Should SPECT-CT replace SPECT for the evaluation of equivocal bone scan lesions in patients with underlying malignancies?

Background: Bone scintigraphy is used extensively in evaluating metastatic disease. There are currently no clear recommendations for the use of single photon emission computed tomography (SPECT)/CT in metastatic bone disease. Given its limited availability there is a need to identify the clinical indications for which SPECT/CT is clearly beneficial in influencing patient care and outcome.

Methods: Forty-two patients with equivocal lesions on planar scintigraphy were recruited and underwent SPECT/CT imaging. On reading of SPECT alone and then SPECT/CT, lesions were classified as malignant, benign or equivocal. Follow-up clinical information, radiological studies and/or bone scans were used as a gold standard. SPECT and SPECT/CT were compared in terms of the number of equivocal findings and accuracy on a patient-wise and lesion-wise basis.

Results: Forty-two patients with 189 skeletal lesions were examined. There was a diverse variety of primary tumours, with the majority being breast (n=22) and prostate cancer (n=8). SPECT/CT resulted in a significant reduction in the proportion of patients (48-14%, P=0.0015) and lesions (31-9%, P<0.0001) with equivocal findings. The overall accuracy of SPECT/CT was significantly higher on both a patient-wise (52-79%, P=0.0026) and lesion-wise basis (67-92%, P<0.0001).

Conclusions: SPECT/CT significantly outperforms SPECT alone for the interpretation of skeletal lesions in patients undergoing bone scanning for metastases. When available SPECT/CT is indicated in patients in whom correct classification of equivocal lesions is expected to alter the patient's management.