Current Management of Neuroblastoma

Radiation Safety Aspects of Iodine-131 metaiodobenzylguanidine (131I mIBG) Therapy Program Startup

As a medical center without a pre-existing radiopharmaceutical therapy program, it was a daunting endeavor to implement a I metaiodobenzylguanidine (mIBG) high-dose treatment regimen. It took several years of planning with hospital administration, vendors, and Texas Department of Health Radiological Control regulators to establish a viable program. Effective communication between physicians, nursing, nuclear medicine, environmental services, maintenance, and other support staff is essential and paramount for the successful execution and continued sustainability of the mIBG therapy program. Besides providing an effective treatment for patients, an additional goal for the program is to keep radiation exposure As Low As Reasonably Achievable (ALARA) for staff and patient caregivers. As such, start-up presented many training, logistical, and radiation safety challenges. The location of the isolation room and shielding specifications were designed to keep radiation exposure to public access areas to less than 2 microsieverts per hour. Before the first patient was treated the policies and procedures for training, radiation safety, product quality control, and infusion process needed to be developed, tested, and approved by various committees. Furthermore, a similar process was required for developing room set-up, post therapy cleanup, and waste storage procedures. Throughout the maturation process of the program, the departments involved have found that our safety culture has continually improved by the re-enforcement of knowledge and lessons learned, as both the ancillary and treatment staff grew more confident in each other's ability during more patient treatments are performed. This article describes the process and lessons learned during the time leading up to the startup and early years of the mIBG therapy program.

FTY-720 induces apoptosis in neuroblastoma via multiple signaling pathways

Neuroblastoma (NB) is the most common extra-cranial pediatric solid tumor. High-risk NB is difficult to treat due to the lack of response to current therapies and aggressive disease progression. Despite novel drugs, alternative treatments and multi-modal treatments, finding an effective treatment strategy for these patients continues to be a major challenge. The current study focuses on examining the effects of FTY-720 or fingolimod, a drug that is FDA-approved for refractory multiple sclerosis, in NB. The results showed that FTY-720 regulates multiple pathways that result in various effects on calcium signaling, ion channel activation and cell survival/death pathways. FTY-720 rapidly inhibits TRPM7 channel activity, and inhibited TRPM7 kinase activity, modulates calcium signaling, induces a loss of mitochondrial membrane potential and opening of the mitochondrial permeability transition pore, and ultimately leads to cell death. Interestingly, the data also showed that low concentrations of FTY-720 sensitized drug-resistant NB cells to antineoplastic drugs. These results suggest that FTY-720 may be an attractive alternative for the treatment of NB.

Rare orbitocranial tumour in an adult

A 35-year-old lady presented with recurrent episodes of painful right upper lid swelling and ptosis of 6 months' duration. The symptoms would subside with oral antibiotics and painkillers. She had also been undergoing treatment for 1 year for multiple painful osteolytic lesions in the long bones and axial skeleton for which no definite diagnosis had been made, despite several radiological and serological investigations having been performed. Computed tomographic scan showed a soft tissue lesion in the superolateral part of the right orbit with erosion of the adjacent bone. Lacrimal gland biopsy showed non-specific inflammatory changes. She was referred for full work-up to exclude lymphoma and metastasis. Magnetic resonance imaging revealed an enhancing soft tissue mass in the right anterior cranial fossa eroding the lateral orbital wall and extending into the orbit. Another mass encased the superior sagittal sinus. Bone marrow biopsy showed near total replacement of marrow cells by a round cell tumour. Immunohistochemical studies revealed that the tumour cells expressed neuron specific enolase and chromogranin. The pathological findings suggested a diagnosis of neuroendocrine tumour though neuroblastoma could not be unequivocally ruled out. A(131) I-metaiodobenzylguanidine scan showed no uptake. Radiologic studies suggested multiple bony metastases. No other site of primary tumour was found so there was a strong possibility of it being a primary orbito-cranial neurogenic tumour. Neuroblastomas and neuroendocrine tumours are very rare in adults. The orbit is an unusual site for a primary of this nature. In addition, it is quite difficult to make a specific diagnosis in a less differentiated tumour.

Regression of orthotopic neuroblastoma in mice by targeting the endothelial and tumor cell compartments

BACKGROUND

High-risk neuroblastoma has an overall five-year survival of less than 40%, indicating a need for new treatment strategies such as angiogenesis inhibition. Recent studies have shown that chemotherapeutic drugs can inhibit angiogenesis if administered in a continuous schedule. The aim of this study was primarily to characterize tumor spread in an orthotopic, metastatic model for aggressive, MYCN-amplified neuroblastoma and secondarily to study the effects of daily administration of the chemotherapeutic agent CHS 828 on tumor angiogenesis, tumor growth, and spread.

METHODS

MYCN-amplified human neuroblastoma cells (IMR-32, 2 x 10(6)) were injected into the left adrenal gland in SCID mice through a flank incision. Nine weeks later, a new laparotomy was performed to confirm tumor establishment and to estimate tumor volume. Animals were randomized to either treatment with CHS 828 (20 mg/kg/day; p.o.) or vehicle control. Differences between groups in tumor volume were analyzed by Mann-Whitney U test and in metastatic spread using Fisher's exact test. Differences with p < 0.05 were considered statistically significant.

