Computed Tomography–Guided High-Dose-Rate Brachytherapy in Hepatocellular Carcinoma: Safety, Efficacy, and Effect on Survival

Image-guided high-dose-rate brachytherapy of malignancies in various inner organs - technique, indications, and perspectives

In the last few years, minimally invasive tumor ablation performed by interventional radiologists has gained increasing relevance in oncologic patient care. Limitations of thermal ablation techniques such as radiofrequency ablation (RFA), microwave ablation (MWA), and laser-induced thermotherapy (LITT), including large tumor size, cooling effects of adjacent vessels, and tumor location near thermosensitive structures, have led to the development of image-guided high-dose-rate (HDR) brachytherapy, especially for the treatment of liver malignancies. This article reviews technical properties of image-guided brachytherapy, indications and its current clinical role in multimodal cancer treatment. Furthermore, perspectives of this novel therapy option will be discussed.

Manually controlled steerable needle for MRI-guided percutaneous interventions

This study aims to develop and evaluate a manually controlled steerable needle that is compatible with and visible on MRI to facilitate full intra-procedural control and accurate navigation in percutaneous interventions. The steerable needle has a working channel that provides a lumen to a cutting stylet or a therapeutic instrument. A steering mechanism based on cable-operated compliant elements is integrated in the working channel. The needle can be steered by adjusting the orientation of the needle tip through manipulation of the handle. The steering mechanism is evaluated by recording needle deflection at constant steering angles. A steering angle of 20.3° results in a deflection of 9.1–13.3 mm in gelatin and 4.6–18.9 mm in porcine liver tissue at an insertion depth of 60 mm. Additionally, the possibility to control the needle path under MRI guidance is evaluated in a gelatin phantom. The needle can be steered to targets at different locations while starting from the same initial position and orientation under MRI guidance with generally available sequences. The steerable needle offers flexibility to the physician in control and choice of the needle path when navigating the needle toward the target position, which allows for optimization of individual treatment and may increase target accuracy.

Activity-based cost analysis of hepatic tumor ablation using CT-guided high-dose rate brachytherapy or CT-guided radiofrequency ablation in hepatocellular carcinoma

Purpose

To analyse and compare the costs of hepatic tumor ablation with computed tomography (CT)-guided high-dose rate brachytherapy (CT-HDRBT) and CT-guided radiofrequency ablation (CT-RFA) as two alternative minimally invasive treatment options of hepatocellular carcinoma (HCC).

Materials and methods

An activity based process model was created determining working steps and required staff of CT-RFA and CT-HDRBT. Prorated costs of equipment use (purchase, depreciation, and maintenance), costs of staff, and expenditure for disposables were identified in a sample of 20 patients (10 treated by CT-RFA and 10 by CT-HDRBT) and compared. A sensitivity and break even analysis was performed to analyse the dependence of costs on the number of patients treated annually with both methods.

Results

Costs of CT-RFA were nearly stable with mean overall costs of approximately 1909 €, 1847 €, 1816 € and 1801 € per patient when treating 25, 50, 100 or 200 patients annually, as the main factor influencing the costs of this procedure was the single-use RFA probe. Mean costs of CT-HDRBT decreased significantly per patient ablation with a rising number of patients treated annually, with prorated costs of 3442 €, 1962 €, 1222 € and 852 € when treating 25, 50, 100 or 200 patients, due to low costs of single-use disposables compared to high annual fix-costs which proportionally decreased per patient with a higher number of patients treated annually. A break-even between both methods was reached when treating at least 55 patients annually.

Conclusion

Although CT-HDRBT is a more complex procedure with more staff involved, it can be performed at lower costs per patient from the perspective of the medical provider when treating more than 55 patients compared to CT-RFA, mainly due to lower costs for disposables and a decreasing percentage of fixed costs with an increasing number of treatments.

CT-guided high-dose-rate brachytherapy in the interdisciplinary treatment of patients with liver metastases of pancreatic cancer

BACKGROUND

CT-guided high-dose-rate brachytherapy (CT-HDRBT) is an interventional radiologic technique for local ablation of primary and secondary malignomas applying a radiation source through a brachycatheter percutaneously into the targeted lesion. The aim of this study was to assess local tumor control, safety and efficacy of CT-HDRBT in the treatment of liver metastases of pancreatic cancer.

