Escalated focal liver radiation and concurrent hepatic artery fluorodeoxyuridine for unresectable intrahepatic malignancies

CT evaluations of focal liver reactions following stereotactic body radiotherapy for small hepatocellular carcinoma with cirrhosis: relationship between imaging appearance and baseline liver function

This study aimed to assess the imaging appearances of focal liver reactions following stereotactic body radiotherapy (SBRT) for small hepatocellular carcinoma (HCC) and to examine relationships between imaging appearance and baseline liver function. We retrospectively studied 50 lesions in 47 patients treated with SBRT (30-40 Gy in 5 fractions) for HCC, who were followed up for more than 6 months. After SBRT, all patients underwent regular follow-ups with blood tests and dynamic CT scans. At a median follow-up of 18.1 months (range 6.2-43.7 months), all lesions but one were controlled. 3 density patterns describing focal normal liver reactions around HCC tumours were identified in pre-contrast, arterial and portal-venous phase scans: iso/iso/iso in 4 patients (Type A), low/iso/iso in 8 patients (Type B) and low/iso (or high)/high in 38 patients (Type C). Imaging changes in the normal liver surrounding the treated HCC began at a median of 3 months after SBRT, peaked at a median of 6 months and disappeared 9 months later. Liver function, as assessed by the Child-Pugh classification, was the only factor that differed significantly between reactions to treatment showing "non-enhanced" (Type A and B) and "enhanced" (Type C) appearances in CT. Hence, liver tissue with preserved function is more likely to be well enhanced in the delayed phase of a dynamic contrast-enhanced CT scan. The CT appearances of normal liver seen in reaction to the treatment of an HCC by SBRT were therefore related to background liver function and should not be misread as recurrence of HCC.

[Transarterial chemoembolization and conformal radiotherapy for hepatocellular carcinoma]

Hepatocellular carcinoma is a poor prognosis tumour. The potential curative therapeutic options are orthotopic liver transplantation, surgical resection and radiofrequency ablation. Unfortunately, only a minority of patients (around 20%) are eligible for these techniques. Thus, patients can benefit from palliative options, such as transarterial chemoembolization (TACE) or sorafenib that bring only modest benefit on survival. Conformal radiotherapy allows delivering high dose radiation within a precise tumour volume while sparing the surrounding liver parenchyma. As employed in monotherapy, conformal radiotherapy is highly efficient for small size hepatocellular carcinoma (<5 cm). Above 5 cm, its efficacy is more limited but its association with TACE gives spectacular rates of complete responses. Controlled phase 2 or 3 trials are urgently warranted to define its indications in the therapeutic algorithm of hepatocellular carcinoma.

Clinical study of transarterial chemoembolization combined with 3-dimensional conformal radiotherapy for hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide. Monotherapy is not very effective for intermediate or advanced stage HCC. Efficacy of combined therapy using transarterial chemoembolization (TACE) with three-dimensional conformal radiotherapy (3-DCRT) for advanced HCC should be evaluated.

METHODS

HCC patients were selected from our patient database. The sequence of treatments that patients underwent was several courses of TACE followed in 2-4 weeks by 3-DCRT. The median tumor irradiation dose was 44Gy. Toxicity, tumor response, and overall survival rate were analyzed.

RESULTS

140 HCC patients were followed up by the last follow-up time. Among these patients, hepatic toxicities due to treatment were notable in 15 cases. Gastrointestinal bleeding after the overall treatment occurred in 3 cases. Leukopenia of grade III was detected in 1 case. Radiation-induced liver disease (RILD) was observed in 3 patients. Among 140 patients, 27, 97, and 16 cases achieved partial response, stable disease, and progressive disease, respectively. The overall survival rates of 1-year, 3-years, and 5-years were 66%, 29%, and 13%, respectively, with a median survival time of 18 months. Both Child-Pugh grade and radiation dose were determined to be independent predictors for overall survival from multivariate analysis.

CONCLUSION

The combined modality of TACE and 3-DCRT is a promising treatment for unresectable HCC. A large-scale, prospective randomized trial should be performed to confirm the utility of this combined therapy.

Radiotherapy and chemotherapy as therapeutic strategies in extrahepatic biliary duct carcinoma

PURPOSE

this report aims to provide an overview on radiotherapy and chemotherapy in extrahepatic biliary duct carcinoma (BDC).

PATIENTS AND METHODS

a PubMed research identified clinical trials in BDC through April 1, 2010 including randomised controlled trials, SEER analyses and retrospective trials. Additionally, publications on the technical progress of radiotherapy in or close to the liver were analysed.

RESULTS

most patients with cholangiocarcinoma present with unresectable disease (80-90%), and more than half of the resected patients relapse within 1 year. Adjuvant and palliative treatment options need to be chosen carefully since 50% of the patients are older than 70 years at diagnosis. Adjuvant radiotherapy or chemotherapy after complete resection (R0) has not convincingly shown a prolongation of survival but radiotherapy did after R1 resection. However, data suggest that liver transplantation could offer long-term survival in selected patients when combined with neoadjuvant chemoradiotherapy in patients with marginally resectable disease. For patients with unresectable biliary tract carcinoma (BTC), palliative stenting was previously the treatment of choice. But recent SEER analyses show that radiotherapy prolongs survival, relieves symptoms and contributes to biliary decompression and should be regarded as the new standard. Novel technical advances in radiotherapy may allow for dose-escalation and could significantly improve outcome for patients with cholangiocarcinoma.

CONCLUSION

both the literature and recent technical progress corroborate the role of radiotherapy in BDC offering chances for novel clinical trials. Progress is less pronounced in chemotherapy.

Dosimetric predictor identification for radiation-induced liver disease after hypofractionated conformal radiotherapy for primary liver carcinoma patients with Child-Pugh Grade A cirrhosis

PURPOSE

Radiation-induced liver disease (RILD) is the most severe complication in liver cancer treatment. The aim of this study was to identify dosimetric predictors for RILD in primary liver carcinoma (PLC) patients with Child-Pugh Grade A cirrhosis after hypofractionated conformal radiotherapy (CRT).

METHODS AND MATERIALS

A total of 114 eligible patients (mean age 45 years old) were enrolled and treated. The mean gross tumor volume (GTV) was (378.3±308.1) cm(3). A median dose of 53 Gy was delivered to the PLC by hypofractionated CRT (three fractions/week) with a median fraction size of 4.6 Gy (range: 4-6 Gy).

