Kenji Kikuchi and Edward A. Neuwelt
✓ The present investigation was conducted to examine the effects upon normal lymphocyte activation of the addition of brain-tumor cyst fluid or cerebrospinal fluid (CSF) to an in vitro culture system. It was believed that factors present in these fluids may play a role in local and systemic immunosuppression in brain-tumor patients. The authors evaluated the effect of the cyst fluid, CSF, and serum from eight patients with brain tumors (one astrocytoma, five glioblastoma multiforme, one medulloblastoma, and one microglioma) on mitogen-stimulated lymphocyte function as measured by 3H-thymidine incorporation, cell size distribution, and cellular proliferation. Lymphocytes from normal volunteers were incubated for 90 hours in culture medium with 10% pooled human serum, mitogens (phytohemagglutinin, concanavalin A, and pokeweed mitogen), and a range of volumes of cyst fluid or CSF from the tumor patients. Significant suppression of mitogen-induced activation of the lymphocytes was demonstrated in the presence of cyst fluid from five out of six patients, but the mitogen response was only minimally affected by the addition of the CSF from these patients to the culture medium. The suppression of lymphocyte activation by cyst fluid was directly proportional in several cases to the concentration of the cyst fluid. The total protein, albumin, and immunoglobulin (Ig) concentrations in the cyst fluids were observed to roughly correspond to the serum levels and were much higher than in CSF. These studies suggest that brain-tumor cells locally produce lymphocyte-suppressive factors which may then be released into blood. Preliminary characterization of the suppressive factor(s) responsible for the inhibition of lymphocyte function indicates that they are non-dialyzable and do not appear to be an IgG.
Jules M. Nazzaro and Edward A. Neuwelt
✓ In this analysis, the authors review studies over the last 50 years addressing the association between long-term survival and type of surgical management in adults with supratentorial intermediate or high-grade astrocytomas. Earlier reports are included because they are repeatedly referenced in current works and clearly are an important basis upon which present attitudes are predicated. Because recent work has definitively demonstrated the significance of prognostic variables on outcome, the handling of such factors in studies that investigated survival data according to degree of surgery is emphasized. Study design, experimental methods used, and methods of data analysis are also examined. This analysis shows that there is little justification for dogmatic statements concerning the relationship between increasing patient survival times and aggressive surgical management in adults with supratentorial intermediate or high-grade astrocytomas, if patients receive postoperative radiotherapy.
Implications for monoclonal antibody therapy
Edward A. Neuwelt, H. David Specht and Suellen A. Hill
✓ The variable penetration of chemotherapeutic drugs into brain and tumor is more dependent upon lipid solubility than upon size. In contrast, the molecular weight of virus- and tumor-specific monoclonal antibodies appears to limit uptake. The authors have studied eight patients with malignant brain tumors in order to compare tumor uptake of an iodinated contrast agent evaluated by computerized tomography scanning with uptake of the low and high molecular weight imaging agents technetium-99m (99mTc)-glucoheptonate and 99mTc-albumin, respectively, measured by radionuclide brain scanning. The agent 99mTc-labeled albumin was chosen for evaluation because its molecular weight (68,000) is similar to that of the most clinically promising monoclonal antibody fragment, the immunoglobulin (Ig) G Fab monomeric fragment. The radionuclide brain scans in the eight patients showed highly variable permeability of brain tumor to these markers, with uptake of the high molecular weight marker in the tumor being much less than that of the low molecular weight radionuclide. A clinical implication of these studies is that the success of monoclonal antibody therapy in the treatment of malignant brain tumors may require techniques to increase permeability of the blood-brain barrier and blood-tumor barrier to protein.
Edward A. Neuwelt, Michael A. Pagel and Richard D. Dix
✓ The present studies were undertaken to determine if viral particles can be delivered across the rat blood-brain barrier (BBB). Osmotic BBB modification with intracarotid mannitol (25%) was immediately followed by bolus intracarotid administration of 0.5 ml purified, ultraviolet-inactivated, herpes simplex virus type 1 endogenously labeled with 35S-labeled methionine (2.0 × 106 cpm, approximately 5 × 108 plaque-forming units/ml). After 60 minutes, intravascular virus was cleared by saline perfusion and the animals were sacrificed. A marked increase (fourfold, p ≤ 0.02) in radioactivity was observed in the ipsilateral brain hemisphere when compared to control animals without barrier modification. Administration of intravenous virus immediately after BBB modification displayed no difference in delivery when compared to intracarotid saline-infused controls (without BBB modification) suggesting the importance of a first-pass phenomenon. There were no significant differences in serum concentrations among intracarotid or intravenous groups. These preliminary studies suggest the possibility of delivering viral particles across the BBB with osmotic disruption, which may permit delivery of genetic material in replication-defective viral vectors in the feline model of GM2-gangliosidosis.
