A trial of Ro 03-8799 (pimonidazole) in carcinoma of the uterine cervix: an interim report from the Medical Research Council Working Party on advanced carcinoma of the cervix

The Role of Imaging Biomarkers to Guide Pharmacological Interventions Targeting Tumor Hypoxia

Hypoxia is a common feature of solid tumors that contributes to angiogenesis, invasiveness, metastasis, altered metabolism and genomic instability. As hypoxia is a major actor in tumor progression and resistance to radiotherapy, chemotherapy and immunotherapy, multiple approaches have emerged to target tumor hypoxia. It includes among others pharmacological interventions designed to alleviate tumor hypoxia at the time of radiation therapy, prodrugs that are selectively activated in hypoxic cells or inhibitors of molecular targets involved in hypoxic cell survival (i.e., hypoxia inducible factors HIFs, PI3K/AKT/mTOR pathway, unfolded protein response). While numerous strategies were successful in pre-clinical models, their translation in the clinical practice has been disappointing so far. This therapeutic failure often results from the absence of appropriate stratification of patients that could benefit from targeted interventions. Companion diagnostics may help at different levels of the research and development, and in matching a patient to a specific intervention targeting hypoxia. In this review, we discuss the relative merits of the existing hypoxia biomarkers, their current status and the challenges for their future validation as companion diagnostics adapted to the nature of the intervention.

Impact of hypoxia on cervical cancer outcomes

The annual global incidence of cervical cancer is approximately 604 000 cases/342 000 deaths, making it the fourth most common cancer in women. Cervical cancer is a major healthcare problem in low and middle income countries where 85% of new cases and deaths occur. Secondary prevention measures have reduced incidence and mortality in developed countries over the past 30 years, but cervical cancer remains a major cause of cancer deaths in women. For women who present with Fédération Internationale de Gynécologie et d'Obstétrique (FIGO 2018) stages IB3 or upwards, chemoradiation is the established treatment. Despite high rates of local control, overall survival is less than 50%, largely due to distant relapse. Reducing the health burden of cervical cancer requires greater individualization of treatment, identifying those at risk of relapse and progression for modified or intensified treatment. Hypoxia is a well known feature of solid tumors and an established therapeutic target. Low tumorous oxygenation increases the risk of local invasion, metastasis and treatment failure. While meta-analyses show benefit, many individual trials targeting hypoxia failed in part due to not selecting patients most likely to benefit. This review summarizes the available hypoxia-targeted strategies and identifies further research and new treatment paradigms needed to improve patient outcomes. The applications and limitations of hypoxia biomarkers for treatment selection and response monitoring are discussed. Finally, areas of greatest unmet clinical need are identified to measure and target hypoxia and therefore improve cervical cancer outcomes.

Targeting Hypoxia: Revival of Old Remedies

Tumour hypoxia is significantly correlated with patient survival and treatment outcomes. At the molecular level, hypoxia is a major driving factor for tumour progression and aggressiveness. Despite the accumulative scientific and clinical efforts to target hypoxia, there is still a need to find specific treatments for tumour hypoxia. In this review, we discuss a variety of approaches to alter the low oxygen tumour microenvironment or hypoxia pathways including carbogen breathing, hyperthermia, hypoxia-activated prodrugs, tumour metabolism and hypoxia-inducible factor (HIF) inhibitors. The recent advances in technology and biological understanding reveal the importance of revisiting old therapeutic regimens and repurposing their uses clinically.

Therapeutic Modification of Hypoxia

Regions of reduced oxygenation (hypoxia) are a characteristic feature of virtually all animal and human solid tumours. Numerous preclinical studies, both in vitro and in vivo, have shown that decreasing oxygen concentration induces resistance to radiation. Importantly, hypoxia in human tumours is a negative indicator of radiotherapy outcome. Hypoxia also contributes to resistance to other cancer therapeutics, including immunotherapy, and increases malignant progression as well as cancer cell dissemination. Consequently, substantial effort has been made to detect hypoxia in human tumours and identify realistic approaches to overcome hypoxia and improve cancer therapy outcomes. Hypoxia-targeting strategies include improving oxygen availability, sensitising hypoxic cells to radiation, preferentially killing these cells, locating the hypoxic regions in tumours and increasing the radiation dose to those areas, or applying high energy transfer radiation, which is less affected by hypoxia. Despite numerous clinical studies with each of these hypoxia-modifying approaches, many of which improved both local tumour control and overall survival, hypoxic modification has not been established in routine clinical practice. Here we review the background and significance of hypoxia, how it can be imaged clinically and focus on the various hypoxia-modifying techniques that have undergone, or are currently in, clinical evaluation.

