In vivo assay of folate receptors in nonfunctional pituitary adenomas with 99mTc-folate SPECT/CT.
The objective of this study was to evaluate the in vivo assay of folate receptors in nonfunctional pituitary adenomas using preoperative (99m)Tc-folate SPECT/CT and Western blot analysis (WBA) of surgical specimens as the standard.


METHODS
Fifty-six patients (29 men, 27 women; age range, 29-82 y) with clinically nonfunctional pituitary adenomas on MRI underwent preoperative imaging using 666 MBq (18 mCi) of (99m)Tc-folate. SPECT/CT images and whole-body and lateral head planar images were acquired approximately 2 h after injection. Surgical resection took place within a week. WBA on a portion of the excised specimens assessed folate receptor expression in 49 patients. Attenuation-corrected (99m)Tc-folate SPECT/CT images were assessed qualitatively and quantitatively (maximal adenoma counts to background), with WBA as a standard.


RESULTS
Integrated CT was useful for uptake localization and assisted region-of-interest placement. Qualitative interpretation of planar imaging yielded a sensitivity of 81% and specificity of 72%. Qualitative SPECT/CT yielded a sensitivity of 94% and specificity of 61%. Receiver-operating-characteristic curve analysis of quantitative uptake yielded a tumor-to-background cutoff ratio of 3.5, with a sensitivity of 81% and specificity of 83%. Scalp uptake yielded consistent results (over the brain, neck, and choroid plexus) for background when SPECT/CT misalignment artifacts were avoided. Detection of pituitary uptake on anterior-posterior and lateral images was hampered by facial uptake, which varied between patients.


CONCLUSIONS
SPECT/CT of (99m)Tc-folate is an accurate method of assaying folate receptors in vivo and may provide a quantitative marker for identifying folate receptor-positive tumors. This method may also prove beneficial in selecting patients for folate-targeted therapy of clinically nonfunctional pituitary adenomas, for which there is currently no medical therapy.
Department of Radiology, Emory University, Atlanta, Georgia 30322, USA. jgalt@emory.edu
James R
JR
Galt
Raghuveer K
RK
Halkar
Chheng-Orn
CO
Evans
Naema A
NA
Osman
David
D
LaBorde
Timothy H
TH
Fox
Bajat A
BA
Faraj
Kush
K
Kumar
Houping
H
Wang
Nelson M
NM
Oyesiku
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D058973:Folate Receptors, GPI-Anchored / Q000378:metabolism*; D005492:Folic Acid / Q000187:drug effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015609:Organotechnetium Compounds; D010911:Pituitary Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000378:metabolism*; D012372:ROC Curve; D012680:Sensitivity and Specificity; D015899:Tomography, Emission-Computed, Single-Photon; D014057:Tomography, X-Ray Computed
D058973:Folate Receptors, GPI-Anchored; D015609:Organotechnetium Compounds; D005492:Folic Acid