Clinical significance of P-glycoprotein expression in breast cancer

Objective: to study the clinical signincance of P-glycoprotein (P-gp) in breast cancer. Methods: Expressionof P-gP in 60 cases of breast cancer was examined byimmunohistothemistry P-gp expression and response tochemotherapy were comparatively investigated in 19patients with methetatic breast cancer. Results: The P-gpwas positive in 48.3% of the 60 cases of breast canceL P-gpexpnaion was not related to patients' age, menstruationstatus, number of edlary lymph nodes involved, clinicalstage, histological type, and hormonal receptor status(p>0.05). The frequency of metastasis (62.1%) andmortality (51.7%) were higher in P-gp positive cases than innegative cases (16.1% vs 12.9%, P<0.005). The 5-yearsuedval rate of P-gp positive cases (48.3 % ) was sigamcantlylower than that of negative cases (87.1%) (P<0.05). Inpatients who received adjuvant chemotherapy distantmethetheis occurred more frequently in the P-gp positivecases (94.7%) than in the P-gp negative cases (57.1%)(P=0.0468). More P-gp negative patients (7/9) than positivepatients (1/10) were responsive to chemotherapy (P=0.0055).Conclusion: Immunohistochemical examination of P-gpexpression is useful in predicting response to chemotherapyand prognosis in breast cancer patients. P-gp positivity isassociated with poor prognosis.