Background: Primary bone cancer comprises three major histologic types: osteosarcoma (OS), Ewing sarcoma (ES), and chondrosarcoma (CS). Given the limited knowledge about the etiology of primary bone cancer, we undertook an age-period-cohort (APC) analysis to determine whether incidence varied by birth cohort or calendar period. The purpose was to examine the temporal development of each bone cancer type and generate etiologic hypotheses via the observed birth cohort-related changes.
Methods: An APC model was fitted to incidence data for U.S. whites for OS, ES, and CS obtained from nine registries of the Surveillance, Epidemiology, and End Results program, which covers about 10% of the U.S. population, 1976-2005.
Results: The incidence of OS decreased between 1976 and 2005 among those aged over 60 years, a decline that occurred among patients with OS as their primary malignancy only. From 1986-1995 to 1996-2005, the incidence rate of CS among females of 20 to 69 years rose by about 50%, with rates increasing among consecutive cohorts born during 1935-1975. CS rates among males were stable, as were rates of ES.
Conclusion: The risk reduction in OS as a primary malignancy at older ages could possibly be related to diminished exposure over time to bone-seeking radionuclides. The CS increase among females corresponds to birth cohorts with rising exposures to oral contraceptives and menopausal hormonal therapy.
Impact: As the estrogen signaling pathway has been shown to stimulate proliferation of normal and malignant chondrocytes, estrogen exposure may increase the risk for CS. Further studies are warranted to clarify its possible etiological significance.