Adolescent and young adult colorectal cancer.

Although the overall incidence of colorectal cancer (CRC) in adolescents and young adults (AYAs) is low, it has seen an increase over the past 2 to 3 decades, which contrasts with the trend of decreased incidence in the older population. This phenomenon is conceivably caused by a lack of routine CRC screening in the young population and lifestyle issues, including the obesity epidemic and dietary factors. Hereditary genetic syndromes (eg, familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer syndrome) and known predisposing medical conditions (eg, inflammatory bowel disease) account for only a minority of CRC cases in AYA. Younger patients with CRC commonly present with more advanced disease at diagnosis and exhibit specific molecular and clinical characteristics associated with a distinct biologic phenotype of CRC compared with older individuals. Matched for stage, however, the prognosis of patients with young-onset CRC is similar to or better than that for older patients. A surprising paucity of data exists on outcomes associated with modern systemic cytotoxic and biologic therapy specifically in young patients with CRC. The toxicity pattern of these treatments, however, differs between young and older patients, partly because of the lower rate of pertinent comorbidities in younger adults. Issues regarding surgical management in the setting of hereditary syndromes and fertility preservation while on therapy are of particular importance to the younger patient population. Future studies should seek to increase understanding of the distinct tumor biology of AYA patients with CRC and the consequences of treatment interventions to optimize outcomes for this population.