Rates and Risk Factors
Rates and Risk Factors
Bone cancers account for about five percent of all childhood cancers. The two main classifications of bone cancers in children are osteosarcoma, the more frequent type, and Ewing's sarcoma.
The incidence of bone cancers in both the US and NJ was 0.7 per 100,000 children during 1979-1995 (Table 1a). Osteosarcoma was the most commonly diagnosed bone cancer with an incidence of 0.4 per 100,000 children. Ewing's sarcoma accounted for most of the remaining cases. Both black and white children had the same incidence of total bone cancer. Very few cases of Ewing's sarcoma occurred among the black population (Table 1b), but black children had a higher incidence rate of osteosarcoma than white children.
Incidence and Mortality Trends
Figure 11 presents bone cancer incidence and mortality trends. Bone cancer incidence rates in NJ experienced two small peaks to 0.9 per 100,000 children in 1987 and 1991 and then declined to the original rate of about 0.6 per 100,000 children by the end of the period. The national incidence rate was constant at 0.7 per 100,000 children. The mortality rates for NJ and the US were the same throughout the period at 0.1 cases per 100,000 children.
Bone cancer incidence rates increase at puberty, suggesting an association with hormonal effects on bone growth. Osteosarcoma incidence among girls is slightly higher than among boys, and black children have a higher incidence than do white children. Eighty percent of osteosarcoma cases occur in the long bones of the leg, and twelve percent arise in the long bones of the arm.
In contrast to osteosarcoma, Ewing's sarcoma is less frequent in black children than white children. Thirty-eight percent of Ewing's sarcoma cases arise in the long bones of the lower leg, with the remaining cases arising mostly in the pelvic bone, upper arm, or ribs.
Five-year survival rates have been increasing for bone cancers in children. For all malignant bone and joint cancers combined, the five-year survival rate has increased from 54 percent in the 1974-76 time period to approximately 64 percent in the 1986-93 time period.6
Genetic Risk Factors
Osteosarcomas can be related to some hereditary bone diseases. Bone sarcomas have also been associated with the treatment of other cancers by radiation and chemotherapy; that is, they sometimes occur as second primary cancers among children.6, 7