Interstitial laser hyperthermia for colorectal liver metastases: the effect of thermal sensitization and the use of a cylindrical diffuser tip on tumor necrosis

Local Treatments in the Unresectable Patient with Colorectal Cancer Metastasis: A Review from the Point of View of the Medical Oncologist

For patients with isolated liver metastases from colorectal cancer who are not candidates for potentially curative resections, non-surgical local treatments may be useful. Non-surgical local treatments are classified according to how the treatment is administered. Local treatments are applied directly on hepatic parenchyma, such as radiofrequency, microwave hyperthermia and cryotherapy. Locoregional therapies are delivered through the hepatic artery, such as chemoinfusion, chemoembolization or selective internal radiation with Yttrium 90 radioembolization. The purpose of this review is to describe the different interventional therapies that are available for these patients in routine clinical practice, the most important clinical trials that have tried to demonstrate the effectiveness of each therapy and recommendations from principal medical oncologic societies.

[Indications and limits of ablative therapies in prostate cancer]

OBJECTIVE

To perform a state of the art about indications and limits of ablative therapies for localized prostate cancer.

METHODS

A review of the scientific literature was performed in Medline database (http://www.ncbi.nlm.nih.gov) and Embase (http://www.embase.com) using different associations of keywords. Publications obtained were selected based on methodology, language and relevance. After selection, 107 articles were analysed.

RESULTS

The objective to combine reduction of side effects and oncological control has induced recent development of several ablative therapies. Beyond this heterogeneity, some preferential indications appear: unilateral cancer of low risk (but with significant volume, excluding active surveillance) or intermediate risk (excluding majority of grade 4); treatment targeted the index lesion, by quarter or hemi-ablation, based on biopsy and mpMRI. In addition, indications must considered specific limits of each energy, such as gland volume and tumor localization.

CONCLUSION

Based on new imaging and biopsy, ablative therapies will probably increased its role in the future in management of localize prostate cancer. The multiple ongoing trials will certainly be helpful to better define their indications and limits.

Laser Ablation for Cancer: Past, Present and Future

Laser ablation (LA) is gaining acceptance for the treatment of tumors as an alternative to surgical resection. This paper reviews the use of lasers for ablative and surgical applications. Also reviewed are solutions aimed at improving LA outcomes: hyperthermal treatment planning tools and thermometric techniques during LA, used to guide the surgeon in the choice and adjustment of the optimal laser settings, and the potential use of nanoparticles to allow biologic selectivity of ablative treatments. Promising technical solutions and a better knowledge of laser-tissue interaction should allow LA to be used in a safe and effective manner as a cancer treatment.

Recent advances of thermally responsive nanogels for cancer therapy

Thermally responsive nanogel drug delivery systems (TRNDDS) have been widely investigated as a new strategy for active targeting tumor therapy, as these can accumulate on the tumor site and/or release the payload at the desired site by structure changes rapidly once stimulated by temperature changes. In this review, we discuss the evolution of TRNDDS and future perspectives for antitumor drug and gene delivery. With further understanding of the specificity of tumor site at the cellular and molecular level, in parallel with the development of nanomaterial design and preparation, TRNDDS show great potential for tumor targeting therapy.

Assessment of the effect of laser irradiations at different wavelengths (660, 810, 980, and 1064 nm) on autophagy in a rat model of mucositis

It is known that high-dose radiation has an effect on tissue healing, but tissue healing does not occur when low dose radiation is applied. To clarify this issue, we compare the treatment success of low dose radiation with programmed cell death mechanisms on wounded tissue. In this study, we aimed to investigate the interactions of low and high-dose radiation using an autophagic mechanism. We included 35 adult Wistar-Albino rats in this study. All animals were injected with 100 mg/kg of 5-fluorouracil (5-FU) on the first day and 65 mg/kg of 5-FU on the third day. The tips of 18-gauge needles were used to develop a superficial scratching on the left cheek pouch mucosa by dragging in a linear movement on third and fifth days. After mucositis formation was clinically detected, animals were divided into five groups (n = 7). Different wavelengths of laser irradiations (1064 nm, Fidelis Plus, Fotona, Slovenia; 980 nm, FOX laser, A.R.C., Germany; 810 nm, Fotona XD, Fotona, Slovenia; 660 nm, HELBO, Medizintechnik GmbH, Wels, Austria) were performed on four groups once daily for 4 days. The laser irradiation was not performed on the control group. To get the tissue from the left cheek at the end of fourth day from all animals, oval excisional biopsy was performed. Molecular analysis assessments of pathological and normal tissue taken were performed. For this purpose, the expression analysis of autophagy genes was performed. The results were evaluated by normalization and statistics analysis. We found that Ulk1, Beclin1, and Atg5 expression levels were increased in the rats when the Nd:YAG laser was applied. This increase showed that a 1064-nm laser is needed to activate the autophagic mechanism. However, in the diode applications, we found that Beclin1, Atg10, Atg5, and Atg7 expressions numerically decreased. Atg5 is responsible for the elongation of autophagosome. Becn1 is a control gene in the control mechanism of autophagy. The reduction of the expression of these genes leads us to think that it may depend on the effect of drug (5-FU) used to form model. Expressions of therapeutic genes increase to ensure hemostasis, but in our study, expressions were found to decrease. More detailed studies are needed.

