Stereotactic body radiation therapy using a respiratory-gated volumetric-modulated arc therapy technique for small hepatocellular carcinoma

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.

Role of Stereotactic Body Radiation Therapy in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC)is a common type of liver cancer with a poor prognosis, especially in patients with advanced stages or underlying liver disease. While surgical resection, liver transplantation, and ablation therapies have traditionally been the mainstay of treatment for HCC, radiation therapy has become increasingly recognized as an effective alternative, particularly for those who are not surgical candidates. Stereotactic Body Radiation Therapy (SBRT) is a highly precise form of radiation therapy that delivers very high doses of radiation to the tumor while sparing surrounding healthy tissue. Several studies have reported favorable outcomes with SBRT in HCC treatment. Moreover, SBRT can be used to treat recurrent HCC after prior treatment, offering a potentially curative approach in select cases. While SBRT has demonstrated its efficacy and safety in treating HCC, future studies are needed to further investigate the potential role of SBRT in combination with other treatments for HCC.

A simple method to measure the gating latencies in photon and proton based radiotherapy using a scintillating crystal

BACKGROUND

In respiratory gated radiotherapy, low latency between target motion into and out of the gating window and actual beam-on and beam-off is crucial for the treatment accuracy. However, there is presently a lack of guidelines and accurate methods for gating latency measurements.

PURPOSE

To develop a simple and reliable method for gating latency measurements that work across different radiotherapy platforms.

METHODS

Gating latencies were measured at a Varian ProBeam (protons, RPM gating system) and TrueBeam (photons, TrueBeam gating system) accelerator. A motion-stage performed 1 cm vertical sinusoidal motion of a marker block that was optically tracked by the gating system. An amplitude gating window was set to cover the posterior half of the motion (0-0.5 cm). Gated beams were delivered to a 5 mm cubic scintillating ZnSe:O crystal that emitted visible light when irradiated, thereby directly showing when the beam was on. During gated beam delivery, a video camera acquired images at 120 Hz of the moving marker block and light-emitting crystal. After treatment, the block position and crystal light intensity were determined in all video frames. Two methods were used to determine the gate-on (τ_on ) and gate-off (τ_off ) latencies. By method 1, the video was synchronized with gating log files by temporal alignment of the same block motion recorded in both the video and the log files. τ_on was defined as the time from the block entered the gating window (from gating log files) to the actual beam-on as detected by the crystal light. Similarly, τ_off was the time from the block exited the gating window to beam-off. By method 2, τ_on and τ_off were found from the videos alone using motion of different sine periods (1-10 s). In each video, a sinusoidal fit of the block motion provided the times T_min of the lowest block position. The mid-time, T_mid-light , of each beam-on period was determined as the time halfway between crystal light signal start and end. It can be shown that the directly measurable quantity T_mid-light - T_min  = (τ_off +τ_on )/2, which provided the sum (τ_off +τ_on ) of the two latencies. It can also be shown that the beam-on (i.e., crystal light) duration ΔT_light increases linearly with the sine period and depends on τ_off - τ_on : ΔT_light  = constant•period+(τ_off - τ_on ). Hence, a linear fit of ΔT_light as a function of the period provided the difference of the two latencies. From the sum (τ_off +τ_on ) and difference (τ_off - τ_on ), the individual latencies were determined.

RESULTS

Method 1 resulted in mean (±SD) latencies of τ_on  = 255 ± 33 ms, τ_off  = 82 ± 15 ms for the ProBeam and τ_on  = 84 ± 13 ms, τ_off  = 44 ± 11 ms for the TrueBeam. Method 2 resulted in latencies of τ_on  = 255 ± 23 ms, τ_off  = 95 ± 23 ms for the ProBeam and τ_on  = 83 ± 8 ms, τ_off  = 46 ± 8 ms for the TrueBeam. Hence, the mean latencies determined by the two methods agreed within 13 ms for the ProBeam and within 2 ms for the TrueBeam.

CONCLUSIONS

A novel, simple and low-cost method for gating latency measurements that work across different radiotherapy platforms was demonstrated. Only the TrueBeam fully fulfilled the AAPM TG-142 recommendation of maximum 100 ms latencies.

Study of hepatic toxicity in small liver tumors after photon or proton therapy based on factors predicting the benefits of proton

OBJECTIVES

In a previous study of hepatic toxicity, the following three factors were identified to predict the benefits of proton beam therapy (PBT) for hepatocellular carcinomas (HCCs) with a maximum diameter of ≤5 cm and Child-pugh grade A (CP-A): number of tumors (1 vs ≥2), the location of tumors (hepatic hilum or others), and the sum of the diameters of lesions. The aim of this study is to analyze the association between these three factors and hepatic toxicity.

METHODS

We retrospectively reviewed patients of CP-A treated with PBT or photon stereotactic body radiotherapy (X-ray radiotherapy, XRT) for HCC ≤5 cm. For normal liver dose, the V5, V10, V20 (volumes receiving 5, 10, and 20 Gy at least), and the mean dose was evaluated. The albumin-bilirubin (ALBI) and CP score changes from the baseline were evaluated at 3 and 6 months after treatment.

