Osteosarcoma rarely affects young children. To determine the clinical characteristics and the prognosis of this cancer in children of less than 5 years at diagnosis, we retrospectively analysed medical records of these patients treated in French centers between 1980 and 2007. A centralised histological review was carried out.

Fifteen patients were studied. Long bones were involved in 14 cases. Metastases at diagnosis were observed in 40% of patients. Histologic type was 74% osteoblastic.

In 3 cases (20%) tumours occurred on a particular background (tall constitutional size, treatment with growth hormone and pregnancy induced by clomiphene). One child had a second cancer 13 years after the first diagnosis.

Twelve children received pre-operative chemotherapy including high dose methotrexate: 5 of them had progressive disease; only 36% had good histological response (less than 10% viable cells). Limb salvage surgery was performed in six cases (40%).

Chemotherapy was well tolerated in most patients. A one-year-old child developed a severe late convulsant encephalopathy with lesions of the white substance that could be due to methotrexate despite adjustment of doses to his weight.

The functional recovery of the three analysable children who underwent limb salvage surgery is uneven and shows frequent mechanical or infectious complications (2 to 5 reinterventions per patients).

First complete remission (CR) was obtained in 12 children, six of them relapsed. With a median follow-up of 15 years, six are alive in CR, six died of disease (40%), two were lost to follow-up and one has stable disease with metastasis.

This study shows that osteosarcoma seems to be more aggressive in children under five years of age. Surgical management remains difficult in this population. Prospective studies are still needed to confirm these observations.