Abstract
BackgroundRadiation-induced insufficiency fractures (IF) is frequently occult without fracture line, which may be mistaken as metastasis. Quantitative apparent diffusion coefficient (ADC) shows potential value for characterization of benign and malignant bone marrow diseases. The purpose of this study was to develop a nomogram based on multi-parametric ADCs in the differntiation of occult IF from bone metastasis after radiotherapy (RT) for cervical cancer.MethodsThis study included forty-seven patients with cervical cancer that showed emerging new bone lesions in RT field during the follow-up. Multi-parametric quantitative ADC values were measured for each lesion by manually setting region of interests (ROIs) on ADC maps, and the ROIs were copied to adjacent normal muscle and bone marrow. Six parameters were calculated, including ADCmean, ADCmin, ADCmax, ADCstd, ADCmean ratio (lesion/normal bone) and ADCmean ratio (lesion/muscle). For univariate analysis, receiver operating characteristic curve (ROC) analysis was performed to assess the performance. For combined diagnosis, a nomogram model was developed by using a multivariate logistic regression analysis.ResultsA total of 75 bone lesions were identified, including 48 occult IFs and 27 bone metastases. There were significant differences in the six ADC parameters between occult IFs and bone metastases (p < 0.05), the ADC ratio (lesion/ muscle) showed an optimal diagnostic efficacy, with an area under ROC (AUC) of 0.887, the sensitivity of 95.8%, the specificity of 81.5%, respectively. Regarding combined diagnosis, ADCstd and ADCmean ratio (lesion/muscle) were identified as independent factors and were selected to generate a nomogram model. The nomogram model showed a better performance, yielded an AUC of 0.92, the sensitivity of 91.7%, the specificity of 96.3%, positive predictive value (PPV) of 97.8% and negative predictive value (NPV) of 86.7%, respectively.ConclusionsMulti-parametric ADC values demonstrate potential value for differentiating occult IFs from bone metastasis, a nomogram based on the combination of ADCstd and ADCmean ratio (lesion/muscle) may provide an improved classification performance.
Highlights
Radiation-induced insufficiency fractures (IF) is frequently occult without fracture line, which may be mistaken as metastasis
Multi-parametric apparent diffusion coefficient (ADC) values demonstrate potential value for differentiating occult IFs from bone metastasis, a nomogram based on the combination of ADC standard deviation (ADCstd) and ADCmean ratio may provide an improved classification performance
Only qualitative Diffusion-weighted Imaging (DWI) assessment could not exclude the possibility that the T2 shine-through effect might have influence on the appearance of such images. Considering this limit, some studies have quantified the diffusion of marrow lesions by using the apparent diffusion coefficient (ADC) value, and the results indicated that ADC measurement was a reliable method in differentiating benign from malignant vertebral compression fractures [16, 17]
Summary
Radiation-induced insufficiency fractures (IF) is frequently occult without fracture line, which may be mistaken as metastasis. The purpose of this study was to develop a nomogram based on multi-parametric ADCs in the differntiation of occult IF from bone metastasis after radiotherapy (RT) for cervical cancer. Cervical cancer is one of the most common gynecologic malignant tumors worldwide. RTinduced IF is a relatively common complication for cervical cancer, previous studies showed that the 2-year cumulative incidences of IF after pelvic RT ranged from 14 to 36.9% [3,4,5,6,7]. MRI has limitation in the detection of fracture line, and abnormalities on MRI may sometimes be mistaken for metastatic diseases [5, 11, 12]. As for the diagnosis of occult IFs (without fracture line), it may be still challenging by using conventional MRI alone
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