SBRT Liver when and how.pptx
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This document discusses stereotactic body radiation therapy (SBRT) for liver tumors. It begins with an overview of liver anatomy and the Couinaud classification system for liver segments. It then discusses SBRT, including indications such as hepatocellular carcinoma and liver metastases. Clinical outcomes for SBRT in HCC and cholangiocarcinoma are summarized from various studies. Case selection criteria and dose constraints are outlined for SBRT treatment of liver tumors.
SBRT Liver when and how.pptx
- 1. SBRT Liver When & How ? Dr Rushi Panchal HOD - Radiation Oncology Shree Krishna Hospital Karamsad, Anand Gujarat
- 2. • Anatomy of liver and its segment. • Brief about what is SBRT and clinical outcome in liver SBRT. • Case selection criteria in both scenario Hepatocellular carcinoma (HCC) & Liver metastases • Simulation to execution : Simulation contouring Dose Prescription planning image guidance OUTLINE Points Not covered : (a) Detail of Motion management (b) Follow up after SBRT
- 3. ANATOMY • Blood supply : portal vein supplying 70-80% and the hepatic artery 20- 30%. There are three hepatic veins (right, middle, left) drains blood from liver in to IVC. • The Couinaud classification of liver anatomy : divides the liver into eight functionally independent segments. • The numbering of the segments is in a clockwise manner. Segment I (the caudate lobe) is located posteriorly. It is not visible on a frontal view. The liver is divided in three vertical planes: • The plane of the right hepatic vein divides the right lobe into anterior (V/VIII) vs posterior segment (VI/VII) • The plane of the middle hepatic vein divides the liver into right and left lobes. This plane runs from IVC to the GB Fossa. • The umbilic plane runs from the falciform ligament to the inferior vena cava and separates the left lateral and medial segments (II & III from IV). • Portal vein The portal vein divides the liver into upper and lower segments. The left and right portal veins branch superiorly and inferiorly to project into the center of each segment.
- 4. Couinaud classification : • The right border of the liver is formed by segment V and VIII • On a normal frontal view the segments VI and VII because they are located more posteriorly. • Although segment IV is part of the left hemi more to the right. ANATOMY
- 5. How to separate liver segments on cross sectional imaging • Left vs Right liver: IVA/B vs V/VIII Extrapolate a line from the gallbladder fossa superiorly along the middle hepatic vein to the IVC (red line). • Left liver: lateral(II/III) vs medial segment (IVA/B)Extrapolate a line along the falciform ligament superiorly to the confluence of the left and middle hepatic veins at the IVC (blue line). • Right liver: anterior (V/VIII) vs posterior segment (VI/VII)Extrapolate a line along the right hepatic vein from the IVC inferiorly to the lateral liver margin (green line). ANATOMY Upper segments Lowerr segments
- 6. Safe delivery/Accuracy is of utmost importance due to high fractional dose and small number of fractions Custom immobilization Respiratory management Image guidance PTV PTV • A critical issue in RT for HCC is the control of respiratory movement, as Liver motion is complex owing to organ deformation and rotation with respiration. • For SBRT, control of respiratory motion should be considered more strictly than for conventional RT to ensure it receives the intended dose (to improve the accuracy of treatment delivery without geographical miss ) while reducing the dose to surrounding normal tissue. SBRT : Overview Stereotactic body radiation therapy (SBRT) is the term applied in the United States by the American Society of Therapeutic Radiology and Oncology (ASTRO) for the management and delivery of image-guided high-dose radiation therapy with tumor-ablative intent within a course of treatment that does notmexceed 5 fractions.
- 7. Unlike intracranial radiosurgery, where the PTV is immobile within the skull and therefore relatively easy to fix in relation to the radiation source, at extra-cranial sites there are the problems of internal organ motion and external patient movement Development of RT mainly focuses on improving two factors: accuracy and precision. Accuracy of RT implies that radiation can be delivered to the correct location each time, despite various uncertainties between the time of radiation treatment planning and the time of actual treatment. Precision of RT means the ability to control distribution of radiation to make sure that prescribed dose is administered exactly to tumor site, and that radiation is not delivered to surrounding normal tissues.
