Cryosurgery and radiofrequency ablation for unresectable colorectal liver metastases

Chemotherapy response evaluation with FDG-PET in patients with colorectal cancer

BACKGROUND

The aim of this prospective study was to evaluate the value of F-18-fluorodeoxyglucose-positron emission tomography (FDG-PET) for early assessment of chemotherapy response in patients with advanced colorectal cancer.

METHODS

Dynamic FDG-PET was carried out before and at 2 (n = 50) and 6 months (n = 19) after the start of treatment. Quantitative Patlak analysis [metabolic rate of glucose (MRGlu)] and a simplified method to measure glucose metabolism [standardized uptake value (SUV)] were evaluated. The predictive value of changes in glucose metabolism was assessed with Cox proportional regression analysis. Overall survival (OS) and progression-free survival (PFS) were calculated using Kaplan-Meier estimates.

RESULTS

There was an increase in the rates of death (P = 0.049 for DeltaMRGlu PET1-2; P = 0.017 for DeltaSUV PET1-2; P = 0.032 for DeltaMRGlu PET1-3; P = 0.048 for DeltaSUV PET1-3) and progression (P = 0.026 for DeltaMRGlu PET1-2; P = 0.035 for DeltaSUV PET1-2; P = 0.041 for DeltaMRGlu PET1-3; P = 0.081 for DeltaSUV PET1-3) associated with worse response as assessed by PET on Cox proportional regression analysis. The OS and PFS analysis showed a significant predictive value at broad ranges of DeltaMRGlu and DeltaSUV cut-off levels.

CONCLUSION

The degree of chemotherapy-induced changes in tumor glucose metabolism is highly predictive for patient outcome. The use of FDG-PET for therapy monitoring seems clinically feasible since simplified methods (SUV) are sufficiently reliable.

Bimodal electric tissue ablation-long term studies of morbidity and pathological change

BACKGROUND

Radiofrequency ablation is a popular method of treating unresectable liver tumors but tumors greater than 3 cm in diameter have a much greater risk of local recurrence after treatment. Bimodal electric tissue ablation is a modified form of radiofrequency ablation that creates significantly larger ablations by the addition of extra direct current circuitry. This may help to reduce the risk of local recurrence in these larger tumors. Prior to use in a clinical setting, a long term study was performed to assess associated morbidity and the pathological changes in the ablations.

METHODS

In eight pigs, six ablations were performed in each liver. Pigs were euthanized at 2 d, 2 wk, 2 mo, and 4 mo, and the ablations were assessed macroscopically and microscopically for pathological change. Regular blood tests were performed to assess changes in liver function. At death, any other abnormalities detected were reported.

RESULTS

Histopathological examination of ablation zones revealed tissue death by coagulative necrosis and healing by fibrotic scarring. Transient rises in serum liver enzymes were seen in the postoperative period. Skin necrosis was noted at the site of the positive electrode of the direct electrical current but no other form of morbidity was seen associated with the procedure.

CONCLUSIONS

Although the positive electrode placement requires further consideration, bimodal electric tissue ablation appears to be safe and behaves in a similar fashion to other thermal therapies such as standard radiofrequency ablation.

Prudent application of radiofrequency ablation in resectable colorectal liver metastasis

Radiofrequency ablation (RFA) for liver metastasis of colorectal (H-CRC) origin is a well-documented technique in surgically unresectable disease. Overall recurrence figures appear inferior to resection but are based on a selection of patients with unresectable disease, often due to multiple localisations of extensive disease. Lesion based recurrence is probably more appropriate to predict results of RFA in surgically resectable H-CRC and figures may be good enough to consider RFA an alternative treatment in high risk patients.