Efficacy and Safety Evaluation of the Various Therapeutic Options in Locally Advanced Cervix Cancer: A Systematic Review and Network Meta-Analysis of Randomized Clinical Trials

Treatment options in locally advanced cervix cancer (LACC) have evolved around radiation therapy (RT) and/or chemotherapy (CT), hypoxic cell sensitizers, immunomodulators (Imm), and locoregional moderate hyperthermia (HT). A systematic review and network meta-analysis was conducted to synthesize the evidence for efficacy and safety in terms of long-term locoregional control (LRC), overall survival (OS), and grade ≥3 acute morbidity (AM) and late morbidity (LM). Five databases were searched, and 6285 articles (1974-2018) were screened per the Preferred Reporting Items for Systematic Reviews and Meta-analysis guidelines. Fifty-nine randomized trials in untreated LACC without surgical intervention were shortlisted. These used 13 different interventions: RT alone and/or neoadjuvant CT (NACT), adjuvant CT (ACT), concurrent chemoradiation therapy (CTRT) (weekly cisplatin [CDDP]/3-weekly CDDP/combination CT with CDDP/non-CDDP-based CT), hypoxic cell sensitizers, Imm, or HT. Odds ratios (ORs) using random effects network meta-analysis were estimated. Interventions for each endpoint were ranked according to their corresponding surface under cumulative ranking curve values. Of the 9894 patients evaluated, the total events reported for LRC, OS, AM, and LM were 5431 of 8197, 4482 of 7958, 1710 of 7183, and 441 of 6333, respectively. ORs and 95% credible intervals (CrIs) for the 2 best strategies were HT + RT versus CTRT + ACT (OR, 1.23; 95% CrI, 0.49-3.19) for LRC, CTRT (3-weekly CDDP) versus HTCTRT (OR, 1.14; 95% CrI, 0.35-3.65) for OS, RT + ACT versus RT (OR, 0.01; 95% CrI, 0.00-1.04) for AM, and NACT + RT + ACT versus RT + Imm (OR, 0.42; 95% CrI, 0.02-7.39) for LM. The 3 interventions with the highest cumulative surface under cumulative ranking curve values for all 4 endpoints were HTRT, HTCTRT, and CTRT (3-weekly CDDP). Articles with low risk of bias and those published during 2004 to 2018 also retained these interventions as the best. Two-step cluster analysis grouped these 3 modalities in a single distinctive cluster. HTRT, HTCTRT, and CTRT with 3-weekly CDDP were identified as therapeutic modalities with the best comprehensive impact on key clinical endpoints in LACC. This warrants a phase 3 randomized trial among these strategies for a head-to-head comparison and additional validation.

Clinical trials targeting hypoxia

The concept of tumour hypoxia as a cause of radiation resistance has been prevalent for over 100 years. During this time, our understanding of tumour hypoxia has matured with the recognition that oxygen tension within a tumour is influenced by both diffusion and perfusion mechanisms. In parallel, clinical strategies to modify tumour hypoxia with the expectation that this will improve response to radiation have been developed and tested in clinical trials. Despite many disappointments, meta-analysis of the data on hypoxia modification confirms a significant impact on both tumour control and survival. Early trials evaluated hyperbaric oxygen followed by a generation of studies testing oxygen mimetics such as misonidazole, pimonidazole and etanidazole. One highly significant result stands out from the use of nimorazole in advanced laryngeal cancer with a significant advantage seen for locoregional control using this radiosensitiser. More recent studies have evaluated carbogen and nicotinamide targeting both diffusion related and perfusion related hypoxia. A significant survival advantage is seen in muscle invasive bladder cancer and also for locoregional control in hypopharygeal cancer associated with a low haemoglobin. New developments include the recognition that mitochondrial complex inhibitors reducing tumour oxygen consumption are potential radiosensitising agents and atovaquone is currently in clinical trials. One shortcoming of past hypoxia modifying trials is the failure to identify oxygenation status and select those patient with significant hypoxia. A range of biomarkers are now available including histological necrosis, immunohistochemical intrinsic markers such as CAIX and Glut 1 and hypoxia gene signatures which have been shown to predict outcome and will inform the next generation of hypoxia modifying clinical trials.

Nitroimidazoles as hypoxic cell radiosensitizers and hypoxia probes: misonidazole, myths and mistakes

Nitroimidazoles have been extensively explored as hypoxic cell radiosensitizers but have had limited clinical success, with efficacy restricted by toxicity. However, they have proven clinically useful as probes for tumour hypoxia. Both applications, and probably much of the dose-limiting toxicities, reflect the dominant chemical property of electron affinity or ease of reduction, associated with the nitro substituent in an aromatic structure. This single dominant property affords unusual, indeed extraordinary flexibility in drug or probe design, suggesting further development is possible in spite of earlier limitations, in particular building on the benefit of hindsight and an appreciation of errors made in earlier studies. The most notable errors were: the delay in viewing cellular thiol depletion as a likely common artefact in testing in vitro; slow recognition of pH-driven concentration gradients when compounds were weak acids and bases; and a failure to explore the possible involvement of pH and ascorbate in influencing hypoxia probe binding. The experience points to the need to involve a wider range of expertise than that historically involved in many laboratories when studying the effects of chemicals on radiation response or using diagnostic probes.

Cancer Radiosensitizers

Radiotherapy (RT) is a mainstay treatment for many types of cancer, although it is still a large challenge to enhance radiation damage to tumor tissue and reduce side effects to healthy tissue. Radiosensitizers are promising agents that enhance injury to tumor tissue by accelerating DNA damage and producing free radicals. Several strategies have been exploited to develop highly effective and low-toxicity radiosensitizers. In this review, we highlight recent progress on radiosensitizers, including small molecules, macromolecules, and nanomaterials. First, small molecules are reviewed based on free radicals, pseudosubstrates, and other mechanisms. Second, nanomaterials, such as nanometallic materials, especially gold-based materials that have flexible surface engineering and favorable kinetic properties, have emerged as promising radiosensitizers. Finally, emerging macromolecules have shown significant advantages in RT because these molecules can be combined with biological therapy as well as drug delivery. Further research on the mechanisms of radioresistance and multidisciplinary approaches will accelerate the development of radiosensitizers.