RESULTS

Patients were followed up for 1-79 months (median 19 months) after the completion of irradiation. RILD was diagnosed in nine (7.9%) patients. Univariate analyses revealed that GTV and the percentage of normal liver volume receiving more than 5-40 Gy irradiations (V(5-40)) were related to the risk of developing RILD. Multivariate analyses demonstrated that only GTV and V(20) were independent predictors. Using V(20) as the predictor for RILD, the accuracy, sensitivity, and specificity was 76.3%, 88.9%, and 75.2%, respectively.

CONCLUSIONS

Our data suggest that V(20) is the unique significant dosimetric predictor for RILD risks in PLC patients with Child-Pugh Grade A cirrhosis after hypofractionated CRT.

Early three-dimensional conformal radiotherapy for patients with unresectable hepatocellular carcinoma after incomplete transcatheter arterial chemoembolization: a prospective evaluation of efficacy and toxicity

PURPOSE

We prospectively evaluated the efficacy and toxicity of early 3-dimensional conformal radiotherapy (3D-CRT) for patients with unresectable hepatocellular carcinoma (HCC) after incomplete transcatheter arterial chemoembolization (TACE).

METHODS

Patients with unresectable HCC who failed 1 or 2 courses of TACE were eligible for this study. Three dimensional-CRT was added for HCC with incomplete uptake of iodized oil. Between January 2006 and February 2007, 40 patients (43 lesions) were enrolled. TACE was performed by using Lipiodol and adriamycin, followed by Gelfoam embolization. Two cycles of TACE were performed in 24 patients (60%), whereas 16 patients (40%) underwent one cycle. The median dose of 54 Gy (3 Gy daily) was delivered with 3D-CRT. Tumor response was evaluated by changes in tumor size on serial computed tomography scans and toxicity was evaluated by the Common Terminology Criteria for Adverse Events v3.0.

RESULTS

An objective response was achieved in 27 of 43 lesions (62.8%), with a complete response in 9 lesions (20.9%) and partial response in 18 lesions (41.9%). The overall survival rate was 72.0% at 1 year and 45.6% at 2 years. There was no grade 3 or greater acute toxicity. Nine patients (22.5%) showed progression of the disease within the irradiated field during the follow-up and intrahepatic metastases developed in 16 patients (40.0%).

CONCLUSION

Early 3D-CRT for HCC unresponsive to 1 or 2 cycles of TACE resulted in a 62.8% tumor response rate and relatively high complete response rates (20.9%) with acceptable toxicity. This study shows that the application of 3D-CRT could be considered for patients with incomplete TACE.

[Nonsurgical management of hepatocellular carcinoma]

Most of patients with hepatocellular carcinoma (HCC) cannot benefit from surgical therapies. Among nonsurgical options, only radiofrequency can challenge surgery for small size tumours. Conformal radiotherapy is likely highly efficient on solitary tumours, but controlled studies are warranted to conclude. Other options are purely palliative. Transarterial hepatic chemoembolization is the goal-standard for multifocal hepatocellular carcinoma and sorafenib for hepatocellular carcinoma with portal vein invasion, leading to modest but significant benefit on survival rates. Yttrium-90 radioembolization is under evaluation through controlled studies, and could be of major interest for multifocal hepatocellular carcinoma with or without portal venous invasion.

Prospective evaluation of microscopic extension using whole-mount preparation in patients with hepatocellular carcinoma: Definition of clinical target volume for radiotherapy

BACKGROUND

To define the clinical target volume (CTV) for radiotherapy in patients with hepatocellular carcinoma (HCC).

METHODS

A prospective study was conducted to histologically evaluate the presence and the distance of microscopic extension (ME) for resected HCC on the basis of examination of whole-mount preparations of carcinoma tissue sections.

RESULTS

A total of 380 whole-mount slides prepared from tumor samples of 76 patients with HCC were examined. Patients with elevated pretreatment AFP levels exhibited higher risk of ME as compared to those with normal pretreatment AFP levels (93.9% vs. 69.8%, P < 0.01). ME positivity was 16.7% for Grade 1, 79.1% for Grade 2, and 96.3% for Grade 3 tumors (P < 0.01). The mean distance of ME was 0.0 ± 0.1 mm (range 0-0.2 mm) for Grade 1, 0.9 ± 0.9 mm (range 0-4.5 mm) for Grade 2, and 1.9 ± 1.9 mm (range 0-8.0 mm) for Grade 3 tumors (P < 0.01).

CONCLUSIONS

The CTV margins for tumor Grades 1, 2, and 3 HCC, are recommended to be 0.2 mm, 4.5 mm, and 8.0 mm beyond the gross tumor margin, respectively, to account for possible ME of the tumors in all patients.

Emerging role of radiotherapy in the management of liver metastases

Improvements with systemic therapy in controlling occult metastatic disease in patients with colorectal cancer and other solid malignancies have raised renewed interest in local therapies that can treat isolated or "oligo" sites of metastatic disease within the liver. Radiotherapy (RT) is a treatment option that can be offered to patients unsuitable for surgery or other ablative therapies. Technological advances in RT planning and delivery have made it possible to administer high doses conformally around focal liver metastases effectively. Methods to facilitate safe delivery of high-dose RT include conformal RT planning, stereotactic body RT, breathing motion management, and image-guided RT. The clinical experience in conformal RT and stereotactic body RT for liver metastases is emerging, with phase I and II trials demonstrating excellent local control and occasional long-term survivors. With appropriate patient selection and sparing of the uninvolved liver, serious toxicity can be avoided. Out-of-field recurrences are common, providing rationale for combining systemic or regional therapies with RT for these patients. Finally, randomized trials of RT for liver metastases are needed to better define the benefits of RT for these patients.

Phase I feasibility trial of stereotactic body radiation therapy for primary hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is increasing in incidence and the majority of patients are not candidates for radical therapies. Therefore, interest in minimally invasive therapies in growing.

METHODS

A Phase I dose escalation trial was conducted at Indiana University to determine the feasibility and toxicity of stereotactic body radiation therapy (SBRT) for primary HCC. Eligible patients had Child-Turcotte-Pugh's Class (CTP) A or B, were not candidates for resection, had 1-3 lesions and cumulative tumour diameter less than or equal to 6 cm. Dose escalation started at 36 Gy in 3 fractions (12 Gy/fraction) with a subsequent planned escalation of 2 Gy/ fraction/level. Dose-limiting toxicity (DLT) was defined as Common Terminology Criteria for Adverse Events v3.0 grade 3 or greater toxicity.

