Hypothermia-enhanced human tumor cell radiosensitivity

Combination of Electrochemotherapy with Radiotherapy: A Comprehensive, Systematic, PRISMA-Compliant Review of Efficacy and Potential Radiosensitizing Effects in Tumor Control

Radiotherapy (RT) and electrochemotherapy (ECT) are established local treatments for cancer. While effective, both therapies have limitations, especially in treating bulky and poorly oxygenated tumors. ECT has emerged as a promising palliative treatment, raising interest in exploring its combination with RT to enhance tumor response. However, the potential benefits and challenges of combining these treatments remain unclear. A systematic review was conducted following PRISMA guidelines. PubMed, Scopus, and Cochrane libraries were searched. Studies were screened and selected based on predefined inclusion and exclusion criteria. Ten studies were included, comprising in vitro and in vivo experiments. Different tumor types were treated with ECT alone or in combination with RT. ECT plus RT demonstrated superior tumor response compared to that under single therapies or other combinations, regardless of the cytotoxic agent and RT dose. However, no study demonstrated a clear superadditive effect in cell survival curves, suggesting inconclusive evidence of specific ECT-induced radiosensitization. Toxicity data were limited. In conclusion, the combination of ECT and RT consistently improved tumor response compared to that with individual therapies, supporting the potential benefit of their combination. However, evidence for a specific ECT-induced radiosensitization effect is currently lacking. Additional investigations are necessary to elucidate the potential benefits of this combination therapy.

The Value of Diffusion-Weighted Magnetic Resonance Imaging in Predicting the Efficacy of Radiation and Chemotherapy in Cervical Cancer

Background

To analyze the application value of apparent diffusion coefficient (ADC) and exponent apparent diffusion coefficient (EADC) in evaluating the efficacy of radiation and chemotherapy in cervical cancer using pre- and posttreatment diffusion-weighted magnetic resonance imaging (DW-MRI) scans.

Methods

52 patients with cervical cancer were administered radiation and chemotherapy. Both MRI and DW-MRI were obtained at different stages. The ADC and EADC values, as well as the maximum tumor diameter, were measured and analyzed.

Results

We found that the ADC value increased after treatment, and the EADC value decreased. Changes in the calculated ADC occurred earlier than the morphologic changes of the tumors. A negative correlation was detected between reduced rates in the maximum tumor diameter two months after treatment and pretreatment ADC value (r = –0.658, P < 0.05). An ROC curve and nonlinear regression analysis showed that the formula, y = (1525500.122x² – 4689.962x + 3.482) × 100%, can be used to calculate the percentage of complete remission after treatment according to the pretreatment ADC value.

Conclusion

Our data suggest that pretreatment ADC and EADC values are predictive of the efficacy of radiation and chemotherapy. Both ADC and EADC values during treatment were instrumental in early monitoring and dynamic observation.

Hypothermia after cranial irradiation protects neural progenitor cells in the subventricular zone but not in the hippocampus

PURPOSE

To explore if hypothermia can reduce the harmful effects of ionizing radiation on the neurogenic regions of the brain in young rats.

MATERIALS AND METHODS

Postnatal day 9 rats were randomized into two treatment groups, hypo- and normothermia, or a control group. Treatment groups were placed in chambers submerged in temperature-controlled water baths (30 °C and 36 °C) for 8 h, after receiving a single fraction of 8 Gy to the left hemisphere. Seven days' post-irradiation, we measured the sizes of the subventricular zone (SVZ) and the granule cell layer (GCL) of the hippocampus, and counted the number of proliferating (phospho-histone H3+) cells and microglia (Iba1 + cells).

RESULTS

Irradiation caused a 53% reduction in SVZ size in the normothermia group compared to controls, as well as a reduction of proliferating cell numbers by >50%. These effects were abrogated in the hypothermia group. Irradiation reduced the number of microglia in both treatment groups, but resulted in a lower cell density of Iba1 + cells in the SVZs of the hypothermia group. In the GCL, irradiation decreased both GCL size and the proliferating cell numbers, but with no difference between the treatment groups. The number of microglia in the GCL did not change.

CONCLUSIONS

Hypothermia immediately after irradiation protects the SVZ and its proliferative cell population but the GCL is not protected, one week post-irradiation.

Cryoablation Combined with Iodine-125 Implantation in the Treatment of Cardiac Metastasis from Alveolar Soft Part Sarcoma: A Case Report

Objectives

A 36-year-old Asian man was referred to our hospital with cardiac metastasis. He had a history of alveolar soft part sarcoma and initially underwent resection in 2005.

Methods

After exposing the tumor by thoracotomy, cryoablation was performed under ultrasound guidance. This treatment was combined with iodine-125 seed implantation to treat the cardiac metastasis.

