Role of 131I-metaiodobenzylguanidine in the treatment of neuroblastoma

Timing and chemotherapy association for 131-I-MIBG treatment in high-risk neuroblastoma

Prognosis of high-risk neuroblastoma is dismal, despite intensive induction chemotherapy, surgery, high-dose chemotherapy, radiotherapy, and maintenance. Patients who do not achieve a complete metastatic response, with clearance of bone marrow and skeletal NB infiltration, after induction have a significantly lowersurvival rate. Thus, it's necessary to further intensifytreatment during this phase. 131-I-metaiodobenzylguanidine (131-I-MIBG) is a radioactive compound highly effective against neuroblastoma, with32% response rate in relapsed/resistant cases, and only hematological toxicity. 131-I-MIBG wasutilized at different doses in single or multiple administrations, before autologous transplant or combinedwith high-dose chemotherapy. Subsequently, it was added to consolidationin patients with advanced NB after induction, but an independent contribution against neuroblastoma and for myelotoxicity is difficult to determine. Despiteresults of a 2008 paper demonstratedefficacy and mild hematological toxicity of 131-I-MIBG at diagnosis, no center had included it with intensive chemotherapy in first-line treatment protocols. In our institution, at diagnosis, 131-I-MIBG was included in a 5-chemotherapy drug combination and administered on day-10, at doses up to 18.3 mCi/kg. Almost 87% of objective responses were observed 50 days from start with acceptable hematological toxicity. In this paper, we review the literature data regarding 131-I-MIBG treatment for neuroblastoma, and report on doses and combinations used, tumor responses and toxicity. 131-I-MIBG is very effective against neuroblastoma, in particular if given to patients at diagnosis and in combination with chemotherapy, and it should be included in all induction regimens to improve early responses rates and consequently long-term survival.

Induction Regimen in High-Risk Neuroblastoma: A Pilot Study of Highly Effective Continuous Exposure of Tumor Cells to Radio-Chemotherapy Sequence for 1 Month. The Critical Role of Iodine-131-Metaiodobenzylguanidine

The prognosis of high-risk neuroblastoma (NB) continues to be poor. The early development of resistance often leads to disease recurrence. In the present study, an innovative induction regimen, including an intensive initial radio-chemotherapy sequence based on the use of iodine-131-metaiodobenzylguanidine (131-I-MIBG), was investigated. The duration of the regimen lasted only one month. Fifteen newly diagnosed patients aged >18 months with high-risk NB were treated with cisplatin, etoposide, cyclophosphamide, and vincristine, followed on day 10 by 131-I-MIBG (dose: 12−18.3 mCi/kg). Cisplatin and vincristine were administered on day 20 and 21 followed by the re-administration of vincristine, cyclophosphamide, and doxorubicin on day 29 and 30. Non-hematologic toxicity was not observed. Moderate hematologic toxicity was present probably attributable to chemotherapy. The evaluation of response was performed approximately 50 days after the initiation of treatment, yielding four complete responses, eight very good partial responses, one partial response, and two non-responses. Importantly, a complete metastatic response was achieved in 87% of patients. The present pilot study, which includes 131-I-MIBG, allows for a highly effective continuous exposure of tumor cells to both chemotherapy and radiotherapy. Furthermore, early high-dose chemotherapy followed by stem cell rescue may achieve high levels of tumor cell clearance and improve the prognosis of high-risk NB.

Draft guidelines regarding appropriate use of (131)I-MIBG radiotherapy for neuroendocrine tumors : Guideline Drafting Committee for Radiotherapy with (131)I-MIBG, Committee for Nuclear Oncology and Immunology, The Japanese Society of Nuclear Medicine

Since the 1980s when clinical therapeutic trials were initiated, (131)I-MIBG radiotherapy has been used in foreign countries for unresectable neuroendocrine tumors including malignant pheochromocytomas and neuroblastomas. In Japan, (131)I-MIBG radiotherapy has not been approved by the Ministry of Health, Labour and Welfare; however, personally imported (131)I-MIBG is now available for therapeutic purposes in a limited number of institutions. These updated draft guidelines aim to provide useful information concerning (131)I-MIBG radiotherapy, to help prevent side effects and protect physicians, nurses, other health care professionals, patients and their families from radiation exposure. The committee has also provided appendices on topics such as practical guidance for attending physicians, patient management, and referring physicians.

