Proton beam therapy for hepatocellular carcinoma: a retrospective review of 162 patients

Assessing alimentary tract radiation in liver cancer treatment with proton beam therapy: a PET/CT imaging study

BACKGROUND

Proton beams deposit energy along their path, abruptly stopping and generating various radioactive particles, including positrons, along their trajectory. In comparison with traditional proton beam therapy, scanning proton beam therapy is effective in delivering proton beams to irregularly shaped tumors, reducing excessive radiation exposure to the alimentary tract during the treatment of liver cancer.

METHODS

In this study, we utilized positron emission tomography/computed tomography (PET/CT) imaging to assess the total amount of radiation to the alimentary tract during liver cancer treatment with proton beam therapy, involving the administration of complex irradiation in 13 patients.

RESULTS

This approach resulted in the prevention of excess radiation. The planned radiation restraint doses for the colon exhibited a significant correlation with the PET values of the colon (correlation coefficient 0.8384, P = .0003). Likewise, the scheduled radiation restraint doses for the gastroduodenum were correlated with the PET values of the gastroduodenum (correlation coefficient 0.5397, P = .0569).

CONCLUSIONS

PET/CT conducted after proton beam therapy is useful for evaluating excess radiation in the alimentary tract. Proton beam therapy in liver cancer, assessed via PET/CT, effectively reduced alimentary tract radiation, which is vital for optimizing treatments and preventing excess exposure.

Optimal hypofractionated radiation therapy schemes for early-stage hepatocellular carcinoma

PURPOSE

Stereotactic body radiation therapy (SBRT) has been emerging as an efficacious and safe treatment modality for early-stage hepatocellular carcinoma (HCC), but optimal fractionation regimens are unknown. This study aims to analyze published clinical tumor control probability (TCP) data as a function of biologically effective dose (BED) and to determine radiobiological parameters and optimal fractionation schemes for SBRT and hypofractionated radiation therapy of early-stage HCC.

MATERIAL AND METHODS

Clinical 1- to 5-year TCP data of 4313 patients from 41 published papers were collected for hypofractionated radiation therapy at 2.5-4.5 Gy/fraction and SBRT of early-stage HCC. BED was calculated at isocenter using three representative radiobiological models developed per the Hypofractionated Treatment Effects in the Clinic (HyTEC) initiative. Radiobiological parameters were determined from a fit to the TCP data using the least χ2 method with one set of model parameters regardless of tumor stages or Child-Pugh scores A and B.

RESULTS

The fits to the clinical TCP data for SBRT of early-stage HCC found consistent α/β ratios of about 14 Gy for all three radiobiological models. TCP increases sharply with BED and reaches an asymptotic maximal plateau, which results in optimal fractionation schemes of least doses to achieve asymptotic maximal tumor control for SBRT and hypofractionated radiation therapy of early-stage HCC that are found to be model-independent.

CONCLUSION

From the fits to the clinical TCP data, we presented the first determination of radiobiological parameters and model-independent optimal fractionation regimens in 1-20 fractions to achieve maximal tumor control whenever safe for SBRT and hypofractionated radiation therapy of early-stage HCC. The determined optimal fractionation schemes agree well with clinical practice for SBRT of early-stage HCC. However, most existing hypofractionated radiation therapy schemes of 3-5 Gy/fraction are not optimal, higher doses are required to maximize tumor control, further validation of these findings is essential with clinical TCP data.

Impact of iodinated oil in proton therapy on relative stopping power of liver post-cTACE

Objective. Conventional transarterial chemoembolization (cTACE) is a common treatment for hepatocellular carcinoma (HCC), often with unsatisfactory local controls. Combining cTACE with radiotherapy shows a promise for unresectable large HCC, with proton therapy preserving healthy liver tissue. However, the proton therapy benefits are subject to the accuracy of tissue relative stopping power (RSP) prediction. The RSP values are typically derived from computed tomography (CT) images using stoichiometric calibration. Lipiodol deposition significantly increases CT numbers in liver regions of post-cTACE. Hence, it is necessary to evaluate the accuracy of RSP in liver regions of post-cTACE.Approach. Liver, water, and iodinated oil samples were prepared. Some liver samples contained iodinated oil. The water equivalent path length (WEPL) of sample was measured through the pullbacks of spread-out Bragg peak (SOBP) depth-dose profiles scanned in a water tank with and without sample in the beam path. Measured RSP values were compared to estimated RSP values derived from the CT number based on the stoichiometric calibration method.Main results. The measured RSP of water was 0.991, confirming measurement system calibration. After removing the RSP contribution from container walls, the pure iodinated oil and liver samples had RSP values of 1.12 and 1.06, while the liver samples mixed with varying oil volumes (5 ml, 10 ml, 15 ml) showed RSP values of 1.05, 1.05 and 1.06. Using the stoichiometric calibration method, pure iodinated oil and liver samples had RSP values of 2.79 and 1.06. Liver samples mixed with iodinated oil (5 ml, 10 ml, 15 ml) had calculated RSP values of 1.21, 1.34, and 1.46. The RSP discrepancy reached 149.1% for pure iodinated oil.Significance.Iodinated oil notably raises CT numbers in liver tissue. However, there is almost no effect on its RSP value. Proton treatment of post-cTACE HCC patients can therefore be overshooting if no proper measures are taken against this specific effect.

Pencil Beam Scanning Carbon Ion Radiotherapy for Hepatocellular Carcinoma

Purpose

Carbon ion radiotherapy (CIRT) has emerged as a promising treatment modality for hepatocellular carcinoma (HCC). However, evidence of using the pencil beam scanning (PBS) technique to treat moving liver tumors remains lacking. The present study investigated the efficacy and toxicity of PBS CIRT in patients with HCC.

Methods

Between January 2016 and October 2021, 90 consecutive HCC patients treated with definitive CIRT in our center were retrospectively analyzed. Fifty-eight patients received relative biological effectiveness-weighted doses of 50-70 Gy in 10 fractions, and 32 received 60-67.5 Gy in 15 fractions, which were determined by the tumor location and normal tissue constraints. Active motion-management techniques and necessary strategies were adopted to mitigate interplay effects efficiently. Oncologic outcomes and toxicities were evaluated.

Results

The median follow-up time was 28.6 months (range 5.7-74.6 months). The objective response rate was 75.0% for all 90 patients with 100 treated lesions. The overall survival rates at 1-, 2- and 3-years were 97.8%, 83.3% and 75.4%, respectively. The local control rates at 1-, 2- and 3-years were 96.4%, 96.4% and 93.1%, respectively. Radiation-induced liver disease was not documented, and 4 patients (4.4%) had their Child-Pugh score elevated by 1 point after CIRT. No grade 3 or higher acute non-hematological toxicities were observed. Six patients (6.7%) experienced grade 3 or higher late toxicities.

Conclusion

The active scanning technique was clinically feasible to treat HCC by applying necessary mitigation measures for interplay effects. The desirable oncologic outcomes as well as favorable toxicity profiles presented in this study will be a valuable reference for other carbon-ion centers using the PBS technique and local effect model-based system, and add to a growing body of evidence about the role of CIRT in the management of HCC.

Current evidence and the potential role of proton beam therapy for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related death, and external beam radiation therapy has emerged as a promising approach for managing HCC. Proton beam therapy (PBT) offers dosimetric advantages over X-ray therapy, with superior physical properties known as the Bragg peak. PBT holds promise for reducing hepatotoxicity and allowing safe dose-escalation to the tumor. It has been tried in various clinical conditions and has shown promising local tumor control and survival outcomes. A recent phase III trial demonstrated the non-inferiority of PBT in local tumor control compared to current standard radiofrequency ablation in early-stage HCC. PBT also tended to show more favorable outcomes compared to transarterial chemoembolization in the intermediate stage, and has proven effective in-field disease control and safe toxicity profiles in advanced HCC. In this review, we discuss the rationale, clinical studies, optimal indication, and future directions of PBT in HCC treatment.

Hepatic Resection vs Particle Therapy as an Initial Treatment for Single Hepatocellular Carcinoma: Bi-institutional Propensity Score-Matched Analysis

BACKGROUND

Curative treatment for hepatocellular carcinoma (HCC) is limited to hepatic resection (HR), radiofrequency ablation, and liver transplantation, but the value of particle therapy (PT) as an initial treatment remains unclear. This study aimed to compare the outcomes of HR and PT for single HCC.

