Aims and background: The aim of the present study was to determine, retrospectively, whether the immunohistochemical expression of two biologic markers of aggressively, P-glycoprotein (P-gp) and PCNA/cyclin (PCNA), could be related to response to chemotherapy and prognosis in locally advanced breast cancer.
Methods: PC 10 Mab was used to determine the proliferation index (PCNA) and C-219 Mab to determine P-gp in 25 locally advanced breast carcinomas subjected to preoperative chemotherapy with MDR-related drugs.
Results: P-gp and PCNA were expressed in 76% and 100% of the tumors, respectively. No case of high P-gp expression was associated with good chemosensitivity, and all P-gp-negative cases showed the best chemotherapeutic response. P-gp and PCNA were both highly expressed in patients who developed local-regional or distant metastases. No recurrence was associated with a negative or low P-gp score.
Conclusions: Statistical analysis showed that high P-gp expression was related to a poor response to chemotherapy and a short disease-free survival. A high PCNA score was not found to be significant for predicting chemosensitivity or survival.