A phase I study of etanidazole and radiotherapy in malignant glioma

Stereotactic radiosurgery of radioresistant glioblastomas. The ways of overcoming radioresistance of hypoxic tumors

Background. Taking into account high degree of resistance of glioblastoma to radiation therapy, and also low overall survival rates of patients, it is necessary to develop improved methods of treating this pathology, in particular, complex combined treatment with radiation therapy and radiosensitizers. Purpose – to assess the effectiveness of radiosensitization of hypoxic tumors in radiosurgical treatment of glioblastomas; to increase non-recurrent and overall survival rate of patients. Materials and methods. Stereotactic radiosurgery (SRS) of glioblastoma was performed in 106 patients (average age – 53 years), 66 males (62,26%) and 40 females (37,73%). The average dose was 18 Gy in a single-fraction SRS, and 32 Gy (7 Gy per fraction) in multi-fraction SRS. The average volume tumor was 29 cm3 . The treatment group consisted of 66 patients who underwent SRS with radiosensitization. 40 patients made up the control group and underwent SRS without radiosensitization. Results. Median overall survival (MOS) was 20 months in the group with radiosensitization, whereas in the control group it was 12 months. 10-month recurrence-free period after radiosurgery was observed in 95,4% of the patients of the group with radiosensitization and in 70,6% of the patients of the control group. MOS after SRS was similar between the patients with wild-type IDH tumors and patients with tumors with IDH mutation (10,0 months and 11,0 months respectively), and also between the patients with MGMT-methylated tumors and patients with MGMT-nonmethylated tumors (11,2 and 10,2 months respectively). Among all the treated patients, in 20 of them (16,6%) side radiation effects after SRS were observed, and in 9 patients (7,5%) radiation necrosis developed in 3 to 16 months after SRS. The signs of moderate toxicity in the form of vomiting were observed in 6,6% of the patients of the subgroup with metronidazole. There were no signs of toxicity in the subgroup with nimorazole. Conclusions. Radiosensitization improves rates of overall survival by 53,3% and recurrence-free survival by 24,8 % in performing SRS of hypoxic radioresistant glioblastomas. Nimorazole and metronidazole are powerful radiosensitizers which increase radiosensitivity of tumor cells through enhancing oxygen saturation of hypoxic cells. In order to determine indications for performing SRS with radiosensitization and periods for performing an SRS session we must take into consideration the result of an oxygen test (level of oxygen saturation of the tumor), the peak of signal intensity in the zone of active tumor growth and the peak of saturation of the whole tumor volume.

The use of radiosensitizing agents in the therapy of glioblastoma multiforme-a comprehensive review

BACKGROUND

Glioblastoma is the most common malignant brain tumor in human adults. Despite several improvements in resective as well as adjuvant therapy over the last decades, its overall prognosis remains poor. As a means of improving patient outcome, the possibility of enhancing radiation response by using radiosensitizing agents has been tested in an array of studies.

METHODS

A comprehensive review of clinical trials involving radiation therapy in combination with radiosensitizing agents on patients diagnosed with glioblastoma was performed in the National Center for Biotechnology Information's PubMed database.

RESULTS

A total of 96 papers addressing this matter were published between 1976 and 2021, of which 63 matched the subject of this paper. All papers were reviewed, and their findings discussed in the context of their underlining mechanisms of radiosensitization.

CONCLUSION

In the history of glioblastoma treatment, several approaches of optimizing radiation-effectiveness using radiosensitizers have been made. Even though several different strategies and agents have been explored, clear evidence of improved patient outcome is still missing. Tissue-selectiveness and penetration of the blood-brain barrier seem to be major roadblocks; nevertheless, modern strategies try to circumvent these obstacles, using novel sensitizers based on preclinical data or alternative ways of delivery.

Advances in radiotherapy of brain tumors: radiobiology versus reality

Radiotherapy still remains the most effective adjunctive therapy for malignant gliomas following surgery and provides useful local control for some benign tumors. Research efforts have been directed towards several aspects of the radiation therapy of tumors. The results of clinical trials undertaken in the last decade offer some basis for optimism in the management of patients with malignant brain tumors, although cure is still not a realistic objective. This review focuses on the rationale and radiobiological basis for recent developments in the radiotherapy of adult brain tumors. The salient issues are discussed from a neurosurgeon's perspective.

Stereotactic Radiosurgery: Adjacent Tissue Injury and Response after High-Dose Single Fraction Radiation—Part II: Strategies for Therapeutic Enhancement, Brain Injury Mitigation, and Brain Injury Repair

IN THE FIRST part of this series, we reviewed the histological, radiographic, and molecular data gathered regarding the brain parenchymal response to radiosurgery and suggested future studies that could enhance our understanding of the topic. With this article, we begin by addressing methods of potentiating the effect of radiosurgery on target lesions of the central nervous system. Much of the work on potentiating the effects of cranial radiation has been performed in the field of whole-brain radiotherapy. Data from Phase III trials evaluating the efficacy of various agents as radiosensitizers or radioenhancers in whole-brain radiotherapy are reviewed, and trials for investigating certain agents as enhancers of radiosurgery are suggested. The roles of gene therapy and nanotechnology in enhancing the therapeutic efficacy of radiosurgery are then addressed. Focus is then shifted to a discussion of strategies of protecting healthy tissue from the potentially deleterious aspects of the brain's response to radiosurgery that were presented in the first article of this series. Finally, comments are made regarding the role of neural progenitor or stem cells in the repair of radiation-induced brain injury after radiosurgery. The importance of both the role of the extracellular matrix and properly directed axonal regrowth leading to appropriate target reinnervation is highlighted.