Results

The patient had an uneventful recovery, and his cardiac function shows no obvious abnormalities. Imaging techniques suggest that cardiac metastasis was well controlled, and the patient is still alive 12 months after treatment.

Conclusions

Tumor cryoablation, combined with iodine seed implantations, may be regarded as a means of palliative treatment.

Issues Critical to the Successful Application of Cryosurgical Ablation of the Prostate

The techniques of present-day cryosurgery performed with multiprobe freezing apparatus and advanced imaging techniques yield predictable and encouraging results in the treatment of prostatic and renal cancers. Nevertheless, and not unique to cryosurgical treatment, the rates of persistent disease demonstrate the need for improvement in technique and emphasize the need for proper management of the therapeutic margin. The causes of persistent disease often relate to a range of factors including selection of patients, understanding of the extent of the tumor, limitations of the imaging techniques, and failure to freeze the tumor periphery in an efficacious manner. Of these diverse factors, the one most readily managed, but subject to therapeutic error, is the technique of freezing the tumor and appropriate margin to a lethal temperature [Baust, J. G., Gage, A. A. The Molecular Basis of Cryosurgery. BJU Int 95, 1187–1191 (2005)]. This article describes the recent experiments that examine the molecular basis of cryosurgery, clarifies the actions of the components of the freeze-thaw cycle, and defines the resultant effect on the cryogenic lesion from a clinical perspective. Further, this review addresses the important issue of management of the margin of the tumor through adjunctive therapy. Accordingly, a goal of this review is to identify the technical and future adjunctive therapeutic practices that should improve the efficacy of cryoablative techniques for the treatment of malignant lesions.

Progress toward Optimization of Cryosurgery

Cryosurgery for diverse neoplastic and non-neoplastic diseases has expanded in applicability in recent years, especially since intraoperative ultrasound became available as a method of monitoring the process of tissue freezing. However, persistence of disease after presumably adequate cryosurgical treatment has disclosed deficiencies in the technique, perhaps due to faulty application of the freeze-thaw cycles or due to shortcomings in the imaging method. Clearly cryosurgical technique is less than optimal. The optimal dosimetry for tissue freezing, the recent improvements in imaging techniques, and the need for adjunctive therapy are defined in this review, which assesses the progress toward improving the efficacy of cryosurgery.

Assessing pH and Oxygenation in Cryotherapy-induced Cytotoxicity and Tissue Response to Freezing

The microenvironmental pH and oxygenation is known to influence tumor cell response to heat, radiation, photodynamic and even chemotherapy. We have studied the previously untested influence of acidity and hypoxia on tumor and endothelial cell sensitivity to freezing. In addition, we have measured changes in oxygenation in vivo in murine FSaII fibrosarcomas after freeze injury. A low pH or low oxygenation environment was found to increase the sensitivity of tumor and endothelial cells to freezing at −20° C or −40° C in vitro. However, low pH and low oxygenation combined did not further increase cryosensitivity of the cells. In vivo, tumor oxygenation after freeze injury was studied immediately or 1–3 days after a standard freezing protocol was applied to FSaII tumors ranging from 250–500 mm3 grown in the rear-limb of C3H mice. Tumor oxygenation at the edge of the iceball was found to transiently increase 1–2 hours after freezing. At 1–3 days after freezing, a treatment that delayed FSaII tumor growth by approximately 1.5-fold, the mean tumor oxygenation was significantly increased by up to 2.5-fold from a control level of 5 mmHg partial pressure of oxygen (pO2), especially at the periphery of the tumor. We conclude that manipulation of pH or oxygenation has potential to increase the anti-tumor effects of minimally invasive cryosurgical techniques. Furthermore, the dynamic changes in oxygenation after freeze injury in vivo suggests value in combining cryotherapy with treatments dependent on oxygenation levels. Ultimately, these may be routes to more reliable treatment response with fewer recurrences.

Combination of cryosurgery and Iodine-125 seeds brachytherapy for lung cancer

It has been proven that radioactive seeds such as Iodine-125 seeds implantation is a highly effective treatment for patients with localized cancer, such as lung cancer. It may increase the effectiveness of cryosurgery for lung cancer with the combination of Iodine-125 seed implantation into edge of the cryoablation zone. Percutaneous cryosurgery and Iodine-125 seed implantation are mutual complementation; both have been proved to be safe and effective modality for unresectable lung cancer, especially for centrally located lung cancer. Well-designed, randomized and control study both in the laboratory and in the clinical about this option are needed before the conclusive evidence submits.