Clinical Advances of Hypoxia-Activated Prodrugs in Combination With Radiation Therapy

With the increasing incidence of cancer worldwide, the need for specific, effective therapies is ever more urgent. One example of targeted cancer therapeutics is hypoxia-activated prodrugs (HAPs), also known as bioreductive prodrugs. These prodrugs are inactive in cells with normal oxygen levels but in hypoxic cells (with low oxygen levels) undergo chemical reduction to the active compound. Hypoxia is a common feature of solid tumors and is associated with a more aggressive phenotype and resistance to all modes of therapy. Therefore, the combination of radiation therapy and bioreductive drugs presents an attractive opportunity for synergistic effects, because the HAP targets the radiation-resistant hypoxic cells. Hypoxia-activated prodrugs have typically been precursors of DNA-damaging agents, but a new generation of molecularly targeted HAPs is emerging. By targeting proteins associated with tumorigenesis and survival, these compounds may result in greater selectivity over healthy tissue. We review the clinical progress of HAPs as adjuncts to radiation therapy and conclude that the use of HAPs alongside radiation is vastly underexplored at the clinical level.

Tumor hypoxia and reoxygenation: the yin and yang for radiotherapy

Tumor hypoxia, a common feature occurring in nearly all human solid tumors is a major contributing factor for failures of anticancer therapies. Because ionizing radiation depends heavily on the presence of molecular oxygen to produce cytotoxic effect, the negative impact of tumor hypoxia had long been recognized. In this review, we will highlight some of the past attempts to overcome tumor hypoxia including hypoxic radiosensitizers and hypoxia-selective cytotoxin. Although they were (still are) a very clever idea, they lacked clinical efficacy largely because of ‘reoxygenation’ phenomenon occurring in the conventional low dose hyperfractionation radiotherapy prevented proper activation of these compounds. Recent meta-analysis and imaging studies do however indicate that there may be a significant clinical benefit in lowering the locoregional failures by using these compounds. Latest technological advancement in radiotherapy has allowed to deliver high doses of radiation conformally to the tumor volume. Although this technology has brought superb clinical responses for many types of cancer, recent modeling studies have predicted that tumor hypoxia is even more serious because ‘reoxygenation’ is low thereby leaving a large portion of hypoxic tumor cells behind. Wouldn’t it be then reasonable to combine hypoxic radiosensitizers and/or hypoxia-selective cytotoxin with the latest radiotherapy? We will provide some preclinical and clinical evidence to support this idea hoping to revamp an enthusiasm for hypoxic radiosensitizers or hypoxia-selective cytotoxins as an adjunct therapy for radiotherapy.

The impact of hypoxia and its modification of the outcome of radiotherapy

Since the initial observations made at the beginning of the last century, it has been established that solid tumors contain regions of low oxygenation (hypoxia). Tumor cells can survive in these hypoxic conditions and are a major factor in tumor radioresistance. This significance has resulted in hypoxia becoming the most cited biological topic in translational radiation oncology. Identifying hypoxic cells in human tumors has become paramount, and the ability to do this has been improved by the help of new imaging techniques and the use of predictive gene profiles. Substantial data confirm the presence of hypoxia in many types of human tumors, although with considerable heterogeneity among individual tumors. Various approaches have been investigated for eliminating the hypoxic population. These include increasing oxygen availability, directly radiosensitizing or killing the hypoxic cells, indirectly affecting them by targeting the tumor vascular supply, increasing the radiation dose to this resistant population, or by using radiation with a high linear energy transfer, for which hypoxia is believed to be less of an issue. Many of these approaches have undergone controlled clinical trials during the last 50 years, and the results have shown that hypoxic radiation resistance can indeed be overcome. Thus, ample data exists to support a high level of evidence for the benefit of hypoxic modification. However, such hypoxic modification still has no impact on general clinical practice. In this review we summarize the biological rationale, and the current activities and trials, related to identifying and overcoming hypoxia in modern radiotherapy.

Molecular Pathways: A Novel Approach to Targeting Hypoxia and Improving Radiotherapy Efficacy via Reduction in Oxygen Demand

Tumor hypoxia presents a unique therapeutic challenge in the treatment of solid malignancies. Its presence has been established to be a poor prognostic factor in multiple cancer types, and past hypoxia-directed approaches have yielded generally disappointing results. Previous approaches have centered on either increasing oxygen delivery or administering agents that preferentially radiosensitize or kill hypoxic cells. However, a novel and potentially more effective method may be to increase therapeutic benefit by decreasing tumor oxygen consumption via agents such as metformin or nelfinavir in a patient population that is enriched for tumor hypoxia. This promising approach is currently being investigated in clinical trials and the subject of this article.

