News Story

· PET Locates, Images Prostate Cancer Travel
· FDA Clearance: Crystallizing Nuc Med Offerings
· Progressive Partners: 7T MRI: Two Better Than One!

PET Locates, Images Prostate Cancer Travel

Researchers at the University of California, Los Angeles, recently used positron emission tomography to locate prostate cancer cells as they spread to lymph nodes, where prostate cancer travels before invading other organs.

Lily Wu, MD, PhD

Using an engineered common cold virus, the team delivered a protein payload that could be expressed only in prostate cells. The study’s findings could assist oncologists in finding the cancer’s spread earlier, making it more treatable, according to senior author Lily Wu, a researcher at UCLA’s Jonsson Cancer Center and associate professor of pharmacology and urology.

“I think this is very exciting for many reasons,” Wu said. “We now know we can reach these prostate cancer metastases at an earlier stage than before, and we know we can deliver genes to those cancer cells that produce proteins that can be imaged by PET. Now we will find out how effective this genetic toxic payload is in preventing further spread of the cancer to other vital organs.”

Employing a prostate cancer-specific vector, the researchers introduced the virus into a tumor in a mouse and were able to detect PET signals only from the lymph nodes with cancer cell involvement. This indicated the virus had reached and infected the prostate cancer cells and produced the imaging protein.

Wu said the spread of prostate cancer to the pelvic lymph nodes is the most reliable indicator that the patient will have a poor prognosis and will likely experience disease recurrence and progression. The accurate evaluation of the pelvic lymph node involvement is critical in planning patients’ treatments, she continued.

Wu also co-developed TSTA, a two-step transcriptional amplification method that increased the expression of the genetic payload inside the cancer cells, which boosted the imaging signals and potential killing activity of the engineered virus.

Conventional imaging methods, such as CT, have a difficult time detecting the tiny cancer metastases in the pelvic lymph nodes. Furthermore, physicians cannot determine if a treatment is attacking cancer cells until they see a decrease in tumor size, which can take months. If the treatment were not effective, patients would have been exposed to a toxic therapy that ultimately did not help them. Wu’s technique would allow an oncologist to learn within days whether the treatment worked or whether the cancer has spread.

Next up, Wu and her group are working to link the noninvasive imaging advance with a treatment component. Specifically, they look to activate a toxic agent in the genetic payload to kill the spreading cancer cells. Their goal is to locate tiny prostate cancer metastases in patients, kill the diseased cells at the same time, and monitor the entire process on a PET scanner. Now, Wu is refining the image-guided therapy in the lab in mouse models.

“It would represent a treatment advance in patients for whom the outcome is not good,” Wu said regarding the image-guided therapy technique. “This would help improve the prognosis for these patients by letting us find and treat these metastases early. If we can catch the cancer before it invades other organs, we have a better chance to change the outcome for these patients.”

Wu’s approach first emerged in the field of breast cancer with testing of the sentinel lymph nodes. While a biopsy can determine if the cancer is in the sentinel node, the lymph nodes associated with prostate cancer are much more difficult to access for biopsy. Therefore, Wu’s method represents a noninvasive alternative.

Wu received support from an interdisciplinary grant from the Jonsson Cancer Center 5 years ago. The study was published in the July issue of Nature magazine.

—Elaine Sanchez

7T MRI: Two Better Than One!

Sometimes, two companies are better than one. That’s why GE Healthcare, Waukesha, Wis, and Varian Medical Systems Inc, Palo Alto, Calif, just announced a new partnership under which the two companies will collaborate in developing a preclinical 7T MRI system. Both initial development and integration will be a joint effort between the two companies; following development, Varian will market and distribute the new system.

Bryan Mock

“Varian has a very nice research system, and GE is known for cutting-edge clinical applications and sequences,” said Bryan Mock, global high-field MR product manager for GE Healthcare. “So we thought we should get together and marry Varian’s hardware with GE’s front end, creating a clinical translational research system with better workflow and improved productivity.”

The new system’s magnet, gradients, positioning devices, and RF coils will be provided by Varian, while GE will supply the electronics, user interface, pulse sequences, and applications. It will be optimized for preclinical imaging in soft tissues, including brain and organ imaging, tumor assessment, disease progression, and functional imaging.

“Preclinical 7T MRI has a variety of applications,” Mock said. “It’s useful in investigating changes in anatomy, metabolism, and physiology during drug research. It helps investigators better understand metabolic pathways.”

Mock explains that the system will come complete with all the clinical software applications for MR currently offered by GE. “It runs the gamut from proton-based imaging through spectroscopy,” he said. “Of course, when you talk about the preclinical environment, the fields of view are all much smaller. So we are modifying the applications to support imaging at much higher resolutions than would normally be done clinically.”

This will lead to additional potential applications of the new system, including investigating new contrast agents, monitoring gene expression, analyzing protein interactions, and determining pharmacokinetics. MR spectroscopy can be used to measure the concentrations of molecules in the body to measure neurotransmitters in the brain or metabolites in muscle.

Mock notes that performing this kind of imaging on large animal populations requires the kind of user-centric design not often seen in today’s preclinical MR systems. “The front end of most available systems is not as user-friendly as people would like it to be,” he said. “It takes a while to set up experiments. By marrying these two technologies, we think we will be creating a much more robust system for everyday, routine use.”

Preclinical imaging is a “key area of growth” for Varian, according to Garry Rogerson, the company’s president and CEO. “Our established MRI product range is highly regarded by the MR scientific community, and this new system enables us to reach beyond our traditional customers,” he said. While GE currently manufactures preclinical PET and CT systems, this will be the company’s first preclinical MRI offering. The companies anticipate rolling out the system by around this time next year.

“We feel this system is an ideal addition to our existing preclinical MRI product line,” said Martin O’Donoghue, vice president of scientific instruments for Varian. “It will appeal to the burgeoning group of researchers who have experience with GE MRI systems. We feel this will give them the preclinical MR imaging tool they have been looking for.”

—C. Vasko