Stereotactic body radiation therapy for liver metastases

Feasibility of Biology-guided Radiotherapy (BgRT) Targeting Fluorodeoxyglucose (FDG) avid liver metastases

INTRODUCTION

Biology-guided radiotherapy (BgRT) is a novel radiation delivery approach utilizing fluorodeoxyglucose (FDG) activity on positron emission tomography (PET) imaging performed in real-time to track and direct RT. Our institution recently acquired the RefleXion X1 BgRT system and sought to assess the feasibility of targeting metastatic sites in various organs, including the liver. However, in order for BgRT to function appropriate, adequate contrast in FDG activity between the tumor and the background tissue, referred to as the normalized SUV (NSUV), is necessary for optimal functioning of BgRT.

METHODS

We reviewed the charts of 50 lung adenocarcinoma patients with liver metastases. The following variables were collected: SUVmax and SUVmean for each liver metastasis, SUVmean and SUVmax at 5 and 10 mm radially from the lesion, and NSUV at 5 mm and 10 mm (SUVmax of the liver metastasis divided by SUV mean at 5 mm at 10 mm respectively).

RESULTS

82 measurable liver metastases were included in the final analysis. The average SUVbackground of liver was 2.26 (95% confidence interval [CI] 2.17-2.35); average SUVmean for liver metastases was 5.31 (95% CI 4.87-5.75), and average SUVmax of liver metastases was 9.19 (95% CI 7.59-10.78). The average SUVmean at 5 mm and 10 mm radially from each lesion were 3.08 (95% CI 3.00-2.16) and 2.60 (95% CI 2.52-2.68), respectively. The mean NSUV at 5 mm and 10 mm were 3.13 (95% CI 2.53-3.73) and 3.69 (95% CI 3.00-4.41) respectively. Furthermore, 90% of lesions had NSUV greater than 1.45 at 5 mm and greater than 1.77 at 10 mm.

CONCLUSIONS

This is the first study to comprehensively characterize FDG contrast between the liver tumor and background, referred to as NSUV. Due to the high background SUV normally found in the liver, this work will be valuable for guiding optimization of BgRT for treating liver metastases in the future using the RefleXion® X1 and potentially other similar BgRT platforms.

Clinical and Dosimetric Impact of 2D kV Motion Monitoring and Intervention in Liver Stereotactic Body Radiation Therapy

Purpose

Positional errors resulting from motion are a principal challenge across all disease sites in radiation therapy. This is particularly pertinent when treating lesions in the liver with stereotactic body radiation therapy (SBRT). To achieve dose escalation and margin reduction for liver SBRT, kV real-time imaging interventions may serve as a potential solution. In this study, we report results of a retrospective cohort of liver patients treated using real-time 2D kV-image guidance SBRT with emphasis on the impact of (1) clinical workflow, (2) treatment accuracy, and (3) tumor dose.

Methods and Materials

Data from 33 patients treated with 41 courses of liver SBRT were analyzed. During treatment, planar kV images orthogonal to the treatment beam were acquired to determine treatment interventions, namely treatment pauses (ie, adequacy of gating thresholds) or treatment shifts. Patients were shifted if internal markers were >3 mm, corresponding to the PTV margin used, from the expected reference condition. The frequency, duration, and nature of treatment interventions (ie, pause vs shift) were recorded, and the dosimetric impact associated with treatment shifts was estimated using a machine learning dosimetric model.

Results

Of all fractions delivered, 39% required intervention, which took on average 1.9 ± 1.6 minutes and occurred more frequently in treatments lasting longer than 7 minutes. The median realignment shift was 5.7 mm in size, and the effect of these shifts on minimum tumor dose in simulated clinical scenarios ranged from 0% to 50% of prescription dose per fraction.

Conclusion

Real-time kV-based imaging interventions for liver SBRT minimally affect clinical workflow and dosimetrically benefit patients. This potential solution for addressing positional errors from motion addresses concerns about target accuracy and may enable safe dose escalation and margin reduction in the context of liver SBRT.

Multimodal Management of Colorectal Liver Metastases: State of the Art

Liver is the most common site of colorectal cancer (CRC) metastases. Treatment of CRC liver metastases (CRLM) includes different strategies, prevalently based on the clinical and oncological intent. Valid approaches in liver-limited or liver-prevalent disease include surgery, percutaneous ablative procedures (radiofrequency ablation, microwave ablation), intra-arterial perfusional techniques (chemo-embolization, radio-embolization) as well as stereotactic radiotherapy. Systemic treatments, including chemotherapy, immunotherapy and other biological agents, are the only options for patients with no chance of locoregional approaches. The use of chemotherapy in other settings, such as neoadjuvant, adjuvant or conversion therapy of CRLM, is commonly accepted in the clinical practice, although data from several clinical trials have been mostly inconclusive. The optimal integration of all these strategies, when applicable and clinically indicated, should be ever considered in patients affected by CRLM based on clinical evidence and multidisciplinary experience. Here we revised in detail all the possible therapeutic approaches of CRLM focusing on the current evidences, the studies still in progress and the often contradictory data.

Comparison of capecitabine-based regimens with platinum-based regimens in Chinese triple-negative breast cancer patients with liver metastasis

Background

Capecitabine-based chemotherapy (CBC) presents potential value in patients with liver metastasis; platinum-based chemotherapy (PBC) has shown promising benefit in patients with triple-negative breast cancer (TNBC). For TNBC patients with liver metastasis, which treatment strategy is better remains to be further studied. The aim of this study was to report the first real-world data evaluating the efficacy and safety of PBC versus CBC in the first-line treatment in Chinese TNBC patients with liver metastasis.

Methods

TNBC patients with liver metastasis pretreated with anthracyclines/taxanes in 4 institutions of China between January 2010 and December 2019 were included. Objective response rate (ORR), overall survival, treatment pattern, and toxicity profile were assessed between PBC and CBC groups.

