In 1970, when I was the final months of my pediatric residency at Boston Children’s Hospital, I spent four weeks on the children’s cancer ward. This was a service staffed by some of the most dedicated physicians and nurses in that storied institution, and the care they provided the children was superb. However, the ward was a sad place, because in 1970 a diagnosis of childhood cancer was a death sentence. Chemotherapy was in its infancy. The chemicals were harsh and painful. The best outcome for which we could hope was a remission of a few months’ duration. In that era, virtually every child with cancer died.
Since that time, progress in the treatment of childhood cancer has been spectacular.  This progress has been the fruit of remarkable advances in medicine, surgery and basic biology. The first five-year survival of a child with pediatric leukemia was reported in the 1970s (1). Today, more than 85% of children with leukemia are cured, and the mortality rate for all forms of pediatric malignancy in the United States has fallen by 70% (2). This is one of the great triumphs of modern medicine.
Unfortunately, this success in the treatment of pediatric cancer is not the entire story. In the same years as childhood cancer deaths were falling because of better treatments, the incidence of childhood cancer – the number of new cases per 1,000 children – was increasing. Leukemia incidence in the United States has increased by 21% since 1976 (3), brain cancer incidence by 45% (3), and testicular cancer incidence  by 51% (2).  Cancer is now the leading cause of death by disease among American children under the age of 15 years.
The causes of these increases in cancer incidence are only partially understood. They are far too rapid to be of genetic origin. It has been suggested that they may reflect improved access to medical care or the increasingly widespread availability of newer diagnostic technologies such as MRI and CAT scan. That explanation might have accounted for a one-time “bump” in cancer incidence when Medicaid was introduced or newer imaging techniques first became available. However, it fails to explain the continuing  increase in incidence of three different types of childhood cancer over a span of five decades (4). The conclusion becomes inescapable that external, environmental factors must be responsible for at some of the increase.

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