Role of interstitial therapy in the treatment of liver cancer

Options for radiotherapy in the treatment of liver metastases

Technologic advances have provided the means to deliver tumoricidal doses of radiation therapy (RT) to patients with unresectable colorectal liver metastases, while avoiding critical normal tissues, providing the opportunity to use RT for curative intent treatment of metastatic disease. For the current report, the expanded role of RT, with its different techniques in the setting of metastatic colorectal cancer, from palliation to cure was reviewed.

Outcome of regional and local ablative therapies for hepatocellular carcinoma: a collective review

BACKGROUND

Transcatheter arterial (chemo) embolization (TACE), cryoablation (CA) and percutaneous ethanol injection (PEI) were the first regional and local ablative techniques that came into use for irresectable HCC. Radiofrequency ablation (RFA) and interstitial laser coagulation (ILC) followed and have now evolved rapidly. It would not be ethical to compare resection with ablation in patients well enough to undergo major surgery. Therefore, hepatic resection and hepatic transplantation remain the only curative treatment options for HCC.

METHODS

On the basis of a Medline literature search and the authors' experiences, the principles, current status and prospects of TACE and local ablative techniques in HCC are reviewed.

RESULTS

Complete tumour necrosis can be achieved in 60-100% of patients treated with PEI (70-100%), cryoablation (60-85%), RFA (80-90%) or ILC (70-97%). After TACE significant tumour response is achieved in 17-61.9% but complete tumour response is rare (0-4.8%) as viable tumour cells remain after TACE. Five-year survival rates are available for TACE (1-8%), PEI (0-70%) and cryoablation (40%). Only PEI and RFA were compared in one RCT. RFA was associated with fewer treatment sessions and a higher complete necrosis rate. Furthermore, all techniques are associated with low morbidity and mortality, but cryoablation seems to be associated with a higher morbidity rate.

CONCLUSION

TACE has shown to be a valuable therapy with survival benefits in strictly selected patients with unresectable HCC. RFA and PEI are now considered as the local ablative techniques of choice for the treatment of, preferably small, HCC. When tumours are located close to bile ducts or large vessels, PEI remains a valuable therapy. Completeness of ablation can be more easily monitored during cryoablation and another advantage of cryoablation is the possibility of edge freezing. The results of ILC are comparable to RFA with only few side effects and high tumour response rates.

Interstitial ablative techniques for hepatic tumours

BACKGROUND

Most patients with liver tumours are not suitable for surgery but interstitial ablative techniques may control disease progression and improve survival rates.

METHODS

A review was undertaken using Medline of all reported studies of cryoablation, radiofrequency ablation, microwave ablation, interstitial laser photocoagulation, high-intensity focused ultrasound and ethanol ablation of primary liver tumours and hepatic metastases.

RESULTS

Although there are no randomized clinical trials, cryoablation, thermal ablation and ethanol ablation have all been shown to be associated with improved palliation in patients with primary and secondary liver cancer. The techniques can be undertaken safely with minimal morbidity and mortality.

CONCLUSION

Although surgical resection remains the first line of treatment for selected patients with primary and secondary liver malignancies, interstitial ablative techniques are promising therapies for patients not suitable for hepatic resection or as an adjunct to liver surgery.

Hepatic cryoablation-induced acute lung injury: histopathologic findings

We have previously shown that hepatic cryoablation (cryo), but not partial hepatectomy, induces a systemic inflammatory response, with distant organ injury and overproduction of NF-kappaB-dependent cytokines. Serum tumor necrosis factor-alpha (TNF-alpha) and macrophage inflammatory protein-2 (MIP-2) levels are markedly increased 1 h and beyond after cryo compared with partial hepatectomy where no elevation occurs. NF-kappaB activation (by electrophoretic mobility shift assay) is strikingly increased in the noncryo liver (but not in the lung) at 30 min and in both the liver and lung tissue 1 h after cryo, returning to the baseline by 2 h and beyond. The current study investigated the histopathologic changes associated with cryoablation-induced acute lung injury. Animals underwent 35% hepatic resection or a similar volume hepatic cryo and were sacrificed at 1, 2, 6, and 24 h. Pulmonary histologic features were assessed using hematoxylin and eosin and immunoperoxidase staining with a macrophage-specific antibody (anti-lysozyme, 1:200 dilution, Dako, Carpinteria, CA). The following features were graded semiquantitatively (0-3): perivascular lymphoid cuffs, airspace edema and hemorrhage, margination of neutrophils within pulmonary vasculature, and the presence of macrophages with foamy cytoplasm in the pulmonary interstitium. Hepatic resection (n = 21) resulted in slight perivascular edema at 1, 2, 6, and 24 h post-resection, but there were no other significant changes. Pulmonary findings after hepatic cryo (n = 22) included prominent perivascular lymphoid cuffs 1 and 2 h following hepatic injury that were not present at any other time point (P 0.01). Marginating PMNs and foamy macrophages were more common after cryo at all time points (P<0.05, cryo vs resection). Severe lung injury, as evidenced by airspace edema and parenchymal hemorrhage, was present in four of six (67%) animals at 24 h (P 0.03). In follow-up studies immediate resection (n = 15) of the cryo-treated liver prior to thawing prevented the pulmonary changes. The findings of pulmonary perivascular interstitial macrophages 2 h following hepatic cryo suggests that hepatic cytokine production may induce downstream recruitment of pulmonary macrophages, which may contribute to subsequent severe lung injury. This study suggests that a soluble mediator from direct liver injury leads to neutrophilic lung inflammation and this is associated with the thawing phase of cryoablation.

