Chest wall recurrence of breast cancer demonstrated on 99mTc-MIBI scintimammography

Abstract

The mastectomy site is usually assessed by clinical examination and ultrasonography for recurrence of breast cancer, although post-surgical and radiotherapy changes limit the accuracy of these methods. MRI has been used successfully but it remains an expensive modality and may not be readily available. Scintimammography is an alternative method which has the advantage of not being affected by post-operative morphological changes. To evaluate the usefulness of planar Tc-MIBI scintimammography and supine Tc-MIBI SPECT in the detection of chest wall recurrence post-mastectomy. The study population comprised of 26 patients (mean age, 47.15 years; median age 47 years; age range, 22-77 years) with suspected chest wall recurrence of breast cancer on clinical examination. All patients received a 740-1000 MBq bolus i.v. injection of Tc-MIBI preferably in the pedal vein. At 5-10 min post-injection planar images were obtained in the prone lateral and supine anterior positions using a double-head gamma camera. After planar imaging supine SPECT was performed (64 projections, 64x64 matrix, 30 s.frame). MIBI uptake was scored as follows: 1 = normal uptake (compared with contralateral side); 2 = focal low uptake (equivocal); and 3 = focal high uptake (positive). All patients underwent excision biopsy or FNAC for tissue diagnosis. FNAC was considered sufficient if unequivocally positive. For the 26 patients, planar scintimammography was found true positive in 14 and true negative in seven. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy were 78%, 87.5%, 93%, 64% and 81%, respectively (P<0.001). SPECT showed a significantly higher overall sensitivity than planar imaging (89% vs. 78%; P<0.001). SPECT and planar imaging showed the same specificity (87.5%). SPECT showed a significantly higher negative predictive value and accuracy than planar imaging (78% vs. 64% and 88% vs. 81%, respectively; P<0.05). Scintimammography is a reliable diagnostic tool and appears accurate in the detection of chest wall recurrence. SPECT shows high positive predictive value and aids in the diagnosis of the chest wall recurrence with greater confidence.