RESULTS

The orthotopic model resembled clinical neuroblastoma in respect to tumor site, growth and spread. Treatment with CHS 828 resulted in tumor regression (p < 0.001) and reduction in viable tumor fraction (p < 0.001) and metastatic spread (p < 0.05) in correlation with reduced plasma levels of the putative tumor marker chromogranin A (p < 0.001). These effects were due to increased tumor cell death and reduced angiogenesis. No treatment-related toxicities were observed.

CONCLUSION

The metastatic animal model in this study resembled clinical neuroblastoma and is therefore clinically relevant for examining new treatment strategies for this malignancy. Our results indicate that daily scheduling of CHS 828 may be beneficial in treating patients with high-risk neuroblastoma.

Rare orbitocranial tumour in an adult

A 35-year-old lady presented with recurrent episodes of painful right upper lid swelling and ptosis of 6 months' duration. The symptoms would subside with oral antibiotics and painkillers. She had also been undergoing treatment for one year for multiple painful osteolytic lesions in the long bones and axial skeleton for which no definite diagnosis had been made, despite several radiological and serological investigations having been performed. Computed tomographic scan showed a soft tissue lesion in the superolateral part of the right orbit with erosion of the adjacent bone. Lacrimal gland biopsy showed non-specific inflammatory changes. She was referred for full work-up to exclude lymphoma and metastasis. Magnetic resonance imaging revealed an enhancing soft tissue mass in the right anterior cranial fossa eroding the lateral orbital wall and extending into the orbit. Another mass encased the superior sagittal sinus. Bone marrow biopsy showed near total replacement of marrow cells by a round cell tumour. Immunohistochemical studies revealed that the tumour cells expressed neuron specific enolase and chromogranin. The pathological findings suggested a diagnosis of neuroendocrine tumour though neuroblastoma could not be unequivocally ruled out. (131) I-metaiodobenzylguanidine scan showed no uptake. Radiologic studies suggested multiple bony metastases. No other site of primary tumour was found so there was a strong possibility of it being a primary orbito-cranial neurogenic tumour. Neuroblastomas and neuroendocrine tumours are very rare in adults. The orbit is an unusual site for a primary of this nature. In addition, it is quite difficult to make a specific diagnosis in a less differentiated tumour.

Radiation quality-dependent bystander effects elicited by targeted radionuclides

The efficacy of radiotherapy may be partly dependent on indirect effects, which can sterilise malignant cells that are not directly irradiated. However, little is known of the influence of these effects in targeted radionuclide treatment of cancer. We determined bystander responses generated by the uptake of radioiodinated iododeoxyuridine ([*I]IUdR) and radiohaloanalogues of meta-iodobenzylguanidine ([*I]MIBG) by noradrenaline transporter (NAT) gene-transfected tumour cells. NAT specifically accumulates MIBG. Multicellular spheroids that consisted of 5% of NAT-expressing cells, capable of the active uptake of radiopharmaceutical, were sterilised by treatment with 20 kBqmL(-1) of the alpha-emitter meta-[211At]astatobenzylguanidine ([211At]MABG). Similarly, in nude mice, retardation of the growth of tumour xenografts containing 5% NAT-positivity was observed after treatment with [131I]MIBG. To determine the effect of subcellular localisation of radiolabelled drugs, we compared the bystander effects resulting from the intracellular concentration of [131I]MIBG and [131I]IUdR (low linear energy transfer (LET) beta-emitters) as well as [123I]MIBG and [123I]IUdR (high LET Auger electron emitters). [*I]IUdR is incorporated in DNA whereas [*I]MIBG accumulates in extranuclear sites. Cells exposed to media from [131I]MIBG- or [131I]IUdR-treated cells demonstrated a dose-response relationship with respect to clonogenic cell death. In contrast, cells receiving media from cultures treated with [123I]MIBG or [123I]IUdR exhibited dose-dependent toxicity at low dose but elimination of cytotoxicity with increasing radiation dose (i.e. U-shaped survival curves). Therefore radionuclides emitting high LET radiation may elicit toxic or protective effects on neighbouring untargeted cells at low and high dose respectively. It is concluded that radiopharmaceutical-induced bystander effects may depend on LET of the decay particles but are independent of site of intracellular concentration of radionuclide.