Histopathological features of liver damage induced by laser ablation in rabbits

BACKGROUND AND OBJECTIVE

Possible mechanisms that promote or interfere with the effects of laser ablation of the liver have not been clarified. The aim of this study was to define the chronological alterations in the normal rabbit liver at early stages after laser ablation.

STUDY DESIGN/MATERIALS AND METHODS

Rabbit livers were ablated with a laser via an optical fiber and then analyzed histopathologically by immunostaining for heat shock protein 70 (HSP70) and by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL) method.

RESULTS

The lesions increased in size progressively over the 24 h that followed ablation and the area of the lesion coincided with the area that had been heated above 43 degrees C. TUNEL-positive hepatocytes were surrounded, at some distance, by HSP70-positive hepatocytes were surrounded, at some distance, by HSP70-positive hepatocytes at 6 h, and such cells were in contact with each other at 24 h.

CONCLUSIONS

Injury to hepatocytes induced by laser ablation increases for 24 h and dying cells express nuclear HSP70, with subsequent fragmentation of DNA.

Biliary structures lead to tumour recurrences after laser-induced interstitial thermotherapy

BACKGROUND AND OBJECTIVE

Thermal diffusion during laser-induced interstitial thermotherapy (LITT) has not yet been fully investigated in heterogeneous tissue architecture such as liver. LITT was performed on rabbit liver tumours to analyse the role of biliary structures in thermal diffusion.

STUDY DESIGN/MATERIALS AND METHODS

Twenty-four VX2 tumours were grafted onto 12 rabbit livers. The animals were randomly separated into two groups when tumour size reached 8 mm. Thermotherapy was performed by delivering the 830-nm output of a diode laser to the centre of the tumour with a 300-,microm fibre. Irradiation conditions were 1.5 W over 900 sec. On day 7 or 14, the tumours were removed and stained with haematoxylin-eosin and picrosirius red F3BA (PR). Thermal damage was evaluated by PR and electron microscopic examinations.

RESULTS

Among the treated tumours, recurrences were found both at the periphery (one on day 7, seven on day 14) and within the treated area (two on day 7, two on day 14). All recurrences were located in the vicinity of the biliary structures, which are frequently spared from thermal injury.

CONCLUSION

Biliary ducts lead to a heat sink, thereby facilitating tumour recurrences.

Interstitial laser hyperthermia, a new method in the management of fibroadenoma of the breast: A pilot study

BACKGROUND AND OBJECTIVE

This study attempts to evaluate the effect of interstitial laser hyperthermia in breast fibroadenomas as an outpatient procedure.

STUDY DESIGN/MATERIALS AND METHODS

In an uncontrolled prospective study, 27 patients younger than 35 years were subjected to laser phototherapy of their breast fibroadenomas. Under real-time ultrasound monitoring, Nd:YAG laser (1,064 nm wavelength) was used at 2 W for 300 sec (600 J) in a continuous wave mode to produce interstitial hyperthermia. Follow-ups were done at 2, 4, and 8 weeks. Subsequently, excision biopsy of residual lumps was performed.

RESULTS

There was significant decrease in clinical and sonographic sizes (P < 0.001). Follow-up ultrasound showed a progressive change of hyperechoic texture, from a heterogeneous to a nearly homogeneous one. There were minimal scars (2-3 mm) and no keloid or abscess formation.

CONCLUSION

Interstitial laser hyperthermia is a safe, precise, and minimally invasive outpatient procedure for in situ destruction of breast fibroadenomas.

Systemic effects and side effects of interstitial techniques used in liver tissue

BACKGROUND

Percutaneous ethanol injection (PEI) and cryosurgery are increasingly used for the treatment of liver malignancies. To create a safety margin and to destroy completely diffusely growing tumors, the precise destruction of healthy liver tissue is necessary. Little is known about the effects of operating on this type of tissue. This study evaluated the effects and side effects of PEI and cryosurgery when applied to normal parenchyma of the liver.

