title: 99mTc-MIBI scintigraphy as a functional method for the evaluation of multidrug resistance in breast cancer patients.
abstract: OBJECTIVE
  To evaluate the clinical application of (99m) Tc-methoxyisobutylisonitrile (MIBI) scintigraphy as a functional method for assessment of multidrug resistance (MDR) in breast cancer patients and the correlation of these results with P-glycoprotein (P-gp) overexpression and objective response to chemotherapy.
  
  
  METHODS
  22 women, 35-68 years old with breast cancer, suitable for neoadjuvant chemotherapy were included onto this study. Two or three cycles of neoadjuvant chemotherapy were administered (FEC in 15 and CMF in 7 patients). Planar and SPECT (99m) Tc-MIBI scintigraphy was carried out before and after neoadjuvant chemotherapy. Focal (99m) Tc-MIBI uptake in breast cancer lesions was used as a scintigraphic criterion of abnormality. Tumor/background uptake (T/B Index) was calculated. Immunohistochemistry was carried out after surgery for P-gp detection in all cases. The degree of expression was evaluated according to semiquantitative score analysis from 0 to 4.
  
  
  RESULTS
  Planar imaging was true positive in 20 patients, false positive in 1 (with breast cancer and mastopathy), and false negative in 1 (with wide tumor necrosis and deep location in the breast). SPECT imaging was true positive in 21 patients and false positive in 1. In 3 patients with multifocal disease additional tumour masses were visualized using SPECT. Sensitivity was 95% (21/22) and 100% (22/22), respectively, for planar and SPECT detection of breast cancer. P-gp expression was positive in 40.8% of the patients and negative in 59.2%. Intense (99m) Tc-MIBI uptake was shown on the planar images in 21 patients independently of the P-gp expression. There was no significant relationship between T/B Index and P-gp detection. Objective response included 2 clinical complete remissions, partial response in 1 patient, minimal response in 12, and no change in 7. Some clinical results corresponded to (99m) Tc-MIBI scintigraphic data: after neoadjuvant chemotherapy T/B Index was reduced > or = 20% in 9 patients with objective response.
  
  
  CONCLUSIONS
  SPECT is an important diagnostic approach for identification of breast cancer with deep location and satellite tumour spots in multifocal disease. T/B Index did not correlate with P-gp overexpression on baseline (99m) Tc-MIBI scan. Objective clinical results after neoadjuvant chemotherapy corresponded to scintigraphic results in 75% of the patients with minimal response.
authors.affiliation: Department of Nuclear Medicine, Sofia Cancer Centre, Sofia, Bulgaria. sergieva_s@yahoo.com
authors.forename: S B
authors.initials: SB
authors.lastname: Sergieva
authors.forename: K V
authors.initials: KV
authors.lastname: Timcheva
authors.forename: N D
authors.initials: ND
authors.lastname: Hadjiolov
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D000328:Adult; D000368:Aged; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000188:drug therapy; D018270:Carcinoma, Ductal, Breast / Q000000981:diagnostic imaging / Q000188:drug therapy; D018275:Carcinoma, Lobular / Q000000981:diagnostic imaging / Q000188:drug therapy; D017024:Chemotherapy, Adjuvant; D003520:Cyclophosphamide / Q000627:therapeutic use; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D015251:Epirubicin / Q000627:therapeutic use; D005260:Female; D005472:Fluorouracil / Q000627:therapeutic use; D006801:Humans; D008727:Methotrexate / Q000627:therapeutic use; D008875:Middle Aged; D020360:Neoadjuvant Therapy; D009361:Neoplasm Invasiveness / Q000000981:diagnostic imaging / Q000473:pathology; D010641:Phenotype; D011859:Radiography; D019275:Radiopharmaceuticals; D017256:Technetium Tc 99m Sestamibi; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D019275:Radiopharmaceuticals; D015251:Epirubicin; D003520:Cyclophosphamide; D017256:Technetium Tc 99m Sestamibi; D005472:Fluorouracil; D008727:Methotrexate