METHODS

Twenty consecutive patients with 49 unresectable liver metastases of pancreatic cancer were included in this retrospective trial and treated with CT-HDRBT, applied as a single fraction high-dose irradiation (15-20 Gy) using a 192Ir-source. Primary endpoint was local tumor control and secondary endpoints were complications, progression-free survival and overall survival.

RESULTS

The mean tumor diameter was 29 mm (range 10-73). The mean irradiation time was 20 minutes (range 7-42). The mean coverage of the clinical target volume was 98% (range 88%-100%). The mean D100 was 18.1 Gy and the median D100 was 19.78 Gy. Three major complications occurred with post-interventional abscesses, three of which were seen in 15 patients with biliodigestive anastomosis (20%) and overall 15%. The mean follow-up time was 13.7 months (range 1.4-55.0). The median progression-free survival was 4.9 months (range 1.4-42.9, mean 9.4). Local recurrence occurred in 5 (10%) of 49 metastases treated. The median overall survival after CT-HDRBT was 8.6 months (range 1.5-55.3). Eleven patients received chemotherapy after ablation with a median progression-free survival of 4.9 months (mean 12.9). Nine patients did not receive chemotherapy after intervention with a median progression-free survival of 3.2 months (mean 5.0). The rate of local tumor control was 91% in both groups after 12 months.

CONCLUSION

CT-HDRBT was safe and effective for the treatment of liver metastases of pancreatic cancer.

Extending the Frontiers Beyond Thermal Ablation by Radiofrequency Ablation: SBRT, Brachytherapy, SIRT (Radioembolization)

Metastatic spread of the primary is still defined as the systemic stage of disease in treatment guidelines for various solid tumors. This definition is the rationale for systemic therapy. Interestingly and despite the concept of systemic involvement, surgical resection as a local treatment has proven to yield long-term outcomes in a subset of patients with limited metastatic disease, supporting the concept of oligometastatic disease. Radiofrequency ablation has yielded favorable outcomes in patients with hepatocellular carcinoma and colorectal metastases, and some studies indicate its prognostic potential in combined treatments with systemic therapies. However, some significant technical limitations apply, such as size limitation, heat sink effects, and unpredictable heat distribution to adjacent risk structures. Interventional and non-invasive radiotherapeutic techniques may overcome these limitations, expanding the options for oligometastatic patients and cytoreductive concepts. Current data suggest very high local control rates even in large tumors at any given location in the human body. The article focusses on the characteristics and possibilities of stereotactic body radiation therapy, interstitial high-dose-rate brachytherapy, and Yttrium-90 radioembolization. In this article, we discuss the differences of the technical preferences as well as their impact on indications. Current data is presented and discussed with a focus on application in oligometastatic or cytoreductive concepts in different tumor biologies.

Is There Any Evidence for a Role of Local Treatment in Cholangiocarcinoma?

Background

Most cholangiocarcinomas (CCA) are locally advanced and unresectable at the time of diagnosis. Currently, chemotherapy combining gemcitabine with a platinum agent is the recommended first-line treatment regimen for advanced biliary tract cancer. However, median overall survival is only approximately 1 year. As the hepatic tumor burden is the limiting factor for the prognosis of these patients, local tumor control is essential.

Methods

We present and discuss the current evidence for such therapy options for patients with CCA.

Results

Local and locoregional therapies have been shown to be well tolerated and can contribute to tumor control in the context of a comprehensive oncologic treatment strategy, and may prolong survival of patients with advanced CCA. Unfortunately, only few high-quality clinical trials are available.

Conclusion

Randomized prospective clinical trials enrolling larger numbers of patients need to be carried out to elucidate the precise value of these treatments alone as well as in combination with systemic chemotherapy.

High-dose-rate brachytherapy planning in palliative management of hilar cholangiocarcinoma: a case study

Introduction:

Cholangiocarcinoma (CCA) or klatskin’s tumour involves malignant tumours at the liver hilum’s biliary confluence. Incidence of CCA results in unresectable tumours that require appropriate therapy to improve quality of life. The liver is considered as the most frequent site of tumour recurrence. Promising results of long-term survival have been established with computed tomography-guided high-dose-rate brachytherapy.

