89Zr-rituximab PET/CT for detection of central nervous system lymphoma

Approximately 2-5% of brain tumours is a primary central nervous system
lymphoma (PCSNL), the majority of which are diffuse large-cell B-cell lymphoma.
Although PCNSL may have characteristic imaging findings on traditional CT and
MR imaging, none of these will unequivocally differentiate CNS lymphoma from
other brain lesions. A primary CNS lymphoma cannot, by definition, be diagnosed
from sites outside the CNS; only in a minority of patients can cerebrospinal
fluid analysis (from lumbar puncture) or ophthalmologic analysis (vitreous body
biopsy) provide a diagnosis. Presently, to make the diagnosis, it is necessary
to do an invasive biopsy of CNS lymphoma for histopathological analysis. This
biopsy only has a diagnostic aim, since - contrary to primary brain tumours -
resection does not contribute to outcome in CNS lymphoma1,2. Complications of
biopsy, such as bleeding and brain edema are more common in patients with CNS
lymphoma than in other primary brain tumours and are seen in 8% of biopsies.
One percent of patient will die of complications after biopsy and in 7% of
patients it is not possible for the pathologists to make a definite diagnosis
of lymphoma 3. With the aid of PET imaging with the tracer 89Zr-rituximab it
might be possible to accurately diagnose malignant brain lymphoma.
89Zr-rituximab is a tracer that binds CD20 antigen, a membrane protein. CD-20
is expressed on normal mature B-cell lymphocytes and also on malignant lymphoma
cells. If a 89Zr-rituximab PET could adequately predict that a brain tumour is
a malignant lymphoma this might prevent some invasive diagnostic biopsies and
complications from these invasive biopsies.

The objective of the study is to confirm that PCNSL is positive on
89Zr-rituximab PET imaging.

This prospective diagnostic proof of concept study will investigate
89Zr-rituximab PET uptake in CNS lymphoma.

Patients participating in the study will undergo additional 89Zr-rituximab PET
imaging before diagnostic brain biopsy. The proposed study is considered safe
and well tolerable. The risks of the extra 89Zr-rituximab PET are negligible.
The study may lead to insights about the possible added value of using
89Zr-rituximab PET in patients with brain tumours suspicious of primary CNS
lymphoma.
There is a very small chance that the extra radiation may lead to adverse
health effects. This is a negligible risk.