SOLID-PHASE EXTRACTION AND HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC DETERMINATION OF TAMOXIFEN AND ITS MAJOR METABOLITES IN BREAST-TUMOR TISSUES

A sensitive (200 ng/g) and selective reversed-phase high-performance l iquid chromatography separation has been developed to determine the le vels of tamoxifen, 4-hydroxytamoxifen (4-OH) and desmethyltamoxifen (D MT) in tumour tissue taken from patients undergoing tamoxifen therapy. A mu Bondapak C-18 10 mu m column (30 cmx3.8 mm I.D.) was used, with a mobile phase of methanol-1% triethylamine at pH 9 (89:11, v/v). Samp le preparation was carried out using a C, (500 mg sorbent, 3 ml reserv oirs) solid-phase extraction method, and extraction efficiencies were followed in individual extracts using a [H-3]TAM radiolabelled spike ( 10 000 dpm), with a range of 60-90%. Accuracy and precision (standard deviation) as determined from tumour spiked with radioinert tamoxifen and its metabolites ranged from 83.4-92.3% (+/-23-33%) at 20 mu g/g; 8 5.2-87.7% (+/-18-23%) at 2 mu g/g; 88-101% (+/-15-50%) at 0.2 mu g/g a nd 63-94% (+/-13-24%) at 0.02 mu g/g. Results from seventy-two patient s show mean values (+/-S.D.) of 174+/-203 ng/g for 4-OH; 783+/-1326 ng /g for DMT and 410+/-458 ng/g for TAM, variations reflecting heterogen eity in levels between patients. This methodology can be routinely app lied to the determination of tamoxifen and its metabolites in tumour t issues from patients undergoing tamoxifen therapy. (C) 1997 Elsevier S cience B.V.