The Epidemiology of Second Primary Cancers

BACKGROUND: Due to improvements in early detection, supportive care, and treatment, the number of cancer survivors in the United States has tripled since 1971 and is growing by 2% each year. In 2001, there were approximately 10 million cancer survivors, representing 3.5% of the population. As survival after a diagnosis of cancer improves, quantification of the late effects of cancer and its therapy become critical. One of the most serious events experienced by cancer survivors is the diagnosis of a new cancer. Second- or higher-order cancers now account for approximately 16% of incident cancers reported to the National Cancer Institute's Surveillance, Epidemiology, and End Results Program. Subsequent neoplasms may not necessarily be attributable to prior cancer treatment but may also reflect the effect of shared etiologic factors, environmental exposures, host characteristics, and combinations of influences, including gene-environment and gene-gene interactions. METHODS/RESULTS: This review will focus on selected highlights and recent findings in treatment-associated malignancies, with an emphasis on survivors of adult cancer. Current study methods will also be summarized. CONCLUSIONS: Important opportunities for future research include the prospective identification of patient subgroups that might be at heightened susceptibility of developing therapy-associated second cancers to modify planned treatments or select alternative management strategies. For the burgeoning population of cancer survivors treated successfully with past regimens, including those therapies that have been subsequently refined, continued quantification of late effects, including second cancers, remains highly relevant in terms of raising clinician and patient awareness, for informed counseling, and for the development of risk-adapted long-term management strategies.