Materials and methods:

Intraluminal brachytherapy (ILBT) is performed through the percutaneous transhapatic bile duct drain tube (PTBD). The passage of the brachytherapy guide tube through the bile duct is more complex compared with oesophageal/endobronchial application.

Results/discussion:

It results in a recoiled view of the tube in the abdominal region of the computed tomography (CT) scan. Owing to inherent artefacts induced by metal stents in CT scans, intersected view is possible between the ILBT guide tube and the intra-hepatic drain tube. It would mislead the planner to track wrong passage that could result in fatal error.

Conclusion:

In this case study, we contoured the ILBT guide tube by cross-verifying its position with a digitally reconstructed radiograph (DRR) before catheter tracking. Thus, it ensures precise simulation of source dwell positions, thereby avoiding high-dose delivery to nearby vital organs such as intestines, liver hilum and blood vessels.

Efficacy and safety of image-guided interstitial single fraction high-dose-rate brachytherapy in the management of metastatic malignant melanoma

PURPOSE

Computed tomography (CT) or magnetic resonance imaging (MRI) guided brachytherapy provides high tumor control rates in hepatocellular carcinoma (HCC) and colorectal liver metastases. In contrast to thermal ablation methods such as radiofrequency ablation (RFA), much less restrictions apply with respect to tumor location or size. In this study, we determined the efficacy and safety of CT- or MRI-guided brachytherapy in metastatic melanoma.

MATERIAL AND METHODS

Fifty-two metastases of malignant melanoma in 14 patients were included in this retrospective study. Local tumor control and safety were evaluated as primary and secondary endpoints. Furthermore, we evaluated overall survival and progression free survival. Tumor locations were liver (n = 31), lung (n = 15), adrenal (n = 3), lymph nodes (n = 2), and kidney (n = 1). Treatment planning was performed using three-dimensional CT or MRI data acquired after percutaneous applicator positioning under CT or open MRI guidance. Subsequently, single fraction high-dose-rate (HDR) brachytherapy was applied using a (192)Iridium source. Clinical and cross-sectional follow-up were performed every 3 months post intervention.

RESULTS

The median diameter of treated lesions was 1.5 cm (range: 0.7-10 cm). Doses between 15 and 20 Gy were applied (median dose: 19.9 Gy). The mean irradiation time ranged between 7-45 minutes. After treatment, there was one patient with a cholangitis. After a median follow up of five months, the median local tumor control was 90%. The median overall survival of the patients was 8 months. The median progression free survival of the patients was 6 months.

CONCLUSIONS

Image-guided HDR brachytherapy is a safe and effective treatment procedure in metastatic malignant melanoma.

Radiation-induced liver damage: correlation of histopathology with hepatobiliary magnetic resonance imaging, a feasibility study

PURPOSE

Radiotherapy of liver malignancies shows promising results (radioembolization, stereotactic irradiation, interstitial brachytherapy). Regardless of the route of application, a certain amount of nontumorous liver parenchyma will be collaterally damaged by radiation. The functional reserve may be significantly reduced with an impact on further treatment planning. Monitoring of radiation-induced liver damage by imaging is neither established nor validated. We performed an analysis to correlate the histopathological presence of radiation-induced liver damage with functional magnetic resonance imaging (MRI) utilizing hepatobiliary contrast media (Gd-BOPTA).

METHODS

Patients undergoing local high-dose-rate brachytherapy for whom a follow-up hepatobiliary MRI within 120 days after radiotherapy as well as an evaluable liver biopsy from radiation-exposed liver tissue within 7 days before MRI were retrospectively identified. Planning computed tomography (CT)/dosimetry was merged to the CT-documentation of the liver biopsy and to the MRI. Presence/absence of radiation-induced liver damage (histopathology) and Gd-BOPTA uptake (MRI) as well as the dose applied during brachytherapy at the site of tissue sampling was determined.

