IMMUNOHISTOCHEMICAL ANALYSTS OF P-GLYCOPROTEIN EXPRESSION IN BREAST-CANCER - CLINICAL CORRELATIONS

Paraffin-embedded, formalin-fixed tissue (PEFFT) specimens from a subs et of breast cancer patients were analyzed by immunohistochemistry to determine whether or not the presence of P-glycoprotein identified che motherapy resistance. Two antibodies, C219 (monoclonal) and Abl (polyc lonal), demonstrated appropriate immunostaining. Retrospectively and p rospectively, P-glycoprotein expression was determined from PEFFT of 2 0 breast cancer biopsies (19 patients with locally advanced or metasta tic disease). Immunohistochemical staining was graded for number of po sitive cells (N0 to N4) and intensity (I0 to I3). The immunostaining N and I of both antibodies were similar. There was no correlation betwe en N, (P = 0.13) or I, (P = 0.67) and chemotherapy response or between N, (P = 0.63) or I, (P = 0.89) and survival. Five patients had residu al cancer at repeat biopsy after systemic chemotherapy for locally adv anced disease. These specimens had similar hi and I as the primary can cer. This assay accurately identifies P-glycoprotein expression in PEF FT and revealed no correlation between expression and chemotherapy res ponse or survival.