STUDY DESIGN

A total of 554 patients with single HCC without vascular invasion were enrolled from January 2000 to December 2015. Patients underwent either HR (n = 279) or PT (n = 275) as initial treatments. A one-to-one propensity score-matching analysis was performed to evaluate the overall survival (OS) and progression-free survival after dividing patients according to liver function as assessed by the modified albumin-bilirubin grade.

RESULTS

The median OS (130 vs 85 months, p = 0.001) and progression-free survival (47 vs 30 months HR, p = 0.004) of HR were also significantly better than that of PT in the propensity score-matching cohort with modified albumin-bilirubin grade 1/2a (n = 145 per group). Meanwhile, in a propensity score-matching cohort with modified albumin-bilirubin grade 2b/3 (n = 53 per group), there were no significant differences in median OS and progression-free survival between HR and PT.

CONCLUSIONS

HR may be preferable as an initial treatment for patients with single HCC without vascular invasion, especially those with preserved liver function. PT can be an acceptable alternative to HR for patients without surgical indication and/or impaired liver function.

Proton Beam Therapy and Photon-Based Magnetic Resonance Image-Guided Radiation Therapy: The Next Frontiers of Radiation Therapy for Hepatocellular Carcinoma

External beam radiation therapy (EBRT) has increasingly been utilized in the treatment of hepatocellular carcinoma (HCC) due to technological advances with positive clinical outcomes. Innovations in EBRT include improved image guidance, motion management, treatment planning, and highly conformal techniques such as intensity-modulated radiation therapy (IMRT) and stereotactic body radiation therapy (SBRT). Moreover, proton beam therapy (PBT) and magnetic resonance image-guided radiation therapy (MRgRT) have expanded the capabilities of EBRT. PBT offers the advantage of minimizing low- and moderate-dose radiation to the surrounding normal tissue, thereby preserving uninvolved liver and allowing for dose escalation. MRgRT provides the advantage of improved soft tissue delineation compared to computerized tomography (CT) guidance. Additionally, MRgRT with online adaptive therapy is particularly useful for addressing motion not otherwise managed and reducing high-dose radiation to the normal tissue such as the stomach and bowel. PBT and online adaptive MRgRT are emerging technological advancements in EBRT that may provide a significant clinical benefit for patients with HCC.

Treatment and the prognosis of hepatocellular carcinoma in Asia

Hepatocellular carcinoma is the most common type of malignant tumour in Asia. Treatment is decided according to the staging system with information on tumour burden and liver function. The Barcelona Clinic Liver Cancer staging system is the most commonly used staging system for the selection of appropriate treatments worldwide, and although it is highly evidenced-base, it has very strict guidelines for treatment. In Asian countries, many efforts have been made to expand the indications of each treatment and combination therapies as well as alternative therapies for better outcomes. The guidelines in Asia are less evidence-based than those in Western countries. More aggressive treatments for hepatocellular carcinoma are generally employed in the guidelines of Asian countries. Surgical resection is frequently employed for selected hepatocellular carcinoma patients with the Barcelona Clinic Liver Cancer stages B and C, and combination therapies are sometimes selected, which are contrary to the recommendations of American and European association for the study of the liver guidelines. Recently, a paradigm shift in treatments for advanced hepatocellular carcinoma has occurred with molecular targeted agents, antibodies and immune checkpoint inhibitors in Asia. Atezolizumab+bevacizumab therapy has become the first-line systemic treatment ineligible for radical treatment or transarterial chemoembolization in Asian countries. The overall survival of patients with hepatocellular carcinoma varies substantially across Asia. Taiwan and Japan have the best clinical outcomes for patients with hepatocellular carcinoma worldwide. Intensive surveillance programmes and the development of radical and non-radical treatments are indispensable for the improvement of prognosis in patients with hepatocellular carcinoma.

Proton Therapy in the Management of Hepatocellular Carcinoma

Simple Summary

Radiation therapy is among the locoregional therapy modalities used to treat unresectable or medically inoperable hepatocellular carcinoma (HCC). Proton radiation therapy plays a major role in the treatment of HCC, especially when liver toxicity is a concern. The aim of this review is to provide a concise and comprehensive summary on the use of proton therapy in the management of HCC.

Abstract

Proton radiation therapy plays a central role in the treatment of hepatocellular carcinoma (HCC). Because of the near-zero exit dose and improved sparing of normal liver parenchyma, protons are being used even in challenging scenarios, including larger or multifocal liver tumors, and those associated with vascular tumor thrombus. There is a mounting level of evidence that suggests that protons are superior to photons in terms of survival and toxicity outcomes, specifically the progression to liver failure. A randomized controlled trial comparing protons to photons is currently underway to verify this hypothesis.

Who Will Benefit from Charged-Particle Therapy?

Charged-particle therapy (CPT) such as proton beam therapy (PBT) and carbon-ion radiotherapy (CIRT) exhibit substantial physical and biological advantages compared to conventional photon radiotherapy. As it can reduce the amount of radiation irradiated in the normal organ, CPT has been mainly applied to pediatric cancer and radioresistent tumors in the eloquent area. Although there is a possibility of greater benefits, high set-up cost and dearth of high level of clinical evidence hinder wide applications of CPT. This review aims to present recent clinical results of PBT and CIRT in selected diseases focusing on possible indications of CPT. We also discussed how clinical studies are conducted to increase the number of patients who can benefit from CPT despite its high cost.

Survival and morbidity following stereotactic radiotherapy of hepatocellular carcinoma: a ten-year, single institution experience

BACKGROUND AND AIM

Stereotactic ablative body radiotherapy (SABR) is an emerging treatment option in hepatocellular carcinoma (HCC) in patients ineligible for other local ablative therapies. This study reports on the safety and efficacy of SABR in a Danish cohort of HCC patients.

MATERIALS AND METHODS

Between January 2009 and December 2018, 28 patients with HCCs were treated with SABR at our institution. The primary endpoint of this retrospective study was local control; secondary endpoints were progression-free survival, overall survival and toxicity.

RESULTS

In 28 patients, 32 tumors (median size 3.7 cm, range 1.4-6.8 cm) were treated. The median follow-up time was 16 months. Most patients (68%) received previous liver-directed treatments. A dose of 48 Gy in three or six fractions were given to 43% of the patients. Grad 1 or 2 toxicity was reported in 13 patients (46%), whereas 4 patients (14%) needed hospitalization (grade 3). One-year local control and overall survivals were 90% and 71%, respectively. One-year progression-free survival was 32%, and 65% of patients with disease progression received further HCC therapy. In univariate analysis, none of the examined factors predicted recurrence or overall survival.

CONCLUSION

SABR provides high local control to inoperable HCC. SABR can be delivered safely even after previous liver-directed therapies and subsequent therapies are feasible after treatment with SABR. Despite excellent local control, disease progression outside of the irradiated site remains prominent. Further studies are warranted to examine combined therapy approaches to maximize disease control.

External Beam Radiotherapy for Hepatocellular Carcinoma: a Review of the Current Guidelines in the East and the West

The incidence of hepatocellular carcinoma (HCC) is geographically heterogeneous depending on the underlying liver disease. Moreover, the decisions and recommendations about standard treatments differ between countries, especially between the East and the West. Because of the complexity of treatment decisions for the management of HCC, a multidisciplinary approach is recommended to maximize the therapeutic efficacy. External beam radiotherapy (RT) has been increasingly used to manage HCC when recommended treatments cannot be applied in real-world clinical practice. However, Western guidelines for the management of HCC do not recommend RT as a treatment option due to the lack of clinical evidence. RT has often been used more in Eastern countries than in Western countries; hence, it is necessary to review both Eastern and Western guidelines for HCC treatment regarding the recommendations about RT. In this study, the comments and potential roles of external beam RT are summarized from several treatment guidelines for the management of HCC.