RESULTS

Fourteen biopsies from eight patients were evaluated. In all cases with histopathological evidence of radiation-induced liver damage (n = 11), no uptake of Gd-BOPTA was seen. In the remaining three, cases no radiation-induced liver damage but Gd-BOPTA uptake was seen. Presence of radiation-induced liver damage and absence of Gd-BOPTA uptake was correlated with a former high-dose exposition.

CONCLUSIONS

Absence of hepatobiliary MRI contrast media uptake in radiation-exposed liver parenchyma may indicate radiation-induced liver damage. Confirmatory studies are warranted.

Computed tomography-guided interstitial high dose rate brachytherapy for centrally located liver tumours: a single institution study

OBJECTIVES

To evaluate the clinical outcome of computed tomography (CT)-guided interstitial (IRT) high-dose-rate (HDR) brachytherapy (BRT) in the treatment of unresectable primary and secondary liver malignancies. This report updates and expands our previously described experience with this treatment technique.

METHODS

Forty-one patients with 50 tumours adjacent to the liver hilum and bile duct bifurcation were treated in 59 interventions of CT-guided IRT HDR BRT. The tumours were larger than 4 cm with a median volume of 84 cm(3) (38-1,348 cm(3)). The IRT HDR BRT delivered a median total physical dose of 20.0 Gy (7.0-32.0 Gy) in twice daily fractions of median 7.0 Gy (4.0-10.0 Gy) in 19 patients and in once daily fractions of median 8.0 Gy (7.0-14.0 Gy) in 22 patients.

RESULTS

With a median follow-up of 12.4 months, the local control for metastatic hepatic tumours was 89 %, 73 % and 63 % at 6, 12 and 18 months respectively. The local control for primary hepatic tumours was 90 %, 81 % and 50 % at 6, 12 and 18 months respectively. Severe side effects occurred in 5.0 % of interventions with no treatment-related deaths.

CONCLUSIONS

CT-guided IRT HDR BRT is a promising procedure for the radiation treatment of centrally located liver malignancies.

KEY POINTS

• Interstitial high-dose-rate brachytherapy (IRT HDR BRT) is a promising treatment for central liver tumours • CT-guided IRT HDR BRT is safe for treating extensive tumours • CT-guided IRT HDR BRT could play a role in managing unresectable hepatic malignancies.

Preliminary experience with CT-guided high-dose rate brachytherapy as an alternative treatment for hepatic recurrence of cholangiocarcinoma

BACKGROUND

Intrahepatic recurrence after resection of intrahepatic or hilar cholangiocarcinoma represents a main reason for the poor prognosis of bile duct cancer. As no standard treatment has been established so far, the aim of this study was to analyse the safety and efficacy of computed tomography-guided high-dose rate brachytherapy (CT-HDRBT) as an alternative treatment in those patients.

METHODS

The outcomes of 10 patients, who had been treated at least once for recurrent cholangiocarcinoma by CT-HDRBT, were retrospectively analysed.

RESULTS

The median survival of all patients after primary liver resection was 85 months [95% confidence interval (CI) 68.129-101.871] with overall 1- and 5-year survival rates of 100% and 78.7%, respectively. After the occurrence of intrahepatic tumour recurrence, a total of 15 CT-HDRBT procedures were performed, alone or combined with other recurrence treatments, without any major complications according to the Society of Interventional Radiology classification. The 1-year and 5-year survival rates after recurrence treatment were 77.1% and 51.4%, respectively.

CONCLUSIONS

CT-HDRBT represents a safe treatment option for patients with recurrent bile duct cancer. As a part of a multimodal concept, CT-HDRBT might lead to a prolongation of survival in selected patients but further studies are urgently needed to prove this concept.

Treatment for liver metastasis from renal cell carcinoma with computed-tomography-guided high-dose-rate brachytherapy (CT-HDRBT): a case series

PURPOSE

To retrospectively analyze the clinical outcome of patients with hepatic metastases from renal cell carcinoma who were treated with computed-tomography-guided high-dose-rate brachytherapy (CT-HDRBT).

