Accumulation of p53 is prognostic for aromatase inhibitor resistance in early-stage postmenopausal patients with ER-positive breast cancer

OBJECTIVE: Studies have indicated that p53 protein accumulation exerts an adverse effect on the survival of breast cancer patients; however, the prognostic value of p53 protein accumulation for aromatase inhibitor (AI) resistance in ER-positive breast cancer is uncertain. METHODS: The expression level of p53 protein was detected by immunohistochemistry in primary early-stage ER-positive breast tumor specimens from 293 postmenopausal breast cancer patients who received first-line AI treatment (letrozole, anastrozole, or exemestane) until relapse, and analysis was performed to determine whether expression of p53 protein affected the response to endocrine therapy. RESULTS: Of the 293 invasive ductal carcinomas, 65.4% were positive for p53 protein expression. All patients received AI therapy as first-line treatment until relapse. The 5-year disease-free survival rates in p53-positive and p53-negative patients were 78% and 89%, respectively. Patients with primary breast tumors that had p53 protein accumulation showed significantly more resistance to AI treatment (hazard ratio=1.729, 95% confidence interval=1.038–2.880, P=0.035). CONCLUSION: This study demonstrated that p53 protein accumulation was helpful in choosing patients who may benefit from AI treatment and is a prognostic marker in ER-positive early-stage breast cancer.