Only about 30% of patients with hepatic metastat-ic disease are suitable for hepatic resection. The majority of patients with liver metastases or primary malignant liver tumors are not candidates for this therapeutic approach due to advanced hepatic tumor spread . To overcome this dilemma, a multi-modality treatment approach involving combined surgical, interventional, focal ablative and chemotherapeutic methods has been proposed to achieve a better five year patient survival.
With the development of focal ablative procedures, including local application of cold, heat, or drugs to destroy tumor tissue, a functional tissue sparing method has been developed. In patients with bilobar tumor spread, these new techniques allow for a combined therapeutic approach with open surgical liver resection of one liver lobe, in combination with focal ablative therapies such as cryothera-py, laser- or radio-frequency induced thermal tumor destruction in the contralateral lobe in order to pre-
Fig. 12. Recurrent HCC post-TACE. Three months post-TACE therapy of an HCC, recurrent hypervascularization of the treated area is visible (arrowhead) on a Tl-weighted arterial phase image after Gd-injection. In addition, a satellite lesion adjacent to the treated lesion is visible (arrow)
Fig. 13a-c. Cryotherapy of the resection edge during atypical liver resection. The T2-weighted unenhanced image (a) shows a decreased size of the liver due to hemi-hepatectomy and additional atypical resections of metastases. To spare as much residual liver tissue as possible, the actual resection was performed with a small resection margin with concomitant cryotherapy of the resection margins (black arrow). On the unenhanced T1-weighted image (b) the lesion shows low SI. On the T1-weighted equilibrium phase image (c) after contrast agent injection the lesion (white arrow) is sharply demarcated from surrounding liver tissue. No signs of residual or recurrent tumor tissue are visible serve the functional surrounding liver tissue [36, 37]. To achieve this objective, precise pretherapeutic imaging is necessary to characterize the tumor's location, size and segmental distribution, in order to allow accurate planning of the therapeutic strategy. In some cases the calculation of tumor volume in relation to residual liver parenchyma might be helpful to determine the post-operative outcome in terms of liver function . The method of intraoperative or interventional preconditioning of one liver lobe, for example, gives a better functional result after hepatic resection or thermal therapy . The liver lobe to be preserved can be stimulated to regenerate by selective interventional occlusion of one portal venous branch on the opposite side. The volume increase can be detected precisely by MR volume calculation [38,40].
Surgical resection of hepatic tumors should be performed if the lesion is surrounded by healthy liver tissue in order to leave a resection safety margin of 1 cm. Tumor locations near larger blood vessels or bile duct structures may make it difficult to achieve this safety margin. Therefore, cryotherapy of the resection edge with a specially designed flattened cryo-probe can be performed as a therapeutic adjunct to achieve tumor-free resection margins [41-43]. On post-operative MR imaging the resulting cryonecrosis is characterized by a flattened elliptical area (Fig. 13) with identical peripheral imaging features as endohepatic cryotherapy. Criteria for detection of residual tumor should be applied analogously.
In the large proportion of patients not suitable for curative treatment, systemic or intra-ar-terial chemotherapy has been established as a second-line therapy to achieve prolonged patient survival. Nevertheless, the five year survival of patients with colorectal carcinoma undergoing conventional chemotherapeutic treatment with 5-fluorouracil and leucovorin has proven to be very poor . Newer strategies using a combination of irinotecan, oxaliplatin and modified delivery regimes have demonstrated better response rates . This improved efficacy not only results in prolonged patient survival, but in some patients also offers the possibility of a curative treatment by surgery after down-staging . Another strategy of preinterventional tumor downsizing is neoadjuvant transarterial chemoembolization. With the combination of chemotherapeutic drugs (e.g. mitomycin) and embolization materials such as microspheres and lipiodol, a significant reduction in tumor volume is possible which then allows treatment options with curative intention, such as surgical resection or focal ablative techniques. Nevertheless, further prospective randomized trials are needed to evaluate this strategy . In this setting, MRI plays an important role in characterizing tumor volume and perfusion before and after neoadjuvant therapy in order to accurately evaluate the effectiveness of treatment and to evaluate the possibility of subsequent curative treatment.
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