Modulation of the tumor vasculature and oxygenation to improve therapy

The tumor microenvironment is increasingly recognized as a major factor influencing the success of therapeutic treatments and has become a key focus for cancer research. The progressive growth of a tumor results in an inability of normal tissue blood vessels to oxygenate and provide sufficient nutritional support to tumor cells. As a consequence the expanding neoplastic cell population initiates its own vascular network which is both structurally and functionally abnormal. This aberrant vasculature impacts all aspects of the tumor microenvironment including the cells, extracellular matrix, and extracellular molecules which together are essential for the initiation, progression and spread of tumor cells. The physical conditions that arise are imposing and manifold, and include elevated interstitial pressure, localized extracellular acidity, and regions of oxygen and nutrient deprivation. No less important are the functional consequences experienced by the tumor cells residing in such environments: adaptation to hypoxia, cell quiescence, modulation of transporters and critical signaling molecules, immune escape, and enhanced metastatic potential. Together these factors lead to therapeutic barriers that create a significant hindrance to the control of cancers by conventional anticancer therapies. However, the aberrant nature of the tumor microenvironments also offers unique therapeutic opportunities. Particularly interventions that seek to improve tumor physiology and alleviate tumor hypoxia will selectively impair the neoplastic cell populations residing in these environments. Ultimately, by combining such therapeutic strategies with conventional anticancer treatments it may be possible to bring cancer growth, invasion, and metastasis to a halt.

The clinical importance of assessing tumor hypoxia: relationship of tumor hypoxia to prognosis and therapeutic opportunities

Tumor hypoxia is a well-established biological phenomenon that affects the curability of solid tumors, regardless of treatment modality. Especially for head and neck cancer patients, tumor hypoxia is linked to poor patient outcomes. Given the biological problems associated with tumor hypoxia, the goal for clinicians has been to identify moderately to severely hypoxic tumors for differential treatment strategies. The "gold standard" for detecting and characterizing of tumor hypoxia are the invasive polarographic electrodes. Several less invasive hypoxia assessment techniques have also shown promise for hypoxia assessment. The widespread incorporation of hypoxia information in clinical tumor assessment is severely impeded by several factors, including regulatory hurdles and unclear correlation with potential treatment decisions. There is now an acute need for approved diagnostic technologies for determining the hypoxia status of cancer lesions, as it would enable clinical development of personalized, hypoxia-based therapies, which will ultimately improve outcomes. A number of different techniques for assessing tumor hypoxia have evolved to replace polarographic pO2 measurements for assessing tumor hypoxia. Several of these modalities, either individually or in combination with other imaging techniques, provide functional and physiological information of tumor hypoxia that can significantly improve the course of treatment. The assessment of tumor hypoxia will be valuable to radiation oncologists, surgeons, and biotechnology and pharmaceutical companies who are engaged in developing hypoxia-based therapies or treatment strategies.

AK-2123 (Sanazol) as a radiation sensitizer in the treatment of stage III cervical cancer: Results of an IAEA multicentre randomised trial

PURPOSE

AK-2123, a nitrotriazole hypoxic cell sensitizer, has reportedly improved results in head and neck cancers, uterine cervical cancers and other solid tumours when added to radical radiotherapy. A prospectively randomised trial was initiated by the International Atomic Energy Agency (IAEA) evaluating AK-2123 and radiotherapy in treatment of uterine cervical cancer stage III and IV.

PATIENTS AND METHODS

A total of 462 patients were randomised from 8 centres. Patients from four centres were excluded due to lack of accrual, closing of the centre and insufficient documentation and reporting. The final study population consisted of 333 patients who were randomised between May 1995 and December 1998. Patients were randomised to either standard radical treatment (radiation therapy alone, RT) or standard radical radiotherapy and additional administration of AK-2123 (RT+AK-2123). The total dose of 45-50.8 Gy was delivered by 20-28 fractions in an overall time of 4-5 1/2 weeks, with further dose escalation by brachytherapy or external beam. In the study arm, patients received 0.6 g/sqm AK-2123 by intravenous administration before external beam radiotherapy, treating with AK-2123 on alternate days (e.g. Monday-Wednesday-Friday) during the entire course of external beam therapy. Following exclusion of 7 patients who did not undergo treatment, a total of 326 patients remained for evaluation.

RESULTS

The rate of local tumour control was significantly higher in the group after radiotherapy and additional administration of AK-2123. Local tumour control was 61% (95/155) after AK-2123 and 46% (79/171) after radiotherapy alone (p=0.006). The actuarial survival at 60 months was 57% after RT+AK-2123, compared to 41% after RT (Log Rank p=0.01). AK-2123 did neither increase gastro-intestinal toxicity nor was it attributed to any haematological toxicity. A mild peripheral toxicity (Grade 1: 13% and Grade 2: 2%) usually completely reversible was infrequently seen after AK-2123 administration.

CONCLUSION

We conclude that the addition of AK-2123 to radical radiotherapy significantly increases local tumour control and survival in advanced squamous cell cancer of the uterine cervix without the addition of any major toxicity.

