Comparison of MRI and Histopathology with regard to Intramedullary Extent of Disease in Bone Sarcomas

Positron emission tomography-magnetic resonance imaging as a research tool in musculoskeletal conditions

Compared to positron emission tomography/computed tomography (PET/CT), the uptake of PET- magnetic resonance imaging (MRI) has been slow, even more so in clinical practice compared to the (pre-)clinical research setting. However, for applications in musculoskeletal (MSK) research, the combination of PET and MRI into a single modality offers attractive advantages over other imaging modalities. Most importantly, MRI has exquisite soft-tissue detail without the use of contrast agents or ionizing radiation, superior bone marrow visualization, and an extensive spectrum of distinct multiparametric assessment methods. In the preclinical setting, the introduction of PET inserts for small-animal MRI machines has proven to be a successful concept in bringing this technology to the lab. Initial hurdles in quantification have been mainly overcome in this setting. In parallel, a promising range of radiochemistry techniques has been developed to create multimodality probes that offer the possibility of simultaneously querying different metabolic pathways. Not only will these applications help in elucidating disease mechanisms, but they can also facilitate drug development. The clinical applications of PET/MRI in MSK are still limited, but encouraging initial results with novel radiotracers suggest a high potential for use in various MSK conditions, including osteoarthritis, rheumatoid arthritis, ankylosing spondylitis and inflammation and infection. Further innovations will be required to bring down the cost of PET/MRI to justify a broader clinical implementation, and remaining issues with quality control and standardization also need to be addressed. Nevertheless, PET/MRI is a powerful platform for MSK research with distinct qualities that are not offered by other techniques.

Functional and Oncological Outcomes of Multidisciplinary Management of Ewing's Sarcoma of Clavicle: A Single-Center Experience

Objectives Ewing's sarcoma is best treated using a multidisciplinary approach. We discuss the functional and oncological outcomes of clavicular Ewing's sarcoma which has been sparsely reported in literature. Materials and Methods We retrospectively evaluated patients who underwent resections for Ewing's sarcoma of clavicle from January 2002 to December 2017. The study end points were locoregional recurrence free survival (LRFS), disease-free survival (DFS), and overall survival (OS) at 3 and 5 years, and functional outcomes measured by Musculoskeletal Tumor Society (MSTS) scores. Statistical Analysis The LRFS, DFS, and OS were calculated and analyzed using the Kaplan-Meier method and log-rank test. Results Data of 21 patients (male: 12, female: 9) was analyzed with a mean age [range] of 15.3 [6-40] years. Total clavicle excision was done in 62% (13 of 21) while 38% ( n = 8) had partial resections. Radiotherapy was administered in 15 patients (71.5%). At a median follow-up of 42 months (range: 7-198), data of 20 patients was available for follow-up. Ten patients died (due to disease: nine, other reasons: One), eight are disease free and alive, one had metastasectomy on recurrence and is disease free and, one patient is alive with disease and on palliative chemotherapy. The LRFS, DFS, and OS were 95, 59, 65% and 95, 47, 59% at 3 and 5 years, respectively. The functional evaluation done for nine patients who are free of disease showed a mean MSTS score of 29 (range: 27-30; total clavicle excision: 28.5, partial clavicle excision: 29.5). Conclusion Patients with Ewing's sarcoma of the clavicle who underwent resection without reconstruction have acceptable local control rates and excellent functional outcomes.

