Oct 4 2007
Study results recently published in the Journal of Academic Radiology indicate that Breast-Specific Gamma Imaging (BSGI) provides higher sensitivity for the detection of ductal carcinoma In Situ (DCIS) than mammography or MRI and can reliably detect small, sub-centimeter lesions. The study, performed by Dr. Rachel Brem and colleagues at The George Washington University Medical Center, evaluated the technology on women with mammographically suspicious microcalicifications and other high risk factors.
Breast-Specific Gamma Imaging (BSGI) -- molecular imaging of the breast utilizing a high-resolution gamma camera -- is an increasingly utilized adjunct imaging modality for the diagnosis of breast cancer. Recent studies and clinical work on over 20,000 patients have demonstrated the significant value of BSGI as a complement to mammography in detecting breast cancer.
The Brem study demonstrated the efficacy of BSGI in helping to find otherwise mammographically occult cancers and in determining the true extent of disease in order to optimize surgical planning. Specifically, BSGI detected low-grade DCIS and identified several lesions <4 mm not found on mammography or MRI. BSGI detected all DCIS lesions less than or equal to 10 mm and the smallest mass noted was 2 mm.
"We believe this is an important contribution to the literature in that it compares different imaging modalities for the diagnosis of DCIS, a timely issue," said Dr. Brem.
DCIS
Ductal carcinoma In Situ (DCIS), the most common type of non-invasive breast cancer, occurs in approximately 28 percent or over 58,000 cases of breast cancer in the U.S. each year. Mammography, the only accepted screening tool for breast cancer, detects the majority of clinically hidden DCIS, depicted as microcalicifications, the hallmark mammographic finding of DCIS. Yet, the diagnosis of DCIS remains difficult as mammography is unreliable in predicting the physical presence and extent of DCIS.
Breast MRI has been shown to have a sensitivity -- the ability to detect that disease is present -- of 73-89 percent for DCIS, but a limited specificity -- the ability to detect that disease is not present -- of 58-89 percent, and a variable positive predictive value of 25-84 percent. As with mammography, areas of DCIS are difficult to detect on MRI, particularly lesions less than 5 millimeters.
In addition, MRI may overestimate DCIS extent in as many as 50 percent of cases and often cannot distinguish benign from malignant lesions, high-grade from low-grade DCIS, or detect an invasive component concurrent with the DCIS," said Dr. Brem. "As a result, MRI remains a secondary study with limitations in DCIS detection and evaluation."
Nature of the study
In the retrospective study, 20 women with 22 biopsy-proven DCIS lesions were reviewed. Patients had BSGI with the Dilon 6800, a high-resolution, small-field-of-view gamma camera with standard mammographic views. Image findings were compared to findings at biopsy or surgical excision. The sensitivity of BSGI, mammography, and when performed, MRI were determined for the detection of DCIS.
BSGI versus MRI
The findings indicate that the pathologic tumor size of the DCIS ranged from 2-21 millimeters. Of the 22 cases of biopsy-proven DCIS in 20 women, 91 percent were detected with BSGI, 82 percent were detected with mammography, and 88 percent were detected with MRI. BSGI had the highest sensitivity for the detection of DCIS, although this small sample size did not demonstrate a statistically significant difference. Two cases of DCIS (9 percent) were diagnosed only after BSGI demonstrated radiotracer uptake in the opposite breast that had been previously undetected by mammography. Two lesions were undetected by BSGI studies.
Details about BSGI with the Dilon 6800 Gamma Camera
Breast-Specific Gamma Imaging (BSGI) performed with the Dilon 6800, is a molecular breast imaging technique that can see lesions independent of tissue density and discover very early stage cancers. BSGI serves as a complementary diagnostic adjunct procedure to mammography and ultrasound for difficult- todiagnose patients. With BSGI, the patient receives a radioactive tracing agent that is absorbed by all the cells in the body. Cancerous cells in the breast, due to their increased rate of metabolic activity, absorb a greater amount of the tracing agent than normal, healthy cells and generally appear as "hot spots" on the BSGI image.
BSGI is ideal for patients with mammograms that are difficult to interpret due to a variety of factors, such as: dense breast tissue, suspicious areas on a mammogram, lumps that can be felt but not seen with mammography or ultrasound, implants and breast augmentation, scarring from previous surgeries and for women with a strong positive family history of breast cancer.