- 8. • Radiotherapy for liver tumor in past, has met with less enthusiasm than most other sites due to inadequate knowledge about partial liver tolerances, poor delivery techniques, inability to control uncertainties associated with breathing motion and risk of RILD (Radiation induced liver damage). • More recent experiences have demonstrated that high-dose partial liver RT may be safer and more effective. • In recent years, technological advances in target definition, treatment planning, and setup verification have allowed radiation oncologists to implement hypofractionated stereotactic body radiation therapy (SBRT) for liver tumors. SBRT : Overview
- 9. Internal fiducial markers can be residual radio- opaque lipiodol after TACE or a commercial fiducial marker which is inserted under sono-guidance. There are several methods accounting for target motion to reduce errors from respiratory motion and improve the accuracy of treatment planning or delivery and can be broadly categorized as motion compensating (active breathing control and tumor tracking) or motion restricting (abdominal compression).
- 10. A.J. Cole et al. / Clinical Oncology 26 (2014) 67e80
- 11. BALL ET AL. J Appl Clin Med Phys. 2022;23:e13810.
- 13. AAPM Task group 101
- 14. To considered Dmax if the constraint volume was ≤0.1 cc. Practical Radiation Oncology! (2021) 11, e355−e365 AAPM Task group 101
- 15. SBRT : Indication and clinical outcome • Liver cancer : HCC & Cholangiocarcinoma • Liver metastasis
- 16. Y. Hu, C. Zhao, R. Ji et al. Journal of the National Cancer Center 2 (2022) 171–182 SBRT : Outcome in HCC
- 17. • Most patients had invasion of their cancer into the hepatic vasculature (a poor prognostic factor), and a small number had metastases outside of the liver. The median age was 66 years (range 27-84). • Overall survival was longer for patients who received a combination of SBRT and sorafenib, compared to those on sorafenib alone (15.8 vs. 12.3 months; one-sided p = 0.055). • Progression-free survival was improved with the addition of SBRT, from 5.5 months with sorafenib alone to 9.2 months with the combination therapy (HR = 0.92, p<0.001). • Patients in the combination arm also had longer intervals before their cancers progressed (18.5 vs. 9.5 months; HR = 0.69, p=0.034). • Treatment-related side effects were not significantly different between the treatment groups. 42% of patients on the sorafenib arm and 47% of patients on the SBRT/sorafenib arm experienced severe (i.e., grade 3 or higher) side effects, and there was one treatment-related death, on the sorafenib-only arm.
- 18. Y. Hu, C. Zhao, R. Ji et al. Journal of the National Cancer Center 2 (2022) 171–182
- 20. However, the possibility to deliver very high RT dose on this site is limited by the low radiation tolerance of both liver and GI tract. • Nine studies were retrospectiveand • one was a prospective Phase I study. • No randomized controlled trial was found. SBRT : Cholangiocarcinoma
- 21. • While significant heterogeneity exists in the current OMD definitions in the literature, consensus was reached on multiple key questions. • Based on available data, OMD can to date be defined as 1–5 metastatic lesions, a controlled primary tumor being optional, but where all metastatic sites must be safely treatable. Y. Lievens et al. / Radiotherapy and Oncology 148 (2020) 157–166 ESTRO-ASTRO OMD consensus document Progression of selected metastatic deposit whilst other remain controlled by systemic therapy. SBRT Liver metastasis
- 23. SBRT Liver metastasis https://doi.org/10.1016/j.semradonc.2022.11.008
- 24. Ohri et al. Int J Radiation Oncol Biol Phys, Vol. 110, No. 1, pp. 188e195, 2021 • Thirteen articles • Stereotactic body radiation therapy for primary liver tumors provides high rates of durable local control, with no clear evidence for a dose response relationship among commonly utilized schedules (33-60 Gy, 3-5 fractions, BED 60-180 Gy ). The 1-, 2-, and 3-year actuarial local control rates after SBRT for primary liver tumors (n = 431) were 93%, 89%, and 86%, respectively. • Excellent local control rates are also seen after SBRT for liver metastases when BEDs of >100 Gy are utilized. Lower 1- (90%), 2- (79%), and 3-year (76%) actuarial local control rates were observed for liver metastases. with BEDs exceeding 100 Gy10 (3-year local control 93%) than for those treated with BEDs of ≤100 Gy10 (3- year local control 65%, P < .001). • The most common histology for patients with liver metastases was colorectal cancer, which accounted for 32% to 100% of the treated lesions in the articles we analyzed (overall 56% of liver metastases). • We therefore believe that it is reasonable to use relatively conservative SBRT schedules, such as 8 to 10 Gy 5 fractions, in this patient population of primary liver cancer. More aggressive schedules should be used with caution, especially in patients with underlying liver disease. • Tumor control probability modeling revealed that the 2-year local control is expected to increase progressively with BED, reaching 76% for a BED of 100 Gy and 90% for a BED of 180 Gy. Hence, relatively aggressive SBRT schedules delivering a BED ! 100 Gy10 should be considered for patients with liver metastases. SBRT Liver metastasis Vs HCC
- 25. Grimm et al. Int J Radiation Oncol Biol Phys, Vol. 110, No. 1, pp. 1e10, 2021 HCC appears to be a relatively radiosensitive tumor, such that, above a certain threshold dose, there may be little benefit in further dose escalation, and potential for increased toxicity. SBRT Liver metastasis Vs HCC • 50% of patients with colorectal adenocarcinoma will develop metastatic disease to the liver, and it is often the first site of metastatic progression. • Liver metastases can cause significant pain from hepatic capsular involvement, thus negatively affecting health- related quality of life for patients with metastatic disease. In addition, more extensive liver disease can cause liver dysfunction that can limit the administration of systemic chemo- therapy and ultimately lead to death. • The potentially curative treatment of liver metastasis with surgical resection has been reported for many years, with 5-year survival rates now of 50%-60%.Moreover, if patients are well selected, up to 20% can achieve long- term disease-free survival after hepatectomy. • Unfortunately, only 10%-20% of liver metastases are amenable to resection. For unresectable tumors, advances in combination chemotherapy and targeted agents have resulted in a doubling of median survival from 10 to 20 months in patients with metastatic colorectal cancer over the past 2 decades. • Alter- natives to surgery, such as radiofrequency ablation, cryoablation, and alcohol injection, have been attempted and have shown some benefit. However, these techniques suffer from many limitations due to lesion location, adjacent structures, and high recurrence rates.
- 26. SBRT LIVER WHEN & HOW
- 27. • Decompensation of liver disease (jaundice, ascites, encephalopathy) reflects non-preserved liver function irrespective of the CP Score / (MELD) score. • TSM : specific patient profile may induce shift of recommendation to the option that would be considered a priority for more advanced stage. • Untreatable progression : It represents failure of selected treatment strategy and emerges when patient present treatment failure or progression but still fit in to their initial BCLC Stage thus warranting the consideration of therapy corresponding to more advanced stage. • CSPH : Hepatic venous pressure gradient >10 mmhg.
- 28. • CP A-B7, PS 0–2, BLCL : B,C(PVT),A (inoperable), 700 cc functional liver reserve, no Ext hep disease, Patients with active viral hepatitis (transaminases> 2.5 times the upper normal limit) should be started on anti-viral therapy at least 2 weeks before SBRT , no signs of hepatic decompensation ( jaundice, Intractable ascites, encephalopathy, Varices ), > 5 mm away from GI Structure. • SBRT is a treatment option for patients with unresectable disease ( unsuitable for resection / transplant ), or for those who are medically inoperable due to comorbidity, can be considered as an alternative to ablation (RFA) /embolization (TACE) techniques or when these therapies have failed/Refractory or they are contraindicated. • SIZE/NUMBER OF LESIONS : patients with 1 to 3 tumors. SBRT could be considered for larger lesions or more extensive disease, if there is sufficient uninvolved liver and liver radiation tolerance can be respected. Indication for HCC SBRT : • Unsuitable for resection or transplant or radiofrequency ablation (RFA) • Unsuitable for TACE or refractory to TACE • Barcelona Clinic Liver Cancer Stage (BCLC) Intermediate (B) or Advanced (C) • Often used in 1-3 lesions, could be considered for larger lesions or more extensive disease if there is sufficient uninvolved liver and liver radiation tolerance can be respected. • Child Pugh A/ Early Child Pugh B. Contraindication for HCC SBRT • Any one hepatocellular carcinoma > 15 cm / Total maximal sum of hepatocellular carcinoma > 20 cm/ More than 5 discrete intrahepatic parenchymal foci of HCC • Direct tumor extension into the stomach, duodenum, small bowel or large bowel/ Measureable common or main branch biliary duct involvement with HCC • Extrahepatic metastases or malignant nodes (that enhance with typical features of HCC) > 2.0 cm, in sum of maximal diameters (e.g. presence of one 2.4 cm metastatic lymph node or two 1.2 cm lung lesions). Note that benign non-enhancing periportal lymphadenopathy is not unusual in the presence of hepatitis and is permitted, even if the sum of enlarged nodes is > 2.0 cm • Hepatic insufficiency resulting in clinical jaundice, encephalopathy and/or variceal bleed. indications for radiotherapy include definitive treatment in Barcelona Clinic Liver Cancer (BCLC) A or B, bridging to transplant, recurrent or large unresectable tumours, combination with TACE for large BCLC B, BCLC C with portal vein thrombosis and palliative treatment. Case selection for HCC SBRT
- 29. Prerequisite For all patients, the following criteria calculated from baseline CT or MR scans should be met: Liver volume minus intrahepatic GTV > 700 cc. Intrahepatic tumor GTV/liver volume ratio <80%. (The effective liver volume irradiated (Veff) had to be less than 0.8, where 1.0 represents whole organ irradiation) Minimal distance from GTV to stomach, duodenum, small or large bowel > 1 cm. • Varying approaches to dose selection have been adopted and include a biological individualized strategy based on the effective volume of irradiated liver and Lyman normal tissue complication probability (NTCP) estimation of classic radiation-induced liver disease or a critical volume approach, which limits the dose received by a specified volume of normal liver often 700 mL. • As well as liver doses, luminal doses are also important. One trial, with one of the highest high-grade GI toxicity rates, did not specify luminal constraints, which may have contributed to the high toxicity, although pre-existing GI ulceration may have had an impact. Another study observed that all patients with high-grade GI toxicity had lesions 0.5 cm from luminal structures. Thus, luminal constraints or specification of minimal distances between targets and lumen, or both, are necessary.
- 30. • Age is not considered in selection criteria, as even elderly and fragile patients can safely undergo SBRT. This non-invasive and well-tolerated therapy is a good option for patients unsuitable for surgery. • Intrinsic radio-sensitivity of tumours is not an issue ,as SBRT can be used regardless of histopathology thanks to the use of ablative doses, with similar local control rates in radioresistant and radiosensitive primary tumour. Indication & Contraindication in Liver mets Safety : • >700 cc residual liver • Focal tumor distribution • >5 mm from luminal GI tissue Efficacy : • Size : <3cm vs 3-6cm vs >6cm • Number of tumors : < 3 v.s 3-5 vs >5 • Tools to select patients : 1) Imaging : PET to rule out extrahepatic disease Primovist MR to rule out diffuse hepatic metastases 2) Natural history : should have expected survival of > 6 months from the their primary lesion. Patients presenting with synchronous metastasis should also have adequate systemic and local treatment before proceeding with liver directed treatment.
- 31. Lowest risk : central, away from luminal GI, ribs, biliary tract Liver SBRT: Lowest Risk to Higher Risk locations
- 32. Low risk : sup/lateral liver Liver SBRT: Lowest Risk to Higher Risk locations
- 33. Potential risk : central lesions, biliary Liver SBRT: Lowest Risk to Higher Risk locations
- 34. Higher risk : Adjacent to stomach and bowel Liver SBRT: Lowest Risk to Higher Risk locations
- 35. Simulation Supine & arms up Custom immobilization is recommended (e.g. With vacuum immobilization, patient positioning boards, knee cushions, and/or breath hold immobilization with active breathing control).
