Liver Sparing Research Articles

Devised a New Preoperative Simulation Using (99m)Tc-GSA SPECT Quantitative Method for Liver Resection

We developed a new imaging method to assess liver function by analyzing the amount of liver asialo single photon emission computed tomography (SPECT) using technetium-99m diethylenetriamine pentaacetic acid galactosyl human serum albumin ((99m)Tc-GSA) injection. A preoperative simulation using various regions of interest (ROIs) was performed, and the usefulness of the method for predicting the residual liver function was examined. Ninety-three patients were enrolled who underwent both asialo scintigraphy and dynamic computed tomography (CT) scanning. The two-dimensional dynamic data were analyzed using the Patlak plot method to calculate Kup and perfusion index (PI). The PIi (the quantity of GSA in a reference slice) was calculated using the PI. The qualitative SPECT data were analyzed using the quantitative images and the PIi, and we calculated the amount of asialo uptake per unit, which we named asialo uptake index (AUI). Volume registration was done between the collected breath holding SPECT data and CT images. We were able to obtain AUI images and calculate the liver sparing ability by analyzing the two-dimensional data. The AUI and each of the liver counts (HH15, LHL15, LU15, and PI) were correlated, and we could perform the preoperative simulation using any ROI. Preoperative simulation for the outcome of hepatectomy could be done using our new method employing quantitative SPECT.

Abdominal Compression During Liver Stereotactic Body Radiation Therapy (SBRT) by Volumetric Modulated Arc Therapy (VMAT) Affords Significant Liver Sparing

Abdominal Compression During Liver Stereotactic Body Radiation Therapy (SBRT) by Volumetric Modulated Arc Therapy (VMAT) Affords Significant Liver Sparing

Effects of dry period management and parity on rumen fermentation, blood metabolites, and liver triacylglyceride in dairy cows

Khazanehei, H., Li, S., Khafipour, E. and Plaizier, J. C. 2015. Effects of dry period management and parity on rumen fermentation, blood metabolites, and liver triacylglyceride in dairy cows. Can. J. Anim. Sci. 95: 445–453. The effects of dry period management on rumen fermentation, blood metabolites and liver triacylglyceride (TAG) were determined in 11 second-parity (PAR 2) and 15 third-parity and older (PAR 3+) cows. Cows were paired and randomly assigned to two treatments: (1) a short 40-d dry period (SHORT) with only a close-up diet [1.43 Mcal kg–1 dry matter (DM)], or (2) a conventional 60-d dry period (CONV) with 39 d far-off diet (1.28 Mcal kg–1 DM) and 21 d close-up diet (1.43 Mcal kg–1 DM) in a randomized block design. Concentrations of total volatile fatty acids, ammonia, and lactate in rumen fluid, and also concentrations of lactate, beta hydroxybutyric acid (BHBA), urea and insulin in plasma were not affected by treatment. Across the 3 wk after calving, cows on the SHORT treatment had higher blood non-esterified fatty acid (NEFA) and glucose, and at 1 wk after calving, these cows had a higher liver TAG than cows on the CONV treatment. Also, during this time, PAR 3+ cows had higher serum NEFA compared with PAR 2 cows. Results suggest that the SHORT treatment resulted in more lipolysis, TAG accumulation in the liver and glucose sparing in early lactation compared with the CONV treatment, and that this effect was greater in PAR 3+ cows than in PAR 2 cows.

P0176 Dosimetric comparison of volumetric intensity-modulated arc (RapidArc) therapy, intensity-modulated radiotherapy, and 3D conformal radiotherapy for primary liver tumours

Background To compare the dosimetric outcomes of volumetric arc radiotherapy (RapidArc), intensity-modulated radiotherapy (IMRT), and 3D conformal radiotherapy (3DCRT) plans for primary liver tumours. Methods 7 patients with localised unresectable hepatocellular carcinoma were included in this study. CT simulation was done with voluntary deep inspiratory breath-holding after administering 80–90 mL of intravenous iodinated contrast. The mean tumour size was 5.6 cm (range 2.1–9.8) and two patients had multiple lesions (range 1–3). All patients were planned for partial liver irradiation for a total dose of 50–66 Gy in 2 Gy per fraction with conformal techniques. 3DCRT, IMRT, and RapidArc plans were generated using Eclipse planning system v.13 and dosimetric analysis was done to evaluate the plan quality and efficiency, including CI, HI, MU delivered, PTV D mean and D max . IMRT plans had 3–5 fields and RapidArc plans had 3–5 arcs. V 10 ,V 20 ,V 30 and V 40 of normal liver and D mean of organs at risk (OAR) and D max of spinal cord were also evaluated. Analysis was done using ANOVA and paired t -test with two tailed p Findings All the three techniques had comparable PTV coverage, dose homogeneity, and OAR sparing. IMRT and Rapid Arc had a significantly better conformity index than 3DCRT ( p = 0.03). The high dose areas within the normal liver; V 40 and V 30 were significantly lower in RapidArc and IMRT plans ( p = 0.03 and p = 0.04, respectively), although no significant differences were noted between IMRT and RapidArc. One patient could not attain the normal liver constraint V 33 Interpretation RapidArc and IMRT provide better normal liver sparing and conformity than 3DCRT. However, RapidArc was not better than IMRT for liver protection. Further large trials are required to clearly establish the benefits of IMRT and Rapid Arc techniques to treat primary liver tumours.

