Perfusion PET Sarcoma: Feasibility of tumor perfusion quantification with Gallium-68-citrate PET/CT in sarcoma and radiotherapy

Tumor vasculature is an important factor in biological response to treatment.
Imaging of tumor perfusion both before and after treatment is difficult, and
existing techniques have their merits and disadvantages. Diffusion and contrast
enhanced perfusion weighted magnetic resonance (MR) imaging have shown some
promising results, but MR is laborious, expensive, and difficult to quantify.
Dynamic contrast enhanced computed tomography (ceCT) is quantitative, but
yields a radiation dose for a limited field of view.
We propose an alternative method for visualization of tumor perfusion in
humans, using the Gallium-68-citrate perfusion tracer and positron emission
tomography (Perfusion-PET) imaging. This dynamic and 3-dimensional technique is
readily available, and is able to (a) quantify the regional blood volume in
tumor tissue, and (b) quantify leakage to the extracellular space as a
parameter of vascular permeability. These parameters may be indicative of the
treatment outcome of radiotherapy, and may be of future value for treatment
selection or adaptation.

The study aims (1) to determine the feasibility of Perfusion-PET with
Gallium-68-citrate, prior to and during radiotherapy, and (2) to better
understand the process of vascular response of tumor to radiotherapy, including
differences between MLS and non-MLS. Secondary aims are to optimize the
procedure, and to derive new (research) approaches for personalised treatment
strategies.

Twenty (20) patients who have been referred for preoperative radiotherapy on a
primary sarcoma (any site) will be asked to undergo perfusion-PET as a study
procedure. This group will be divided in 2 subgroups: an MLS-group (n=10) and a
non-MLS group (n=10). The MLS patients will serve as a so called positive
control: good vascularization at diagnosis and a shut-down during radiotherapy.
The perfusion phenomena in patients with non-MLS histologies are unpredictable
and they will be regarded each as a study subject by themselves.
The perfusion-PET will be performed prior to radiotherapy and after the 8th,
the 16th and the 25th fraction of external beam radiotherapy.
Changes in tumor blood volume and extravasation will be plotted against the
number of fractions radiotherapy given. The images will be correlated with
histopathology at the time of resection.

4x Intravenous administration of a (known to be safe) radioactive tracer,
followed by a PET with lowdose CT scan, for a total
radiations exposure of maximum 6 mSv. Longer stay in the department of
nucleaire geneeskunde for a maximum of 1 hour (after the radiotherapy
treatment).