median age of this study group was 58 years and of the 55 patients, 48 were males. Positive expression of p53 gene protein was documented by immunohistochemistry in 24 (44%) patients. Over expression of p53 was not associated with T or N stage, site of disease, radiation response or survival outcomes (P=0.143). Stage was the only independent prognostic variable, both for the response to treatment (radiation) and survival (P=0.01). CONCLUSIONS Over expression of p53 protein, when detected immunohistochemically, does not predict for radiation response in these tumors.