RESULTS

Seventeen patients with 25 lesions were enrolled. Dose was escalated to 48 Gy (16 Gy/fraction) in CTP-A patients without DLT. Two patients with CPC-B disease developed grade 3 hepatic toxicity at the 42-Gy (14 Gy/fraction) level. The protocol was amended for subsequent CTP-B patients to receive a regimen of 5 fractions starting at 40 Gy (8 Gy/fraction) with one patient experiencing progressive liver failure. Four additional patients were enrolled (one died of unrelated causes after an incomplete SBRT course) without DLT. The only factor related to more than one grade 3 or greater liver toxicity or death within 6 months was the CTP score (p=0.03). Six patients underwent a liver transplant. Ten patients are alive without progression with a median FU of 24 months (10-42 months), with local control/stabilisation of the disease of 100%. One and two-year Kaplan-Meier estimates for overall survival are 75% and 60%, respectively.

CONCLUSIONS

SBRT is a non-invasive feasible and well tolerated therapy in adequately selected patients with HCC. The preliminary local control and survival are encouraging. A confirmatory Phase II trial is currently open to accrual.

Yttrium-90 radioembolization in the management of liver malignancies

Primary and secondary liver tumors are common. Locoregional therapies are establishing a role in the management of liver tumors due to the limited roles of surgical and systemic therapies. Our review presents some general concepts associated with yttrium-90 radioembolization and its specific utilization in various primary and secondary liver malignancies.

Biological impact of geometric uncertainties: what margin is needed for intra-hepatic tumors?

Background

To evaluate and compare the biological impact on different proposed margin recipes for the same geometric uncertainties for intra-hepatic tumors with different tumor cell types or clinical stages.

Method

Three different margin recipes based on tumor motion were applied to sixteen IMRT plans with a total of twenty two intra-hepatic tumors. One recipe used the full amplitude of motion measured from patients to generate margins. A second used 70% of the full amplitude of motion, while the third had no margin for motion. The biological effects of geometric uncertainty in these three situations were evaluated with Equivalent Uniform Doses (EUD) for various survival fractions at 2 Gy (SF₂).

Results

There was no significant difference in the biological impact between the full motion margin and the 70% motion margin. Also, there was no significant difference between different tumor cell types. When the margin for motion was eliminated, the difference of the biological impact was significant among different cell types due to geometric uncertainties. Elimination of the motion margin requires dose escalation to compensate for the biological dose reduction due to the geometric misses during treatment.

Conclusions

Both patient-based margins of full motion and of 70% motion are sufficient to prevent serious dosimetric error. Clinical implementation of margin reduction should consider the tumor sensitivity to radiation.

Three-dimensional conformal radiation therapy and intensity-modulated radiation therapy combined with transcatheter arterial chemoembolization for locally advanced hepatocellular carcinoma: an irradiation dose escalation study

PURPOSE

To determine the maximum tolerated dose (MTD) of three-dimensional conformal radiation therapy (3DCRT)/intensity-modulated radiation therapy (IMRT) combined with transcatheter arterial chemoembolization for locally advanced hepatocellular carcinoma.

METHODS AND MATERIALS

Patients were assigned to two subgroups based on tumor diameter: Group 1 had tumors <10 cm; Group II had tumors ≥10 cm. Escalation was achieved by increments of 4.0 Gy for each cohort in both groups. Dose-limiting toxicity (DLT) was defined as a grade of ≥3 acute liver or gastrointestinal toxicity or any grade 5 acute toxicity in other organs at risk or radiation-induced liver disease. The dose escalation would be terminated when ≥2 of 8 patients in a cohort experienced DLT.

RESULTS

From April 2005 to May 2008, 40 patients were enrolled. In Group I, 11 patients had grade ≤2 acute treatment-related toxicities, and no patient experienced DLT; and in Group II, 10 patients had grade ≤2 acute toxicity, and 1 patient in the group receiving 52 Gy developed radiation-induced liver disease. MTD was 62 Gy for Group I and 52 Gy for Group II. In-field progression-free and local progression-free rates were 100% and 69% at 1 year, and 93% and 44% at 2 years, respectively. Distant metastasis rates were 6% at 1 year and 15% at 2 years. Overall survival rates for 1-year and 2-years were 72% and 62%, respectively.

CONCLUSIONS

The irradiation dose was safely escalated in hepatocellular carcinoma patients by using 3DCRT/IMRT with an active breathing coordinator. MTD was 62 Gy and 52 Gy for patients with tumor diameters of <10 cm and ≥10 cm, respectively.

Intra-arterial therapies for hepatocellular carcinoma: where do we stand?

PURPOSE AND DESIGN

Intra-arterial therapies for unresectable hepatocellular carcinoma (HCC) consist of a catheter-based group of treatments where therapeutic and/or embolic agents are intra-arterially directed to target tumors. Here we review these therapies, which may be classified into embolotherapy/chemotherapy-based and radiotherapy-based treatments. Embolotherapy/chemotherapy-based treatments include transcatheter arterial embolization, transarterial chemoembolization, transcatheter arterial chemoeinfusion, and chemoembolization with drug-eluting beads. Radiotherapy-based treatments include radioembolization with yttrium-90 and injection of iodine-131-labeled lipiodol.

RESULTS AND CONCLUSION

Interpretation of the results of clinical trials as well as implementation of meta-analyses involving the efficacy of intra-arterial therapies for unresectable HCC has been challenging and difficult to perform. The levels of evidence for treatment recommendations in oncology provide a common framework to understand the current status of intra-arterial therapies for HCC. Here we use an evidence-based approach to critically review and comprehend the current role and future potential of intra-arterial therapies in unresectable HCC.

Dose-escalation study of single-fraction stereotactic body radiotherapy for liver malignancies

PURPOSE

We performed a Phase I dose-escalation study to explore the feasibility and safety of treating primary and metastatic liver tumors with single-fraction stereotactic body radiotherapy (SBRT).

METHODS AND MATERIALS

Between February 2004 and February 2008, 26 patients were treated for 40 identifiable lesions. Nineteen patients had hepatic metastases, 5 had intrahepatic cholangiocarcinomas, and 2 had recurrent hepatocellular carcinomas. The prescribed radiation dose was escalated from 18 to 30 Gy at 4-Gy increments with a planned maximum dose of 30 Gy. Cumulative incidence functions accounted for competing risks to estimate local failure (LF) incidence over time under the competing risk of death.

