Intrathecal therapy with 198Au-colloid for meningosis prophylaxis

Carcinomatous meningitis: Leptomeningeal metastases in solid tumors

Leptomeningeal metastasis (LM) results from metastatic spread of cancer to the leptomeninges, giving rise to central nervous system dysfunction. Breast cancer, lung cancer, and melanoma are the most frequent causes of LM among solid tumors in adults. An early diagnosis of LM, before fixed neurologic deficits are manifest, permits earlier and potentially more effective treatment, thus leading to a better quality of life in patients so affected. Apart from a clinical suspicion of LM, diagnosis is dependent upon demonstration of cancer in cerebrospinal fluid (CSF) or radiographic manifestations as revealed by neuraxis imaging. Potentially of use, though not commonly employed, today are use of biomarkers and protein profiling in the CSF. Symptomatic treatment is directed at pain including headache, nausea, and vomiting, whereas more specific LM-directed therapies include intra-CSF chemotherapy, systemic chemotherapy, and site-specific radiotherapy. A special emphasis in the review discusses novel agents including targeted therapies, that may be promising in the future management of LM. These new therapies include anti-epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors erlotinib and gefitinib in nonsmall cell lung cancer, anti-HER2 monoclonal antibody trastuzumab in breast cancer, anti-CTLA4 ipilimumab and anti-BRAF tyrosine kinase inhibitors such as vermurafenib in melanoma, and the antivascular endothelial growth factor monoclonal antibody bevacizumab are currently under investigation in patients with LM. Challenges of managing patients with LM are manifold and include determining the appropriate patients for treatment as well as the optimal route of administration of intra-CSF drug therapy.

Dose distribution to spinal structures from intrathecally administered yttrium-90

Previous treatment of cerebrospinal fluid (CSF) malignancies by intrathecal administration of (131)I-radiolabelled monoclonal antibodies has led to the assumption that more healthy tissue will be spared when a pure beta-emitter such as (90)Y replaces (131)I. The purpose of this study is to compare and quantitatively evaluate the dose distribution from (90)Y to the CSF space and its surrounding spinal structures to (131)I. A 3D digital phantom of a section of the T-spine was constructed from the visible human project series of images which included the spinal cord, central canal, subarachnoid space, pia mater, arachnoid, dura mater, vertebral bone marrow and intervertebral disc. Monte Carlo N-particle (MCNP4C) was used to model the (90)Y and (131)I radiation distribution. Images of the CSF compartment were convolved with the radiation distribution to determine the dose within the subarachnoid space and surrounding tissues. (90)Y appears to be a suitable radionuclide in the treatment of central nervous system (CNS) malignancies when attached to mAb's and the dose distribution would be confined largely within the vertebral foramen. This choice may offer favourable dose improvement to the subarachnoid and surface of spinal cord over (131)I in such an application.

Leptomeningeal metastases from solid malignancy: a review

Leptomeningeal metastases (LMM) consist of diffuse involvement of the leptomeninges by infiltrating cancer cells. In solid tumors, the most frequent primary sites are lung and breast cancers, two tumors where the incidence of LMM is apparently increasing. Careful neurological examination is required to demonstrate multifocal involvement of the central nervous system (CNS), cranial nerves, and spinal roots, which constitute the clinical hallmark of the disease. Cerebro-spinal fluid (CSF) analysis is almost always abnormal but only a positive cytology or demonstration of intrathecal synthesis of tumor markers is diagnostic. T1-weighted gadolinium-enhanced sequence of the entire neuraxis (brain and spine) plays an important role in supporting the diagnosis, demonstrating the involved sites and guiding treatment. Radionuclide CSF flow studies detect CSF compartmentalization and are useful for treatment planning. Standard therapy relies mainly on focal irradiation and intrathecal or systemic chemotherapy. Studies using other therapeutic approaches such as new biological or cytotoxic compounds are ongoing. The overall prognosis remains grim and quality of life should remain the priority when deciding which treatment option to apply. However, a sub-group of patients, tentatively defined here, may benefit from an aggressive treatment.

Delayed cerebrovascular complications of intrathecal colloidal gold

OBJECTIVE

Therapy with intrathecal colloidal gold has been used in the past as an adjunct in the treatment of childhood neoplasms, including medulloblastoma and leukemia. We describe the long-term follow-up period of a series of patients treated with intrathecal colloidal gold and emphasize the high incidence of delayed cerebrovascular complications and their management.