Dosimetry study of [I-131] and [I-125]- meta-iodobenz guanidine in a simulating model for neuroblastoma metastasis

The physical properties of I-131 may be suboptimal for the delivery of therapeutic radiation to bone marrow metastases, which are common in the natural history of neuroblastoma. In vitro and preliminary clinical studies have implied improved efficacy of I-125 relative to I-131 in certain clinical situations, although areas of uncertainty remain regarding intratumoral dosimetry. This prompted our study using human neuroblastoma multicellular spheroids as a model of metastasis. 3D dose calculations were made using voxel-based Medical Internal Radiation Dosimetry (MIRD) and dose-point-kernel (DPK) techniques. Dose distributions for I-131 and I-125 labeled mIBG were calculated for spheroids (metastases) of various sizes from 0.01 cm to 3 cm diameter, and the relative dose delivered to the tumors was compared for the same limiting dose to the bone marrow. Based on the same data, arguments were advanced based upon the principles of tumor control probability (TCP) to emphasize the potential theoretical utility of I-125 over I-131 in specific clinical situations. I-125-mIBG can deliver a higher and more uniform dose to tumors compared to I-131 mIBG without increasing the dose to the bone marrow. Depending on the tumor size and biological half-life, the relative dose to tumors of less than 1 mm diameter can increase several-fold. TCP calculations indicate that tumor control increases with increasing administered activity, and that I-125 is more effective than I-131 for tumor diameters of 0.01 cm or less. This study suggests that I-125-mIBG is dosimetrically superior to I-131-mIBG therapy for small bone marrow metastases from neuroblastoma. It is logical to consider adding I-125-mIBG to I-131-mIBG in multi-modality therapy as these two isotopes could be complementary in terms of their cumulative dosimetry.

Treatment of advanced neuroblastoma in children over 1 year of age: the critical role of ¹³¹I-metaiodobenzylguanidine combined with chemotherapy in a rapid induction regimen

BACKGROUND

The prognosis of patients with advanced neuroblastoma (NB) remains poor. Major and early responses have an important bearing on treatment outcome. Iodine-131-metaiodobenzylguanidine (¹³¹I-MIBG) has the potential to deliver large doses of radiation specifically to NB cells. We evaluated the toxicity of, and response to, a novel induction regimen that included ¹³¹I-MIBG combined with cisplatin, cyclophosphamide, etoposide, vincristine, and doxorubicin.

PROCEDURE

Thirteen children over 1 year of age with advanced NB at diagnosis were investigated extensively. ¹³¹I-MIBG was administered on day 10; this was preceded by chemotherapy in the five patients in group 1 (described in our previous study), and both preceded and followed by chemotherapy in the eight patients in group 2. The final induction regimen (used for group 2) lasted 1 month. Evaluation was performed 40 days after the start of treatment.

RESULTS

In both groups 1 and 2, the extent of hematologic toxicity, which was the only side effect, was similar to that seen with chemotherapy alone. Doses of ¹³¹I-MIBG as high as 16.6 mCi/kg showed no evidence of toxicity, even in patients with extensive bone marrow infiltration. Overall, we recorded two patients with a complete response (CR), six very good partial responses (VGPR), four partial responses (PR), and one mixed response (MR). In group 2, CR/VGPR were observed in patients treated with higher doses of ¹³¹I-MIBG.

CONCLUSIONS

The results of this pilot study show that ¹³¹I-MIBG, in combination with chemotherapy, appears to play an important role in a new and effective induction regimen for advanced NB.