Bimodal electric tissue ablation-modified radiofrequency ablation with a le veen electrode in a pig model

Radiofrequency ablation (RFA) is a method of treating non-resectable liver tumors by use of a high-frequency alternating electrical current. Concerns have been raised as the local recurrence rates following treatment have been reported to be as high as 47%. The size of the ablation is limited by charring of adjacent tissues. It is hypothesized that by hydrating the liver, we can reduce charring, thus producing larger ablations, and that this can be achieved by addition of a direct electrical current to the electrical circuit. Using a pig model, standard RFA control ablations were created in the left lobe of the liver. Ablations using the modified circuit were created in the right lobe. At the end of the procedure, the pig was killed by lethal injection and the liver harvested. From the explanted liver, the diameter of each ablation was measured and the modified ablations were compared with controls using restricted maximum likelihood variance analysis. From 4 pigs, 14 controls and 12 modified ablations were produced. The mean diameter of the controls was 27.78 mm (+/- SE 3.37 mm). The mean diameter of the modified ablation was 49.55 mm (+/- SE 3.46 mm), which was significantly larger than the controls (P < 0.001). This study has shown that by modification of the standard RFA circuit with the addition of a direct electrical current, significantly larger ablations can be produced. By using this technique, the number of ablations required to treat one tumor would be less and it is anticipated this could reduce the rate of local recurrence.

Thermal maps around two adjacent cryoprobes creating overlapping ablations in porcine liver, lung, and kidney

PURPOSE

To determine cryoprobe spacing requirements in order to achieve overlapping ablation zones using the same ablation protocol in porcine liver, lung, and kidney.

MATERIALS AND METHODS

Six female pigs underwent cryoablation of the liver, lung, and kidney. Two 2.4-mm cryoprobes were spaced 20-mm apart with seven 16-gauge thermometers placed linearly and in axis with the cryoprobes at 5-mm increments from one another. The placement of the thermometers was such that three were placed between the two probes and two were placed laterally to each probe. Simultaneous use of the cryoprobes, using 12- and 8-minute double-freeze cycles, was performed with intratissue temperature monitoring during the procedure.

RESULTS

The center temperatures between the two cryoprobes in kidney, lung, and liver were -25.87( degrees )C +/- 1.91, -6.47(degrees )C +/- 3.94, and 0.48( degrees )C +/- 6.69, respectively. Dual 2.4-mm cryoprobes in our model achieved acute pathological complete coagulative necrosis zone at the center of the ablation zone between the cryoprobes only in the kidney tissue where a mean diameter of the acute complete coagulative necrosis zone was 39.6 mm +/- 0.76 mm.

CONCLUSIONS

The critical temperature of -20 degrees C was not reached at the midpoint between the probes with the 20-mm spacing arrangement in the lung and liver. These results emphasize the need for individualized organ ablation treatment protocols.

A cost-utility analysis of treatments for malignant liver tumours: a pilot project

BACKGROUND

Hepatic resection is the standard treatment for colorectal liver metastases when feasible. Techniques such as radiofrequency ablation (RFA) have been the subject of ongoing research in hopes of achieving a similar survival to that achieved with hepatic resection, but with less morbidity and better quality of life (QOL). The aim was to to generate a hypothesis concerning the cost-utility of various treatments that may be further tested with randomized trials in the future.

PATIENTS AND METHODS

This was a prospective, non-randomized pilot study comparing the cost-utility of hepatic resection, RFA, systemic chemotherapy, and symptom control alone for colorectal liver metastases. All patients with newly diagnosed liver malignancies were eligible. QOL was measured serially with the Health Utilities Index. Costs, in 2001 Canadian dollars, were captured from the viewpoint of society in general.

RESULTS

In all, 40 patients were enrolled in the study: 7 underwent hepatic resection, 7 underwent RFA (sometimes in combination with resection), 20 received systemic chemotherapy, and 6 received symptom control alone. Liver resection appeared to be the most effective approach, with an average benefit of 2.58 QALYs (quality-adjusted life years) compared with 1.95 QALYs for RFA, 1.18 QALYs for chemotherapy, and 0.82 QALYs for symptom control alone, resulting in cost-utility ratios of $7792, $8056, $12,571, and $4788 per QALY, respectively.

DISCUSSION

The cost-utility of hepatic resection and RFA appeared similar even though patients receiving RFA had more advanced disease. The role of RFA is still being defined; however, if long-term survival proves to be promising, then this study lends support to the conduct of randomized controlled trials in the future.

Comparison between local ablative therapy and chemotherapy for non-resectable colorectal liver metastases: a prospective study

BACKGROUND

There is a growing interest for the use of local ablative techniques in patients with non-resectable colorectal liver metastases. Evidence on the efficacy over systemic chemotherapy is, however, extremely weak. In this prospective study we aim to assess the additional benefits of local tumour ablation.