STUDY DESIGN

Two groups of six minipigs each were treated with either PEI or cryosurgery to create necrosis in the liver. During and after the procedures, vital signs were monitored and necrotic areas were observed by ultrasonography. Standard and immunohistochemistry stains were made from samples of the necrosis, the liver, and the lung.

RESULTS

In the PEI group, thromboembolic complications occurred in all animals (fatality rate 50%). Hematogenous spread of hepatocytes was demonstrated by immunohistochemistry and was a cause of pulmonary embolism. In the cryosurgery group, neither specific complications nor signs of cell spillage occurred. Because of an isolating effect of blood perfusion, hepatocytes close to the portal triads were less damaged, vital cells were present in the periphery, and the necroses were smaller than the induced lesions.

CONCLUSIONS

The effect of PEI in healthy liver tissue is unpredictable. This makes the creation of a safety margin or the treatment of a diffusely infiltrating tumor impossible. PEI always introduces the risk of hematogenous cell spread. Effects of cryosurgery are less dependent on tissue qualities. In both techniques, the real extent of complete tissue destruction cannot be visualized by ultrasonography.

Epi-illumination fluorescent light microscopy for the in vivo study of rat hepatic microvascular response to cryothermia

To elucidate the hepatic microvascular response to cryothermia, we studied the liver microcirculation of Sprague-Dawley rats after one and two 4-minute freeze-thaw cycles using intravital fluorescence microscopy. Irrespective of the number of freeze-thaw cycles applied, the nature of hepatic microvascular injury was characterized by complete stasis of sinusoidal blood flow within the central part of the cryolesions and heterogeneous sinusoidal perfusion in a critically perfused border zone located at the periphery of the lesions. Analysis over time (2 hours) revealed a successive shutdown of sinusoidal perfusion within this critically perfused border zone, which was caused by intravascularly lodging cell aggregates, blocking the lumen of individual sinusoids. The aggregates consisted of parenchymal cells and cell fragments, but did not include leukocytes or platelets. Strikingly, microvascular perfusion failure was associated with Ito cell disintegration and marked dilation of sinusoids (15.6 +/- 0.8 microm vs. 8.8 +/- 0.8 microm; P <.05). This excludes sinusoidal constriction as the cause of nutritive perfusion failure, and may indicate dysfunction of Ito cell-regulated vasomotor control by cryothermia. However, because circulating cell aggregates were frequently observed plugging individual microvessels, dilation of sinusoids may just be the result of passive distension caused by outflow blockade. Analysis of hepatic tissue at 8 weeks after cryothermia did not reveal regeneration and microvascular remodeling, but loss of hepatic tissue, which corresponded well with the tissue area presenting with sinusoidal perfusion failure during the initial observation period after cryothermia. The fact that there was no recovery of sinusoidal perfusion over the initial 2-hour observation period, but loss of tissue after 8 weeks, supports the view that cryothermia induces injury not only by direct low-temperature-mediated action, but also through ischemia caused by irreversible deterioration of the microcirculation.

Interstitial laser coagulation for hepatic tumours

BACKGROUND

The potential role of interstitial laser coagulation (ILC) for patients with irresectable hepatic tumours is currently being investigated. Since its introduction in 1983 it has evolved into an innovative minimally invasive technique.

METHODS

On the basis of a Medline literature search and the authors' experience, the principles, current state and prospects of ILC for hepatic tumours are reviewed.

RESULTS

Animal studies and early clinical studies have shown the safety and feasibility of ILC. The site of interest can be approached at laparoscopy or percutaneously and treatment is easily repeatable. Recent advances include the use of fibres with a cylindrical diffusing light-emitting tip, the length of which is adaptable to tumour diameter, water-cooled fibre systems, simultaneous multiple fibre application, and hepatic inflow occlusion during laser treatment. ILC allows complete destruction of tumours up to 5 cm in diameter. Currently a limitation is the lack of reliable real-time monitoring of laser-induced effects but progress in magnetic resonance imaging techniques should allow accurate temperature measurements to be obtained rapidly during treatment. However, the actual benefit of ILC in terms of patient survival remains to be investigated.

CONCLUSION

In terms of tools and experience, ILC has now been developed sufficiently to study its effect on survival of patients with irresectable hepatic tumours.

Magnetic resonance imaging-histomorphologic correlation studies on paramagnetic metalloporphyrins in rat models of necrosis

RATIONALE AND OBJECTIVES

The authors intended to confirm previous findings that paramagnetic porphyrins are avid only for intratumoral nonviable tissues, but not for viable tumor cells, and to test the hypothesis that necrosis, regardless of location and origin, can be visualized by metalloporphyrin enhanced magnetic resonance imaging (MRI).