Dosimetry for 131I-MIBG therapies in metastatic neuroblastoma, phaeochromocytoma and paraganglioma

PURPOSE

Radiation dosimetry is a basic requirement for targeted radionuclide therapies (TRT) which have become of increasing interest in nuclear medicine. Despite the significant role of the radiopharmaceutical (131)I-metaiodobenzylguanidine (MIBG) for the treatment of metastatic neuroblastoma, phaeochromocytoma and paraganglioma details for a reliable dosimetry are still sparse. This work presents our procedures, the dosimetric data and experiences with TRT using (131)I-MIBG.

METHODS

A total of 21 patients were treated with (131)I-MIBG between 2004 and 2008 according to a clearly defined protocol. Whole-body absorbed doses were determined by a series of scintillation probe readings for all 21 cases. Tumour absorbed doses were calculated on the basis of quantitative imaging for an entity of 25 lesions investigated individually using the region of interest (ROI) technique based on five scans each.

RESULTS

Typical whole-body absorbed doses are found in the region of 2 Gy (range: 1.0-2.9 Gy) whereas tumour absorbed doses in turn cover a span between 10 and 60 Gy. Nonetheless this variation of tumour absorbed doses is comparatively low.

CONCLUSION

The trial protocol in use is a substantial advancement in terms of reliable dosimetry. A clearly defined modus operandi for MIBG therapies should involve precisely described dosimetric procedures, e.g. a minimum of 20 whole-body measurements using a calibrated counter and at least four gamma camera scans over the whole period of the inpatient stay should be carried out. Calculation of tumour volumes is accomplished best via evaluation of SPECT and CT images.

Hematologic Toxicity of High-Dose Iodine-131–Metaiodobenzylguanidine Therapy for Advanced Neuroblastoma

Purpose

Iodine-131–metaiodobenzylguanidine (131I-MIBG) has been shown to be active against refractory neuroblastoma. The primary toxicity of 131I-MIBG is myelosuppression, which might necessitate autologous hematopoietic stem-cell transplantation (AHSCT). The goal of this study was to determine risk factors for myelosuppression and the need for AHSCT after 131I-MIBG treatment.

Patients and Methods

Fifty-three patients with refractory or relapsed neuroblastoma were treated with 18 mCi/kg 131I-MIBG on a phase I/II protocol. The median whole-body radiation dose was 2.92 Gy.

Results

Almost all patients required at least one platelet (96%) or red cell (91%) transfusion and most patients (79%) developed neutropenia (< 0.5 × 103/μL). Patients reached platelet nadir earlier than neutrophil nadir (P < .0001). Earlier platelet nadir correlated with bone marrow tumor, more extensive bone involvement, higher whole-body radiation dose, and longer time from diagnosis to 131I-MIBG therapy (P ≤ .04). In patients who did not require AHSCT, bone marrow disease predicted longer periods of neutropenia and platelet transfusion dependence (P ≤ .03). Nineteen patients (36%) received AHSCT for prolonged myelosuppression. Of patients who received AHSCT, 100% recovered neutrophils, 73% recovered red cells, and 60% recovered platelets. Failure to recover red cells or platelets correlated with higher whole-body radiation dose (P ≤ .04).

Conclusion

These results demonstrate the substantial hematotoxicity associated with high-dose 131I-MIBG therapy, with severe thrombocytopenia an early and nearly universal finding. Bone marrow tumor at time of treatment was the most useful predictor of hematotoxicity, whereas whole-body radiation dose was the most useful predictor of failure to recover platelets after AHSCT.

Biodistribution of post-therapeutic versus diagnostic (131)I-MIBG scans in children with neuroblastoma

BACKGROUND

To evaluate the biodistribution of therapeutic (131)I-metaiodobenzylguanidine (MIBG) and assess the sensitivity of diagnostic versus therapeutic (131)I-MIBG scans to detect metastatic disease.

PROCEDURE

This retrospective study included 44 diagnostic and post-therapy scans (PTS) in 18 children with neuroblastoma treated with (131)I-MIBG (2.0-33.1 GBq). The findings of diagnostic scans (DS) (2.6-44.4 MBq) were compared to those of corresponding PTS.

