· Running the Numbers
· Mayo Researchers Develop Tool to Spot Small Breast Tumors
· Prostascint Added to NCCN Clinical Practice Guidelines
· Customized Radioisotopes Could Attack Cancer Cells More Efficiently


Running the Numbers

The risk of breast cancer recurrence increased 3.5 times among older women who did not receive radiation after breast-conserving surgery, according to a study published in Cancer.1 To examine the impact of treatment on the occurrence of recurrent and additional breast tumors, Ann M. Geiger, MPH, PhD, and researchers at Wake Forest University School of Medicine, Winston-Salem, NC, retrospectively followed 1,837 women aged 65 and older for the 10 years after they had surgery for early-stage breast cancer. Regardless of age or comorbidities, the women who underwent breast-conserving surgery but not radiotherapy were more likely to have recurrence of the disease or to develop additional breast tumors, compared to women who received breast-conserving surgery and radiation, or mastectomy alone. These results held regardless of tamoxifen treatment, suggesting that adjuvant radiation treatment was highly effective.

Reference

  1. Geiger AM, Thwin SS, Lash TL, et al. Recurrences and second primary breast cancers in older women with initial early-stage disease. Cancer. 2007;109:966-974.

Mayo Researchers Develop Tool to Spot Small Breast Tumors

By Renee DiIulio

Michael O’Connor, PhD, professor of radiologic physics at the Mayo Clinic College of Medicine, Rochester, Minn, is anxious to evaluate in multicenter trials a new nuclear medicine imaging technique, molecular breast imaging (MBI), which was developed by researchers at the Mayo Clinic. Early research indicates that the modality has promise as a screening method for breast cancer. Now, O’Connor says, the medical community needs to produce some units for use in studies that can prove this potential.

Michael O?Connor, PhD

Invoking the chicken?egg dilemma, O’Connor says, “We need good results to convince manufacturers to build them, but if they don’t build them, we don’t have the instruments needed to produce those results.”

Building a Prototype

The Mayo Clinic team is working with prototypes that they built themselves. During his consultant days, O’Connor acquired the first detector after evaluating a new device from GE Healthcare, Waukesha, Wis. “We had looked at breast imaging with gamma cameras about 5 years before then and had decided it was a waste of time,” he says.

But the new detector had promise. Working in collaboration with GE Healthcare and Gamma Medica-Ideas Inc, Northridge, Calif, which supplied later detectors, O’Connor and his colleagues built prototypes using stripped-down mammography units. The current MBI model replaces the cassette and compression unit of a mammography device with two semiconductor-based gamma cameras. “We were unable to use conventional gamma cameras because they have dead space that makes it difficult to get the breast into an active part of the detector,” O’Connor says.

The current protocol requires four 10-minute images; the examination takes about 40 minutes. O’Connor would like to reduce that to 20 minutes to increase its practicality for screening.

The breast is still compressed for the gamma camera image—for roughly 5 to 10 minutes to prevent movement—but the pressure is not as strong as that for mammography. The gamma camera unit requires 15 pounds of pressure; mammography uses 45 to 50 pounds of pressure, O’Connor explains.

The radiation exposure is equal to that of mammography. “We tailored the dose to match a mammogram,” O’Connor says. The patient is injected with a small amount of sestamibi, a radioactive drug that preferentially travels to tumors, which absorb the substance and become more visible in the image.

“With gamma cameras, the closer you are to the surface of the camera, the better the resolution,” O’Connor says. “But these cameras have better intrinsic resolution. They have better contrast and can see smaller objects. We couldn’t see much below 15 mm before, and now we can see objects that are 4 or 5 mm in diameter.”

Early data has shown about a 93% overall sensitivity in patients with known tumors. The system has detected tumors 10 mm in diameter in 88% of all patients in which it has been used. These findings indicate that the modality is able to detect tumors that mammography has missed. Also, no side effects have been reported.

Making Progress

The researchers are now studying the technique in asymptomatic, high-risk women, with the goal of examining 2,000 patients. “We have examined about 350 patients so far,” O’Connor says. “Mammography picked up two tumors, but we found eight. So, we’re doing well.”

He compares the results with those of MRI. “MRI has produced similar findings. The big difference is cost. MRI is very expensive and can run several thousand dollars,” O’Connor says, crediting the expense with preventing the modality from becoming a screening tool. He estimates that mammography costs about $100 to $200, and ultrasound roughly $300 to $400. This new technique would run about $500. “It is more expensive than mammography, but less than MR,” O’Connor says.

