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Association of MRI findings with intra-articular tumour extension
Lorenzo Deveza1, Mohammed A El Amine2, Anton S Becker2
1Department of Surgery, Memorial Sloan Kettering Cancer Center, New York, New York, USA.
Aims:
Treatment of high-grade limb bone sarcoma that invades a joint requires en bloc extra-articular excision. MRI can demonstrate joint invasion but is frequently inconclusive, and its predictive value is unknown. We evaluated the diagnostic accuracy of direct and indirect radiological signs of intra-articular tumour extension and the performance characteristics of MRI findings of intra-articular tumour extension.
Methods:
We performed a retrospective case-control study of patients who underwent extra-articular excision for sarcoma of the knee, hip, or shoulder from 1 June 2000 to 1 November 2020. Radiologists blinded to the pathology results evaluated preoperative MRI for three direct signs of joint invasion (capsular disruption, cortical breach, cartilage invasion) and indirect signs (e.g. joint effusion, synovial thickening). The discriminatory ability of MRI to detect intra-articular tumour extension was determined by receiver operating characteristic analysis.
Results:
Overall, 49 patients underwent extra-articular excision. The area under the curve (AUC) ranged from 0.65 to 0.76 for direct signs of joint invasion, and was 0.83 for all three combined. In all, 26 patients had only one to two direct signs of invasion, representing an equivocal result. In these patients, the AUC was 0.63 for joint effusion and 0.85 for synovial thickening. When direct signs and synovial thickening were combined, the AUC was 0.89.
Conclusion:
MRI provides excellent discrimination for determining intra-articular tumour extension when multiple direct signs of invasion are present. When MRI results are equivocal, assessment of synovial thickening increases MRI's discriminatory ability to predict intra-articular joint extension. These results should be interpreted in the context of the study's limitations. The inclusion of only extra-articular excisions enriched the sample for true positive cases. Direct signs likely varied with tumour histology and location. A larger, prospective study of periarticular bone sarcomas with spatial correlation of histological and radiological findings is needed to validate these results before their adoption in clinical practice.
Insights
Magnetic Resonance Imaging (MRI) effectively identifies intra-articular tumor extension in high-grade limb bone sarcomas when multiple direct invasion signs are present. For equivocal cases, assessing synovial thickening significantly improves diagnostic accuracy for joint involvement.
Area of Science:
- Orthopedic Oncology
- Diagnostic Imaging
- Radiology
Background:
- High-grade limb bone sarcomas invading joints necessitate en bloc extra-articular excision.
- Magnetic Resonance Imaging (MRI) is used to assess joint invasion, but its accuracy and predictive value for intra-articular tumor extension remain unclear.
Purpose of the Study:
- To evaluate the diagnostic accuracy of direct and indirect radiological signs of intra-articular tumor extension using MRI.
- To determine the performance characteristics of MRI findings in predicting intra-articular tumor extension.
Main Methods:
- A retrospective case-control study involved 49 patients undergoing extra-articular excision for knee, hip, or shoulder sarcoma.
- Radiologists assessed preoperative MRI for direct signs (capsular disruption, cortical breach, cartilage invasion) and indirect signs (effusion, synovial thickening) of joint invasion.
- Receiver operating characteristic analysis was used to determine MRI's discriminatory ability.
Main Results:
- The combined AUC for three direct signs of invasion was 0.83. For equivocal results (1-2 direct signs), the AUC for synovial thickening was 0.85.
- Combining direct signs with synovial thickening yielded an AUC of 0.89, indicating improved diagnostic performance.
- Individual direct signs had AUCs ranging from 0.65 to 0.76.
Conclusions:
- MRI demonstrates excellent discrimination for intra-articular tumor extension when multiple direct invasion signs are evident.
- In equivocal MRI findings, synovial thickening enhances the ability to predict intra-articular joint extension.
- Further prospective studies are needed to validate these findings for clinical practice.
