Pharmacology and phase I/II study of continuous intravenous infusions of iododeoxyuridine and hyperfractionated radiotherapy in patients with glioblastoma multiforme

Phase I and Pharmacology Study of Ropidoxuridine (IPdR) as Prodrug for Iododeoxyuridine-Mediated Tumor Radiosensitization in Advanced GI Cancer Undergoing Radiation

PURPOSE

Iododeoxyuridine (IUdR) is a potent radiosensitizer; however, its clinical utility is limited by dose-limiting systemic toxicities and the need for prolonged continuous infusion. 5-Iodo-2-pyrimidinone-2'-deoxyribose (IPdR) is an oral prodrug of IUdR that, compared with IUdR, is easier to administer and less toxic, with a more favorable therapeutic index in preclinical studies. Here, we report the clinical and pharmacologic results of a first-in-human phase I dose escalation study of IPdR + concurrent radiation therapy (RT) in patients with advanced metastatic gastrointestinal (GI) cancers.

PATIENTS AND METHODS

Adult patients with metastatic GI cancers referred for palliative RT to the chest, abdomen, or pelvis were eligible for study. Patients received IPdR orally once every day × 28 days beginning 7 days before the initiation of RT (37.5 Gy in 2.5 Gy × 15 fractions). A 2-part dose escalation scheme was used, pharmacokinetic studies were performed at multiple time points, and all patients were assessed for toxicity and response to Day 56.

RESULTS

Nineteen patients were entered on study. Dose-limiting toxicity was encountered at 1,800 mg every day, and the recommended phase II dose is 1,200 mg every day. Pharmacokinetic analyses demonstrated achievable and sustainable levels of plasma IUdR ≥1 μmol/L (levels previously shown to mediate radiosensitization). Two complete, 3 partial, and 9 stable responses were achieved in target lesions.

CONCLUSIONS

Administration of IPdR orally every day × 28 days with RT is feasible and tolerable at doses that produce plasma IUdR levels ≥1 μmol/L. These results support the investigation of IPdR + RT in phase II studies.

Clinical Results of Unconventional Fractionation Radiotherapy in Central Nervous System Tumors

Malignant brain tumors (primary and metastatic) are apparently resistant to most therapeutic efforts. Several randomized trials have provided evidence supporting the efficacy of radiation therapy. Attempts at improving the results of external beam radiotherapy include altered fractionation, radiation sensitizers and concomitant chemotherapy. In low-grade gliomas, all clinical studies with radiotherapy have employed conventional dose fractionation regimens. In high-grade gliomas, hypofractionation schedules represent effective palliative regimens in poor prognosis subsets of patients; short-term survival in these patients has not allowed to evaluate late toxicity. In tumors arising within the central nervous system, hyperfractionated irradiation exploits the differences in repair capacity between tumour and late responding normal tissues. It may allow for higher total dose and may result in increased tumor cell kill. Accelerated radiotherapy may reduce the repopulation of tumor cells between fractions. It may potentially improve tumor control for a given dose level, provided that there is no increase in late normal tissue injury. In supratentorial malignant gliomas, superiority of accelerated hyperfractionated over conventionally fractionated schedules was observed in a randomized trial; however, the gain in survival was less than 6 months. At present no other randomized trial supports the preferential choice for altered fractionation irradiation. Also in pediatric brainstem tumors there are no data to confirm the routine use of hyperfractionated irradiation, and significant late sequelae have been reported in the few long-term survivors. Shorter treatment courses with accelerated hyperfractionated radiotherapy may represent a useful alternative to conventional irradiation for the palliation of brain metastases. Different considerations have been proposed to explain this gap between theory and clinical data. Patients included in dose/effect studies are not stratified by prognostic factors and other treatment-related parameters. This observation precludes any definite conclusion about the relative role of conventional and of altered fractionation. New approaches are currently in progress. More prolonged radiation treatments, up to higher total doses, could delay time to tumor progression and improve survival in good prognosis subsets of patients; altered fractionation may be an effective therapeutic tool to achieve this goal.

Evaluation of the combined effect of NIR laser and ionizing radiation on cellular damages induced by IUdR-loaded PLGA-coated Nano-graphene oxide

Glioma is one of the most common malignant cancers of the central nervous system (CNS). Radiatherapy and chemotherapy may be used to slow the growth of tumors that cannot be removed with surgery. The current study developed a combination therapy tool using Nanographene oxide (NGO) functionalized with poly lactic-co-glycolic acid (PLGA) as a carrier of 5-iodo-2-deoxyuridine (IUdR) for glioma cancer treatment. U87MG cells were treated in different groups with IUdR, PLGA-coated Nanographene oxide (PLGA-NGO), IUdR-loaded PLGA-coated Nanographene oxide (IUdR-PLGA-NGO), 2Gy 6MV X-ray radiation, and near-infrared region (NIR) laser radiation. PLGA-NGO showed excellent biocompatibility, high storage capacity for IUdR and high photothermal conversion efficiency. It was effectively employed to create cell damage in the U87MG cell line in the presence of X-ray (6 MV) and NIR laser. Moreover, IUdR-PLGA-NGO+X-ray+NIR laser significantly reduced the plating efficiency of the cells in comparison with IUdR-PLGA-NGO+X-ray and IUdR-PLGA-NGO+NIR laser. Furthermore, Prussian blue staining showed that IUdR-PLGA-NGO-SPIONs were delivered into glioblastoma cells. The PLGA-NGO loaded with IUdR under NIR and X-ray radiation exhibited the highest cytotoxicity toward U87MG cells when compared with other treatment methods, indicating efficient radio-photothermal targeted therapy.

Somatic mutations in glioblastoma are associated with methylguanine-DNA methyltransferase methylation

The high level of methylguanine-DNA methyltransferase (MGMT) in glioblastoma is responsible for resistance to alkylating agents, such as temozolomide (TMZ). In glioblastomas with a methylated MGMT promoter, MGMT deficiency is presumed, resulting in an enhanced effect of TMZ. The aim of the present study was to investigate whether genomic alterations work synergistically with MGMT methylation status and contribute to the response to treatment and overall prognosis in glioblastoma. The current study included a cohort of 35 glioblastoma patients, with MGMT promoter methylation present in 48% of tumors. MGMT methylation was associated with significantly longer median survival (29.0 months) compared with patients without MGMT methylated tumors (12.0 months), as well as longer median time to progression following TMZ treatment (13.2 months, compared with 5.6 months for patients with an unmethylated MGMT status). In addition, somatic variants in hot spot exonic regions of 50 key cancer genes were examined in these glioblastomas. Non-synonymous mutations in methylated MGMT glioblastomas were four times higher compared with unmethylated MGMT glioblastomas. Furthermore, significantly increased frequencies of mutations in the TP53, CDKN2A, PTEN and PIK3CA genes were detected in MGMT methylated glioblastomas. The relative significance of these mutations, and their contribution to TMZ sensitivity, adjunct to MGMT methylation, require further investigation in a larger cohort.

The Metabolic Epicenter of Supratentorial Gliomas: A 1H-MRSI Study

Background:

Assessing the impact of glioma location on prognosis remains elusive. We approached the problem using multivoxel proton magnetic resonance spectroscopic imaging (1H-MRSI) to define a tumor “metabolic epicenter”, and examined the relationship of metabolic epicenter location to survival and histopathological grade.

Methods:

We studied 54 consecutive patients with a supratentorial glioma (astrocytoma or oligodendroglioma, WHO grades II-IV). The metabolic epicenter in each tumor was defined as the 1H-MRSI voxel containing maximum intra-tumoral choline on preoperative imaging. Tumor location was considered the X-Y-Z coordinate position, in a standardized stereotactic space, of the metabolic epicenter. Correlation between epicenter location and survival or grade was assessed.

Results:

Metabolic epicenter location correlated significantly with patient survival for all tumors (r2 = 0.30, p = 0.0002) and astrocytomas alone (r2 = 0.32, p = 0.005). A predictive model based on both metabolic epicenter location and histopathological grade accounted for 70% of the variability in survival, substantially improving on histology alone to predict survival. Location also correlated significantly with grade (r2 = 0.25, p = 0.001): higher grade tumors had a metabolic epicenter closer to the midpoint of the brain.

Conclusions:

The concept of the metabolic epicenter eliminates several problems related to existing methods of classifying glioma location. The location of the metabolic epicenter is strongly correlated with overall survival and histopathological grade, suggesting that it reflects biological factors underlying glioma growth and malignant dedifferentiation. These findings may be clinically relevant to predicting patterns of local glioma recurrence, and in planning resective surgery or radiotherapy.

Predictors of long-term survival in patients with glioblastoma multiforme: advancements from the last quarter century

Over the last quarter century there has been significant progress toward identifying certain characteristics and patterns in GBM patients to predict survival times and outcomes. We sought to identify clinical predictors of survival in GBM patients from the past 24 years. We examined patient survival related to tumor locations, surgical treatment, postoperative course, radiotherapy, chemotherapy, patient age, GBM recurrence, imaging characteristics, serum, and molecular markers. We present predictors that may increase, decrease, or play no significant role in determining a GBM patient's long-term survival or affect the quality of life.

First-in-human phase 0 trial of oral 5-iodo-2-pyrimidinone-2'-deoxyribose in patients with advanced malignancies

PURPOSE

Iododeoxyuridine (IdUrd), a halogenated nucleoside analog, produced clinical responses when administered as a radiosensitizer via continuous intravenous (c.i.v.) infusion over the course of radiotherapy. We conducted a phase 0 trial of 5-iodo-2-pyrimidinone-2'-deoxyribose (IPdR), an oral prodrug of IdUrd, in patients with advanced malignancies to assess whether the oral route was a feasible alternative to c.i.v. infusion before embarking on large-scale clinical trials. Plasma concentrations of IPdR, IdUrd, and other metabolites were measured after a single oral dose of IPdR.

EXPERIMENTAL DESIGN

Eligible patients had advanced refractory malignancies. A single oral dose of IPdR was administered per patient and patients were followed for 14 days for safety assessments; dose escalations were planned (150, 300, 600, 1,200, and 2,400 mg) with one patient per dose level and 6 patients at the highest dose level. Blood sampling was conducted over a 24-hour period for pharmacokinetic analysis.

RESULTS

There were no drug-related adverse events. Plasma concentrations of IdUrd generally increased as the dose of IPdR escalated from 150 to 2,400 mg. All patients at the 2,400 mg dose achieved peak IdUrd levels of (mean ± SD) 4.0 μmol/L ± 1.02 μmol/L at 1.67 ± 1.21 hours after IPdR administration.