Results

A total of 59 TNBC patients with liver metastasis were identified. Among these, 33 were treated with PBC and 26 were treated with CBC. The ORR was higher in the CBC group than in the PBC group (57.7% versus 30.3%, P=0.035). Median overall survival was also greatly improved (19.2 versus 14.4 months, P=0.041). Docetaxel/cisplatin was more likely to be used for PBC, and paclitaxel/capecitabine was the main regimen for CBC. Multivariable Cox regression analysis indicated that CBC was an independent predictor for overall survival after adjustment for baseline factors including age, tumor size, nodal status, prior anthracyclines/taxanes use, and tumor grade (odds ratio =0.51; 95% confidence interval, 0.27-0.98; P=0.042). Adverse events were not different except gastrointestinal tract toxicities, hand-foot syndrome and hematologic toxicity.

Conclusions

For TNBC patients with liver metastasis, capecitabin-based chemotherapy might be more suitable than the platinum-based regimen in the first-line treatment, as measured by objective response rate and overall survival. Further large-scale studies are warranted.

Slice-stacking T2-weighted MRI for fast determination of internal target volume for liver tumor

Background

To investigate the feasibility of generating maximum intensity projection (MIP) images to determine internal target volume (ITV) using slice-stacking MRI (SS-MRI) technique.

Methods

Slice-stacking is a technique which applies a multi-slice MRI acquisition to generate a 3D MIP for ITV contouring, without reconstructing 4D-MRI. 4D digital extended cardiac-torso (XCAT) phantom was used to generate MIP images with sequential 2D HASTE sequence, with different tumor diameters (10, 30 and 50 mm) and with simulated regular and irregular (patient) breathing motions. A reference MIP was generated using all acquisition images. Consecutive repetitions were then used to generate MIP to analyze the relationship between Dice's similarity coefficient (DSC) and the number of repetitions, and the relationship between the relative ITV volume difference and the number of repetitions. Images from XCAT phantom and from three hepatic carcinoma patients were collected in this study to demonstrate the feasibility of this technique.

Results

For both regular and irregular breathing motion, the average DSC of ITV is >0.94 and the average relative ITV volume difference is <10% (approximately 0.15 cm³) when using 5 repeated scanning images to reconstruct MIP for tumor diameter of 10 mm. As tumor diameter increases, the DSC of ITV is >0.97 and the relative ITV volume difference is <5% for regular breathing motion, and the DSC of ITV is >0.97 and the relative ITV volume difference is <5.5% for irregular breathing motion when using 5 repeated scanning images to reconstruct MIP. In patient image study, the mean relative ITV volume difference is <3% and the mean DSC is 0.99 when using 5 repeated scanning images to reconstruct MIP.

Conclusions

The number of scans required to generate tumor ITV for slice-stacking method (5-7 repetition) is 3-4 times less than that of 4D-MRI (15-20 repetitions). It is feasible to generate a fast clinically acceptable ITV using slice-stacking method with sequential 2D MR images.

Radiation Therapy in Adult Soft Tissue Sarcoma-Current Knowledge and Future Directions: A Review and Expert Opinion

Simple Summary

Radiation therapy (RT) is an integral part of the treatment of adult soft-tissue sarcomas (STS). Although mainly used as perioperative therapy to increase local control in resectable STS with high risk features, it also plays an increasing role in the treatment of non-resectable primary tumors, oligometastatic situations, or for palliation. This review summarizes the current evidence for RT in adult STS including typical indications, outcomes, side effects, dose and fractionation regimens, and target volume definitions based on tumor localization and risk factors. It covers the different overall treatment approaches including RT either as part of a multimodal treatment strategy or as a sole treatment and is accompanied by a summary on ongoing clinical research pointing at future directions of RT in STS.

Abstract

Radiation therapy (RT) is an integral part of the treatment of adult soft-tissue sarcomas (STS). Although mainly used as perioperative therapy to increase local control in resectable STS with high risk features, it also plays an increasing role in the treatment of non-resectable primary tumors, oligometastatic situations, or for palliation. Modern radiation techniques, like intensity-modulated, image-guided, or stereotactic body RT, as well as special applications like intraoperative RT, brachytherapy, or particle therapy, have widened the therapeutic window allowing either dose escalation with improved efficacy or reduction of side effects with improved functional outcome. This review summarizes the current evidence for RT in adult STS including typical indications, outcomes, side effects, dose and fractionation regimens, and target volume definitions based on tumor localization and risk factors. It covers the different overall treatment approaches including RT either as part of a multimodal treatment strategy or as a sole treatment, namely its use as an adjunct to surgery in resectable STS (perioperative RT), as a primary treatment in non-resectable tumors (definitive RT), as a local treatment modality in oligometastatic disease or as palliative therapy. Due to the known differences in clinical course, general treatment options and, consequently, outcome depending on lesion localization, the main part of perioperative RT is divided into three sections according to body site (extremity/trunk wall, retroperitoneal, and head and neck STS) including the discussion of special applications of radiation techniques specifically amenable to this region. The review of the current evidence is accompanied by a summary on ongoing clinical research pointing at future directions of RT in STS.

Stereotactic Body Radiation Therapy in Oligometastatic Uterine Cancer: Clinical Outcomes and Toxicity

We report on clinical outcomes in patients with oligometastatic uterine cancer treated with stereotactic body radiation therapy (SBRT). Twenty-seven patients with 61 lesions were treated with SBRT. Median follow-up was 16.9 months. Local control was achieved in 49/61 (80.3%) lesions. One-year local-progression-free survival and overall survival were 75.9% and 65.4%. Lesions with favorable response were smaller than lesions with unfavorable response (p = .007). Liver lesions were less likely to achieve favorable response (p = .0128). There were no grade 3 or 4 events. Treatment with SBRT can provide excellent local control in oligometastatic uterine cancer with minimal toxicity.

Dosimetric Validation of Digital Megavolt Imager for Flattening Filter Free Beams in the Pre-Treatment Quality Assurance of Stereotactic Body Radiation Therapy for Liver Metastases

Aim:

The aim is to evaluate the use of digital megavolt imager (DMI) aS1200 in portal dosimetry with flattening filter free (FFF) beams.

Materials and Methods:

Dosimetric properties of DMI is characterized at 6MV FFF beams for signal saturation, dose linearity, dependency on dose-rate and source-detector distance (SDD), signal lag (ghosting), and back scatter. Portal dosimetry is done for twenty volumetric modulated arc therapy (VMAT) based stereotactic body radiotherapy (SBRT) plans for the treatment of liver metastases and the results are compared with repeated measurements of Octavius 4D.

