Oncology

Differentiating between low-grade chondrosarcoma and enchondroma

Distinguishing low-grade chondrosarcoma from enchondroma remains a dilemma in orthopaedic oncology. What is an enchondroma and what is a low-grade chondrosarcoma? Researchers in Madrid (Spain) have shed some light on what might be useful clinical and radiological criteria to guide treatment. These orthopaedic oncologists report their experience of 133 patients with cartilaginous tumours that could theoretically fall into either category, presenting in the appendicular skeleton. All patients were followed prospectively. Features including clinical history, and radiological and nuclear imaging, along with biopsy results, were collected, and the authors also categorised patients on an aggressiveness scale. Patients were followed clinically and radiologically, and their characteristics compared with the eventual outcomes.¹ The authors were able to identify that pain on palpation, cortical erosion on cross-sectional imaging and Tc99 bone scan uptake above that at the iliac crest were all statistically significantly associated with the likelihood of malignant tumours. Interestingly, the clinical judgement showed a sensitivity of 73.5% and specificity of 94.1%. This paper goes some way towards identifying helpful criteria for diagnosis, and certainly outlines some important factors that can be used to arouse suspicion.

PET-CT in chondroma and chondrosarcoma

On the same theme, an oncology team in São Paulo (Brazil) evaluate the potential for use of positron emission tomography–computed tomography (PET-CT) in differentiating between chondroma and chondrosarcoma.² PET-CT is a maturing technology that is starting to find its feet, and, although clearly not suitable for all applications, is finding its niche in a number of diagnostic situations. The study team reports their experience of PET-CT as a diagnostic modality in 36 patients with suspected chondrosarcoma over a period of six years. The authors identified a threshold of SUVmax of 2.0 as the threshold for exploring the potential for malignancy. Patients above the threshold underwent surgery; those below, observation. Their study population included 17 below-threshold patients diagnosed as chondromas and 19 diagnosed as likely chondrosarcomas with SUVmax values over the threshold. Although the authors do examine nicely the potential benefits of SUVmax and undertake some ROC analysis, not all patients underwent biopsy, and follow-up is rather limited. While this paper adds extra sophistication, it is potentially less clinically useful than the previous report!

Denosumab: great until you stop taking it

Denosumab has become a bit of a wonder drug in orthopaedic oncology, with widely reported trials demonstrating it to be as effective as almost any other treatment in the management of giant cell tumours of bone (GCT). Denosumab works through direct inhibition of the bone resorption pathways mediated by the RANK receptor and its ligand. In a small prospective series from Toronto (Canada), the research team investigated the outcomes of 20 patients managed with denosumab to downgrade tumours prior to resection.³ The patients in this study received at least six months of neo-adjuvant denosumab and then joint-preserving surgery. Denosumab was effective in all patients in resolving pain, and intralesional resection was possible in 18 of 20 cases. The patients were followed up to 30 months, with local recurrence occurring in three patients within this relatively short time period. This is a small series, confirming other work showing that denosumab works brilliantly to downstage GCT and allows for conservative surgery; however, rates of local recurrence when denosumab is stopped are worrying.

Is cement augmentation helpful in intramedullary nailing for mets?

Nailing sufficient for pathological fractures

The patella in distal femoral arthroplasty?

Does size reliably predict malignancy in soft tissue tumours?

In a retrospective study from Innsbruck (Austria), the authors set out to examine whether size is a predictive marker of tumour malignancy in soft tissue masses (STM), and furthermore if the ratio of width and length of a STM reflects tumour biology more accurately.⁷ The research team performed measurements of maximal lesion size and perpendicular diameter on MRI and ultrasonography studies of 212 patients, all with a histologically verified diagnosis. Size alone was a weak predictor of malignancy in STMs (sensitivity 68.8%, specificity 50.3%), whereas the ratio showed better discriminatory power, with greater separation between benign and malignant entities (sensitivity 83.6%, specificity 53.6%). A weighted combination of size, age and ratio improved the diagnostic power of this simple test (sensitivity 77%, specificity 80%). The authors of this study have demonstrated that malignant tumours have a significantly higher length:width ratio – i.e. they grow in a more spherical fashion – than benign lesions, and crucially also intermediate lesions. This is a simple, easy to digest paper with an important clinical message: essentially, when combined with some simple demographics, the sphericity of the lesion can be used as a reasonable predictor of the likelihood of malignancy.

Surgical staging of osteosarcoma under the spotlight

Although widely used throughout orthopaedics, classifications can sometimes be simply an end unto themselves with no clinical or surgical relevance. We are always slightly hesitant when a ‘new classification’ paper crosses our desks at 360. The journals are full of self-serving classifications with little visible benefit over previous efforts at classification. In orthopaedic oncology, however, classifications are hugely important, and understanding the prognosis of specific lesions is key to the patient and medical team in order to have an idea as to the likely success of any treatment. So any new classification should add utility to the decision making. The Birmingham (UK) classification is devised on the basis of two parts: the response to chemotherapy (good response = ⩾ 90% necrosis; poor response = < 90% necrosis) and margins (< 2 mm or ⩾ 2 mm).⁸ The intention was to improve upon the current ‘gold standard’ of surgical margins. Their retrospective study applies their newly devised classification to establish how useful it might be in clinical practice. The study team included 389 patients, all of whom had high-grade conventional osteosarcoma without metastasis. Patients were all treated with pre-operative chemotherapy and surgical resection. All the available covariates were modeled using univariate and then multivariate modeling. This yielded the ‘Birmingham’ classification based on chemotherapy response and soft-tissue resection margins. The authors established that intralesional resection (hazard ratio 10) and pre-operative chemotherapy (hazard ratio 3.8) were both associated with recurrence in this series, which, when independently tested, did provide a better prediction for local recurrence than the musculoskeletal tumor society (MSTS) criteria. In addition, the Birmingham classification was discriminatory for survival between subcategories, which the MSTS system was not.

UK guidelines for the management of bone sarcomas

And finally we would draw the attention of 360 readers to the British Sarcoma Group (London, UK) guidelines, which are newly updated this month from their previous 2010 incarnation.⁹ The new guidelines incorporate recent recommendations from European and UK bodies and essentially boil down to the recommendation that all patients with bone pain or a palpable mass should be appraised thoroughly with appropriate clinical review and imaging. A valuable read for anybody with a general orthopaedic practice who is likely to come into contact with bone sarcomas.