Scintimammography as an adjunctive breast imaging technology: an evidence-based analysis.
OBJECTIVE
X-ray mammography (XMM) represents the most useful screening tool in breast cancer detection, especially for patients over 50. Unfortunately, XMM is not reliable in the assessment of dense breast tissue found in approximately 25% of women younger than 50 years of age, or in differentiating scar tissue from a tumor. Currently, ultrasound (US) is being used as an adjunct to XMM, with the purpose of improving sensitivity and specificity of XMM in breast cancer detection. In an attempt to reduce the biopsy rate resulting from false positive tests, other adjunctive technologies are being explored, including scintimammography (SMM). A number of papers in the current literature suggest the high value of SMM in breast cancer detection. This evaluation addresses the clinical indications for and effectiveness of SMM in the diagnosis of breast cancer.


METHODS
SMM is a nuclear medicine imaging technique that uses radionuclides and has the ability to image malignant breast tumors. SMM requires the administration of a gamma-ray emitting radiopharmaceutical to the patient, and a camera for imaging the lesion. The most commonly used radiopharmaceutical for SMM is TC-99m-methoxy isobutyl isonitrile MIBI.


METHODS
In the 2003 Medical Advisory Secretariat assessment of SMM in the diagnosis of breast cancer, a structured search was used to identify English-language studies published between 1992 and October 2002. A meta-analysis was then conducted of the literature which compared the diagnostic value of SMM with US as the second line imaging technique. An updated search strategy was developed in order to identify all studies published from October 2002 to January 2007.


RESULTS
The results of the meta-analysis showed that SMM is as effective as US in differentiating benign and malignant breast lesions. However, there may be a role for SMM as a third line adjunctive technique in the evaluation of breast abnormalities, in particular where breast ultrasound examination is inconclusive because of dense breast tissue or architectural distortion resulting from previous surgery or radiation treatment. There is equivalence between SMM and US as a second line investigation for abnormal mammograms. As of October 2003 (to January 2007), there was no new comparative evidence on the diagnostic accuracy of SMM and US as a second line diagnostic tool.


CONCLUSIONS
No new comparative evidence on the diagnostic accuracy of SMM and US as a second line diagnostic tool has become available between October 2002 and January 2007. Therefore, the conclusions from the 2003 MAS review remain for this updated version in 2007. The results of the meta-analysis showed that SMM is as effective as US in differentiating benign and malignant breast lesions. However, there may be a role for SMM as a third line adjunctive technique in the evaluation of breast abnormalities, in particular where breast ultrasound examination is inconclusive because of dense breast tissue or architectural distortion resulting from previous surgery or radiation treatment. SMM is thought to be more accurate in patients with dense breasts, and as younger women are more likely to have dense breasts, a separate analysis specific to women under 50 years of age is needed.