Percutaneous microwave ablation applications for liver tumors: recommendations for COVID-19 patients

Microwave ablation (MWA) is an alternative locoregional therapy to surgical resection of solid tumors in the treatment of malignancies, and is widely used for hepatic tumors. It has a slightly higher overall survival (OS) rate compared to external beam radiation therapy (EBRT), and proton beam therapy (PBT), and better long-term recurrence-free OS rate compared to radiofrequency ablation (RFA). In this paper, current commercial devices, most recent noncommercial designs, and the principles behind them alongside the recently reported developments and issues of MWA are reviewed. The paper also provides microscopic insights on effects of microwave irradiation in the body. Our review shows that MWA is a safe and effective, minimally invasive method with high ablation completion rates. However, for large tumors, the completion rates slightly decrease, and recurrences increase. Thus, for large tumors we suggest using a cooled shaft antenna or multiple antenna placements. Comparisons of the two common ablation frequencies 915 MHz and 2.45 GHz have shown inconsistent results due to non-identical conditions. This review suggests that 915 MHz devices are more effective for ablating large tumors and the theory behind MWA effects corroborates this proposition. However, for small tumors or tumors adjacent to vital organs, 2.45 GHz is suggested due to its more localized ablation zone. Among the antenna designs, the double-slot antenna with a metallic choke seems to be more effective by localizing the radiation around the tip of the antenna, while also preventing backward radiation towards the skin. The review also pertains to the use of MWA in COVID-19 patients and risk factors associated with the disease. MWA should be considered for COVID-19 patients with hepatic tumors as a fast treatment with a short recovery time. As liver injury is also a risk due to COVID-19, it is recommended to apply liver function tests to monitor abnormal levels in alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin, and other liver function indicators.

The impact of different setup methods on the dose distribution in proton therapy for hepatocellular carcinoma

Purpose

To investigate the impact of different setup methods, vertebral body matching (VM), diaphragm matching (DM), and marker matching (MM), on the dose distribution in proton therapy (PT) for hepatocellular carcinoma (HCC).

Materials and Methods

Thirty‐eight HCC lesions were studied retrospectively to assess changes in the dose distribution on two computed tomography (CT) scans. One was for treatment planning (1st‐CT), and the other was for dose confirmation acquired during the course of PT (2nd‐CT). The dose coverage of the clinical target volume (CTV‐D₉₈) and normal liver volume that received 30 Gy relative biological effectiveness (RBE) (liver‐V₃₀) were evaluated under each condition. Initial treatment planning on the 1st‐CT was defined as reference, and three dose distributions recalculated using VM, DM, and MM on the 2nd‐CT, were compared to it, respectively. In addition, the relationship between the CTV‐D₉₈ of each method and the distance between the center of mass (COM) of the CTV and the right diaphragm top was evaluated.

Results

For CTV‐D₉₈, significant differences were observed between the reference and VM and DM, respectively (P = 0.013, P = 0.015). There were also significant differences between MM and VM and DM, respectively (P = 0.018, P = 0.036). Regarding liver‐V₃₀, there was no significant difference in any of the methods, and there were no discernable difference due to the different setup methods. In DM, only two out of 34 cases with a distance from right diaphragm top to COM of CTV of 90 mm or less that CTV‐D₉₈ difference was 5% or more and CTV‐D₉₈ was worse than VM were confirmed.

Conclusion

Although MM is obviously the most effective method, it is suggested that DM may be particularly effective in cases where the distance from right diaphragm top to COM of CTV of 90 mm or less.

Capacity of proton beams in preserving normal liver tissue during proton beam therapy for hepatocellular carcinoma

Unirradiated liver volume (ULV) preservation rate is an important factor associated with radiation-induced liver disease (RILD) in patients with hepatocellular carcinoma (HCC) undergoing proton beam therapy (PBT). The purpose of this study is to identify the predictors for ULV preservation and quantify the capacity of proton beams in normal liver sparing during PBT. We reviewed planning data of 92 patients with single intrahepatic HCC tumors undergoing PBT. The potential clinical and planning factors that may affect ULV preservation were involved in multiple linear regression for ULV preservation rate. The significant factors were determined to be predictors and their influences were quantified. The median ULV preservation rate was 62.08%. All the assessed clinical factors showed significant effects on ULV preservation rate: clinical target volume (CTV), P < 0.001; portal vein tumor thrombosis (PVTT), P = 0.010; left lobe tumor, P = 0.010. In contrast, none of the planning factors demonstrated significance. The coefficients of significant factors in multiple linear regression were 60.85 for intercept, -0.02 for CTV, -9.01 for PVTT and 8.31 for left lobe tumors. The capacity of proton beams to spare normal liver tissue during PBT for HCC is mainly affected by clinical factors. The baseline of the ULV preservation rate is 60.85%, decreasing 0.02% with each milliliter of CTV increase and 9.01% for tumors with PVTT, and increasing 8.31% for tumors limited to the left lobe. Further clinical studies should be carried out to correlate our dosimetric findings with clinical outcomes.

Hypofractionated proton beam radiotherapy in patients with unresectable liver tumors: multi-institutional prospective results from the Proton Collaborative Group

Background

Recent advances in radiotherapy techniques have allowed ablative doses to be safely delivered to inoperable liver tumors. In this setting, proton beam radiotherapy (PBT) provides the means to escalate radiation dose to the target volume while sparing the uninvolved liver. This study evaluated the safety and efficacy of hypofractionated PBT for liver tumors, predominantly hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (ICC).

Methods

We evaluated the prospective registry of the Proton Collaborative Group for patients undergoing definitive PBT for liver tumors. Demographic, clinicopathologic, toxicity, and dosimetry information were compiled.

Results

To date, 63 patients have been treated at 9 institutions between 2013 and 2019. Thirty (48%) had HCC and 25 (40%) had ICC. The median dose and biological equivalent dose (BED) delivered was 58.05 GyE (range 32.5–75) and 80.5 GyE (range 53.6–100), respectively. The median mean liver BED was 13.9 GyE. Three (4.8%) patients experienced at least one grade ≥ 3 toxicity. With median follow-up of 5.1 months (range 0.1–40.8), the local control (LC) rate at 1 year was 91.2% for HCC and 90.9% for ICC. The 1-year LC was significantly higher (95.7%) for patients receiving BED greater than 75.2 GyE than for patients receiving BED of 75.2 GyE or lower (84.6%, p = 0.029). The overall survival rate at 1 year was 65.6% for HCC and 81.8% for ICC.

Conclusions

Hypofractionated PBT results in excellent LC, sparing of the uninvolved liver, and low toxicity, even in the setting of dose-escalation. Higher dose correlates with improved LC, highlighting the importance of PBT especially in patients with recurrent or bulky disease.

Role of External Beam Radiotherapy in Hepatocellular Carcinoma

External beam radiotherapy (EBRT) has improved efficacy and safety with advancements in technology and techniques. EBRT plays an important role in management of hepatocellular carcinoma (HCC). In resectable cases, EBRT serves as a bridge to transplantation or improves local control through adjuvant radiotherapy. In unresectable patients, EBRT offers high local control rates. In metastatic settings, EBRT provides effective palliation. This review presents an overview of radiotherapy treatment modalities used for HCC, current treatment guidelines for the role of EBRT in HCC, clinical outcomes between various EBRT approaches and other locoregional treatments for HCC, and the future role of EBRT for HCC.

Do Biliary Complications after Proton Beam Therapy for Perihilar Hepatocellular Carcinoma Matter?

We aimed to evaluate the biliary complications and efficacy of proton beam therapy (PBT) for hepatocellular carcinoma (HCC). We retrospectively analyzed 167 patients who received PBT with ≥ 75 GyRBE of biological effective dose with 𝛼/β = 10 for primary HCC. The perihilar region was defined as a 1-cm area extending from the right, left, and common hepatic ducts, including the gallbladder and cystic duct. PBT-related biliary complications were defined as follows: significant elevation in bilirubin level to > 3.0 mg/dL; elevation to more than twice of the baseline level after the completion of PBT; or newly developed radiological biliary abnormalities, which were not caused by HCC progression, comorbidities, or other treatments. Eighty (47.9%) had perihilar HCC. PBT-related events occurred in seven (4.2%), three of whom had perihilar HCC. Radiologic biliary abnormalities developed in 12 patients (7.2%); however, no events were PBT-related. All patients who experienced PBT-related biliary complications had underlying liver cirrhosis. The albumin-bilirubin grade was identified as an independent factor associated with PBT-related biliary complications. PBT at the current dose showed a low rate of PBT-related biliary complications even for patients with perihilar HCC. PBT for HCC patients with risk factors requires attention to reduce PBT-related biliary complications.

Clinical results of active scanning proton therapy for primary liver tumors

BACKGROUND

Evidence for the efficacy of radiation therapy for primary liver cancer is growing. In this context, proton therapy (PT) can potentially improve the therapeutic ratio, as demonstrated by recent clinical studies. Here we report the first European clinical experience on the use of PT for primary liver cancer.