RESULTS

All patients tolerated the single-fraction SBRT well without developing a dose-limiting toxicity. Nine acute Grade 1 toxicities, one acute Grade 2 toxicity, and two late Grade 2 gastrointestinal toxicities were observed. After a median of 17 months follow-up (range, 2-55 months), the cumulative risk of LF at 12 months was 23%. Fifteen patients have died: 11 treated for liver metastases and 4 with primary liver tumors died. The median survival was 28.6 months, and the 2-year actuarial overall survival was 50.4%.

CONCLUSIONS

It is feasible and safe to deliver single-fraction, high-dose SBRT to primary or metastatic liver malignancies measuring ≤5 cm. Moreover, single-fraction SBRT for liver lesions demonstrated promising local tumor control with minimal acute and long-term toxicity. Single-fraction SBRT appears to be a viable nonsurgical option, but further studies are warranted to evaluate both control rates and impact on quality of life.

Stereotactic body radiation therapy for colorectal liver metastases

BACKGROUND

Stereotactic body radiation therapy (SBRT) is a treatment option for colorectal liver metastases. Local control, patient survival and toxicity were assessed in an experience of SBRT for colorectal liver metastases.

METHODS

SBRT was delivered with curative intent to 20 consecutively treated patients with colorectal hepatic metastases who were candidates for neither resection nor radiofrequency ablation (RFA). The median number of metastases was 1 (range 1-3) and median size was 2.3 (range 0.7-6.2) cm. Toxicity was scored according to the Common Toxicity Criteria version 3.0. Local control rates were derived on tumour-based analysis.

RESULTS

Median follow-up was 26 (range 6-57) months. Local failure was observed in nine of 31 lesions after a median interval of 22 (range 12-52) months. Actuarial 2-year local control and survival rates were 74 and 83 per cent respectively. Hepatic toxicity grade 2 or less was reported in 18 patients. Two patients had an episode of hepatic toxicity grade 3.

CONCLUSION

SBRT is a treatment option for patients with colorectal liver metastases who are not candidates for resection or RFA.

Treatment of hepatocellular carcinoma with intra-arterial injection of radionuclides

Hepatocellular carcinoma (HCC) is becoming an important public health concern. Current therapeutic options are limited and new treatments are therefore being developed. The intra-arterial treatment chemoembolization has limited efficacy and few prospects for further progress. One particularly promising, though little used, alternative to chemoembolization is radioembolization with iodine-131 ((131)I) or rhenium-188 labeled lipiodol or yttrium-90 labeled microspheres (glass or resin beads). Three randomized studies have proven the effectiveness of (131)I-lipiodol in patients with HCC-as adjuvant therapy after surgery, compared with chemoembolization, and also in patients who have portal vein thrombosis. Microspheres enable the delivery of high-dose radiation (>200 Gy) to the tumor while sparing the neighboring hepatic tissue from overexposure. Overall, the efficacy of radioembolization has been good and toxic effects have been low. These results are comparable to those obtained with chemoembolization but further improvement can be expected by combining radioembolization with standard chemotherapy or with targeted therapies, such as anti-angiogenic drugs.

Accelerated treatment using intensity-modulated radiation therapy plus concurrent capecitabine for unresectable hepatocellular carcinoma

BACKGROUND

: Patients with unresectable hepatocellular carcinoma (HCC) have limited treatment options. In this study, the authors investigated the feasibility, toxicity, and efficacy associated with intensity-modulated radiation therapy (IMRT) and concurrent, chronomodulated capecitabine in the treatment of unresectable HCC.

METHODS

: Twenty patients underwent treatment planning for HCC confined to the liver with helical tomotherapy-based IMRT. Fifty-five percent of patients had Child-Pugh Class A disease, and 45% of patients had Class B disease. Ninety-five percent of patients were prescribed 50 gray (Gy) of radiotherapy to the planning target volume delivered in 20 fractions with concurrent, chronomodulated capecitabine. Transcatheter arterial chemoembolization preceded radiotherapy in 11 patients, and 9 patients received IMRT alone because of portal vein thrombosis, esophageal varices, or tumor size.

RESULTS

: The mean greatest tumor dimension was 9 cm (range, 1.3-17.4 cm), the mean dose to normal liver was 22.6 Gy (range, 10-29.2 Gy), and the average volume of liver that received >30 Gy (V30) was 27.2% (range, 12%-43%). Eighteen patients (90%) completed the prescribed treatment of 50 Gy. There was no increase from baseline in acute or late toxicity greater than 2 grades. Partial response or disease stability was achieved at 3 months to 6 months after treatment in 15 of 16 patients (94%). The median survival (+/-standard deviation) for patients who had Child-Pugh Class A and B disease was 22.5 +/- 5.1 months and 8 +/- 3.3 months, respectively.

CONCLUSIONS

: In this initial experience with accelerated IMRT plus capecitabine for patients who had large HCC lesions, the results demonstrated acceptable toxicity with promising local control. The relatively low acute and late toxicity observed with this program suggested that dose intensification can be incorporated into the treatment regimen if needed. Cancer 2009. (c) 2009 American Cancer Society.

Stereotactic body radiation therapy: a novel treatment modality

Stereotactic body radiation therapy (SBRT) involves the delivery of a small number of ultra-high doses of radiation to a target volume using very advanced technology and has emerged as a novel treatment modality for cancer. The role of SBRT is most important at two cancer stages-in early primary cancer and in oligometastatic disease. This modality has been used in the treatment of early-stage non-small-cell lung cancer, prostate cancer, renal-cell carcinoma, and liver cancer, and in the treatment of oligometastases in the lung, liver, and spine. A large body of evidence on the use of SBRT for the treatment of primary and metastatic tumors in various sites has accumulated over the past 10-15 years, and efficacy and safety have been demonstrated. Several prospective clinical trials of SBRT for various sites have been conducted, and several other trials are currently being planned. The results of these clinical trials will better define the role of SBRT in cancer management. This article will review the radiobiologic, technical, and clinical aspects of SBRT.