Results:

The detector signal to monitor unit (MU) ratio drops drastically below 25MU. The detector linearity with dose is within 1% and no evidence of signal saturation as such. The aS1200 response variation across various dose rates and SDD is <0.4% and <0.2% respectively. The effect of ghosting increased distinctly at higher dose rate but however it is negligible (0.1%). The impact of back scatter is <0.3% because of additional shielding provided at the back of the detector. The portal dosimetry results of SBRT QA plans evaluated at the gamma criteria of 2mm/2% (DTA/DD) both under global and local mode analysis has shown an average gamma passing rate of area gamma (<1) 97.9±0.8% and 96.4±0.9%. The SBRT QA results observed in aS1200 are inline and consistent with Octavius 4D measured results.

Conclusion:

The characteristics of aS1200 evaluated at FFF beams have shown its potential ability as QA tool and can be used in SBRT QA for liver metastases with greater confidence.

Treatment Strategy for Distant Synchronous Metastatic Head and Neck Squamous Cell Carcinoma

PURPOSE OF REVIEW

Management of metastatic head and neck squamous cell cancers (HNSCC) can be challenging. This review gives an insight of current treatment options for patients with synchronous metastatic HNSCC and suggests a therapeutic algorithm.

RECENT FINDINGS

With the rise of novel therapeutic techniques and medications, many treatment options for both locoregional and distant metastatic disease have become available. The evolving paradigm of metastatic disease now integrates the concept of oligometastatic disease. On top of systemic treatments, patients with low metastatic burden can benefit from curative approaches such as local therapies (surgery, radiotherapy) directed to either primary tumour and distant metastasis. However, data integrating these considerations in the management of metastatic HNSCC is still lacking. Based on this algorithm, we can provide a tailored treatment to each patient with synchronous metastatic HNSCC, according to their age, general condition and metastatic burden.

Local Treatment of Breast Cancer Liver Metastasis

Breast cancer represents a leading cause of death worldwide. Despite the advances in systemic therapies, the prognosis for patients with breast cancer liver metastasis (BCLM) remains poor. Especially in case of failure or cessation of systemic treatments, surgical resection for BCLMs has been considered as the treatment standard despite a lack of robust evidence of benefit. However, due to the extent and location of disease and physical condition, the number of patients with BCLM who are eligible for surgery is limited. Palliative locoregional treatments of liver metastases (LM) include transarterial embolization (TAE), transarterial chemoembolization (TACE), and selective internal radiotherapy (SIRT). Percutaneous thermal ablation methods, such as radiofrequency ablation (RFA) and microwave ablation (MWA), are considered potentially curative local treatment options. They are less invasive, less expensive and have fewer contraindications and complication rates than surgery. Because conventional ultrasound- and computed tomography-guided single-probe thermal ablation is limited by tumor size, multi-probe stereotactic radiofrequency ablation (SRFA) with intraoperative image fusion for immediate, reliable judgment has been developed in order to treat large and multiple tumors within one session. This review focuses on the different minimally invasive local and locoregional treatment options for BCLM and attempts to describe their current and future role in the multidisciplinary treatment setting.

Multidisciplinary management of liver metastases in patients with colorectal cancer: a consensus of SEOM, AEC, SEOR, SERVEI, and SEMNIM

Colorectal cancer (CRC) has the second-highest tumor incidence and is a leading cause of death by cancer. Nearly 20% of patients with CRC will have metastases at the time of diagnosis, and more than 50% of patients with CRC develop metastatic disease during the course of their disease. A group of experts from the Spanish Society of Medical Oncology, the Spanish Association of Surgeons, the Spanish Society of Radiation Oncology, the Spanish Society of Vascular and Interventional Radiology, and the Spanish Society of Nuclear Medicine and Molecular Imaging met to discuss and provide a multidisciplinary consensus on the management of liver metastases in patients with CRC. The group defined the different scenarios in which the disease can present: fit or unfit patients with resectable liver metastases, patients with potential resectable liver metastases, and patients with unresectable liver metastases. Within each scenario, the different strategies and therapeutic approaches are discussed.

Single community-based institutional series of stereotactic body radiation therapy (SBRT) for treatment of liver metastases

Background

Stereotactic body radiation therapy (SBRT) is a safe and effective option for treatment of liver metastases. However, existing data are mostly reported by high-volume centers. There have been reports that advanced radiotherapy techniques performed at low-volume centers result in inferior outcomes. Our goal was to assess the implementation of SBRT for the treatment of liver metastases at a low-volume center by studying the efficacy and toxicity of this technology through retrospective database review at a single, community-based institution.

Methods

We performed an IRB approved patient registry study. Patients had a median age of 65, KPS of at least 70 (median 90) and primary tumor controlled. All patients underwent fiducial marker placement under CT-guidance 1-2 weeks prior to planning scans. Gross tumor volume (GTV) was delineated using contrast enhanced CT scans, as well as fusion with PET and/or MRI scans. GTV was expanded by 5 mm to create the planning target volume (PTV). Treatment was delivered by image guided stereotactic robotic radiosurgery with respiratory motion tracking. Lesions were treated with 3 fractions to a median total dose of 54 Gy. Overall survival, progression-free survival (PFS) and local failure-free survival were estimated using the Kaplan-Meier method. Log-rank statistic was used to compare local control based on GTV volume.

Results

Between 2006 and 2016, 42 consecutively treated patients with 81 metastatic liver lesions were treated with SBRT. Median follow-up was 25 months. Major primary tumor sites were colon (n=18) and lung (n=7). Synchronous extrahepatic disease was present in 15% of the treated lesions and 46% had prior local treatment of liver metastases. The number of lesions treated concurrently ranged from 1 to 4. Lesions had a median maximum diameter of 2.5 cm (range, 0.5-9.5 cm), and a mean volume of 53 cc (range, 0.5-363.0 cc). Kaplan-Meier estimated 1- and 2-year overall survival was 72% and 62%. Estimated 1- and 2-year progression free survival was 32% and 23%. Estimated 1- and 2-year local control was 86% and 80%. Two-year local control was worse for lesions >50 cc compared to lesions ≤50 cc (62% vs. 84%, P=0.04). Toxicity occurred in 26% of treatment courses and included grade 1 (n=12) and grade 2 toxicity (n=3).