METHODS

Ten patients (7 men and 3 women; median age 72 ± 7.9 years) with a total number of 16 hepatic metastases from histologically proven renal cell carcinoma were treated with CT-HDRBT after discussing the case in an interdisciplinary tumor conference. All patients had underwent nephrectomy before CT-HDRBT. Three patients had extrahepatic manifestations (2 lung and 1 bone). Six patients had received immunotherapy or targeted therapy before CT-HDRBT. Follow-up included gadoxetic acid (Gd-EOB-DTPA) enhanced MRI two times within 6-8 weeks and after that every 3 months after treatment to evaluate treatment efficacy.

RESULTS

Mean follow-up time was 21.6 ± 13.7 months. One patient developed local and systemic (pulmonary and osseous) progression after 10.8 months which was treated with targeted therapy and died 20.3 months after CT-HDRBT. None of the remaining nine patients developed local progression or died during the follow-up period. Five patients developed systemic progression (3 pulmonary, 1 osseous and 1 locally at the site of nephrectomy) after an average of 19.7 ± 5.5 months.

CONCLUSIONS

CT-HDRBT is a viable alternative to hepatic resection of liver metastases from renal cell carcinoma in selected patients.

Percutaneous computed tomography-guided high-dose-rate brachytherapy ablation of breast cancer liver metastases: initial experience with 80 lesions

PURPOSE

To analyze initial experience with computed tomography-guided high-dose-rate brachytherapy (CT-HDRBT) ablation of breast cancer liver metastases (BCLM).

MATERIALS AND METHODS

Between January 2008 and December 2010, 37 consecutive women with 80 liver metastases were treated with CT-HDRBT in 56 sessions. Mean age was 58.6 years (range, 34-83 y). Treatment was performed by CT-guided applicator placement and high-dose-rate brachytherapy with an iridium-192 source. The mean radiation dose was 18.57 Gy (standard deviation 2.27). Tumor response was evaluated by gadoxetic acid-enhanced liver magnetic resonance (MR) imaging performed before treatment, 6 weeks after treatment, and every 3 months thereafter.

RESULTS

Two patients were lost to follow-up; the remaining 35 patients were available for MR imaging evaluation for a mean follow-up time of 11.6 months (range 3-32 mo). Mean tumor diameter was 25.5 mm (range 8-74 mm). Two (2.6%) local recurrences were observed after local tumor control for 10 months and 12 months. Both local progressions were successfully retreated. Distant tumor progression (new metastases or enlargement of nontreated metastases) occurred during the follow-up period in 11 (31.4%) patients. Seven (20%) patients died during the follow-up period. Overall survival ranged from 3-39 months (median 18 months).

CONCLUSIONS

CT-HDRBT is a safe and effective ablative therapy, providing a high rate of local tumor control in patients with BCLM.

Modelling survival in hepatocellular carcinoma

OBJECTIVES

To identify the pattern of the risk of death over long-term in unresectable hepatocellular carcinoma by determining the appropriate distribution to extrapolate overall survival and to assess the role of the Weibull distribution as the standard survival model in oncology.

RESEARCH DESIGN AND METHODS

To select the appropriate distribution, three types of data sources have been analysed. Patient level data from two randomized controlled trials and published Kaplan-Meier curves from a systematic literature review provided short term follow-up data. They were supplemented with patient level data, with long-term follow-up from the Cancer Institute New South Wales, Australia. Published Kaplan-Meier curves were read in and a time-to-event dataset was created. Distributions were fitted to the data from the different sources separately. Their fit was assessed visually and compared using statistical criteria based on log-likelihood, the Akaike information criterion (AIC), and the Bayesian information criterion (BIC).

RESULTS

Based on both published and patient-level, and both short- and long-term follow-up data, the Weibull distribution, used very often in cost-effectiveness models in oncology, does not seem to offer a good fit in hepatocellular carcinoma among the different survival models. The best fitting distribution appears to be the lognormal, with loglogistic as the second-best fitting function. Results were consistent between the different sources of data.

CONCLUSIONS

In unresectable hepatocellular carcinoma, the Weibull model, which is often treated at the gold standard, does not appear to be appropriate based on different sources of data (two clinical trials, a retrospective database and published Kaplan-Meier curves). Lognormal distribution seems to be the most appropriate distribution for extrapolating overall survival.