Thermal ablation of liver metastases from colorectal cancer: radiofrequency, microwave and laser ablation therapies

Surgery is currently considered the treatment of choice for patients with colorectal cancer liver metastases (CRLM) when resectable. The majority of these patients can also benefit from systemic chemotherapy. Recently, local or regional therapies such as thermal ablations have been used with acceptable outcomes. We searched the medical literature to identify studies and reviews relevant to radiofrequency (RF) ablation, microwave (MW) ablation and laser-induced thermotherapy (LITT) in terms of local progression, survival indexes and major complications in patients with CRLM. Reviewed literature showed a local progression rate between 2.8 and 29.7 % of RF-ablated liver lesions at 12-49 months follow-up, 2.7-12.5 % of MW ablated lesions at 5-19 months follow-up and 5.2 % of lesions treated with LITT at 6-month follow-up. Major complications were observed in 4-33 % of patients treated with RF ablation, 0-19 % of patients treated with MW ablation and 0.1-3.5 % of lesions treated with LITT. Although not significantly different, the mean of 1-, 3- and 5-year survival rates for RF-, MW- and laser ablated lesions was (92.6, 44.7, 31.1 %), (79, 38.6, 21 %) and (94.2, 61.5, 29.2 %), respectively. The median survival in these methods was 33.2, 29.5 and 33.7 months, respectively. Thermal ablation may be an appropriate alternative in patients with CRLM who have inoperable liver lesions or have operable lesions as an adjunct to resection. However, further competitive evaluation should clarify the efficacy and priority of these therapies in patients with colorectal cancer liver metastases.

Magnetic fluid hyperthermia inhibits the growth of breast carcinoma and downregulates vascular endothelial growth factor expression

The application of magnetic fluid hyperthermia (MFH) with nanoparticles has been shown to inhibit tumor growth in several animal models. However, the feasibility of using MFH in vivo to treat breast cancer is uncertain, and the mechanism is unclear. In the present study, it was observed that the intratumoral administration of MFH induced hyperthermia significantly in rats with Walker-265 breast carcinomas. The hyperthermia treatment with magnetic nanoparticles inhibited tumor growth in vivo and promoted the survival of the tumor-bearing rats. Furthermore, it was found that MFH treatment downregulated the protein expression of vascular endothelial growth factor (VEGF) in the tumor tissue, as observed by immunohistochemistry. MFH treatment also decreased the gene expression of VEGF and its receptors, VEGF receptor 1 and 2, and inhibited angiogenesis in the tumor tissues. Taken together, these results indicate that the application of MFH with nanoparticles is feasible for the treatment of breast carcinoma. The MFH-induced downregulation of angiogenesis may also contribute to the induction of an anti-tumor effect.

Research perspectives: gold nanoparticles in cancer theranostics

High recurrence rates after surgical resection remain a formidable challenge in many cancers. Although chemo- and/or radiotherapy are often applied following surgery to prevent tumor relapse, these treatments are generally accompanied by serious side effects and challenges in their delivery that limit their effectiveness. Gold nanoparticles (AuNPs), which possess unique physicochemical properties, have the potential to enhance the efficacy of these conventional treatment modalities. In this review, we briefly describe the current state of AuNP research in the area of cancer theranostics. Recent studies have investigated AuNPs' use as photothermal converters, drug carriers, radiosensitizers, and imaging probes in a wide range of applications for cancer diagnosis and therapy. AuNPs have promise in minimally invasive thermal ablation therapy, diagnostic imaging, intraoperative tumor margin delineation, and multimodal anticancer therapy. The successful translation of AuNPs into the clinic will have significant impact on the care of cancer patients using image-guided, minimally invasive approaches.

