Safety margin in irradiation of colorectal liver metastases: assessment of the control dose of micrometastases

Role of diffusion-weighted imaging in response prediction and evaluation after high dose rate brachytherapy in patients with colorectal liver metastases

BACKGROUND

The aim of the study was to assess the role of diffusion-weighted imaging (DWI) to evaluate treatment response in patients with liver metastases of colorectal cancer.

PATIENTS AND METHODS

In this retrospective, observational cohort study, we included 19 patients with 18 responding metastases (R-Mets; follow-up at least one year) and 11 non-responding metastases (NR-Mets; local tumor recurrence within one year) who were treated with high-dose-rate brachytherapy (HDR-BT) and underwent pre- and post-interventional MRI. DWI (qualitatively, mean apparent diffusion coefficient [ADCmean], ADCmin, intraindividual change of ADCmean and ADCmin) were evaluated and compared between pre-interventional MRI, first follow-up after 3 months and second follow-up at the time of the local tumor recurrence (in NR-Mets, mean: 284 ± 122 d) or after 12 months (in R-Mets, mean: 387+/-64 d). Sensitivity, specificity, positive predictive values (PPVs), and negative predictive values (NPVs) for detection of local tumor recurrence were calculated on second follow up, evaluating (1) DWI images only, and (2) DWI with Gd-enhanced T1-weighted images on hepatobiliary phase (contrast-enhanced [CE] T1-weight [T1w] hepatobiliary phase [hb]).

RESULTS

ADCmean significantly increased 3 months after HDR-BT in both groups (R-Mets: 1.48 ± 0.44 and NR-Mets: 1.49 ± 0.19 x 10-3 mm2;/s, p < 0.0001 and p = 0.01), however, intraindividual change of ADCmean (175% vs.127%, p = 0.03) and ADCmin values (0.44 ± 0.24 to 0.82 ± 0.58 x 10-3 mm2/s) significantly increased only in R-Mets (p < 0.0001 and p < 0.001). ADCmin was significant higher in R-Mets compared to NR-Mets on first follow-up (p = 0.04). Sensitivity (1 vs. 0.72), specificity (0.94 vs. 0.72), PPV (0.91 vs. 0.61) and NPV (1 vs. 0.81) could be improved by combining DWI with CE T1w hb compared to DWI only.

CONCLUSIONS

DW-MRI seems to be helpful in the qualitative and quantitative evaluation of treatment response after HDR-BT of colorectal metastases in the liver.

Local tumor control of intermediate and advanced stage hepatocellular carcinoma after local ablative treatment with image-guided interstitial high-dose-rate brachytherapy: A subgroup analysis of 286 HCC nodules

PURPOSE

Image-guided interstitial high-dose-rate brachytherapy (iBT) has been demonstrated to offer high local tumor control rates (LTC) of >90% after local ablation of intermediate and advanced hepatocellular carcinoma (HCC; BCLC B and C). The purpose of this study was to show the efficacy of iBT stratified by subgroups and to identify clinical characteristics associated with superior local tumor control (LTC) based on a highly heterogenous patient population METHODS AND MATERIALS: A cumulative number of 286 HCC nodules in 107 patients were retrospectively analyzed. Clinical and imaging follow-ups were conducted every 3 months after treatment. Analyzed clinical factors were: etiology, presence of liver cirrhosis, radiographic features, lesion size, pretreatment, administered dose, presence of portal hypertension, portal vein thrombosis, and level of alpha-fetoprotein (AFP).

RESULTS

LTC rate was 88.8% for a median follow-up of 14.3 months (range 3-81 months; 95% CI: 85-92%). Median minimal enclosing tumor dose (D100) was 16.1 Gy (range 7.1-30.3 Gy; reference dose 15 Gy). Subgroup analysis showed significant fewer local recurrences for alcoholic liver disease (ALD)-related HCCs compared to those related to other causes of liver cirrhosis (nonalcoholic fatty liver disease, virus-related liver cirrhosis and other causes) (p = 0.015). LTC was significantly lower after prior surgical resection (p = 0.046). No significant variance was observed for the applied D100 in each group or for all other clinical factors tested.

CONCLUSIONS

IBT achieves high LTC rates across treated subgroups. However, further studies should particularly address the possible impact of underlying etiology on local recurrence with emphasis on a possible higher radiosensitivity of ALD-related HCCs.

Biopsy and Margins Optimize Outcomes after Thermal Ablation of Colorectal Liver Metastases

Simple Summary

Thermal ablation (TA) is a non-surgical treatment of cancer that has been used with success in the treatment of colorectal liver metastases (CLM). TA consists of burning the cancer and a rim of surrounding tissue (margin) with a special needle placed in the tumor under image guidance. Despite the technological evolution of TA, tumor progression/recurrence rates remain higher than expected. We present a method that combines tissue and imaging tests performed immediately after ablation to determine whether there is complete tumor destruction or remaining live cancer cells that can cause tumor progression/recurrence. This information can provide guidance for additional treatments for patients with evidence of residual cancer, i.e.,: additional TA at the same or subsequent sitting, or additional chemotherapy and short-interval imaging follow-up to detect recurrence. The presented method proposes a clinical practice paradigm change that can improve clinical outcomes in a large population of patients with CLM treated by TA.

