During the past five decades, dramatic progress has been made in the development of curative therapy for pediatric malignancies. Long-term survival into adulthood is the expectation for 80% of children with access to contemporary therapies for pediatric malignancies. The therapy responsible for this survival can also produce adverse long-term health-related outcomes, referred to as "late effects," that manifest months to years after completion of cancer treatment. A variety of approaches have been used to advance knowledge about the very long-term morbidity associated with childhood cancer and its contribution to early mortality. These initiatives have utilized a spectrum of resources including investigation of data from population-based registries, self-reported outcomes provided through large-scale cohort studies, and information collected from medical assessments. Studies reporting outcomes in survivors who have been well characterized in regards to clinical status and treatment exposures, and comprehensively ascertained for specific effects through medical assessments, typically provide the highest quality of data to establish the occurrence and risk profiles for late cancer treatment-related toxicity. Regardless of study methodology, it is important to consider selection and participation bias of the cohort studies in the context of the findings reported.
Figure 1. Investigators from the Childhood Cancer Survivor Study (CCSS), a retrospective multi-institutional cohort investigation that has been monitoring health outcomes of more than 20,000 long-term childhood cancer survivors for more than 15 years, estimated a cumulative incidence of 73.4% for at least one chronic health problem (grades 1–5) by age 40 years among the 10,397 adult participants (mean age, 26.6 years); more than 40% will experience a chronic condition that is severe, life-threatening, or fatal (grades 3–5). The risk of specific late effects in an individual is dependent upon the type and location of the cancer and therapeutic interventions undertaken to control the cancer. Oeffinger KC, Mertens AC, Sklar CA, et al.: Chronic health conditions in adult survivors of childhood cancer. N Engl J Med 355 (15): 1572-82, 2006. Copyright © 2006 Massachusetts Medical Society.
Late effects are commonly experienced by adults who have survived childhood cancer and demonstrate an increasing prevalence associated with longer time elapsed from cancer diagnosis. Population-based studies support excess hospital-related morbidity among childhood cancer survivors compared with age- and gender-matched controls.[3,4,5,6,7] Research has clearly demonstrated that late effects contribute to a high burden of morbidity among adults treated for cancer during childhood, with 60% to almost 90% developing one or more chronic health conditions and 20% to 40% experiencing severe or life-threatening complications during adulthood.[2,8,9,10,11] Recognition of late effects, concurrent with advances in cancer biology, radiological sciences, and supportive care, has resulted in a change in the prevalence and spectrum of treatment effects. In an effort to reduce and prevent late effects, contemporary therapy for the majority of pediatric malignancies has evolved to a risk-adapted approach that is assigned based on a variety of clinical, biological, and sometimes genetic factors. With the exception of survivors requiring intensive multimodality therapy for aggressive or refractory/relapsed malignancies, life-threatening treatment effects are relatively uncommon after contemporary therapy in early follow-up (up to 10 years after diagnosis). However, survivors still frequently experience life-altering morbidity related to effects of cancer treatment on endocrine, reproductive, musculoskeletal, and neurologic function.