Second malignant neoplasms after successful treatment of childhood cancers.

Improved treatment and supportive care have increased the survival of children diagnosed with cancer. This success has resulted in a growing population at risk of long-term complications of therapy, including secondary malignancy. These neoplasms may result from the direct effect of the modalities used in treatment of the primary tumor, more indirect effects of the treatment or supportive care, the genetic predisposition of the patient, or to interactions among these factors. The increasing success of cancer therapy is producing a rapidly growing population of patients at risk of second malignancy. This is a result of the increasing intensity of treatments and the increasing duration of survival, which provides the time to manifest the late effects of therapy. The concept that a patient is "cured" at some arbitrary time after treatment does not diminish the need for follow-up of all cancer survivors to identify and treat secondary malignancies. These risks have led to an increased effort to define phenotypic and genotypic categories of patients that may be cured with less intensive therapy and to develop molecularly targeted drugs that have fewer noxious effects on normal tissues.