Up until thirty years ago, leukemia was considered a fatal disease. Fortunately nowadays, acute lymphoblastic leukemia, the most common type of childhood leukemia, is cured in over 80% of the patients. This means that most patients are ultimately cured and disease-free.
Significant progress has also been achieved in the treatment of solid tumors. In the past, when surgery was the only available treatment, survival rates were 0-20% and the surgery-related mortality was high. In the 1950s, radiotherapy was incorporated to the treatment of pediatric malignancies; the first positive results were observed for the management of Hodgkin lymphoma and Wilms’ tumor. In the 1960s, benefitting from the previous experience in the field of leukemia, chemotherapy was integrated to the treatment of solid tumors, in combination with surgery and radiotherapy. Over the following three decades, the combination of all these treatment modalities in collaborative, multicentric studies, led to increased survival rates for most pediatric solid tumors. In Spain, the average survival is as high as 80%. Over the last years, clinical trials have emerged as the best tool to evaluate the efficacy of new treatments for childhood cancer.
Leukemia is the most common cancer in children; it accounts for about one third of pediatric malignancies. Acute lymphoblastic leukemia (ALL) is the most frequent malignancy, with 80% of acute leukemias being ALL and 20% being acute myeloid leukemia (AML). The survival rates of patients with ALL has significantly increased over the last decades: from 20% in the 1960s to over 80% with current treatments.
In spite of these excellent results, there is still a small group of patients (10-20%) for which the available treatments fail. New therapeutic strategies should be designed for these patients, in order to improve their outcomes.
Brain tumors are the most frequent pediatric solid tumors, accounting for about 20% of all childhood cancer cases.
Over the last years, the diagnostic tools such as neuro-imaging, immunohistochemistry and molecular diagnosis, have been improved. Furthermore, the surgical treatments have been refined, and the new radiotherapy techniques have reduced long-term sequelae. However, there is still room for improvement: the outcome of this group of patients remains dismal, with their survival rates being the lowest among children with cancer.
The most relevant pediatric bone tumors are osteosarcoma and Ewing sarcoma. According to the national tumor registry (RETI-SEHOP), bone tumors account for about 7% of all pediatric tumors in Spain.
Up until recently, the results obtained in the treatment of these tumors were discouraging. Nevertheless, over the last years, the combination of surgery, systemic chemotherapy and radiotherapy, has significantly improved the outcome of these tumors.
The use of neoadjuvant therapies has led to more conservative surgical treatments.
TUMORS OF THE SYMPATHETIC NERVOUS SYSTEM
Neuroblastoma accounts for about 8-10% of all pediatric tumors. The mean age at diagnosis is 22 months; 40% of children are diagnosed before one year of age, 80% before four years of age, and 97% before ten years of age.
Local tumors usually have a very good prognosis; the biological features of the tumor determine the outcome and the treatment strategy. Unfortunately, the outcome of metastatic neuroblastoma continues to be dismal, posing a major challenge in the field of pediatric oncology.
Wilms’ tumor is the most frequent renal tumor, accounting for 6% of all pediatric tumors. The highest incidence occurs in young children (1-5 years old), particularly in 2-3 year-old children.
Wilms’ tumor is an embryonal tumor, and has the potential ability to become metastatic. However, it is very sensitive to both chemotherapy and radiotherapy, and hence the chances of curing the disease are high. In fact, over 90% of children with Wilms’ tumor can be cured nowadays.