CONCLUSIONS

Adequate plasma levels of IdUrd were obtained to justify proceeding with a phase I trial of IPdR in combination with radiation. This trial shows the ability of a small, phase 0 study to provide critical information for decision-making regarding future development of a drug.

5-iodo-2-pyrimidinone-2'-deoxyribose-mediated cytotoxicity and radiosensitization in U87 human glioblastoma xenografts

PURPOSE

5-iodo-2-pyrimidinone-2'-deoxyribose (IPdR) is a novel orally administered (p.o.) prodrug of 5-iododeoxyuridine. Because p.o. IPdR is being considered for clinical testing as a radiosensitizer in patients with high-grade gliomas, we performed this in vivo study of IPdR-mediated cytotoxicity and radiosensitization in a human glioblastoma xenograft model, U87.

METHODS AND MATERIALS

Groups of 8 or 9 athymic male nude mice (6-8 weeks old) were implanted with s.c. U87 xenograft tumors (4 x 10(6) cells) and then randomized to 10 treatment groups receiving increasing doses of p.o. IPdR (0, 100, 250, 500, and 1000 mg/kg/d) administered once daily (q.d.) x 14 days with or without radiotherapy (RT) (0 or 2 Gy/d x 4 days) on days 11-14 of IPdR treatment. Systemic toxicity was determined by body weight measurements during and after IPdR treatment. Tumor response was assessed by changes in tumor volumes.

RESULTS

IPdR alone at doses of > or =500 mg/kg/d resulted in moderate inhibition of tumor growth. The combination of IPdR plus RT resulted in a significant IPdR dose-dependent tumor growth delay, with the maximum radiosensitization using > or =500 mg/kg/d. IPdR doses of 500 and 1000 mg/kg/d resulted in transient 5-15% body weight loss during treatment.

CONCLUSIONS

In U87 human glioblastoma s.c. xenografts, p.o. IPdR given q.d. x 14 days and RT given 2 Gy/d x 4 days (days 11-14 of IPdR treatment) results in a significant tumor growth delay in an IPdR dose-dependent pattern. The use of p.o. IPdR plus RT holds promise for Phase I/II testing in patients with high-grade gliomas.

Toxicology and pharmacokinetic study of orally administered 5-iodo-2-pyrimidinone-2'deoxyribose (IPdR) x 28 days in Fischer-344 rats: impact on the initial clinical phase I trial design of IPdR-mediated radiosensitization

PURPOSE

A toxicology and pharmacokinetic study of orally administered (po) IPdR (5-3iodo-2-pyrimidinone-2'deoxyribose, NSC-726188) was performed in Fischer-344 rats using a once daily (qd) x 28 days dosing schedule as proposed for an initial phase I clinical trial of IPdR as a radiosensitizer.

METHODS

For the toxicology assessment, 80 male and female rats (10/sex/dosage group) were randomly assigned to groups receiving either 0, 0.2, 1.0 or 2.0 g kg(-1)day(-1) of po IPdR x 28 days and one-half were observed to day 57 (recovery group). Animals were monitored for clinical signs during and following treatment with full necropsy of one-half of each dosage group at day 29 and 57. For the plasma pharmacokinetic assessment, 40 rats (10/sex/dosage group) were randomly assigned to groups receiving either 0.2 or 1.0 g kg(-1)day(-1) of po IPdR x 28 days with multiple blood samplings on days 1 and 28 and single blood sampling on days 8 and 15.

RESULTS

No drug-related deaths occurred. Higher IPdR doses resulted in transient weight loss and transient decreased hemoglobins but had no effect on white cells or platelets. Complete serum chemistry evaluation showed transient mild decreases in total protein, alkaline phosphatase, and serum globulin. Necropsy evaluation at day 29 showed minimal to mild histopathologic changes in bone marrow, lymph nodes and liver; all reversed by day 59. There were no sex-dependent differences in plasma pharmacokinetics of IPdR noted and the absorption and elimination kinetics of IPdR were found to be linear over the dose range studied.

CONCLUSIONS

A once-daily dosing schedule of po IPdR for 28 days with doses up to 2.0 g kg(-1)day(-1) appeared to be well tolerated in Fischer-344 rats. Drug-related weight loss and microscopic changes in bone marrow, lymph nodes and liver were observed. These changes were all reversed by day 57. IPdR disposition was linear over the dose range used. However, based on day 28 kinetics it appears that IPdR elimination is enhanced following repeated administration. These toxicology and pharmacokinetic data were used when considering the design of our initial phase I trial of po IPdR as a clinical radiosensitizer.

Schedule-dependent drug effects of oral 5-iodo-2-pyrimidinone-2'-deoxyribose as an in vivo radiosensitizer in U251 human glioblastoma xenografts

PURPOSE

5-Iodo-2-pyrimidinone-2'-deoxyribose (IPdR) is an oral prodrug of 5-iodo-2'-deoxyuridine (IUdR), an in vitro/in vivo radiosensitizer. IPdR can be rapidly converted to IUdR by a hepatic aldehyde oxidase. Previously, we found that the enzymatic conversion of IPdR to IUdR could be transiently reduced using a once daily (q.d.) treatment schedule and this may affect IPdR-mediated tumor radiosensitization. The purpose of this study is to measure the effect of different drug dosing schedules on tumor radiosensitization and therapeutic index in human glioblastoma xenografts.

EXPERIMENTAL DESIGN

Three different IPdR treatment schedules (thrice a day, t.i.d.; every other day, q.o.d.; every 3rd day, q.3.d.), compared with a q.d. schedule, were analyzed using athymic nude mice with human glioblastoma (U251) s.c. xenografts. Plasma pharmacokinetics, IUdR-DNA incorporation in tumor and normal proliferating tissues, tumor growth delay following irradiation, and body weight loss were used as end points.

RESULTS

The t.i.d. schedule with the same total daily doses as the q.d. schedule (250, 500, or 1,000 mg/kg/d) improved the efficiency of IPdR conversion to IUdR. As a result, the percentage of IUdR-DNA incorporation was higher using the t.i.d. schedule in the tumor xenografts as well as in normal small intestine and bone marrow. Using a fixed dose (500 mg/kg) per administration, the q.o.d. and q.3.d. schedules also showed greater IPdR conversion than the q.d. schedule, related to a greater recovery of hepatic aldehyde oxidase activity prior to the next drug dosing. In the tumor regrowth assay, all IPdR treatment schedules showed significant increases of regrowth delays compared with the control without IPdR (q.o.d., 29.4 days; q.d., 29.7 days; t.i.d., 34.7 days; radiotherapy alone, 15.7 days). The t.i.d. schedule also showed a significantly enhanced tumor growth delay compared with the q.d. schedule. Additionally, the q.o.d. schedule resulted in a significant reduction in systemic toxicity.

CONCLUSIONS

The t.i.d. and q.o.d. dosing schedules improved the efficiency of enzymatic activation of IPdR to IUdR during treatment and changed the extent of tumor radiosensitization and/or systemic toxicity compared with a q.d. dosing schedule. These dosing schedules will be considered for future clinical trials of IPdR-mediated human tumor radiosensitization.

Differential Radiosensitization in DNA Mismatch Repair-Proficient and -Deficient Human Colon Cancer Xenografts with 5-Iodo-2-pyrimidinone-2′-deoxyribose

PURPOSE

5-iodo-2-pyrimidinone-2'-deoxyribose (IPdR) is a pyrimidinone nucleoside prodrug of 5-iododeoxyuridine (IUdR) under investigation as an orally administered radiosensitizer. We previously reported that the mismatch repair (MMR) proteins (both hMSH2 and hMLH1) impact on the extent (percentage) of IUdR-DNA incorporation and subsequent in vitro IUdR-mediated radiosensitization in human tumor cell lines. In this study, we used oral IPdR to assess in vivo radiosensitization in MMR-proficient (MMR+) and -deficient (MMR-) human colon cancer xenografts.

EXPERIMENTAL DESIGN

We tested whether oral IPdR treatment (1 g/kg/d for 14 days) can result in differential IUdR incorporation in tumor cell DNA and subsequent radiosensitization after a short course (every day for 4 days) of fractionated radiation therapy, by using athymic nude mice with an isogenic pair of human colon cancer xenografts, HCT116 (MMR-, hMLH1-) and HCT116/3-6 (MMR+, hMLH1+). A tumor regrowth assay was used to assess radiosensitization. Systemic toxicity was assessed by daily body weights and by percentage of IUdR-DNA incorporation in normal bone marrow and intestine.

RESULTS

After a 14-day once-daily IPdR treatment by gastric gavage, significantly higher IUdR-DNA incorporation was found in HCT116 (MMR-) tumor xenografts compared with HCT116/3-6 (MMR+) tumor xenografts. Using a tumor regrowth assay after the 14-day drug treatment and a 4-day radiation therapy course (days 11-14 of IPdR), we found substantial radiosensitization in both HCT116 and HCT116/3-6 tumor xenografts. However, the sensitizer enhancement ratio (SER) was substantially higher in HCT116 (MMR-) tumor xenografts (1.48 at 2 Gy per fraction, 1.41 at 4 Gy per fraction), compared with HCT116/3-6 (MMR+) tumor xenografts (1.21 at 2 Gy per fraction, 1.20 at 4 Gy per fraction). No substantial systemic toxicity was found in the treatment groups.

CONCLUSIONS

These results suggest that IPdR-mediated radiosensitization can be an effective in vivo approach to treat "drug-resistant" MMR-deficient tumors as well as MMR-proficient tumors.

Continuous 28-day iododeoxyuridine infusion and hyperfractionated accelerated radiotherapy for malignant glioma: a phase I clinical study

PURPOSE

To investigate the maximal tolerated dose of a continuous 28-day iododeoxyuridine (IUdr) infusion combined with hyperfractionated accelerated radiotherapy (HART); to analyze the percentage of IUdr-thymidine replacement in peripheral granulocytes as a surrogate marker for IUdr incorporation into tumor cells; to measure the steady-state serum IUdr levels; and to assess the feasibility of continuous IUdr infusion and HART in the management of malignant glioma.

METHODS AND MATERIALS

Patients were required to have biopsy-proven malignant glioma. Patients received 100 (n = 4), 200 (n = 3), 300 (n = 3), 400 (n = 6), 500 (n = 4), 625 (n = 5), or 781 (n = 6) mg/m(2)/d of IUdr by continuous infusion for 28 days. HART was started 7 days after IUdr initiation. The total dose was 70 Gy (1.2 Gy b.i.d. for 25 days with a 10-Gy boost [2.0 Gy for 5 Saturdays]). Weekly assays were performed to determine the percentage of IUdr-DNA replacement in granulocytes and serum IUdr levels using standard high performance liquid chromatography methods. Standard Phase I toxicity methods were used.