Percutaneous cryoablation for stage IV lung cancer: a retrospective analysis

The aim of this study was to investigate the therapeutic effect of cryoablation treatment and palliative treatment in stage IV lung cancer. Fifty-four patients were enrolled into the study. Thirty-one patients received cryoablation treatment (including intra- and extrapulmonary tumors), and 23 patients had palliative treatment (no cryoablation). Both the safety of the procedure and overall survival (OS) for stage IV lung cancer were assessed during a 6.5 year follow-up period. The OS of patients in both groups and the effects of treatment timing and frequency were compared. The OS in the cryoablation group was significantly longer than in the palliative group (median OS: 14 months vs. 7 months, P = 0.0009). The OS of those who received delayed cryoablation treatment was longer than that observed for those who received timely treatment (median OS: 18.5 months vs. 10 months, P = 0.0485), but this was not observed in those who received palliative treatment (median OS: 7 months vs. 7.5 months, P = 0.9814). Multiple treatments played an important role in improving the OS of patients who received cryoablation treatment (median OS: 18 months vs. 14 months, P = 0.0376). There was a significant difference between cryoablation and palliative treatment, in terms of OS. In addition, multiple cryoablation treatments may have an advantage over single treatments.

Experimental cryosurgery investigations in vivo

Cryosurgery is the use of freezing temperatures to elicit an ablative response in a targeted tissue. This review provides a global overview of experimentation in vivo which has been the basis of advancement of this widely applied therapeutic option. The cellular and tissue-related events that underlie the mechanisms of destruction, including direct cell injury (cryolysis), vascular stasis, apoptosis and necrosis, are described and are related to the optimal methods of technique of freezing to achieve efficacious therapy. In vivo experiments with major organs, including wound healing, the putative immunological response following thawing, and the use of cryoadjunctive strategies to enhance cancer cell sensitivity to freezing, are described.

The pathophysiology of thermoablation: optimizing cryoablation

PURPOSE OF REVIEW

To describe the response of prostate cancer to thermal therapies with an emphasis on cryoablative techniques.

RECENT FINDINGS

Long-term follow-up studies demonstrate clearly the effectiveness of the use of modern cryoablative techniques in the management of prostate cancer. Recently published American Urology Association Best Practice Guidelines identify prostate cryoablation as both primary and salvage therapies. Recent findings demonstrate the effectiveness of -40 degrees C exposure as lethal to prostate cancer genotypes following a double freeze-thaw encounter. In addition, the use of adjunctive agents to sensitize the cancer to freezing is reported.

SUMMARY

Thermal therapeutic options, especially cryoablation, are of growing interest for the treatment of prostatic and renal cancers. The methods of application of cryoablative therapy and the mechanisms of cell death that are attendant to the freezing-thaw encounter are clearly understood. Research focused on the development of freeze sensitizing agents that work adjunctively is of central interest in furthering the efficacy of this therapy.

Induction of hypothermic conditions associated with increased micronuclei formation in sigma-1 receptor knockout mice after administration of the antipsychotic compound E-5842

The antipsychotic sigma-1 (sigma(1)) receptor ligand E-5842 has been shown to increase micronucleated polychromatic erythrocyte (MNPCE) frequency in mouse bone marrow secondary to compound-induced hypothermia. Interaction with sigma(1) receptor has been considered a plausible contributing factor for E-5842-induced hypothermia, raising concern for a possible class effect of sigma receptor ligands in the mouse micronucleus (MN) test. We assessed the potential of E-5842 (200 mg/kg, oral) to produce hypothermic conditions associated with increased micronuclei formation in sigma(1) receptor knockout (sigma(1)R-KO) and wild type (WT) mice. After administration, animal's rectal temperature was recorded and peripheral blood and bone marrow samples were obtained (48 hr) and assessed for induction of micronucleated reticulocytes (MNRET) and MNPCE, respectively. E-5842 administration produced marked hypothermia both in sigma(1)R-KO and WT mice. Maximum decreases from preadministration temperature were 12.2 and 13.5 degrees C in sigma(1)R-KO and WT mice, respectively. Temperature returned to normal approximately 32 hr after administration. Bone marrow examination revealed a statistical significant increase (P < 0.05) in MNPCE frequency both in sigma(1)R-KO and WT animals. Examination of peripheral blood samples showed a slight, although nonstatistical significant, increase in MNRET frequency in sigma(1)R-KO mice. No similar effect was observed among WT animals. The results obtained after E-5842 administration to sigma(1)R-KO mice indicate that induction of hypothermic conditions associated with increased MNPCE formation is not mediated by compound interaction with sigma(1) receptor, ruling out concern for a possible class effect of similar high affinity sigma(1) receptor ligands in the mouse MN test.