RESULTS

In terms of biodistribution, the PTS identified (131)I-MIBG activity in one or more patients in the following regions not detected on the DS: nasal mucosa, cerebellum, central brain, adrenals, spleen, kidneys, thyroid, salivary glands, lower halves of the lungs, bladder, bowel, and an incisional scar. Conversely, the DS identified activity in the thorax, heart, kidneys, and bladder each in one patient without being visualized on the PTS. In terms of sensitivity to detect metastatic disease, 210 lesions were seen on the PTS compared to 151 on the DS. The PTS demonstrated sites of disease not evident in the DS in 16 cases.

CONCLUSIONS

The biodistribution of (131)I-MIBG is different using therapeutic doses as compared to pre-therapy doses. (131)I-MIBG imaging following high therapeutic doses often reveals sites of occult metastatic disease that may be clinically relevant.

Second malignancies in children with neuroblastoma after combined treatment with 131I-metaiodobenzylguanidine

BACKGROUND

(131)I-metaiodobenzylguanidine ((131)I-MIBG) is selectively taken up by cells of neural crest origin, allowing targeted radiotherapy of tumors such as neuroblastoma (NB) and pheochromocytoma. Radiotherapy may provide additional benefits in the treatment of NB, with moderate side effects such as hematologic and thyroid toxicity. However, with longer follow-up, other complications might occur. We describe our experience with second cancers occurring in children treated with (131)I-MIBG and chemotherapy.

METHODS

The clinical records of 119 consecutive NB cases treated with (131)I-MIBG at a single institution between 1984 and 2001 were reviewed for the occurrence of a second malignant neoplasm (SMN).

RESULTS

Overall, five cases of SMN occurred in the study patients. In particular, two cases of myeloid leukemia, one of angiomatous fibrous histiocytoma, one of malignant schwannoma, and one case of rhabdomyosarcoma were detected. The schwannoma and the rhabdomyosarcoma developed within the residual neuroblastic mass after first-line therapy.

CONCLUSIONS

Should (131)I-MIBG treatment become more broadly employed in the therapeutic strategy for neuroblastoma, the risk of second cancer will have to be taken into consideration. The organization of an international registry of subjects treated with (131)I-MIBG might better define the frequency and features of second malignancies following this radiometabolic approach.

Malignant abdominal masses in children: quick guide to evaluation and diagnosis

A palpable mass in the abdomen of a child is a serious finding. In this article the authors present their single-institution experience of how these malignancies present and their distribution by age and diagnosis. The most common abdominal malignancies diagnosed in the pediatric population include neuroblastoma, Wilms' tumor, hepatoblastoma, lymphoma, and germ cell tumors. This article provides the busy general pediatrician with some guidelines of how to proceed after discovering a suspiciousmass.

Novel techniques in the delivery of radiation in pediatric oncology

The field of radiation oncology continues to develop at a rapid pace, due to concurrent progress in high speed computing, improved sensitivity in diagnostic imaging (both anatomic and physiologic), and the introduction of rational new therapeutics built on solid radiobiologic principles. These innovations will become critically important in the field of pediatric oncology, as they will allow for an increased therapeutic ratio in the developing child. Maximizing the benefit of lower dose radiation through the use of radiation modifiers (hypoxic cell sensitizers, signal transduction pathway inhibitors, concurrent chemotherapy), increasing the tolerance of normal tissues (radioprotectors) and tailoring the target area more closely to the desired critical tissues (IMRT, functional simulation with PET and MRS, radiolabeled monoclonal antibodies) will lessen the short and long term toxicity of radiation and increase its effectiveness.

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.

Hyperfractionated low-dose radiotherapy for high-risk neuroblastoma after intensive chemotherapy and surgery

PURPOSE

To assess prognostic factors for local control in high-risk neuroblastoma patients treated with hyperfractionated 21-Gy total dose to consolidate remission achieved by dose-intensive chemotherapy and surgery.

PATIENTS AND METHODS

Patients with high-risk neuroblastoma in first remission received local radiotherapy (RT) totaling 21 Gy in twice-daily 1.5-Gy fractions. RT to the primary site followed dose-intensive chemotherapy and tumor resection; the target field encompassed the extent of tumor at diagnosis, plus 3-cm margins and regional lymph nodes. RT to distant sites followed radiologic evidence of response. Local failure was correlated with clinical factors (including other consolidative treatments) and biologic findings.

