Evidence based medicine advancing clinical expertise in breast cancer diagnostics

Several recent independent studies have focused on the use of Breast-Specific Gamma Imaging (BSGI) in different patient populations and have reported promising results. BSGI is a functional imaging procedure that is proving to be an effective tool in the early detection of breast cancer and in the differentiation of malignant and benign tumors.
BSGI, as a functional or molecular procedure, images cellular activity while both mammography and ultrasound image tissue density. Radiologists have long known that the presence of certain types of breast tissue, especially dense breast tissue, can increase the risk of breast cancer by masking some lesions on mammographic images. Functional imaging allows physicians to see the breast more clearly by accessing a map of cellular metabolism.
BSGI is more sensitive than its predecessor, scintimammography, and relies on the advanced imaging technology of anatomic specific detectors to optimize the results. Unlike conventional gamma cameras that have difficulty detecting cancers smaller than 1 cm, the Dilon 6800 exhibits significantly higher study resolution. BSGI with the Dilon system has been shown to detect cancers as small as 1 mm in clinical studies and practice, and demonstrates a very high sensitivity for DCIS and lobular carcinoma.

The following is a short summary of recent findings using BSGI.

BSGI vs. MRI in the Evaluation of Patients with Indeterminate Mammograms

A recent study published in the Breast Journal indicated that Breast-Specific Gamma Imaging (BSGI) may be more specific than MRI in the evaluation of patients with questionable mammograms. This sub-group of patients is difficult to manage and often requires follow-up imaging, which can increase patient anxiety and frequency of biopsy. Breast MRI resulted in 18 false positive cases while BSGI demonstrated only 7. Although MRI detected one cancer missed by BSGI, there was no statistically valid difference in sensitivity between these techniques. While BSGI and MRI did not exhibit any significant difference in sensitivity, BSGI displayed a significantly higher specificity for breast cancer. In addition, BSGI found cancers as small as 3mm in this study.

Brem RF, Petrovitch I, Rapelyea JA, et al. Breast specific gamma imaging with 99mTc-sestamibiand magnetic resonance imaging in the diagnosis of breast cancer— a comparative study. Breast J 2007;13 (5):465-9.

BSGI vs. Mammography and MRI in the detection of DCIS

Authors at The George Washington University Medical Center also recently published a retrospective study in Academic Radiology indicating that BSGI may also be more sensitive than MRI or mammography in the detection of ductal carcinoma in-situ (DCIS). The patient population consisted of women with suspicious mammograms, as well as high-risk women with a history of breast cancer and negative mammograms, bloody nipple discharge or palpable mass. Mammography detected 82 percent of the lesions in this study, missing a total of 4 cancers: two in patients with bloody nipple discharge and two DCIS lesions in the contralateral breast of patients with known primary lesions. BSGI, however, detected all of these. In addition, while MRI and BSGI were concurrent in several cases, BSGI detected a 4mm lesion that was missed by MRI. Two cases of low grade carcinoma in this study were also positive in BSGI. The authors observed the highest sensitivity for DCIS of 91% with BSGI, followed by 88 percent with MRI and 82 percent with mammography, and concluded that BSGI reliably detects sub-centimeter lesions and is a useful adjunct imaging tool for detecting DCIS.

Brem RF, Fishman M, Rapelyea JA. Detection of ductal carcinoma in situ with mammography, breast specific gamma imaging, and magnetic resonance imaging: a comparative study. Acad Radiol 2007;14(8):945-50.

The combined use of Mammography, Ultrasound and BSGI in breast cancer diagnosis

Two separate publications recently evaluated patients using mammography, ultrasound and BSGI. The first, presented in the spring of 2007 at the American Society of Breast Disease Annual Symposium, evaluated the sensitivity and specificity of BSGI and its use as an additional imaging tool to mammography and ultrasound. BSGI was performed on 205 women who had high-risk for breast cancer, newly diagnosed breast cancer, palpable mass negative in mammography and/or ultrasound, or inconclusive findings after mammography and ultrasound. Of these patients, there were 157 negative BSGI with 127 confirmed negative at 6 or 12 month follow up. BSGI displayed an overall sensitivity of 90.5% and a specificity of 87.5 percent. In addition, in 4 patients, BSGI detected more wide-spread disease than indicated by mammography.
Interestingly, BSGI did not miss any infiltrating lobular cancers but missed two small, low-grade cancers: one 1 mm and one 5 mm. The smallest cancer identified by BSGI in this study was 5 mm. The authors concluded that BSGI helped to avoid biopsy in 157 women with 127 confirmed negative with 6 or 12 month follow up at the time of publication and that BSGI is a valuable adjunct imaging technology that can serve to help identify unsuspected breast cancers.
Weigert J. Breast-specific gamma imaging (high-resolution molecular imaging of the breast): a useful adjunct to breast imaging. Poster presented at the annual symposium of the American Society of Breast Disease, San Francisco, California. April 2007.