METHODS

Between 1967 and 1970, 14 children with posterior fossa medulloblastoma underwent treatment at the University of Minnesota. Treatment consisted of surgical resection, external beam radiotherapy, and intrathecal colloidal gold. All patients underwent long-term follow-up periods.

RESULTS

Of the 14 original patients, 6 died within 2 years of treatment; all experienced persistent or recurrent disease. The eight surviving patients developed significant neurovascular complications 5 to 20 years after treatment. Three patients died as a result of aneurysmal subarachnoid hemorrhage, and five developed ischemic symptoms from severe vasculopathy that resembled moyamoya disease.

CONCLUSION

Although therapy with colloidal gold resulted in long-term survival in a number of cases of childhood medulloblastoma, our experience suggests that the severe cerebrovascular side effects fail to justify its use. The unique complications associated with colloidal gold therapy, as well as the management of these complications, are presented. We recommend routine screening of any long-term survivors to exclude the presence of an intracranial aneurysm and to document the possibility of moyamoya syndrome.

Neoplastic meningitis

Neoplastic meningitis is recognized clinically in 4% to 7% of patients with extraneural cancer, but it remains dramatically under-diagnosed. The frequency of neoplastic meningitis is increasing because of heightened clinical suspicion, improved neuroimaging techniques, and longer survival in patients with extraneural cancer Longer survival allows residual tumor cells within central nervous system sanctuary sites time to become symptomatic. Affected patients may present with cerebral, cranial nerve, or spinal signs and symptoms, depending on the specific sites of central nervous system (CNS) involvement. Magnetic Resonance Imaging (MRI) seems to be sensitive for detecting metastatic deposits along the neuraxis. However, metastases at a microscopic level are below the resolution of MRI scanning. As a result, the standard diagnostic test for neoplastic meningitis remains the cytologic identification of malignant cells in cerebrospinal fluid (CSF). Although CSF cytology is useful, malignant cells are not detected in as many as one third of patients who have compelling clinical or radiographic evidence of neoplastic meningitis. Novel assays are being tested that may enhance the early identification of malignant cells in CSF. Currently, the diagnosis occurs generally after the onset of neurologic manifestations and heralds a rapidly fatal course for most patients. By the time symptoms appear, most tumors have disseminated widely within the CNS, due to cortical irritation, compression of nervous system structures, or obstruction of CSF flow. At this stage surgery, cranial irradiation, and chemotherapy are rarely, if ever, curative. The goals of treatment are to improve or to stabilize the neurologic status of patients and to prolong survival. A major problem in treating neoplastic meningitis is that the entire neuraxis must be treated. If only symptomatic areas are treated, reseeding of the neuraxis with tumor cells will occur. Therefore, intrathecal chemotherapy remains a mainstay of therapy. Currently, four therapeutic agents are available for intrathecal treatment: methotrexate, ara-C, sustained-release ara-C (DepoCyt; Chiron Therapeutics, San Francisco, CA), and thiotepa. Unfortunately, intrathecal chemotherapy does not treat bulky disease in the subarachnoid space, and often is slow to stabilize progressive neurologic deficits. For these reasons, radiation therapy to sites of symptomatic disease and sites of bulky disease on imaging studies is recommended. High dose intravenous methotrexate may be as effective as intrathecal methotrexate. Alternative approaches (which offer less toxicity, enhanced therapeutic effect, and prolonged survival) are being investigated.

Principles of radiotherapy of neoplastic meningosis

Neoplastic meningosis can be a complication of a tumor originating in the brain or the meninges, or it can be a complication of a solid tumor elsewhere that has metastasized to the leptomeninges. The therapeutic dilemma for a radiation oncologist is that neoplastic meningosis involves the entire neuraxis and, as a consequence, ideally, the entire neuraxis should be radiated. However, delivering the necessary radiation dose to the entire neuraxis may be associated with considerable neurologic or bone marrow toxicity. Radiotherapy of neoplastic meningosis can be performed by external beam radiation or by intrathecal injection of radioactive nuclides or radiolabeled monoclonal antibodies. Intrathecal radiation has the theoretical advantage that treatment is directed towards the entire neuraxis with limited irradiation outside the neuraxis. In practice, intrathecal radiation is still under investigation and subject to some limitations and toxicities. Indications and techniques for external beam radiation may range from either therapeutic or elective cranial or craniospinal radiation to palliative involved-field radiation. Patients with neoplastic meningosis are frequently treated with a combination of radiation and chemotherapy, and/or may have been irradiated to the nervous system in the past. Both are well known risk factors for radiation damage to the nervous system. In general, current treatment protocols focus on the development of combination chemotherapy programs and reduction of the radiation dose to minimize toxicity and/or to improve tumor control.