Conclusions

These results are comparable to available published data regarding the safety and efficacy of liver metastasis SBRT on trial at high volume institutions. Our findings, therefore, demonstrate the successful implementation of a liver metastasis SBRT program in the low-volume, community-hospital setting. These findings suggest that low-volume and high-volume centers are both options for liver metastasis SBRT.

Evaluation of dosimetric uncertainty caused by MR geometric distortion in MRI-based liver SBRT treatment planning

PURPOSE

MRI-based treatment planning is a promising technique for liver stereotactic-body radiation therapy (SBRT) treatment planning to improve target volume delineation and reduce radiation dose to normal tissues. MR geometric distortion, however, is a source of potential error in MRI-based treatment planning. The aim of this study is to investigate dosimetric uncertainties caused by MRI geometric distortion in MRI-based treatment planning for liver SBRT.

MATERIALS AND METHODS

The study was conducted using computer simulations. 3D MR geometric distortion was simulated using measured data in the literature. Planning MR images with distortions were generated by integrating the simulated 3D MR geometric distortion onto planning CT images. MRI-based treatment plans were then generated on the planning MR images with two dose calculation methods: (1) using original CT numbers; and (2) using organ-specific assigned CT numbers. Dosimetric uncertainties of various dose-volume-histogram parameters were determined as their differences between the simulated MRI-based plans and the original clinical CT-based plans for five liver SBRT cases.

RESULTS

The average simulated distortion for the five liver SBRT cases was 2.77 mm. In the case of using original CT numbers for dose calculation, the average dose uncertainties for target volumes and critical structures were <0.5 Gy, and the average target volume percentage at prescription dose uncertainties was 0.97%. In the case of using assigned CT numbers, the average dose uncertainties for target volumes and critical structures were <1.0 Gy, and the average target volume percentage at prescription dose uncertainties was 2.02%.

CONCLUSIONS

Dosimetric uncertainties caused by MR geometric distortion in MRI-based liver SBRT treatment planning was generally small (<1 Gy) when the distortion is 3 mm.

Literature Review of Current Management of Colorectal Liver Metastasis

Colorectal cancer is a leading cause of cancer mortality in the United States, and metastasis to the liver is a frequent sequela. Currently, surgical resection is the best option for curative treatment and/or long-term survival after colorectal liver metastasis (CRLM), but unfortunately, not all patients are surgical candidates. Alternative and adjunct therapies commonly used in the treatment of CRLM include chemotherapy, biologic therapy, radio-embolization, and radiofrequency ablation. The aim of this review was to report the various treatment modalities and outcomes currently used in the treatment of CRLM.

Selection and clinical significance of individualized treatment for metastatic liver cancer

The liver is one of the most common target organs for metastasis of malignant tumors, with a metastasis rate of 11.1%. Approximately 40% of patients with malignant tumors will develop liver metastasis. Metastatic liver cancer not only exhibits individualized difference in the origin of primary tumor, tumor gene, and biological behavior, but also varies in the stage of progression, anatomic characteristics, organ function, and complications. In view of the different sources and pathways of metastatic tumors, the treatment of metastatic liver cancer involves two aspects: primary tumor and liver metastasis. How to choose surgery, local ablation, chemotherapy, molecular targeted drugs, endocrine therapy, biological and immune therapy, and radiotherapy as well as the treatment opportunity rationally is the key to the treatment of metastatic liver cancer. Advanced imaging techniques are used to determine the size, number, location, and blood supply of metastatic liver cancer, so as to provide an objective basis for making an accurate individualized treatment plan for metastatic liver cancer. At present, any single therapy for metastatic liver cancer has its own indications. If a metastatic liver tumor cannot be resected radically , the use of a single therapy is difficult to cure or control the progression of the tumor. In this case, it is necessary to combine two or more than two kinds of treatment methods to achieve the synergistic effect. According to the specific condition of patients with metastatic liver cancer, the individual characteristics of the patients should be analyzed by experienced clinicians to formulate an individualized treatment plan in accordance with the principles of evidence-based medicine, so as to make the patients benefit most from the plan, improve the quality of life, and prolong the survival time.

Hepatobiliary scintigraphy allows the evaluation of short-term functional toxicity of liver stereotactic body radiotherapy: Results of a pilot study

PURPOSE

To study the potential of (99m)Tc-Mebrofenin hepatobiliary scintigraphy (HBS) in identifying the short-term variations of liver function after stereotactic body radiotherapy (SBRT) for liver cancers.

MATERIAL AND METHODS

We treated with SBRT 3 patients (pts) affected by a cholangiocarcinoma and 3 patient presenting liver metastases (3x15 Gy, 4 pts; 5x8 Gy, 1 pt; 6x5 Gy, 1 pt). All patients received HBS before and 3 months after SBRT, which were co-registered with the simulation CT-scan. Structures corresponding to isodoses from 10-90 Gy were created, with intervals of 10 Gy. Finally, the variations of the mean activity (MBq) in each isodose structure have been calculated. Then, a linear regression analysis was performed.

RESULTS

We showed a linear reduction of the activity, significantly related to the delivered dose (p<0.01), and a reduction of the perfusion of 0.78% for each delivered Gy. The linear equation has predictive value of the loss of the function of 96% (R2 = 0.9605).

CONCLUSIONS

HBS could improve treatment plans for liver SBRT, by allowing the identification of the liver function variations after SBRT and, potentially, the prediction of remnant liver function after SBRT. These preliminary results should be confirmed on long-term prospective data and larger population.

A simulation study to assess the potential impact of developing normal tissue complication probability models with accumulated dose

PURPOSE

This study aimed to analyze the potential clinical impact of the differences between planned and accumulated doses on the development and use of normal tissue complication probability (NTCP) models.

