Bone scintigraphy and the added value of SPECT (single photon emission tomography) in detecting skeletal lesions

Skeletal metastases are one of the major clinical problems for the oncologi st. Over the last several decades bone scintigraphy has been used extensive ly in detecting bone involvement since it can provide information about dis ease location, prognosis and the effectiveness of treatment. Bone scan offe rs the advantage of total body examination, and images bone lesions earlier than other techniques. In this paper the main clinical problems related to the most common applications of bone scan in breast, prostate, lung cancer and other tumours are discussed. The experience carried out at the Nationa l Cancer Institute of Milan by using bone SPECT to detect single bone metas tases is reported. One hundred and eighteen patients with bone metastases ( from different tumour types: breast, lung, prostate, lymphomas, etc,) were studied by planar scintigraphy, SPECT and other radiological modalities (CT , MRT or X-rays). The overall performances of bone SPECT were sensitivity: 90.5% (19/21), specificity 92.8% (90/97), positive predictive value 73% (19 /26), negative predictive value 97.8% (90/92), accuracy 92.4% (109/118). Co nsidering breast cancer, the most frequent pathology in our series, and the lumbar spinal tract, the most common skeletal segment involved, the figure s of merit of SPECT were: sensitivity 100% (4/4), specificity 95.3% (41/43) , positive predictive value 66.7% (4/6), negative predictive value 100% (41 /41), accuracy 95.7% (45/47). In conclusion bone SPECT showed very good per formances, in particular improving the predictive value of planar scan in t he diagnosis of vertebral metastases.