METHODS

A consecutive series of 201 colorectal cancer patients, without extrahepatic disease, that underwent laparotomy for surgical treatment of liver metastases, were prospectively followed for survival and HRQoL. At laparotomy three groups were identified: patients in whom radical resection of metastases proved feasible, patients in whom resection was not feasible and received local ablative therapy, and patients in whom resection or local ablation was not feasible for technical reasons and who received systemic chemotherapy.

FINDINGS

Patients in the chemotherapy and in local ablation group were comparable for all prognostic variables tested. For the local ablation group overall survival at 2 and 5 years was 56 and 27%, respectively (median 31 months, n = 45), for the chemotherapy group 51 and 15%, respectively (median 26 months, n = 39) (P = 0.252). After resection these figures were 83 and 51%, respectively (median 61 months, n = 117) (P < 0.001). The median DFS after local ablation was 9 months, HRQoL was restored within 3 months. Patients after local ablation gained far more QALY's (317) than in the chemotherapy group (165) (P < 0.001).

INTERPRETATION

Although overall survival did not reached statistical significance, the median DFS of 9 months suggests a beneficial effect of local tumour ablation for non-resectable colorectal liver metastases. Moreover, compared with systemic chemotherapy more QALY's were gained after local ablative therapy.

Current role of radiofrequency ablation for the treatment of colorectal liver metastases

BACKGROUND AND METHOD

This paper reviews the current status of radiofrequency ablation in the treatment of colorectal liver metastases. Relevant studies with at least ten patients that reported rates of complete tumour ablation, local recurrence, or survival from 1 to 5 years after treatment were included in the review.

RESULTS AND CONCLUSION

Only six studies that reported at least 3-year survival were identified, with results ranging from 37 to 58 per cent. Some of these figures are promising, given that the patients were considered to have unresectable disease. However, available evidence is limited and hepatic resection remains the standard of care when feasible; radiofrequency ablation cannot be considered an equivalent. Radiofrequency ablation does, however, appear to have a role in treating unresectable disease, and may also be used in conjunction with resection to extend its limits.

FDG-PET in colorectal cancer

[18F]Fluorodeoxyglucose (FDG) positron emission tomography (PET) is a useful imaging tool in the evolving management of patients with colorectal carcinoma. This technique is able to measure and visualize metabolic changes in cancer cells. This feature results in the ability to distinguish viable tumor from scar tissue, in the detection of tumor foci at an earlier stage than possible by conventional anatomic imaging and in the measurement of alterations in tumor metabolism, indicative of tumor response to therapy. Nowadays, FDG-PET plays a pivotal role in staging patients before surgical resection of recurrence and metastases, in the localization of recurrence in patients with an unexplained rise in serum carcinoembryonic antigen and in assessment of residual masses after treatment. In the presurgical evaluation, FDG-PET may be best used in conjunction with anatomic imaging in order to combine the benefits of both anatomical (CT) and functional (PET) information, which leads to significant improvements in preoperative liver staging and preoperative judgment on the feasibility of resection. Integration of FDG-PET into the management algorithm of these categories of patients alters and improves therapeutic management, reduces morbidity due to futile surgery, leads to substantial cost savings and probably also to a better patient outcome. FDG-PET also appears to have great potential in monitoring the success of local ablative therapies soon after intervention and in the prediction and evaluation of response to radiotherapy, systemic therapy, and combinations thereof. This review aims to outline the current and future role of FDG-PET in the field of colorectal cancer.

Image-Guided Microtherapy for Tumor Ablation: From Thermal Coagulation to Advanced Irradiation Techniques

Image-guided tumor ablation has been established as a valuable adjunct in oncological treatment concepts. The majority of micro-therapeutic procedures is performed by applying thermal ablation, such as radiofrequency or laser. However, in view of the limitations of thermal ablation regarding tumor size or adjacent risk structures, novel techniques combining brachytherapy with modern interventional techniques have demonstrated favorable outcomes. In addition, advances in non-invasive percutaneous irradiation, such as extracranial stereotaxy, have demonstrated very competitive preliminary results. In this article, state-of-the-art techniques for micro-therapeutic tumor ablation are being described.