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A new study finds that ultrasound, also called
sonography, may be more accurate than mammography at
detecting breast cancer in young women who have symptoms of the disease. This may be the
case, researchers say, because younger women tend to have dense breast tissue, which can
eclipse cancer on mammogram films. However, the researchers do not advocate ultrasound as
a screening tool. In the study, it was effective on women who already had cancer
symptoms, such as breast lumps. The study could be valuable to radiologists who
investigate breast abnormalities in younger women.
Breast ultrasound is frequently used to evaluate breast abnormalities that are found
with screening or diagnostic mammography or during a physician performed clinical breast
exam. Ultrasound is excellent at imaging cysts—round, fluid-filled, pockets inside
the breast—and can often quickly determine if a suspicious area is in fact a cyst
(always non-cancerous) or an increased density of solid tissue (dense mass) which may
require a biopsy to determine if it is cancerous.
To compare ultrasound and mammography in women with symptoms of breast cancer, Dr.
Nehmat Houssami of the University of Sydney, Australia and colleagues enrolled 240 women
from a breast clinic, all of whom were found to have breast cancer. The researchers then
enrolled an additional 240 women from the clinic who were found not to have breast cancer
despite having breast lumps or similar symptoms. All of the women were examined with both
ultrasound and mammography.
The results showed that, overall, there was not a statistically significant difference
in the effectiveness of ultrasound versus mammography for detecting breast cancer. Breast
cancer was accurately found with ultrasound in 81.7% of the women, compared to 75.8% with
mammography.
However, Dr. Houssami and his colleagues did find ultrasound to be more accurate at
detecting breast cancer in younger women (45 years of age or younger). Among these women,
ultrasound accurately detected 84.9% of breast cancers, compared to 71.7% of cases
detected with mammography alone. This is likely to due to the fact that younger women tend
to have more dense breast cancer, which makes it more difficult to spot breast cancer on a
mammogram film.
Based on the finding of the study, the researchers conclude that ultrasound may be more
effective than mammography at detecting breast cancer in younger women with cancer
symptoms and may be considered as the initial test for these women. (However, in the
majority of cases, women who have symptoms of breast cancer are referred for both
ultrasound and mammography).
While ultrasound has excellent contrast resolution, which may be particularly useful in
younger women with breast symptoms, it has other limitations which prevent it from
becoming a widespread screening tool for breast cancer. For example, ultrasound
does not have good spatial resolution like mammography, and therefore cannot provide as
much detail as a mammogram image. Ultrasound is also unable to image microcalcifications,
tiny calcium deposits that are often the first indication of breast cancer. Mammography,
on the other hand, is excellent at imaging calcifications. Ultrasound may be able to
detect macrocalcifications (larger calcium deposits) in some cases.
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