Challenge and hope in radiotherapy of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most critical global health issues. With frequent association of viral liver disease, HCC is highly complex, harboring both cancer and chronic liver disease. The tumor stage and underlying liver function are both major determinants of the treatment selection as well as prognosis in HCC patients, thus allowing no more than a 20% chance for potentially curative therapies. Radiotherapy technology has been evolved remarkably during the past decade, and radiation can be precisely delivered, thereby permitting higher doses to the tumour and reduced doses to surrounding normal tissues. There has been increasing interest in the merits of radiotherapy in HCC over the past few years, as indicated by a Pub Med search. Radiotherapy has been used as the definitive therapy with curative intent in early stage tumours. It has been used also in combination with TACE for intermediate stage tumours. In locally advanced tumours, radiotherapy has been combined with systemic agents. Despite its efficacy, radiotherapy has not yet been incorporated into the standard management guidelines of HCC. The lack of high evidence level data, especially randomized controlled trials, has posed an obstacle in including radiotherapy into the routine treatment schema of HCC. Therefore, well-designed prospective studies are strongly recommended using developing technology for radiotherapy alone or combination therapies. Also, many issues such as the optimal dose-fractionation, intra- or extrahepatic metastasis after radiotherapy, and radiation-induced hepatic dysfunction remain to be solved. In this review, current status of radiotherapy for HCC will be discussed with regard to technical consideration and combination strategy. The limitation and future perspectives will also be discussed.

Predictive factors of gastroduodenal toxicity in cirrhotic patients after three-dimensional conformal radiotherapy for hepatocellular carcinoma

BACKGROUND AND PURPOSE

To identify predictive factors for the development of gastroduodenal toxicity (GDT) in cirrhotic patients treated with three-dimensional conformal radiotherapy (3D-CRT) for hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

We retrospectively analyzed dose-volume histograms (DVHs) and clinical records of 73 cirrhotic patients treated with 3D-CRT for HCC. The median radiation dose was 36 Gy (range, 30-54 Gy) with a daily dose of 3 Gy. The grade of GDT was defined by the Common Toxicity Criteria Version 2. The predictive factors of grade 3 GDT were identified.

RESULTS

Grade 3 GDT was found in 9 patients. Patient's age and the percentage of gastroduodenal volume receiving more than 35 Gy (V(35)) significantly affected the development of grade 3 GDT. Patients over 50 years of age developed grade 3 GDT more frequently than patients under 50 years of age. The risk of grade 3 GDT grew exponentially as V(35) increased. The 1-year actuarial rate of grade 3 GDT in patients with V(35)<5% is significantly lower than that in patients with a V(35)> or =5% (4% vs. 48%, p<.01).

CONCLUSIONS

Patient's age and V(35) were the most predictive factors for the development of grade 3 GDT in patients treated with RT.

125I Radioactive Seeds Implantation Therapy for Hepatocellular Carcinoma

BACKGROUND

This study was to evaluate the outcome and the prognostic factors of unresectable hepatocellular carcinoma (HCC) patients with ¹²⁵I radioactive seeds implantation, who had failed transcatheter arterial chemoembolization (TACE).

METHODS

From September 2002 to March 2006, 48 patients with unresectable HCC underwent ¹²⁵I permanent implantation brachytherapy. Thirty-eight patients were male and 10 were female. Mean age was 59 years, ranginging from 32 to 86. Karnofsky performance status(KPS) was 100 in 10 patients, 80 in 21 patients, and 60 in 17 patients. According to Child-Pugh classification of liver, 34 patients were in class A and 14 patients in class B. Twenty-two patients had alpha-fetoprotein (AFP) level > 400 ng/ml. Tumor size was < 5cm in 17 patients, 5-10 cm in 18 patients, and > 10cm in 13 patients. Thirty-four patients had confluent tumors, 14 patients presented single hepatic tumor. Serum hepatitis antigen markers were positive for type B in 38 patients and type C in 10 patients. Twenty-two patients had Okuda Stage I, 24 patients Stage II, and 2 patients Stage III. According to the AJCC staging system (6th edition), 10 patients were in Stage II (T2N0M0), 20 in Stage IIIa (T3N0M0) and 18 in Stage IIIb (T4N0M0).

RESULTS

An objective response was observed in 34 of 48 patients, giving a response rate of 70.8%. The survival rates at 1, 2 and 3 years were75%, 45.8% and 27.1%, respectively. In the analysis of prognostic factors, tumor type, tumor size, Okuda stage, AJCC stage, Liver Child-Pugh, pretreatment AFP level, and matched peripheral dose (MPD) all had significant impact on survival.

CONCLUSIONS

The ¹²⁵I permanent implantation brachytherapy induced a substantial tumor response rate of 70.8% with survival rates at 1, 2 and 3 years of 75%, 45.8% and 27.1%, respectively, and a median survival time of 15.5 months in patients with unresectable HCC who had failed TACE. The complications are acceptable and can be managed with conservative treatment. Although we do not know whether there is a survival benefit through the use of this treatment, ¹²⁵I permanent implantation brachytherapy seems to be a practical method of salvage for this subset of patients. Further study is warranted to evaluate the survival of such patients with controlled trial.

Proton beam therapy for large hepatocellular carcinoma

PURPOSE

To investigate the safety and efficacy of proton beam therapy (PBT) in patients with large hepatocellular carcinoma (HCC).

METHODS AND MATERIALS

Twenty-two patients with HCC larger than 10 cm were treated with proton beam therapy at our institution between 1985 and 2006. Twenty-one of the 22 patients were not surgical candidates because of advanced HCC, intercurrent disease, or old age. Median tumor size was 11 cm (range, 10-14 cm), and median clinical target volume was 567 cm(3) (range, 335-1,398 cm(3)). Hepatocellular carcinoma was solitary in 18 patients and multifocal in 4 patients. Tumor types were nodular and diffuse in 18 and 4 patients, respectively. Portal vein tumor thrombosis was present in 11 patients. Median total dose delivered was 72.6 GyE in 22 fractions (range, 47.3-89.1 GyE in 10-35 fractions).

RESULTS

The median follow-up period was 13.4 months (range, 1.5-85 months). Tumor control rate at 2 years was 87%. One-year overall and progression-free survival rates were 64% and 62%, respectively. Two-year overall and progression-free survival rates were 36% and 24%, respectively. The predominant tumor progression pattern was new hepatic tumor development outside the irradiated field. No late treatment-related toxicity of Grade 3 or higher was observed.

CONCLUSIONS

The Bragg peak properties of PBT allow for improved conformality of the treatment field. As such, large tumor volumes can be irradiated to high doses without significant dose exposure to surrounding normal tissue. Proton beam therapy therefore represents a promising modality for the treatment of large-volume HCC. Our study shows that PBT is an effective and safe method for the treatment of patients with large HCC.

Extrapolation of normal tissue complication probability for different fractionations in liver irradiation

PURPOSE

The ability to predict normal tissue complication probability (NTCP) is essential for NTCP-based treatment planning. The purpose of this work is to estimate the Lyman NTCP model parameters for liver irradiation from published clinical data of different fractionation regimens. A new expression of normalized total dose (NTD) is proposed to convert NTCP data between different treatment schemes.

