Imaging of the breast is an important tool in the early detection, diagnosis and monitoring of response to treatment in breast cancer. Mammography has been the gold standard for detection of breast cancer for many years. Mammographic findings are based on anatomic changes in the breast and detection is based on differences in density of normal and abnormal tissues. However, the ability of mammography to correctly spot cancer varies from greater than 80% in women over the age of 50 to 68% for women 40 to 44 years of age. This difference is due to increased breast density in younger women. Ultrasound (US) uses high-frequency sound waves to create a picture of an area of interest. It is most frequently used to direct biopsy and to determine whether a lump is solid or cystic. Magnetic Resonance Imaging (MRI) uses magnetic fields to produce detailed cross-sectional images providing very good soft tissue contrast. MRI of the breast is now used in addition to mammography, as a test in high risk women for detection of breast cancer. In addition, MRI is increasingly being used prior to breast cancer surgery to assess the extent of tumor.
Another imaging method is to use a substance with attached radioactivity and inject it into patients. This substance is taken up preferentially by cancer cells and can then be photographed. A novel compact gamma imaging system, developed by General Electric, can be used to photograph a radioactive substance taken up by breast cancer cells. This new camera is positioned close to the breast so that, in most cases, all breast tissue is within 5 cm of the detector. Most recently, dual detector systems have been introduced, further reducing the lesion to detector distance and improving the image. This modern technology, called Molecular Breast Imaging (MBI), has the potential to detect breast cancer in difficult situations (e.g. dense breasts), to measure the response of breast tumors to treatment, to measure blood flow within tumors, and to determine whether drugs can penetrate into tumors.
Dr. G. Pond, an OCOG biostatistician, lead the multidisciplinary team (J Valiant, head of the Centre for Probe Development and Commercialization (CPDC), at McMaster; K Gulenchyn, head of Nuclear Medicine at HHS; and L. Bordeleau, medical oncologist at the JCC who specializes in hereditary cancers) in the THORN trial. In the THORN trial the goal was to study the feasibility and safety of the MBI Gamma Camera, and to explore the ability of this camera to detect early breast cancer in women at high risk of developing breast cancer (e.g. BRCA1/2 carriers). These women presently undergo annual MRI and as part of the study, underwent MRI and MBI at baseline and again at 12 months. 42 women participated in this study.