METHODS AND MATERIALS

Thirty patients who were previously treated with stereotactic body radiation therapy for liver cancer and for whom the accumulated dose was computed were assessed retrospectively. The linear quadratic equivalent dose at 2 Gy per fraction and generalized equivalent uniform dose were calculated for planned and accumulated doses. Stomach and duodenal Lyman-Kutcher-Burman NTCP models (α/β = 2.5; n = .09) were developed on the basis of planned and accumulated generalized equivalent uniform doses and the differences between the models assessed. In addition, the error in determining the probability of toxicity on the basis of the planned dose was evaluated by comparing planned doses in the NTCP model that were created from accumulated doses.

RESULTS

The standard, planned-dose NTCP model overestimates toxicity risk for both the duodenal and stomach models at doses that are below approximately 20 Gy (6 fractions) and underestimates toxicity risk for doses above approximately 20 Gy (6 fractions). Building NTCP models with accumulated rather than planned doses changes the predicted risk by up to 16% (mean: 6%; standard deviation: 7%) for duodenal toxicity and 6% (mean: 2%; standard deviation: 2%) for stomach toxicity. For a protocol that plans a 10% iso-toxicity risk to the duodenum, a 15.7 Gy (6 fractions) maximum dose constraint would be necessary when using standard NTCP models on the basis of a planned dose and a 17.6 Gy (6 fractions) maximum dose would be allowed when using NTCP models on the basis of accumulated doses.

CONCLUSIONS

Assuming that accumulated dose is a more accurate representation of the true delivered dose than the planned dose, this simulation study indicates the need for prospective clinical trials to evaluate the impact of building NTCP models on the basis of accumulated doses.

Development of deep neural network for individualized hepatobiliary toxicity prediction after liver SBRT

BACKGROUND

Accurate prediction of radiation toxicity of healthy organs-at-risks (OARs) critically determines the radiation therapy (RT) success. The existing dose-volume histogram-based metric may grossly under/overestimate the therapeutic toxicity after 27% in liver RT and 50% in head-and-neck RT. We propose the novel paradigm for toxicity prediction by leveraging the enormous potential of deep learning and go beyond the existing dose/volume histograms.

EXPERIMENTAL DESIGN

We employed a database of 125 liver stereotactic body RT (SBRT) cases with follow-up data to train deep learning-based toxicity predictor. Convolutional neural networks (CNNs) were applied to discover the consistent patterns in 3D dose plans associated with toxicities. To enhance the predicting power, we first pretrain the CNNs with transfer learning from 3D CT images of 2644 human organs. CNNs were then trained on liver SBRT cases. Furthermore, nondosimetric pretreatment features, such as patients' demographics, underlying liver diseases, liver-directed therapies, were inputted into the fully connected neural network for more comprehensive prediction. The saliency maps of CNNs were used to estimate the toxicity risks associated with irradiation of anatomical regions of specific OARs. In addition, we applied machine learning solutions to map numerical pretreatment features with hepatobiliary toxicity manifestation.

RESULTS

Among 125 liver SBRT patients, 58 were treated for liver metastases, 36 for hepatocellular carcinoma, 27 for cholangiocarcinoma, and 4 for other histologies. We observed that CNN we able to achieve accurate hepatobiliary toxicity prediction with the AUC of 0.79, whereas combining CNN for 3D dose plan analysis and fully connected neural networks for numerical feature analysis resulted in AUC of 0.85. Deep learning produces almost two times fewer false-positive toxicity predictions in comparison to DVH-based predictions, when the number of false negatives, i.e., missed toxicities, was minimized. The CNN saliency maps automatically estimated the toxicity risks for portal vein (PV) regions. We discovered that irradiation of the proximal portal vein is associated with two times higher toxicity risks (risk score: 0.66) that irradiation of the left portal vein (risk score: 0.31).

CONCLUSIONS

The framework offers clinically accurate tools for hepatobiliary toxicity prediction and automatic identification of anatomical regions that are critical to spare during SBRT.

A Multi-Institutional Experience of MR-Guided Liver Stereotactic Body Radiation Therapy

Purpose

Daily magnetic resonance (MR)–guided radiation has the potential to improve stereotactic body radiation therapy (SBRT) for tumors of the liver. Magnetic resonance imaging (MRI) introduces unique variables that are untested clinically: electron return effect, MRI geometric distortion, MRI to radiation therapy isocenter uncertainty, multileaf collimator position error, and uncertainties with voxel size and tracking. All could lead to increased toxicity and/or local recurrences with SBRT. In this multi-institutional study, we hypothesized that direct visualization provided by MR guidance could allow the use of small treatment volumes to spare normal tissues while maintaining clinical outcomes despite the aforementioned uncertainties in MR-guided treatment.

Methods and materials

Patients with primary liver tumors or metastatic lesions treated with MR-guided liver SBRT were reviewed at 3 institutions. Toxicity was assessed using National Cancer Institute Common Terminology Criteria for Adverse Events Version 4. Freedom from local progression (FFLP) and overall survival were analyzed with the Kaplan-Meier method and χ² test.

Results

The study population consisted of 26 patients: 6 hepatocellular carcinomas, 2 cholangiocarcinomas, and 18 metastatic liver lesions (44% colorectal metastasis). The median follow-up was 21.2 months. The median dose delivered was 50 Gy at 10 Gy/fraction. No grade 4 or greater gastrointestinal toxicities were observed after treatment. The 1-year and 2-year overall survival in this cohort is 69% and 60%, respectively. At the median follow-up, FFLP for this cohort was 80.4%. FFLP for patients with hepatocellular carcinomas, colorectal metastasis, and all other lesions were 100%, 75%, and 83%, respectively.

Conclusions

This study describes the first clinical outcomes of MR-guided liver SBRT. Treatment was well tolerated by patients with excellent local control. This study lays the foundation for future dose escalation and adaptive treatment for liver-based primary malignancies and/or metastatic disease.