RESULTS

Between June 1994 and August 1999, 31 patients were enrolled. No patient had Grade 3 or worse HART toxicity. Grade 3 or greater IUdr toxicity predominantly included neutropenia (n = 3), thrombocytopenia (n = 3), and elevated liver function studies (n = 3). The maximal tolerated dose was 625 mg/m(2)/d. Thymidine replacement in the peripheral granulocytes peaked at 3 weeks and increased with the dose (maximal thymidine replacement 4.9%). The steady-state plasma IUdr level increased with the dose (maximum, 1.5 microM).

CONCLUSION

In our study, continuous long-term IUdr i.v. infusion had a maximal tolerated dose of 625 mg/m(2)/d. Granulocyte incorporation data verified the concept that prolonged IUdr infusion results in IUdr-DNA replacement that corresponds to a high degree of cell labeling. IUdr steady-state plasma levels increased with increasing dose and attained levels needed for clinical radiosensitization. Continuous IUdr infusion and HART were both feasible and well tolerated.

Five-chlorodeoxycytidine, a tumor-selective enzyme-driven radiosensitizer, effectively controls five advanced human tumors in nude mice

PURPOSE

The study's goals were as follows: (1) to extend our past findings with rodent tumors to human tumors in nude mice, (2) to determine if the drug protocol could be simplified so that only CldC and one modulator, tetrahydrouridine (H4U), would be sufficient to obtain efficacy, (3) to determine the levels of deoxycytidine kinase and dCMP deaminase in human tumors, compared to adjacent normal tissue, and (4) to determine the effect of CldC on normal tissue radiation damage to the cervical spinal cord of nude mice.

METHODS AND MATERIALS

The five human tumors used were as follows: prostate tumors, PC-3 and H-1579; glioblastoma, SF-295; breast tumor, GI-101; and lung tumor, H-165. The duration of treatment was 3-5 weeks, with drugs administered on Days 1-4 and radiation on Days 3-5 of each week. The biomodulators of CldC were N-(Phosphonacetyl)-L-aspartate (PALA), an inhibitor of aspartyl transcarbamoylase, 5-fluorodeoxycytidine (FdC), resulting in tumor-directed inhibition of thymidylate synthetase, and H4U, an inhibitor of cytidine deaminase. The total dose of focused irradiation of the tumors was usually 45 Gy in 12 fractions.

RESULTS

Marked radiosensitization was obtained with CldC and the three modulators. The average days in tumor regrowth delay for X-ray compared to drugs plus X-ray, respectively, were: PC-3 prostate, 42-97; H-1579 prostate, 29-115; glioblastoma, 5-51; breast, 50-80; lung, 32-123. Comparative studies with PC-3 and H-1579 using CldC coadministered with H4U, showed that both PALA and FdC are dispensable, and the protocol can be simplified with equal and possibly heightened efficacy. For example, PC-3 with X-ray and (1) no drugs, (2) CldC plus the three modulators, (3) a high dose of CldC, and (4) escalating doses of CldC resulted in 0/10, 3/9, 5/10, and 6/9 cures, respectively. The tumor regrowth delay data followed a similar pattern. After treating mice only 11/2 weeks with CldC + H4U, 92% of the PC-3 tumor cells were found to possess CldU in their DNA. The great majority of head-and-neck tumors from patient material had markedly higher levels of dC kinase and dCMP deaminase than found in adjacent normal tissue. Physiologic and histologic studies showed that CldC + H4U combined with X-ray, focused on the cervical spinal cord, did not result in damage to that tissue.

CONCLUSIONS

5-CldC coadministered with only H4U is an effective radiosensitizer of human tumors. Ninety-two percent of PC-3 tumor cells have been shown to take up ClUra derived from CldC in their DNA after only 11/2 weeks and 2 weeks of bolus i.p. injections. Enzymatic alterations that make tumors successful have been exploited for a therapeutic advantage. The great electronegativity, coupled with the relatively small Van der Waal radius of the Cl atom, may result in CldC's possessing the dual advantageous properties of FdC on one hand and BrdU and IdU on the other hand. These advantages include autoenhancing the incorporation of CldUTP into DNA by not only overrunning but also inhibiting the formation of competing TTP pools in tumors. A clinical trial is about to begin, with head-and-neck tumors as a first target of CldC radiosensitization.

IUdR polymers for combined continuous low-dose rate and high-dose rate sensitization of experimental human malignant gliomas

Local polymeric delivery enhances IUdR radiosensitization of human malignant gliomas (MG). The combined low-dose rate (LDR) (0.03 Gy/h) and fractionated high-dose rate (HDR) treatments result in cures of experimental MGs. To enhance efficacy, we combined polymeric IUdR delivery, LDR, and HDR for treatments of both subcutaneous and intracranial MGs. In vitro: Cells (U251 MG) were trypsinized and replated in triplicate 1 day prior to LDR irradiation in media either without (control) or with 10 microM IUdR. After 72 hr, LDR irradiation cells were acutely irradiated (1.1 Gy/min) with increasing (0, 1.25, 2.5, 5.0, or 10 Gy) single doses. Implantable IUdR polymers [(poly(bis(p-carboxyphenoxy)-propane) (PCPP): sebaic acid (PCPP:SA), 20:80] (50% loading; 10 mg) were synthesized. In vivo: For flank vs. intracranial tumors, mice had 6 x 10(6) subcutaneous vs. 2 x 10(5) intracranial cells. For intracranial or subcutaneous MGs, mice had intratumoral blank (empty) vs. IUdR polymer treatments. One day after implantation, mice had immediate external LDR (3 cGy/h x 3 days total body irradiation) or HDR (2 Gy BID x 4 days to tumor site) or concurrent treatments. For the in vitro IUdR treatments, LDR resulted in a striking increase in cell-killing when combined with HDR. For the in vivo LDR treatments of flank tumors, the growth delay was greater for the IUdR vs. blank polymer treatments. For the combined LDR and HDR, the IUdR treatments resulted in a dramatic decrease in tumor volumes. On day 60 the log V/V0 were -1.7 +/- 0.22 for combined LDR + HDR + IUdR polymer (P < 0.05 vs. combined LDR + HDR + blank polymer). Survival for the intracranial controls was 22.9 +/- 1.2 days. For the blank polymer + LDR vs. blank polymer + LDR + HDR treatments, survival was 25.3 +/- 1.7 (P = NS) vs. 48.1 +/- 3.5 days (P < 0.05). For IUdR polymer + LDR treatment survival was 27.3 +/- 2.3 days (P = NS). The most striking improvement in survival followed the IUdR polymer + LDR + HDR treatment: 66.0 + 6.4 days (P < 0.05 vs. blank polymer + LDR + HDR). The polymeric IUdR delivery plus combined continuous LDR and HDR treatments results in growth delay and improved survival in animals bearing the MG xenografts. This treatment may hold promise for the treatment of human MGs.

Unlabelled iododeoxyuridine increases the cytotoxicity and incorporation of [1251]-iododeoxyuridine in two human glioblastoma cell lines

Iododeoxyuridine (IUdR), labelled with radioiodines emitting Auger, alpha or beta- radiation, has been proposed as a therapeutic tool in the treatment of cancer. However, the low per cent incorporation in tumour cells and limited cytotoxicity are major obstacles for such an application. Using unlabelled IUdR as a modulator, we have studied the in vitro cytotoxicity of [125I]-IUdR in two human glioblastoma cell lines. Surprisingly, an enhanced cytotoxicity of [125I]-IUdR was observed in the presence of 0.3-10 microM concentrations of unlabelled IUdR in U251 glioblastoma cells and to a lesser extent in LN229 cells. The presence of unlabelled IUdR unexpectedly increased the incorporation of [125I]-IUdR in both cell lines. Thymidine competitively blocked the cytotoxic effects of combined unlabelled and [125I]-labelled IUdR in these cells and DNA-incorporation of radiolabelled IUdR.

Synthetic, implantable polymers for IUdR radiosensitization of experimental human malignant glioma

BACKGROUND

Recently, polymeric controlled delivery of chemotherapy has been shown to improve survival of patients with malignant glioma. We tested the delivery of IUdR via polymers for radiosensitization of experimental intracranial human malignant glioma. To assess efficacy, we measured the in vitro release, the in vivo delivery of IUdR and the resultant radiosensitization of experimental human U251 glioblastoma xenografts.

METHODS

In vitro: To measure release, increasing (10%, 30%, 50%) proportions of IUdR in synthetic [(poly(bis(p-carboxyphenoxy)-propane) (PCPP):sebacic acid (SA) polymer discs were serially incubated in buffered saline and the supernatant fractions were assayed. In vivo: To compare local vs. systemic delivery, mice bearing flank xenografts had intratumoral or contralateral flank IUdR polymer (50% loading) treatments. Mice bearing intracranial (i.c.) xenografts had i.c. vs. flank IUdR polymer treatments. Four or 8 days after implantation of polymers, mice were sacrificed and the percentage tumor cells that were labeled with IUdR was measured using quantitative microscopic immunohistochemistry. For comparisons of radiosensitization, mice bearing i.c. xenografts had i.c. vs. flank IUdR polymers and cranial fractionated external beam irradiation (2 Gy BID x 4 days).

RESULTS

In vitro: Increasing percentage loadings of IUdR resulted in higher percentages of release: 43.7 +/- 0.1, 70.0 +/- 0.2, and 90.2 +/- 0.2 (p < 0.001 ANOVA) for the 10, 30, and 50% loadings, respectively. In vivo: For the flank tumors, both the ipsilateral and contralateral IUdR polymers resulted in similarly high percentages labeling of the tumors vs. time. For the ipsilateral IUdR polymers, the percentages of tumor cellular labeling after 4 vs. 8 days were 45.8 +/- 7.0 vs. 40.6 +/- 3.9 (p = NS. For the contralateral polymer implants, the percentages tumor cellular labeling were 43.9 +/- 10.1 vs. 35.9 +/- 5.2 (p = NS) measured 4 vs. 8 days after implantation. For the i.c. tumors treated with extracranial IUdR polymers, the percentages of tumor cellular labeling were low: 13.9 +/- 8.8 and 11.2 +/- 5.7 measured 4 and 8 days after implantation. For the i.c. tumors having the i.c. IUdR polymers, however, the percentages labeling were comparatively much higher: 34.3 +/- 4.9 and 35.3 +/- 4.0 on days 4 and 8, respectively. For the i.c. tumors, examination of the percentage cellular labeling vs. distance from the implanted IUdR polymer showed labeling was highest closest to the polymer disc. Radiosensitization: For mice bearing i.c. tumors and receiving flank vs. intracranial IUdR polymer treatments, the survival after external beam irradiation was significantly higher for the intracranial treatments: 49 + 8.9 vs. 80 + 4.1 (p = 0.03) days, respectively.