Local tumour control in women with carcinoma of the cervix treated with the addition of nitroimidazole agents to radiotherapy: a meta-analysis

The purpose of this paper was to estimate the effect of nitroimidazoles on the local control and overall survival of women receiving radiotherapy for carcinoma of the cervix. Sources searched included Medline, Cancerlit and national cancer organizations. Proceedings of meetings were hand-searched. Trial selection and quality score were performed in duplicate. Data extraction was performed by a single author. Five trials involving 849 patients were included. Median follow-up was typically 4 years or greater. The odds ratio (OR) for local recurrence did not demonstrate a significant effect (OR: 1.14; 95% confidence interval (CI): 0.78-1.66). The difference in mortality was also non-significant (OR: 1.26; 95% CI: 0.95-1.66). A significant increase in neuropathy was found (OR: 3.21; 95% CI: 1.36-7.55). Subgroup analysis did not reveal any sources of heterogeneity between trials. Despite five published randomized trials, evidence supporting the use of nitroimidazoles in the treatment of cervical cancer is lacking. Meta-analysis revealed no significant effect on local tumour control with a weak, non-significant trend suggesting a decrease in overall survival. There is, however, a significant increase in the rate of neurotoxicity with the use of these compounds. This overview can not support the use of these agents.

Clinical studies of hypoxia modification in radiotherapy

Hypoxic modification has been the subject of investigations in clinical radiation oncology since the early 60s. To date, this has not yet resulted in a treatment that has been widely accepted. Logistics and technical difficulties limit the routine use of hyperbaric oxygen in radiotherapy. The nitroimidazoles have not gained general acceptance, initially because of their toxicity and later because of doubts about the effectiveness of the newer generation of less toxic drugs. Nevertheless, there is good evidence from these studies that improving clinical outcome by hypoxic modulation is an achievable goal. Newer approaches including combinations of radiotherapy with tirapazamine, erythropoietin, and carbogen and nicotinamide (ARCON) are currently in phase III trial. For these new strategies to be successful, it is important that the proper patient categories are selected. Various methods to assess tumor oxygenation are now becoming available in the clinic. These potential predictive assays must be incorporated and validated in current and future large-scale clinical trials. Modifiers that target other aspects of tumor biology may also have indirect effects on tumor oxygenation. These aspects require further study in preclinical and early clinical settings.

A phase III randomized study of misonidazole plus radiation vs. radiation alone for cervix cancer

BACKGROUND AND PURPOSE

A randomized-controlled study of radical radiotherapy for cervical cancer with or without the hypoxic sensitizer, misonidazole was conducted from 1981 to 1984 to investigate its therapeutic benefit.

PATIENTS AND METHODS

Seventy-three patients were accrued from the Princess Margaret Hospital, and St John Regional Cancer Centre and randomized to either misonidazole (MISO, n = 39) or placebo (P, n = 34) in addition to radiotherapy. MISO was given orally each day 4 h prior to external beam radiation treatment (45Gy to midplane in 20 daily fractions) at a dose of 0.45 g/m(2), as well as during intra-uterine brachytherapy (40Gy).

RESULTS

The 10-year overall survival (OS) for the entire group was 46%, and the disease-free survival (DFS) was 39%. The 10-year OS for patients in the MISO arm was 45%, compared to 49% for the P arm (P = 0.89). The corresponding DFS figures were 36 and 43%, respectively, (P = 0.6). Ten patients (14%) developed severe late complications (grade 3 or 4). The 10-year serious late complication rate was 14% for MISO and 12% for P (P = 0.51).

CONCLUSIONS

Misonidazole failed to improve the outcome of patients with cervix cancer treated with radiotherapy.

Chemical radioprotection: a critical review of amifostine as a cytoprotector in radiotherapy

The use of chemical radioprotectors represents an obvious strategy to improve the therapeutic index in radiotherapy. Amofostine (WR-2721) has recently been approved for use in head and neck cancer to protect against radiation-induced xerostomia. Currently, the question has arisen whether amifostine could be used for radioprotection in broader terms. Amifostine may have the potential to enable intensified treatment by ameliorating mucosal reactions that are often a limiting factor in accelerated fractionation or concomitant chemoradiation. However, it has as yet not been clarified whether sufficient amifostine to reduce mucositis can be administered before each radiation fraction without causing unacceptable toxicity. Also, the optimal dosage and schedule of amifostine in chemoradiation combinations have not yet been established. The major concern related to radioprotectiors is the potential hazard of collateral tumor protection. A number of clinical studies have concluded that amifostine does not reduce antitumor efficacy. However, not even the largest study conducted, with over 300 patients, has sufficient statistical power to detect a clinically significant reduction in tumor control rate. To put this issue ultimately to a rest, a clinical trial with a sufficient accrual to definitely rule out a tumor protective effect of amifostine needs to be conducted. Substances reducing radiation-induced toxicity by modulating the biological response to radiation injury may represent an alternative concept in radioprotection. However, such agents are still at a developmental stage.

Effect of a hypoxic cell sensitizer doranidazole on the radiation-induced apoptosis of mouse L5178Y lymphoma cells

We investigated the sensitizing effect of the 2-nitroimidazole analogue doranidazole, a new hypoxic radiosensitizer, on radiation-induced apoptosis in L5178Y cells. Apoptosis was assessed by checking DNA ladder formation, the presence of sub-G1 peaks in flow cytometry, and chromatin condensation. A radiosensitizing effect of doranidazole was also confirmed by a soft-agar colony assay of surviving cells. In the assay of DNA ladder formation, DNA fragmentation was observed following irradiation under an aerobic or hypoxic condition with or without doranidazole. The proportions of the cells at the sub-G1 peak in a flow cytometric measurement was not very different among the irradiations at 5 Gy under the aerobic condition, 15 Gy under hypoxia, and 10 Gy with 1 mM doranidazole under hypoxia. The fraction of cells with chromatin condensation was found to be significantly increased with doranidazole up to 3 mM when applied under hypoxic irradiation, but did not increase even at 10 mM. The sensitizer enhancement ratio was estimated to be about 1.7 with a concentration of 1 mM. This enhancement ratio was not different from that observed by assaying cell survivals. On the other hand, doranidazole showed no radiosensitizing effect under aerobic conditions with 1 mM. In conclusion, the radiation-induced apoptosis of L5178Y cells was enhanced by doranidazole under hypoxia.