Abstract

Background: Thermal ablation is a definitive local treatment for selected colorectal liver metastases (CLM) that can be ablated with adequate margins. A critical limitation has been local tumor progression (LTP). Methods: This prospective, single-group, phase 2 study enrolled patients with CLM < 5 cm in maximum diameter, at a tertiary cancer center between November 2009 and February 2019. Biopsy of the ablation zone center and margin was performed immediately after ablation. Viable tumor in tissue biopsy and ablation margins < 5 mm were assessed as predictors of 12-month LTP. Results: We enrolled 107 patients with 182 CLMs. Mean tumor size was 2.0 (range, 0.6–4.6) cm. Microwave ablation was used in 51% and radiofrequency ablation in 49% of tumors. The 12- and 24-month cumulative incidence of LTP was 22% (95% confidence interval [CI]: 17, 29) and 29% (95% CI: 23, 36), respectively. LTP at 12 months was 7% (95% CI: 3, 14) for the biopsy tumor-negative ablation zone with margins ≥ 5 mm vs. 63% (95% CI: 35, 85) for the biopsy-positive ablation zone with margins < 5 mm (p < 0.001). Conclusions: Biopsy-proven complete tumor ablation with margins of at least 5 mm achieves optimal local tumor control for CLM, regardless of the ablation modality used.

Feasibility and Safety of CT-Guided High-Dose-Rate Brachytherapy Combined with Transarterial Chemoembolization Using Irinotecan-Loaded Microspheres for the Treatment of Large, Unresectable Colorectal Liver Metastases

PURPOSE

To evaluate feasibility and safety of combined irinotecan chemoembolization and CT-guided high-dose-rate brachytherapy (HDRBT) in patients with unresectable colorectal liver metastases > 3 cm in diameter.

MATERIALS AND METHODS

This prospective study included 23 patients (age, 70 y ± 11.3; 16 men) with 47 liver metastases (size, 62 mm ± 18.7). Catheter-related adverse events were reported per Society of Interventional Radiology classification, and treatment toxicities were reported per Common Terminology Criteria for Adverse Events. Liver-related blood values were analyzed by Wilcoxon test, with P < .05 as significant. Time to local tumor progression, progression-free survival (PFS), and overall survival (OS) were estimated by Kaplan-Meier method.

RESULTS

No catheter-related major or minor complications were recorded. Significant differences vs baseline levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT; both P < .001), γ-glutamyltransferase (GGT; P = .013), and hemoglobin (P = .014) were recorded. After therapy, 11 of 23 patients (47.8%) presented with new grade I/II toxicities (bilirubin, n = 3 [13%]; AST, n = 16 [70%]; ALT, n = 18 [78%]; ALP, n = 12 [52%] and hemoglobin, n = 15 [65%]). Moreover, grade III/IV toxicities developed in 10 (43.5%; 1 grade IV): AST, n = 6 (26%), grade III, n = 5; grade IV, n = 1; ALT, n = 3 (13%); GGT, n = 7 (30%); and hemoglobin, n = 1 (4%). However, all new toxicities resolved within 3 months after therapy without additional treatment. Median local tumor control, PFS, and OS were 6, 4, and 8 months, respectively.

CONCLUSIONS

Combined irinotecan chemoembolization and CT-guided HDRBT is safe and shows a low incidence of toxicities, which were self-resolving.

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.

Application of tolerance limits to the characterization of image registration performance

Deformable image registration is used increasingly in image-guided interventions and other applications. However, validation and characterization of registration performance remain areas that require further study. We propose an analysis methodology for deriving tolerance limits on the initial conditions for deformable registration that reliably lead to a successful registration. This approach results in a concise summary of the probability of registration failure, while accounting for the variability in the test data. The (β, γ) tolerance limit can be interpreted as a value of the input parameter that leads to successful registration outcome in at least 100β% of cases with the 100γ% confidence. The utility of the methodology is illustrated by summarizing the performance of a deformable registration algorithm evaluated in three different experimental setups of increasing complexity. Our examples are based on clinical data collected during MRI-guided prostate biopsy registered using publicly available deformable registration tool. The results indicate that the proposed methodology can be used to generate concise graphical summaries of the experiments, as well as a probabilistic estimate of the registration outcome for a future sample. Its use may facilitate improved objective assessment, comparison and retrospective stress-testing of deformable.

Detection of liver micrometastases from colorectal origin by perfusion CT in a rat model

BACKGROUND

Some patients with colorectal carcinoma have liver metastases (LMs) which cannot be detected by conventional imaging. This study aimed to assess whether hepatic perfusion changes induced by micrometastases can be detected by perfusion computed tomography (CT).

