Regional variation and challenges in estimating the incidence of giant cell tumor of bone.

BACKGROUND: Estimating the incidence of giant cell tumor of bone is challenging because few population-based cancer registries record benign bone tumors. We compared two approaches, the indirect (relative index) estimation approach used in The Burden of Musculoskeletal Diseases in the United States (BMUS) and a direct incidence rate approach (from registries that record giant cell tumor), to estimate giant cell tumor incidence in France, Germany, Italy, Spain, the U.K., Sweden, Australia, Canada, Japan, and the U.S. METHODS: Giant cell tumor of bone incidence was calculated with use of the BMUS relative index of giant cell tumor to osteosarcoma in three scenarios (low, base case, and high) from case series. We compared the BMUS approach with the latest data from tumor registries in Australia (1972 to 1996), Japan (2006 to 2008), and Sweden (1993 to 2011) that record giant cell tumors. United Nations population estimates were used to project results to 2013. RESULTS: The low scenario in the BMUS approach reflects data from Unni and Inwards; the incidence of giant cell tumor of bone is 0.34 relative to osteosarcoma. As the incidence of osteosarcoma is 31.4% of the total incidence of bone and joint cancers, the incidence of giant cell tumor is 0.11 times that of all bone and joint cancers. The base scenario reflects the series by Mirra et al., with a giant cell tumor incidence of 0.47 relative to osteosarcoma (0.15 to all bone and joint cancers). The high scenario reflects the series by Ward, with an incidence of 0.84 relative to osteosarcoma (0.26 to all bone and joint cancers). Differences among the three series reflect referral to a national center of excellence compared with referral to a local oncology practice. Registry data indicated a giant cell tumor incidence rate per million per year of 1.33 in Australia, 1.03 in Japan, and 1.11 in Sweden in 2013. The estimated incidence rate per million in the ten countries in 2013 ranged from 1.03 (Japan) to 1.17 (Canada) with use of the registry-based approach and from 0.73 (Japan) for the low scenario) to 2.20 (Germany) for the base case with use of the BMUS approach. CONCLUSIONS: Giant cell tumor of bone affects approximately one person per million per year in the ten countries studied. Estimates derived with use of age-specific incidences from tumor registries were typically within the range of the low and base case BMUS scenarios. We recommend the registry-derived method for estimating the incidence of giant cell tumor.