Abstract 1822: Age-period-cohort (APC) analysis of primary bone cancer incidence rates in the United States (1976 – 2005)

Abstract BACKGROUND: Primary bone cancer comprises three major histological subtypes: osteosarcoma (OS), Ewing sarcoma (ES) and chondrosarcoma (CS). The most frequent subtype, OS, primarily occurs in adolescence, but has a second peak at the oldest ages, usually attributed to late effects of radiotherapy and chemotherapy, and Paget's disease. The adolescent age distribution of ES resembles that of OS, suggesting a link between the onset of puberty and these subtypes of bone cancer. CS is rare in childhood, and incidence rates, unlike those of OS and ES, increase fairly uniformly with age. Given the limited knowledge about the etiology of primary bone cancer, and the unusual age-incidence distribution for OS and ES, we undertook an APC analysis to determine whether incidence varied by birth cohort or calendar period. For other cancers, such as testis and breast, the identification of cohort patterns has generated new hypotheses regarding environmental risk factors. METHODS: We fit an APC model to incidence data among U.S. whites for OS, ES and CS obtained from nine registries of the Surveillance, Epidemiology, and End Results (SEER) program, which covers about 10% of the U.S. population, 1976-2005. The purpose was to examine the temporal development of each bone cancer subtype, with an aim to providing etiologic clues as to the role of birth cohort-related changes. RESULTS: Incidence of OS decreased between 1976 and 2005 among those 60 years and older, and rates declined among cohorts born 1905-34. The risk of CS doubled among females 20-69 years, with rates increasing among consecutive birth cohorts born 1925-54, whereas those of males were unaltered. For both sexes, ES incidence rates tended to be stable. CONCLUSIONS: The risk reduction in OS at older ages was most likely due to improved radiotherapy and more effective chemotherapy. The CS risk increase in females corresponds to birth cohorts who were increasingly exposed to estrogens, both in terms of contraceptives (from 1960 onwards), and hormone replacement therapy (from 1950 onwards). In support of our hypothesis that estrogens are involved in the increase in CS among women over time, in vitro studies show that the estrogen signaling pathway stimulates proliferation of both normal and malignant chondrocytes. Further studies are warranted to pursue the possible etiological significance of estrogen exposure in CS risk. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1822.