[Update on interstitial brachytherapy]

CLINICAL/METHODICAL ISSUE

Minimally invasive treatment procedures, such as image-guided local tumour ablation have gained increasing relevance in oncologic concepts. Limitations of thermal ablation procedures have led to the development of percutaneous, computed tomography (CT) guided brachytherapy.

STANDARD RADIOLOGICAL METHODS

Thermal ablation procedures, such as radiofrequency ablation (RFA) and laser-induced thermotherapy (LITT) show limitations regarding maximum tumour size (<5 cm), cooling effects of adjacent vessels and surrounding risk structures.

METHODICAL INNOVATIONS

The image-guided interstitial brachytherapy allows the single application of high-dose rate (HDR) irradiation with an extensive protracted cytotoxic effect. Adjacent risk structures play a minor role due to the steep dose gradient outside the clinical target volume.

PERFORMANCE

Studies using CT-guided brachytherapy resulted in a local tumour control rate of approximately 90% after 12 months in the treatment of hepatocellular carcinoma (HCC) and 70-90% in the treatment of colorectal metastases or cholangiocellular carcinoma (CCC). Similar response rates were also seen in the treatment of metastases of renal cell carcinoma (RCC), non-small cell lung cancer (NSCLC) or neuroendocrine tumours. In colorectal liver metastases and HCC the method has proven to have a positive impact on prognosis.

ACHIEVEMENTS

In contrast to thermal ablation the method can be used without restriction with respect to tumour location. Cooling effects do not play a role. It has already been applied in more than 5,000 cases and it is used in clinical routine.

PRACTICAL RECOMMENDATIONS

Image-guided brachytherapy is safe and effective and has found its way into the clinical routine.

Computed tomography-guided brachytherapy for liver cancer

Limitations of thermal liver cancer ablation have led to the development of percutaneous, catheter-based brachytherapy for the treatment of liver malignancies. Computed tomography (CT)-guided brachytherapy has been used to treat primary and metastatic liver cancers, including very large tumors >10 cm. Cooling effects by adjacent blood vessels are not a concern in brachytherapy, and the method may be used safely in tumors unsuitable for thermal ablation that are close to the liver hilum due to the relatively high radiation tolerance of bile duct. CT scanning is used for dosimetry planning after catheter implantation and also to guide the catheter placement itself. Major complications, including postinterventional bleeding, are rare despite frequent application of this technique in a salvage situation. Patients with liver cirrhosis have an increased risk for complications. Prospective trials of CT-guided brachytherapy have been performed with promising survival rates for liver metastases and hepatocellular carcinoma, respectively. In this article, the radiobiological and technical properties of CT-guided brachytherapy, appropriate patients for treatment, and prospective trials that have been published to date are reviewed.

Hepatocellular carcinoma: computed-tomography-guided high-dose-rate brachytherapy (CT-HDRBT) ablation of large (5-7 cm) and very large (>7 cm) tumours

OBJECTIVES

Evaluate the clinical outcome of CT-guided high-dose-rate-brachytherapy (CT-HDRBT) of hepatocellular carcinoma (HCC) larger than 5 cm in diameter with the goal of local tumour control (LTC).

METHODS

Thirty-five patients with 35 unresectable HCCs ranging in size from 5 to 12 cm (mean: 7.1 cm) were treated with CT-HDRBT. Tumours were classified into two groups according to diameter: "large lesions" (5-7 cm) and "very large lesions" (>7 cm). Tumour response was evaluated by Gd-EOB-DTPA-enhanced liver magnetic resonance imaging (MRI) performed before, 6 weeks after, and then every 3 months after treatment. Endpoints included local tumour control (LTC), progression-free survival (PFS) and overall survival (OS).

RESULTS

Nineteen tumours were classified as "large" and 16 as "very large". Complete tumour enclosure was achieved in all patients after the first CT-HDRBT session. Five patients were lost to follow-up. At a mean follow-up of 12.8 months, two patients had local progression (6.7%), one in each group. Nine patients (30%) experienced distant progression, five (26.3%) in the "large" and four (25%) in the "very large" group. No patients died during the follow-up period. No major complications were recorded.

