Study of p53 oncoprotein expression and S-phase fraction in patients with head and neck cancer: A preliminary study

The purpose of this study was to investigate the role of p53 oncoprotein expression and S-phase fraction in the assessment of response to radiotherapy in head and neck cancer patients. In this prospective study, a total of 43 previously untreated head and neck cancer patients were enrolled. Preoperative and preradiotherapy (PreRT) biopsy was taken and radiotherapy was given. Repeat post-radiotherapy (Post-RT) biopsy was done from the same site to evaluate the response to radiotherapy. PreRT and post-RT documentation of p53 expression and S-phase fraction was evaluated. Out of a total of 43 patients, 58% (25/43) were responders and 42% (18/43) were non-responders to radiotherapy. Pre-RT p53 expression was observed in 60% (26/43) of tumors, while 84% (36/43) patients had pre-RT high (>10%) S-phase fraction tumors. Amongst non-responders, 78% (14/18) had postRT p53 positive expression in comparison to only 20% (5/25) post-RT p53 positive expression in responders (P<0.0001). Mean S-phase fraction was lower in postRT tumors as compared to pre-RT tumors amongst responders (p<0.001). Patients with post-RT p53 positive tumor had worse prognosis than patients with post-RT p53 negative tumors (p<0.05). Non-responders had significantly higher post-RT p53 expression as compared to that of responders (p<0.0001). Similarly, responders had lower post-RT S-phase fraction as compared to postRT S-phase fraction tumors of non-responders (p<0.0001). Patients with pre-RT p53 positive expression and subsequent post-RT p53 negative expression responded to radiotherapy and had better survival than patients with pre-RT p53 negative tumors and subsequent post-RT p53 positive expression (p<0.01). Thus, patients whose tumor expressed p53 and high S-phase fraction had a strong probability not to respond to radiotherapy. The ability to predict the outcome of radiotherapy with these markers would allow early choice of the best treatment modalities in patients with head and neck cancer. [Turk J Cancer 2003;33(2):75-81]