CONCLUSIONS

Implantable biodegradable polymers provide the local, controlled release of IUdR and result in the high, local delivery of IUdR to experimental intracranial human malignant glioma. The local delivery and labeling result in improved survival following radiotherapy. This technique holds promise for the local delivery of IUdR for radiosensitization of human brain tumors.

Synthetic, implantable polymers for local delivery of IUdR to experimental human malignant glioma

PURPOSE

Recently, polymeric controlled delivery of chemotherapy has been shown to improve survival of patients with malignant glioma. We evaluated whether we could similarly deliver halogenated pyrimidines to experimental intracranial human malignant glioma. To address this issue we studied the in vitro release from polymers and the in vivo drug delivery of IUdR to experimental human U251 glioblastoma xenografts.

METHODS AND MATERIALS

In vitro: To measure release, increasing (10%, 30%, 50%) proportions of IUdR in synthetic [(poly(bis(p-carboxyphenoxy)-propane) (PCPP):sebacic acid (SA) polymer discs were serially incubated in buffered saline and the supernatant fractions were assayed. In vivo: To compare local versus systemic delivery, mice bearing flank xenografts had intratumoral or contralateral flank IUdR polymer (50% loading) treatments. Mice bearing intracranial (i.c.) xenografts had i.c. versus flank IUdR polymer treatments. Four or 8 days after implantation of polymers, mice were sacrificed and the percentage tumor cells that were labeled with IUdR was measured using quantitative microscopic immunohistochemistry.

RESULTS

In vitro: Increasing percentage loadings of IUdR resulted in higher percentages of release: 43.7 + 0.1, 70.0 + 0.2, and 90.2 + 0.2 (p < 0.001 ANOVA) for the 10%, 30%, and 50% loadings, respectively. In vivo: For the flank tumors, both the ipsilateral and contralateral IUdR polymers resulted in similarly high percentages labeling of the tumors versus time. For the ipsilateral IUdR polymers, the percentage of tumor cellular labeling after 4 days versus 8 days was 45.8 +/- 7.0 versus 40.6 +/- 3.9 (p = NS). For the contralateral polymer implants, the percentage of tumor cellular labeling were 43.9 +/- 10.1 versus 35.9 +/- 5.2 (p = NS) measured 4 days versus 8 days after implantation. For the i.c. tumors treated with extracranial IUdR polymers, the percentage of tumor cellular labeling was low: 13.9 +/- 8.8 and 11.2 +/- 5.7 measured 4 and 8 days after implantation. For the i.c. tumors having the i.c. IUdR polymers, however, the percentage labeling was comparatively much higher: 34.3 +/- 4.9 and 35.3 +/- 4.0 on days 4 and 8, respectively. For the i.c. tumors, examination of the percentage cellular labeling versus distance from the implanted IUdR polymer showed that labeling was highest closest to the polymer disc.

CONCLUSION

Synthetic, implantable biodegradable polymers provide the local, controlled release of IUdR and result in the high, local delivery of IUdR to experimental intracranial human malignant glioma. This technique holds promise for the local delivery of IUdR for radiosensitization of human brain tumors.

Intravenous delivery of 5'-iododeoxyuridine during hyperfractionated radiotherapy for locally advanced head and neck cancers: results of a pilot study

OBJECTIVES

Locally advanced cancers of the head and neck require aggressive treatment, often with limited effectiveness and significant toxicity and morbidity. This pilot study was designed to assess tolerance using combined hyperfractionated radiotherapy and the halogenated pyrimidine radiosensitizer 5'-iododeoxyuridine (IdUrd).

STUDY DESIGN

This was a prospective single-arm study open to patients with advanced head and neck cancers that had a poor chance of control with conventional radiation therapy. Patients were treated with hyperfractionated radiation therapy at standard doses in combination with an IdUrd infusion and observed for tumor response and normal tissue tolerances.

METHODS

Radiation therapy was delivered in fractions of 1.2 Gy or 1.5 Gy twice daily to a total dose in the range of 70 to 76 Gy. IdUrd was delivered as an intravenous infusion (1000 mg/m2 per day) for a maximum of 14 days at the beginning and then again during the middle of the radiotherapy.

RESULTS

Twelve patients with advanced squamous cell lesions were enrolled and 11 were observed to have complete clinical remissions. Seven patients remained clinically free of local disease at the time of death or most recent follow-up. Acute toxicities, usually hematologic or mucosal, were severe and all patients required treatment modifications and considerable supportive care.

CONCLUSIONS

Although a high rate of response was achieved using this regimen, the toxicities are prohibitive. The kinetic profile of IdUrd incorporation suggests the need for future studies using repetitive short courses of IdUrd.

Quantitative imaging study of extent of surgical resection and prognosis of malignant astrocytomas

OBJECTIVE

This study used quantitative radiological imaging to determine the effect of surgical resection on postoperative survival of patients with malignant astrocytomas. Previous studies relied on the surgeons' impressions of the amount of tumor removed, which is a less reliable measure of the extent of resection.

METHODS

Information concerning possible prognostic factors was collected for 75 patients undergoing magnetic resonance imaging or computed tomography preoperatively and within 10 days postoperatively. Image analysis of the neuroradiological studies was conducted to quantify pre- and postoperative total tumor volumes and enhancing volumes. Univariate and multivariate proportional hazards models were used to analyze the regression of survival regarding 22 covariates that might affect survival. The covariates that were entered included age, gender, tumor grade, cumulative radiation dose, chemotherapy, seizures as a first symptom, Karnofsky performance status at presentation, pre- and postoperative total and enhancing tumor volumes, ratio of pre- to postoperative total and enhancing tumor volumes, tumor location, surgeon's impression of the degree of resection, and subsequent surgery.

RESULTS

There were 23 patients with anaplastic astrocytomas and 52 with glioblastomas multiforme. The estimated mean survival time was 27 months for patients undergoing gross total resection, 33 months for subtotal resection, and 13 months for open or stereotactic biopsy. Five factors that were significant predictors of survival in multivariate analysis were tumor grade, age, Karnofsky performance status, radiation dose, and postoperative complications (P < 0.05). In univariate analysis, tumor grade, radiation dose, age, Karnofsky status, complications, presence of enhancing tumor in postoperative imaging, and postoperative volume of enhancing tumor were significantly associated with survival (P < 0.05).

CONCLUSION

We conclude that the most important prognostic factors affecting survival of patients with anaplastic astrocytomas and glioblastomas multiforme are tumor grade, age, preoperative performance status, and radiation therapy. Postoperative complications adversely affect survival. Aggressive surgical resection did not impart a significant increase in survival time. Surgical resection may improve survival, but its importance is less than that of other factors and may be demonstrable only by larger studies.

[Radiotherapy of glioblastoma]

Glioblastoma cells appear to be inherently radioresistant and to present a significant fraction of hypoxic cells. The most significant prognostic factors to compare results achieved in several series of patients are the age, performance status and quality of surgical resection. Several randomized trials have provided evidence supporting the efficacy of radiation therapy in the treatment of glioblastoma. Prescription of a 60-Gy dose delivered according to a conventional dose-fractionation scheme (single daily fractions of 1.7 to 2 Gy five times per week) in a target volume with a 2-3 cm margin of tissue surrounding the perimeter of the contrast enhancing lesion on computerized tomography and magnetic resonance imaging is derived from observations made in several retrospective and prospective studies. Evidence of improvement in survival was observed neither in patients receiving hyperfractioned and accelerated radiotherapy, nor in patients for whom radiation sensitizers such as nitroimidazole compounds or halogenated pyrimidine analogs were associated to radiation therapy. The addition of nitrosourea to radiotherapy increases the 2-year survival rate by about 10%. Combination of full-dose external beam radiotherapy and brachytherapy or radiosurgery boost in selected patients with glioblastoma leads to an increase in the median survival, while external beam radiation alone in patients with similar prognosis does not.

Hyperfractionated and accelerated radiation therapy in central nervous system tumors (malignant gliomas, pediatric tumors, and brain metastases)

The authors review the main contributions of the international literature concerning the role of hyperfractionation (HF), accelerated fractionation (AF), and accelerated hyperfractionation (AHF) of the dose in radiation therapy (RT) of central nervous system tumors. Basic rationales, clinical results, acute/late toxicity, and current prospectives are summarized in three sections focusing on malignant gliomas, pediatric brainstem tumors, and brain metastases. In supratentorial malignant gliomas the superiority of AHF (0.89 Gy x 3 fractions/day; total dose 61.4 Gy) over conventional fractionation ((CF) total dose 58 Gy) was demonstrated by a randomized trial. However, the gain in median survival time was less than 6 months. No other randomized trials support the preferential choice of non-CF schedules outside clinical trials. Ongoing trials are exploring the role of AHF in combination with chemotherapy, hypoxic cell and radiosensitizing agents. As for pediatric brainstem tumors, there are no data to support the routine use of HF that should be preferably used in an investigative setting. As late sequelae have been reported in the few long-term survivors, patients should be carefully selected. Regarding brain metastases AF RT and AHF RT, with their faster treatment course, may represent a convenient alternative to CF RT for the palliation of brain metastases. In carefully selected patients with solitary brain metastases non-CF RT may be part of aggressive treatment approaches.

Implantable biodegradable polymers for IUdR radiosensitization of experimental human malignant glioma

PURPOSE

The potential of halogenated pyrimidines for the radiosensitization of human malignant gliomas remains unrealized. To assess the role of local delivery for radiosensitization, we tested a synthetic, implantable biodegradable polymer for the controlled release of 5-iodo-2'-deoxyuridine (IUdR) both in vitro and in vivo and the resultant radiosensitization of human malignant glioma xenografts in vivo.

MATERIALS AND METHODS

In vitro: To measure release, increasing (10%, 30%, 50%) proportions (weight/weight) of IUdR in the polyanhydride [(poly(bis(p-carboxyphenoxy)-propane) (PCPP): sebacic acid (SA) (PCPP : SA ratio 20:80)] polymer discs were incubated (1 ml phosphate-buffered saline, 37 degrees C). The supernatant fractions were serially assayed using high performance liquid chromatography. To measure modulation of release, polymer discs were co-loaded with 20 microCi 5-125-iodo-2'-deoxyuridine (125-IUdR) and increasing (10%, 30%, or 50%) proportions of D-glucose. To test radiosensitization, cells (U251 human malignant glioma) were sequentially exposed to increasing (0 or 10 microM) concentrations of IUdR and increasing (0, 2.5, 5.0, or 10 Gy) doses of acute radiation. In vivo. To measure release, PCPP : SA polymer discs having 200 microCi 125-IUdR were surgically placed in U251 xenografts (0.1-0.2 cc) growing in the flanks of nude mice. The flanks were reproducibly positioned over a collimated scintillation detector and counted. To measure radiosensitization, PCPP : SA polymer discs having 0% (empty) or 50% IUdR were placed in the tumor or contralateral flank. After five days, the tumors were acutely irradiated (500 cGy x 2 daily fractions).