RESULTS

In 89 patients (XRT: 48, PBT: 41), those with two or three (2-3) predictive factors were higher normal liver doses than with zero or one (0-1) factor. In the PBT group, the ALBI score worsened more in patients with 2-3 factors than those with 0-1 factor, at 3 months (median: 0.26 vs 0.02, p = 0.032) and at 6 months (median: 0.35 vs 0.10, p = 0.009). The ALBI score change in the XRT group and CP score change in either modality were not significantly different in the number of predictive factors.

CONCLUSION

The predictive factor numbers predicted the ALBI score change in PBT but not in XRT.

ADVANCES IN KNOWLEDGE

This study suggest that the number of predictive factors previously identified (0-1 vs 2-3) were significantly associated with dosimetric parameters of the normal liver in both modalities. In the proton group, the number of predictive factors was associated with a worsening ALBI score at 3 and 6 months, but these associations were not found in the photon SBRT group.

Prognosis and Risk Factors of Recurrence in HBV-Related Small Hepatocellular Carcinoma After Stereotactic Body Radiation Therapy

Objective

The role of stereotactic body radiation therapy (SBRT) for treating small hepatocellular carcinoma (sHCC) has gained increasing recognition. However, the prognosis and risk factors for recurrence in patients with sHCC remain unclear. This study investigated the risk factors for the recurrence of hepatitis B virus (HBV)-related sHCC after SBRT.

Methods

A total of 240 HBV-related sHCC patients treated with SBRT between March 2011 and March 2020 were retrospectively analyzed. The cumulative probability of recurrence was calculated according to the Kaplan–Meier method. Univariate and multivariate analyses were performed with Cox proportional hazard models.

Results

Recurrent hepatocellular carcinoma developed in 134 (55.8%) patients at a median time of 27 months after SBRT. The one- and two-year rates of recurrence were 20.9 and 45.0%, respectively. The median follow-up time was 30 months. The Cox multivariate analysis indicated that age (P = 0.029, HR [1.019, 1.002–1.037]), tumor size (P = 0.012, HR [1.227, 1.045–1.440]), and aspartate aminotransferase-to-platelet ratio index (APRI) (P = 0.005, HR [1.911, 1.221–2.989]) were independent risk factors for recurrence.

Conclusion

Patients receiving SBRT for HBV-related sHCC may be at greater risk of recurrence if they have a high APRI score combined with advanced age and large tumor size.

A study on predicting cases that would benefit from proton beam therapy in primary liver tumors of less than or equal to 5 cm based on the estimated incidence of hepatic toxicity

•

An advantage of PBT is reducing the liver receiving low doses of radiation.

•

The factors predicting the benefit in PBT are different among NTCP models.

•

The tumor size, number, and location are useful in estimating the benefits of PBT.

Background

Materials and methods

Results

Conclusions

Stereotactic body radiation therapy as a salvage treatment for single viable hepatocellular carcinoma at the site of incomplete transarterial chemoembolization: a retrospective analysis of 302 patients

BACKGROUND

To evaluate the clinical outcomes of patients who received stereotactic body radiation therapy (SBRT) for single viable hepatocellular carcinoma (HCC) at the site of incomplete transarterial chemoembolization (TACE).

METHODS

Patients treated with SBRT for single viable HCC after incomplete TACE between 2012 and 2017 at Asan Medical Center (Seoul, South Korea) were included. Incomplete TACE was defined as (1) evidence of viable HCC at the site of TACE on follow-up dynamic computed tomography (CT) or magnetic resonance imaging following one or more consecutive TACEs, (2) no definite tumor staining on superselective hepatic angiogram, or (3) no definite iodized oil uptake on post-embolization angiogram or CT. Doses of 10-15 Gy per fraction were given over 3-4 consecutive days. The primary outcome was local control rate at 3 years and secondary outcome included tumor response, overall survival rate, out-of-field intrahepatic recurrence-free survival, distant metastasis-free survival and treatment-related toxicities. Treatment-related adverse events were evaluated according to the common terminology criteria for adverse events, version 4.03.

RESULTS

A total of 302 patients were analyzed. The median follow-up duration was 32.9 months (interquartile range [IQR], 23.6-41.7) and the median tumor size was 2.0 cm (range, 0.7-6.9). The local control (LC) and overall survival rates at 3 years were 91.2 and 72.7%, respectively. 95.4% of the tumors reached complete response (CR) during the entire follow-up period (anyCR). The median interval from SBRT to anyCR was 3.4 months (IQR, 1.9-4.7), and 39.9 and 83.3% of the lesions reached CR at 3- and 6-months after SBRT, respectively. Radiation-induced liver disease was observed in 8 (2.6%) patients. No patients experienced gastroduodenal bleeding within the radiation field.

CONCLUSION

SBRT could be considered a feasible salvage treatment option for HCC after incomplete TACE.

Effectiveness of individual audio-visual coaching, respiratory modulated stereotactic body radiotherapy for localized hepatocellular carcinoma: Analysis of 29 cases from a single academic radiotherapy center

Objectives:

Recently, Stereotactic Body Radiotherapy (SBRT) has been suggested for managing hepatocellular carcinoma (HCC) curatively. Thus, we conducted this clinical study to evaluate retrospectively the effect of individualized audio-visual (AV) coaching, respiratory modulated SBRT.