Currently, MBI would fall into the same category as scintimammography, another nuclear imaging technique that has been approved by the FDA as a complementary diagnostic to mammography. But O’Connor has bigger plans involving additional research: “It will be a long process, but we would like to develop molecular breast imaging into a screening technique on its own.”

O’Connor estimates that it will take another 18 months to 2 years to complete the current study with 2,000 subjects, and the team is lining up additional studies. “We would like to compare the technique with MRI, and we have a wish list of small projects to solidify our understanding of how the system works,” he says.

The next step is to commercialize. “We need a company to build and [obtain approval for] an instrument to use in multicenter trials,” O’Connor says. “We know the technology works. We now have to convince everyone else.”

Renee DiIulio is a contributing writer for  Medical Imaging. For more information, contact .

Prostascint Added to NCCN Clinical Practice Guidelines

The National Comprehensive Cancer Network (NCCN), Jenkintown, Pa, a nonprofit alliance of 20 of the world’s leading cancer centers, recently incorporated Prostascint (capromab pendetide) into its updated clinical practice guidelines for recurrent prostate cancer. Issued on an ongoing basis, NCCN’s clinical practice guidelines are intended as benchmarks for clinical policy in the oncology community and are based on evaluation of scientific data integrated with expert judgment on the part of multidisciplinary panels of expert physicians from member institutions.

Prostascint, produced by Cytogen Corp, Princeton, NJ, is the first commercial monoclonal antibody-based agent to target prostate-specific membrane antigen for imaging the spread and severity of prostate cancer. “Proper selection of therapy depends on whether prostate cancer has spread from the prostate gland,” Michael Manyak, MD, vice president of medical affairs at Cytogen, noted in a press release. “The NCCN guidelines recognize that fused Prostascint images can assist in that determination.”

Recent data by researchers experimenting with fusing a Prostascint-enabled functional study over an anatomic image, such as those obtained by CT or MR devices, has generated renewed interest in using fused scans in both disease assessment and treatment planning. One study at the Case Western Reserve University School of Medicine, Cleveland, looked at the difference in biochemical disease-free survival between patients, using the images to assess who had suggested metastatic deposits and who did not. “The use of these fused Prostascint scans has significantly benefited our patients receiving brachytherapy,” noted Rodney Ellis, MD, a radiation oncologist at Case Western and lead author of the study. “The expanded NCCN guidelines take into consideration these and other findings that have improved prostate cancer localization through the use of fused Prostascint images.”

For a complete library of NCCN?s clinical practice guidelines, visit
www.nccn.org/professionals/physician_gls/default.asp.

—C. Vasko

Customized Radioisotopes Could Attack Cancer Cells More Efficiently

Radioisotope therapy will lead the way to customized cancer treatment for patients, according to Thomas Ruth, PhD, director of the TRIUMF PET program at the University of British Columbia, Vancouver, Canada, who presented his research at the annual conference of the American Association for the Advancement of Science (AAAS), held on February 15?19 in San Francisco. Ruth and his team are taking large portions of radioactive material and separating out the particular atoms necessary for therapy.

“Individual therapy means patients will require fewer radiation doses and treatment sessions,” Ruth said. “And the patient isn’t the only one who benefits. Doctors do not have to spend as much time treating patients, and hospitals will spend less money helping those patients get better.”

Because radioactive chemicals decay in a predictable way while emitting radiation, it is possible to more efficiently target cancer cells with radioisotopes tailored to each patient. Ruth and his colleagues use the

TRIUMF particle accelerator to isolate different chemicals for therapeutic use; the primary challenge is figuring out how to produce Rhenium 186, the element they need for treatment, in a cost-efficient way.

For now, the team purchases the most common type of rhenium—from either MDS Nordion, Kanarta, Ontario, or the University of Missouri Research Reactor Center, Columbia—then experiments with how best to ionize the chemical. “Right now, getting Rhenium 186 is a difficult and expensive process,” Ruth said. “The key is to make this practical for the people who need to use it. In the next few months, we will partner with local hospitals and begin preclinical trials—and in the meantime, improve on the way we extract it to make it easy to purchase and cheap to use.”

—C. Vasko