METHODS

Intravenous administrations of gadolinium mesoporphyrin (Gd-MP), manganese tetraphenylporphyrin (Mn-TPP), manganese methylpyrroporphyrin-gadopentetate dimeglumine complex (Mn-MPP-Gd) and manganese tetra(4-sulfonatophenyl)porphyrin (MnTPPS4) at 0.05 mmol/kg were compared with those of gadopentetate dimeglumine (Gd-DTPA) at 0.1 mmol/kg in 38 rats with cholestatic liver necrosis, alcohol- and laser-induced coagulation necrosis in liver, and skeletal muscle, reperfused hepatic infarction, and segmental renal infarction. T1-weighted spin echo MRI (TR/TE = 300/15 mseconds) was acquired before and as long as 48 hours after injection, matched with histologic findings, and correlated with Gd/ Mn tissue content measurements.

RESULTS

Both Gd-DTPA and the four metalloporphyrins initially caused a similar nonspecific negative contrast enhancement in the necrosis. However, a strong and persisting positive enhancement (necrosis-to-normal contrast ratio ranging from 1.5 to 2.0) developed only with metalloporphyrins in all types of necrosis. In liver and kidney, Gd and Mn concentrations at 24 hours were comparable in necrotic and normal tissues. In muscle, the concentrations were more than eight times higher in necrotic than in normal tissue.

CONCLUSIONS

The implied affinity of metalloporphyrins for necrosis with presumably increased relaxivity suggests a possible mode of targetability for MRI contrast media that may elicit novel applications.

Magnetic resonance-guided laparoscopic interstitial laser therapy of the liver

BACKGROUND

There is a necessity for an imaging method during laparoscopy to get a three-dimensional access to the target. In this study we evaluated laparoscopic interstitial laser therapy of the liver under magnetic resonance imaging guidance.

METHODS

Five domestic pigs underwent laparoscopy in an open-configuration magnetic resonance system. Under simultaneous real-time magnetic resonance imaging interstitial laser therapy was applied to the liver. Magnetic resonance images, macroscopic aspects of the lesions, and light microscopic findings were compared.

RESULTS

The interventions could be safely performed. There was no image artifact caused by instruments or by the carbon dioxide. Dynamic gadolinium-enhanced imaging proved to significantly predict the macroscopic volume of the laser lesions.

CONCLUSIONS

Magnetic resonance-guided laparoscopic interstitial laser therapy of the liver combines the advantages of minimal invasive surgery and magnetic resonance imaging. Further development should focus on laparoscopic instruments and temperature sensitive sequences.

Current and future treatment modalities for hepatocellular carcinoma

This article reviews recent innovations in the treatment of Hepatocellular carcinoma (HCC), which, although a common malignancy, has often proved difficult to diagnose and treat effectively. The epidemiology and natural history of HCC are discussed, as well as treatments such as hepatic resection, liver transplantation, and cryosurgery, among others.

Generation and observation of radio frequency thermal lesion ablation for interventional magnetic resonance imaging

RATIONALE AND OBJECTIVES

Recently, there has been increased interest in interventional magnetic resonance (MR) imaging and minimally invasive cancer therapy via radio frequency (RF) thermal ablation. In this work, we examined RF thermal lesion generation in phantoms and ex vivo bovine liver and correlated them with MR images under a variety of conditions, which begins our assessment of the role of MR imaging in this new method for cancer treatment.

METHODS

Radio frequency lesions were created in gel phantoms and ex vivo bovine liver, using stationary (bovine liver) and variable speed (gel) moving electrodes to create lesions with shapes mimicking tumors. Ex vivo bovine liver lesions were made with the tissue held at room temperature (n = 4) and in a 37 degrees C saline bath (n = 3) using a 16-gauge electrode (tip temperature: 70 degrees C, 80 degrees C, and 90 degrees C; ablation time: 1-13 minutes). Electrical impedance and RF power were plotted during ablation. After ablation, RF-induced lesions were imaged with a 0.2-tesla (T) MR system using a variety of pulse sequences.

RESULTS

Complex shaped lesions were created successfully in phantoms. Averaged maximum ex vivo lesion volume made at 90 degrees C ablation experiments holding the tissue temperature at 37 degrees C and at room temperature were 1.58 +/- 0.35 cm3 and 1.0 +/- 0.26 cm3 respectively (confidence interval: 90%). The aspect ratios and RF power of the lesions decreased as ablations proceeded. Impedance dropped during the first 2 minutes of the ablation. Ex vivo lesions appeared as regions of low-signal amplitude in T2-weighted MR images.

CONCLUSIONS

Phantom ablation experience may be useful and applicable in thermotherapy planning. Lesions made in ex vivo bovine liver held at 37 degrees C via a saline bath are larger than those created at room temperature. Lesions shapes are ablation time dependent until thermal equilibrium is reached. Impedance reduction and lesion formation are related; 0.2-T MR systems can image RF energy-induced thermal lesions.

