Cancer Incidence, Survival, and Mortality Among Adolescents and Young Adults

Abstract

While the epidemiology of cancer has been studied in children and older adults for more than a half century, little attention had been paid to the cancers in between those that occur in the older adolescents and young adult (AYA) between 15 and 40 years of age. Yet as recently ascertained, more than a million new cases of invasive cancer are diagnosed in AYAs annually worldwide. Not only are the array of cancers that are diagnosed in AYAs unique, accumulating evidence suggests that many are biologically distinct from what appears to be the same neoplasm in younger and older persons. AYA cancers may thereby have different etiologies and require different therapeutic strategies. Many cancers peak in incidence in AYAs, and there is an intermediate peak between the well-known childhood cancer peak and the predominant one that occurs in the elderly. If the cancers that account for the childhood peak are embryonal/fetal cancers and those that account for the peak late in life as the cancers of aging, the AYA peak may be considered as due to cancers of intermediate growth and maturation. For most of the past quarter century, the incidence of the AYA cancers has been increasing for reasons that have not been ascertained. In Europe, the United States, and Japan, the 5-year survival rates of the vast majority of cancers in AYA have been remarkably similar. In the United States, the overall rate of survival improvement had been less in AYAs than in either younger or older patients. The trends and patterns of incidence do offer certain clues as to cancer causation in AYAs and potential methods of prevention. Detailed analyses of incidence patterns by geographic region and demographic factors together with determination of variations in incidence in time and space should provide additional insights into etiology and separate lines of investigation and therapeutic opportunities.