Materials and Methods:

Between 2014 and 2018, 29 patients with inoperable Barcelona Clinic Liver Cancer (BCLC) stage 0-B HCC received AV coaching, respiratory-modulated SBRT. We constructed a task-oriented multidisciplinary team to establish a standard operation process of respiratory modulation procedures and developed our AV coaching devices. In the training period, a goodness-of-fit test was applied individually. SBRT was delivered with a total dose of 40–54 Gy in 5–6 fractions individually. Freedom from local progression (FFLP) and overall survival (OS) were estimated using SPSS (version 17, SPSS Inc., Chicago, IL, USA) life tables.

Results:

The patient characteristics were as follows: 32.7 ± 16 mm in maximum tumor diameter (range 11–94); BCLC stage 0: 3.4%, BCLC A: 48.3%, BCLC B: 48.3%; Child-Pugh classification A: 86.2%, Child-Pugh classification B: 13.8%, and a median of 2 prior liver-directed treatments (range 0–7). One-, 2-, and 3-year rates of FFLP of SBRT were 96.6%, 96.6%, and 96.6%, respectively. One-, 2-, and 3-year rates of OS were 81.5%, 72.4%, and 67.2%, respectively. No adverse event (AE) occurred in 41.4% of patients, 48.3% developed grade (G) 1–2 AE, 10.3% had G3 AE and none had G4-5 AE.

Conclusion:

Respiration-modulated SBRT is a promising noninvasive treatment option for patients with inoperable and localized HCC. Our data show that SBRT provides comparable tumor control to historical curative options like surgery and radiofrequency ablation of localized tumors. Thus, we are conducting a further prospective clinical trial with the intent to demarcate the clinical effectiveness of SBRT in a larger population of patients with HCC.

Stereotactic ablative radiotherapy for hepatocellular carcinoma: A systematic review and meta-analysis of local control, survival and toxicity outcomes

There is a growing body of literature supporting the use of stereotactic ablative body radiotherapy (SABR) in the management of primary hepatocellular carcinoma (HCC). This systematic review and meta-analysis of the current published evidence for SABR for HCC assessed the impact of treatment dose, fractionation and tumour size on the outcomes of local control (LC), overall survival (OS) and toxicity. A systematic search was independently performed by two authors for articles published in peer-reviewed journals between January 2005 and December 2019. A DerSimonian and Laird random effects model was used to assess pooled results. A multivariate meta-regression analysis incorporated the effect of explanatory variables (radiation dose in EQD2_[10], fractionation and tumour size) on outcomes of OS, LC and toxicity. Forty-nine cohorts involving 2846 HCC patients with 3088 lesions treated with SABR were included. Pooled 1-, 2- and 3-year LC rates were 91.1% (95% confidence interval [CI] 88.3-93.2), 86.7% (95% CI 82.7-89.8) and 84.2% (95% CI 77.9-88.9) respectively. Pooled 1-, 2- and 3-year OS rates were 78.4% (95% CI 73.4-82.6), 61.3% (55.2-66.9) and 48.3% (95% CI 39.0-57). Population-weighted median grade 3 toxicity rates were 6.5% (IQR 3.2-16) and mean grade 4/5 rates were 1.4% (IQR 0-2.1). Within EQD2_[10] ranges of 40 to 83.33 Gy corresponding to common dose-fractionation regimens of 30-50 Gy in 5 fractions, there was a multivariate association between superior LC and OS with increasing EQD2_[10] , with a proportionately smaller increase in grade 3 toxicity and no association with grade 4/5 toxicity. Stereotactic ablative body radiotherapy is a viable treatment option for HCC with high LC rates and low rates of reported grade 3/4 toxicity. Increasing EQD2_[10] was associated with improvements in LC and OS with a comparatively smaller increase in toxicity. Prospective randomised trials are warranted to define optimal patient selection and dose-fractionation regimens.

Treatment outcomes of stereotactic body radiation therapy using a real-time tumor-tracking radiotherapy system for hepatocellular carcinomas

AIM

To report the outcomes of stereotactic body radiotherapy using a real-time tumor-tracking radiotherapy system for hepatocellular carcinoma patients.

METHODS

From January 2005 to July 2018, 63 patients with 74 lesions with a maximum diameter ≤52 mm were treated by stereotactic body radiotherapy using a real-time tumor-tracking radiotherapy system. No patient with a Child-Pugh Score ≥9 was included, and 85.6% had a score of 5 or 6. Using the biological effective dose (BED) with an α/β ratio of 10 (BED₁₀ ), the median dose in BED₁₀ at the reference point was 76.8 Gy (range 60-122.5 Gy). Overall survival (OS) and local control rates were assessed using the Kaplan-Meier method.

RESULTS

With a median follow-up period of 24.6 months (range 0.9-118.4 months), the 1-year and 2-year OS rates were 86.8% (95% confidence interval [95% CI] 75.8-93.3) and 71.1% (57.8-81.6), respectively. The 2-year OS was 89.6% in patients with the baseline modified albumin-bilirubin (mALBI) grade =1, and 61.7% in patients with grade ≥2a. In the multivariate analysis, the mALBI grade (=1 vs. ≥2a) was a significant factor for OS (p = 0.028, 95% CI 1.11-6.18). The 1-year and 2-year local control rates were 100% (100-100%) and 92.0% (77.5-97.5%). The local control rates were significantly higher in the BED₁₀ ≥100 Gy group than in the BED₁₀ <100 Gy group (2-year 100% vs. 86.5%, p = 0.049) at the reference point.