RESULTS

In vitro: Intact IUdR was released from the PCPP : SA polymer discs in proportion to the percentage loading. After 4 days the cumulative percentages of loaded IUdR that were released were 43.7 +/- 0.1, 70.0 +/- 0.2, and 90.2 +/- 0.2 (p < 0.001 ANOVA) for the 10, 30, and 50% loadings. With 0, 10, 30, or 50% D-glucose co-loading, the cumulative release of 125-IUdR from PCPP : SA polymers was 21, 70, 92, or 97% (p < 0.001), respectively, measured 26 days after incubation. IUdR radiosensitized U251 cells in vitro. Cell survival (log10) was -2.02 +/- 0.02 and -3.68 +/- 0.11 (p < 0.001) after the 10 Gy treatment and no (control) or 10 microM IUdR exposures, respectively. In vivo: 125-IUdR Release: The average counts (log10 cpm +/- SEM) (hours after implant) were 5.2 +/- 0.05 (0.5), 4.3 +/- 0.07 (17), 3.9 +/- 0.08 (64), and 2.8 +/- 0.06 (284). Radiosensitization: After intratumoral implantation of empty polymer or intratumoral 50% IUdR polymer, or implantation of 50% IUdR polymers contralateral to tumors the average growth delays of tumors to 4 times the initial volumes were 15.4 +/- 1.8, 20.1 + 0.1, and 20.3 + 3.6 (mean + SEM) days, respectively (p = 0.488 one-way ANOVA). After empty polymer and radiation treatments, no tumors regressed and the growth delay was 31.1 + 2.1 (p = 0.046 vs. empty polymer alone) days. After implantation of 50% IUdR polymers either contralateral to the tumors or inside the tumors, followed by radiation, tumors regressed; growth delays to return to the initial average volumes of 14.0 + 3.6 or 24.2 + 0.2 (p < 0.01) days, respectively.

CONCLUSIONS

Synthetic, implantable biodegradable polymers hold promise for the controlled release and local delivery of IUdR for radiosensitization of gliomas.

Incorporation of iododeoxyuridine in multicellular glioma spheroids: implications for DNA-targeted radiotherapy using Auger electron emitters

A promising new treatment for glioma involves Auger electron emitters such as 125I or 123I conjugated to deoxyuridine (IUdR). However, the presence in tumour deposits of non-proliferating cells with clonogenic potential poses a major limitation to this cycle-specific therapy. We have used multicellular tumour spheroids derived from the human glioma cell line UVW to study [125I]IUdR-targeted radiotherapy in aggregates containing cells in different proliferative states. Autoradiographic identification of labelled cells indicated that nuclear incorporation of [125I]IUdR decreased markedly with increasing size of spheroid. IUdR incorporation was maximal in the surface layer of cells and decreased with depth within spheroids. Radiopharmaceutical uptake corresponded closely to the regions of cell cycling as indicated by staining for the nuclear antigen Ki67. The uptake of drug was enhanced by increasing the duration of incubation from 52 h to 104 h. These observations suggest that significant sparing of non-cycling malignant cells would result from treatment delivered as a single injection of radiolabelled IUdR. To achieve maximal therapeutic effect. IUdR should be administered by multiple injections, by slow release from biodegradable implants or by slow-pump delivery.

Survival improvement in anaplastic astrocytoma, combining external radiation with halogenated pyrimidines: final report of RTOG 86-12, Phase I-II study

PURPOSE

This study evaluated the toxicity and tumor efficacy of the halopyrimidine IUdR as a chemical modifier of radiation response in patients with malignant glioma. The preliminary results published in 1993 demonstrated no real advantage in the group of patients with glioblastoma. However, a benefit appeared to be evolving in the group of patients with Anaplastic Astrocytoma (AA). We are now presenting the results on the long-term follow-up of patients with AA.

METHODS AND MATERIALS

Between August 1987 and October 1991, 79 patients were entered in a prospective study with newly diagnosed malignant glioma. Twenty-one of 79 were AA. The study was designed to have a fixed dose of radiation consisting of 60.16 Gy in 32 fractions in 6.5 weeks but varying the dose schedule of IUdR, delivered in a continuous intravenous infusion of long (96 h) or short (48 and 24 h) duration, every week for the 6.5 weeks of radiation treatment.

RESULTS

The last AA patient was entered in March 1991. Ninety-five percent of the AA patients were under 59 years of age and 86% had a Karnofsky score 80. Thirty-eight percent had a tumor diameter of less than 5 cm and 52% had a tumor diameter between 5-10 cm. Seventy-six percent had partial or total tumor resection. The toxicity of this treatment was acceptable and has already been published elsewhere. At the time of this report, 14 out of 21 patients with AA are dead. The median survival, calculated from the Kaplan-Meier, is 3.2 years. Thirty-three percent of the patients have survived 5 years. These results compare favorably with the best results reported in the literature with postoperative external radiation plus chemotherapy, median survival time (MST) of 3 years, and previous Radiation Therapy Oncology Group (RTOG) experience with radiation alone, MST of 2 years.

CONCLUSIONS

Our findings in patients with AA corroborate the improved therapeutic results published recently when combining external radiation with "long" infusion of i.v. BUdR and indicate the need to proceed with randomized Phase III studies utilizing halogenated pyrimidines and radiation. One such study has already been activated, RTOG # 94-04.

Early postoperative magnetic resonance imaging following nonneoplastic cortical resection

Postcraniotomy residual tumor is often determined by magnetic resonance (MR) imaging. Magnetic resonance changes that occur in the postoperative setting must be defined to ensure both the optimum timing of postoperative image acquisition and the accurate assessment of images for residual tumor. Postoperative changes in nontumor parenchyma have previously been described for computerized tomography but not for MR imaging. In the present study, 11 patients without intracranial neoplastic disease (six females and five males with a median age of 36 years) submitted to MR imaging 17 to 28 hours after undergoing temporal lobectomies for epilepsy. Four of the operations were performed with the patients under general anesthesia and seven under local anesthesia. Postoperative MR images (T1-weighted, T1-weighted gadolinium enhanced, and T2-weighted) were reviewed. Extraaxial fluid, air, or blood was present in all cases. Enhancement of the resection bed parenchyma occurred in seven (64%) of 11 patients. In three of the remaining four patients, assessment of parenchymal enhancement was obscured by extraaxial fluid collections. Dural enhancement occurred adjacent to the resection site in all of the cases and remotely in 73%. Eight (73%) of 11 patients displayed enhancement of the pia-arachnoid of the ipsilateral cerebral convexity, two (18%) of the contralateral convexity, and four (36%) of the pia-arachnoid overlying the cerebellum. Contrary to previous reports, contrast enhancement of nonneoplastic human brain parenchyma can occur postoperatively within 17 hours. Benign parenchymal contrast enhancement is usually linear in appearance; nonneoplastic dural and leptomeningeal enhancement can occur both adjacent to and distant from the surgical site. Extraaxial fluid collections can hinder MR evaluation of the resection bed.

Brain tumors

This synthesis of the literature on radiotherapy for brain tumors, ie, cancer originating in the central nervous system (CNS), is based on 81 scientific articles, including 25 randomized studies, 13 prospective studies, and 25 retrospective studies. These studies involve 11,081 patients. A more comprehensive chapter on brain tumors may be ordered from SBU. Curative treatment is not available for patients with highly malignant glioma (grades III and IV). Postoperative radiotherapy for highly malignant glioma extends patients' survival, with good quality of life, by several weeks to several months. Virtually all patients die from this disease. Although the clinical benefits from radiotherapy, measured as survival, appear to be modest, it is more effective than any chemotherapy tested thus far. The clinical effects of radiotherapy for highly malignant glioma are improved only marginally by altering factors such as absorbed dose, fractionation, irradiated tissue volume, radiation quality, or by adding radiosensitizing substances. Radiotherapy alone usually provides a clear but temporary improvement in patients with highly malignant glioma, hence it clearly has a palliative benefit. Postoperative radiotherapy for low-grade malignant gliomas (grades I and II) may extend survival. It also reduces tumor volume. No evidence shows that radiotherapy alone or postoperatively can lead to cure. In patients who have undergone subtotal meningioma resection, postoperative radiotherapy substantially reduces the risk for recurrence and extends life, and is thereby indicated. Radiotherapy is not indicated following macroscopic radical meningioma surgery. Patients with brain metastases experience rapid neurological improvement following radiotherapy to the whole brain, and this palliative effect often remains throughout the remainder of the patient's life. Palliative radiotherapy, often to large volumes of the CNS, is therefore motivated in a large proportion of the patient groups. In a smaller group of patients with solitary metastases, radiotherapy may be given postoperatively following radical neurosurgery. Life may be extended in this group, otherwise radiotherapy does not influence survival. Stereotactic radiotherapy of solitary, mainly spherical metastases in the brain is often superior to other known methods with respect to palliation and survival. The number of patients is, however, relatively small.

Five-chlorodeoxycytidine and biomodulators of its metabolism result in fifty to eighty percent cures of advanced EMT-6 tumors when used with fractionated radiation

PURPOSE

To extend our findings in previous radiation and biochemical studies with five rodent tumors, in which we used one and occasionally two or three irradiations. The extent of control of the EMT-6 mammary adenocarcinoma was determined using fractionated radiation (12 irradiations) over a 3-week period using the radiosensitizer 5-chloro-2'-deoxycytidine (CldC) and biomodulators of its metabolism: N-(Phosphonacetyl)-L-aspartate (PALA), tetrahydrouridine and 5-fluoro-2'-deoxycytidine (FdC).

METHODS AND MATERIALS

Mammary adenocarcinoma EMT-6 tumors implanted 1 week prior to therapy in BALB/c mice were subjected to single daily doses of focused radiation, not exceeding a total of 60 Gy, on days 2-5 of each week. N-(Phosphonacetyl)-L-aspartate (PALA) was administered on the first day of therapy. Five-fluoro-2'-deoxycytidine and CldC were administered in the morning and afternoon, respectively, of the next 2 days, and CldC was administered on the fourth day. Tetrahydrouridine was always coadministered with FdC or CldC. Drug and radiation treatments overlapped for 3 weeks.

