SAN FRANCISCOIsraeli investigators have developed a new method for
enhancing paclitaxel (Taxol) delivery to recurrent brain tumors and are using
diffusion-weighted magnetic resonance imaging (MRI) to monitor for response.
Physicist Yael Mardor, PhD, presented initial phase I/II trial results at
the 37th Annual Meeting of the American Society of Clinical Oncology (ASCO
abstract 217) on behalf of neurosurgeon Zvi Ram, MD, and other colleagues at
Sheba Medical Center, Tel-Hashomer Hospital, Israel.
The technique uses convection to overcome the blood-brain barrier. Small
pulses of paclitaxel are pumped through a catheter to the brain for several
days, inducing a pressure gradient within the tumor.
By using diffusion-weighed MRIs sensitive to the speed of water molecules,
the investigators were able to see immediate changes in images taken before,
during, and after treatment. "The idea is that we filter out the signals
from the fast water molecules and look only at the signals coming from slow
water molecules," Dr. Mardor said. "This kind of image gives specific
tissue characterization that is not obtained by conventional MRI."
The ASCO poster documented paclitaxel’s effect in the first three glioma
patients treated with the new technique. In an MRI taken shortly after a
patient received paclitaxel through a catheter, a bright spot appeared in the
brain, consistent with brain swelling. In subsequent images, the spot was seen
to spread. Dr. Mardor said that the spot shows the slowing down of water
molecules as a result of treatment.
"Several days after the treatment began, we saw within the bright spot
an appearance of a dark spot. The dark spot means fast water flow, which we
think is correlated with later necrosis of this tumor," she told ONI.
"And if you look at the conventional MRI, 2 weeks post-therapy, you see
that the therapy actually burned a hole in the treated area, so this patient
did respond to the therapy."
Dr. Ram’s technique for infusing paclitaxel enables patients to receive
very high concentrations of the drug over very high volumes of the brain, Dr.
Mardor said. The hope is that it will also be effective in other brain tumors
that do not respond to chemotherapy because of the blood-brain barrier.