Treatment of Liver Metastases Using an Internal Target Volume Method for Stereotactic Body Radiotherapy

The prognosis of patients with metastatic cancers has improved in the past decades due to effective chemotherapy and oligometastatic surgery. For inoperable patients, local ablation therapies, such as stereotactic body radiotherapy (SBRT), can provide effective local tumor control with minimal toxicity. Because of its high precision and accuracy, SBRT delivers a higher radiation dose per fraction, is more effective, and targets smaller irradiation volumes than does conventional radiotherapy. In addition, steep dose gradients from target lesions to surrounding normal tissues are achieved using SBRT; thus, SBRT provides more effective tumor control and exhibits fewer side effects than conventional radiotherapy. The use of SBRT is prevalent for treating intracranial lesions (known as stereotactic radiosurgery); however, it is now also used for treating spinal and adrenal metastases. Because of advancements in image-guided assistance and respiratory motion management, several studies have investigated the use of SBRT for treating lung or liver tumors, which move as a patient breathes. The results of these studies have suggested that SBRT favorably controls tumors in the case of moving lesions. Four-dimensional computed tomography (4D-CT) with an abdominal compressor (AC) is clinically convenient for effective respiratory motion management. Because this method is noninvasive and allows free breathing, its use reduces complications. Furthermore, patients consider this method convenient. Moreover, it is considered more efficient than other methods of respiratory motion management by physicians and therapists. The use of 4D-CT with an AC for treating pulmonary lesions has also been widely investigated, and the technique is gaining acceptance for treating hepatic lesions. However, the protocols for using 4D-CT with an AC for treating hepatic lesions are different from those used for treating pulmonary lesions. In this article, we describe a new protocol for SBRT with 4D-CT and an AC for treating liver metastases.

Quantitative analysis of respiration-induced motion of each liver segment with helical computed tomography and 4-dimensional computed tomography

Background

To analyze the respiratory-induced motion of each liver segment using helical computed tomography (helical CT) and 4-dimensional computed tomography (4DCT), and to establish the individual segment expansion margin of internal target volume (ITV) to facilitate target delineation of tumors in different liver segments.

Methods

Twenty patients who received radiotherapy with CT-simulation scanning of the whole liver in both helical CT and 10-phase-gated 4DCT were investigated, including 2 patients with esophagus cancer, 4 with lung cancer, 10 with breast cancer, 2 with liver cancer, 1 with thymoma, and 1 with gastric diffuse large B-cell lymphoma (DLBCL). For each patient, 9 representative points were drawn on the helical CT images of liver segments 1, 2, 3, 4a, 4b, 5, 6, 7, and 8, respectively, and adaptively deformed to 2 phases of the 4DCT images at the end of inspiration (phase 0 CT) and expiration (phase 50 CT) in the treatment planning system. Using the amplitude of each point between phase 0 CT and phase 50 CT, we established quantitative data for the respiration-induced motion of each liver segment in 3-dimensional directions. Moreover, using the amplitude between the original helical CT and both 4DCT images, we rendered the individual segment expansion margin of ITV for hepatic target delineation to cover more than 95% of each tumor.

Results

The average amplitude (mean ± standard deviation) was 0.6 ± 3.0 mm in the left-right (LR) direction, 2.3 ± 2.4 mm in the anterior-posterior (AP) direction, and 5.7 ± 3.4 mm in the superior-inferior (SI) direction, respectively. All of the segments moved posteriorly and superiorly during expiration. Segment 7 had the largest amplitude in the SI direction, at 8.6 ± 3.4 mm. Otherwise, the segments over the lateral side, including segments 2, 3, 6, and 7, had greater excursion in the SI direction compared to the medial segments. To cover more than 95% of each tumor, the required expansion margin of ITV in the LR, AP, and SI directions were at least 2.5 mm, 2.5 mm, and 5.0 mm on average, respectively, with variations between different segments.

Conclusions

The greatest excursion occurred in liver segment 7, followed by the segments over the lateral side in the SI direction. The individual segment expansion margin of ITV is required to delineate targets for each segment and direction.

The SBRT database initiative of the German Society for Radiation Oncology (DEGRO): patterns of care and outcome analysis of stereotactic body radiotherapy (SBRT) for liver oligometastases in 474 patients with 623 metastases

BACKGROUND

The intent of this pooled analysis as part of the German society for radiation oncology (DEGRO) stereotactic body radiotherapy (SBRT) initiative was to analyze the patterns of care of SBRT for liver oligometastases and to derive factors influencing treated metastases control and overall survival in a large patient cohort.

METHODS

From 17 German and Swiss centers, data on all patients treated for liver oligometastases with SBRT since its introduction in 1997 has been collected and entered into a centralized database. In addition to patient and tumor characteristics, data on immobilization, image guidance and motion management as well as dose prescription and fractionation has been gathered. Besides dose response and survival statistics, time trends of the aforementioned variables have been investigated.

RESULTS

In total, 474 patients with 623 liver oligometastases (median 1 lesion/patient; range 1–4) have been collected from 1997 until 2015. Predominant histologies were colorectal cancer (n = 213 pts.; 300 lesions) and breast cancer (n = 57; 81 lesions). All centers employed an SBRT specific setup. Initially, stereotactic coordinates and CT simulation were used for treatment set-up (55%), but eventually were replaced by CBCT guidance (28%) or more recently robotic tracking (17%). High variance in fraction (fx) number (median 1 fx; range 1–13) and dose per fraction (median: 18.5 Gy; range 3–37.5 Gy) was observed, although median BED remained consistently high after an initial learning curve. Median follow-up time was 15 months; median overall survival after SBRT was 24 months. One- and 2-year treated metastases control rate of treated lesions was 77% and 64%; if maximum isocenter biological equivalent dose (BED) was greater than 150 Gy EQD2Gy, it increased to 83% and 70%, respectively. Besides radiation dose colorectal and breast histology and motion management methods were associated with improved treated metastases control.

CONCLUSION

After an initial learning curve with regards to total cumulative doses, consistently high biologically effective doses have been employed translating into high local tumor control at 1 and 2 years. The true impact of histology and motion management method on treated metastases control deserve deeper analysis. Overall survival is mainly influenced by histology and metastatic tumor burden.

The emerging role of stereotactic radiotherapy in gastrointestinal malignancies: a review of the literature and analysis from the Irish perspective

Primary and secondary malignancies of the liver and pancreas result in significant morbidity and mortality, with increasing incidence and increasing demands on health services worldwide. Surgery is the only curative single modality of treatment and remains the gold standard. Unfortunately, up to 80% of the patients present with unresectable disease, and so, alternative efficacious local and systemic treatments are needed. Technologic advances in radiotherapy over recent decades have meant that precision high-dose treatment with stereotactic body radiotherapy (SBRT) has emerged as a viable cost-effective outpatient-based treatment in the management of these difficult to treat abdominal malignancies. This article reviews the current indications for SBRT in these settings, comparing it with other treatments including surgery, chemotherapy, radiofrequency ablation, and trans-arterial chemoembolisation. We also review the current use of abdominal SBRT and future projections in the Irish healthcare setting.

