Study finds mixed results for breast-specific gamma imaging

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Breast-specific gamma imaging (BSGI) has high sensitivity (96.4 percent) and moderate specificity (59.5 percent) helping detect breast cancers, according to a study published in the June issue of Radiology

Rachel F. Brem, MD, and colleagues from the departments of radiology and surgery at George Washington University in Washington, D.C., undertook the study to determine the sensitivity and specificity of BSGI for the detection of breast cancer by using pathologic results as the reference standard.

The researchers retrospectively reviewed 146 women (aged 32–98 years) undergoing BSGI and breast biopsy. The patients underwent BSGI with intravenous injection of 30 mCi (1110 MBq) of technetium 99-sestamibi and were imaged in craniocaudal and mediolateral oblique projections, the authors wrote.

The investigators assigned scores to study images, and classified the scores as positive (focal increased radiotracer uptake) or negative (no uptake or scattered heterogeneous physiologic uptake), and compared with biopsy results.

In 146 patients, 167 lesions were biopsied, of which 83 (16 ductal carcinoma in situ [DCIS] and 67 invasive cancers) were malignant, Brem and colleagues wrote. Of 84 nonmalignant lesions, 82 were benign and two showed atypical histologic results (one atypical lobular hyperplasia and one lobular carcinoma in situ), the researchers said.

Brem and colleages found that BSGI helped detect cancer in 80 of 83 malignant lesions with a sensitivity of 96.4 percent and correctly identified 50 of 84 nonmalignant lesions as negative for cancer with a specificity of 59.5 percent.

The positive predictive value for 80 of 114 malignant lesions with a BSGI examination with findings positive for cancer was 68.8 percent and the negative predictive value for 50 of 53 nonmalignant lesions was 94.3 percent, according to the researchers. The smallest invasive cancer and DCIS detected were both 1 mm.

The researchers noted that the BSGI helped detect occult cancer not visualized at mammography or ultrasonography in six patients.