Musculoskeletal pain as an indicator of occult malignancy. Yield of bone scintigraphy.

BACKGROUND: When musculoskeletal pain is persistent or out of proportion to clinical findings, diagnostic imaging is often used to evaluate for the presence of occult pathologic conditions. OBJECTIVE: To examine the efficacy of bone scintigraphy for identifying occult malignancy in such patients. METHODS: Bone scans of 491 patients with new or recurrent complaints of musculoskeletal pain and no previously known malignancy were retrospectively reviewed. The findings of each scan were classified into 1 of the following categories: (A) no evidence of malignancy; (B) equivocal (1-3 lesions of uncertain significance); or (C) probable metastatic disease (> 3 lesions without trauma or other benign explanation). All diagnoses of malignancy established within 6 months of the bone scan were then determined from review of radiological and clinical records. RESULTS: The distribution of scan interpretations was as follows: category A, 386 (79%); category B, 84 (17%); and category C, 21 (4%). Among the 181 patients younger than 50 years, 161 (89%) had category A and 20 (11%) had category B scans. Of the 310 patients aged 50 years or older, 226 (73%) had scans in category A, 64 (21%) in category B, and 21 (7%) in category C. Thirty patients (6%) had malignancy involving bone, 29 among those aged 50 years or older. In patients aged 50 years or older, 10 (16%) of 64 with equivocal scan findings (category B) and 19 (90%) of 21 with widespread abnormalities (category C) had malignancy involving bone. Initial radiographs of symptomatic sites showed lytic or blastic bone abnormalities suggestive of malignancy in 16 (59%) of the 29 older patients in whom this diagnosis was confirmed. CONCLUSIONS: In patients aged 50 years or older, the yield of bone scintigraphy for identification of occult malignancy (29/310; 9%) is sufficient to justify its use in the investigation of the cause of problematic bone or musculoskeletal symptoms.