- 36. BALL ET AL. J Appl Clin Med Phys. 2022;23:e13810. Simulation
- 37. • Intravenous contrast-enhanced, multiphasic CT is required for GTV delineation. Needs 2 – 2.5 mm slice thickness for Scan. If fixed oral contrast/ water intake is given then repeat at time of treatment. • For HCC : Tumor enhances on the arterial phase before washing out during venous and delayed phases, obtained during breath hold. • For liver mets : PV Phase is used to delineate hypo vascular mets and Arterial phase for Hyper vascular mets. • 4D-CT can aid in estimation of motion & generation of i-GTV/ITV. • MRI sequences &/ PET-CT can further assist with GTV definition. • CTV margins are typically not employed except prior TACE (t) sites (CTVt), or adjacent RFA (r) (or MW ablation) cavity (CTVr) are permitted. • PTV margins are usually individualized and are ideally 5 mm but up to 10 mm may be required, depending on the motion management strategy. Aorta and branches IVC,PV,Solid organ Parenchyma Renal collecting, ureter, U_bladder NON CONTRAST ARTERIAL ENHANCMENNT VENOUS PHASE_ WASHOUT DELAYED PHASEMORE WASHOUT CAPSULE/PSE UDO CAPSULE Simulation & Target Volume Contouring Aspects HCC
- 38. Analyze the tumor in all phases of triple phase CT And See the greatest resolution Simulation & Target Volume Contouring Aspects HCC
- 39. Simulation & Target Volume Contouring Aspects HCC • The primary tumor(s) and any tumor vascular thrombi must be treated • The Gross Tumor Volume (GTV) is defined as all parenchymal and vascular HCC visualized on contrast enhanced CT and/or MRI, most often best seen on arterial phase (as hyperintensity) and/or venous or delayed phase (as hypointensity relative to liver). Vascular HCC thrombi (GTVv) most often are best seen on venous phase imaging as hypointensity relative to the contrast in the vessel, Vascular HCC may be combined with parenchymal HCC (labeled as GTVp or GTVpv) if they are to be treated to the same dose. • Treatment of non-tumor extrahepatic vascular thrombi, RFA cavities and prior TACE sites is not recommended. no prophylactic nodal irradiation is allowed. • It is expected that there will be no expansion from GTV to CTV for the majority of cases. However, CTV expansions to include regions at high risk for microscopic disease, including non- tumor vascular (v) thrombi (CTVv), prior TACE (t) sites (CTVt), or adjacent RFA (r) (or other ablation) sites (CTVr) are permitted. • PTV will provide a margin around each CTV to compensate for set-up and internal organ motion • minimum PTV margin of 4 mm around each CTV is required in all directions (for example if active breathing control is used with excellent reproducibility). The maximum permitted PTV margin is 20 mm, expected to be used uncommonly. PTV margins ≤ 10 mm are a goal.
- 40. 4D CT Scan Simulation
- 41. 4D Simulation
- 42. 4D Simulation
- 43. BALL ET AL. J Appl Clin Med Phys. 2022;23:e13810. Simulation & Target Volume Contouring Aspects HCC
- 44. OAR Contouring for HCC • At minimum, these structures are required to be contoured at the level of the PTV and over any region received > 10 Gy. It requires : Normal Liver ( Liver – GTV), Stomach, Duodenum, Small bowel, large bowel, Sp_Cord, Heart, Ribs, Lungs, Kidney, CBD, Gall bladder, Great vessel. • An upper abdominal/liver atlas, posted at the ITC website, may be used as a guide for contouring.
- 45. • Individualized dose prescription (27.5- 50Gy in 5#) to isodose covering 95% of PTV based on tumor size, the volume of normal tissues irradiated (correlated with mean liver dose), as proximity of GI luminal structures to PTV, normal tissue constraints must be maintained, CP Score (severity of liver Disease). Treatment on alternate day. • When using SBRT for HCC as a bridging therapy, as the final objective is not complete ablation, doses no higher than 45 Gy in five fractions are recommended, and consideration should be given to reduce the doses in central lesions or in other locations in which fibrosis may lead to a potential increased risk of toxicity. • The dose to multiple PTVs may be different. Vascular tumor thrombosis (e.g., portal vein thrombosis) dose should be the same as the HCC prescription dose. However, lower doses are acceptable if required to maintain normal tissue limits. RFA cavities can be treated to differential doses to optimize normal liver sparing . • The goal is to use the highest allowable prescription dose to the PTV, while respecting normal tissue constraints. In the absence of adjacent GI luminal structures that may limit dose, the PTV dose prescription should be as high as possible based on mean liver dose (MLD, defined as the mean dose to the liver minus all GTVs). Dose prescription for HCC For small tumors away from luminal GI tissues, a fixed dose may be used (eg, 40 Gy in 5 fractions), but for larger tumors, where doses must be limited because of normal liver tolerance, an individualized strategy, based on escalating dose based on liver constraints, is most appropriate.
