Neuroblastoma is the most common extracranial solid cancer in childhood and the most common cancer in infancy, with an annual incidence of about 650 new cases per year in the US. Close to 50 percent of neuroblastoma cases occur in children younger than two years old. It is a neuroendocrine tumor, arising from any neural crest element of the sympathetic nervous system or SNS. A branch of the autonomic nervous system, the SNS is a nerve network that carries messages from the brain throughout the body and is responsible for the fight-or-flight response and production of adrenaline or epinephrine. Its solid tumors, which take the form of a lump or mass, commonly begin in one of the adrenal glands, though they can also develop in nerve tissues in the neck, chest, abdomen, or pelvis. Esthesioneuroblastoma, also known as olfactory neuroblastoma, is believed to arise from the olfactory epithelium and classification remains controversial. Since it is not a sympathetic nervous system malignancy it is a distinct clinical entity not to be confused with neuroblastoma.
The cause of neuroblastoma is unknown, though most physicians believe that it is an accidental cell growth that occurs during normal development of the adrenal glands.
Neuroblastoma is one of the rare human malignancies known to demonstrate spontaneous regression from an undifferentiated state to a completely benign cellular appearance.
The highest incidence is in the first year of life as children afflicted with neuroblastoma are assumed to be born with the cancer, and some cases are congenital. The age range is broad, including older children and adults, but only 10% of cases occur in people older than 5 years of age.
Often because symptoms are so unclear, 50 to 60% of all neuroblastomas have already spread (metastasized) to other parts of the body by the time a diagnosis is made.
The diagnosis is usually confirmed by a surgical pathologist, taking into account the clinical presentation, microscopic findings, and other laboratory tests. On microscopy, the tumor cells are typically described as small, round and blue, and rosette patterns (Homer-Wright pseudo-rosettes) may be seen. A variety of immunohistochemical stains are used by pathologists to distinguish neuroblastomas from histological mimics, such as rhabdomyosarcoma, Ewing's sarcoma, lymphoma and Wilms' tumor. In February 2007, Althea Technologies announced the development of a molecular diagnostic capable of clearly differentiating various types of childhood cancers, developed in cooperation with the U.S. National Cancer Institute (NCI).
In about 90% of cases of neuroblastoma, elevated levels of catecholamines or its metabolites are found in the urine or blood. Catecholamines and their metabolites include dopamine, homovanillic acid (HVA), and/or vanillylmandelic acid (VMA).
Another way to detect neuroblastoma is the mIBG scan (meta-iodobenzylguanidine), which is taken up by 90 to 95% of all neuroblastomas, often termed "mIBG-avid." The mechanism is that mIBG is taken up by sympathetic neurons, and is a functioning analog of the neurotransmitter norepinephrine. When it is radio-ionated with I-131 or I-123 (radioactive iodine isotopes), it is a very good radiopharmaceutical for diagnosis and monitoring of response to treatment for this disease. With a half-life of 13 hours, I-123 is the preferred isotope for imaging sensitivity and quality. I-131 has a half-life of 8 days and at higher doses is an effective therapy as targeted radiation against relapsed and refractory neuroblastoma.
Neuroblastoma is one of the peripheral neuroblastic tumors (pNTs) that have similar origins and show a wide pattern of differentiation ranging from benign ganglioneuroma to stroma-rich ganglioneuroblastoma with differentiating neuroblastic cells intermixed or in nodules, to highly malignant neuroblastoma. This distinction in the pre-treatment tumor pathology is an important prognostic factor, along with age and mitosis-karyorrhexis index (MKI). This pathology classification system describes "favorable" and "unfavorable" tumors by the International Neuroblastoma Pathology Committee (INPC, also called Shimada system) which was established in 1999 and revised in 2003.
Although international agreement on staging (INSS) has been used, the need for an international consensus on risk assignment has also been recognized in order to compare similar cohorts in results of studies. Beginning in 2005, representatives of the major pediatric oncology cooperative groups have met to review data for 8,800 neuroblastoma patients treated in Europe, Japan, USA, Canada, and Australia between 1990 and 2002. This task force has proposed the International Neuroblastoma Risk Group (INRG) classification system. Retrospective studies revealed the high survival rate of 12-18 month old age group, previously categorized as high-risk, and prompted the decision to reclassify 12-18 month old children without MYCN amplification to intermediate risk category.
The new INRG risk assignment will classify neuroblastoma at diagnosis based on a new International Neuroblastoma Risk Group Staging System (INRGSS):
The new risk stratification will be based on the new INRGSS staging system, age (dichotomized at 18 months), tumor grade, MYCN amplification, unbalanced 11q aberration, and ploidy into four pre-treatment risk groups: very low, low, intermediate, and high risk.
Biologic and genetic characteristics have been identified, which, when added to classic clinical staging, has allowed patient assignment to risk groups for planning treatment intensity. These criteria include the age of the patient, extent of disease spread, microscopic appearance, and several other biological features, most importantly MYCN oncogene amplification (MYCN regulates microRNAs), into low, intermediate, and high risk disease. A recent biology study (COG ANBL00B1) analyzed 2687 neuroblastoma patients and the spectrum of risk assignment was determined: 37% of neuroblastoma cases are low risk, 18% are intermediate risk, and 45% are high risk. (There is some evidence that the high- and low-risk types are caused by different mechanisms, and are not merely two different degrees of expression of the same mechanism.)