RESULTS

Of 99 consecutively irradiated patients followed for a median of 21.1 months from RT, 10 relapsed in or at margins of RT fields at 1 to 27 months (median, 14 months). At 36 months after RT, the probability of primary-site failure was 10.1% +/- 5.3%. No primary-site relapses occurred among the 23 patients whose tumors were excised at diagnosis, but there were three such relapses among the seven patients who were irradiated with evidence of residual disease in the primary site. Four of 18 patients with MYCN-amplified disease and serum lactate dehydrogenase greater than 1,500 U/L had local failures (23.4% +/- 10.7% risk at 18 months). Acute radiotoxicities were insignificant, but three of 35 patients followed for > or = 36 months had short stature from decreased growth of irradiated vertebra.

CONCLUSION

Hyperfractionated 21-Gy RT is well tolerated and, together with dose-intensive chemotherapy and surgery, may help in local control of high-risk neuroblastoma. Extending the RT field to definitively encompass regional nodal groups may improve results. Visible residual disease may warrant higher RT dosing. Patients with biologically unfavorable disease may be at increased risk for local failure. RT to the primary site may not be necessary when tumors are excised at diagnosis.

Angiomatoid (malignant) fibrous histiocytoma as a second tumour in a child with neuroblastoma

Neuroblastoma occurring as a disseminated disease in children has a poor prognosis. Haematogenous metastases usually involve the marrow, bone, liver and skin. A second neoplasm may also develop. We describe a child with retroperitoneal neuroblastoma (stage 3) who developed a nodular mass in the inguinal area which was suspected to be a metastasis. Histopathology disclosed an angiomatoid (malignant) fibrous histiocytoma, and excision was curative. The occurrence of angiomatoid (malignant) fibrous histiocytoma as a second tumour in a patient with neuroblastoma has not previously been reported.

131I-metaiodobenzylguanidine (131I-MIBG) therapy for residual neuroblastoma: a mono-institutional experience with 43 patients

Incomplete response to therapy may compromise the outcome of children with advanced neuroblastoma. In an attempt to improve tumour response we incorporated 131I-metaiodobenzylguanidine (131I-MIBG) in the treatment regimens of selected stage 3 and stage 4 patients. Between 1986 and 1997, 43 neuroblastoma patients older than 1 year at diagnosis, 13 with stage 3 (group A) and 30 with stage 4 disease (group B) who had completed the first-line protocol without achieving complete response entered in this study. 131I-MIBG dose/course ranged from 2.5 to 5.5 Gbq (median, 3.7). The number of courses ranged from 1 to 5 (median 3) depending on the tumour response and toxicity. The most common acute side-effect was thrombocytopenia. Later side-effects included severe interstitial pneumonia in one patient, acute myeloid leukaemia in two, reduced thyroid reserve in 21. Complete response was documented in one stage 4 patient, partial response in 12 (two stage 3, 10 stage 4), mixed or no response in 25 (ten stage 3, 15 stage 4) and disease progression in five (one stage 3, four stage 4) Twenty-four patients (12/13 stage 3, 12/30 stage 4) are alive at 22-153 months (median, 59) from diagnosis. 131I-MIBG therapy may increase the cure rate of stage 3 and improve the response of stage 4 neuroblastoma patients with residual disease after first-line therapy. A larger number of patients should be treated to confirm these results but logistic problems hamper prospective and coordinated studies. Long-term toxicity can be severe.

131I MIBG therapy in neuroblastoma: mechanisms, rationale, and current status

131I MIBG has been used as palliative treatment of neuroblastoma patients with recurrent or persistent disease who failed other modalities of treatment. Since the results were promising, the concept arose of using it in conjunction with other modalities, either as an up-front treatment or as combination therapy. This article reviews the principle of 131I MIBG treatment, in conjunction with other modalities currently used for the treatment of neuroblastoma, in an attempt to improve the final outcome.