Fluoroethyltyrosine F-18 PET Scan for Adults with Suspected Functional Pituitary Adenoma and Unclear MRI Results

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What is this study about?

The study focuses on adults who have a functional pituitary adenoma, a type of tumor that can cause hormone problems. Common forms of this tumor include prolactinoma, Cushing’s disease, acromegaly and thyrotropic adenoma. In many cases the usual brain scan called MRI does not clearly show the tumor, making it hard for doctors to decide on the best treatment. To help clarify the situation, participants receive an injection of a substance called fluoroethyltyrosine f-18 and then undergo a special scan known as 18F-fluoro-ethyl-tyrosine (18FET) PET. This scan works like a camera that highlights areas where the tumor takes up more of the injected substance than the surrounding healthy brain tissue.

The purpose of the study is to estimate how often the PET scan shows a positive result in these patients. After the injection, the scan is performed and the images are read by three experts who look for a spot of increased uptake, described as a “positive” scan. Participants are then followed for about a year to see whether the scan results lead to surgery or radiation treatment, and to observe any changes in hormone levels. The study also records technical details of the scan, such as the amount of signal measured by SUVmax, SUVmean and SUVpeak, to better understand how the test works in different tumor types.

1 baseline assessment after enrollment

after joining the study, you will undergo a baseline clinical assessment that includes a review of your medical history, physical examination, and laboratory tests to measure hormone levels.

the pituitary magnetic resonance imaging that was already performed will be reviewed together with the study team to confirm eligibility.

2 pre‑pet preparation

you will be scheduled for a day on which the 18f‑fluoro‑ethyl‑tyrosine scan is performed.

on that day, an intravenous line will be placed in a vein in your arm.

3 intravenous injection of tracer

through the intravenous line, you will receive a single dose of 250 mbq of fluoroethyltyrosine f‑18 (the radioactive tracer).

the injection is given as a quick bolus and does not require any preparation beyond fasting for a short period if instructed.

4 pet imaging

immediately after the injection, you will be positioned on a scanning table and a pet scan of the pituitary region will be performed.

the scan typically lasts between thirty and sixty minutes, during which you are asked to remain still.

the purpose of the scan is to detect focal areas of increased tracer uptake that may indicate an active adenoma.

5 post‑scan observation

once the scan is complete, you will be observed for a short period (about fifteen minutes) to ensure that no immediate reaction occurs after the tracer injection.

if any symptoms arise, they will be evaluated by medical staff.

6 result review and treatment planning

within a few days, the images will be reviewed by three independent readers to determine whether the scan is positive or negative.

the outcome will be discussed with you, and a decision about further treatment (surgery, radiation, or observation) will be made based on the results.

7 treatment (if indicated)

if the scan is positive and surgery or external beam radiation therapy is recommended, the chosen procedure will be scheduled and performed during the 12‑month study period.

the specific type of treatment will follow standard clinical practice for the hormonal subtype of the adenoma.

8 regular follow‑up visits

you will attend follow‑up visits at approximately 1 month, 3 months, 6 months, and 12 months after the scan.

each visit includes a physical examination, repeat hormone laboratory tests, and assessment of any symptoms.

if you undergo surgery or radiation, additional visits may be scheduled to monitor recovery and treatment response.

9 final study assessment

at the end of the 12‑month period, a final evaluation will be performed to document the outcome of any treatment and to record whether the scan result correlated with clinical response.

the final data are used to determine the study’s primary and secondary endpoints.

Who Can Join the Study?

Be a man or a woman.
Be 18 years old or older.
Have a suspected functional pituitary adenoma – a hormone‑producing tumor in the pituitary gland. This may be a prolactinoma (produces prolactin), Cushing’s disease (produces excess cortisol), acromegaly (produces excess growth hormone), or thyrotropic adenoma (produces excess thyroid‑stimulating hormone).
The tumor may be new (de novo) or have come back or remained after previous treatment (recurrence/persistence).
Have an indeterminate pituitary MRI – a brain scan that does not clearly show whether the tumor is present.
Be covered by social security (have health insurance that pays for medical care).
Agree to follow all study steps and stay in the study for its entire length.
Be able to have surgery and/or radiation treatment if the PET scan shows the tumor is suitable for those therapies.