Effective photothermal chemotherapy using doxorubicin-loaded gold nanospheres that target EphB4 receptors in tumors

Photothermal ablation (PTA) is an emerging technique that uses near-infrared (NIR) laser light-generated heat to destroy tumor cells. However, complete tumor eradication by PTA therapy alone is difficult because heterogeneous heat distribution can lead to sublethal thermal dose in some areas of the tumor. Successful PTA therapy requires selective delivery of photothermal conducting nanoparticles to mediate effective PTA of tumor cells, and the ability to combine PTA with other therapy modalities. Here, we synthesized multifunctional doxorubicin (DOX)-loaded hollow gold nanospheres (DOX@HAuNS) that target EphB4, a member of the Eph family of receptor tyrosine kinases overexpressed on the cell membrane of multiple tumors and angiogenic blood vessels. Increased uptake of targeted nanoparticles T-DOX@HAuNS was observed in three EphB4-positive tumors both in vitro and in vivo. In vivo release of DOX from DOX@HAuNS, triggered by NIR laser, was confirmed by dual-radiotracer technique. Treatment with T-DOX@HAuNS followed by NIR laser irradiation resulted in significantly decreased tumor growth when compared with treatments with nontargeted DOX@HAuNS plus laser or HAuNS plus laser. The tumors in 6 of the 8 mice treated with T-DOX@HAuNS plus laser regressed completely with only residual scar tissue by 22 days following injection, and none of the treatment groups experienced a loss in body weight. Together, our findings show that concerted chemo-photothermal therapy with a single nanodevice capable of mediating simultaneous PTA and local drug release may have promise as a new anticancer therapy.

Focal laser ablation of prostate cancer: definition, needs, and future

Current challenges and innovations in prostate cancer management concern the development of focal therapies that allow the treatment of only the cancer areas sparing the rest of the gland to minimize the potential morbidity. Among these techniques, focal laser ablation (FLA) appears as a potential candidate to reach the goal of focusing energy delivery on the identified targets. The aim of this study is to perform an up-to-date review of this new therapeutic modality. Relevant literature was identified using MEDLINE database with no language restrictions (entries: focal therapy, laser interstitial thermotherapy, prostate cancer, FLA) and by cross-referencing from previously identified studies. Precision, real-time monitoring, MRI compatibility, and low cost of integrated system are principal advantages of FLA. Feasibility and safety of this technique have been reported in phase I assays. FLA might eventually prove to be a middle ground between active surveillance and radical treatment. In conclusion, FLA may have found a role in the management of prostate cancer. However, further trials are required to demonstrate the oncologic effectiveness in the long term.

Laser ablation for small hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide and is increasingly detected at small size (<5 cm) owing to surveillance programmes in high-risk patients. For these cases, curative therapies such as resection, liver transplantation, or percutaneous ablation have been proposed. When surgical options are precluded, image-guided tumor ablation is recommended as the most appropriate therapeutic choice in terms of tumor local control, safety, and improvement in survival. Laser ablation (LA) represents one of currently available loco-ablative techniques: light is delivered via flexible quartz fibers of diameter from 300 to 600 μm inserted into tumor lesion through either fine needles (21g Chiba needles) or large-bore catheters. The thermal destruction of tissue is achieved through conversion of absorbed light (usually infrared) into heat. A range of different imaging modalities have been used to guide percutaneous laser ablation, but ultrasound and magnetic resonance imaging are most widely employed, according to local experience and resource availability. Available clinical data suggest that LA is highly effective in terms of tumoricidal capability with an excellent safety profile; the best results in terms of long-term survival are obtained in early HCC so that LA can be proposed not only in unresectable cases but, not differently from radiofrequency ablation, also as the first-line treatment.

Changes in growth factor levels after thermal ablation in a murine model of colorectal liver metastases

OBJECTIVES

This study examines changes in the expression of growth factors following thermal ablation (TA) of selected colorectal cancer (CRC) liver metastases.

METHODS

Using mice with established CRC liver metastases, two tumours in each animal were thermally ablated. Liver and tumour tissues were collected at various time-points (days 0, 1, 2, 3, 5 and 7) following TA treatment from the ablation site and from sites distant from ablated tumour. Changes in growth factor expression (epidermal growth factor [EGF], vascular endothelial growth factor [VEGF], hepatocyte growth factor [HGF] and transforming growth factor-β[TGF-β]) in comparison with baseline levels (non-ablated) were assessed by enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry.

