6 October 2007: Breast Cancer Imaging Update
Mammography is the single most important imaging modality of the breast. It is an X-ray technique that has proven to be of great value in screening for breast cancer. Empirical evidence shows that it can reduce mortality by at least 26%.
However, in case of high breast density in young women and some older women, a tumour may not be easily seen on the mammogram because the tumor often appears as a white shadow, the same image as the dense breast tissue. It is like trying to pick out a piece of white paper pasted on a white wall. Therefore, some additional techniques have to be deployed.
A new X-ray technique called Tomosynthesis will be coming out next year. With one single exposure of the breast, one can obtain over 60 very thin images of the breast. This will allow very small tumours within the dense breast to be picked up. This modality shows great promise.
Ultrasound does not involve X-rays and is widely available. It can pick out benign and malignant tumours. However, it may not pick up DCIS or malignant tumours that are very small. Ultrasound is therefore a complementary study to mammography. A new software program called “Elasticity” is available on some new ultrasound machines. There is a difference in elasticity between benign and malignant tumours.
MRI scan is now routinely used to complement mammography and ultrasound. MRI of the breast has a sensitivity of near 100% for invasive breast carcinoma and over 95% for breast carcinoma. It does not have any ionizing radiation and is done within 20 to 30 minutes. The indications for breast MRI include screening for patients who have BRCA-1 or BRCA-2 genes, for patients with positive personal history or positive family history or patients who have had silicone or gel injection into the breasts. In the diagnostic setting, MRI is useful for patients who have a questionable abnormal finding on mammogram or ultrasound. Sometimes, there is a palpable abnormality and the ultrasound and mammogram are normal or the patient had prior surgery and the margins of the surgery are positive. In the patient with known breast carcinoma, MRI is used to see the full extent of tumour. A second tumour in the same breast can occur up to 6% to 34% of the time. Therefore, it is important to delineate the full extent of tumour prior to surgery. A tumour may also occur in the opposite breast in 3.8% to 5.4% of the time. Therefore, the breast that does not have the known carcinoma should also be scanned. MRI is also used increasingly for monitoring patients who are undergoing neoadjuvant chemotherapy prior to surgery.
In conclusion, there are many new imaging strategies for a woman with breast cancer and all these modalities are complementary.
With the whole Body MRI scanner, MRI imaging for the whole body is now available. It can be used to stage patients with breast cancer and monitor their treatments. Since many breast cancer patients are young, MRI is attractive as it does not involve any radiation on the body.
Dr. Gladys Goh Lo, M.D., Diplomate, American Board of Radiology, MCPS (Manitoba), FHKAM (Rad) FHKCR, CT Body Fellowship at Stanford University Medical Center. Over 21 years of Private Practice in USA and Hong Kong. Specialty is Body Imaging. Current interests are Breast and Cardiac Imaging