General Information About Unusual Cancers of Childhood
Fortunately, cancer in children and adolescents is rare, although the overall incidence of childhood cancer has been slowly increasing since 1975. Children and adolescents with cancer should be referred to medical centers that have a multidisciplinary team of cancer specialists with experience treating the cancers that occur during childhood and adolescence. This multidisciplinary team approach incorporates the skills of the primary care physician, pediatric surgical subspecialists, radiation oncologists, pediatric medical oncologists/hematologists, rehabilitation specialists, pediatric nurse specialists, social workers, and others to ensure that children receive treatment, supportive care, and rehabilitation that will achieve optimal survival and quality of life. (Refer to the PDQ Supportive and Palliative Care summaries for specific information about supportive care for children and adolescents with cancer.)
Guidelines for pediatric cancer centers and their role in the treatment of pediatric patients with cancer have been outlined by the American Academy of Pediatrics. At these pediatric cancer centers, clinical trials are available for most types of cancer that occur in children and adolescents, and the opportunity to participate in these trials is offered to most patients/families. Clinical trials for children and adolescents diagnosed with cancer are generally designed to compare potentially better therapy with therapy that is currently accepted as standard. Most of the progress made in identifying curative therapy for childhood cancers has been achieved through clinical trials. Information about ongoing clinical trials is available from the NCI Web site.
Dramatic improvements in survival have been achieved for children and adolescents with cancer. Between 1975 and 2010, childhood cancer mortality decreased by more than 50%. Childhood and adolescent cancer survivors require close follow-up because cancer therapy side effects may persist or develop months or years after treatment. (Refer to the PDQ summary on Late Effects of Treatment for Childhood Cancer for specific information about the incidence, type, and monitoring of late effects in childhood and adolescent cancer survivors.)
Childhood cancer is a rare disease with less than 13,000 cases diagnosed before the age of 20 years each year in the United States. The Rare Disease Act of 2002 defines a rare disease as one that affects populations smaller than 200,000 persons in the United States and thus, by definition, all pediatric cancers would be considered rare. The designation of a pediatric rare tumor is not uniform; for example, the Italian cooperative project on rare pediatric tumors (Tumori Rari in Eta Pediatrica [TREP]) defines a pediatric rare tumor as one with an incidence of less than two per 1 million population per year and is not the subject of specific clinical trials. Yet, this definition excludes common histologic subtypes such as melanoma and thyroid carcinoma, both of which have an incidence rate in excess of five per 1 million per year.
Most diagnoses included in this summary of rare cancers are in the subset of malignancies listed in the International Classification of Childhood Cancer (ICCC) subgroup XI, including thyroid cancer, melanoma and nonmelanoma skin cancers, in addition to multiple types of carcinomas (e.g., adrenocortical carcinoma, nasopharyngeal carcinoma, and most adult-type carcinomas such as breast cancer, colorectal cancer, etc.). These diagnoses account for about 4% of cancers diagnosed in children aged 0 to 14 years, compared with about 20% of cancers diagnosed for adolescents aged 15 to 19 years (see Figure 1). The majority of cancers within subgroup XI are either melanomas or thyroid cancer, with the remaining subgroup XI cancer types accounting for only 1.3% of cancers in children aged 0 to 14 years and 5.3% of cancers within adolescents aged 15 to 19 years. The very low incidence of patients with any individual diagnosis, and their age distribution, makes these rare cancers extremely challenging to study.
Several initiatives to study rare pediatric cancers have been developed by the Children's Oncology Group (COG) and international groups. The Gesellschaft für Pädiatrische Onkologie und Hämatologie (GPOH) rare tumor project was founded in Germany in 2006. The TREP project was launched in Italy in 2000, and the Polish Pediatric Rare Tumor Study Group was launched in 2002. Within the COG, efforts have concentrated on increasing accrual to the COG registry and the rare tumor bank and developing single-arm clinical trials and increasing cooperation with adult cooperative group trials. The accomplishments and challenges of this initiative are described in detail.
The tumors discussed in this summary are very diverse; they are arranged in descending anatomic order, from infrequent tumors of the head and neck to rare tumors of the urogenital tract and skin. All of these cancers are rare enough that most pediatric hospitals might see less than a handful of some histologies in several years. The majority of the histologies described here occur more frequently in adults. Information about these tumors may also be found in sources relevant to adults with cancer.
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