Utility of bone scintigraphy in the evaluation of incidentally found osseous lesions

Objectives Incidental bone lesions are frequently noted on imaging and have a broad differential including benign and malignant processes. Bone scintigraphy (BS) has been used as part of the evaluation of solitary bone lesions to confirm the solitary nature of the findings. The purpose of this study was to evaluate the impact of BS ordered as part of the evaluation of incidentally detected bone lesions over 5 years at a Veterans Administration Medical Center.

Methods The indications for all BS performed at the Atlanta VAMC from 10/1/2008 to 9/30/2013 were reviewed along with the medical record to identify studies ordered as part of the work-up of incidentally found bone lesions. Patients with an active cancer diagnosis that could lead to bone metastases were excluded. Patient demographic data, lesion characteristics, BS interpretation, ordering physician management after bone scan, follow-up imaging, and subsequent cancer diagnoses were extracted from the medical record.

Results Of the 1712 BS during the study period, 171 (10%) fit the inclusion criteria. 15 of the 171 studies (9%) were interpreted as positive for metastatic disease; 4 patients had diffuse prostate cancer metastases and the other 11 had benign bone findings on follow-up. Findings were equivocal on 17 studies and cancer was diagnosed in none of these patients. Additionally, 26 patients (15%) had BS ordered for small lytic lesions which were all negative and more appropriate imaging was recommended for evaluation. Excluding the studies ordered for lytic lesions, 112 of 145 studies (77%) were interpreted as benign and cancer metastatic to the bones was diagnosed in this group in only one patient on follow-up. When positive and equivocal reads are grouped together, the specificity for identifying malignant disease was 80%, the PPV was 15%, and the NPV was 99%.

Conclusions A negative BS effectively identified the absence of a malignant etiology of the incidentally noted lesions obviating the need for further work-up in the majority of patients but a non-negative read resulted in 26 patients undergoing additional testing for benign lesions.