CONCLUSIONS

CT-HDRBT is a promising therapy for HCCs that exceed indications for thermal ablation.

KEY POINTS

• Computed Tomography guided high-dose-rate brachytherapy offers new therapeutic options for hepatocellular carcinoma • CT-HDRBT can be safely practised in HCCs exceeding 5 cm in diameter • CT-HDRBT offers high rate of local control where thermal ablation is impossible • CT-HDRBT could be a valid alternative to TACE for intermediate stage HCC.

In vivo assessment of catheter positioning accuracy and prolonged irradiation time on liver tolerance dose after single-fraction 192Ir high-dose-rate brachytherapy

BACKGROUND

To assess brachytherapy catheter positioning accuracy and to evaluate the effects of prolonged irradiation time on the tolerance dose of normal liver parenchyma following single-fraction irradiation with 192Ir.

MATERIALS AND METHODS

Fifty patients with 76 malignant liver tumors treated by computed tomography (CT)-guided high-dose-rate brachytherapy (HDR-BT) were included in the study. The prescribed radiation dose was delivered by 1 - 11 catheters with exposure times in the range of 844 - 4432 seconds. Magnetic resonance imaging (MRI) datasets for assessing irradiation effects on normal liver tissue, edema, and hepatocyte dysfunction, obtained 6 and 12 weeks after HDR-BT, were merged with 3D dosimetry data. The isodose of the treatment plan covering the same volume as the irradiation effect was taken as a surrogate for the liver tissue tolerance dose. Catheter positioning accuracy was assessed by calculating the shift between the 3D center coordinates of the irradiation effect volume and the tolerance dose volume for 38 irradiation effects in 30 patients induced by catheters implanted in nearly parallel arrangement. Effects of prolonged irradiation were assessed in areas where the irradiation effect volume and tolerance dose volume did not overlap (mismatch areas) by using a catheter contribution index. This index was calculated for 48 irradiation effects induced by at least two catheters in 44 patients.

RESULTS

Positioning accuracy of the brachytherapy catheters was 5-6 mm. The orthogonal and axial shifts between the center coordinates of the irradiation effect volume and the tolerance dose volume in relation to the direction vector of catheter implantation were highly correlated and in first approximation identically in the T1-w and T2-w MRI sequences (p = 0.003 and p < 0.001, respectively), as were the shifts between 6 and 12 weeks examinations (p = 0.001 and p = 0.004, respectively). There was a significant shift of the irradiation effect towards the catheter entry site compared with the planned dose distribution (p < 0.005). Prolonged treatment time increases the normal tissue tolerance dose. Here, the catheter contribution indices indicated a lower tolerance dose of the liver parenchyma in areas with prolonged irradiation (p < 0.005).

CONCLUSIONS

Positioning accuracy of brachytherapy catheters is sufficient for clinical practice. Reduced tolerance dose in areas exposed to prolonged irradiation is contradictory to results published in the current literature. Effects of prolonged dose administration on the liver tolerance dose for treatment times of up to 60 minutes per HDR-BT session are not pronounced compared to effects of positioning accuracy of the brachytherapy catheters and are therefore of minor importance in treatment planning.

Morphological and functional MDCT: problem-solving tool and surrogate biomarker for hepatic disease clinical care and drug discovery in the era of personalized medicine

This article explains the significant role of morphological and functional multidetector computer tomography (MDCT) in combination with imaging postprocessing algorithms served as a problem-solving tool and noninvasive surrogate biomarker to effectively improve hepatic diseases characterization, detection, tumor staging and prognosis, therapy response assessment, and novel drug discovery programs, partial liver resection and transplantation, and MDCT-guided interventions in the era of personalized medicine. State-of-the-art MDCT depicts and quantifies hepatic disease over conventional CT for not only depicting lesion location, size, and extent but also detecting changes in tumor biologic behavior caused by therapy or tumor progression before morphologic changes. Color-encoded parameter display provides important functional information on blood flow, permeability, leakage space, and blood volume. Together with other relevant biomarkers and genomics, the imaging modality is being developed and validated as a biomarker to early response to novel, targeted anti-VEGF(R)/PDGFR or antivascular/angiogenesis agents as its parameters correlate with immunohistochemical surrogates of tumor angiogenesis and molecular features of malignancies. MDCT holds incremental value to World Health Organization response criteria and Response Evaluation Criteria in Solid Tumors in liver disease management. MDCT volumetric measurement of future remnant liver is the most important factor influencing the outcome of patients who underwent partial liver resection and transplantation. MDCT-guided interventional methods deliver personalized therapies locally in the human body. MDCT will hold more scientific impact when it is fused with other imaging probes to yield comprehensive information regarding changes in liver disease at different levels (anatomic, metabolic, molecular, histologic, and other levels).