The second publication was presented at the American Roentgen Ray Society. The authors studied the impact of triple diagnosis (mammography, ultrasound and BSGI) in patients with: palpable masses with negative mammogram, biopsy proven cancer, equivocal mammographic findings, and those at high risk for breast cancer. Overall sensitivity for BSGI was 96 percent and the smallest cancer detected by BSGI was 1 mm. In addition, this study demonstrated a sensitivity of 89 percent for sub-centimeter lesions, with half of these lesions being smaller than 5 mm. The sensitivity of BSGI for DCIS in this study is 94 percent even though the median size of DCIS was 7mm. The positive and negative predictive values of 70 percent and 94 percent respectively demonstrate that BSGI is an excellent adjunctive imaging procedure in patients where mammography alone is insufficient.

Floerke A, Brem R, Rapelyea J, Teal C, Kelly T. Breast Specific Gamma Imaging as an Adjunct Imaging Modality for the Diagnosis of Breast Cancer. Oral Presentation American Roentgen Ray Society (ARRS) meeting. Orlando, FL. May 9, 2007

Impact of BSGI in Pre-surgical Planning

Beth Israel Medical Center, located in New York City, presented a study at the 2006 American Society of Breast Disease that evaluated the use of BSGI in high risk or newly diagnosed breast cancer patients and its change in patient management. The study examined the first 163 women imaged at their institution who were newly diagnosed with cancer or at high risk, including those who had a personal or family history of breast cancer, mammographically dense breasts (which make mammograms difficult to read) or suspicious mammograms. The authors found that BSGI changed patient care management in 19 percent of their cases, almost two-thirds of which were pre-menopausal. Although BSGI missed 5 cancers, it also identified 5 new areas of cancer and 4 high risk lesions; 2 papillomas, one spindle cell tumor and one LCIS not found in mammography or ultrasound. Although this study was performed as a first experience study and therefore included the institutional learning curve, BSGI was shown to have a sensitivity of 88.6 percent and a specificity of 85.7percent. The study concluded that BSGI is a promising imaging modality for helping to optimize patient management.
Cocilovo C, Greene T, Gross J, et al. Breast specific gamma imaging: a clinical pilot study. Poster presented at the annual symposium of the American Society of Breast Disease, Las Vegas, Nevada. April 2006.

Additional studies currently under way:

• The utility of BSGI in monitoring primary tumor response to neo-adjuvant chemotherapy for both surgical planning and therapy modulation
• Comparison of BSGI axillary node imaging and sentinel lymph node pathology in the detection of axillary metastases
• Clinical impact of BSGI in patient management
• The effectiveness in evaluating lymphatic involvement in breast carcinoma patients using combination of BSGI and US for axillary node metastases detection
• Comparison of BSGI and MRI in the sensitivity and specificity of secondary mammographically occult malignant lesions in patients with known primary lesions.

BSGI in Clinical Practice:

Breast-Specific Gamma Imaging is being used in hospitals and private imaging centers across the country to help effectively manage challenging breast cases, such as for high-risk patients with equivocal mammograms, those who present with dense breasts, multifocality, scar tissue, implants, hormone replacement therapy, and palpable lesions not detected with mammography or ultrasound. BSGI is quickly becoming a standard of care in breast diagnostics, with over 20,000 patients imaged to date and the procedure being integrated into many leading medical centers, including Beth Israel and Cornell University Medical Centers in New York; The George Washington University Medical Center, Washington, D.C.; Methodist Hospital in Philadelphia and The Rose in Houston.

Ted Fogarty, MD, Radiologist Med Center One, Chairman of Radiology at University of North Dakota School of Medicine speaks of his Clinical experience with BSGI, “Our MQSA audits from 2003 to 2006 tell a striking story. Our practice averaged around 50 cancer diagnoses per year in 2003, 2004, and 2005. With the addition of BSGI in 2006 we found 93 cancers. We read a few more mammograms in 2006, but not the 5000 needed to achieve that increase on the usual mammographic statistics; it was clearly the impact of BSGI becoming a part of our institution’s breast cancer screening program. In addition, our PPV increased from 25 percent to 50 percent.”  

Broad Spread Bilateral Lobular Carcinoma

Clinical History – 61 year old patient with no prior history.

BSGI detected several satellite lesions which were occult in mammography and ultrasound, resulting in improved treatment planning.

Mammogram – Multiple bilateral masses and microcalcifications suspicious for malignancy including a 1cm mass in the right breast at 9 o’clock, 3cm mass in the left breast at 12 o’clock and a 1.5 cm mass in the left breast at 8 o’clock. BIRADS 0. Further evaluation with ultrasound is recommended.

Ultrasound – Three irregular masses correlating to those noted in mammography in size and location. In addition, there are some irregularities in the left axillary nodes. Biopsies of the masses are recommended.

BSGI – Multiple bilateral foci of uptake indicating high suspicion of the three masses observed by US, in addition to a large number of smaller areas of focal uptake. At least 5 new satellites are noted in the left breast and 4 in the right. There is also a focal enhancement in the axillary tail of the right breast possible indicating an involved node. Highly suggestive of broad spread bilateral malignancy.

Pathology – broad spread bilateral lobular carcinoma.

Patient case histories courtesy of The Rose, Houston, TX.