METHODS

All patients treated for primary liver cancer in our center entered the analysis. Patients were simulated during deep expiration breath-hold. A 15-fraction treatment schedule was adopted using active scanning PT. Clinical outcome and toxicity were retrospectively analyzed.

RESULTS

Between January 2018 and December 2019, 18 patients were treated. Fourteen patients had hepatocellular carcinoma (HCC), three patients had intrahepatic cholangiocarcinoma (ICC), and one patient had synchronous ICC-HCC. The Child-Pugh score was A5 in the majority of patients with HCC (71.4%). Median prescription dose was 58.05 Gy (range, 50.31-67.5). Median follow-up was 10 months (range, 1-19). The majority of deaths occurred from liver tumor progression. One-year overall survival (OS) was 63%. A significant correlation between worse OS and patient performance status, vascular invasion, and tumor stage was recorded. One-year local control was 90%. Toxicity was low, with a decrease in Child-Pugh score ⩾2 points detected in one patient. No cases of classic radiation-induced liver disease occurred.

CONCLUSIONS

Our initial results of active scanning PT for primary liver cancer demonstrated the feasibility, safety, and effectiveness of this advanced technique in this setting. The potential of the combination of PT with other locoregional therapies is under evaluation.

Phase II Study of Hypofractionated Proton Beam Therapy for Hepatocellular Carcinoma

Background: Proton beam has an excellent depth dose distribution due to its unique physical properties, and thus proton beam therapy (PBT) has been tried and showed promising outcomes in hepatocellular carcinoma (HCC). The purpose of this phase II study is to evaluate the efficacy of hypofractionated PBT in HCC.

Methods: The eligibility criteria for this study were as follows: patients with HCC lesion(s) who were failed after, were difficult to treat with, or refused to other local treatments; tumor size and number of ≤7 and ≤2 cm, respectively, and HCC lesion(s) of ≥2 cm from gastrointestinal organs; Child–Pugh score of ≤7; Eastern Cooperative Oncology Group performance status ≤1; and age ≥18 years. The prescribed dose of PBT was 70 Gy equivalent in 10 fractions. The primary endpoint was 3-year local progression-free survival (LPFS) rate.

Results: Forty-five patients were prospectively enrolled, and there were 35 men and 10 women with a median age of 63 years (range, 46–78 years). Thirty-seven patients had recurrent and/or residual disease, and eight patients had treatment-naive disease. All patients received the planned treatments without treatment interruption, and grade ≥3 acute toxicity did not occur. The median follow-up duration was 35.1 months (range, 11.2–56.3 months) and local progression occurred in two patients (8.7%). The 3-year rates of LPFS and overall survival (OS) were 95.2% (95% confidence interval [CI], 89.1%−100%) and 86.4% (95% CI, 72.9–99.9%), respectively.

Conclusion: Hypofractionated PBT showed promising LPFS and OS, and further studies are warranted to compare PBT with other local modalities.

Proton beam therapy for liver cancers

Proton beam therapy (PBT) delivers less dose to nearby normal organs compared to X-ray therapy (XRT), which is particularly relevant for treating liver cancers given that both mean and low liver dose are among the most significant predictors of radiation induced liver disease (RILD). High-dose PBT has been shown to achieve excellent long-term tumor control with minimal toxicity in hepatocellular carcinoma (HCC) patients. Increasing data support ablative PBT for patients with unresectable cholangiocarcinoma or liver metastases, especially those with larger tumors not suitable for XRT.

Proton Beam Therapy in Liver Malignancies

PURPOSE OF REVIEW

Proton beam therapy (PBT) allows for improved sparing of surrounding normal tissues compared with X-ray-based radiation therapy. This is especially important in the setting of liver malignancies, where an increase in integral dose leads to a higher risk of radiation-induced liver disease (RILD) as well as close proximity to vital gastrointestinal (GI) organs.

RECENT FINDINGS

We have data from multiple centers demonstrating that PBT can safely deliver high, ablative doses of radiation therapy conferring excellent local control with good tolerance of treatment. PBT is an effective treatment with longstanding evidence of efficacy that is increasing in availability.

Three cases of hepatocellular carcinoma treated 4 times with proton beams

HCC may recur following surgery or radiofrequency ablation. Proton beam therapy (PBT) is a type of radiotherapy that achieves excellent local control of HCC without severe toxicity. The present study reported the long-term outcome of 3 HCC patients who each received 4 repeat courses of PBT. All patients had a hepatitis B or C viral infection. A total of 14 lesions were treated using a curative PBT protocol and irradiated liver volumes in each treatment were 7-50% of the total liver volume. Liver function in all cases was considerably preserved until the last follow-up and patient survival was 51-107 months from the first PBT with no local recurrence observed in the 14 lesions. The presented cases indicated that repeated PBT is an effective treatment option for recurrent HCC due to reduced liver damage and superior local treatment compared with other treatment options such as transarterial chemoembolization.

Indicator for local recurrence of hepatocellular carcinoma after proton beam therapy: analysis of attenuation difference between the irradiated tumor and liver parenchyma on contrast enhancement CT

OBJECTIVES

We aimed to identify dynamic CT features that can be used for prediction of local recurrence of hepatocellular carcinoma (HCC) after proton beam therapy (PBT).

METHODS

We retrospectively retrieved CT scans of patients with PBT-treated HCC, taken between January 2004 and December 2016. 17 recurrent lesions and 34 non-recurrent lesions were retrieved. The attenuation difference between irradiated tumor and irradiated parenchyma (AD_HCC-IP) was compared in the two groups by using the Mann-Whitney U test. Cut-off value of AD_HCC-IP was estimated by using the Youden index.

RESULTS

The follow-up time after PBT initiation ranged from 374 to 2402 days (median, 1069 days) in recurrent lesions, and 418 to 2923 days (median, 1091.5 days) in non-recurrent lesions (p = 0.892). The time until appearance of local recurrence after PBT initiation ranged from 189 to 2270 days (median, 497 days). AD_HCC-IP of recurrent lesions [mean, -21.8 Hounsfield units (HU); from -95 to -31 HU] was significantly greater than that of non-recurrent lesions (mean, -51.7 HU; from -117 to -12 HU) at 1-2 years in portal venous phase (p = 0.039). 5-year local tumor control rates were 0.93 and 0.56 in lesions with AD_HCC-IP at 1-2 years in PVP < -55 and ≥ -55 HU, respectively.

CONCLUSION

The attenuation difference between irradiated HCC and irradiated liver parenchyma in portal venous phase at 1-2 years after PBT can predict long-term local recurrence of HCC after treatment.

ADVANCES IN KNOWLEDGE

We identified a cut-off value for contrast enhancement of HCC after PBT that could predict future local recurrence.

Improved clinical outcome using transarterial chemoembolization combined with radiofrequency ablation for patients in Barcelona clinic liver cancer stage A or B hepatocellular carcinoma regardless of tumor size: results of a single-center retrospective case control study

Background

To determine the safety and efficacy of transarterial chemoembolization (TACE) combined with radiofrequency ablation (hereafter, TACE-RFA) in treating Barcelona Clinic Liver Cancer (BCLC) Stage A or B (hereafter, BCLC A/B) hepatocellular carcinoma (HCC) patients, and to explore the range of tumor sizes suitable for combination therapy.

Methods

This retrospective study assessed the consecutive medical records of HCC patients with BCLC A/B who received TACE-RFA or TACE from September 2009 to September 2018. Progression-free survival (PFS), overall survival (OS), therapeutic response, and complications were compared between the two groups.

Results

Among 2447 patients who received TACE-RFA or TACE, 399 eligible patients were enrolled in our study, including 128 patients in the TACE-RFA group and 271 patients in the TACE group. Compared with the TACE group, the PFS and OS rates of 1,3,5,8 years in the TACE-RFA group were significantly better, with higher objective tumor regression rate and better disease control rate. RFA treatment did not increase the risk of death in patients with HCC, and both liver subcapsular hematoma and bile duct injury were improved by symptomatic treatment. Serum α-fetoprotein level and treatment method were important independent prognostic factors for OS, whereas albumin, hepatitis B and treatment method were important independent prognostic factors for PFS. Subgroup analysis showed that patients in the TACE-RFA group always showed better OS and PFS.

