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Molecular Breast Imaging: Evaluation of a New Technique Using Scintimammography as a Potential Screening Tool for Women at Increased Risk of Breast Cancer
Background: Conventional scintimammography has a high overall sensitivity and specificity for the detection of breast cancer. However sensitivity drops to ~50% for the detection of breast lesions less than 10-15 mm in diameter, making it unsuitable as a screening tool. We have developed Molecular Breast Imaging (MBI) - a new technique which utilizes a Cadmium-Zinc-Telluride (CZT) gamma camera for scintimammography that has been shown to have a high sensitivity (92%) for the detection of breast lesions < 15 mm in diameter. Hence, MBI may be a valuable screening tool, particularly for women in whom the sensitivity of conventional mammography (MMO) is reduced by the density of the breast parenchyma. Hypothesis: (1) MBI has sufficiently high sensitivity and specificity and equal or higher positive predictive value than MMO or ultrasound in the high-risk dense breast sub-population, (2) MBI produces a sufficiently low false positive rate that permits its use as a screening tool in this patient population. Specific Aim: The aim of this study is to demonstrate the utility of MBI as an adjunct screening modality for the detection of occult breast cancers in a high risk dense breast population. Study Design: The clinical study will include a population of women who have been previously diagnosed with dense breasts (BI-RAD Category 3 or 4 / 4) and normal MMO (BI-RADS Category I or II/ V) and have high risk factors for breast cancer. The study population will comprise 700 women with: (1) A negative clinical examination; (2) A Category I or II MMO; Category 3 or 4 breast density, and (3) A Gail score equal to or greater than 1.7. All patients will have a screening MMO with computer aided diagnosis and will then undergo MBI. Patients with positive studies (MBI or MMO) will undergo biopsy of the lesion (either based on the MMO or from additional ultrasound or MRI studies). All patients will have repeat MBI and MMO studies at 1 and 2 years and a clinical follow-up at 3 years to determine if any interval cancers occur. Potential Outcomes / Benefits of Research: Demonstration that MBI has a high sensitivity and specificity for the detection of breast cancer in the high-risk dense breast population is a critical step in the development of MBI as a routine screening tool. The low cost of an MBI procedure (a factor of 5 to 10 times less than an MRI) should make this a viable and superior screening technique to MMO in this patient population.
In about 20% of patients who have mammograms, the breast tissue is very dense or bright on the mammographic images. As a consequence it can be very difficult for the radiologist to detect breast cancer in these images. One possible alternative screening technique in these patients is scintimammography. This technique uses a gamma camera and involves the injection of a small amount of a radioactive material that is taken up by the tumor. While this technique works reasonably well, it cannot reliably detect small tumors less than 1/2 inch in diameter. We have a new type of gamma camera that overcomes many of the limitations of conventional systems and in preliminary studies in patients, has been able to reliably detect tumors down to about 1/5 inch in diameter. In this study we propose to use this new gamma camera to study 700 patients who are know to have dense breasts on mammography and who are also known to be at a high risk of developing breast cancer. As part of this study, each patient will have a conventional mammogram and will then have a scintimammogram. If either study shows a suspected tumor, the patient will be referred for additional studies (using ultrasound or MRI) and / or biopsy of the suspected lesion. Both imaging studies will be repeated at 1 year and 2 years in order to detect any tumors that might have been missed or had developed in the intervening period. At 3 years, we will do a final clinical follow-up by mail with all patients to see if any of them developed breast cancer. From analysis of the mammograms and scintimammograms, we expect to be able to demonstrate that scintimammography with this new gamma camera is a useful and better screening technique than mammography in these patients.