METHOD AND MATERIALS

The NTCP data of radiation- induced liver disease (RILD) from external beam radiation therapy for primary liver cancer patients were selected for analysis. The data were collected from 4 institutions for tumor sizes in the range of of 8-10 cm. The dose per fraction ranged from 1.5 Gy to 6 Gy. A modified linear-quadratic model with two components corresponding to radiosensitive and radioresistant cells in the normal liver tissue was proposed to understand the new NTD formalism.

RESULTS

There are five parameters in the model: TD(50), m, n, alpha/beta and f. With two parameters n and alpha/beta fixed to be 1.0 and 2.0 Gy, respectively, the extracted parameters from the fitting are TD(50)(1) = 40.3 +/- 8.4Gy, m =0.36 +/- 0.09, f = 0.156 +/- 0.074 Gy and TD(50)(1) = 23.9 +/- 5.3Gy, m = 0.41 +/- 0.15, f = 0.0 +/- 0.04 Gy for patients with liver cirrhosis scores of Child-Pugh A and Child-Pugh B, respectively. The fitting results showed that the liver cirrhosis score significantly affects fractional dose dependence of NTD.

CONCLUSION

The Lyman parameters generated presently and the new form of NTD may be used to predict NTCP for treatment planning of innovative liver irradiation with different fractionations, such as hypofractioned stereotactic body radiation therapy.

A multicenter retrospective cohort study of practice patterns and clinical outcome on radiotherapy for hepatocellular carcinoma in Korea

AIM

To determine the national practice processes of care and outcomes of radiotherapy for hepatocellular carcinoma (HCC) in Korea.

PATIENTS AND METHODS

A national survey of 53 institutions nationwide was conducted by requesting data on their experience of radiotherapy for HCC. Among them, 10 institutions were selected for performing more detailed analysis, based on the radiotherapy experience of at least five HCC patients between 2004 and 2005.

RESULTS

This study covered the treatment of 398 HCC patients for 2 years. Most patients (78%) were in stage III or IV. Radiotherapy was chosen after the failure of other treatments, most frequently transarterial chemoembolization. Radiotherapy was performed predominantly using the three-dimensional conformal technique (3D-CRT, 81.9%) mostly with a total dose of >/=45 Gy. In 9.3% of the patients, radiotherapy was performed using radiosurgery. In a biologically effective dose (BED) with 10 Gy of alpha/beta, 4.2-124.3 Gy(10) was delivered. The median survival time was 12 months, and the 2-year overall survival rate was 27.9%. A tumour size <5 cm, a negative lymph node and BED >53.1 Gy(10) were shown by multivariate analysis to be significant factors for a better prognosis. In a subset analysis for the 326 patients treated with 3D-CRT, better liver function with Child-Pugh class A was shown to be an additional factor for a better prognosis.

CONCLUSIONS

Radiotherapy has been used to treat advanced HCC in various modes, but mostly as a salvage treatment. Although this study was retrospective, it indicates that radiotherapy is a quite effective modality for HCC patients.

Treatment parameters and outcome in 680 treatments of internal radiation with resin 90Y-microspheres for unresectable hepatic tumors

PURPOSE

Radioembolization (RE) using (90)Y-microspheres is an effective and safe treatment for patients with unresectable liver malignancies. Radiation-induced liver disease (RILD) is rare after RE; however, greater understanding of radiation-related factors leading to serious liver toxicity is needed.

METHODS AND MATERIALS

Retrospective review of radiation parameters was performed. All data pertaining to demographics, tumor, radiation, and outcomes were analyzed for significance and dependencies to develop a predictive model for RILD. Toxicity was scored using the National Cancer Institute Common Toxicity Criteria Adverse Events Version 3.0 scale.

RESULTS

A total of 515 patients (287 men; 228 women) from 14 US and 2 EU centers underwent 680 separate RE treatments with resin (90)Y-microspheres in 2003-2006. Multifactorial analyses identified factors related to toxicity, including activity (GBq) Selective Internal Radiation Therapy delivered (p < 0.0001), prescribed (GBq) activity (p < 0.0001), percentage of empiric activity (GBq) delivered (p < 0.0001), number of prior liver treatments (p < 0.0008), and medical center (p < 0.0001). The RILD was diagnosed in 28 of 680 treatments (4%), with 21 of 28 cases (75%) from one center, which used the empiric method.

CONCLUSIONS

There was an association between the empiric method, percentage of calculated activity delivered to the patient, and the most severe toxicity, RILD. A predictive model for RILD is not yet possible given the large variance in these data.

Innovative therapy for hepatocellular carcinoma: three-dimensional high-dose photon radiotherapy

The development of three-dimensional conformal radiotherapy (3DCRT) has enabled high dose radiation to be directed to tumour with a frank sparing of the non-tumour surrounding liver parenchyma without restriction due to tumour topography and size, presence of peritumourous satellite nodules or associated segmental portal vein thrombosis. 3DCRT can be safely delivered alone or concomitantly with transarterial chemoembolization (TACE), giving very encouraging results. Efficacy is strongly related to a smaller tumor size and higher dose of radiation while toxicity closely correlates to the pre-radiotherapy liver functions and the dose delivered to the uninvolved liver. These data has led to integrate 3DCRT in the multimodal treatment of HCC as a possible curative-intent option as well as surgical resection or percutaneous procedures although phase-III controlled studies are warranted to clarify this point. This may represent a promising approach in patients who are inoperable or for whom other ablation therapies are not feasible. The next steps will be the optimization of delivery modes of this type of photon therapy, taking account that other radiation modalities such as proton beam therapy for instance might be shown as of great interest within the next few years.

Options for radiotherapy in the treatment of liver metastases

Technologic advances have provided the means to deliver tumoricidal doses of radiation therapy (RT) to patients with unresectable colorectal liver metastases, while avoiding critical normal tissues, providing the opportunity to use RT for curative intent treatment of metastatic disease. For the current report, the expanded role of RT, with its different techniques in the setting of metastatic colorectal cancer, from palliation to cure was reviewed.

