Faculty Bibliography

Our experience with 11C-putrescine underscores the difficulty of finding a selective brain tumor tracer, uniquely incorporated by neoplastic glia or metastatic cells within brain, but not by the proliferating, nontransformed cells which constitute a normal pathophysiological reaction to various disease processes. Thirty-three patients with 36 lesions were studied with 11C-putrescine to determine the specificity of labeled putrescine for tumor tissue. The uptake of 11C-putrescine was correlated with local cerebral glucose metabolic rate in various lesions, including different types of tumors, to assess the relationship between 11C-putrescine uptake and tumor biology. Carbon-11-putrescine uptake was similar in malignant tumor and benign, non-neoplastic lesions with blood-brain barrier breakdown, illustrating the lack of tumor specificity of this tracer. Carbon-11-putrescine was not well incorporated into poorly enhancing lesions, regardless of their pathology, emphasizing the requirement of a disrupted blood-brain barrier for 11C-putrescine uptake. The ratio of 11C concentration within lesions, compared to that in a region of interest in the contralateral brain, weakly correlated with an analogous ratio for local cerebral glucose metabolic rate in various lesions. Physiological processes not unique to tumors are associated with polyamine active transport and metabolism and contribute to the lack of tumor specificity of 11C-putrescine. Carbon-11-putrescine appear to have less diagnostic utility than 18FDG in brain tumors. The potential of 11C-putrescine for evaluating the effect of antineoplastic therapy and providing prognostic information on brain tumors remains to be investigated

Four patients in whom the plasma CEA reflected the clinical course of intracranial disease are presented. We conclude that a search to explain an elevated CEA should include the central nervous system. In addition, in selected patients with brain metastases the plasma CEA is a helpful indicator of tumor control and of its response to radiation and chemotherapy

We used quantitative autoradiography (QAR) to evaluate the effect of systemically administered dexamethasone on capillary permeability in brain tumors and surrounding brain. Rats bearing unilateral right hemispheric C6 gliomas were studied at one and twelve hours after 10 mg/kg of intraperitoneal dexamethasone. Capillary permeability was determined by measuring unidirectional blood-to-brain and blood-to-tumor transport of 14C-alpha aminoisobutyric acid (14C-AIB) over fifteen minutes. 14C-AIB entry into tumor, brain adjacent-to-tumor (BAT), and ipsilateral and contralateral cortices was determined and expressed as a unidirectional transfer constant, K. Nontreated tumor K was more than two-fold greater than K for BAT and ten-fold greater than ipsilateral cortical K, confirming substantial barrier disruption in tumor. In addition, the K for BAT was also significantly greater than K for cortex, indicating that the barrier in the peritumoral region was also disrupted. One hour after dexamethasone treatment, tumor K fell to 63% of its pretreatment value (p less than 0.025). By twelve hours post-treatment, tumor K fell to 25% of the untreated value (p less than 0.001) and to 47% of the one-hour value (p less than 0.005). BAT K fell to 29% of its untreated value (p less than 0.02) and to 46% of its one-hour value (p less than 0.02). By 12 hours, ipsilateral cortical K fell to 67% of the untreated cortical value (p less than 0.05). Compared to untreated values, there was no significant difference between contralateral cortical K at either one or twelve hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Using quantitative autoradiography, we investigated the effect of meningeal carcinomatosis on local cerebral glucose utilization (LCGU). A rat model of meningeal carcinomatosis using Walker 256 tumor was used. LCGU was evaluated using 14C-2-deoxy-D-glucose according to the Sokoloff method. Thirty-one neuroanatomic structures were evaluated, both separately and as part of five functional or neuroanatomic groups: olfactory, auditory, visual, limbic, and white matter. The relationship between tumor and LCGU of underlying brain was examined. Compared with controls, there was no global change of LCGU in the experimental group that applied to all structures. However, mean LCGU was significantly depressed in olfactory cortex, temporal cortex, olfactory tubercle, amygdala, caudate/putaman, inferior colliculus, medial geniculate, anterior commissure, and corpus callosum, and the functional groups that make up the olfactory and auditory systems. There was no correlation between extent of regional tumor burden and degree of depression of LCGU in underlying structures. In meningeal carcinomatosis, tumor results in selective regional depression of LCGU. This occurs both in structures underlying tumor and those anatomically remote, but in certain cases, functionally related to structures subadjacent to tumor. These data may help to explain the diversity of neurologic dysfunction seen in patients with meningeal cancer