CONCLUSION

This retrospective study of stereotactic body radiotherapy using real-time tumor-tracking radiotherapy for hepatocellular carcinoma showed favorable outcomes with lower incidence of toxicities, especially in patients treated with BED₁₀ ≥100 Gy to the reference point.

Radiofrequency ablation versus stereotactic body radiation therapy for small (≤ 3 cm) hepatocellular carcinoma: A retrospective comparison analysis

BACKGROUND AND AIM

We compared the clinical outcomes of radiofrequency ablation (RFA) and stereotactic body radiation therapy (SBRT) in small (≤ 3 cm) hepatocellular carcinoma.

METHODS

A total of 266 patients treated with RFA (n = 179) or SBRT (n = 87) were reviewed. Local control rates (LCRs), intrahepatic recurrence-free survival (IHRFS) rates, and overall survival (OS) rates were compared. Inverse probability of treatment weighting (IPTW) was used to adjust for imbalances in baseline characteristics between the two groups.

RESULTS

The median follow-up period was 50.3 months, and treatment method (RFA vs SBRT) was not a significant prognostic factor for LCR, OS, and IHRFS in both multivariate and IPTW-adjusted analyses. The 4-year LCRs after RFA and SBRT were 92.7% and 95.0%, respectively. Perivascular location was a significant prognostic factor for LCR in the entire patients and in the RFA group, but not in the SBRT group. The 4-year OS rates in the RFA and SBRT groups were 78.1% and 64.1%, respectively (P = 0.012). After IPTW adjustment, the 4-year LCRs (90.6% vs 96.3%) and OS rates (71.8% vs 70.2%) were not significantly different between the two groups. The rate of grade ≥ 3 adverse events was 0.6% (n = 1) in the RFA group and 1.1% (n = 1) in the SBRT group.

CONCLUSIONS

The two treatment methods showed comparable outcomes in terms of LCR, OS rate, and IHRFS rate after IPTW adjustment. SBRT seems to be a viable alternative method for small hepatocellular carcinomas that are not suitable for RFA due to tumor location.

Current Understanding of Ablative Radiation Therapy in Hepatocellular Carcinoma

The role of ablative stereotactic body radiotherapy (SBRT) in hepatocellular carcinoma (HCC) has been evolving over the last few decades. SBRT has mostly been used in early stages of HCC, including few (≤ 3 in number) tumors, small tumours (< 3 cm in size), as well as larger tumours which are ineligible for other ablative modalities, mostly without vascular invasion. In early stage HCC, SBRT is used as a definitive treatment with curative intent or with intent to bridge to liver transplant. Retrospective and prospective institutional series document a high rate of local control (68–95% at 3 years) following SBRT. This coupled with a low risk of toxicity makes this non-invasive ablative treatment an attractive option for patients who are ineligible for other ablative treatments. Small randomized studies of ablative radiation have also shown non-inferiority of radiation as compared to radiofrequency ablation (RFA). Currently, SBRT is widely available as a safe and effective liver directed therapy, although there is a need for more studies providing higher level evidence. This review gives a brief overview of SBRT and the evidence for its use in HCC patients with ablative intent.

Therapeutic outcome and related predictors of stereotactic body radiotherapy for small liver-confined HCC: a systematic review and meta-analysis of observational studies

Background and purpose

Stereotactic body radiotherapy (SBRT) is a promising ablative modality for hepatocellular carcinoma (HCC) especially for those with small-sized or early-stage tumors. This study aimed to synthesize available data to evaluate efficacy and explore related predictors of SBRT for small liver-confined HCC (≤ 3 lesions with longest diameter ≤ 6 cm).

Materials and methods

A systematic search were performed of the PubMed and Cochrane Library databases. Primary endpoints were overall survival (OS) and local control (LC) of small HCC treated with SBRT, meanwhile, to evaluate clinical parameters associated with treatment outcome by two methods including subgroup comparisons and pooled HR meta-analysis. The secondary endpoint was treatment toxicity.

Results

After a comprehensive database review, 14 observational studies with 1238 HCC patients received SBRT were included. Pooled 1-year and 3-year OS rates were 93.0% (95% confidence interval [CI] 88.0–96.0%) and 72.0% (95% CI 62.0–79.0%), respectively. Pooled 1-year and 3-year LC rates were 96.0% (95% CI 91.0–98.0%) and 91.0% (95% CI 85.0–95.0%), respectively. Subgroup comparisons regarding Child–Pugh class (stratified by CP-A percentage 100%, 75–100%, 50–75%) showed there were statistically significant differences for both 1-year and 3-year OS rate (p < 0.01), while that regarding number of lesions, pretreatment situation, age (median/mean age of 65), macrovascular invasion, tumor size, and radiation dose (median BED₁₀ of 100 Gy), there were no differences. In subgroup comparisons for LC rate, it showed number of lesions (1 lesion vs. 2–3 lesions) was significantly associated with 1-year LC rate (p = 0.04), though not associated with 3-year LC rate (p = 0.72). In subgroup comparisons categorized by other factors including pretreatment situation, age, CP-A percentage, macrovascular invasion, tumor size, and radiation dose, there were no significant differences for 1- or 3-year LC rate. To further explore the association between CP class and OS, the second method was applied by combining HR and 95% CIs. Results indicated CP-A was predictive of better OS (p = 0.001) with pooled HR 0.31 (95% CIs 0.11–0.88), which was consistent with subgroup comparison results. Concerning adverse effect of SBRT, pooled rates of grade ≥ 3 hepatic complications and RILD were 4.0% (95% CI 2.0–8.0%) and 14.7% (95% CI 7.4–24.7%), respectively.

