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 following health care professionals and others to ensure that children receive treatment, supportive care, and rehabilitation that will achieve optimal survival and quality of life:
- Primary care physician.
- An ophthalmologist with extensive experience in the treatment of children with retinoblastoma.
- Pediatric surgical subspecialists.
- Radiation oncologists.
- Pediatric medical oncologists/hematologists.
- Rehabilitation specialists.
- Pediatric nurse specialists.
- Social workers.
(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 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 therapies 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.[1,3,4] Between 1975 and 2010, childhood cancer mortality has decreased by more than 50%.[1,3,4] 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.)Incidence
Retinoblastoma is a relatively uncommon tumor of childhood that arises in the retina and accounts for about 3% of the cancers occurring in children younger than 15 years. The estimated annual incidence in the United States is approximately 4 cases per 1 million children younger than 15 years. Although retinoblastoma may occur at any age, it most often occurs in younger children; the annual incidence is 10 to 14 cases per 1 million in children aged 0 to 4 years. Ninety-five percent of cases are diagnosed before age 5 years, and two-thirds of these cases occur before age 2 years. Older age is usually associated with more advanced disease and a poorer prognosis.Heritable and Nonheritable Forms of Retinoblastoma
Retinoblastoma is a tumor that occurs in heritable (25% to 30%) and nonheritable (70% to 75%) forms. Heritable disease is defined by the presence of a positive family history, multifocal retinoblastoma, or an identified germline mutation of the RB1 gene. This germline mutation may have been inherited from an affected progenitor (25%) or may have occurred in utero at the time of conception in patients with sporadic disease (75%). Heritable retinoblastoma may manifest as unilateral or bilateral disease. The penetrance of the RB1 mutation (laterality, age at diagnosis, and number of tumors) is probably dependent on concurrent genetic modifiers such as MDM2 and MDM4.[6,7] Approximately 85% of patients with unilateral retinoblastoma do not have the heritable form of the disease, whereas all children with bilateral disease are presumed to have the heritable form, even though only 25% have an affected parent. In heritable retinoblastoma, tumors tend to be diagnosed at a younger age than in the nonheritable form of the disease. Unilateral retinoblastoma in children younger than 1 year raises concern for heritable disease, whereas older children with a unilateral tumor are more likely to have the nonheritable form of the disease.[8,9]Screening
Children with the heritable form of retinoblastoma may continue to develop new tumors for a few years after diagnosis and treatment; for this reason, they need to be examined frequently for the development of new tumors. It is recommended that they be examined every 2 to 4 months for at least 28 months. The interval between exams is based on the age of the child (less frequent visits as the child ages) and the stability of the disease.
Early-in-life screening by fundus exams under general anesthesia at regular intervals, according to a schedule based on the absolute estimated risk, can improve prognosis in terms of globe sparing and use of less-intensive, ocular-salvage treatments in children with a positive family history of retinoblastoma. Because a proportion of children who present with unilateral retinoblastoma will eventually develop disease in the opposite eye, periodic examinations of the unaffected eye are performed until the germline status of the RB1 gene is determined.
The parents and siblings of patients with retinoblastoma should have screening ophthalmic examinations to exclude an unknown familial disease. Siblings should continue to be screened until age 3 to 5 years or until it is confirmed that they do not have a genetic mutation.
Blood and/or tumor samples can be screened to determine if a patient with retinoblastoma has a mutation in the RB1 gene. Once the patient's genetic mutation has been identified, other family members can be screened directly for the mutation. The RB1 gene is located within the q14 band of chromosome 13. Exon by exon sequencing of the RB1 gene demonstrates germline mutation in 90% of patients with heritable retinoblastoma.[12-14] Although a positive finding with current technology confirms susceptibility, a negative finding cannot absolutely rule it out. A multistep assay including DNA sequencing to identify mutations within coding exons and immediate flanking intronic regions, Southern blot analysis to characterize genomic rearrangements, and transcript analysis to characterize potential splicing mutations buried within introns may need to be performed for a complete genetic evaluation of the RB1 gene. In cases of somatic mosaicism or cytogenetic abnormalities, the mutations may not be easily detected, and more exhaustive techniques such as karyotyping, multiplex ligation-dependent probe amplification, fluorescence in situ hybridization, and methylation analysis of the RB1 promoter may be needed. The absence of detectable RB1 mutations in some patients may suggest that alternative genetic mechanisms may underlie the development of retinoblastoma. In a report of 29 patients with clinical retinoblastoma and no evidence of a RB1 mutation, 15 demonstrated high levels of MYCN amplification. These patients had distinct, aggressive, histologic features and a median age at diagnosis of 4 months.