Liver tumor ablation techniques

Despite advances in surgical technique, patients with primary and secondary liver tumors remain a difficult management problem, as most tumors are unresectable at presentation. Alternative therapies, involving the in situ destruction of liver tumors, have recently come under scrutiny as palliative options. Percutaneous ethanol injection and cryosurgery have been advocated, but both have associated technical difficulties and adverse effects. Novel liver tumor ablation techniques have recently been developed that work via the induction of localized hyperthermia. There is mounting evidence to support a hypothesis that cancer cells are more selectively sensitive to heat than are normal cells, due to the poor blood supply of neoplastic tissue and the decreased vasodilatation capacity of the neovascular bed. These ablative modalities induce a variable degree of tumor necrosis in unresectable tumors, and therefore may provide useful palliation. Clinical trials are needed to determine the true nature and degree of any palliative benefit. In addition, the determinants of treatment efficacy and the predictability of the necrotic zone must be better understood before these techniques can be contemplated as alternatives to liver resection for cure.

Treatment principles in advanced colorectal cancer

BACKGROUND

Colorectal cancer is an important disease in the Australian community. Whilst there has been much discussion about the appropriate management of local disease, particularly with respect to the issue of adjuvant therapy, there has been relatively little local discussion of treatment options in metastatic colorectal cancer.

METHODS

The critical principles underlying treatment in this setting are briefly outlined in the present article, indicating wherever possible what options could be considered standard, and based on the available literature, which approaches must still be considered experimental at this time.

RESULTS

Overall, the results of treatment in this group of patients remain poor.

CONCLUSION

Further clinical trials are required to address the issues affecting patients with metastatic colorectal cancer.

Estimation of volumes of distribution and intratumoral ethanol concentrations by computed tomography scanning after percutaneous ethanol injection

RATIONALE AND OBJECTIVES

We developed a technique for estimating the volumes of distribution and intratumoral ethanol concentrations using computed tomography (CT) scanning in patients undergoing percutaneous ethanol injection (PEI) treatment of malignant hepatic tumors.

METHODS

A phantom containing anhydrous ethanol diluted with deionized distilled water to concentrations of 0-100% ethanol was scanned by CT. Thirty-seven treatment sessions were performed on eight patients with malignant hepatic tumors undergoing PEI under CT guidance. The patients were scanned pre- and post-PEI, and a region of interest containing the treated hepatic tissue was selected for pixels between -250 and 15 Hounsfield units (H). The mean density of the pixels in this range was computed and the concentration of ethanol estimated. Volumes of distribution of ethanol and intratumoral concentration were then correlated with volume of ethanol injected during PEI. The ratios of volumes of distribution of ethanol to ethanol injected (adjusted in-range [IR]/volume injected) were compared for responders (n = 4) and nonresponders (n = 4).

RESULTS

CT numbers in the phantom scaled linearly with ethanol concentration; 100% ethanol measured -234 H. On CT scans after PEI, the volume of distribution of ethanol correlated positively with the volume injected. Calculated intratumoral ethanol concentrations ranged from 4% to 31%. The adjusted IR/volume injected was significantly higher for responders than nonresponders (p < .5).

CONCLUSION

CT density data can be used to estimate volume of ethanol distribution in tissue; a larger relative intratumoral distribution of alcohol appears to correlate with a favorable response to PEI. However, CT measurement of intratumoral ethanol concentrations may require more complex computational techniques.

Hepatic artery chemotherapy for colorectal liver metastases

Fifty per cent of patients with colorectal cancer develop hepatic metastases but only a minority are candidates for potentially curative surgical resection. Hepatic artery chemotherapy (HAC) has been used to treat patients with non-resectable metastases confined to the liver. Although response rates to HAC have been shown to be higher than response rates to systemic chemotherapy, the advantage in terms of survival has been debated. Furthermore, HAC requires surgical catheter placement which adds to the cost and morbidity of treatment. There have now been eight prospective randomized trials of HAC vs intravenous chemotherapy and/or supportive therapy. The present paper analyses the results of these trials with particular reference to survival. Surgical morbidity, treatment-related toxicity and cost are also discussed.

Intraoperative ultrasonography in detection of hepatic metastases from colorectal cancer

PURPOSE

This study was designed to compare diagnostic accuracies of measuring liver enzymes, preoperative ultrasonography, surgical examination, and intraoperative ultrasonography for detection of liver metastases from colorectal cancer.

METHODS

Blind, prospective comparisons of diagnostic examinations mentioned above were performed in 295 consecutive patients with colorectal cancer. An experienced ultrasonologist performed the preoperative examinations, and results were unknown to the other experienced ultrasonologist who performed the intraoperative examinations. The latter, also was unaware of the findings by the surgeon. The presence of metastases was further assessed by ultrasonography three months postoperatively, as well as additional surgery and liver biopsy in some of the patients.