Conclusion

The study showed that SBRT was a potent local treatment for small liver-confined HCC conferring excellent OS and LC persisting up to 3 years, even though parts of included patients were pretreated or with macrovascular invasion. CP-A class was a significant predictor of optimal OS, while number of lesions might affect short term tumor control (1-year LC). Tumor size and radiation dose were not vital factors impacting treatment outcome for such small-sized HCC patients. Because of the low quality of observational studies and heterogeneous groups of patients treated with SBRT, further clinical trials should be prospectively investigated in large sample sizes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13014-021-01761-1.

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.

A preliminary investigation of re-evaluating the irradiation dose in hepatocellular carcinoma radiotherapy applying 4D CT and deformable registration

Purpose

To investigate the effect of breathing motion on dose distribution for hepatocellular carcinoma (HCC) patients using four‐dimensional (4D) CT and deformable registration.

Methods

Fifty HCC patients who were going to receive radiotherapy were enrolled in this study. All patients had been treated with transarterial chemoembolization beforehand. Three‐dimensional (3D) and 4D CT scans in free breathing were acquired sequentially. Volumetric modulated arc therapy (VMAT) was planned on the 3D CT images and maximum intensity projection (MIP) images. Thus, the 3D dose (Dose‐_3D) and MIP dose (Dose‐_MIP) were obtained, respectively. Then, the Dose‐_3D and Dose‐_MIP were recalculated on 10 phases of 4D CT images, respectively, in which the end‐inhale and end‐exhale phase doses were defined as Dose‐_3D‐EI, Dose‐_3D‐EE, Dose‐_MIP‐EI, and Dose‐_MIP‐EE. The 4D dose (Dose‐_4D‐3D and Dose‐_4D‐MIP) were obtained by deforming 10 phase doses to the end‐exhale CT to accumulate. The dosimetric difference in Dose‐_3D, Dose‐_EI3D, Dose‐_EE3D, Dose‐_4D‐3D, Dose‐_MIP, Dose‐_EIMIP, Dose‐_EEMIP, and Dose‐_4D‐MIP were compared to evaluate the motion effect on dose delivery to the planning target volume (PTV) and normal liver.

Results

Compared with Dose‐_3D, PTV D99 in Dose‐_EI3D, Dose‐_EE3D and Dose‐_4D‐3D decreased by an average of 6.02%, 1.32%, 2.43%, respectively (P < 0.05); while PTV D95 decreased by an average of 3.34%, 1.51%, 1.93%, respectively (P < 0.05). However, CI and HI of the PTV in Dose‐_3D was superior to the other three distributions (P < 0.05). There was no significant differences for the PTV between Dose‐_EI and Dose‐_EE, and between the two extreme phase doses and Dose‐_4D (P> 0.05). Negligible difference was observed for normal liver in all dose distributions (P> 0.05).

Conclusions

Four‐dimensional dose calculations potentially ensure target volume coverage when breathing motion may affect the dose distribution. Dose escalation can be considered to improve the local control of HCC on the basis of accurately predicting the probability of radiation‐induced liver disease.

Clinical outcomes of stereotactic body radiation therapy for small hepatocellular carcinoma

BACKGROUND AND AIM

The purpose of this study was to investigate the long-term oncologic outcomes after stereotactic body radiation therapy (SBRT) for small hepatocellular carcinoma (HCC).

METHODS

A total of 290 patients with HCC were registered between March 2007 and July 2013. A dose of 10-15 Gy per fraction was given over three to four consecutive days, resulting in a total dose of 30-60 Gy. Overall and recurrence-free survivals were estimated from the date of the start of SBRT to the date of death, the last follow-up examination, or to the date of tumor recurrence.

RESULTS

The median follow-up period of all patients was 38.2 months, and the median tumor size was 1.7 cm. Overall survival (OS) rate at 5 years was 44.9%. Multivariate analyses revealed that age, Child-Pugh class, tumor size, and albumin levels were significant factors for OS. The 5-year local control rate was 91.3%. In multivariate analysis, tumor size and albumin were significantly associated with local tumor control. However, there was a negative correlation between total dose and tumor size in Pearson's correlation analysis (r = -0.111, P = 0.046).

CONCLUSIONS

Stereotactic body radiation therapy was an excellent ablative treatment option for patients with small HCC. Tumor size was a significant factor for local tumor control after SBRT, although the total dose was negatively correlated with tumor size. Considering the low OS rates and the high local tumor control rates, the combined SBRT and systemic therapies may be beneficial for improving survival outcomes.

Stereotactic body radiation therapy for small (≤5 cm) hepatocellular carcinoma not amenable to curative treatment: Results of a single-arm, phase II clinical trial

Background/Aims

Stereotactic body radiation therapy (SBRT) is used as an alternative ablative treatment in patients with hepatocellular carcinoma (HCC) not suitable for curative treatments. The purpose of this prospective study was to evaluate the long-term efficacy of SBRT for small (≤5 cm) HCCs.

