Trial Information

Prospective Evaluation of the Effect of Corticotropin-Releasing Hormone Stimulation on 18F-Fludeoxyglucose High-Resolution Positron-Emission Tomography in Cushing's Disease

Objective

Preoperative imaging identification and localization of adrenocorticotropin hormone
(ACTH)-secreting pituitary adenomas is critical for the accurate diagnosis and the
successful surgical treatment of Cushing's disease (CD). Unfortunately, over 40 percent of
CD patients do not have a visible pituitary adenoma on magnetic resonance (MR)-imaging (the
most sensitive imaging modality for ACTH-positive adenoma detection and localization). Lack
of MR-imaging for diagnosis and to guide surgical resection results in significantly higher
rates of surgical failure compared to cases associated with adenomas visible on MR-imaging.
Because ACTH-adenomas are metabolically active compared to the surrounding pituitary gland,
(18)F-fludeoxyglucose ((18)F-FDG) positron emission tomography (PET)-imaging in CD patients
could be used to detect adenomas not detectable on MR-imaging. Moreover,
corticotropin-releasing hormone (CRH) can be given to selectively increase the metabolic
activity of ACTH-secreting pituitary adenomas to increase the likelihood of their detection
and localization by (18)F-FDG PET-imaging. To determine the effect of CRH stimulation on
(18)F-FDG uptake using PET-imaging in CD, we will perform (18)F-FDG high-resolution
PET-imaging (with and without CRH stimulation) in CD patients.

Study Population

Thirty male and female CD patients 8 years and older will participate in this study.

Study Design

This is a single center trial to determine the effect of CRH stimulation on (18)F-FDG uptake
in high-resolution PET-imaging of ACTH-adenomas in CD patients. CD patients will undergo
(18)F-FDG high-resolution PET-imaging without CRH stimulation and (18)F-FDG high-resolution
PET-imaging with intravenous CRH stimulation. The order of the PET scans will be randomized
and the second PET scan will occur greater than 24 hours but less than 14 days after initial
PET-imaging. For (18)F-FDG PET-imaging with CRH stimulation, intravenous (18)F-FDG will be
given just before CRH administration. The PET images will be read by radiologists who are
blinded to the administration of CRH. Within 12 weeks after completion of the last
(18)F-FDG high-resolution PET-imaging scan, patients will undergo surgical resection of the
pituitary adenoma. Surgical and histological confirmation of adenoma location will be used
to assess the diagnostic and localization accuracy of PET-imaging and to compare to
preoperative MR-imaging results in CD patients. Inferior petrosal sinus sampling (IPSS)
results will be compared with imaging results and with surgical and histological findings.

Outcome Measures

The primary objective of this study is to determine the effect of CRH stimulation on
(18)F-FDG uptake in high-resolution PET-imaging for CD. To assess and compare (18)F-FDG
uptake without and with CRH stimulation, we will compare (18)F-FDG standardized uptake
values (SUVs) in the region of interest (pituitary gland and pituitary adenoma). Secondary
objectives include determining if CRH stimulation enhances detection of ACTH-adenomas as
demonstrated on (18)F-FDG high-resolution PET-imaging and assessing the accuracy and
sensitivity of (18)F-FDG high-resolution PET-imaging detection of ACTH-adenomas compared to
MR-imaging. Measures to assess for these secondary objectives include comparing (18)F-FDG
high-resolution PET-imaging (with and without CRH stimulation) detection to (1) MR-imaging
detection of adenomas, (2) IPSS results, and (3) actual tumor location confirmed by
histological findings to location predicted by PET- and MR-imaging within patients.