A related video is at www.youtube.com/InternalMedicineNews
CHICAGO — Breast-specific gamma imaging can detect additional breast cancers missed by mammography and physical examination in women with newly diagnosed breast cancer.
In a retrospective study in 159 women with at least one biopsy-proven cancer, follow-up breast-specific gamma imaging (BSGI) identified clinically and mammographically occult cancer in 14 of 45 lesions. Nine of the 14 occult cancers were in the same breast as the index lesion, Dr. Rachel F. Brem said at the annual meeting of the Radiological Society of North America.
“Surgical management is going to be dependent on whether there is one breast cancer or more than one cancer in that breast or in the other breast,” Dr. Brem told reporters at a press briefing. In at least one case, the discovery of an additional lesion meant that a mastectomy had to be performed rather than a lumpectomy as originally planned.
Unlike other adjunct imaging modalities such as mammography and ultrasound that image the physical structure of the breast, BSGI is a form of molecular imaging that captures the cellular functioning of the breast tissue through radiotracer uptake. Cancerous cells show increased radiotracer uptake because of their higher metabolic activity.
Previous studies using BSGI have shown that the technique improves cancer detection in high-risk women and can detect the earliest breast cancers, even those as small as 1 mm, said Dr. Brem, director of breast imaging and intervention, George Washington University, Washington.
Half of the cancers detected in the current study were less than 1 cm in diameter. They ranged in size from 0.1 cm to 3.6 cm, with a mean of 1.16 cm.
When asked by reporters how BSGI compares with other new molecular imaging modalities such as positron emission mammography (PEM), Dr. Brem said that the radiation dose with BSGI is at most half that of PEM and that BSGI can be performed at a “fraction of the cost” of PEM. A BSGI unit costs about $250,000 and the radiotracer costs about $75 per imaging study.
PEM also is difficult to perform in women with diabetes, as it utilizes radiated sugar, and it is approved for use only in women with known cancer, she said.
A BSGI study takes about 40 minutes and uses technetium 99-sestamibi, a radiotracer used for more than 15 years in cardiac stress testing. More than 80,000 women in the United States have been imaged with BSGI since it was approved in 1999. It is available in about 50 centers in the United States, Dr. Brem said.
The women in the study ranged in age from 29 to 93 years (mean 54 years); 12% had a personal history of cancer and 43% had a first-degree relative who had had breast cancer. Of note, 73% of the women had dense breasts.
Breast density is a significant limitation of mammographic breast cancer detection and is a strong independent risk factor for the development of breast cancer, said Dr. Brem, also a professor of radiology at the university. A recent study showed a four-to sixfold increased risk of detected breast cancer in women with mammographically dense breasts (N. Engl. J. Med. 2007;356:227-36).
Dr. Brem disclosed that she owned stock in and is a board member of Dilon Technologies, which makes the BSGI unit. She also has served on the board of directors for iCAD Inc. and was a consultant for Orbotech.
This image of a small cancer (dark circle) was obtained using BSGI. Radiological Society of North America