Molecular Imaging Is Changing the Course of Breast Cancer Treatment

For difficult-to-diagnose patients, a new imaging technology called breast-specific gamma imaging (BSGI) has been found to be a more useful adjunctive imaging tool than ultrasound for patients who need additional imaging following a questionable mammogram.

Molecular imaging has recently been shown to be highly effective, safe, and painless imaging tool for diagnosing and treating breast cancer. Clinicians are reporting that the information they have gained from molecular imaging technologies has resulted in decisions to change the course of treatment in between 24% and 48% of breast cancer cases.

With BSGI, the patient receives a pharmaceutical tracing agent that is absorbed by all the cells in the body. Because of their increased rate of metabolic activity, cancerous cells in the breast absorb a greater amount of the tracing agent than the normal surrounding tissue and typically appear as "hot spots” on the BSGI image.

Breast cancer is just one of many types of cancer for which new and emerging molecular imaging techniques and therapies can significantly improve detection, diagnosis, and treatment. "As a field, molecular imaging is evolving very rapidly,” said SNM (formerly called the Society of Nuclear Medicine; Reston, VA, USA) president Robert W. Atcher, Ph.D., M.B.A. "Each new discovery--whether through improved cancer diagnosis and treatment, increased understanding of the fundamental causes of Alzheimer's disease, or strides in how we treat cardiovascular disease--brings personalized medicine one step closer to reality. Molecular imaging techniques and therapies allow us to understand what is happening at a cellular level. Physicians can actually see the precise location of disease, determine if other organs are being affected, and then target treatment. It is about delivering the right treatment to the right patient at the right time.”

According to SNM researchers, molecular imaging has the potential to diagnose cancer early on--at its most curable stage; create a portrait of what cells are doing and how they function over time; eliminate the need for unnecessary exploratory surgery or multiple surgeries; provide a painless and cost-effective alternative to more expensive (and less accurate) diagnostic tests; confirm and treat suspected recurrent cancers; monitor an individual's response to treatment and make adjustments as necessary; and equip physicians and individuals with information to make informed decisions about the best course of action.

"Molecular imaging has the ability to detect abnormalities very early in the progression of disease or even before symptoms occur--potentially saving countless lives,” added Dr. Atcher. "Working together with patients and their caregivers, we can truly imagine the future.”

In the largest-ever study to compare molecular breast imaging (MBI) to mammography, in September 2008, researchers from the Mayo Clinic (Rochester, MN, USA) had demonstrated that MBI could detect three times as many tumors in women who have dense breast patterns on their mammogram and are at increased risk of breast cancer. With mammography, it is difficult to distinguish normal breast tissue from tumor tissue in women with dense breasts. As a consequence, women who have dense breasts as well as other breast cancer risk factors often need additional screening.

The study results were presented in September 2008, at the American Society of Clinical Oncology's 2008 Breast Cancer Symposium in Washington, DC, USA. "These results suggest that MBI could become an important screening tool for women who have dense breast tissue and increased breast cancer risk,” said Carrie B. Hruska, Ph.D., a research fellow in the department of radiology at Mayo Clinic. "Larger trials are needed to further validate our research, but it is encouraging to find that MBI can detect cancers that are not easily visible on screening mammography. Our next step will be to compare MBI prospectively to other screening methods, such as MRI.”

The latest study out of the Mayo Clinic involved a dual-headed dedicated gamma camera used during MBI, which was shown to accurately detect small breast tumors less than 2 cm in size. One hundred fifty patients who had suspicious lesions smaller than 2 cm in size were imaged using dual-head molecular breast imaging.

"There were 128 cancers confirmed in 88 patients,” according to Dr. Hruska, lead author of the study. "The sensitivity rate of dual-head MBI during the study was 90% (115/128),” she said. "Dual head MBI involves a very light, pain-free compression of the breast. Two views of each breast are performed, lasting for about 10 minutes per view. The patient receives an intravenous injection of a commonly used radiotracer and this tracer circulates throughout the body and is preferentially absorbed in the breast cancer.”

MBI is about the same cost as digital mammography. There are many women who could benefit from an additional test such as dual-head MBI that is both cost-effective and also has a good specificity (meaning it will not give a lot of false-positive results), Dr. Hruska pointed out. The findings were published in the December 2008 issue of the American Journal of Roentgenology (AJR).

Researchers have also recently compared BGI technology to ultrasound. "My colleagues and I found that in women who needed further examination beyond mammography in the diagnosis of breast cancer, BSGI offered more definitive answers than ultrasound,” said Dr. Jean Weigert, director of Women's Imaging at Mandell and Blau M.D.'s PC (New Britain, CT, USA). The study was recently presented in December 2008 at the annual meeting of the Radiological Society of North America (RSNA), held in Chicago, IL, USA

Dr. Weigert conducted a study comparing BSGI to ultrasound in patients who required additional imaging following a mammogram. As part of their diagnostic evaluation, 70 patients had mammography, ultrasound, BSGI, and biopsy. BSGI and ultrasound had 96% and 58% sensitivity, respectively, and 55% and 43% specificity, respectively. These results demonstrate that BSGI may be more effective than ultrasound as an adjunctive imaging technology to mammography.

BSGI for this study was performed using a Dilon Technologies (Newport News, VA, USA) 6800 gamma camera, a high-resolution, small field-of-view gamma camera, optimized to perform BSGI.

Dr. Weigert concluded that, "BSGI provided superior sensitivity and comparable--if not better--specificity in this group of patients with questionable mammograms requiring additional diagnostic imaging. BSGI may be a more useful modality than ultrasound as an adjunct imaging technology to mammography.”

Related Links:
SNM
Mayo Clinic
Mandell and Blau M.D.'s PC
Dilon Technologies