Methods

A phase II, single-arm clinical trial on SBRT for small HCCs was conducted at an academic tertiary care center. The planned SBRT dose was 45 Gy with a fraction size of 15-Gy over 3 consecutive days. The primary endpoint was 2-year local control rate. Radiologic responses were assessed according to the Response Evaluation Criteria in Solid Tumors (RECIST, version 1.1) and the modified RECIST criteria.

Results

Between 2013 and 2016, 50 patients (53 lesions) were enrolled, with a median follow-up period of 47.8 months (range, 2.9–70.6). Patients’ age ranged from 41 to 74 years, and 80% were male. Median tumor size was 1.3 cm (range, 0.7–3.1). The 2- and 5-year local control rates were 100% and 97.1%, respectively. The 5-year overall survival rate was 77.6%. Six months after SBRT, radiologic responses were evident in 44 lesions (83%) according to the RECIST criteria and 49 (92.4%) according to the modified RECIST criteria. None of the patients showed grade ≥3 adverse events.

Conclusions

SBRT showed excellent results as an ablative treatment for patients with small HCCs while showing minimal toxicities. SBRT can be a good alternative for both curative and salvage intents in patients with HCCs that are unsuitable for curative treatments.

Preoperative Stereotactic Body Radiotherapy to Portal Vein Tumour Thrombus in Hepatocellular Carcinoma: Clinical and Pathological Analysis

The prognosis of hepatocellular carcinoma (HCC) with portal vein tumour thrombus (PVTT) is poor. We conducted a prospective study to evaluate the efficacy and safety of tri-modality therapy, including preoperative stereotactic body radiotherapy (SBRT) and surgery, followed by hepatic arterial infusion chemotherapy (HAIC) in HCC patients with PVTT. In this report, we investigated the pathology of the irradiated PVTT specimen in resected cases and SBRT-related acute toxicity. A total of 8 HCC patients with PVTT received preoperative SBRT targeting the PVTT at a dose of 48 Gy in 4 fractions at our institute from 2012 to 2016. Of the eight patients, six underwent surgery, while the remaining two did not because of disease progression. At the pathological examination, all patients’ irradiated PVTT specimens showed necrotic tissue, and three of six patients showed complete pathological response. Two patients showed 30% necrosis with high degeneration and one patient, with 30% necrosis without degeneration, was the only recurrent case found during the follow-up period (median: 22.5, range: 5.9–49.6 months). No SBRT-related acute toxicity worse than grade 2 was observed from SBRT to surgery. In conclusion, the preoperative SBRT for HCC was pathologically effective and the acute toxicities were tolerable.

Image quality evaluation of in-treatment four-dimensional cone-beam computed tomography in volumetric-modulated arc therapy for stereotactic body radiation therapy

In this study, the image quality of in-treatment four-dimensional cone-beam computed tomography (In-4D-CBCT) obtained with various prescription doses (PDs) were quantitatively evaluated in volumetric-modulated arc therapy (VMAT) for stereotactic body radiation therapy (SBRT) of the lungs and liver. To assess image quality, we used a dynamic thorax phantom and three-dimensional (3D) abdominal phantom; In-4D-CBCT images were acquired with various PDs (from 5 to 12 Gy). The In-4D-CBCT with various PDs were compared with the reference images (pre-4D-CBCT). The image quality was evaluated using the signal-to-noise ratio (SNR), the contrast-to-noise ratio (CNR), and the Dice similarity coefficient (DSC). The fiducial marker positions with various PDs were compared with those of the reference images. For the dynamic thorax phantom, the difference between pre- and In-4D-CBCT in terms of SNR and CNR decreased, as the PD increased from 6 to 12 Gy. The median DSC ranged from 0.7 to 0.74, and showed good similarity. For the 3D abdominal phantom, the difference between pre- and In-4D-CBCT in terms of SNR and CNR decreased as the PD increased from 5 to 6 Gy; conversely, it increased as the PD increased from 7 to 8 Gy. The fiducial marker positions were within 1.0 mm for all PDs. We concluded that the image quality of In-4D-CBCT degraded compared with the reference image; however, it was sufficiently accurate for assessing the intra-fractional tumor position in VMAT for SBRT of the lungs and liver both in terms of the target volume similarity and accuracy of the fiducial marker position.

Current status of stereotactic body radiotherapy for the treatment of hepatocellular carcinoma

Stereotactic body radiotherapy (SBRT) is an advanced form of radiotherapy (RT) with a growing interest on its application in the treatment of hepatocellular carcinoma (HCC). It can deliver ablative radiation doses to tumors in a few fractions without excessive doses to normal tissues, with the help of advanced modern RT and imaging technologies. Currently, SBRT is recommended as an alternative to curative treatments, such as surgery and radiofrequency ablation. This review discusses the current status of SBRT to aid in the decision making on how it is incorporated into the HCC management.

[Liver stereotactic body radiotherapy: Clinical features and technical consequences, results. Which treatment machine in which situation?]