RESULTS

Fifty to 80% cures (usually 70%) were obtained with no apparent morbidity and the same moderate weight loss that occurs with radiation alone. Neither tumor regrowth delay nor cures were obtained with drugs or radiation alone. An apparent threefold dose increase effect was obtained with the end point: "days to reach 4 times initial tumor volume." Increasing the radiation dose threefold (without drugs) resulted in four out of five deaths; increasing the dose twofold (without drugs) resulted in extensive weight loss and hair loss in the entire ventral area and no cures. Increasing the dose of drugs or radiation 1.5-fold, in the complete protocol, did not result in increased morbidity. Comparative studies with Iododeoxyuridine demonstrate the heightened efficacy of CldC.

CONCLUSIONS

One cannot achieve the same results obtained with CldC and the modulators by merely increasing the dose of radiation. There is a significant window of safety in this approach. The evidence we have obtained with EMT-6, the fifth rodent tumor we have studied with CldC, as well as the demonstrated and proposed reasons for its superior efficacy over 5-Iododeoxyuridine (and 5-Bromodeoxyuridine), drugs in current use, indicate that CldC will allow more aggressive treatment of human tumors with radiation than is now feasible.

Preoperative radiation therapy and iododeoxyuridine for large retroperitoneal sarcomas

PURPOSE

Local failure is frequent after conventional therapy for patients with retroperitoneal sarcomas. A Phase I/II multimodality approach was used, combining iododeoxyuridine (IdUrd) and radiation therapy, followed by attempted surgical resection, with the goal of improving local control.

METHODS AND MATERIALS

Patients with retroperitoneal sarcomas were treated with three to five consecutive cycles of treatment. Each 14-day cycle consisted of a continuous intravenous infusion of IdUrd on days 1-5, twice a day radiation therapy (1.25 Gy/fraction) on days 8-12, and a break on day 13 and 14. Surgical resection was attempted after three or five cycles. Patients resected after three cycles received an additional two cycles of treatment with radiation directed to the tumor bed. IdUrd dose was escalated in Phase I fashion (1000 mg/m2/day, 1333 mg/m2/day, and 1600 mg/m2/day). The median potential follow-up was 31 months.

RESULTS

Sixteen patients (13 with high grade tumors) were treated. The median maximum tumor size was 17 cm. Resection margins were negative in four patients, microscopically positive in four patients, and grossly positive in three patients. Five patients were not resected. The only grade 4 acute toxicity observed was vomiting which occurred in three patients receiving upper abdominal radiation. Postsurgical and long-term complications were rare. Median survival overall and for resected patients were 18 and 32 months, respectively. Local control was observed in three out of four patients with negative margins (9, 40+, and 51+ months), two out of four patients with microscopically positive margins (4 and 22 months), and one out of three patients with grossly positive margins (46+ months). The overall freedom from local progression was 45% at 24 months.

CONCLUSION

Retroperitoneal sarcomas can be resected after preoperative radiation therapy and IdUrd, with encouraging local control in patients resected with negative or microscopically positive margins. The recommended dose using this drug and radiation schedule appears to be 1600 mg/m2/day, which will form the basis for a Phase II trial.

National Cancer Institute (phase II) study of high-grade glioma treated with accelerated hyperfractionated radiation and iododeoxyuridine: results in anaplastic astrocytoma

PURPOSE

We report the outcome of a Phase II study of a cohort of patients with high-grade glioma treated with accelerated hyperfractionated radiation and the radiation sensitizer, iododeoxyuridine (IdUrd).

METHODS AND MATERIALS

Between January 1988 and December 1990, 39 consecutive patients with high-grade glioma were enrolled and treated on a Phase II protocol including hyperfractionated radiation and IdUrd. Thirty-two patients were male and seven were female. Age range was 19 to 71 years with a median age of 38 years. IdUrd (1000 mg/m2 per day) was administered in two separate 14-day courses, the first during the initial radiation field and the second during the final cone-down field. All patients were treated consistently with partial brain technique and received 1.5 Gy/fraction twice daily to a mean total dose of 71.25 Gy (range 66-72 Gy excluding one patient who did not complete treatment). The initial field was treated to 45 Gy followed by a cone-down field covering the tumor volume plus a 1-cm margin to the final dose. Patients were assessed for acute and long-term morbidity and followed for outcome. Two patients had biopsies during the course of treatment. Flow cytometry and high performance liquid chromatography was used to evaluate the labeling index and the percent replacement of IdUrd in the biopsy specimen.

RESULTS

Thirty-eight of 39 patients completed therapy. One patient died on treatment at 48 Gy and is included in the survival analysis. No patient was lost to follow-up. Twenty-one patients had Grade 3 (anaplastic astrocytoma) tumors and 18 patients had Grade 4 (glioblastoma multiforme). Median survival for the entire cohort was 23 months. For the glioblastoma multiforme patients, median survival was 15 months. The median survival of the anaplastic astrocytoma patients has not yet been reached. In the patients assessed, the range of IdUrd tumor cell incorporation was only 0-2.4%.

CONCLUSION

Accelerated hyperfractionated radiation therapy with IdUrd was administered with acceptable acute toxicity. The major acute side effects of mucositis and thrombocytopenia were related to IdUrd infusion and were dose-dependent. There were no unacceptable acute toxicities referable to the radiation as delivered. With a median potential follow-up of 51 months, the actuarial median survival of the glioblastoma multiforme patients is comparable with the best previously published reports. The outcome of patients with anaplastic astrocytoma compares very favorably with even the most aggressive multi-modality approaches in the recent literature with a minimum of acute morbidity.

Bromodeoxyuridine-mediated radiosensitization in human glioma: the effect of concentration, duration, and fluoropyrimidine modulation

PURPOSE

To define the relative influence of duration of exposure, concentration, and modulation by fluorodeoxyuridines (FdUrd) on the incorporation of 5-bromo-2-deoxyuridine (BrdUrd) into DNA of a human malignant glioma line (D-54) in vitro and in vivo.

MATERIALS AND METHODS

IN VITRO STUDIES

an established human malignant glioma line (D-54) was exposed to a clinically achievable concentration of BrdUrd to model intravenous (1 microM BrdUrd) and intraarterial (4 microM BrdUrd) conditions. The influence of modulation was assessed using 1 nM FdUrd. Incorporation of BrdUrd, radiosensitization, and cytotoxicity were determined after 24, 72, and 120 h drug exposures. In Vivo studies: nude mice bearing D-54 xenografts were infused with BrdUrd at 100 mg/kg/day for 7 and 14 days or BrdUrd at 400 mg/kg/day for 5 days. The influence of modulation was assessed by combining 100 mg/kg/day of BrdUrd with 0.1, 0.3, and 1 mg/kg/day FdUrd for 7 days. Incorporation of BrdUrd into the DNA of tumor, gut, and marrow were determined.

RESULTS

In Vitro: thymidine replacement and radiosensitization were a function of concentration, and incorporation began to plateau after 2 to 3 population doublings. Modulation with 1 nM FdUrd significantly increased incorporation. Radiosensitization was a linear function of thymidine replacement under all conditions tested. In Vivo: infusion with 400 mg/kg/day for 5 days resulted in greater tumor incorporation (10.3 +/- 0.4% thymidine replaced) than treatment with 100 mg/kg/day for 14 days (6.0 +/- 0.6% of thymidine replaced). Infusion of FdUrd with BrdUrd increased normal tissue incorporation of BrdUrd, but failed to increase BrdUrd incorporation in tumor cells.

CONCLUSION

These results suggest that relatively short, high dose rate infusions may be preferable to long, low dose rate infusions. The potential benefit of FdUrd modulation demonstrated in vitro may be difficult to realize using continuous systemic infusions.

Kinetics of cell labeling and thymidine replacement after continuous infusion of halogenated pyrimidines in vivo

PURPOSE

Iododeoxyuridine (IdUrd) is a halogenated pyrimidine which has been recognized as a clinical radiosensitizer. It is generally agreed that the extent of radiosensitization correlates with the degree of thymidine substitution in DNA. Controversy exists regarding the optimal administration schedule to achieve maximum radiosensitization. To obtain more information relating to this problem, we present experiments on an in vivo human tumor xenograft continuously exposed to a fixed serum concentration of halogenated pyrimidines so as to study the kinetics of cell labeling and thymidine replacement.

METHODS AND MATERIALS

Human colon tumor (HCT-116) cells were injected subcutaneously into nude mice. After 10 days, most animals (> 90%) developed measurable tumor nodules with a volume doubling time of 5 +/- 1 days. Once the tumors reached a cross-sectional area of 0.25-0.30 cm2, miniosmotic pumps were implanted to deliver a dose of 100 mg/kg/day of IdUrd by continuous infusion. After an IdUrd exposure time of 1-7 days, blood and tumor tissue were collected.

RESULTS

The steady state serum IdUrd concentration was 0.95 +/- 0.1 microM, which is a clinically relevant concentration for a prolonged continuous intravenous infusion. The tumor cell potential doubling time (Tpot) was 25 +/- 2 h. The percent IdUrd thymidine replacement and the fraction of cells labeled, followed exponential saturation kinetics with a halflife of 33 +/- 9 and 27 +/- 2 h, respectively. After 5 days of exposure (congruent to 5 x Tpot), the thymidine replacement in tumor cells was 2.0 +/- 0.2% and the fraction of tumor cells labeled was 94 +/- 1%. Immunohistochemical staining of IdUrd labeled tumor tissues showed an exposure dependent gradient of cellular labeling that was initially highest in regions close to blood vessels. After 4 days of exposure at 100 mg/kg/day, there was an increase in the fraction of cells in G(0) + G1 and a decrease in the S phase population, suggesting a block between G1 and S phase.

CONCLUSION

We conclude that the in vivo kinetics of IdUrd thymidine replacement and fraction of cells labeled after continuous exposure followed exponential saturation kinetics with a halflife of approximately the potential doubling time of the tumor cell population. Simple modeling suggests that some form of prolonged, or briefly interrupted, continuous infusion should be considered for clinical administration because such schedules would leave fewer cells unsensitized than shorter infusions would. Even 10% of unlabeled clonogenic cells could explain the lack of dramatic clinical successes with IdUrd or BrdUrd sensitization.

The application of 5-bromodeoxyuridine in the management of CNS tumors

A variety of clinical reports have described the application of the bromodeoxyuridine labeling index as an adjunct to conventional pathological examination of CNS tumors. This index has proven useful in predicting the clinical outcome associated with many such tumors. Furthermore, because of its efficacy as a radiosensitizing agent, bromodeoxyuridine (and the closely related iododeoxyuridine) has been used in combination with radiation therapy for malignant glial neoplasms, with some encouraging results. Although most studies suggest that bromodeoxyuridine is safe, there is evidence that this compound does have potential side-effects, including the observation that it is a mutagen and carcinogen in some experimental systems. A number of new alternative approaches for predicting the clinical outcome of CNS tumors has been developed based on an increased understanding of their molecular biology. However, until such approaches are better characterized, the clinical application of bromodeoxyuridine will continue to play an important role in predicting the clinical behavior of many CNS tumors.