Conclusions

TACE-RFA had an advantage over TACE alone in prolonging PFS and improving OS in HCC patients with BCLC A/B, and can benefit patients regardless of tumor size.

A comparison of the outcomes between surgical resection and proton beam therapy for single primary hepatocellular carcinoma

PURPOSE

There are many treatment choices for hepatocellular carcinoma (HCC), one of which is proton beam therapy (PBT). The purpose of this study was to compare surgical resection (SR) and PBT to clarify the prognostic factors for operable HCC based on a single institution's database.

METHODS

Patients with single primary nodular HCC ≤ 100 mm without vessel invasion on pretreatment imaging were divided into the SR group and PBT group. In the PBT group, the patients with unresectable HCC due to their liver function and/or performance status were excluded.

RESULTS

There were 314 and 31 patients who underwent SR and PBT, respectively. The median survival time in the SR group was significantly better than in the PBT group (104.1 vs. 64.6 months, p = 0.008). Regarding the relapse-free survival (RFS), there was no significant difference between the SR and PBT groups (33.8 vs. 14.0 months, p = 0.099).

CONCLUSION

The RFS was comparable between the PBT and SR groups. However, the PBT group had a significantly worse overall survival than the SR group. SR may therefore be favorable as an initial treatment for HCC compared to PBT.

Proton beam therapy for tumors of the upper abdomen

Proton radiotherapy has clear dosimetric advantages over photon radiotherapy. In contrast to photons, which are absorbed exponentially, protons have a finite range dependent on the initial proton energy. Protons therefore do not deposit dose beyond the tumor, resulting in great conformality, and offers the promise of dose escalation to increase tumor control while minimizing toxicity. In this review, we discuss the rationale for using proton radiotherapy in the treatment of upper abdominal tumors-hepatocellular carcinomas, cholangiocarcinomas and pancreatic cancers. We also review the clinical outcomes and technical challenges of using proton radiotherapy for the treatment of these malignancies. Finally, we discuss the ongoing clinical trials implementing proton radiotherapy for the treatment of primary liver and pancreatic tumors.

Fitting the Generalized Target Model to Cell Survival Data of Proton Radiation Reveals Dose-Dependent RBE and Inspires an Alternative Method to Estimate RBE in High-Dose Regions

The imprecise estimation of the relative biological effectiveness (RBE) of proton radiation has been one of the main challenges for further calculating the biologically effective dose in proton therapy. Since dose levels can greatly influence the proton RBE, the relationship between the two should be clarified first. In addition, since the dose-response curves are usually too complex to readily assess RBE in high-dose regions, a reliable and simple method is needed to predict the RBE of proton radiation accurately in clinically relevant doses. The standard linear-quadratic (LQ) model is widely used to determine the RBE of particles for clinical applications. However, there has been some debate over its use when modeling the cell survival curves in high-dose regions, since those survival curves usually show linear behavior in the semilogarithmic plot. By considering both cellular repair effects and indirect effects of radiation, we have proposed a generalized target model with linear-quadratic linear (LQL) characteristics. For the more accurate evaluation of proton RBE in radiotherapy, here we used this generalized target model to fit the cell survival data in V79 and C3H 10T1/2 cells exposed to proton radiation with different LETs. The fitting results show that the generalized target model works as well as the LQ model in general. Based on the fitting parameters of the generalized target model, the RBE of six given doses D_T (RBE_T) could be calculated in the corresponding cell lines with different LETs. The results show that the RBE_T gradually decreases with increased dose in both cell types. In addition, inspired by the calculation method of the maximum values of RBE (RBE_M) in the low-dose region, a novel method was proposed for estimating the RBE in the high-dose region (RBE_H) based on the slope ratio of the dose-response curves in this region. Linear regression analysis indicated a significant linear correlation between the proposed RBE_H and the RBE_T in high-dose regions, which suggests that the current method can be used as an alternative tool, which is both simple and robust, to estimate RBE in high-dose regions.

Hypofractionated particle beam therapy for hepatocellular carcinoma-a brief review of clinical effectiveness

Hepatocellular carcinoma (HCC) is the fifth most common malignancy and the second leading cause of cancer mortality worldwide. The cornerstone to improving the prognosis of HCC patients has been the control of loco-regional disease progression and the lesser toxicities of local treatment. Although radiotherapy has not been considered a preferred treatment modality for HCC, charged particle therapy (CPT), including proton beam therapy (PBT) and carbon ion radiotherapy (CIRT), possesses advantages (for example, it allows ablative radiation doses to be applied to tumors but simultaneously spares the normal liver parenchyma from radiation) and has emerged as an alternative treatment option for HCC. With the technological advancements in CPT, various radiation dosages of CPT have been used for HCC treatment via CPT. However, the efficacy and safety of the evolving dosages remain uncertain. To assess the association between locoregional control of HCC and the dose and regimen of CPT, we provide a brief overview of selected literature on dose regimens from conventional to hypofractionated short-course CPT in the treatment of HCC and the subsequent determinants of clinical outcomes. Overall, CPT provides a better local control rate compared with photon beam therapy, ranging from 80% to 96%, and a 3-year overall survival ranging from 50% to 75%, and it results in rare grade 3 toxicities of the late gastrointestinal tract (including radiation-induced liver disease). Regarding CPT for the treatment of locoregional HCC, conventional CPT is preferred to treat central tumors of HCC to avoid late toxicities of the biliary tract. In contrast, the hypo-fractionation regimen of CPT is suggested for treatment of larger-sized tumors of HCC to overcome potential radio-resistance.

Design and commissioning of an image-guided small animal radiation platform and quality assurance protocol for integrated proton and x-ray radiobiology research

Small animal x-ray irradiation platforms are expanding the capabilities and future pathways for radiobiology research. Meanwhile, proton radiotherapy is transitioning to a standard treatment modality in the clinician’s precision radiotherapy toolbox, highlighting a gap between state-of-the-art clinical radiotherapy and small animal radiobiology research. Comparative research of the biological differences between proton and x-ray beams could benefit from an integrated small animal irradiation system for in vivo experiments and corresponding quality assurance (QA) protocols to ensure rigor and reproducibility. The objective of this study is to incorporate a proton beam into a small animal radiotherapy platform while implementing QA modelled after clinical protocols.

A 225 kV x-ray small animal radiation research platform (SARRP) was installed on rails to align with a modified proton experimental beamline from a 230 MeV cyclotron-based clinical system. Collimated spread out Bragg peaks (SOBP) were produced with beam parameters compatible with small animal irradiation. Proton beam characteristics were measured and alignment reproducibility with the x-ray system isocenter was evaluated. A QA protocol was designed to ensure consistent proton beam quality and alignment. As a preliminary study, cellular damage via γ-H2AX immunofluorescence staining in an irradiated mouse tumor model was used to verify the beam range in vivo.

The beam line was commissioned to deliver Bragg peaks with range 4–30 mm in water at 2 Gy min⁻¹. SOBPs were delivered with width up to 25 mm. Proton beam alignment with the x-ray system agreed within 0.5 mm. A QA phantom was created to ensure reproducible alignment of the platform and verify beam delivery. γ-H2AX staining verified expected proton range in vivo.

An image-guided small animal proton/x-ray research system was developed to enable in vivo investigations of radiobiological effects of proton beams, comparative studies between proton and x-ray beams, and investigations into novel proton treatment methods.

Angiographic Findings in Patients with Hepatocellular Carcinoma Previously Treated Using Proton Beam Therapy

Given the growing interest in using proton beam therapy (PBT) for hepatocellular carcinoma (HCC), it is possible that transarterial chemoembolization (TACE) could be used for selected patients who have previously undergone PBT. However, these cases can be technically challenging to treat and require appropriate preparation. Thus, we aimed to identify angiographic findings in this setting. We retrospectively identified 31 patients (28 men and 3 women, mean age: 69 years, range: 43–84 years) who underwent hepatic angiography plus TACE or transarterial infusion chemotherapy (TAI) for HCC that recurred after PBT (July 2007 to June 2018). We discovered four angiographic findings, which we speculate were related to the previous PBT. 18 patients experienced recurrence in the irradiated field, and 13 patients experienced recurrence outside the irradiated field. 29 patients underwent TACE and only 2 patients underwent TAI. The mean number of previous PBT treatments was 1.3 ± 0.6 (range: 1–4). The median interval from the earliest PBT treatment to hepatic angiography was 559 days (range: 34–5,383 days), and the median interval from the latest PBT treatment to hepatic angiography was 464 days (range: 34–5,383 days). Abnormal staining of the irradiated liver parenchyma was observed in 22 patients, which obscured the angiographic tumor staining in 4 patients. Development of a tortuous tumor feeder vessel was observed in 13 patients. Development of an extrahepatic collateral pathway was observed in 7 patients. Development of an arterioportal or arteriovenous shunt was observed in 4 patients. Based on these findings, we conclude that PBT was associated with various angiographic findings during subsequent transarterial chemotherapy for recurrent HCC, and familiarity with these findings will be important in developing appropriate treatment plans.

