Paediatrics: Bone tumours

Bone tumours

These tumours are rare in childhood (5% of all paediatric malignancies).

·  Incidence peaks in teenage years, in which they are the 4th most common group of malignancies.

·  Majority of cases are osteosarcoma (OS) or Ewing’s sarcoma (ES). They are histologically distinct, with different patterns of disease and response to treatment.

·  Sarcomas are associated with Li–Fraumeni syndrome (familial mutation of p53), and patients cured of familial retinoblastoma are at a high risk of OS.

Osteosarcoma

Presentation

Localized pain and swelling, pathological fracture, and rarely erythema. Most affect the long bones around the knee (67%) and humerus. The metaphysis is a more common site than mid-shaft. Delay in diagnosis is common.

Metastases

·  Seen at diagnosis in 15–25% of cases

·  Lungs most common site, followed by bones.

Diagnostic investigations

·  Plain X-rays of bony lesion.

·  Biopsy (for definitive diagnosis).

·  Lactate dehydrogenase and alkaline phosphatase.

·  MRI of primary site.

·  CT chest.

·  Isotope bone scan.

Treatment

Chemotherapy, followed by surgery and then further chemotherapy. The aim is to perform limb-preserving surgery whenever possible.

Prognosis

Adverse outlook is associated with:

·  Inability to resect primary tumour.

·  Poor response to induction chemotherapy.

·  Metastatic disease (especially extrapulmonary disease).

Relapsed osteosarcoma

Most recurrences are isolated pulmonary metastases. Surgical resection can result in long-term survival in 20–30% of patients. The role of chemo-therapy for recurrent OS is uncertain. The role of radiotherapy is limited to palliation.

Ewing’s sarcoma of bone and soft tissue

ES usually occurs in bone, but may also occur in soft tissues. ES and pe-ripheral PNETs share a common immunophenotype (CD99 or MIC2) and cytogenetic profile (t(11;22) in 85% and t(21;22) in 5–10%). Both tumour categories belong to the Ewing’s family of tumours. (Note: Peripheral PNET should not be confused with CNS PNET tumours.)

Presentation

Localized pain and swelling, and sometimes pathological fracture. The diaphysis of long bones is more commonly affected than metaphysis. The axial skeleton is involved more often than in OS with pelvis the most com-mon site. Metastases to lungs and bone are more common at diagnosis than in OS.

Diagnostic investigations

·Plain X-rays of bony lesion.

·Biopsy (for definitive diagnosis).

·Lactate dehydrogenase and alkaline phosphatase.

·MRI of primary site.

·CT chest.

·Isotope bone scan.

·Bone marrow aspirates and trephines (bilateral).

Treatment

Chemotherapy, followed by surgery and then further chemotherapy. For extremity sites, limb-preserving surgery is the aim whenever possible. Radiotherapy is an effective adjunct, and an alternative to surgery, partic-ularly at axial sites.

Prognosis

Adverse outlook associated with:

·large primaries;

·axial sites;

·poor response to induction chemotherapy;

·metastatic disease.

Bony metastases confer a particularly grave prognosis with <20% long-term survivors.

Relapsed ES

Salvage therapy is rarely successful, and will depend on treatment pre-viously received. Second-line chemotherapy may include combinations involving Etoposide, carboplatin, cyclophosphamide, topotecan and irono-tecan. Surgery and radiotherapy may also have a role in treatment.