Influence of extent of surgery and tumor location on treatment outcome of patients with glioblastoma multiforme treated with combined modality approach

Between 1988 and 1991, eighty-six patients with glioblastoma multiforme were evaluated in order to define the influence of extent of surgery and tumor location on treatment outcome. Patients underwent surgery followed by postoperative hyperfractionated radiotherapy and chemotherapy delivered according to one of two consecutive protocols. Surgery consisted of biopsy in 25 (29%) patients and subtotal or gross total tumor resection in 61 (71%) patients. Frontally located tumors were noted in 26 (30%) patients and other tumor locations were noted in 60 (70%) patients. Patients having more radical surgery had longer median survival time (MST) and higher 1- and 2-year survival rates than those with biopsy only (56 vs 29 weeks, respectively; 62% and 23% vs 16% and 0%, respectively; p = 0.00000). Patients having frontally located tumors had longer MST and higher 1- and 2-year survival rates than those with other tumor locations (101 vs 47 weeks, respectively; 76% and 44% vs 37% and 2.5%, respectively; p = 0.00001). Multivariate analysis confirmed that extent of surgery and tumor location were independent prognostic factors in patients with glioblastoma multiforme. Regarding progression-free survival, patients having more radical surgery had longer median time to tumor progression (MTP) than those with biopsy only (33 weeks vs 21 weeks, respectively). Also, progression-free survival at 1 year was higher in radically resected group than in biopsy only group (20% vs 0%, respectively; p = 0.00000). Patients with frontally located tumors had longer MTP (42 weeks) and higher progression-free survival at 1 year (42%) than those with other tumor location (28 weeks and 1.7%, respectively; p = 0.00002).(ABSTRACT TRUNCATED AT 250 WORDS)

Iododeoxyuridine (IUdR) combined with radiation in the treatment of malignant glioma: a comparison of short versus long intravenous dose schedules (RTOG 86-12)

PURPOSE

To evaluate the toxicity and tumor efficacy of the halopyrimidine IUdR (NSC #39661, IND 22475) as a chemical modifier of radiation response when used in a high dose short time infusion versus the acceptable 4 day infusion.

METHODS AND MATERIALS

In August 1987 we initiated a prospective study in patients with newly diagnosed anaplastic astrocytoma and glioblastoma. The study was designed to have a fixed dose of radiation (60.16 Gy = 1.88 Gy in 32 fractions in 6.5 weeks) but varying the dose schedule of IUdR, keeping the total dose between 21 and 24 g/m2. IUdR was delivered in a 96, 48, or 24 hr continuous intravenous infusion per week for 6.5 weeks during radiation treatment.

RESULTS

The study was closed for patient accrual on October 1, 1991. Twenty-two patients were treated on the 96 hrs, 32 on the 48 hr and 25 on the 24 hr schedules. The incidence of glioblastoma ranged between 68 and 75% in the three arms. Seventy percent of the patients had a Karnofsky of 80-90% at the onset of treatment. Over 50% of the patient population were under age 55. Drug tolerance was related to the duration of the IUdR infusion. Toxicities were most pronounced in the 96 hr IUdR infusion schedule where 27.4% of the patients reported a grade 3 drug toxicity. No fatal or grade 4 toxicities were observed. More patients on the 24 and 48 hr schedule received at least 80% of the IUdR dose specified per protocol. We did not observe a trend in acute normal tissue radiation reactions in any of the three arms. The median survivals calculated from the Kaplan-Meier plot are 13.4, 10.5, and 11 months, respectively, for the 96, 48, and 24 hr infusions. The Cox Proportional Hazards model showed that any difference in survival can be attributed to histological grade, type of previous surgery and, to some extent, age of the patient. Dose schedule was not a significant predictor of survival, although statistically nonsignificant trend toward longer survival is seen in those patients with glioblastoma treated in the "long" 4 day schedule.

CONCLUSION

Overall, our treatment combination, particularly for patients with glioblastoma, has not shown convincing evidence of an improvement in survival. Of interest, however, it is the 2 year survival rate of 68% for patients with anaplastic astrocytoma. In our experience, the administration of IUdR is laborious, time consuming and with bothersome acute gastrointestinal and hematological toxicities.

The clinical rationale for S-phase radiosensitization in human tumors

Nonhypoxic cell radiosensitizers, principally the halogenated pyrimidines and hydroxyurea, have been studied in the laboratory and clinical setting for more than 30 years. Early clinical experience in the 1960s and 1970s with the thymidine analogs 5-bromodeoxyuridine (BUdR) and 5-iododeoxyuridine (IUdR) was disappointing because normal tissue toxicity eliminated any potential for therapeutic gain. Inadequate delivery systems for intravenous and intraarterial infusions also contributed to the decline of this strategy. More recently, laboratory investigations have revealed further information regarding the mechanism of IUdR/BUdR radiosensitization. This knowledge provided a rationale for the sequence and timing of drug and radiation exposure, which could be both effective and tolerable. Advancing technology also provided safer infusion devices, and a resurgence in clinical trials combining IUdR or BUdR and radiation resulted. Current laboratory studies are now providing data on tumor cell kinetics, which is being applied to ongoing clinical trials. Fluoropyrimidines, principally 5-fluorouracil (5-FU), were also used in early clinical trials and unlike IUdR/BUdR were found to have significant activity as single agents against a variety of tumor types. The clinical integration of 5-FU and radiation occurred more slowly, but recent trials have demonstrated a therapeutic gain. Improved rates of local control and survival with combined 5-FU and radiation versus radiation alone have now been demonstrated in patients with rectal, esophageal, and anal carcinomas. However, the mechanism of interaction between the fluoropyrimidines and radiation remains uncertain and continues to be investigated with the hope of improved clinical outcome. As the cellular pathways influenced by the halogenated pyrimidines have been defined, the potential for biochemical modulation of these agents has been recognized. Leucovorin, the most commonly applied modulator, has been shown to enhance the activity of 5-FU in patients with metastatic colorectal carcinoma. These studies serve as an example for current trials that use biochemical modulators of IUdR, BUdR, and 5-FU as radiosensitizers. Hydroxyurea, currently used in the treatment of chronic leukemia, has also been considered a radiosensitizer. As with IUdR/BUdR, the clinical trials have often been inconclusive and interest in this radiosensitizer has waned. A poor understanding of the mechanism of action and tumor cell/normal tissue kinetics may be responsible for the lack of overall success with this strategy. Current investigations of cell kinetics in humans and potential mechanisms of hydroxyurea action could provide information critical to future trials of hydroxyurea radiosensitization.

5-Fluorouracil, hydroxyurea and escalating doses of iododeoxyuridine with concomitant radiotherapy for malignant gliomas: a clinical and pharmacologic analysis

BACKGROUND

Iododeoxyuridine (IUdR) is a known radiation enhancer, and interacts biochemically with 5-fluorouracil (5-FU) and hydroxyurea (HU).

PATIENTS AND METHODS

IUdR was added to the previously studied regimen of continuous infusion 5-FU at 300 mg/m2/day for 5 days, HU 500 mg every 12 hours for 11 doses and radiotherapy 200 cGy/day for 5 days, all administered for 7 consecutive weeks to patients with malignant glioma. IUdR was administered as 5-day continuous intravenous infusion during weeks 1 and 4. The IUdR dose was changed in cohorts of patients. IUdR plasma concentrations were determined during weeks 1 and 4, and IUdR incorporation into the DNA of granulocytes was measured on weeks 2 and 5.

RESULTS

Two patients treated at the initial IUdR dose of 500 mg/m2/day developed grade 3 or 4 myelosuppression and mucositis. Additional dose levels of IUdR tested were 250 mg/m2/day and 125 mg/m2/day; at the latter dose, severe or life-threatening toxicity was seen in only 3 of 8 patients treated. IUdR incorporation into DNA of granulocytes was 10.5(+/- 2.3)% at an IUdR dose of 500 mg/m2/day but decreased to 0.76(+/- 0.3)% at 125 mg/m2/day. Similarly, IUdR plasma concentrations decreased from 436 (+/- 114) ng/ml to 99 (+/- 29) ng/ml.

CONCLUSIONS

The addition of IUdR to 5-FU and HU results in significant systemic toxicity necessitating limitation of the IUdR dose to 125 mg/m2/day. There is a significant biochemical interaction between IUdR, 5-FU and HU leading to increased IUdR incorporation into DNA and to substantial clinical toxicity. Further clinical studies to exploit this interaction at more feasible schedules may be useful.

Radiation therapy for malignant astrocytomas in adults

High grade (or malignant) astrocytomas remain a formidable therapeutic challenge. The main prognostic factors are patient age, patient performance status, tumor grade, the extent of surgical resection and the presence of fits. These factors could help to identify different groups of patients and should be an advantage in deciding on treatment strategies. Modern imaging techniques provide a more precise idea of tumor volume. The study of tumor recurrence shows that they occur in the immediate vicinity of the primary site. Surgery aside, radiotherapy remains the most important treatment modality. Currently, its standards concerning optimal dose and target volume appear to be accepted overall. There is no doubt that a dose-response relation exists; however, doses exceeding 60 Gy increase morbidity. Therefore 60 Gy is the dose most often cited in the literature. Furthermore, as whole brain irradiation does not decrease the risk of recurrence, a focal irradiation including a defined mean volume is generally used today. Radiosensitizers and heavy particles have not fulfilled their initial promise. Brachytherapy remains an interesting alternative for a limited number of patients. Nevertheless, it seems to increase recurrence at a distance from the primary site and to lead to severe focal lesions. Interstitial thermoradiotherapy may minimize local doses and thus help avoid serious local necrosis. Amongst the other therapeutic alternatives, intravenous chemotherapy using nitrosoureas provides a certain but modest benefit. Other administration modalities are currently undergoing evaluation. These include intra-arterial chemotherapy or high dose chemotherapy with auto-bone marrow transplantation. The interest of this latter is concerned mainly with anaplastic astrocytomas. Finally, among the future alternatives, gene therapy appears to hold the most promise. Intensive therapies, combined modality treatments, with the recent help of biological innovations, should be proposed to favorable groups of patients.