Liver stereotactic body radiotherapy is a developing technique for the treatment of primary tumours and metastases. Its implementation is complex because of the particularities of the treated organ and the comorbidities of the patients. However, this technique is a treatment opportunity for patients otherwise in therapeutic impasse. The scientific evidence of liver stereotactic body radiotherapy has been considered by the French health authority as insufficient for its widespread use outside specialized and experienced centers, despite a growing and important number of retrospective and prospective studies, but few comparative data. This article focuses on the specific features of stereotactic body radiotherapy for liver treatments and the results of published studies of liver stereotactic body radiotherapy performed with classic linear accelerators and dedicated radiosurgery units.

Comparison of Stereotactic Body Radiation Therapy and Transarterial Chemoembolization for Unresectable Medium-Sized Hepatocellular Carcinoma

PURPOSE

This study compared the local control and overall survival (OS) between stereotactic body radiation therapy (SBRT) and transarterial chemoembolization (TACE) in medium-sized (3-8 cm) hepatocellular carcinoma (HCC).

METHODS AND MATERIALS

From January 2008 to October 2017, 188 patients with medium-sized HCC underwent either TACE (n = 142) or SBRT (n = 46). We adjusted for imbalances in treatment assignment using propensity score matching. Infield control (IFC) and OS were analyzed retrospectively.

RESULTS

The median follow-up time was 17.1 months for all patients and 26.6 months for surviving patients. The 3-year IFC was 63.0% for the TACE group and 73.3% for the SBRT group. Multivariable analysis identified the independent predictors for IFC as treatment modality (SBRT vs TACE), sex (female vs male), and recurrence status (recurrence vs new diagnosis). The 3-year OS was 22.9% for the TACE group and 47.4% for the SBRT group. Multivariable analysis identified the independent predictors of OS as number of tumors, treatment modality (SBRT vs TACE), albumin-bilirubin grade, tumor volume, Eastern Cooperative Oncology Group status, and recurrence status. Propensity score matching analysis revealed that the SBRT group had better IFC (3-year IFC of 77.5% vs 55.6%; P = .007) and OS (3-year OS of 55.0% vs 13.0%; P < .001) than the TACE group. For recurrent HCC, the SBRT group exhibited superior IFC (3-year IFC of 75% vs 57.5%; P = .022) and OS (3-year OS of 58.3% vs 5.9%; P < .001) compared with the TACE group. However, there was no difference in IFC or OS between TACE and SBRT for patients with newly diagnosed HCC.

CONCLUSIONS

SBRT has better IFC and OS rates than TACE in patients with medium-sized HCC, particularly for recurrent cases, which warrants prospective randomized controlled trials of TACE and SBRT.

Stereotactic body radiation therapy in patients with hepatocellular carcinoma: A mini-review

Stereotactic body radiation therapy (SBRT) is an emerging treatment for hepatocellular carcinoma. This technique results in excellent local control rates with favorable toxicity profile despite being predominantly used in heavily pretreated patients or those unsuitable for other local therapies. SBRT may be used as a sole treatment or in combination with other local therapies as well as a bridging strategy for patient awaiting liver transplants. This brief review describes current practice of SBRT with respect to radiation technique, patient selection and treatment concepts. It summarizes available evidence from retro- and prospective studies evaluating SBRT alone, SBRT in combination with other treatments and SBRT compared to other local treatment approaches.

Stereotactic body radiation therapy for hepatocellular carcinoma: Practice patterns, dose selection and factors impacting survival

Background

Stereotactic body radiation therapy (SBRT) is an emerging option for unresectable hepatocellular carcinoma (HCC) without consensus regarding optimal dose schemas. This analysis identifies practice patterns and factors that influence dose selection and overall survival, with particular emphasis on dose and tumor size.

Materials/Methods

Query of the National Cancer Database (NCDB) identified patients with unresectable, nonmetastatic HCC who received SBRT from 2004 to 2013. Biological Effective Dose (BED) was calculated for each patient in order to uniformly analyze different fractionation regimens.

Results

A total of 456 patients met the inclusion criteria. The median BED was 100 Gy (22.5‐208.0), which corresponded to the most common dose fractionation (50 Gy in five fractions). Various factors influenced dose selection including tumor size (P < 0.001), tumor stage (P = 0.002), and facility case volume (<0.001). On multivariate analysis, low BED (<75 Gy, HR 2.537, P < 0.001; 75‐100 Gy, HR 1.986, P = 0.007), increasing tumor size (HR 1.067, P = 0.032), elevated AFP (HR 1.585, P = 0.019), stage 3 (HR 1.962, P < 0.001), low‐volume facilities (1‐5 cases HR 1.687, P = 0.006), and a longer time interval from diagnosis to SBRT (>2 to ≤4 months, HR 1.456, P = 0.048; >4 months, HR 2.192, P < 0.001) were associated with worse survival.

Conclusion

SBRT use is increasing for HCC, and multiple regimens are clinically employed. Although high BED was associated with improved outcomes, multiple factors contributed to the dose selection with favorable patients receiving higher doses. Continued efforts to enhance radiation planning and delivery may help improve utilization, safety, and efficacy.