RESULTS

Baseline TGF-β and VEGF levels in the liver parenchyma of tumour-bearing mice were significantly higher than levels in naive liver parenchyma. Levels of VEGF and HGF decreased after TA treatment in all tissues. Levels of EGF decreased in ablated and distant tumour tissues, but displayed a tendency to increase in liver tissue. Levels of TGF-β also decreased during the first 2 days following TA, but later increased in liver and tumour tissues distant from the ablation site to a level that reached significance in tumour tissue at day 7 (P < 0.001). Decreases in growth factor levels were also observed in animals that underwent laparotomy without TA treatment, which indicates that these decreases were caused by the experimental procedure.

CONCLUSIONS

Tumour induces upregulation of TGF-β and VEGF in liver parenchyma. Growth factors decreased after TA, but this appears to be the result of the experimental procedure rather than the TA itself. However, TA resulted in increased levels of TGF-β, which may contribute to tumour recurrence.

Feasibility of computed tomography based thermometry during interstitial laser heating in bovine liver

OBJECTIVES

To assess the feasibility of computed tomography (CT) based thermometry during interstitial laser heating in the bovine liver.

METHODS

Four freshly exercised cylindrical blocks of bovine tissue were heated using a continuous laser of Nd:YAG (wavelength: 1064 nm, active length: 30 mm, power: 10-30 W). All tissues were imaged at least once before and 7 times during laser heating using CT and temperatures were simultaneously measured with 5 calibrated thermal sensors. The dependency of the average CT numbers as a function of temperature was analysed with regression analysis and a CT thermal sensitivity was derived.

RESULTS

During laser heating, the growing hypodense area was observed around the laser source and that area showed an increase as a function of time. The formation of hypodense area was caused by declining in CT numbers at increasing temperatures. The regression analysis showed an inverse linear dependency between temperature and average CT number with -0.65 ± 0.048 HU/°C (R(2) = 0.75) for the range of 18-85°C in bovine liver.

CONCLUSIONS

The non-invasive CT based thermometry during interstitial laser heating is feasible in the bovine liver. CT based thermometry could be further developed and may be of potential use during clinical LITT of the liver.

Protective effect of autophagy in laser-induced glioma cell death in vitro

BACKGROUND AND OBJECTIVE

Laser phototherapy could be potentially used for cancer treatment, but the mechanisms of laser-induced cell death are not completely understood. Autophagy is the process in which the damaged cellular proteins and organelles are engulfed by and destroyed in acidified multiple-membrane vesicles. The aim of the present study was to investigate the role of autophagy in laser-induced tumor cell death in vitro.

STUDY DESIGN/MATERIALS AND METHODS

The monolayers of U251 human glioma tumor cells were exposed to 532 nm laser light from a single mode frequency-doubled Nd-YVO4 laser. A flattened Gaussian radial profile of laser beam (0.5-4 W) was used to uniformly illuminate entire colony of cells for various amounts of time (15-120 seconds) in the absence of cell culture medium. The cells were grown for 24 hours and the cell viability was determined by crystal violet or MTT assay. The presence of autophagy was assessed after 16 hours by fluorescence microscopy/flow cytometric analysis of acridine orange-stained autophagolysosomes and Western blot analysis of the autophagosome-associated LC3-II protein. The concentration of the principal pro-autophagic protein beclin-1 was determined after 6 hours by cell-based ELISA.

RESULTS

The intracytoplasmic accumulation of autophagic vesicles, increase in LC3-II and up-regulation of beclin-1 expression were clearly observed under irradiation conditions that caused approximately 50% cytotoxicity. Post-irradiation addition of three different autophagy inhibitors (bafilomycin A1, chloroquine, or wortmannin) further increased the laser-induced cytotoxicity, without affecting non-irradiated cells.

CONCLUSIONS

These data indicate that beclin-1-dependent induction of autophagy can protect glioma cells from laser-mediated cytotoxicity.