Endoluminal and Interstitial Brachytherapy for the Treatment of Gastrointestinal Malignancies: a Systematic Review

Radiation therapy is an integral component in the multimodality management of many gastrointestinal (GI) cancers at all stages of clinical presentation. With recent advances in technology and radiation delivery, external beam radiation therapy (EBRT) can be delivered with reduced toxicity. However, despite these advances, EBRT doses are still limited by the presence of radiosensitive serial structures near clinical targets in the GI tract. Relative to EBRT techniques, brachytherapy techniques have a lower integral dose and more rapid fall-off, allowing for high-dose delivery with little normal tissue exposure. Given the unique characteristics of brachytherapy, it is an attractive strategy to treat GI malignancies. This review addresses the application of both high-dose rate brachytherapy (HDRBT) and low-dose rate brachytherapy (LDRBT) to multiple GI malignancies for both definitive and palliative management.

Validation of the liver mean dose in terms of the biological effective dose for the prevention of radiation-induced liver damage

AIM

The purpose of this study was to determine the optimal mean liver biologically effective dose (BED) to prevent radiation-induced liver disease (RILD) in stereotactic body radiation therapy (SBRT).

BACKGROUND

The actual mean doses appropriate for liver irradiation in modern radiotherapy techniques have not been adequately investigated, although SBRT is sometimes alternatively performed using fractionated regimens.

MATERIALS AND METHODS

SBRT treatment plans for liver tumors in 50 patients were analyzed. All distributions of the physical doses were transformed to BED₂ using the linear-quadratic model. The relationship between physical doses and the BED₂ for the liver were then analyzed, as was the relationship between the mean BED₂ for the liver and the planning target volume (PTV).

RESULTS

A significantly positive correlation was observed between the mean physical dose for the background liver and the mean BED₂ for the whole liver (P < 0.0001, r = 0.9558). Using the LQ model, a mean BED₂ of 73 and 16 Gy for the whole liver corresponded to the hepatic tolerable mean physical dose of 21 and 6 Gy for Child-Pugh A- and B-classified patients, respectively. Additionally, the PTV values were positively correlated with the BEDs for the whole liver (P < 0.0001, r = 0.8600), and the background liver (P < 0.0001, r = 0.7854).

CONCLUSION

A mean BED₂ of 73 and 16 Gy for the whole liver appeared appropriate to prevent RILD in patients with Child-Pugh classes A and B, respectively. The mean BED₂ for the liver correlated well with the PTV.

Motion management strategies and technical issues associated with stereotactic body radiotherapy of thoracic and upper abdominal tumors: A review from NRG oncology

The efficacy of stereotactic body radiotherapy (SBRT) has been well demonstrated. However, it presents unique challenges for accurate planning and delivery especially in the lungs and upper abdomen where respiratory motion can be significantly confounding accurate targeting and avoidance of normal tissues. In this paper, we review the current literature on SBRT for lung and upper abdominal tumors with particular emphasis on addressing respiratory motion and its affects. We provide recommendations on strategies to manage motion for different, patient-specific situations. Some of the recommendations will potentially be adopted to guide clinical trial protocols.

SBRT planning for liver metastases: A focus on immobilization, motion management and planning imaging techniques

AIM

To evaluate the different techniques used for liver metastases Stereotactic Body Radiation Therapy (SBRT) planning. We especially focused on immobilization devices, motion management and imaging used for contouring.

BACKGROUND

Although some guidelines exist, there is no consensus regarding the minimal requirements for liver SBRT treatments.

MATERIALS AND METHODS

We reviewed the main liver metastases SBRT publications and guidelines; and compared the techniques used for immobilization, motion management, margins and imaging.

RESULTS

There is a wide variety of techniques used for immobilization, motion management and planning imaging.

CONCLUSIONS

We provide a subjective critical analysis of minimal requirements and ideal technique for liver SBRT planning.

Stereotactic body radiation therapy for liver metastasis - The linac-based Greater Poland Cancer Centre practice

AIM

The main purpose of this work is to give a technical description and present the properties of the liver SBRT protocol implemented in the Greater Poland Cancer Centre (GPCC) in Poznan, Poland.

BACKGROUND

Stereotactic body radiation therapy (SBRT) for liver metastasis is a non-invasive therapeutic option which enables irradiation of a small target in the body with a high dose.

MATERIALS AND METHODS

This study presents details of our linac-based liver SBRT protocol. Special emphasis has been placed on fiducial implantation, patient preparation (CT scanning, immobilization), treatment planning, and its implementation.

RESULTS

The liver SBRT treatment course implemented in the GPCC consists of three fractions to deliver a total of 45 Gy. Fraction delivery details with description of patient positioning (localization of liver metastasis) are presented below.

CONCLUSIONS

The literature validation of the assumptions concerning the steps of the GPCC linac-based liver SBRT procedure show their potential for an effective and patient friendly implementation.

Dosimetric Comparison of Plans for Photon- or Proton-Beam Based Radiosurgery of Liver Metastases

Purpose

Radiosurgery treatment of liver metastases with photon beams has been an established method for more than a decade. One method commonly used is the stereotactic body radiation therapy (SBRT) technique. The aim of this study was to investigate the potential sparing of the organs at risk (OARs) that the use of intensity-modulated proton therapy (IMPT), instead of SBRT, could enable.

Patients and Methods

A comparative treatment-planning study of photon-beam and proton-beam based liver-cancer radiosurgery was performed. Ten patients diagnosed with liver metastasis and previously treated with SBRT at the Karolinska University Hospital were included in the study. New IMPT plans were prepared for all patients, while the original plans were set as reference plans. The IMPT planning was performed with the objective of achieving the same target dose coverage as with the SBRT plans. Pairwise dosimetric comparisons of the treatment plans were then performed for the OARs. A 2-sided Wilcoxon signed-rank test with significance level of 5% was carried out.

