title: Technetium-99m-sestamibi parathyroid scintigraphy: effect of P-glycoprotein, histology and tumor size on detectability.
abstract: The purpose of this study was to evaluate the effect of P-glycoprotein (P-gp) levels, predominant histology and tumor size on the detectability of parathyroid adenomas with 99mTc-sestamibi scans. Although previous studies have shown that positivity correlates with tumor size, false-negative studies have been reported with large tumors and true-positives reported with very small tumors. Recent investigations have reported rapid washout of sestamibi in malignant tumors because of high levels of P-gp, similar to that seen with multidrug chemotherapy resistance. Therefore, we postulated that this mechanism might account for false-negative studies in parathyroid tumors. Preliminary reports have suggested that the predominant histological subtype influences positivity on 99mTc-sestamibi parathyroid scans.
  
  
  METHODS
  We studied 25 patients with surgically confirmed parathyroid adenomas with 99mTc-sestamibi parathyroid scans. The results of the imaging study were correlated with tissue P-gp levels, predominant histological subtype and size of the surgically removed glands.
  
  
  RESULTS
  There were 21 true-positive and 4 false-negative results. The size of the adenomas ranged from 0.12 to 8.64 ml. We found no correlation between the results of the dual-phase 99mTc-sestamibi study and either the predominant cell type or the level of P-gp. Positivity did correlate with the size of the adenoma (p=0.73, p < 0.0001). We cannot exclude the possibility that P-gp and cell type may still play a role in individual cases, but we suspect that other yet to be determined factors may influence 99mTc-sestamibi detectability in addition to tumor size.
authors.affiliation: Department of Radiology, Georgetown University Hospital, Washington, DC 20007, USA.
authors.forename: A
authors.initials: A
authors.lastname: Bhatnagar
authors.forename: P R
authors.initials: PR
authors.lastname: Vezza
authors.forename: J A
authors.initials: JA
authors.lastname: Bryan
authors.forename: F B
authors.initials: FB
authors.lastname: Atkins
authors.forename: H A
authors.initials: HA
authors.lastname: Ziessman
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism*; D000236:Adenoma / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology; D000293:Adolescent; D000328:Adult; D000368:Aged; D005188:False Negative Reactions; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010280:Parathyroid Glands / Q000000981:diagnostic imaging / Q000473:pathology; D010282:Parathyroid Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology; D011300:Preoperative Care; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D012189:Retrospective Studies; D017256:Technetium Tc 99m Sestamibi
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D019275:Radiopharmaceuticals; D017256:Technetium Tc 99m Sestamibi