Role of p53 and p21/WAF1 detection in patient selection for preoperative radiotherapy in rectal cancer patients

BACKGROUND: Recent studies showed that p53 and p21 may play major roles in determining tumor radiosensitivity through the apoptosis pathway. The aim of this study was to investigate the predicting value of radiosensitivity in human rectal carcinoma. METHODS: p53 and p21/WAF1 expressions in formalin fixed, paraffin-embedded, preradiation biopsy samples from 49 patients with primary rectal carcinoma were analyzed immunohistochemically. p53 and p21 expressions and their relationships with histopathologic changes after radiation and other clinical features were evaluated. RESULTS: Expressions of p53 and p21/WAF1 were 49 and 28.6 percent, respectively. In 36.7 percent of total tumors, significant histopathologic effect can be observed. There was a significant inverse expression of p53 and p21. Most of the p53(+) or p21(–) tumors were radioresistant, and the majority of p53(–) or p21(+) tumors were radiosensitive. Tumors size in the radiosensitive, p53(–), or p21(+) group decreased more significantly than in radioresistant, p53(+), or p21(–) group (P<0.01), and patients with radioresistant, p53(+), or p21(–) tumors had more local recurrence, more distant metastasis, and a shorter five-year survival rate than those with radiosensitive, p53(–), or p21(+) tumors, but without statistic significance. No statistically significant correlation can be observed between other tumor clinical features and radiosensitivity, p53, or p21 expressions. CONCLUSION: Immunohistochemistry detection of p53 and p21 expressions may be useful parameters for more radiosensitive patients selected for preoperative radiotherapy.Supported by a Grant-in-aid for Scientific Research from the Ministry of Education, Science and Culture of Japan.Presented at the meeting of the Asian-Pacific Congress of Gastroenterology, Yokohama, Japan, September 19 to 23, 1996.