Staging and Classification of Primary Musculoskeletal Bone and Soft Tissue Tumors Based on the 2020 WHO Update, From the AJR Special Series on Cancer Staging

Staging of primary musculoskeletal bone and soft tissue tumors is most commonly performed using the AJCC and the Enneking or Musculoskeletal Tumor Society (MSTS) staging systems. Radiologic imaging is integral in achieving adequate musculoskeletal neoplastic staging by defining lesion extent and identifying regional lymph node involvement and distant metastatic disease. Additional important features in surgical planning, though not distinct components of the staging systems, include cortical involvement, joint invasion, and neurovascular encasement; these features are optimally evaluated by MRI. In 2020, the WHO updated the classification of primary musculoskeletal tumors of soft tissue and bone. The update reflects the continued explosion in identification of novel gene alterations in many bone and soft tissue neoplasms. This has resulted in newly designated lesions, reclassification of lesion categories, and improved specificity of diagnosis. While radiologists do not need to have a comprehensive knowledge of the pathologic details, a broad working understanding of the most recent update is important to aid accurate and timely diagnosis given that histologic grading is a component of all staging systems. By approaching primary musculoskeletal neoplasms through a multidisciplinary approach with colleagues in pathology, orthopedic oncology, radiation oncology, and medical oncology, radiologists may promote improved diagnosis, treatment, and outcomes.

Imaging of Bone Sarcomas and Soft-Tissue Sarcomas

BACKGROUND

 In the diagnosis of bone and soft-tissue sarcomas, the continuous advancement of various imaging modalities has improved the detection of small lesions, surgical planning, assessment of chemotherapeutic effects, and, importantly, guidance for surgery or biopsy.

METHOD

 This review was composed based on a PubMed literature search for the terms "bone sarcoma," "bone cancer" and "soft tissue sarcoma," "imaging," "magnetic resonance imaging", "computed tomography", "ultrasound", "radiography", and "radiomics" covering the publication period 2005-2020.

RESULTS AND CONCLUSION

 As discussed in this review, radiography, ultrasound, CT, and MRI all play key roles in the imaging evaluation of bone and soft-tissue sarcomas. In daily practice, advanced MRI techniques complement standard MRI but remain underused, as they are considered time-consuming, technically challenging, and not reliable enough to replace biopsy and histology. PET/MRI and radiomics have shown promise regarding the imaging of sarcomas in the future.

KEY POINTS

  · Radiographs remain crucial in diagnostic imaging algorithms for sarcomas.. · US is an initial imaging study for the evaluation of superficial soft-tissue tumors.. · The role of CT continues to evolve as new techniques emerge.. · MRI allows the noninvasive evaluation of soft-tissue, osseous, and articular structures.. · Machine learning methods could improve personalized selection of therapy for patients with sarcoma..

CITATION FORMAT

· Igrec J, Fuchsjäger MH. Imaging of Bone and Soft-Tissue Sarcomas. Fortschr Röntgenstr 2021; 193: 1171 - 1182.

Assessment of Resection Margins in Bone Tumor Surgery

Limb salvage surgery is now the preferred procedure for bone tumor surgery. To decrease the risk of local recurrence, it is crucial to obtain adequate resection margins. The obtained margins must be evaluated postoperatively because they influence what treatment is given subsequently when margins are not adequate (e.g., surgical revision and radiotherapy). The study aims to evaluate margin assessment of tumor specimen by MRI compared to conventional histology (to establish the viability of using MRI) and assess the accuracy of a patient-specific instrument when narrow margins were aimed. The resection margins in 12 consecutive patients that were operated on for bone tumor resection were prospectively analyzed using three methods: MRI of the resection specimen, macroscopic evaluation of specimen slices, and microscopic pathological evaluation. The assessments were qualitative (R0, R1, and R2) and quantitative (distance in mm). MRI, macroscopic, and microscopic margins generated similar results for both the qualitative (all resections were R0) and quantitative assessments. The median error in safe margins was 2 mm with a surgical guide (PSI) and 5 mm without a surgical guide. Local recurrences were not detected after a mean follow-up period of 3.7 years (range, 2.1-5 years); however, four patients died during the study. In conclusion, MRI is a valuable tool for assessing safe margins. When specimens are not available for pathological assessment (e.g., extracorporeally irradiated autograft or autoclaved autograft), MRI could be used to evaluate margins. In particular, when tumor volume is high, MRI could also help to focus the pathological examination on areas of concern.