Regional infusion-radioembolization

Selective internal radiation therapy involves the intra-arterial delivery of radioactive beads to the tumor while minimizing dosing to the adjacent organ. Because this technique invariably results in some degree of embolization, it has also been termed radioembolization. More than 8000 patients have been treated worldwide, with a large body of experience with primary hepatocellular carcinoma (HCC) and metastatic colorectal carcinoma (MCRC) and growing experience with other tumors (metastatic neuroendocrine, breast carcinoma, cholangiocarcinoma). Response rates by FDG-PET are 80% to 90%. Complications are uncommon and most often consist of self-limited malaise. More significant complications, including radiation-induced liver disease, ischemic cholecystitis, and gastrointestinal ulceration may be seen in up to 10% of patients. This underscores the critical importance of patient selection and meticulous technique. Median survival times in patients who have HCC and MCRC are significantly improved compared with historic controls. Further study is required to determine the appropriate role of radioembolization in the context of state-of-the-art chemotherapy and other liver-directed therapies.

Pilot clinical trial of localized concurrent chemoradiation therapy for locally advanced hepatocellular carcinoma with portal vein thrombosis

BACKGROUND

Patients with advanced hepatocellular carcinoma (HCC) with portal vein thrombosis (PVT) have a particularly grave prognosis. In the current study, an attempt was made to localize chemoradiation therapy (CCRT) followed by hepatic arterial infusion chemotherapy (HAIC) in patients with locally advanced HCC with PVT and good reserve liver function. The objective of the current study was to evaluate the therapeutic effect of localized CCRT followed by HAIC as a new treatment modality for these patients.

METHODS

Between January 1998 and December 2003, 40 patients were recruited. Concurrent regional chemotherapy using an intra-arterial implanted port plus localized external beam radiotherapy was performed with a total of 45 gray (Gy) over 5 weeks with conventional fractionation and hepatic arterial infusion of 5-fluorouracil (5-FU), which was administered during the first and fifth weeks of radiotherapy. One month after localized CCRT, HAIC with 5-FU and cisplatin was administered every 4 weeks.

RESULTS

One month after localized CCRT, an objective response was observed on the intention-to-treat analysis in 18 of 40 patients (45%). The actuarial 3-year overall survival rate was 24.1% and the median survival time was 13.1 months from the start of radiation treatment. Responders after localized CCRT demonstrated significantly better survival (P = .033) than nonresponders.

CONCLUSIONS

The substantial response rate as well as median survival time noted in the current study encourages the use of this new approach in patients with locally advanced HCC with PVT.

Hepatocellular carcinoma: radiation therapy

Although whole liver tolerance to radiation therapy (RT) is low, hepatocellular carcinoma (HCC) can be treated with focal high-dose RT, using a variety of advanced and specialized treatment strategies. Technical advancements in external beam RT that facilitate the safe delivery of RT to a wide spectrum of patients include conformal RT planning, breathing motion management, and image-guided RT. A variety of doses and RT fractionation schemes have been used safely alone or in combination with other therapies such as transarterial chemoembolization. Charged particles, produced from very specialized treatment units, are associated with particularly desirable dose distributions allowing tumoricidal doses to be delivered with sustained tumor control and little toxicity, even in the presence of Child-Pugh class B or C cirrhosis. Another strategy to deliver RT to HCC is hepatic arterial delivery of radioisotopes, such as microspheres tagged with yttrium-90. Liver toxicity is more likely in patients with reduced liver reserve and/or tumors infiltrating the majority of the liver. Phase II studies and a small phase III trial have demonstrated activity of hepatic arterial radioisotopes in HCC, providing rationale for large confirmatory randomized trials. Recurrences after RT occur most often within the liver, outside the high-dose irradiated volume, and outcomes after RT to very large and/or diffuse HCC are poor, providing rationale for combining RT with other therapies or novel radiation sensitizers. Given the vascular properties of HCC, there is rationale for investigating RT with anti-vascular endothelial growth factor-targeted agents.

Fibrosis, portal hypertension, and hepatic volume changes induced by intra-arterial radiotherapy with 90yttrium microspheres

PURPOSE

To identify changes in hepatic parenchymal volume, fibrosis, and induction of portal hypertension following radioembolization with glass microspheres for patients with metastatic disease to the liver.

RESULTS

In our series of sequential bilobar (n = 17) treatments, a mean decrease in liver volume of 11.8% was noted. In this group, a mean splenic volume increase of 27.9% and portal vein diameter increase of 4.8% were noted. For patients receiving unilobar treatments (n = 15), mean ipsilateral lobar volume decrease of 8.9%, contralateral lobar hypertrophy of 21.2%, and a 5.4% increase in portal vein diameter were also noted. These findings were not associated with clinical toxicities.

CONCLUSION

(90)Yttrium radioembolization utilizing glass microspheres in patients with liver metastases results in changes of hepatic parenchymal volume and also induced findings suggestive of fibrosis and portal hypertension. Further studies assessing the long-term effects are warranted.

Radiotherapy for 65 patients with advanced unresectable hepatocellular carcinoma

AIM: To evaluate the efficacy of radiotherapy (RT) in patients with advanced unresectable hepatocellular carcinoma (HCC).

METHODS: A total of 65 patients were treated with RT in the Korea University Medical Center. The median age of the patients was 60 years, and 86.2% were men. 18.5% and 81.5% of the patients were diagnosed as TNM stage III and IV-A, respectively. Treatment response was assessed 4 mo after initiation of RT. Tumor regression rate 1 mo after initiation of RT (TRR_1m) was also assessed. Duration of survival was calculated from the initiation of RT.

RESULTS: The objective treatment response was 56.9%. The 12 mo survival rate was 34.7%. Predictive factors for survival were Child-Pugh grade, α-fetoprotein level and treatment response. An objective response was achieved more frequently in patients with TRR_1m≥ 20% than in those with TRR_1m < 20% (P < 0.001).

CONCLUSION: RT is effective in treating advanced HCC with a tumor response rate of 56.9%.

Estimate of radiobiologic parameters from clinical data for biologically based treatment planning for liver irradiation

PURPOSE

The Radiation Therapy Oncology Group (RTOG) is initiating a few new hypofractionation regimens (RTOG 0438) to treat liver cancer patients. To evaluate the radiobiologic equivalence between different regimens requires reliable radiobiologic parameters. The purpose of this work is to estimate a plausible set of such parameters for liver tumors and to design new optimized dose fractionation schemes to increase patient survival.

METHODS AND MATERIALS

A model was developed to fit clinical survival data from irradiation of a series of primary liver patients. The model consists of six parameters including radiosensitivity parameters alpha and alpha/beta, potential doubling time T(d). Using this model together with the Lyman model for calculations of the normal tissue complication probability, we designed a series of hypofractionated treatment strategies for liver irradiation.

