Characterization Of Solitary Lesions In The Extremities In Patients With Known Cancer:Contribution Of ^99mTc-MDP SPECT/CT

Background In recent years,with the social and economic development,lifestyle changes,life extension,cancer incidence and mortality significantly increased,has become a threat to human life and health of the second major disease.Bone is the most common site of malignant tumor metastasis,and early detection of metastases has an important influence on patients’ treatment decisions.According to the latest eighth edition of TNM staging system for lung cancer,there were significant differences in survival between patients with single and multiple bone metastases.Although extremities are not the common site for the solitary bone metastasis,early detection and diagnosis and active treatment can effectively improve the quality of life of patients.Objective Evaluate the contribution of single-photon emission computed tomography/computed tomography(SPECT/CT)in differentiating bone metastases from benign bone lesions.Methods This study was a retrospective review of patients with known cancer who underwent Whole-body Bone Scan(WBS)from January 2015 to December 2018 andshowed solitary lesions with 99mTc-MDP uptake in the extremities and then underwent SPECT/CT for further diagnosis.SPECT/CT images were independently interpreted by two experienced nuclear medicine physicians,and analyzed localization and degree of osteoblastic activity of lesions.The standard diagnostic criterion was based on biopsy or radiologic follow-up over at least 12 months.The sensitivity,accuracy,positive predictive value and negative predictive value of WBS and SPECT/CT imaging were calculated respectively.Inter-reviewer agreement was assessed by using weighted k statistics.Results A total of 124 patients were included in the study,25 bone metastases and 99(73.26%)benign lesions were diagnosed.The most common benign bone disease was a benign bone tumor or tumor like disease(31.75%,28/99),followed by degeneration(27.11%,24/78).The majority(65%,17/28)of benign bone tumors or tumor like disease were enchondromas.In the proximal and distal extremities,the most common disease was degeneration.In the diaphysis extremities,the most common disease was bone metastases.The area under ROC curve of WBS and SPECT/CT of reviewer 1 were 0.677 and 0.981.The area under ROC curve of WBS and SPECT/CT of reviewer 2 were 0.731 and 0.927.The weighted kappa score for inter-reviewer agreement of WBS and SPECT/CT were 0.731 and 0.927 respectively,showed good agreement.Conclusion When solitary disease of the extremities is detected by WBS in patients with known cancer,benign lesions may be more common than malignant lesions.The most common benign bone disease was a benign bone tumor(especially enchondromas),followed by degeneration.Bone metastases were found more frequently in the diaphysis of the extremities,and difficult to differentiate from benign bone lesions.SPECT/CT not only provides information about comprehensive function and anatomical structure but also helpful for the diagnosis of equivocal lesions of the extremities.