Tc-99m-methoxy isobutyl isonitrile scintimammography: imaging postexcision biopsy for residual and multifocal breast tumor.

OBJECTIVES: The interpretation of mammogram in a postsurgical breast can be extremely complex and difficult because masses, calcifications, and architectural distortion can mimic cancer. Scintimammography has been proposed because it is not affected by these morphological changes and can potentially be used in patients after excision biopsy to assess any residual tumor, other foci of disease (multifocal disease).

MATERIALS AND METHODS: The population comprised of 21 patients (mean age: 47.80 years, median age: 50 years, and age range: 26-77 years) evaluated for suspected residual breast cancer after excision biopsy. All patients received a 740-1000 MBq bolus IV injection of Tc-99m-methoxy isobutyl isonitrile (MIBI) preferably in pedal vein. At 5-10 min after injection, planar images were obtained in prone lateral and supine anterior positions using dual head gamma camera. MIBI uptake was scored as follows: 1 - as normal uptake (compared with contralateral side), 2 - focal low-intense uptake (equivocal), and 3 - focal high-intense uptake (positive). All patients had histopathology for tissue diagnosis.

RESULTS: Of the 21 patients evaluated, scintimammography planar was found true positive in 13 and true negative in six. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 92.85, 85.71, 92.85, 85.71, and 90.47%, respectively (P<0.001). Scintimammography detected 2/2 multifocal disease.

CONCLUSION: In patients after excision biopsy, scintimammography with Tc-99m-MIBI is valuable in assessing residual or multifocal disease. Scintimammography has high positive predictive value and may influence planning further management.