The therapy for these different risk categories is very different.
With current treatments, patients with low and intermediate risk disease have an excellent prognosis with cure rates above 90% for low risk and 70%-90% for intermediate risk. In contrast, therapy for high-risk neuroblastoma results in cures only about 30% of the time.
Chemotherapy agents used in combination have been found to be effective against neuroblastoma. Agents commonly used in induction and for stem cell transplant conditioning are platinum compounds (cisplatin, carboplatin), alkylating agents (cyclophosphamide, ifosfamide, melphalan), topoisomerase II inhibitor (etoposide), anthracycline antibiotics (doxorubicin) and vinca alkaloids (vincristine). Some newer regimens include topoisomerase I inhibitors (topotecan and irinotecan) in induction which have been found to be effective against recurrent disease.
By contrast, focus the past 20 years or more has been to intensify treatment for high-risk neuroblastoma. Chemotherapy induction variations, timing of surgery, stem cell transplant regimens, various delivery schemes for radiation, and use of monoclonal antibodies and retinoids to treat minimal residual disease continue to be examined. Recent phase III clinical trials with randomization have been carried out to answer these questions to improve survival of high-risk disease:
In addition to these phase III studies, research institutions such as Baylor College of Medicine/Texas Children's, St. Jude Children's Research Hospital (Memphis, Tennessee), and Memorial Sloan-Kettering Cancer Center in New York offer unique treatment protocols. Texas Children's uses a novel induction regimen which includes a method of giving chemotherapy called “chemo-switching” where cisplatin is given as high-dose pulse and etoposide is given at low-dose over several weeks for the first two cycles. St Jude's recently finished (2007) testing a new up-front chemotherapy regimen in 23 children which included irinotecan and gefitinib with 16 months of maintenance chemotherapy after stem cell transplant with alternating oral 13-cis-retinoic acid and topotecan. Sloan-Kettering offers treatment that includes a mouse-derived monoclonal antibody, 3F8, used in protocols since the mid 1980s. This antibody is used for treating minimal residual disease or consolidation instead of stem cell transplant.
Topotecan with cyclophosphamide is frequently used in refractory setting and after relapse. A randomized study (2004) with 119 patients (comparing topotecan alone to topotecan and cyclophosphamide) revealed a 31% complete or partial response rate with two-year progression-free survival at 36% in the topotecan and cyclophosphamide group. Irinotecan (intravenous or oral) and oral temozolomide are also used in refractory and recurrent neuroblastoma.
Many phase I and phase II trials are currently testing new agents against neuroblastoma in children who have relapsed or are resistant to initial therapy. Investigators are studying targeted therapy, anti-angiogenesis agents, and new monoclonal antibodies such as hu14.18-IL2.
In November 2006, DRAXIS Health received approval from the U.S. Food and Drug Administration (FDA) to run two clinical trials using radioactive Iobenguane I-131 Injection (I-131 MIBG) to treat high-risk neuroblastoma and in May 2008 Molecular Insight Pharmaceuticals announced the opening of a Phase IIa trial of Azedra, the I-131 MIBG molecule radiolabeled using Molecular Insight's proprietary Ultratrace technology, which removes unnecessary nonradioactive molecules, effectively concentrating radiation in the neuroblastoma tumor cells. These trials are coordinated by a group of 11 children’s hospitals and two universities in the United States known as the New Advances in Neuroblastoma Therapy (NANT) consortium, and are continuations of earlier NANT studies. The NANT consortium is also currently offering trials using a tyrosine kinase inhibitor CEP-701 (lestaurtinib), new oral powder formulation of fenretinide, intravenous fenretinide, and bisphosphonate (Zometa). In February 2007, a study in Sweden reported that a common painkiller, might inhibit the development of neuroblastoma and help make treatment of the disease more effective. Celecoxib, an analgesic, anti-inflammatory substance that works by inhibiting the effect of the inflammatory enzyme, Cox-2, and thus could affect neuroblastoma tumors, which depend on Cox-2 for their growth and proliferation. Clinical studies are now planned; research to date has been done only in animals and cell cultures.
Most long-term survivors alive today had low or intermediate risk disease and milder courses of treatment compared to high-risk disease. The majority of survivors have long-term effects from the treatment. Survivors of intermediate and high-risk treatment often experience hearing loss. Growth reduction, thyroid function disorders, learning difficulties, and greater risk of secondary cancers affect survivors of high-risk disease. An estimated two of three survivors of childhood cancer will ultimately develop at least one chronic and sometimes life-threatening health problem within 20 to 30 years after the cancer diagnosis.
The protein p53 is believed to play a role in the development of resistance to chemotherapy.
New neuroblastoma therapy study results reported from Cincinnati Children's Hospital, Department of Radiology.(Report)
Feb 23, 2010; Current study results from the report, '123I-MIBG scintigraphy and 18F-FDG PET in Neuroblastoma,' have been published....