Phase Ia study of a hypoxic cell sensitizer doranidazole (PR-350) in combination with conventional radiotherapy

A phase Ia study of a 2-nitroimidazole nucleoside analog radiosensitizer doranidazole was conducted to evaluate its toxicity and pharmacokinetics in patients undergoing conventional external beam radiotherapy. Twenty-nine patients, aged 40-74 years, with a WHO performance status of 0-2 and with adequate organ functions, were entered in the study. Single administration of doranidazole was investigated first with 13 patients and then a course of five consecutive daily administrations was tested in 16 patients. Doranidazole was given i.v. 25 min before irradiation. Doranidazole doses of 400, 800, 1300 and 2000 mg/m2 were evaluated in the former study, and daily doses of 800, 1300 and 2000 mg/m2 were investigated in the latter study. All patients tolerated doranidazole administration. Although a transient decrease in the 24-h creatinine clearance rate was observed in five patients (one in the single administration study and four in the repeat administration study), this was not considered to be the dose-limiting toxicity. Other toxicities (hematological and gastrointestinal), which may not be related to doranidazole administration, were also mild and were not dose limiting. No neurotoxicity was observed. The average maximum concentration, area under the time-concentration curve and half-life of doranidazole in serum were 172-194 microg/ml, 502-582 microg x h/l and 4.2-4.6 h, respectively, at 2000 mg/m2. At the tested doses, administration of doranidazole was tolerable and achieved serum concentrations at which reasonable radiosensitization could be expected. A phase Ib/II study to evaluate the feasibility and efficacy of up to 30 repeat administrations seems to be warranted.

Has the outlook improved for amifostine as a clinical radioprotector?

Amifostine has recently been approved for clinical radiotherapy as a protector against irradiation-induced xerostomia. It is our aim to review the outlook for using amifostine as a general clinical radioprotector. Protection against X-rays is mainly obtained by the scavenging of free radicals. The degree of protection is therefore highly dependent on oxygen tension, with protection factors ranging from 1 to 3. Maximal protection is observed at physiological levels of oxygenation. A great variability in protection has also been observed between different normal tissues. Some tissue, like brain, is not protected while salivary glands and bone marrow may exhibit a three-fold increase in radiation tolerance. Amifostine is dephosphorylized to its active metabolite by a process involving alkaline phosphatase. Due to lower levels of alkaline phosphatase in tumor vessels, amifostine is marketed as a selective protector of normal tissue and not tumors. However, the preclinical investigations concerning the selectivity of amifostine are controversial and the clinical studies are sparse and do not have the power to evaluate the influence of amifostine on the therapeutic index.

CONCLUSION

based on the present knowledge amifostine should only be used in experimental protocols and not in routine practice.

Optical sensor-based oxygen tension measurements correspond with hypoxia marker binding in three human tumor xenograft lines

Hypoxia has a negative effect on the outcome of radiotherapy and surgery and is also related to an increased incidence of distant metastasis. In this study, tumor pO(2) measurements using a newly developed time-resolved luminescence-based optical sensor (OxyLitetrade mark) were compared with bioreductive hypoxia marker binding (pimonidazole). Single pO(2) measurements per tumor were compared to hypoxia marker binding in tissue sections using image analysis. Both assays were performed in the same tumors of three human tumor lines grown as xenografts. Both assays demonstrated statistically significant differences in the oxygenation status of the three tumor lines. There was also a good correlation between hypoxia marker binding and the pO(2) measurements with the OxyLitetrade mark device. A limitation of the OxyLitetrade mark system is that it is not yet suited for sampling multiple sites in one tumor. An important strength is that continuous measurements can be taken at the same position and dynamic information on the oxygenation status of tumors can be obtained. The high spatial resolution of the hypoxia marker binding method can complement the limitations of the OxyLitetrade mark system. In the future, a bioreductive hypoxic cell marker for global assessment of tumor hypoxia may be combined with analysis of temporal changes in pO(2) with the OxyLitetrade mark to study the effects of oxygenation-modifying treatment on an individual basis.

Radiosensitivity of human pancreatic cancer cells in vitro and in vivo, and the effect of a new hypoxic cell sensitizer, doranidazole

BACKGROUND AND PURPOSE

A clinical study of the new 2-nitroimidazole nucleoside analogue doranidazole (PR-350) in combination with intraoperative radiotherapy is ongoing in Japan for localized unresectable pancreatic cancer. However, few data have been reported on the radiosensitivity and hypoxic fraction of human pancreatic cancers, and the efficacy of doranidazole against them. This study was undertaken to address these issues.

