Incremental Value of Single-photon Emission Computed Tomography-computed Tomography for Characterization of Skeletal Lesions in Breast Cancer Patients

The incremental value of single-photon emission computed tomography-computed tomography (SPECT-CT) over planar bone scintigraphy and SPECT in detecting skeletal lesions in breast cancer patients and its effect on patient management is assessed in this study. This is a prospective study which was conducted over 1-year duration. Whole-body planar scintigraphy, SPECT, and SPECT-CT were performed in 85 breast cancer patients with total of 128 lesions. Correlative imaging and clinical follow-up was used as the reference standard. McNemar's multistep analysis was performed for each patient and each lesion. On patient-wise analysis, 47 patients had equivocal diagnosis on planar bone scintigraphy, 28 on SPECT, and eight on SPECT-CT. On lesion-wise analysis, there were 72 equivocal lesions on planar bone scintigraphy, 48 on SPECT, and 15 on SPECT-CT. Overall, SPECT-CT resulted in a significant reduction in the proportion of equivocal diagnosis on both patient-wise (P < 0.004) and lesion-wise basis (P < 0.004), irrespective of the skeletal region involved. The sensitivity on a per-patient basis was 43%, 58%, and 78% for planar bone scintigraphy, SPECT, and SPECT-CT, respectively. Similarly, the specificity was 85%, 92%, and 94% for planar bone scintigraphy, SPECT, and SPECT-CT, respectively. Patient management was correctly altered in 32% of the patients based on SPECT-CT interpretation. Our data suggest that adding SPECT-CT to whole-body imaging significantly improves sensitivity and specificity in diagnosing bone metastases and significantly reduces the proportion of equivocal diagnosis in all regions of the skeleton. The most important outcome is derived from the accurate alteration in patient management clinically by down- and up-staging of patients and a more precise identification of metastatic extent.