Genetic counseling is an integral part of the management of patients with retinoblastoma and their families, regardless of clinical presentation; counseling assists parents in understanding the genetic consequences of each form of retinoblastoma and in estimating the risk of disease in family members.[14,18] Genetic counseling, however, is not always straightforward. Families with retinoblastoma may have a founder mutation with embryonic mutagenesis causing genetic mosaicism of gametes. A significant proportion (10%–18%) of children with retinoblastoma have somatic genetic mosaicism,[20,21] making the genetic story more complex and contributing to the difficulty of genetic counseling.Factors Influencing Mortality
The present challenge for those who treat retinoblastoma is to preserve life and to prevent the loss of an eye, blindness, and other serious effects of treatment that reduce the life span or the quality of life. With improvements in the diagnosis and management of retinoblastoma over the past several decades, metastatic retinoblastoma is observed less frequently in the United States and other developed nations. As a result, other causes of retinoblastoma-related mortality in the first decade of life, such as trilateral retinoblastoma and subsequent neoplasms (SNs), have become significant contributors to retinoblastoma-related mortality. In the United States, before the advent of chemoreduction as a means of treating bilateral (heritable) disease, trilateral retinoblastoma contributed to more than 50% of retinoblastoma-related mortality in the first decade after diagnosis.Trilateral retinoblastoma
Trilateral retinoblastoma is a well-recognized syndrome that occurs in 5% to 15% of patients with heritable retinoblastoma and is defined by the development of an intracranial midline neuroblastic tumor, which typically develops more than 20 months after the diagnosis of retinoblastoma. Patients who are asymptomatic at the time of diagnosis with an intracranial tumor have a better outcome than patients who are symptomatic.
Given the poor prognosis of trilateral retinoblastoma and the short interval between the diagnosis of retinoblastoma and the occurrence of trilateral disease, routine neuroimaging could potentially detect the majority of cases within 2 years of first diagnosis. Although it is not clear whether early diagnosis can impact survival, screening with magnetic resonance imaging has been recommended as often as every 6 months for 5 years for those suspected of having heritable disease or those with unilateral disease and a positive family history. Computed tomography scans are generally avoided for routine screening in these children because of the perceived risk of exposure to ionizing radiation.Subsequent neoplasms (SNs)
Patients with heritable retinoblastoma have a markedly increased frequency of SNs.[24,25] There may be an association between type of RB1 mutation and incidence of SNs, with complete loss of RB1 activity having a higher incidence of SNs. The cumulative incidence was reported to be 26% (± 10%) in nonirradiated patients and 58% (± 10%) in irradiated patients by 50 years after diagnosis of retinoblastoma—a rate of about 1% per year. However, more recent studies analyzing cohorts of patients treated with more advanced radiation planning and delivery technology have reported the rates to be about 9.4% in nonirradiated patients and about 30.4% in irradiated patients. The most common SN is osteosarcoma, followed by soft tissue sarcoma and melanoma; these malignancies may occur inside or outside of the radiation field, although most are radiation-induced. The carcinogenic effect of radiation therapy is associated with the dose delivered, particularly for subsequent sarcomas, where a step-wise increase is apparent at all dose categories. In irradiated patients, two-thirds of SNs occur within irradiated tissue, and one-third occur outside the radiation field.[27-29]
The risk of SNs also appears to be dependent on the patient's age at the time the external-beam radiation therapy is given, especially in children younger than 12 months, and the histopathologic types of SNs may be influenced by age.[28,30,31] These data support a genetic predisposition to soft tissue sarcomas, in addition to the risk of osteosarcoma.
There is no evidence of an increased incidence of acute myeloid leukemia in children with heritable retinoblastoma.; [Level of evidence: 3iiiA] Of 245 patients, all of whom received etoposide, only one patient had acute promyelocytic leukemia after 79 months.
With the increase in survival of patients with heritable retinoblastoma, it has become apparent that they are also at risk of developing epithelial cancers late in adulthood. A marked increase in mortality from lung, bladder, and other epithelial cancers has been described.[34,35]
Survival from SNs is certainly suboptimal and varies widely across studies.[25,34,36-39] However, with advances in therapy, it is essential that all SNs be treated with curative intent. Those who survive SNs are at a sevenfold increased risk for developing another SN. The risk further increases threefold when patients are treated with radiation therapy for their retinoblastoma. Retinoblastoma survivors with bilateral disease and an inherited germline mutation are at a slightly higher risk of a SN than those without an inherited mutation; this increase appears to be most significant for melanoma.Late Effects from Retinoblastoma Therapy
Orbital growth is somewhat diminished after enucleation; however, the impact of enucleation on orbital volume may be less after placement of an orbital implant.
Patients with retinoblastoma demonstrate a variety of long-term visual field defects after treatment for their intraocular disease. These defects are related to tumor size, location, and treatment method. One study of visual acuity after treatment with systemic chemotherapy and focal ophthalmic therapy was conducted in 54 eyes in 40 children. After a mean follow-up of 68 months, 27 eyes (50%) had a final visual acuity of 20/40 or better, and 36 eyes (67%) had final visual acuity of 20/200 or better. The clinical factors that predicted visual acuity of 20/40 or better were a tumor margin at least 3 mm from the foveola and optic disc and an absence of subretinal fluid.
Because systemic carboplatin is now commonly used in the treatment of retinoblastoma (refer to the Intraocular Retinoblastoma and Extraocular Retinoblastoma sections of this summary for more information), concern has been raised about hearing loss related to therapy. While an analysis of 164 children treated with six cycles of carboplatin-containing therapy (18.6 mg/kg per cycle) showed no loss of hearing among children who had a normal initial audiogram, another series documented hearing loss in 17% of patients. Age younger than 6 months at the time of treatment and higher carboplatin systemic exposures appear to correlate with an increased risk of ototoxicity.[48,49]References
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