Role of Radiotherapy in the Treatment of Hepatocellular Carcinoma

The role of radiotherapy in the treatment of hepatocellular carcinoma (HCC) has evolved over the past few decades with the advancement of technology and improved imaging. Radiotherapy can offer high local control rates in unresectable HCC, including cases with major vascular involvement, and can provide a modality to help bridge patients to potentially curative resection or transplantation. In metastatic cases, radiotherapy can provide good palliation. This review focuses on the common radiotherapy treatment modalities used for HCC, provides outcome comparisons of these radiotherapy techniques to outcomes with other treatment modalities for HCC, and highlights the discrepancy of the role of radiotherapy in HCC amongst the current available treatment guidelines.

Stereotactic Body Radiation Therapy: A New Strategy for Loco-Regional Treatment for Hepatocellular Carcinoma While Awaiting Liver Transplantation

BACKGROUND

Trans-arterial chemoembolization and radiofrequency ablation are commonly used for control of hepatocellular carcinoma (HCC) on liver transplant (LTx) waiting list. Stereotactic body radiation therapy (SBRT) was introduced to our institution for HCC as a bridging or downsizing therapy to LTx.

PATIENTS AND METHODS

Twenty-five HCC lesions in 22 patients were treated with SBRT while waiting for LTx from January 2010 to December 2015. Nineteen of these patients received deceased donor LTx. SBRT was defined as 40-50 Gy delivered in 4-6 fractions. Pre- and post-liver transplant outcome were analyzed in addition to the dropout rate and tumor response to SBRT.

RESULTS

Median size of original tumors was 3.2 cm (2.0-8.9), and median size of tumor after SBRT was significantly smaller at 0.9 cm (0-3.2) in the explanted livers (p < 0.01). The dropout rate was 9%, and they were only downsized patients outside of Milan criteria. Liver disease did not progress between pre- and post-SBRT except one patient. Twenty-eight percent of treated HCCs showed complete pathologic response, and 22% had extensive partial response with some residual tumor. No HCC recurrence was experienced after LTx.

CONCLUSION

SBRT is indicated to be safe, effective treatment for HCC on LTx waiting list, and it leads to satisfactory post-liver transplant outcomes.

Predictors of Radiation-Induced Liver Disease in Eastern and Western Patients With Hepatocellular Carcinoma Undergoing Proton Beam Therapy

PURPOSE

To identify predictors of radiation-induced liver disease (RILD) in patients with hepatocellular carcinoma (HCC) treated with proton beam therapy (PBT).

METHODS

This multicenter study included 136 patients with HCC (eastern, n = 102; western, n = 34) without evidence of intrahepatic tumor progression after PBT. The RILD was defined as ascites with alkaline-phosphatase abnormality, grade ≥3 hepatic toxicity, or Child-Pugh score worsening by ≥2 within 4 months after PBT completion. The proton doses were converted to equivalent doses in 2-GyE fractions. The unirradiated liver volume (ULV) was defined as the absolute liver volume (LV) receiving <1 GyE; the standard liver volume (SLV) was calculated using body surface area. Possible correlations of clinicodosimetric parameters with RILD were examined.

RESULTS

The mean pretreatment LV was 85% of SLV, and patients with a history of hepatectomy (P < .001) or hepatitis B virus infection (P = .035) had significantly smaller LV/SLV. Nineteen (14%) patients developed RILD. Multivariate logistic regression analysis identified ULV/SLV (P = .001), gross tumor volume (P = .001), and Child-Pugh classification (P = .002) as independent RILD predictors, and mean liver dose and target-delivered dose were not associated with RILD occurrence. A "volume-response" relationship between ULV/SLV and RILD was consistently observed in both eastern and western cohorts. In Child-Pugh class-A patients whose ULV/SLV were ≥50%, 49.9%-40%, 39.9%-30% and <30%, the RILD incidences were 0%, 6%, 16%, and 39% (P < .001), respectively. For the Child-Pugh class-B group, the RILD incidences in patients with ≥60%, 59.9%-40%, and <40% of ULV/SLV were 0%, 14%, and 83% (P = .006), respectively.

CONCLUSIONS

The ULV/SLV, not mean liver dose, independently predicts RILD in patients with HCC undergoing PBT. The relative and absolute contraindications for Child-Pugh class-A patient's ULV/SLV are <50% and <30%, and <60% and <40% for Child-Pugh class-B patients, respectively. Our results indicate that the likelihood of hepatic complications for PBT is dictated by similar metrics as that for surgery.

Protons versus Photons for Unresectable Hepatocellular Carcinoma: Liver Decompensation and Overall Survival

PURPOSE

Ablative radiation therapy is increasingly being used for hepatocellular carcinoma (HCC) resulting in excellent local control rates; however, patients without evidence of disease progression often die from liver failure. The clinical benefit of proton- over photon-based radiation therapy is unclear. We therefore sought to compare clinical outcomes of proton versus photon ablative radiation therapy in patients with unresectable HCC.

METHODS AND MATERIALS

This is a single-institution retrospective study of patients treated during 2008 to 2017 with nonmetastatic, unresectable HCC not previously treated with liver-directed radiation therapy and who did not receive further liver-directed radiation therapy within 12 months after completion of index treatment. The primary outcome, overall survival (OS), was assessed using Cox regression. Secondary endpoints included incidence of non-classic radiation-induced liver disease (defined as increase in baseline Child-Pugh score by ≥2 points at 3 months posttreatment), assessed using logistic regression, and locoregional recurrence, assessed using Fine-Gray regression for competing risks. All outcomes were measured from radiation start date.

RESULTS

The median follow-up was 14 months. Of 133 patients with median age 68 years and 75% male, 49 (37%) were treated with proton radiation therapy. Proton radiation therapy was associated with improved OS (adjusted hazard ratio, 0.47; P = .008; 95% confidence interval [CI], 0.27-0.82). The median OS for proton and photon patients was 31 and 14 months, respectively, and the 24-month OS for proton and photon patients was 59.1% and 28.6%, respectively. Proton radiation therapy was also associated with a decreased risk of non-classic radiation-induced liver disease (odds ratio, 0.26; P = .03; 95% CI, 0.08-0.86). Development of nonclassic RILD at 3 months was associated with worse OS (adjusted hazard ratio, 3.83; P < .001; 95% CI, 2.12-6.92). There was no difference in locoregional recurrence, including local failure, between protons and photons.

CONCLUSIONS

Proton radiation therapy was associated with improved survival, which may be driven by decreased incidence of posttreatment liver decompensation. Our findings support prospective investigations comparing proton versus photon ablative radiation therapy for HCC.

Proton beam therapy outcomes for localized unresectable hepatocellular carcinoma

BACKGROUND AND PURPOSE

This study documents the utilization and efficacy of proton beam therapy (PBT) in western patients with localized unresectable hepatocellular carcinoma (HCC).

METHODS AND METHODS

Forty-six patients with HCC, Child-Pugh class of A or B, no prior radiotherapy history, and ECOG performance status 0-2 received PBT at our institution from 2007 to 2016. Radiographic control within the PBT field (local control, LC) and overall survival (OS) were calculated from the start of PBT.

RESULTS

Most (83%) patients had Child-Pugh class A. Median tumor size was 6 cm (range, 1.5-21.0 cm); 22% of patients had multiple tumors and 28% had tumor vascular thrombosis. Twenty-five (54%) patients received prior treatment. Median biologically effective dose (BED) was 97.7 GyE (range, 33.6-144 GyE) administered in 15 fractions. Actuarial 2-year LC and OS rates were 81% and 62% respectively; median OS was 30.7 months. Out-of-field intrahepatic failure was the most common site of disease progression. Patients receiving BED ≥90 GyE had a significantly better OS than those receiving BED <90 GyE (49.9 vs. 15.8 months, p = 0.037). A trend toward 2-year LC improvement was observed in patients receiving BED ≥90 GyE compared with those receiving BED <90 GyE (92% vs. 63%, p = 0.096). On multivariate analysis, higher BED (p = 0.023; hazard ratio = 0.308) significantly predicted improved OS. Six (13%) patients experienced acute grade 3 toxicity.