Results

Improved sparing of the OARs was made possible with the IMPT plans. There was a significant decrease of the mean doses delivered to the following risk organs: the nontargeted part of the liver (P = .002), the esophagus (P = .002), the right kidney (P = .008), the spinal cord (P = .004), and the lungs (P = .002). The volume of the liver receiving less than 15 Gy was significantly increased with the IMPT plans (P = .004).

Conclusion

The IMPT-based radiosurgery plans provided similar target coverage and significant dose reductions for the OARs compared with the photon-beam based SBRT plans. Further studies including detailed information about varying tissue heterogeneities in the beam path, due to organ motion, are required to evaluate more accurately whether IMPT is preferable for the radiosurgical treatment of liver metastases.

Stereotactic Body Radiotherapy for Inoperable Liver Tumors: Results of a Single Institutional Experience

OBJECTIVES

Stereotactic body radiation therapy (SBRT) is an emerging treatment option for liver tumors unsuitable for ablation or surgery. We report our experience with SBRT in the treatment of liver tumors.

MATERIALS AND METHODS

Patients with primary or secondary liver cancer were identified in our local SBRT database. Patients were included irrespective of prior liver-directed therapies. The primary endpoint of our review was in-field local control (LC). Secondary endpoints were progression-free survival (PFS), overall survival (OS), and toxicity.

RESULTS

From 2009 to 2015, a total of 71 liver lesions in 68 patients were treated with SBRT (three patients had two liver lesions treated). The median age was 71 years (27-89 years). Hepatocellular carcinoma (HCC) was the diagnosis in 23 patients (34%), with the grade of Child-Pugh A (52%), B (39%), or C (nine percent) cirrhosis. Six patients (nine percent) had intrahepatic cholangiocarcinoma (IHC). The remaining 39 patients (57%) had metastatic liver lesions. Colorectal adenocarcinoma was the most common primary tumor type (81%). The median size for HCC, IHC, and metastatic lesions was 5 cm (2-9 cm), 3.6 cm (2-4.9 cm), and 4 cm (1-8 cm), respectively. The median prescribed dose was 45 Gy (16-50 Gy). Median follow-up was 11.5 months (1-45 months). Actuarial one-year in-field LC for HCC and metastatic lesions was 85% and 64% respectively (p= 0.66). At one year, the actuarial rate of new liver lesions was 40% and 26%, respectively, (p=0.58) for HCC and metastases. Only six patients with IHC were treated with SBRT in this study - in these patients, one-year LC was 78% with new liver lesions in 53%. The SBRT treatments were well tolerated. The side effects included common criteria for adverse events (CTCAE) v4 grade 1 acute gastrointestinal toxicity in three patients, grade 3 nausea in one patient, and grade 3 acute dermatitis in another patient. Two patients had grade 5 toxicity. Radiation pneumonitis was observed in one patient two months post-SBRT treatment, and another patient was suspected to have had radio-induced liver disease (RILD) two months after SBRT. No late toxicity was seen.

CONCLUSION

SBRT is a well-tolerated and effective alternative treatment option for selected patients with primary and metastatic liver tumors.

New Perspectives in the Treatment of Colorectal Metastases

BACKGROUND

In recent years, the management of metastatic colorectal cancer has become more aggressive and more multidisciplinary. New treatment options have been proposed in addition to the standard approach of resection of liver metastases and chemotherapy.

SUMMARY

Selected patients with synchronous limited peritoneal and liver disease (peritoneal cancer index <12 and <3 liver metastases) can be scheduled for aggressive treatment, including cytoreductive surgery, hyperthermic intraperitoneal chemotherapy, and liver resection. This approach has achieved survival benefits, even if the treatment is unlikely to be curative in most patients. Moreover, liver transplantation has been recently reconsidered for liver-only metastases, resulting in the de facto reinstatement of the chance of surgery for some unresectable patients. Even though indications for liver transplantation remain to be standardized, preliminary studies have reported extremely promising outcomes. Radio-embolization has proven to be an effective additional tool for the treatment of unresectable tumors, and its potential role in association with chemotherapy for resectable disease is currently being investigated. Stereotactic body radiation therapy is a safe, non-invasive, and effective therapeutic option for patients with inoperable oligometastatic disease. Thanks to recent technical progress, high radiation doses can now be delivered in fewer fractions with excellent local disease control and a low risk of radiation-induced liver injury. Finally, radiofrequency ablation (RFA) for colorectal metastases has become more effective, with results approaching those of surgical series. New interstitial treatments, such as microwave ablation and irreversible electroporation, could overcome some of the limitations of RFA, thereby further expanding indications and optimizing outcomes.

KEY MESSAGES

Currently, a multidisciplinary approach to patients with colorectal liver metastases is mandatory. Aggressive surgical treatments should be integrated with all the available non-surgical options to maximize disease control and patient survival.

The role of SBRT in oligometastatic patients with liver metastases from breast cancer

Liver metastases from breast cancer are a common occurrence. Local ablative therapies are a promising therapeutic option for these patients, with the potential for a long term disease control in the setting of "oligometastatic patients". Identification of the perfect candidate for local approaches is still challenging and unclear. Stereotactic body radiation therapy (SBRT) is one of the most valuable local therapy, because of great efficiency, low morbidity and minimal invasiveness. In this paper, we reviewed the state of the art in the care of breast cancer patients with liver metastases, with a focus on SBRT.

Stereotactic body radiotherapy for the pancreas: a critical review for the medical oncologist

With recent advances in imaging modalities and radiation therapy, stereotactic body radiotherapy (SBRT) has allowed for the delivery of high doses of radiation with accuracy and precision. As such, SBRT has generated favorable results in the treatment of several cancers. Although the role of radiation has been controversial for the treatment of pancreatic ductal adenocarcinoma (PDAC) due to rather lackluster results in clinical trials, SBRT may offer improved outcomes, enhance the quality of life, and aid in palliative care settings for PDAC patients. This review delineates the role of SBRT in the treatment of PDAC, presents the defining principles of radiation biology and the radiation oncology work flow, and discusses the prospects of new treatment regimens involving tumor immunology and radiation therapy.

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.