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.
Figure 1. Cancer incidence rates for patients aged 0 to 14 years and 15 to 19 years in the Surveillance Epidemiology and End Results (SEER) program from 2005 to 2009. Incidence rates are age-adjusted and age-specific and are shown for leukemia, lymphoma, central nervous system (CNS) tumors, neuroblastoma, retinoblastoma, renal tumors, hepatic tumors, bone tumors, soft tissue tumors, germ cell tumors, carcinomas and melanomas, and other cancers. Retinoblastoma occurs infrequently in adolescents aged 15 to 19 years.
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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