Radiotherapy and wound healing

Radiotherapy is an invaluable weapon when treating cancer. However, the deleterious effects of radiation, both immediate and long-term, may have a significant effect on local tissues. Problematic wound healing in radiation-damaged tissue constitutes a major problem that is frequently overlooked during the management of patients who require radiotherapy, or have had radiotherapy in the past. Poor wound healing may lead to chronic ulceration, pain, secondary infection and psychological distress and compromise the outcome of general or reconstructive surgery. We discuss the pathophysiology of poor wound healing following radiotherapy, specific problems for radiation-damaged tissue and potential treatments to improve wound healing of irradiated tissues.

Cryosurgery--a putative approach to molecular-based optimization

Cryosurgery must be performed in a manner that produces a predictable response in an appropriate volume of tissue. In present-day clinical practice, that goal is not always achieved. Concerns with cryosurgical techniques in cancer therapy focus in part on the incidence of recurrent disease in the treated site, which is commonly approximately 20-40% in metastatic liver tumors, and prostate cancers. Whether the cause of this failure is disease-based or technique related, cryosurgery for cancer commonly needs the support of adjunctive therapy in the form of anti-cancer drugs or radiotherapy to increase the rate of cell death in the peripheral zone of the therapeutic lesion where cell survival is in balance for several days post-treatment. Recent evidence has identified a third mechanism of cell death associated with cryosurgery. This mechanism, apoptosis or gene regulated cell death, is additive with both the direct ice-related cell damage that occurs during the operative freeze-thaw intervals and coagulative necrosis that occurs over days post-treatment. In this manuscript we discuss, through a combination of literature review and new data, the combined roles of these distinct modes of cell death in a prostate and colorectal cancer. Data are presented suggesting that sub-freezing temperatures, when sequentially applied with low dose chemotherapy, may provide improved cancer cell death in the freeze zone periphery. Since the mechanism of action of most common chemotherapeutic agents is to initiate apoptosis in cancer cells, the observation that sub-freezing exposures yields a similar effect provides a possible route toward molecular-based procedural optimization to improve therapeutic outcome.

Induction of micronuclei in mouse bone-marrow erythrocytes in association with hypothermia after administration of the sigma receptor ligand E-5842

Oral administration of E-5842, a new sigma1 receptor ligand being developed as an antipsychotic drug, to male mice at single doses of 50, 100, 200 and 400 mg/kg produced marked and sustained decreases in rectal temperature. Both the intensity and the duration of the hypothermic effect increased with dose. Maximum decreases from the mean pre-administration temperature (36.2 degrees C) ranged from 7.5 to 12.9 degrees C for animals receiving 50 and 400 mg/kg doses, respectively. Examination of bone-marrow smears obtained 24, 48 and 72 h after administration revealed a slight but statistically significant (p < 0.05) increase in the frequency of micronucleated polychromatic erythrocytes (MNPCE) at the 48 h sampling for animals receiving the 200 mg/kg dose. These animals showed decreases from pre-administration temperature of approximately 12 degrees C, with recovery being observed 24 h after administration. When the hypothermic effect of E-5842 administration was avoided by housing treated animals under conditions of increased environmental temperature (30 degrees C) for 24 h, MNPCE frequency reverted to vehicle control values. Further, in E-5842-treated animals with an increased MNPCE frequency there was a shift in the distribution of the relative areas of micronuclei in MNPCE towards higher values. In addition, there was a statistically significant increase (p < 0.001) in the number of relatively large micronuclei (micronucleus diameter > or = 1/4 cytoplasm diameter) similar to that produced by administration of the mitotic spindle inhibitor colchicine (1 mg/kg), suggesting disturbance of mitotic apparatus as the possible underlying mechanism. The results suggest that the slight increase in MNPCE frequency observed 48 h after administration of a 200 mg/kg dose of E-5842 is due to a hypothermic effect and not to a direct effect of E-5842 on DNA.

Mechanisms of tissue injury in cryosurgery

As the modern era of cryosurgery began in the mid 1960s, the basic features of cryosurgical technique were established as rapid freezing, slow thawing, and repetition of the freeze-thaw cycle. Since then, new applications of cryosurgery have caused numerous investigations on the mechanism of injury in cryosurgery with the intent to better define appropriate or optimal temperature-time dosimetry of the freeze-thaw cycles. A diversity of opinion has become evident on some aspects of technique, but the basic tenets of cryosurgery remain unchanged. All the parts of the freeze-thaw cycle can cause tissue injury. The cooling rate should be as fast as possible, but it is not as critical as other factors. The coldest tissue temperature is the prime factor in cell death and this should be -50 degreesC in neoplastic tissue. The optimal duration of freezing is not known, but prolonged freezing increases tissue destruction. The thawing rate is a prime destructive factor and it should be as slow as possible. Repetition of the freeze-thaw cycle is well known to be an important factor in effective therapy. A prime need in cryosurgical research is related to the periphery of the cryosurgical lesion where some cells die and others live. Adjunctive therapy should influence the fate of cells in this region and increase the efficacy of cryosurgical techniques.