RESULTS

The sensitivity of intraoperative ultrasonography (62/64) was significantly superior to that of surgical exploration (54/64) and that of preoperative ultrasonography (45/64). The lowest sensitivity was presented by liver enzymes. Bilobar metastases were detected in 42 of 46 patients by intraoperative ultrasonography but in only 33 patients by the surgeon. Intraoperative ultrasonography demonstrated the highest specificity of all examinations.

CONCLUSIONS

Intraoperative ultrasonography reduces the number of patients with liver metastases from being subjected to superfluous or even harmful liver surgery, and it may increase the number in whom liver surgery will prolong life.

Adjuvant therapy with essential fatty acids (EFAs) for primary liver tumors: some hypotheses

Hepatocarcinoma is responsible for approximately 1 million deaths annually. It is usually discovered at an advanced stage and, if inoperable, has a poor prognosis. New therapies combining chemotherapy, hyperthermia, radiotherapy and immunomodulators have been recently attempted with various levels of success. Once the tumor is detected at an early stage, some possibilities of cure seem to emerge either by intratumoral percutaneous injection (PEI) of alcohol or by chemoembolization and interstitial hyperthermia. When the tumor volume is more than 5 cm, these therapies are less successful and radiotherapy can be used. All the techniques described have some limits; PEI, for instance, does not achieve a complete eradication of lesions > 3 cm and a non-homogenous alcohol distribution within the tumor leads to areas of necrosis. Radiotherapy, even if effective, is limited by dose-related radiation hepatitis. Another important limiting factor is the incomplete response to therapy and tumor recurrence. Essential fatty acids, especially gamma linolenic acid (GLA) and eicosapentaenoic acid (EPA) are discussed here for their ability to control primary tumor proliferation and increase response to chemotherapy, radiotherapy and hyperthermic treatment, thanks to their effects on cellular membranes (increased lipoperoxidation and modification of tumor stroma).

Applications of lasers in gastroenterology

In this article the clinical uses of lasers in gastroenterology are reviewed. The endoscopic delivery of light for therapeutic as well as diagnostic purposes is discussed. Current research directions in the field are also indicated where appropriate.

Ultrastructural alterations in heated canine myocardium

BACKGROUND AND OBJECTIVE

The anisotropy factor of light scattering (g) (wavelength 632.8 nm) in heated myocardium decreases as a function of temperature, suggesting, on the basis of Mie theory of light scattering, formation of an increasing number of particles with diameters smaller than the incident wavelength.

STUDY DESIGN/MATERIALS AND METHODS

To test this hypothesis, fresh myocardium was heated at constant temperatures between 37 degrees C and 75 degrees C for 1,000 s. Changes in size and number of granules generated by disintegrating organelles and sarcomeres were studied as a function of temperature by transmission electron microscopy, planimetry and particle counting.

RESULTS

The mitochondria started to disintegrate at 45 degrees C and myofibrils between 45 degrees C and 50 degrees C into increasing numbers of small electron dense granules (diameter 50-200 nm), which correlated with the observed decrease of g from 0.93 +/- 0.02 (at room temperature to 45 degrees C) to 0.77 +/- 0.05 at 75 degrees C.

CONCLUSION

The scattering coefficient microseconds of 161 +/- 33 cm-1 did not change significantly.

The effect of cryotherapy on the cremaster muscle microcirculation in vivo

The effect of cryotherapy on normal striated muscle was investigated using 18 adult male rats. Animals were divided into two groups, an experimental cryotherapy group and a control group receiving sham treatment. After the surgical procedure animals were allowed to equilibrate and vessel diameters, macromolecular leakage and blood flow were assessed before the cremaster muscle was frozen to -60 degrees C. After thawing measurements were taken every 15 min over a 2 h period. Cryotherapy resulted in an initial reduction in blood flow followed by a brief period of reperfusion, with complete vascular stasis eventually observed. Macromolecular leakage occurred from all vessels, which mirrored the fluctuations in blood flow. Transient changes in vessel diameters were also observed. Histology confirmed the in vivo observations of vessel congestion and muscle damage. The data suggest that cessation of flow and increased macromolecular leakage within the muscle may contribute to the cell death and tumour necrosis observed following cryotherapy.