CONCLUSIONS

High-dose PBT is associated with high rates of LC and OS for unresectable HCC. Dose escalation may further improve outcomes.

Patient specific outcomes of charged particle therapy for hepatocellular carcinoma - A systematic review and quantitative analysis

Hepatocellular carcinoma (HCC) is a raising condition world-wide. Most of patients are ineligible for surgery at diagnosis due to the advanced stage of the disease or poor medical condition of the patient. Charged particle therapy (CPT) is a radiotherapy modality showing promising results. The aim of this systematic review was to summarize current knowledge on patient-specific outcomes of CPT for HCC, including overall survival, local control, the effect of radiation dose and the toxicity burden. The systematic review was performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). After comprehensive database search 17 cohorts (16 studies, 1516 patients) were included into qualitative and quantitative analyses; 11 of 16 studies were retrospective. Eleven studies were on protons, 2 studies were on protons and carbon ions and 4 on carbon ions alone, were identified. Median BED10 (biologically equivalent dose) range was 68.75-122.5 GyE. Mean weighted overall survival across studies was 86%, 62%, 59% and 35% at 1, 2, 3 and 5 years, respectively. Mean weighted local control was 86%, 89%, 87% and 89% at 1, 2, 3 and 5 years, respectively. Adjusted morbidity rates were: 54% for acute G1-2 toxicities and 6% for acute ≥G3 toxicities; 9% for late G1-2 toxicities and less than 4% for late ≥G3 toxicities. There was no treatment-associated mortality. CONCLUSIONS: CPT offers high local control, acceptable overall survival and low post-treatment morbidity. Quality of findings, especially on toxicities, is decreased by incomplete reporting and retrospective designs of available studies. Therefore, there is a strong need for better reporting and prospective studies.

Proton Beam Therapy and Carbon Ion Radiotherapy for Hepatocellular Carcinoma

Charged particle therapy with proton beam therapy (PBT) and carbon ion radiotherapy (CIRT) has emerged as a promising radiation modality to minimize radiation hepatotoxicity while maintaining high rates of tumor local control. Both PBT and CIRT deposit the majority of their dose at the Bragg peak with little to no exit dose, resulting in superior sparing of normal liver tissue. CIRT has an additional biological advantage of increased relative biological effectiveness, which may allow for increased hypofractionation regimens. Retrospective and prospective studies have demonstrated encouragingly high rates of local control and overall survival and low rates of hepatotoxicity with PBT and CIRT. Ongoing randomized trials will evaluate the value of PBT over photons and other standard liver-directed therapies and future randomized trials are needed to assess the value of CIRT over PBT.

Short-course carbon-ion radiotherapy for hepatocellular carcinoma: A multi-institutional retrospective study

BACKGROUND & AIMS

Carbon-ion radiation therapy has shown encouraging results in hepatocellular carcinoma patients in single-centre studies. We evaluated the effectiveness and safety of short-course carbon-ion radiation therapy for hepatocellular carcinoma in a multicentre study conducted by the Japan Carbon Ion Radiation Oncology Study Group.

METHODS

Consecutive hepatocellular carcinoma patients who were treated with carbon-ion radiation therapy in four or fewer fractions at four Japanese institutions between April 2005 and November 2014 were analysed retrospectively. The primary outcome was overall survival; secondary outcomes were local control rate, treatment-related toxicity and radiation-induced liver disease.

RESULTS

A total of 174 patients were included in this study. Prescribed carbon-ion radiation therapy doses were (relative biological effectiveness): 48.0 Gy in two fractions (n = 46), and 52.8 Gy (n = 108) and 60.0 Gy (n = 20) in four fractions. The median follow-up period was 20.3 (range, 2.9-103.5) months. The overall survival and local control rates at 1, 2 and 3 years were 95.4%, 82.5% and 73.3%; and 94.6%, 87.7% and 81.0% respectively. Multivariate analysis revealed that Eastern Cooperative Oncology Group performance status 1-2, Child-Pugh class B, maximum tumour diameter ≥3 cm, multiple tumours and serum alpha foetoprotein level >50 ng/mL were significant prognostic factors of overall survival. No treatment-related death occurred during the follow-up period. Grades 3 or 4 treatment-related toxicities were observed in 10 patients (5.7%); radiation-induced liver disease was observed in three patients (1.7%).

CONCLUSIONS

Short-course carbon-ion radiation therapy is a safe, effective and potentially curative therapy for hepatocellular carcinoma.

A feasibility study of high-dose hypofractionated carbon ion radiation therapy using four fractions for localized hepatocellular carcinoma measuring 3 cm or larger

BACKGROUND AND PURPOSE

To evaluate the safety of carbon-ion radiotherapy (C-ion RT) using 60 Gy (relative biological effectiveness, RBE) in four fractions for patients with hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

The primary outcome was acute toxicities within 90 days. The secondary outcomes were late toxicities, local control, and progression-free survival and overall survival rates. The key inclusion criteria were as follows: (1) 3 cm or larger HCC without major vascular invasion and not adjacent to the alimentary tract; (2) Child-Pugh's grade A/B; and (3) without extrahepatic metastasis.

RESULTS

A total of 21 cases were analyzed between October 2012 and April 2016. The median follow-up period among the 17 survivors was 24.2 (range: 6.3-43.7) months. Grade 3 or higher acute toxicity was not observed, while three (14.3%) of the 21 patients experienced grade 3 late toxicities. The 1- and 2-year local control, progression-free survival, and overall survival rates were 100% and 92.3%, 81.0% and 50.0%, and 90.5% and 80.0%, respectively.

CONCLUSION

C-ion RT using 60 Gy (RBE) in four fractions was safe and achieved promising local tumor control.

Proton therapy for hepatocellular carcinoma: Current knowledges and future perspectives

Hepatocellular carcinoma (HCC) is the second leading cause of cancer-related death, as few patients can be treated with currently available curative local modalities. In patients with HCC where curative modalities are not feasible, radiation therapy (RT) has emerged as an alternative or combination therapy. With the development of various technologies, RT has been increasingly used for the management of HCC. Among these advances, proton beam therapy (PBT) has several unique physical properties that give it a finite range in a distal direction, and thus no exit dose along the beam path. Therefore, PBT has dosimetric advantages compared with X-ray therapy for the treatment of HCC. Indeed, various reports in the literature have described the favorable clinical outcomes and improved safety of PBT for HCC patients compared with X-ray therapy. However, there are some technical issues regarding the use of PBT in HCC, including uncertainty of organ motion and inaccuracy during calculation of tissue density and beam range, all of which may reduce the robustness of a PBT treatment plan. In this review, we discuss the physical properties, current clinical data, technical issues, and future perspectives on PBT for the treatment of HCC.

Respiratory-gated Proton Beam Therapy for Hepatocellular Carcinoma Adjacent to the Gastrointestinal Tract without Fiducial Markers

The efficacy of proton beam therapy (PBT) for hepatocellular carcinoma (HCC) has been reported, but insertion of fiducial markers in the liver is usually required. We evaluated the efficacy and toxicity of respiratory-gated PBT without fiducial markers for HCC located within 2 cm of the gastrointestinal tract. From March 2011 to December 2015 at our institution, 40 patients were evaluated (median age, 72 years; range, 38-87 years). All patients underwent PBT at a dose of 60 to 80 cobalt gray equivalents (CGE) in 20 to 38 fractions. The median follow-up period was 19.9 months (range, 1.2-72.3 months). The median tumor size was 36.5 mm (range, 11-124 mm). Kaplan-Meier estimates of the 2-year overall survival, progression-free survival, and local tumor control rates were 76%, 60%, and 94%, respectively. One patient (2.5%) developed a grade 3 gastric ulcer and one (2.5%) developed grade 3 ascites retention; none of the remaining patients developed grade >3 toxicities (National Cancer Institute Common Terminology Criteria for Adverse Events ver. 4.0.). This study indicates that PBT without fiducial markers achieves good local control without severe treatment-related toxicity of the gastrointestinal tract for HCC located within 2 cm of the gastrointestinal tract.