In vitro activity of Etanidazole against the protozoan parasite Trypanosoma cruzi

We investigated the in vitro action of an hydrosoluble 2-nitroimidazole, Etanidazole (EZL), against Trypanosoma cruzi, the etiologic agent of Chagas disease. EZL displayed lethal activity against isolated trypomastigotes as well as amastigotes of T. cruzi (RA strain) growing in Vero cells or J774 macrophages, without affecting host cell viability. Although not completely equivalent to Benznidazole (BZL), the reference drug for Chagas chemotherapy, EZL takes advantage in exerting its anti-T. cruzi activity for longer periods without serious toxic side effects, as those recorded in BZL-treated patients. Our present results encourage further experiments to study in depth the trypanocidal properties of this drug already licensed for use in human cancers.

A phase I trial of etanidazole and hyperfractionated radiotherapy in children with diffuse brainstem glioma

PURPOSE

To determine the toxicity and maximum tolerated dose of etanidazole administered concurrently with hyperfractionated radiation therapy (HRT) for children with brainstem glioma.

METHODS AND MATERIALS

Eighteen patients with brainstem glioma were treated with etanidazole and HRT on a dose escalation protocol (Phase I trial) between 1990 and 1996. All patients had MRI confirmation of diffuse pontine glioma and signs/symptoms of cranial nerve deficit, ataxia, or long tract signs of <6 months' duration. Cervicomedullary tumors were excluded. Patients (median age: 8.5 years; 11 males, 7 females) received HRT to the tumor volume plus a 2-cm margin with parallel-opposed 6-15-MV photons. The total dose was 66 Gy in 44 fractions (1.5 Gy b.i.d., with at least 6 h between fractions) for the first 3 patients and 63 Gy in 42 fractions for the subsequent 15 patients. Etanidazole was administered as a rapid i.v. infusion 30 min before the morning fraction of HRT. Planned doses of etanidazole were 1.8 g/m(2) x 17 doses (30.6 g/m(2)) at Step 1 to a maximum of 2.4 g/m(2) x 21 doses (50.4 g/m(2)) at Step 8. Dose escalation was planned with 3 patients at each of the 8 levels.

RESULTS

Three patients were treated at each dose level except Level 2, on which only 1 patient was treated. The highest dose level achieved was Level 7, which delivered a total etanidazole dose of 46.2 g/m(2). Two patients were treated at this level, and both patients experienced Grade 3 toxicity in the form of a diffuse cutaneous rash. Three patients received a lower dose of 42 g/m(2) (dose Level 6) without significant toxicity, and this represents the maximum tolerated dose (MTD). There were 23 cases of Grade 1 toxicity (10 vomiting, 5 peripheral neuropathy, 2 rash, 2 constipation, 1 weight loss, 3 others), 11 cases of Grade 2 toxicity (4 vomiting, 2 skin erythema, 2 constipation, 1 arthralgia, 1 urinary retention, 1 hematologic), and 4 Grade 3 toxicities (2 rash, 1 vomiting, 1 skin desquamation). Grade 2 or 3 peripheral neuropathy was not seen at any dose level. The median survival from the start of treatment was 8.5 months (range: 3-58 months).

CONCLUSION

The MTD of etanidazole in children receiving HRT for brainstem glioma is 42 g/m(2), with cutaneous rash as the dose-limiting toxicity. This is in contrast to the adult experience, which demonstrates a 24% lower MTD of 34 g/m(2) limited by peripheral neuropathy.

Simulation of intratumoral release of Etanidazole: effects of the size of surgical opening

The efficacy of radiotherapy can be enhanced by the delivery of radiosensitizer (Etanidazole) to brain tumor from biodegradable polymer implants. This process is investigated by simulation carried out at a cut section of tumor with polymeric wafers of Etanidazole loading implanted in the resected cavity. The coupled mass and momentum equations are solved to obtain the transient solution of the drug distribution in the tumor. The polymeric delivery shows high therapeutic index, indicating the wafers' success in delivering more drugs to the tumor rather than to the tissue. The penetration distance of Etanidazole was found to decrease from 14 mm (at 5th/40th day after implantation) to 6.5 mm (at 30th/75th day), suggesting an initial high burst of drug release which cause nearby tissue toxicity and a low effective drug delivery towards the later stages. The short penetration depth is due to Etanidazole having low interstitial Peclet number and high elimination/diffusion modulus. Edema causes the interstitial pressure, velocity, and concentration to increase in all domains, and leads to enhanced convection and a lowering of therapeutic index. Simulations on the open tumor geometry show significantly lower efficacy of the drug delivery due to the uneven distribution of drug in the tumor zone.

Novel radiation technologies for malignant gliomas

Despite the advent of new technologies available for the imaging of brain tumors and the evolution of methods to deliver more focused radiation therapy, most malignant gliomas recur locally. Therapies aimed at increasing local control of gliomas will set the stage for improved survival in a disease with a dismal overall prognosis. This review focuses on several radiotherapeutic approaches to dose escalation that may help improve local control.

A phase I study of a hypoxic cell sensitizer KU-2285 in combination with conventional radiotherapy

A fluorinated 2-nitroimidazole radiosensitizer KU-2285 was given orally to 14 patients. The daily dose ranged from 0.5 to 2.0 g and the total dose given ranged from 0.8 to 28 g/m2. Possible toxicities observed were vomiting in two patients, muscle cramping in one and multiple joint pain in one. All these complications were mild and transient and no other toxicity was observed. The peak serum concentration of KU-2285 was 25-30 micrograms/ml at the dose of 1 g/m2. The cumulative toxicity of KU-2285 appears to be relatively low and further clinical trials seem to be warranted.