- 46. Dose prescription for HCC
- 47. 3 × 15–25 Gy : for patients with tumors <3 cm in size and adequate liver reserve (CP-A5) 5 × 10–12 Gy : for patients with tumors between 3 and 5 cm or inadequate liver reserve (CP-A 6) 10 × 5–5.5 Gy : for patients with tumors >5 cm in size or CP-B scores. S. Apisarnthanarax et al Practical Radiation Oncology! (2022) 12, 28−51
- 48. Plan evaluation for HCC : • The prescription isodose should encompass 95% of PTV. A goal is that 100% of the CTV is encompassed by the prescription dose. Maximum dose within PTV = 150%. Maximum dose outside PTV = 120% of the maximal PTV prescription. Differential prescription to GTV/HOT-CORE : 20-30% higher. • Efforts should be made to keep the 30Gy isodose as conformal as possible. • If multiple PTVs, the MLD should be evaluated with the prescription dose corresponding to the highest dose level that any PTV is treated. • Reducing the maximal dose to all luminal gastrointestinal normal tissues should be a planning priority to reduce the risk of gastrointestinal toxicity. • Target coverage : Rx isodose should encompass 95% PTV / 100% CTV coverage • Normal tissue avoidance : – Prescription dose based on volume of normal liver irradiated (correlated with mean liver dose) – In absence of adjacent luminal structures to limit dose, PTV dose may be the highest allowable • Conformality : Prescription isodose 30 Gy isodose • Most simple solution meeting acceptability criteria : VMAT – 1 arc vs. 2 arcs
- 49. Constraints for HCC • Mean liver dose & Dose to 700cc should be given priority over Veff to minimize NTCP. • Liver being parallel organ can receive high doses of radiation as long as a sufficient volume of healthy liver tissue is spared. Kavanagh et al. used a similar SBRT dosimetric constraint by requiring that 700 mL of the normal liver receive no more than a total of 15 Gy in a three- fraction regimen for liver SBRT. This critical volume- type restriction for the normal liver is comparable to liver surgeons requiring a certain predicted minimal volume of liver to remain in order to ensure that a patient has adequate and reasonable liver functional reserve after surgical resection. • The effective liver volume (Veff) irradiated is a model based on the normal liver volume and the volume irradiated. The Veff is defined as the normal liver volume minus all GTVs, which if homogenously irradiated to the maximum dose would be associated with the same estimated risk of RILD as the delivered heterogeneous treatment plan. A lower Veff correlated with significantly lower risks of RILD, demonstrating in the setting of dose escalation, high doses can be delivered as long as the mean dose to the liver is taken into account. Non-liver OARs
- 50. Mean dose to liver should be restricted to 18Gy in CP A5-6 for 5-6 # and < 6Gy in CP B7 S. Apisarnthanarax et al Practical Radiation Oncology! (2022) 12, 28−51
- 53. Pre & post SBRT considerations • Pre SBRT : – Ensure recovery from chemo (> 2 weeks gap ) • Caution with anti-VEGF therapy – Fiducial markers – in needed for IGRT – Antiemetics - if stomach irradiated – Steroid - if high risk for biliary edema or massive vascular invasion – Antiviral therapy if untreated Hepatitis B : start Antiviral 2 weeks before • Post SBRT : – Consider proton pump inhibitors – if stomach irradiated
- 54. Image Guidance • Daily image guidance is necessary. • Orthogonal x-rays and cone beam CT (CBCT) are most commonly employed. CBCT matching has been suggested to be superior to orthogonal x- rays. • The use of peritumoral fiducials ( Gold seeds ), with both x-rays and CBCT, can further enhance setup. • The presence of lipiodol following TACE, or surgical clips, has also been used as surrogates for tumor position if not then liver contour can be taken in to the account. • Depending on the method of respiratory motion compensation, CBCT acquired in breath hold or as a 4D- CBCT to assist in matching. Lipiodol / fiducial useful in IGRT LIVER DUODENUM LARGE BOWEL STOMACH
- 55. A. Burton et al. Physics and Imaging in Radiation Oncology 24 (2022) 21–29
- 56. BALL ET AL. J Appl Clin Med Phys. 2022;23:e13810.
- 57. Future implementation : MR Guided radiotherapy • The implementation of daily online image guidance using MRI in the context of the MR-linac will provide enhanced soft tissue information compared to CBCT, thus improving setup accuracy, without the need for fiducials. • The system may also allow intrafraction motion monitoring. Adaptive radiotherapy would allow creation of “plans of the day,” based on each day's anatomy, which could further improve accuracy. • These measures may reduce uncertainties, PTV margins, and normal tissue irradiation, hopefully reducing toxicities and improving the therapeutic ratio for HCC SBRT.