A low cost light diffuser made of metal coil

We proposed a low cost flexible light diffuser made of metal coil to obtain an appropriate light dose against certain laser therapies in narrow bending organs. We investigated experimentally the diffusion light dose of prototype coils made of stainless steel (sus304). We measured the diffusion light intensity of the prototype coils along the irradiation direction and the circumferential direction with the various pitch distances of the prototype coils and numerical aperture (NA) of laser light beam as the characteristic parameters of the light diffusion. We measured the temperature elevation of the prototype coils to study the waste energy of these prototype coils. The FWHM on the light intensity along the prototype coils marked up to 12.8mm with the constant pitch distance of 0.09 mm and the fiber output light NA of 0.038. The FWHM on the light intensity was improved to 13.7 mm with the composite pitch distance coils of which the pitch distances were 0.09 mm in the proximate and 0.18 mm in the distal. Since the efficiency of the diffusion irradiation against the fiber output was typically 7.7% in the prototype coils of which the surface reflectance was 50%, approximately 90% of the laser light energy was transferred to the temperature elevation. We estimated the practical diffusion efficiency around 75% using the high reflection of the prototype coils surface up to 90%.

Laser ablation of hepatocellular carcinoma-A review

A wide range of local thermal ablative therapies have been developed in the treatment of non resectable hepatocellular carcinoma (HCC) in the last decade. Laser ablation (LA) and radiofrequency ablation (RFA) are the two most widely used of these. This article provides an up to date overview of the role of laser ablation in the local treatment of HCC. General principles, technique, image guidance and patient selection are discussed. A review of published data on treatment efficacy, long term outcome and complication rates of laser ablation is included and comparison with RFA made. The role of laser ablation in combination with transcatheter arterial chemoembolization is also discussed.

Mechanisms of Focal Heat Destruction of Liver Tumors

BACKGROUND

Focal heat destruction has emerged as an effective treatment strategy in selected patients with malignant liver tumors. Radiofrequency ablation, interstitial laser thermotherapy, and microwave treatment are currently the most widely applied thermal ablative techniques. A major limitation of these therapies is incomplete tumor destruction and overall high recurrences. An understanding of the mechanisms of tissue injury induced by focal hyperthermia is essential to ensure more complete tumor destruction. Here, the currently available scientific literature concerning the underlying mechanisms involved in the destruction of liver tumors by focal hyperthermia is reviewed.

METHODS

Medline was searched from 1960 to 2004 for literature regarding the use of focal hyperthermia for the treatment of liver tumors. All relevant literature was searched for further references.

RESULTS

Experimental evidence suggests that focal hyperthermic injury occurs in two distinct phases. The first phase results in direct heat injury that is determined by the total thermal energy applied, tumor biology, and the tumor microenvironment. Tumors are more susceptible to heat injury than normal cells as the result of specific biological features, reduced heat dissipating ability, and lower interstitial pH. The second phase of hyperthermic injury is indirect tissue damage that produces a progression of tissue injury after the cessation of the initial heat stimulus. This progressive injury may involve a balance of several factors, including apoptosis, microvascular damage, ischemia-reperfusion injury, Kupffer cell activation, altered cytokine expression, and alterations in the immune response. Blood flow modulation and administration of thermosensitizing agents are two methods currently used to increase the extent of direct thermal injury. The processes involved in the progression of thermal injury and therapies that may potentially modulate them remain poorly understood.

CONCLUSION

Focal hyperthermia for the treatment of liver tumors involves complex mechanisms. Evidence suggests that focal hyperthermia produces both direct and indirect tissue injury by differing underlying processes. Methods to enhance the effects of treatment to achieve complete tumor destruction should focus on manipulating these processes.

Thin cylindrical diffusers in multimode Ge-doped silica fibers

BACKGROUND AND OBJECTIVES

Cylindrical fiber diffusers are common tools in photodynamic therapy (PDT). However, large outer diameter and short length limit the indications to which they can be applied. Here a diffuser with an outer diameter of 250 microm and an active length exceeding 5 cm was developed.

STUDY DESIGN/MATERIALS AND METHODS

Diffusers based on photosensitive quartz optical fibers with a cladding diameter of 140 microm were developed using a structured beam from an excimer laser. A complete set of photometric characteristics, including longitudinal, polar, and azimuth radiance emission diagrams were collected.

RESULTS AND CONCLUSIONS

The longitudinal radiance emission is homogenous to within +/-10%. The ability to create custom designed longitudinal emission profiles was demonstrated. The variations of the polar and azimuth radiance emission diagrams were within +/- 15% from an ideal Lambertian emitter. The polar uniformity can be improved with a slight increase of the outer diameter using a diffusing recoating compound. The residual light leakage at the distal end of the fiber diffuser was suppressed to 2%. The minimal bending radius after recoating is approximately 5 mm. Maximum power distribution is > 0.5 W cm(-1).