Effects of nimodipine and dexamethasone on low-level CO2 laser-induced release of 51chromium from canine 2C5 gliosarcoma cells

Low-energy penumbral irradiation of surgical lasers may produce undesirable effects on surrounding tissues. This study used a 51Cr cell labeling technique to determine if gliosarcoma cells could be therapeutically protected prior to their exposure to low-power laser irradiation. Canine 2C5 gliosarcoma cells with intracellular 51Cr were treated with nimodipine and/or dexamethasone and then exposed to low-power levels of CO2 laser. The 51Cr was released from the cells in a dose-dependent fashion following exposure to laser energy. Correlative analysis of the data indicated that a strong direct relationship between laser fluence and 51Cr release did exist for controls and drug-treated groups with coefficients of correlation r > or = +0.90 and coefficients of determination r2 > or = 0.82. However, comparison of the data from the drug-treated and control groups found that there was no significant difference between them (P > .05). Therefore, no protective or detrimental effects were observed with the use of nimodipine and/or dexamethasone on the gliosarcoma cells as tested in this system. Further investigation is necessary in order to define the mechanisms by which low-power level lasers affect these cells. These effects do not appear to be mediated through localization of mechanisms to the cell membranes or their constituent Ca2+ channels.

Interstitial Nd:YAG laser coagulation with a cylindrical diffusing fiber tip in experimental liver metastases

Interstitial laser coagulation as a means of destructing hepatic metastases was investigated. Colon carcinoma CC531 was implanted in the liver of 42 Wag/Rij rats; 20 days later, tumors (5.5 +/- 0.2 mm) were exposed to 1,064 nm Nd:YAG laser light at 4 W/cm and either 600, 1,200, 2,400, 3,400, or 4,800 J/cm from a 0.5 cm Helioseal coated cylindrical diffuser. Temperature and fluence rate were measured at the tumor boundary. Lesions were studied on day 2 and 36 posttreatment by light microscopy. Tumor proliferative activity was assessed by bromodeoxyuridine incorporation. Liver damage and function were determined by serum liver enzymes and antipyrine clearance. Fluence rate increased during laser treatment up to 170%; mean temperature increased logarithmically up to 69.7 degrees C. Short-term light microscopy showed coagulation necrosis of 7-11 mm without charring. Lesion size and liver enzymes increased logarithmically with laser energy applied. No deterioration in liver function was found. At 4,800 J/cm complete tumor remission occurred in three of four animals. This study shows the ability of interstitial laser coagulation to produce selective destruction of colonic tumor within the liver.

Dependence of laser photocoagulation on interstitial delivery parameters

Photocoagulation was performed ex vivo between tissue slabs by delivering continuous-wave laser energy from an optical fiber either directly, or by depositing the energy into a 2.4 mm diameter steel sphere at the fiber tip. The dependence of photocoagulation lesions on the following variables was assessed: (1) energy source: Nd:YAG-532 nm, 1,064 nm +/- steel sphere, (2) tissue type: porcine muscle (light), bovine muscle (dark), (3) delivered power: P = 1.5-3.0 W (porcine), 1.0-2.5 W (bovine), (4) exposure duration: T = 300-1500 s. The resulting cross-sectional photocoagulation lesions are summarized as follows: 532 nm: elongated; central charring in all cases; 1,064 nm: circular; central charring only in bovine for P > or = 2.0 W, T > or = 500 s; sphere: circular; central charring in bovine for P > or = 1.5 W and porcine for P > or = 2.0 W. These experiments suggest photocoagulation lesion size decreases as optical penetration increases. The results indicate that interstitial laser photocoagulation lesions > 10 mm diameter can be made without charring in both lightly and heavily pigmented tissues ex vivo by delivering 1,064 nm laser energy at sufficiently low power for at least 1,000 s from well-polished optical fibers.

Surgical management of malignant islet cell tumors

The surgical management of pancreatic islet cell carcinomas poses a complicated set of questions resulting from their rare occurrence and the difficulty in establishing a diagnosis in early cases or, conversely, the problems inherent in dealing with metastatic disease. However, because their biologic behavior is rather indolent, a real opportunity exists not only for cure but also for meaningful palliation. These goals apply both to the tumor itself and the effects of the hormones they may secrete. The challenge facing the multidisciplinary management team in general, and the surgeon specifically, is to achieve the optimal combination of surgical resection and other treatment options. While the precept of aggressive excision applies to most islet cell carcinomas, it is not universally applicable. In contrast to other islet cell tumors, insulinomas are overwhelmingly benign, and are well treated by enucleation or limited pancreatic resection. Although based on relatively few cases, cytoreductive surgery seems beneficial for malignant insulinomas. Advances that have occurred over the past decade in Zollinger-Ellison syndrome have markedly altered surgical management. Medication which reliably prevents ulcer formation has permitted the surgical perspective to be redirected from end organ ablation to curative tumor excision. Multicentricity and metastases, however, limit the extent to which cure can actually be achieved. Patients with vasoactive intestinal peptide-producing tumors and glucagonomas are very rare, and when possible, should undergo tumor resection to correct the severe hormonally caused metabolic derangements. Increasingly recognized are islet cell carcinomas that do not produce clinical syndromes. They may be confused with ductal carcinomas, but when resected, lead to distinctly superior survival rates among patients.