RESULTS

The radiobiologic parameters for liver tumors were estimated to be: alpha/beta = 15.0 +/- 2.0 Gy, alpha = 0.010 +/- 0.001 Gy (-1), T(d) = 128 +/- 12 day. By calculating the biologically effective dose using the obtained parameters, it is found that for liver patients with an effective liver volume of approximately 45% the dose fractionation regimens suggested in RTOG 0438 can be escalated to higher dose for improved patient survival ( approximately 80% at 1 year) while keeping the normal tissue complication probability to less than 10%.

CONCLUSIONS

A plausible set of radiobiologic parameters has been obtained based on clinical data. These parameters may be used for radiation treatment planning of liver tumors, in particular, for the design of new treatment regimens aimed at dose escalation.

Radioembolization for the treatment of unresectable hepatocellular carcinoma: A clinical review

Hepatocellular carcinoma (HCC) is the sixth most common cancer in the world. The majority of patients with HCC present with unresectable disease. These patients have historically had limited treatment options secondary to HCC demonstrating chemoresistance to the currently available systemic therapies. Additionally, normal liver parenchyma has shown intolerance to tumoricidal radiation doses, limiting the use of external beam radiation. Because of these limitations, novel percutaneous liver-directed therapies have emerged. The targeted infusion of radioactive microspheres (radioembolization) represents one such therapy. Radioembolization is a minimally invasive transcatheter therapy through which radioactive microspheres are infused into the hepatic arteries that supply tumor. Once infused, these microspheres traverse the hepatic vascular plexus and selectively implant within the tumor arterioles. Embedded within the arterioles, the ⁹⁰Y impregnated microspheres emit high energy and low penetrating radiation doses selectively to the tumor. Radioembolization has recently shown promise for the treatment of patients with unresectable HCC. The objective of this review article is to highlight two currently available radioembolic devices (⁹⁰Y, ¹⁸⁸Rh) and provide the reader with a recent review of the literature.

Application of active breathing control in 3-dimensional conformal radiation therapy for hepatocellular carcinoma: the feasibility and benefit

BACKGROUND AND PURPOSE

To investigate the feasibility and effectiveness of utilizing active breathing coordinator (ABC) in 3DCRT for HCC.

MATERIALS AND METHODS

A dosimetric comparison between the free-breathing (FB) plan and ABC plan in HCC 3DCRT was performed. Set-up errors and reproducibility of diaphragm position using ABC were measured, and patients' acceptance was also recorded.

RESULTS

From April 2005 to February 2007, 28 HCC were irradiated with ABC and they tolerated ABC well. The mean dose to normal liver was reduced from 16.9Gy in FB plan to 14.3Gy in ABC plan. PTV for ABC and FB plans were 529cm(3) and 781cm(3), respectively, and V(23) were reduced from 45% to 30%. The predicted incidences of radiation-induced liver disease by Lyman model were 1% and 2.5%, respectively, in favor of ABC plan. The systematic and random errors for the ABC and FB plans were 1.2mm vs. 4.7mm, 1.6mm vs. 3.5mm, and 1.8mm vs. 2.7mm, respectively, in cranio-caudal, anterior-posterior, and left-right directions. The average intrafraction reproducibility of diaphragm position in cranio-caudal direction was 1.6mm, and the interfraction, 6.7mm.

CONCLUSIONS

The utilization of ABC in HCC 3DCRT is feasible, and can reduce liver irradiation.

Conformal radiotherapy for hepatocellular carcinoma

Technical advancements in radiation therapy (RT) have facilitated the safe delivery of conformal, dose-escalated radiation to a wide spectrum of hepatocellular carcinoma (HCC) patients. A variety of doses and RT fractionation schemes have been used, and RT has been used in combination with transarterial chemoembolization (TACE). Compared to untreated historical controls or those treated with TACE alone, outcomes following RT alone or TACE and RT are better. Despite advances in RT delivery, liver toxicity following RT remains a dose-limiting factor, and investigations to better understand the pathophysiology of RT-induced liver toxicity are warranted. For most tumors, RT can provide sustained local control. However, HCC tends to recur within the liver away from the irradiated volume, providing rationale for combining RT with systemic or regional therapies. There is a particular interest in combining RT with anti-VEGF-targeted agents for their independent activity in HCC as well as their radiation sensitization properties. Randomized trials of RT are warranted.

The evolving role of radiation therapy in hepatocellular carcinoma

Technical advancements in imaging, in radiation therapy (RT) planning and RT delivery, have facilitated the safe delivery of conformal radiation therapy to patients with unresectable hepatocellular carcinoma (HCC). Although experience in liver cancer RT is limited, the RT technologies and tools to deliver RT safely are being disseminated rapidly. A variety of doses and RT fractionations have been used to treat HCC, and RT has been used in combination with other therapies including transarterial hepatic chemoembolization (TACE). Outcomes following RT alone or RT and TACE appear better than outcomes following similar historical controls of TACE alone, however, randomized trials of RT are needed. The first site of recurrence following RT is most often within the liver, away from the high dose volume, providing rationale for combining RT with regional or systemic therapies. Given the vascular properties of HCC, the combination of RT with anti-VEGF targeted agents may improve outcomes further.

Simultaneous tumour dose escalation and liver sparing in Stereotactic Body Radiation Therapy (SBRT) for liver tumours due to CTV-to-PTV margin reduction

PURPOSE

To quantify potential benefits of CTV-to-PTV margin reduction for SBRT of liver tumours, as allowed by enhanced treatment precision.

MATERIALS AND METHODS

For 14 patients plans were generated for the clinical margin and for 3 tighter margins. An in-house developed algorithm was used to optimise beam directions, shapes, and weights for generation of the plan with the highest isocenter dose (D(iso)), while keeping the minimum PTV dose at least 65%xD(iso) and strictly adhering to all imposed hard OAR constraints. Each plan contains 10 optimal beam directions, automatically selected from up to 252 coplanar and non-coplanar input directions.

RESULTS

Apart from the expected tumour dose escalation (D(iso), EUD(PTV), gEUD(PTV)) with decreasing margin, a simultaneous improved sparing of the normal liver (D33%, D50%, D(mean)) was also observed. The smaller the margin was, the bigger both effects were. For renormalized plans with D(iso) equal to the clinical value (3x19.2Gy), and a margin reduction of 50% (2.5mm laterally, 5mm longitudinally), normal liver D33% and D50% reduced on average by 22% (maximum 38%), and 26% (maximum 47%), respectively.

CONCLUSIONS

Using an algorithm for beam direction, shape and weight optimisation, large increases in the therapeutic ratio of liver plans could be obtained for reduced margins.