Who Cannot Join the Study?

Pregnancy – you are currently pregnant.
Known hypersensitivity to radiopharmaceuticals – you are allergic to medicines that contain a tiny amount of radioactive material used for imaging.
Administrative reasons – you cannot give informed consent (agree to take part after understanding the study), cannot take part for the whole study, do not have social security coverage, or refuse to sign the consent form.
Active alcohol consumption – you are currently drinking alcohol regularly.
Liver disease or severe uncontrolled epilepsy – you have serious liver problems or epilepsy (a condition causing seizures) that is not well controlled.
Deprived of liberty (guardianship, curatorship, etc.) – you are under legal guardianship or similar restrictions that limit your ability to make decisions.
Does not speak French – you cannot understand or speak French, which is needed for the study.

Where you can join this trial?

Verified and Recommended Sites

No sites found in this category

Verified Sites

Site Name	City	Country	Status
Centre Hospitalier Universitaire De Lille	Lille	France

Other Sites

No sites found in this category

Trial status

Country	Status	Recruitment Start
France	Not yet recruiting	01.09.2026

Trial locations

Investigated drugs:

Fluoroethyltyrosine F-18

18F‑fluoro‑ethyl‑tyrosine (FET) is a special radioactive substance that is injected into a vein before a PET scan. It travels through the bloodstream and is taken up by cells that are actively growing, such as the cells in a functional pituitary adenoma. Because it emits a tiny amount of radiation, the PET scanner can create detailed images that show where the tumor is located and how active it is. This helps doctors decide whether surgery or radiation therapy might be needed, especially when a regular MRI does not give clear information. The tracer is used only for imaging and does not treat the tumor itself.

Prolactinoma – A non‑cancerous tumor of the pituitary gland that makes too much prolactin, a hormone that controls milk production. The excess hormone can cause menstrual changes, infertility, or unwanted breast milk in women, and reduced libido or erectile problems in men. The tumor usually grows slowly, and the hormonal effects often develop gradually over months or years. As the lesion enlarges, it may press on nearby structures, leading to headaches or visual disturbances.

Cushing disease – A pituitary tumor that releases excess ACTH, which in turn makes the adrenal glands produce too much cortisol. Elevated cortisol causes weight gain, round face, and easy bruising, which typically appear over several months. The tumor often expands slowly, and the hormonal excess may worsen as the lesion grows. Continued hormone overproduction can lead to changes in skin, muscle, and bone over time.

Acromegaly – A pituitary adenoma that secretes excess growth hormone, leading to enlarged bones and soft tissues. The physical changes, such as larger hands, feet, and facial features, develop slowly and become noticeable over years. The tumor may increase in size, occasionally pressing on nearby nerves and causing headaches or vision problems. Hormone excess continues as long as the tumor remains active, gradually affecting many body systems.

Thyrotropin‑secreting pituitary adenoma – A tumor of the pituitary gland that produces too much thyroid‑stimulating hormone (TSH), causing the thyroid gland to release excess thyroid hormone. The resulting high thyroid levels can cause rapid heartbeat, weight loss, and nervousness, which often appear gradually. The adenoma may slowly enlarge, potentially leading to pressure symptoms such as headaches or visual field changes. Ongoing hormone overproduction continues as the tumor persists.

Trial ID:

2025-523829-17-00

Protocol code:

2025_0205

Trial Phase:

Therapeutic exploratory (Phase II)

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Fluoroethyltyrosine F-18 PET Scan for Adults with Suspected Functional Pituitary Adenoma and Unclear MRI Results

What is this study about?

Who Can Join the Study?

Who Cannot Join the Study?