A dosimetric model for intrathecal treatment with 131I and 67Ga

PURPOSE

Calculations were performed of absorbed dose distributions of the beta-emitter 131I and the Auger emitter 67Ga for intrathecal administration.

METHODS AND MATERIALS

The proposed dosimetric model accounts for the macroscopic distribution of the activity, by means of a Medical Internal Radiation Dose Committee approach, and for the microscopic distribution of activity, by means of a point kernel technique. This point kernel approach was used in combination with a distance histogram technique, to study in more detail the absorbed dose distribution in the cerebro-spinal fluid, in the surface of the central nervous system, and in tumor sites. We simulated decreased uptake, as well as highly selective uptake in free-floating tumor cells and in meningeal lesions (1-16 cells thick).

RESULTS

In case of limited access to lesions adherent to the pia mater, the beta-emitter 131I provides crossfire from the CSF, resulting in a higher absorbed dose (Gy/MBq) in these lesions as compared with the Auger emitter 67Ga. In case of increasing radionuclide uptake, the increment of the absorbed dose in the adherent lesions and the free floating cells from 67Ga is considerable because of the local deposition of energy by this radionuclide.

CONCLUSIONS

The model might be useful to select the optimal emission characteristics of radionuclides applicable for intrathecal therapy, which is demonstrated in a comparison of the Auger emitter 67Ga and the beta-emitter 131I.

Radionuclide therapy revisited

Apart from its use in endocrinology and rheumatology, therapeutic nuclear medicine is developing rapidly as an additional treatment modality in oncology. Many different specific tumour-seeking radiopharmaceuticals are being applied both for diagnostic scintigraphy and treatment, using multiple routes and mechanisms to target radionuclides at tumours. After a brief introduction of some basic principles of radionuclide targeting, the therapeutic radiopharmaceuticals available are reviewed according to the accumulation site in relation to the cell nucleus; the results of their current clinical use for therapy are also reviewed. The response observed to a number of these applications, the non-invasiveness of the procedure and the relative lack of toxicity and late effects in comparison with chemotherapy and external beam radiotherapy make radionuclide therapy an attractive and realistic alternative in the management of malignant disease, as well as in the treatment of a few benign disorders.

Dosimetry of intrathecal iodine131 monoclonal antibody in cases of neoplastic meningitis

Radioiodinated monoclonal antibodies (MCA) were administered by the lumbar route into the cerebrospinal fluid (CSF) of four patients with malignant leptomeningeal disease. Evidence suggesting uptake of 131I-MCA by tumour sites was seen in scintigrams. Dosimetry calculations were carried out, assuming that a proportion of the administered radionuclide was bound as a thin layer on the CSF surfaces of the meninges. The percentage injected dose and the clearance curves for the head and four spinal segments were obtained by scintigraphy after administration of tracer amounts of 131I-MCA (7-18 MBq). Although radioisotope levels in the central nervous system (CNS) fell, as determined by both external scintillation counting and direct CSF sampling, a marked difference in the measurements developed with respect to time. The ratio of these two measurements reached a maximum of 49:1, 7 days after monoclonal antibody administration. Patients subsequently received therapeutic amounts (870-1600 MBq) of 131I-MCAs, resulting in clinical remissions and prolonged survival. The mean absorbed radiation dose was estimated as 3.9 cGy.MBq-1 to the thoraco-lumbar region of the spine and 0.51 cGy.MBq-1 to the outer surface of the brain. The maximal dose delivered to the surface of the CNS in the region of the spine and brain was 5800 and 600 cGy, respectively.

A pilot study of 131I monoclonal antibodies in the therapy of leptomeningeal tumors

A pilot study was performed to investigate the toxicity and therapeutic effect of radiolabeled antibody administered intrathecally in patients with leptomeningeal tumors. Five patients who failed conventional therapy received between 11 mCi and 40 mCi of radiolabeled antibody. The choice of antibody varied depending on the immunophenotype of the tumor. Therapy was well tolerated generally, with minimal acute toxicity. Four of five patients achieved an objective response to treatment that has been sustained for a period varying from 7 months to 2 years. No clinical signs of chronic toxicity have been observed in patients 1 and 2 years after therapy.