Technetium-99m sestamibi is a transport substrate recognised by the multidrug-resistant P-glycoprotein (Pgp). To test whether 99mTc-sestamibi efflux is enhanced in breast carcinomas overexpressing Pgp, we determined the efflux rates of 99mTc-sestamibi and Pgp levels in tumours from 30 patients with untreated breast carcinoma. Patients were intravenously injected with 740 MBq of 99mTc-sestamibi and underwent a 15-min dynamic study followed by the acquisition of static planar images at 0.5, 1, 2 and 4 h. Tumour specimens were obtained from each patient 24 h after 99mTc-sestamibi scan and Pgp levels were determined using 125I-MRK16 monoclonal antibody and in vitro quantitative autoradiography. All breast carcinomas showed high uptake of 99mTc-sestamibi and data from region of interest analysis on sequential images were fitted with a monoexponential function. The efflux rates of 99mTc-sestamibi, calculated from decay-corrected time-activity curves, ranged between 0.00121 and 0.01690 min-1 and were directly correlated with Pgp levels measured in the same tumours (r=0.62; P<0.001). Ten out of 30 breast carcinomas (33%) contained 5 times more Pgp than benign breast lesions and showed a mean concentration of 5.73+/- 1.63 pmol/g of tumour (group A). The remaining 20 breast carcinomas had a mean Pgp concentration of 1.29+/-0.64 pmol/g (group B), equivalent to that found in benign breast lesions. 99mTc-sestamibi efflux from tumours of group A was 2.7 times higher than that observed in tumours of group B (0.00686+/-0.00390 min-1 vs 0.00250+/-0.00090 min-1, P<0.001). The in vivo functional test with 99mTc-sestamibi showed a sensitivity and a specificity of 80% and 95%, respectively. In conclusion, the efflux rate of 99mTc-sestamibi may be used for the in vivo identification of the multidrug resistant (MDR1) phenotype in untreated breast cancer patients.

A rapid tumor clearance of 99mTc-sestamibi may predict lack of tumor response to neoadjuvant chemotherapy with drugs affected by the multidrug-resistant phenotype in patients with locally advanced breast carcinoma.

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Sixty-eight patients (45 males, 23 females) were studied in order to assess the usefulness of mucosal tissue concentrations of both carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA19-9) in detecting patients at high risk for gastric cancer. CEA and CA19-9 were assayed on cytosol obtained from multiple endoscopic biopsies of 41 patients with chronic superficial gastritis, 18 with chronic atrophic gastritis, and 9 with gastric cancer. Mucosal tissue concentrations of both CEA and CA19-9 increased from chronic superficial gastritis to chronic atrophic gastritis and to gastric cancer (p = 0.005 and p = 0.002, respectively). Mucosal CEA levels in patients with intestinal metaplasia (IM) were significantly higher than in nonmetaplastic mucosa (p = 0.04). Epithelial dysplasia was associated with higher, though not significant, tissue concentrations of both CEA and CA19-9 when compared with IM. Finally, a correlation between serum levels and tissue concentrations was observed only for CA19-9 (Pearson's correlation coefficient = 0.7). In conclusion, these data indicate that gastric mucosa of patients with chronic atrophic gastritis and intestinal metaplasia express high levels of both CA19-9 and CEA.