Metastatic tumours

A pathological fracture through a metastatic tumour may be the first clue that a patient has malignant disease. Indeed, the primary may never be found. In other cases metastatic bone disease occurs some time after treatment of the primary tumour. The commonest source of metastases in bone is tumours of the breast, the prostate and the kidney. In patients who are suspected of having metastases, a radioisotope bone scan may show up lesions which are nor yet symptomatic, and which may not even be visible on X-ray (Fig. 25.6).

The management of metastases is excision, where these are isolated and relatively slow growing. In the majority of cases radiotherapy and/or chemotherapy can be used to slow the rare of growth of the lesion. If more than 50 per cent of the cortex is eroded over more than 2 cm then it is considered that the long bones are liable to imminent pathological fracture. Under these circumstances it is best to stabilise the bone before it breaks. In the femur, the tibia or the humerus, a prophylactic intramedullary nail can be used to support the bone. Even where a fracture has already occurred, stabilisation and radiotherapy will relieve the patient’s pain, allow them to remain mobile and may even allow the fracture to heal.

Before embarking on stabilisation of a metastatic lesion, it is always worth taking an X-ray of the whole bone and of the other long bones. It may be that other bones need fixing at the same sitting or that there are so many metastases that stabilisation of one will make no difference to the patient’s quality of life. Patients with multiple metastases may have a high serum calcium and this will need checking before embarking on a general anaesthetic. The risk of pulmonary embolus is also high, and patients need to be warned of this when giving their consent for, surgery.

  Primary malignant bone tumours

These are very rare indeed. The commonest of this rare group is the osteosarcoma. These tumours have very variable histology and occur either in adolescents or in the elderly secondary to Pager’s disease. The tumour is metaphyseal (usually the tibia or the femur) and is easy to confuse with a stress fracture or with an infected haematoma. If the diagnosis is suspected, the tumour should not be biopsied. The patient should be referred to a team of doctors who are com­petent to undertake the surgery, the radiotherapy, the chemotherapy and the counselling of the patient.

Imaging

Characteristically, there is periosteal lifting (Codman’s trian­gle) and ‘sun-ray’ spicules of new bone within the tumour. Magnetic resonance imaging (MRI) and computerised tomo­graphy (CT) scan may be helpful in determining the true extent of the tumour within the medulla (Fig. 25.7).

Treatment

The choice of treatment depends on the histological grading of the tumour, the age of the patient, the presence or absence of secondaries and the wishes of the patient.

If there is no evidence of secondaries, and it is technically possible, an amputation may be the treatment of choice with chemotherapy used to destroy micrometastases. Alternative­ly, radiotherapy and chemotherapy to shrink the lesion fol­lowed by a massive joint replacement may carry a higher risk of recurrence but may be cosmetically and functionally much more acceptable. If massive joint replacements are to be used in growing children, then designs need to be used which allow for lengthening of the limb as the child grows. Massive allografts using bones and joints from cadaver donors have limited long-term success, and have problems with rejection and the possibility of transmission of infection.

prognosis

Survival is dependent on the histological grading and the degree of spread, but in cure rates of around 50 per cent can be achieved.

Chondrosarcoma

This tumour commonly occurs in the pelvis, ribs or proximal long bones in middle-aged people. The tumour is lyric with ill-defined boundaries and has speckled calcification within its substance (Fig. 25.8). The grade of malignancy is very variable and is closely linked to the prognosis. Low-grade tumours have a survival rate of 75 per cent at 5 years, while high-grade tumours have a survival rate of less than 10 per cent over the same period.

Fibrosarcoma

These tumours occur most commonly in the metaphysis or diaphysis of the tibia or femur, but may also arise in soft tissue. They metastasise to the lungs and the 5-year survival rare is around 30 per cent.

Synovial sarcoma

This is a highly malignant tumour which metastasises through the blood supply, bloodstream and lymphatics. Five-year survival rare is low whatever treatment is attempted.

Ewing’s tumour

This tumour is commonest in childhood and arises in the midshaft or metaphysis of long bones. The child may present with pyrexia and have a high erythrocyte sedimentation rare, so the condition can be confused with osteomyelitis. Radio­logically, there may be multiple layers of subperiosteal new bone producing an ‘onion skin’ arrangement. Although the tumour is highly malignant, aggressive treatment with chemotherapy and radiotherapy has started to produce some survivors (see Fig. 25.2).