METHODS

LMs were produced in rats by injecting carcinoma cells into the portal vein. Perfusion CT was performed at microscopic (day 10), interval (day 17), and macroscopic stage (day 34). Perfusion parameters were computed using a dual-input one-compartmental model.

RESULTS

Micro and macro LMs presented a mean diameter of 0.5 and 2.6 mm, respectively. Compared to controls, LMs at interval (1.1 mm) and macroscopic stage induced significant perfusion changes: a decrease of 42% (P=0.004) and 41% (P=0.029) in hepatic transit time and an increase of 292% (P=0.073) and 240% (P=0.001) in portal delay, respectively.

CONCLUSIONS

LMs with a mean diameter between 1.1 and 2.6 mm induced significant hepatic perfusion changes, detected by CT. Such detection may help to select patients and propose chemotherapy at the time of primary tumor resection.

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.

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.

Value of diffusion weighted MR imaging as an early surrogate parameter for evaluation of tumor response to high-dose-rate brachytherapy of colorectal liver metastases

Background

To assess the value of diffusion weighted imaging (DWI) as an early surrogate parameter for treatment response of colorectal liver metastases to image-guided single-fraction ¹⁹²Ir-high-dose-rate brachytherapy (HDR-BT).

Methods

Thirty patients with a total of 43 metastases underwent CT- or MRI-guided HDR-BT. In 13 of these patients a total of 15 additional lesions were identified, which were not treated at the initial session and served for comparison. Magnetic resonance imaging (MRI) including breathhold echoplanar DWI sequences was performed prior to therapy (baseline MRI), 2 days after HDR-BT (early MRI) as well as after 3 months (follow-up MRI). Tumor volume (TV) and intratumoral apparent diffusion coefficient (ADC) were measured independently by two radiologists. Statistical analysis was performed using univariate comparison, ANOVA and paired t test as well as Pearson's correlation.

Results

At early MRI no changes of TV and ADC were found for non-treated colorectal liver metastases. In contrast, mean TV of liver lesions treated with HDR-BT increased by 8.8% (p = 0.054) while mean tumor ADC decreased significantly by 11.4% (p < 0.001). At follow-up MRI mean TV of non-treated metastases increased by 50.8% (p = 0.027) without significant change of mean ADC values. In contrast, mean TV of treated lesions decreased by 47.0% (p = 0.026) while the mean ADC increased inversely by 28.6% compared to baseline values (p < 0.001; Pearson's correlation coefficient of r = -0.257; p < 0.001).

Conclusions

DWI is a promising imaging biomarker for early prediction of tumor response in patients with colorectal liver metastases treated with HDR-BT, yet the optimal interval between therapy and early follow-up needs to be elucidated.

Comparison of macroscopic pathology measurements with magnetic resonance imaging and assessment of microscopic pathology extension for colorectal liver metastases

PURPOSE

To compare pathology macroscopic tumor dimensions with magnetic resonance imaging (MRI) measurements and to establish the microscopic tumor extension of colorectal liver metastases.

METHODS AND MATERIALS

In a prospective pilot study we included patients with colorectal liver metastases planned for surgery and eligible for MRI. A liver MRI was performed within 48 hours before surgery. Directly after surgery, an MRI of the specimen was acquired to measure the degree of tumor shrinkage. The specimen was fixed in formalin for 48 hours, and another MRI was performed to assess the specimen/tumor shrinkage. All MRI sequences were imported into our radiotherapy treatment planning system, where the tumor and the specimen were delineated. For the macroscopic pathology analyses, photographs of the sliced specimens were used to delineate and reconstruct the tumor and the specimen volumes. Microscopic pathology analyses were conducted to assess the infiltration depth of tumor cell nests.

RESULTS

Between February 2009 and January 2010 we included 13 patients for analysis with 21 colorectal liver metastases. Specimen and tumor shrinkage after resection and fixation was negligible. The best tumor volume correlations between MRI and pathology were found for T1-weighted (w) echo gradient sequence (r(s) = 0.99, slope = 1.06), and the T2-w fast spin echo (FSE) single-shot sequence (r(s) = 0.99, slope = 1.08), followed by the T2-w FSE fat saturation sequence (r(s) = 0.99, slope = 1.23), and the T1-w gadolinium-enhanced sequence (r(s) = 0.98, slope = 1.24). We observed 39 tumor cell nests beyond the tumor border in 12 metastases. Microscopic extension was found between 0.2 and 10 mm from the main tumor, with 90% of the cases within 6 mm.

CONCLUSIONS

MRI tumor dimensions showed a good agreement with the macroscopic pathology suggesting that MRI can be used for accurate tumor delineation. However, microscopic extensions found beyond the tumor border indicate that caution is needed in selecting appropriate tumor margins.