Childhood Cancer: Occurrence, Treatment and Risk of Second Primary Malignancies

Simple Summary Childhood cancers are mostly of unknown etiology and represent devastating diagnoses. The clinical benefits of steadily increasing tumor control and survival rates are countered by severe and fatal health consequences from genotoxic therapies in long-term survivors of pediatric cancers. Among them, iatrogenic second primary malignancies represent the heaviest burden for the patient. Therefore, particularly in pediatric tumor patients, the reduction of genotoxic treatments and the use of targeted or immune-based oncologic strategies are of high clinical interest. The knowledge of therapy-associated as well as intrinsic risk factors for late sequelae of antineoplastic treatments including secondary primary malignancies offers the opportunity to adapt oncologic therapies for high-risk patients and to intensify follow-up with intervention strategies and multidisciplinary care. Cancer represents the leading cause of disease-related death and treatment-associated morbidity in children with an increasing trend in recent decades worldwide. Nevertheless, the 5-year survival of childhood cancer patients has been raised impressively to more than 80% during the past decades, primarily attributed to improved diagnostic technologies and multiagent cytotoxic regimens. This strong benefit of more efficient tumor control and prolonged survival is compromised by an increased risk of adverse and fatal late sequelae. Long-term survivors of pediatric tumors are at the utmost risk for non-carcinogenic late effects such as cardiomyopathies, neurotoxicity, or pneumopathies, as well as the development of secondary primary malignancies as the most detrimental consequence of genotoxic chemo- and radiotherapy. Promising approaches to reducing the risk of adverse late effects in childhood cancer survivors include high precision irradiation techniques like proton radiotherapy or non-genotoxic targeted therapies and immune-based treatments. However, to date, these therapies are rarely used to treat pediatric cancer patients and survival rates, as well as incidences of late effects, have changed little over the past two decades in this population. Here we provide an overview of the epidemiology and etiology of childhood cancers, current developments for their treatment, and therapy-related adverse late health consequences with a special focus on second primary malignancies.