A Pilot Study of 18F Fluorothymidine (FLT) PET/CT in Lymphoma

Background:

• Positron emission tomography (PET) uses radioactive substances called radiotracers to locate areas of cancer in the body. For this test, the patient is given an injection of the radiotracer and lies in a large donut-shaped scanner that detects where in the body the radioactivity accumulates. Computed tomography (CT) scans use low dose x-rays that help to better localize where the radioactive tracer is concentrating. PET/CT scans are usually done in lymphoma patients before treatment starts and at the end of treatment to evaluate the response to therapy.
• PET scans typically use a sugar-like radioactive tracer called fluorodeoxyglucose (FDG) and low-dose x-rays. Sometimes, however, FDG PET scans show what looks like active disease and presence of a mass after chemotherapy even when there are no live cancer cells. Doctors have particular problems in evaluating response to treatment when this happens because they can't tell if the mass is active cancer or just dead tumor cells.
• An experimental radiotracer called 18F- Fluorothymidine (FLT) has high uptake in active tumor cells and may be better able to evaluate treatment response.

Objectives:

• To test the use of FLT PET/CT imaging in assessing treatment response in patients with lymphoma.

Eligibility:

• Patients 18 years of age or older who are enrolled in a lymphoma therapy study at the National Institutes of Health (NIH) Clinical Center or in the Cancer and Leukemia Group B (CALGB) 50330 study at another location.

Design:

• There are two arms in this study:

• The first arm evaluates FLT as an early predictor of tumor response to therapy. Patients are imaged with FLT and FDG PET before starting treatment, following two cycles of therapy and after treatment ends.
• The second arm evaluates the ability of FLT to distinguish if a mass that remains after treatment has viable cancer or dead tissue. Patients who have completed treatment and in whom FDG PET shows a remaining tumor mass are imaged with FLT PET. Following the scan, the tumor is biopsied for verification.