MATERIALS AND METHODS

In vitro, four established human pancreatic cancer cell lines (SUIT-2, PANC-1, MIA PaCa-2 and BxPC-3) and murine SCCVII tumor cells (for comparison) were used. These cells were treated with 0.4 or 1 mM doranidazole for 45 mm prior to and during aerobic or hypoxic irradiation, and the cell survival was determined using the colony assay. In vivo, Balb/c nude mice bearing the pancreatic cancers (about 200 mg) on their backs received whole-body irradiation either after cervical dislocation, without physical restraint or anesthesia, or 20 min after intravenous injection of 100 mg/kg (0.4 mmol/kg) or 250 mg/kg (1 mmol/kg) of doranidazole. Following irradiation, the in vivo-in vitro assay was performed. The hypoxic fraction was estimated by the paired survival curve method.

RESULTS

Regarding in vitro radiosensitivity, there were no characteristics common to the four pancreatic cancer cell lines. In vitro, doranidazole had no sensitizing effect under aerobic conditions, but under hypoxic conditions, its sensitizer enhancement ratio (SER) was 1.25-1.3 at 0. 4 mM and 1.4-1.55 at 1 mM against the four pancreatic cancer cell lines. These SERs were similar to those obtained in SCCVII cells. In vivo, the hypoxic fraction was 20% (95% CI, 11-38%) in SUIT-2, 14% (6.5-28%) in PANC-1, 10% (5.9-16%) in MIA PaCa-2, and 27% (15-46%) in BxPC-3 tumors. The SER of doranidazole was 1.15-1.3 at the dose of 100 mg/kg and 1.35-1.45 at 250 mg/kg.

CONCLUSIONS

The four xenografted human pancreatic cancers had hypoxic fractions of 10-27% (mean: 18%). Doranidazole had definite in vitro and in vivo effects on all pancreatic cancer cell lines.

A survey on staging and treatment in uterine cervical carcinoma in the Radiotherapy Cooperative Group of the European Organization for Research and Treatment of Cancer

BACKGROUND

The treatment outcome of advanced stage uterine cervical carcinoma remains unsatisfactory. In order to elaborate a novel trial within The Radiotherapy Cooperative Group (RCG) of the European Organization for Research and Treatment of Cancer (EORTC), we conducted a survey in 1997-1998 to determine the variability of pre-treatment assessment and treatment options. The variability of choosing surgery, defined radiation therapy techniques and chemotherapy are investigated, as well as the center's choices of future treatment strategies.

METHODS

Fifty two of 81 RCG centers from the RCG have participated in the survey. As one would expect, there is a large variation in the techniques used for pretreatment evaluation and treatment options. There is no 'standard' for reporting acute and late side effects. Chemotherapy is used neither systematically nor uniformly, and some centers continue to use neadjuvant chemotherapy modalities.

RESULTS

Furthermore, the survey reveals that there is a strong demand for the reduction of overall treatment-time, for clinical investigation of novel combined modality treatment strategies, especially chemo-radiation therapy, and also for the use of new radiation sensitizers.

CONCLUSION

We conclude that a more homogeneous approach to the pretreatment evaluation as well as treatment techniques is required in order to allow adequate quality control in any future trial of the RCG in the EORTC.

Modification of the Radiation Response of Patients With Carcinoma of the Uterine Cervix

BACKGROUND: The purpose of this review is to summarize clinical trials for patients with cervical cancer treated with irradiation and modifiers of the irradiation response. METHODS: The MEDLINE database was used to identify clinical studies that evaluated modifiers of the irradiation response for patients with carcinoma of the uterine cervix from 1970 through 1998. The studies included were prospective, randomized phase III clinical trials comparing irradiation alone to irradiation plus a chemical modifier for carcinoma of the uterine cervix. RESULTS: Various chemical agents have been combined with irradiation in the treatment of patients with carcinoma of the uterine cervix. These agents include hyperbaric oxygen, hydroxyurea, nitroimidazoles, neoadjuvant chemotherapy, and concurrent chemotherapy. CONCLUSIONS: Many prospective, randomized studies evaluating the use of chemical agents to modify the irradiation response in patients with carcinoma of the uterine cervix indicate no improvement over radiation therapy alone. However, the February 1999 NCI clinical announcement describes a survival advantage for cisplatin-based therapy and concurrent irradiation.

Irradiation with or without misonidazole for patients with stages IIIB and IVA carcinoma of the cervix: final results of RTOG 80-05. Radiation Therapy Oncology Group

PURPOSE

The purpose of this study was to evaluate tumor response, progression-free survival, local tumor control, patterns of relapse, and toxicity in patients with Stages IIIb and IVa squamous cell carcinoma of the uterine cervix treated with irradiation or irradiation and misonidazole. This is a report of the final results of the study.

METHODS

This study was a prospective randomized Phase III trial performed by the Radiation Therapy Oncology Group (RTOG). Between August 1980 and November 1984, 120 patients with Stages IIIb and IVa squamous cell carcinoma of the cervix were randomized to receive either standard irradiation or standard irradiation and misonidazole. Irradiation consisted of 46 Gy to the pelvis plus a 10 Gy parametrial boost followed by intracavitary brachytherapy or external irradiation boost to the primary tumor. Misonidazole was administered at 400 mg/m2 daily, 2-4 h before irradiation. Patients in the 2 treatment groups were evenly distributed by stage, Karnofsky Performance Status, and positive para-aortic lymph nodes.