We reviewed the serial CT studies obtained between 1974 and 1986 of 31 patients with malignant glioma who survived for 2 to 11 years after surgical removal of their tumors. In all cases surgery was followed by radiation therapy to the head (6000 rad) and chemotherapy. Patients were divided into two age groups: those under age 40 (n = 13) and those over age 40 (n = 18). By 2 years all patients in the older group developed evidence of leukoencephalopathy characterized by periventricular zones of decreased attenuation. Only 58% of the younger group showed evidence of white matter changes at this point. All patients from both age groups who survived for 4 years developed leukoencephalopathy. The severity of leukoencephalopathy from 6 months after surgery and beyond was always greater in the older group. All patients developed cerebral atrophy as evidenced by sulcal dilatation and ventricular enlargement. Atrophy was progressive beginning with the first postirradiation scan, and was always more severe in the older patients. A significant difference was found in the clinical status of the two age groups as determined by the mental status score and the Karnofsky scale. Despite progressive brain changes, survivors under age 40 maintained a nearly normal mental status and Karnofsky scores until their death, whereas survivors over age 40 showed progressive clinical decline

Using quantitative autoradiography, we investigated the entry over 90 min of [14C]methotrexate (MTX) into C6 gliomas implanted bilaterally into Wistar rat brains. The [14C]MTX was administered into the right carotid artery, yielding ipsilateral 'arterial' brain and tumor concentrations and contralateral 'systemic' concentrations. In a separate group of tumor-bearing rats, mannitol 1.6 M was given into the right carotid artery prior to administering the [14C]MTX to disrupt the blood-brain barrier on the ipsilateral side. [14C]MTX tissue concentrations were measured in regions of 50 x 50 x 20 microns in tumor, peritumoral brain tissue (brain adjacent to tumor), and cerebral cortex. In the nonmannitol experiments, tissue concentrations from the rats at each time interval were fitted using a nonlinear curve fitting program, and the pharmacokinetic values of influx and efflux of [14C]MTX into the three compartments were calculated. The influx rate constant K1 for [14C]MTX ranged from 1.3 to 8.2 microliters/g/min in the tumor. Influx rate constants in the cortex were 1.3-1.9 microliters/g/min and in the brain adjacent to tumor were 1.7-2.8 microliters/g/min. The efflux rate constant k2 was approximated for each tissue but was less reliable than the K1 values. The k2 for tumor, brain adjacent to tumor, and cortex was always higher than the corresponding K1. Peak [14C]MTX concentrations in the tumor were highest after arterial infusion with hyperosmolar barrier disruption, lower after arterial administration without barrier modification, and lowest after systemic administration. However, cortical [14C]MTX concentration was also highest after arterial administration with barrier modification and higher than the highest tumor concentration. Furthermore, tissue exposure (concentration x time) was also highest in the cortex after barrier disruption. The [14C]MTX concentration x time (micrograms/min/g x 90 min +/- SEM) ratio between tumor and cortex after systemic administration was 33.4 +/- 4.1:15.7 +/- 1.9; after arterial administration it was 96.3 +/- 11.7:30.3 +/- 3.1; after arterial administration with barrier disruption it was 266.6 +/- 28.8:311.2 +/- 15.9. The greatest tumor:cortex ratio (3.1:1) occurred with arterial drug administration without barrier disruption. Disrupting the barrier enough to permit increased tumor exposure actually increased cortical exposure to a greater degree. The resulting poorer therapeutic ratio would not appear to support this technique in humans, at least for neurotoxic drugs