Edward A. Neuwelt, Alfred Horaczek and Michael A. Pagel
✓ Osmotic modification of the blood-brain barrier (BBB) provides an experimental model of vasogenic edema, is totally reversible, and does not cause any structural damage. In the present communication, the effect of corticosteroids on drug delivery to normal rat brain was evaluated in this model. Intraperitoneal dexamethasone was administered at doses ranging from 12 to 48 mg/sq m for 3 days; gentamicin delivery to the brain was then evaluated after either intravenous or intracarotid administration in both control and BBB-modified animals. Only animals receiving the highest dose of dexamethasone and in which the gentamicin was given intravenously demonstrated a statistically significant decrease in drug delivery. The effect of dexamethasone over a wide range of dosages, therefore, exhibited only modest effects on drug delivery to normal brain after osmotic BBB disruption.
A clinico-pathological study
Edward A. Neuwelt, Mark Glasberg, Eugene Frenkel and W. Kemp Clark
✓ Eight patients with primary malignant pineal tumors have been seen at this institution over the past 6 years; six of them underwent definitive surgical exploration. Complete gross microsurgical excision of well encapsulated tumors was possible in four of these patients. In two cases of pineal germinomas, a biopsy and a subtotal resection were carried out because of the known radiosensitivity of this tumor. These six surgical patients all received postoperative craniospinal radiation and continue to do well up to 6 years postoperatively. Two nonoperative patients were initially treated at other institutions by ventriculoperitoneal shunt and radiation and were the only ones to develop metastatic disease. One patient had metastasis of her pineoblastoma to her unirradiated spinal canal and the other patient had metastasis of his germinoma to the peritoneum. The former patient was quadriplegic on admission, although her pineal tumor was no longer visible on computerized tomography (CT), and she died of pneumonia. The latter patient's tumor secreted the beta chain of human chorionic gonadotropin (HCG). This patient's massive metastatic tumor burden completely regressed as determined by body CT scan and HCG levels after four courses of chemotherapy with bleomycin, vinblastine, and cis-platinum. In 20 patients with lesions of the pineal region, craniotomy was associated with only one death (a patient with metastatic adenocarcinoma). Thus, microsurgery for pineal tumors provides either a reasonably safe potential for complete tumor extirpation and possible cure, or a tissue diagnosis which is necessary for appropriate therapeutic planning for radiotherapy and/or chemotherapy. The traditional therapeutic approach of empiric radiotherapy without a tissue diagnosis for pineal lesions may no longer be warranted.
Jules M. Nazzaro, William T. Shults and Edward A. Neuwelt
✓ To optimize orientation and operative exposure for aggressive resection, the authors approached pineal region tumors transtentorially with the patient in a semisitting position. In the current report, 12 consecutive patients were evaluated to document operative ocular morbidity referable to the brain stem as well as visual deficits secondary to occipital lobe retraction. Before craniotomy, ophthalmological findings related to dorsal midbrain dysfunction were evident in four of the 10 patients who had previously undergone ventricular shunting. The other patients developed a partial or complete Parinaud's syndrome in the early postoperative period and some suffered additional deficits such as cranial nerve palsies. These deficits improved to varying degrees in all patients. Although each had full visual fields preoperatively, an absolute or incomplete left homonymous hemianopsia developed in the immediate postoperative period. Such visual field deficits fully resolved over a variable period of time in 10 of the 12 patients. One patient has a permanent left homonymous hemianopsia, while another has a left homonymous paracentral scotoma. Eight patients were able to return to preoperative pursuits. While ocular abnormalities related to dorsal midbrain dysfunction are most probably independent of operative approach, visual field deficits attributable to occipital lobe retraction were common in patients after a occipital transtentorial approach performed in the semisitting position. Reading difficulties associated with ocular motor dysfunction due to dorsal midbrain involvement represent the principal long-term neuro-ophthalmological complaint of patients who have undergone pineal region surgery.
Kenji Kikuchi, Christopher I. McCormick and Edward A. Neuwelt
✓ This investigation was conducted to examine the immunosuppressive potential of phenytoin in vivo and to document a correlation between phenytoin therapy and depressed lymphocyte responsiveness to mitogens. It was thought that phenytoin, the most widely used anticonvulsant agent, may play some role in the immunosuppression seen in brain-tumor patients. The effect of phenytoin on mitogen-stimulated lymphocyte function was evaluated by tritiated (3H)-thymidine incorporation and lymphocyte nuclear size distribution. Lymphocytes from either phenytoin-treated or normal rabbits were incubated for 90 hours in culture medium in the presence of three mitogens: phytohemagglutinin (PHA), concanavalin A (Con A), and pokeweed mitogen (PWM). Significant suppression of mitogen-induced activation of the lymphocytes from treated animals was demonstrated. The present studies suggest a possible connection between phenytoin therapy and altered immune competence in brain-tumor patients.