Strategic application of radiotherapy for hepatocellular carcinoma

With increasing clinical use, radiotherapy (RT) has been considered reliable and effective method for hepatocellular carcinoma (HCC) treatment, depending on extent of disease and patient characteristics. RT for HCC can improve therapeutic outcomes through excellent local control, downstaging, conversion from unresectable to resectable status, and treatments of unresectable HCCs with vessel invasion or multiple intrahepatic metastases. In addition, further development of modern RT technologies, including image-guided radiotherapy (IGRT), intensity-modulated radiotherapy (IMRT), and stereotactic body radiotherapy, has expanded the indication of RT. An essential feature of IGRT is that it allows image guidance therapy through in-room images obtained during radiation delivery. Compared with 3D-conformal RT, distinctions of IMRT are inverse treatment planning process and use of a large number of treatment fields or subfields, which provide high precision and exquisitely conformal dose distribution. These modern RT techniques allow more precise treatment by reducing inter- and intra-fractional errors resulting from daily changes and irradiated dose at surrounding normal tissues. More recently, particle therapy has been actively investigated to improve effectiveness of RT. This review discusses modern RT strategies for HCC, as well as optimal selection of RT in multimodal approach for HCC.

Clinical results of proton beam therapy for hepatocellular carcinoma over 5 cm

AIM

This study aimed to evaluate the safety and efficacy of proton beam therapy for large hepatocellular carcinoma (HCC).

METHODS

Twenty-four patients with a HCC larger than 5.0 cm were treated with proton beam therapy at our institution between 2008 and 2015.

RESULTS

The clinical stage was I in 2 patients, II in 9 patients, and IIIB in 13 patients. Ten of the 24 patients were not surgical candidates because of advanced HCC or old age. Median tumor size was 90 mm (range, 50-180 mm). Median total dose delivered was 72.6 Gray-equivalents (GyE) in 22 fractions (range, 60.8-85.8 GyE). Median follow-up period was 17.5 months (range, 3-70 months). Local control rate at 2 years was 87.0%. The 2-year overall survival rate was 52.4%. The predominant tumor progression pattern was new hepatic tumor development outside the irradiated field. No acute or late treatment-related toxicity of grade 3 or higher, other than dermatitis, was observed.

CONCLUSIONS

These results show that proton beam therapy offers an effective and safe method for treating patients with large HCC. Proton beam therapy represents a promising method for treatment of large-volume HCC.

Progressive hypofractionated carbon-ion radiotherapy for hepatocellular carcinoma: Combined analyses of 2 prospective trials

BACKGROUND

The objective of this study was to evaluate the safety and efficacy of carbon-ion radiotherapy (CIRT) in patients with hepatocellular carcinoma (HCC) with stepwise dose escalation and hypofractionation in 2 combined prospective trials.

METHODS

Sequential phase 1/2 (protocol 9603) and phase 2 (protocol 0004) trials were conducted for patients with histologically proven HCC. The phase 1 component of protocol 9603 was a dose-escalation study; CIRT was delivered in 12, 8, or 4 fractions. After determination of the recommended dose, 2 phase 2 trials were performed in an expanded cohort, and the data were pooled to analyze toxicity, local control, and overall survival.

RESULTS

In the phase 1 component of protocol 9603, 69.6, 58.0, and 52.8 Gy (relative biological effectiveness [RBE]) in 12, 8, and 4 fractions, respectively, constituted the maximum tolerated doses, and 52.8 Gy (RBE) in 4 fractions was established as the recommended dose regimen for the 2 phase 2 studies. In 124 patients with a total of 133 lesions, few severe adverse effects occurred, and local-control and overall survival rates at 1, 3, and 5 years were 94.7% and 90.3%, 91.4% and 50.0%, and 90.0% and 25.0%, respectively; this included 1-, 3-, and 5-year local-control rates of 97.8%, 95.5%, and 91.6%, respectively, in the phase 2 study. In a multivariate analysis, Child-Pugh class B and the presence of a tumor thrombus were significant factors for mortality.

CONCLUSIONS

The safety and efficacy of CIRT in 12, 8, and 4 fractions were confirmed, with 52.8 Gy (RBE) in 4 fractions established as the recommended treatment course for eligible HCC patients. Cancer 2017;123:3955-65. © 2017 The Authors. Cancer published by Wiley Periodicals, Inc. on behalf of American Cancer Society.

Particle radiotherapy, a novel external radiation therapy, versus liver resection for hepatocellular carcinoma accompanied with inferior vena cava tumor thrombus: A matched-pair analysis

BACKGROUND

Hepatocellular carcinoma accompanied with inferior vena cava tumor thrombus carries a dismal prognosis, and the feasibility of local treatment has remained controversial. The present study aimed to compare the outcomes of particle radiotherapy and liver resection in patients with hepatocellular carcinoma with inferior vena cava tumor thrombus.

METHODS

Thirty-one and 19 patients, respectively, underwent particle radiotherapy and liver resection for hepatocellular carcinoma with inferior vena cava tumor thrombus. A matched-pair analysis was undertaken to compare the short- and long-term outcomes according to tumor stage determined using the tumor-node-metastasis classification.

RESULTS

Both stages IIIB and IV (IVA and IVB) patients were well-matched for 12 factors, including treatment policy and patient and tumor characteristics. The median survival time of matched patients with stage IIIB tumors in the particle radiotherapy group was greater than that in the liver resection group (748 vs 272 days, P = .029), whereas no significant difference was observed in the median survival times of patients with stage IV tumors (239 vs 311 days, respectively). There were significantly fewer treatment-related complications of grade 3 or greater in the particle radiotherapy group (0%) than in the liver resection group (26%).

CONCLUSION

Particle radiotherapy is potentially preferable in hepatocellular carcinoma patients with stage IIIB inferior vena cava tumor thrombus and at least equal in efficiency to liver resection in those with stage IV disease, while causing significantly fewer complications. Considering the relatively high survival and low invasiveness of particle radiotherapy when compared to liver resection, this approach may represent a novel treatment modality for hepatocellular carcinoma with inferior vena cava tumor thrombus.

A systematic review of publications on charged particle therapy for hepatocellular carcinoma

Charged particle therapy (proton beam therapy and carbon ion therapy) is a form of radiotherapy which has the unique characteristic of superior depth dose distribution, and has been used for the treatment of hepatocellular carcinoma (HCC) in a limited number of patients, especially in Japan. We undertook a systematic review to define the clinical utility of charged particle therapy for patients with HCC. We searched the MEDLINE database from 1983 to June 2016 to identify clinical studies on charged particle therapy for HCC. Primary outcomes of interest were local control, overall survival, and late radiation morbidities. A total of 13 cohorts from 11 papers were selected from an initial dataset of 78 papers. They included a randomized controlled trial comparing proton beam therapy with transarterial chemoembolization, 9 phase I or II trials and 2 retrospective studies. The reported actuarial local control rates ranged from 71.4-95% at 3 years, and the overall survival rates ranged from 25-42.3% at 5 years. Late severe radiation morbidities were uncommon, and a total of 18 patients with grade ≥3 late adverse events were reported among the 787 patients included in this analysis. Charged particle therapy for HCC was associated with good local control with limited probability of severe morbidities. The cost-effectiveness and the distinctive clinical advantages of charged particle therapies should be clarified in order to become a socially accepted treatment modality for HCC.

Proton beam therapy for hepatocellular carcinoma

INTRODUCTION

Radiation therapy is an effective treatment option for hepatocellular carcinoma (HCC) patients. However, radiotherapy for HCC still has limited recognition as a standard treatment option in international consensus guidelines due to a paucity of randomized controlled trials and the risk of hepatotoxicity, which is primarily mediated by baseline liver function and dose delivered to non-tumor liver cells. Proton beam therapy (PBT) may offer advantages over photon-based radiation treatments through its dosimetric characteristic of sparing more liver volume at low to moderate doses. PBT has the potential to reduce radiation-related hepatotoxicity and allow for tumor dose escalation. Areas covered: This article reviews the clinical rationale for using PBT for HCC patients and clinical outcome and toxicity data from retrospective and prospective studies. PBT-specific technical challenges for these tumors and appropriate selection of patients to be treated with PBT are discussed. Expert commentary: Local control, overall survival, and toxicity results are promising for liver PBT. Future studies, including ongoing randomized cooperative group trials, will aim to determine the incremental benefit of PBT over photons and which patients are most suitable for PBT.