Correlation of sensitizer enhancement ratio with bromodeoxyuridine concentration and exposure time in human cervical carcinoma cells treated with low dose rate irradiation

The effect of a range of bromodeoxyuridine concentrations and exposure times on the sensitizer enhancement ratio of two human cervical carcinoma cell lines treated with low rate irradiation was evaluated. Both cell lines show a linear, though different, dose response to low dose rate irradiation at dose rates up to 0.62 Gy/hr. Cells were pre-incubated with 0, 1, 5, or 10 microM bromodeoxyuridine for 0, 24, or 48 hr prior to low dose rate irradiation. Based on the survival of cells exposed to 4 Gy, delivered at 0.62 Gy/hr, a slope was determined for an exponential survival curve for each bromodeoxyuridine concentration and exposure time. Sensitizer enhancement ratios were calculated as the ratio of the slopes of the treated and untreated cells from a particular exposure time. Ratios increased linearly initially with a plateauing at higher levels with respect to the product of bromodeoxyuridine concentration and time of exposure for both cell lines with similar degrees of enhancement. A linear relationship has been noted previously for acute irradiation of hamster cells over a similar range of sensitizer concentrations and exposure times. At the highest dose-time points (540 microM-hr) ratios of greater than 2 were attained, which were comparable to results obtained following acute radiation exposures of V-79 cells. These results demonstrate that significant sensitizer enhancement ratios with low dose irradiation can be obtained in human tumor cells after exposures of 2 to 3 doubling times using relatively low concentrations of sensitizer.

Heterogeneity in response to treatment with buthionine sulfoximine or interferon in human malignant glioma cells

Two tumor cell lines were established from each of three human malignant glioma biopsy specimens (M059, M067, M071) and sensitivity to treatment with radiation or chemotherapeutic agents (BCNU, nitrogen mustard) was determined. The effects of recombinant human interferon-alpha (rIFN) on the radiation response and of buthionine sulfoximine (BSO) on the drug response were investigated as well. For tumor M059, two cell lines that differed significantly in radiosensitivity were isolated (surviving fractions at 2 Gy = 0.02 and 0.64). The chemosensitivity and response to chemical modification differed as well. Cell lines established from tumor M071 differed in their response to rIFN only and were not sensitized by BSO. M067 cell lines showed little difference and were not sensitized by either agent. These results suggest that differences may exist both within and among human malignant gliomas with regard to their sensitivity to drugs, radiation, and the ability of chemical agents to modify treatment responses.

Radiosensitivity testing of human primary brain tumor specimens

The inherent radiosensitivity of early passage cells derived from 22 patients with tumors of glial origin has been determined using a clonogenic assay system. The mean (+/- SD) surviving fraction at 2 Gy was 0.37 +/- 0.22 (range = 0.02-0.87). No correlation between inherent radiosensitivity and tumor cell plating efficiency or intracellular glutathione was observed. Tumor cells that were both resistant to nitrosoureas and expressed the Mer+ phenotype did not differ significantly in their radiosensitivity as compared to cells that were repair deficient (Mer-) and sensitive to nitrosoureas. Initial clinical follow-up suggests that factors in addition to inherent tumor cell radiosensitivity, such as performance status and age, continue to be the most important determinants of the response of patients with primary brain tumors to radiotherapy.

Radiotoxicity of 17 alpha-[125I]iodovinyl-11 beta-methoxyestradiol in MCF-7 human breast cancer cells

Therapeutic strategies for human breast cancer using 125I-labeled steroid hormones are clinically attractive in light of the estrogen dependence of many human breast cancers and the favorable microdosimetry resulting from 125I decay. We determined the uptake specific estrogen receptor binding and radiotoxicity of 17 alpha-[125I]iodovinyl-11 beta-methoxyestradiol (125IVME2) in vitro using cultured MCF-7 human breast carcinoma cells. 125IVME2 rapidly enters MCF-7 cells and reaches a plateau in the presence of competing 10(-7) M 17 beta-estradiol. In the absence of competitor, uptake is substantially greater before reaching a plateau. Efflux of 125IVME2 from cells incubated in the absence of estradiol decreases to levels corresponding to specific binding. Under equilibrium conditions and in the absence of competitor, 125IVME2 binds to both specific and nonspecific sites but, in the presence of excess 17 beta-estradiol, the observed binding is nonspecific. 125IVME2 is cytotoxic to exponentially growing MCF-7 cells and produces a survival curve typical of those observed for [125I]iododeoxyuridine and 16 alpha-[125I]iodoestradiol.

Glutathione levels and chemosensitizing effects of buthionine sulfoximine in human malignant glioma cells

Biopsy samples and cultured cells derived from them were obtained from 39 patients with malignant glioma and were analyzed for 1) glutathione (GSH) content; 2) sensitivity to 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and/or nitrogen mustard (HN2) treatment and 3) the effect of buthionine sulfoximine (BSO) treatment on BCNU and/or HN2 cytotoxicity. The average GSH concentration of biopsy specimens was lower than those of cultured cells (2.36 +/- 0.44 vs. 11.42 +/- 2.32 nmol/10(6) cells). While some of the tumor specimens were sensitive to either BCNU or HN2, the majority were resistant to both. However, 8 of 23 tumors tested showed enhanced sensitivity to BCNU following treatment with BSO. Five of 17 tumors were similarly sensitized to HN2 by BSO. These results suggest that BSO chemosensitization may be of value for certain patients and that screening assays may help identify treatment-sensitive individuals.

Normal brain response after interstitial microwave hyperthermia

The effects of interstitial hyperthermia were assessed in the normal brain after a single 30 min treatment using 2450 MHz microwaves. A single helical coil microwave antenna was inserted into the frontal white matter and reference temperatures of 40, 41, 42, 43 and 44 degrees C maintained for 30 min along a temperature sensing probe 5 mm away and parallel to the antenna. The extent of hyperthermia damage was quantified weekly for 6 weeks using computed tomography (CT), and changes in regional cerebral blood flow (rCBF), tissue vascularity and mean transit time were determined using ultrafast CT. Qualitative histopathological analysis was carried out on tissues at various times after heating. Heat lesions were radiographically characterized by rapid development and resolution and consisted of an area of focal low density surrounded by a ring of contrast enhancement. Histologically, the focus of low density corresponded to regions of tissue necrosis, whereas the ring enhancement showed local reactive changes, including endothelial cell proliferation and infiltration with macrophages. Tissue necrosis occurred at temperatures greater than 43.9 +/- 1.5 degrees C (mean +/- standard deviation), and volumes of necrosis and ring enhancement were at a maximum 1 week following treatment. Relative to the contralateral, unheated hemisphere, rCBF in the heated brain appeared to be reduced for the first 3 weeks after treatment but approached normal by week 4. The mean transit time of blood was increased for weeks 1-3 compared to the untreated hemisphere, and tissue vascularity reached a maximum, 3 weeks after treatment. The rapid CT changes together with ultrafast CT and histopathological findings suggest that focal heat lesions in the brain stimulate a significant and rapid vascular response.

Low dose rate irradiation and halogenated pyrimidine effects on human cervical carcinoma cells

The response of two human cervical carcinoma cell lines to the combination of bromodeoxyuridine (BrdUrd) incorporation and low dose rate irradiation (LDRI) was assessed. Survival curves were generated following both acute (67.2 Gy/hr) and low dose rate (0.11-0.62 Gy/hr) 137Cs gamma-ray irradiation. The two cell lines exhibited markedly different radiation responses, but for the chronic irradiation, there was no significant difference in response between the low dose rates for either cell line. In all cases, the low dose rate radiation response could be described using a single exponential y = e-alpha D. The sensitizer enhancement ratio (SER) at 10% survival was determined and for the first cell line the low dose rate slope (alpha) was approximately 0.7 Gy-1 with an SER of 1.3-1.5 and an SER of approximately 1.6 for the acute response. In contrast, the second cell line had a low dose rate slope (alpha) of approximately 0.4 Gy-1, an SER of 1.3-1.5, and an SER of approximately 1.7 for the acute response. The similarity of the SER's is notable in light of the marked differences between the intrinsic radiation response of the cells. As the concentration and/or time of exposure to BrdUrd increased, both cytotoxicity and the degree of sensitization also increased. This study demonstrates that SER's with BrdUrd and LDRI are comparable to those obtained for acute exposures in two cervical carcinoma cell lines. The results suggest that this combination of modalities may have clinical applications.

A method for determination of iododeoxyuridine substitution of thymidine using reversed-phase high-performance liquid chromatography

An assay for thymidine substitution by iododeoxyuridine (IdUrd) using reversed-phase high-performance liquid chromatography (HPLC) has been developed. Three principal steps in this procedure are: extraction of DNA from cell or tissues, hydrolysis of DNA into deoxynucleosides and separation using HPLC. Approximately 1 microgram of DNA was recovered from 10(5) cells by phenol extraction, and subjected to hydrolysis into deoxynucleosides which required a three-stage DNA digestion using enzymes DNAse I. phosphodiesterase I and alkaline phosphatase. The deoxynucleosides were separated on the Microsorb C18 column with isocratic elution; 90-100% of the DNA was recovered as deoxynucleosides on the column. The method was used to determine quantitatively the percent IdUrd substitution of thymidine in Chinese hamster lung cells in vitro and BA1112 rhabdomyosarcoma in WAG/Rij rats perfused with IdUrd. It was possible to determine the thymidine substitution by IdUrd as small as 1% using a few micrograms of DNA. The close correspondence between the percent substitutions determined by HPLC and those determined by radioactive assay using [125I]-labelled IdUrd, confirmed the accuracy of our HPLC method. The HPLC analysis is especially suitable for the determination of percent IdUrd substitution of thymidine in tissue biopsies from animals used in in vivo experiments or humans undergoing radiation treatment.

Analysis of 5-iodo-2'-deoxyuridine incorporation in murine melanoma for photon activation therapy

Quantitative evaluation of the dose enhancement obtained with analog nucleoside agents such as iododeoxyuridine (IdUrd) requires knowledge of the degree to which the thymidine (Thd) in DNA is replaced by IdUrd. In the present investigation, mice were infused with IdUrd using an intravenous infusion apparatus capable of delivering continuous multi-day infusions without restraining the mice. The absolute incorporation of IdUrd in DNA was measured by 125IdUrd label, both in whole tissue and extracted DNA, showing a good correlation between levels observed in DNA and whole tissue. Replacement in a Harding-Passey murine melanoma tumor carried in BALB/c mice approached 10%. In addition, a Neutron Activation Analysis (NAA) technique was developed which showed in vitro, a sensitivity sufficient to evaluate the % replacement of Thd by IdUrd in small biological samples with a sensitivity greater than 0.1 ppm, at 1% replacement in mg samples. This method can provide information on iodine substitution in DNA in humans where the use of a radioactive DNA-seeking substance would be undesirable. Analyses of IdUrd incorporation in cultured cells by NAA and 125I counting showed good agreement.