Early Diffusion-Weighted Imaging and Proton Magnetic Resonance Spectroscopy Features of Liver Transplanted Tumors Treated with Radiation in Rabbits: Correlation with Histopathology

In this study, we sought to determine how diffusion-weighted imaging (DWI) and proton magnetic resonance spectroscopy (¹H-MRS) features are associated with histopathological results, and explored the cellular mechanisms of DWI and ¹H-MRS in early radiosensitivity of transplanted liver tumors. VX2 tumors were implanted into the hind leg muscles of 60 New Zealand White Rabbits. All rabbits were randomly divided into ten subgroups according to treatment: irradiated or nonirradiated and according to different times postirradiation. Magnetic resonance scanning was then performed one day before irradiation and on days 1, 3, 5 and 7 postirradiation. Differences in tumor volume, apparent diffusion coefficient (ADC) value, choline/creatine ratio and lipid/creatine ratio, and their associations with histopathological findings, were assessed. Tumor volumes in the irradiated groups were smaller than control values, while ADC values increased gradually with time postirradiation; choline/creatine ratios were reduced while lipid/creatine ratios were larger compared to control values. Bax protein levels after irradiation increased with time. Interestingly, the ADC value and Bax-positive grade showed the same increasing trend (r = 0.900, P < 0.001). Additionally, choline/creatine and lipid/creatine ratios were respectively significantly associated with Bax-positive grade. Furthermore, significant associations of tumor volume with ADC value, choline/creatine ratio and lipid/creatine ratio were observed. These findings demonstrated that ADC value, choline/creatine ratio and lipid/creatine ratio, indicators of early radiosensitivity, are related to cell apoptosis.

Evaluation of delivered dose to a moving target by 4D dose reconstruction in gated volumetric modulated arc therapy

Purpose

To develop a 4D dose reconstruction method and to evaluate the delivered dose in respiratory-gated volumetric modulated arc therapy (VMAT).

Materials and methods

A total 112 treatment sessions of gated VMAT for 30 stereotactic body radiotherapy (SBRT) patients (10 lung, 10 liver, and 10 pancreas) were evaluated. For respiratory-gated SBRT, 4DCT was acquired, and the CT data at the end-exhale phase was used for a VMAT plan. The delivered dose was reconstructed using a patient’s respiratory motion and machine motion acquired during the beam delivery. The machine motion was obtained from the treatment log file, while the target position was estimated from an external respiratory marker position. The target position was divided into 1-mm position bins, and sub-beams with beam isocenters corresponding to each position bin were created in a motion mimicking plan, reflecting motion data including MLC leaf positions and gantry angle and target position data during beam treatment. The reconstructed 4D dose was compared with the dose of the original plan using these dosimetric parameters; the maximum dose (D_max) and mean dose (D_mean) of gross target volume (GTV) or organs at risk (spinal cord, esophagus, heart, duodenum, kidney, spinal cord, and stomach). The minimum dose (D_min) to GTV was also calculated to verify cold spots in tumors.

Results

There was no significant difference of dose parameters regard to the GTV in all tumors. For the liver cases, there were significant differences in the D_max of duodenum (-4.2 ± 1.4%), stomach (-3.5 ± 4.2%), left kidney (-4.1 ± 2.8%), and right kidney (-3.2 ± 1.3%), and in the D_mean of duodenum (-3.8 ± 1.4%), stomach (-3.9 ± 2.2%), left kidney (-3.1 ± 2.8%), and right kidney (-4.1 ± 2.6%). For the pancreas cases, there were significant differences in the D_max of stomach (2.1 ± 3.0%), and in the D_mean of liver (1.5 ± 0.6%), duodenum (-1.0 ± 1.4%), stomach (2.1 ± 1.6%), and right kidney (-1.3 ± 0.9%). The average gamma pass rates were 97.6 ± 4.8% for lung cases, 99.6 ± 0.5% for liver cases, and 99.5 ± 0.5% for pancreas cases. Most cases showed insignificant dose variation, with gamma pass rates higher than 98%, except for two lung cases with gamma pass rates of 86.9% and 90.6%. The low gamma pass rates showed larger global motion ranges resulting from the baseline shift during beam delivery.

Conclusion

The actual delivered dose in thoracic and abdominal VMAT under breathing motion was verified by 4D dose reconstruction using typical treatment equipment and software. The proposed method provides a verification method for the actual delivered dose and could be a dosimetric verification QA tool for radiation treatment under various respiratory management techniques.

Long-term complete response after transcatheter arterial chemoembolization and stereotactic body radiation therapy in a patient with hepatocellular carcinoma at the caudate lobe

It is expected that a combination of transcatheter arterial chemoembolization (TACE) with stereotactic body radiation therapy (SBRT) may induce synergistic therapeutic effects in hepatocellular carcinoma (HCC), which would result in a high rate of complete therapeutic response. In this study, we present the 5-year clinical course of a patient who had HCC at the caudate lobe, which was treated with TACE and SBRT. A 53-year-old male was diagnosed with an 8 cm-sized HCC at the caudate lobe with compression of the inferior vena cava (IVC). For fear of pulmonary metastasis, we decided to perform sequential TACE-radiotherapy instead of upfront hepatectomy, although the tumor appeared resectable. The first session of TACE, SBRT with 12 fractions, and the second session of TACE were sequentially performed. The patient was administered metformin for chemoprevention. Over the course of a 5-year follow-up, there was no evidence of HCC recurrence. We reported the clinical sequence of a patient showing complete therapeutic response of HCC at the caudate lobe after a combination of TACE and radiotherapy. This type of combined locoregional treatment can be a therapeutic option for HCC at the caudate lobe with marginal resectability.