The role of bone SPET study in diagnosis of single vertebral metastases

The spine is the preferential site of metastases from several neoplasms. In the past years whole body bone scan (BS) with 99mTc-diphosphonates has been considered the first choice in detecting the skeletal involvement. However the presence of vertebral non-neoplastic pathology in oncologic patients can cause several false positive results and this increases the difficulty in defining the etiology of a focal uptake. Nowadays, technological development has provided new gamma cameras, which are able to perform tomographic acquisition (single photon emission tomography, SPET). This technique allows one to better define the anatomical location of the areas of increased uptake. In our study, 81 cancer patients, with suspected single skeletal metastases not defined by BS, were studied by SPET. The skeletal involvement was confirmed during at least 12 months follow up by means of clinical, radiological and nuclear medicine examinations. The overall malignant bone alterations were 14 while the benign ones were 67. The performances of SPET were: diagnostic sensitivity 92.8% (13/14), specificity 92.5% (62/67) positive predictive value 72.2% (13/18), negative predictive value 98.4% (62/63), accuracy 92.6% (75/81). Our conclusion is that bone SPET proved to be a very reliable tool in differentiating benign disease from metastatic involvement.