Selecting source locations in multifiber interstitial laser photocoagulation

A theoretical basis and practical algorithm are described for selecting optimal fiber source locations in multifiber interstitial laser photocoagulation (ILP). By analyzing the shape of overlapping coagulation patterns, the optimal separation of adjacent point heat sources inside a flat target volume boundary is shown to be d* = 2 square root of 2rc, where rc is the coagulation radius of a single source. Against a curved boundary, the algorithm specifies how d* should be altered. To assess the validity of the theory, ILP was conducted in bovine muscle by delivering 1064 nm laser energy through two or four plane-cut optical fibers simultaneously. Delivered power, exposure duration, and source separation were varied. The observed coagulation patterns matched the theory-predicted patterns at delivered powers of 1.60W and 1.85W, but not at 2.40W. Also, the experiments indicate that reciprocity of delivered power and exposure duration is invalid for ILP.

Low-level CO2 laser-induced release of 51chromium from canine 2C5 gliosarcoma cells

Recently, interest has grown in the area of low-power laser effects upon tissues. We used a 51Cr cell labeling technique with glioma tissue to better understand these effects. Canine 2C5 gliosarcoma cells with intracellular 51Cr were exposed to CO2 laser in the range of 0.2 to 3.0 J/cm2. Correlative analysis of the data indicated that there is a strong direct relationship between laser fluence and the percent of total intracellular 51Cr released from the glioma cells with a coefficient of correlation (r) of +0.93. The calculated standard error of the correlation coefficient was +/- 0.06 and the coefficient of determination (r2) was 0.86. These results indicate that the 51Cr cell labeling technique is a useful method for quantifying the low-power laser effects on the integrity of the cell membrane of gliosarcoma cells in vitro. However, further investigation is needed to clarify the specific mechanisms by which the CO2 laser induces changes upon these cells.

Water-jet-cooled Nd:YAG laser coagulation of experimental liver metastases: correlation between ultrasonography and histology

To establish the value of ultrasonography in imaging laser coagulation of tumor and surrounding tissue, the relation between measurements on ultrasound and histology was determined in a rat tumor model. A piece of colon carcinoma CC531 was implanted in the liver of 21 Wag/Rij rats; 20 days later, tumors (mean diameter 5.3 mm) were treated with a water-jet-cooled Nd:YAG laser at 10 W and either 150 J, 300 J, 600 J, 1,200 J, 1,700 J, or 2,400 J. Ultrasonography was done just pre- and immediately post-laser treatment. The animals were sacrificed and livers removed for light microscopical evaluation. Depth and width of coagulation were measured directly on ultrasound, and on histological samples by computer-assisted image analysis. Laser treatment did not change the echogenic aspect of the tumor on ultrasound. However, liver damage appeared hypoechoic compared to normal liver. A significant correlation was found between the total size of the lesion on ultrasound and histology (P = 0.015, r = 0.57 for depth; P = 0.012, r = 0.58 for width), suggesting that laser induced tumor destruction may be derived from the amount of surrounding hepatic damage on ultrasound.

Interstitial laser hyperthermia: a new approach for treating liver metastases

The palliative management of hepatic metastases remains unsatisfactory. There is a need for a simple non invasive technique which can stop or retard the rate of tumour growth. In principle, Interstitial Laser hyperthermia may fulfil such a role. In experimental studies, this technique produced precise in situ necrosis within solid organs which healed safely. In a pilot feasibility study, we treated ten patients with a total of 18 hepatic metastases on 31 occasions using a percutaneous approach to achieve an overall objective response rate of 44%. The treatment proved simple to perform, was well tolerated and produced radiological evidence of necrosis in small metastases (diameter less than or equal to 3 cm). However, further research is required before the technique can be regarded as established. Its future role in most cases will be to control the growth of discrete hepatic metastases unsuitable for resection. In instances where the extent of necrosis can be matched accurately to tumour volume, the potential for cure exists.

Liver resection and laser hyperthermia

Table 2 provides a comparison of these interstitial and in situ techniques, assessing several criteria and utilizing and expanding on an excellent review by Masters et al. The rapid advance of technology and cross-fertilization between groups using different interstitial techniques will lead to a clear understanding of the benefits and limits of each. However, there is essentially no information at the present time to suggest that these techniques should be used in lieu of hepatic resection in an attempt to cure patients who are good operative risks. There are insufficient data of a controlled nature to determine that there has been a survival or palliative benefit in many of the patients so treated. Nevertheless, as it is clear that these treatments cause tissue destruction in an appropriate nonmorbid way and that they are well tolerated with low risk to the patients, it is entirely conceivable that interstitial techniques will replace hepatic resection in some instances in the future, particularly for lesions smaller than 3 cm.