Studies on the anti-tumor activities of the soy isoflavone daidzein on murine neuroblastoma cells

Daidzein (4',7-dihydroxyisoflavone) and genistein (4',5,7-trihydroxyisoflavone) are two major isoflavones found predominantly in soy beans, as well as in certain traditional Chinese medicinal herbs and tea leaves. In the past decade, there have been extensive studies on the anti-tumor effects of genistein on cancers of the breast, prostate and colon in humans. However, the anti-tumor effects of daidzein on neuronal cancer cells and its action mechanisms remain poorly understood. In this study, daidzein was shown to inhibit the proliferation of a number of murine and human neuroblastoma cell lines in vitro. Using the murine neuroblastoma Neuro-2a (BU-1) cells as the cell model, daidzein was also found to prevent the cell cycle progression to G2/M phase and induced apoptosis of the neuronal tumor cells, as measured by flow cytometry and gel electrophoresis for fragmented DNA respectively. Taken together, our results showed that daidzein could exert pleiotropic effects on the murine neuroblastoma cells, including inhibition of cell proliferation, modulation of cell cycle check point regulation, and triggering of neuronal cell apoptosis.

Targeted radiotherapy: microgray doses and the bystander effect

Indirect effects may contribute to the efficacy of radiotherapy by sterilizing malignant cells that are not directly irradiated. However, little is known of the influence of indirect effects in targeted radionuclide treatment. We compared gamma-radiation-induced bystander effects with those resulting from exposure to three radiohaloanalogues of meta-iodoben-zylguanidine (MIBG): [(131)I]MIBG (low linear energy transfer (LET) alpha-emitter), [(123)I]MIBG (high LET Auger electron emitter), and meta-[(211)At]astatobenzylguanidine ([(211)At]MABG) (high LET alpha-emitter). Cells exposed to media from gamma-irradiated cells exhibited a dose-dependent reduction in survival fraction at low dosage and a plateau in cell kill at > 2 Gy. Cells treated with media from [(131)I]MIBG demonstrated a dose-response relationship with respect to clonogenic cell death and no annihilation of this effect at high radiopharmaceutical dosage. In contrast, cells receiving media from cultures treated with [(211)At]MABG or [(123)I]MIBG exhibited dose-dependent toxicity at low dose but elimination of cytotoxicity with increasing radiation dose (i.e. U-shaped survival curves). Therefore radionuclides emitting high LET radiation may elicit toxic or protective effects on neighboring untargeted cells at low and high dose respectively. We conclude that radiopharmaceutical-induced bystander effects may depend on LET and be distinct from those elicited by conventional radiotherapy.

[131I]MIBG and topotecan: a rationale for combination therapy for neuroblastoma

MIBG is selectively concentrated in neuroblastoma cells, and radioiodinated MIBG has been used with some success for targeted radiotherapy. However, long-term cure remains elusive, and the topoisomerase I inhibitor topotecan may improve upon existing [131I]MIBG therapy. While synergistic killing by combinations of ionising radiation and topoisomerase I inhibitors has been reported, there is no consensus on optimal scheduling. Furthermore, there has been no attempt to demonstrate radio-potentiation by topoisomerase I inhibitors and targeted radiotherapy. We are investigating various scheduled combinations of topotecan and [131I]MIBG on neuroblastoma cells, and preliminary data suggests that topotecan induces increased accumulation of [131I]MIBG in vitro.

Neuroblastoma: Management, recurrence, and follow-up

The clinical use of N-myc amplification in neuroblastoma management has served as a paradigm for "bench to bedside" medicine. It is hoped that the quest for molecular markers such as neurotrophin, TrkA, and TrkB will continue to advance the understanding of neuroblastoma. In addition, animal models of neuroblastoma (N-myc transgenic mice, and neuroblastoma xenografts) have been established to assess the efficacy of novel treatments. These advances are likely to improve clinical practice in the future.

Human megakaryocytes cultured in vitro accumulate serotonin but not meta-iodobenzylguanidine whereas platelets concentrate both

OBJECTIVE

Thrombocytopenia is the major toxicity of radio-iodinated meta-iodobenzylguanidine (MIBG) therapy in patients with recurrent neuroblastoma. MIBG is taken up in platelets via the serotonin transporter. Given the delayed appearance and long duration of the thrombocytopenia, it seems likely that the precursor megakaryocytes are the primary targets of [131I]MIBG radiotoxicity.

MATERIALS AND METHODS

We investigated MIBG and serotonin uptake in cultured human megakaryocytes grown in vitro from CD34(+) cells obtained from bone marrow.

RESULTS

With radio-iodinated MIBG, cell-associated radioactivity was negligible, even after prolonged incubations for up to 16 hours. In contrast, after 4 or 16 hours with 10(-8) M [3H]serotonin, 6% or 14% of the added substrate was accumulated in the megakaryocytes. This uptake approached saturation above 10(-7) M and was reduced greater than 90% by coincubation by imipramine. This indicates specific uptake, which was confirmed by fluvoxamine and citalopram. The serotonin reuptake inhibitors fluvoxamine (0.3 nM) and citalopram (1 nM) effectively reduced serotonin uptake to 44% +/- 3% and 30% +/- 9% of the controls, respectively.

CONCLUSIONS

Megakaryocytes efficiently retain serotonin in storage granules, as concluded from the consistent reductive effect of tetrabenazine on uptake, retention, and localization (micro-autoradiographic) of serotonin. Thus, serotonin, but not MIBG, is taken up by cultured megakaryocytes.