RESULTS

Sixty-one patients were treated with irradiation alone, and 59 patients received irradiation and misonidazole. Complete response in the pelvis occurred in 44 (75%) of those treated with irradiation and in 38 (64%) of those treated with irradiation and misonidazole. The progression-free survivals were 22% at 5 years for the control group, and 29% at 5 years for the misonidazole group. At the time of last follow-up, 18 patients in the control arm were free of disease, and in the experimental arm, 19 were free of disease. The patterns of failure for those treated with irradiation alone were local-only in 9 patients, distant-only in 8 patients, and local and distant in 11 patients. The patterns of failure for those receiving irradiation and misonidazole were local-only in 3 patients, distant-only in 8 patients, and local and distant in 8 patients. The maximum toxicity experienced per patient was grade 3 in 18%, grade 4 in 8%, and no grade 5 toxicity for those treated with irradiation alone compared to 8%, 2%, and 2%, respectively, for the experimental arm.

CONCLUSION

There were no statistically significant differences in pelvic response, disease-free survivals, patterns of failure, or toxicity for the irradiation alone group or for the irradiation and misonidazole group as administered in this study for patients with Stages IIIb and IVa squamous cell carcinoma of the uterine cervix.

[Radiation sensitizing agents for hypoxic cells: past, present and future]

Hypoxic cells are present in rodent and xenografted human tumours and it has been known for a long time that the absence of oxygen in tumours is a factor of resistance against ionising radiation. The dose modifying role of oxygen (oxygen enhancement ratio) has been largely studied in experimental models. For pO2 values of 2 mmHg, the relative radiosensitivity of tumour cells is intermediate between the maximum sensitivity observed in air and the minimal one observed in hypoxia. The measurement of tumour pO2 in patients (polarographic technique) has demonstrated the presence of low values (< 10 mmHg) in many different tumour sites (ENT, uterine cervix, breast, melanoma, etc). In order to sensitise hypoxic tumours, imidazole have been used in patients, but most of the results were negative. New methods have been developed in the combination of bioreductive drugs of cytotoxic cells to radiotherapy. In this article, we will describe the clinical results obtained in patients with radiosensitising chemical agents.

[Chemoradiotherapy in cancers of the uterine cervix]

Treatment of uterine cervix carcinomas is based on radiotherapy and surgery. Prognosis of advanced carcinoma leads to the proposal of many combinations. Only concurrent radio-chemotherapy demonstrated some interests. Combination of radiotherapy and radiosensitisers failed to demonstrate any advantage and in some instances was associated with an adverse effect. Hydroxyurea and mitomycin C alone or associated were extensively tested without benefit. From modern combinations and recent studies, we could conclude that only cisplatin (and probably its derivates) can be included in future trials.

Proliferation and hypoxia in human squamous cell carcinoma of the cervix: first report of combined immunohistochemical assays

PURPOSE

To characterize the distribution of hypoxia and proliferation in human squamous cell carcinoma of the cervix via an immunohistochemical approach prior to initiation of therapy.

METHODS AND MATERIALS

Patients with primary squamous cell carcinoma of the cervix uteri received a single infusion of the 2-nitroimidazole, pimonidazole (0.5 g/m2 i.v.), and 24 h later punch biopsies of the primary tumor were taken. Tissue was formalin fixed, paraffin embedded, and sectioned for immunohistochemistry. Hypoxia was detected by monoclonal antibody binding to adducts of reductively activated pimonidazole in malignant cells. Staining for endogenous MIB-1 and PCNA was detected in tumor cells via commercially available monoclonal antibodies. Point counting was used to quantitate the fraction of tumor cells immunostained for MIB-1, PCNA, and hypoxia marker binding.

RESULTS

Immunostaining for pimonidazole binding was distant from blood vessels. There was no staining in necrotic regions, and only minimal nonspecific staining, mostly in keratin. In general, cells immunostaining for MIB-1 and PCNA did not immunostain for pimonidazole binding. Cells immunostaining for MIB-1 and PCNA showed no obvious geographic predilection such as proximity to vasculature. Quantitative comparison showed an inverse relationship between hypoxia marker binding and proliferation.

CONCLUSIONS

Immunohistochemical staining for pimonidazole binding is consistent with the presence of hypoxic cells in human tumors and may be useful for estimating tumor hypoxia prior to radiation therapy. Immunostaining for pimonidazole binding is an ideal complement to immunohistochemical assays for endogenous proliferation markers allowing for comparisons of tumor hypoxia with other physiological parameters. These parameters might be used to select patients for radiation protocols specifically designed to offset the negative impact of hypoxia and/or proliferation on therapy. The inverse relationship between pimonidazole binding and proliferation markers is a preliminary result requiring verification.

Remote controlled prolonged conscious sedation for gynaecological radiotherapy

Conscious sedation with subanaesthetic doses of propofol is an effective technique for the management of highly anxious patients in dentistry. Prolonged administration of propofol to achieve conscious sedation in spontaneously breathing patients without an airway adjunct has not been reported previously. We describe the management of target-controlled conscious sedation with propofol for 21 h in a patient undergoing gynaecological radiotherapy.