Radiobiological restrictions and tolerance doses of repeated single-fraction hdr-irradiation of intersecting small liver volumes for recurrent hepatic metastases

BACKGROUND

To assess radiobiological restrictions and tolerance doses as well as other toxic effects derived from repeated applications of single-fraction high dose rate irradiation of small liver volumes in clinical practice.

METHODS

Twenty patients with liver metastases were treated repeatedly (2 - 4 times) at identical or intersecting locations by CT-guided interstitial brachytherapy with varying time intervals. Magnetic resonance imaging using the hepatocyte selective contrast media Gd-BOPTA was performed before and after treatment to determine the volume of hepatocyte function loss (called pseudolesion), and the last acquired MRI data set was merged with the dose distributions of all administered brachytherapies. We calculated the BED (biologically equivalent dose for a single dose d = 2 Gy) for different alpha/beta values (2, 3, 10, 20, 100) based on the linear-quadratic model and estimated the tolerance dose for liver parenchyma D90 as the BED exposing 90% of the pseudolesion in MRI.

RESULTS

The tolerance doses D90 after repeated brachytherapy sessions were found between 22 - 24 Gy and proved only slightly dependent on alpha/beta in the clinically relevant range of alpha/beta = 2 - 10 Gy. Variance analysis showed a significant dependency of D90 with respect to the intervals between the first irradiation and the MRI control (p < 0.05), and to the number of interventions. In addition, we observed a significant inverse correlation (p = 0.037) between D90 and the pseudolesion's volume. No symptoms of liver dysfunction or other toxic effects such as abscess formation occurred during the follow-up time, neither acute nor on the long-term.

CONCLUSIONS

Inactivation of liver parenchyma occurs at a BED of approx. 22 - 24 Gy corresponding to a single dose of ~10 Gy (alpha/beta ~ 5 Gy). This tolerance dose is consistent with the large potential to treat oligotopic and/or recurrent liver metastases by CT-guided HDR brachytherapy without radiation-induced liver disease (RILD). Repeated small volume irradiation may be applied safely within the limits of this study.

MR-guided liver tumor ablation employing open high-field 1.0T MRI for image-guided brachytherapy

OBJECTIVE

To determine the feasibility and safety of image-guided brachytherapy employing a modified open high-field MR system.

METHODS

This is a follow-up study of a development project enabling technologies for interventional use of 1.0T open MRI. Modifications included coils and in-bore visualization, fluoroscopic sequences and user interfaces. We recruited 104 patients with 224 liver malignancies to receive MR-guided brachytherapy. Interventions were performed >20 min after Gd-EOB-DTPA. We recorded interventional parameters including the intervention time (from acquisition of the first scout until the final sequence for brachytherapy treatment planning). Two reviewers assessed MR-fluoroscopic images in comparison to plain CT as used in CT intervention, applying a rating scale of 1-10. Statistical analysis included Friedman and Kendall's W tests.

RESULTS

We employed freehand puncture with interactive dynamic imaging for navigation. Technical success rate was 218 complete ablations in 224 tumours (97%). The median intervention time was 61 min. We recorded no adverse events related to the use of MRI. No major complications occurred. The rate of minor complications was 4%. Local control at 3 months was 96%. Superiority of MR-fluoroscopic, Gd-EOB-DTPA-enhanced images over plain CT was highly significant (P < 0.001).

CONCLUSION

MR-guided brachytherapy employing open high-field MRI is feasible and safe.