Clinical decision tool for optimal delivery of liver stereotactic body radiation therapy: Photons versus protons

PurposeStereotactic body radiation therapy (SBRT) for treatment of liver tumors is often limited by liver dose constraints. Protons offer potential for more liver sparing, but clinical situations in which protons may be superior to photons are not well described. We developed and validated a treatment decision model to determine whether liver tumors of certain sizes and locations are more suited for photon versus proton SBRT. Methods and materialsSix spherical mock tumors from 1 to 6 cm in diameter were contoured on computed tomography images of 1 patient at 4 locations: dome, caudal, left medial, and central. Photon and proton plans were generated to deliver 50 Gy in 5 fractions to each tumor and optimized to deliver equivalent target coverage and maximal liver sparing. Using these plans, we developed a hypothesis-generating model to predict the optimal modality for maximal liver sparing based on tumor size and location. We then validated this model in 10 patients with liver tumors. ResultsProtons spared significantly more liver than photons for dome or central tumors ≥3 cm (dome: 134 ± 21 cm3, P = .03; central: 108 ± 4 cm3, P = .01). Our model correctly predicted the optimal SBRT modality for all 10 patients. For patients with dome or central tumors ≥3 cm, protons significantly increased the volume of liver spared (176 ± 21 cm3, P = .01) and decreased the mean liver dose (8.4 vs 12.2 Gy, P = .01) while offering no significant advantage for tumors <3 cm at any location or for caudal and left medial tumors of any size. ConclusionsWhen feasible, protons should be considered as the radiation modality of choice for dome and central tumors >3 cm to allow maximal liver sparing and potentially reduce radiation toxicity. Protons should also be considered for any tumor >5 cm if photon plans fail to achieve adequate coverage or exceed the mean liver threshold.

Place de la radiothérapie stéréotaxique dans la prise en charge des tumeurs hépatiques

Stereotactic radiotherapy is a high-precision technique based on the administration of high doses to a limited target volume. This treatment constitutes a therapeutic progress in the management of many tumours, especially hepatic ones. If surgery remains the standard local therapy, stereotactic radiotherapy is first dedicated to inoperable patients or unresectable tumours. Patients with moderately altered general status, preserved liver function and tumour lesions limited in number as in size are eligible to this technique. Results in terms of local control are satisfying, regarding primary tumours (notably hepatocellular carcinomas) as metastases stemming from various origins. If treatment protocols and follow-up modalities are not standardized to this day, iconographic acquisition using four-dimensional computed tomography, target volumes delineation based on morphological and/or metabolic data, and image-guided radiotherapy contribute to an oncologic efficacy and an improved sparing of the functional liver. The purpose of this literature review is to report the results of the main works having assessed stereotactic radiotherapy in the management of primary and secondary liver tumours. Technical particularities of this radiation modality will also be described.

Using Volume Index and Lateral Hepatic Angle to Differentiate Biliary Atresia From TPN‐Associated Cholestasis

Differential diagnosis between biliary atresia (BA) and total parenteral nutrition-associated cholestasis (TPN-AC) and early treatment for cholestatic infants are challenges for evaluating neonatal or infantile cholestasis. The aim of our retrospective study was to apply noninvasive indices of magnetic resonance images to differentiate BA from TPN-AC. A total of 44 patients diagnosed as having BA (n = 30) or TPN-AC (n = 14) were included in the present retrospective study and underwent abdominal magnetic resonance imaging to evaluate the possibility of BA. The left lateral hepatic angle was determined from the coronal image of the left portal vein and portal vein of segment II. Adjusted volume indices of the right hepatic lobe (AVIR) and left lateral segment (AVILL) were calculated as the product of 3 diameters (centimeters) divided by each patient's body weight. The left lateral hepatic angles of patients with BA (74° ± 21°) were significantly larger than for patients with TPN-AC (33° ± 9°) and controls (36° ± 5°, P < 0.05). AVILL of the BA (0.037 ± 0.012 cm/g) and TPN-AC groups (0.042 ± 0.030 cm/g) were not significantly different (P = 0.61) but were significantly larger than for controls (0.020 ± 0.011 cm/g) (P < 0.05). The right hepatic lobe to left lateral hepatic segment ratio (RLR) of patients with BA was significantly (P < 0.05) smaller (1.61 ± 0.58) than for patients with TPN-AC (3.08 ± 2.43) and controls (2.98 ± 0.92). Patients with BA could have relative sparing and selective enlargement of the left lateral liver with a resultant lobar difference and blunt left lateral hepatic angle. Noninvasive indices of lobar difference and left lateral hepatic angle help differentiate patients with BA from those with TPN-AC.

TH‐E‐BRF‐01: Exploiting Tumor Shrinkage in Split‐Course Radiotherapy

Purpose:In split‐course radiotherapy, a patient is treated in several stages separated by weeks or months. This regimen has been motivated by radiobiological considerations. However, using modern image‐guidance, it also provides an approach to reduce normal tissue dose by exploiting tumor shrinkage. In this work, we consider the optimal design of split‐course treatments, motivated by the clinical management of large liver tumors for which normal liver dose constraints prohibit the administration of an ablative radiation dose in a single treatment.Methods:We introduce a dynamic tumor model that incorporates three factors: radiation induced cell kill, tumor shrinkage, and tumor cell repopulation. The design of splitcourse radiotherapy is formulated as a mathematical optimization problem in which the total dose to the liver is minimized, subject to delivering the prescribed dose to the tumor. Based on the model, we gain insight into the optimal administration of radiation over time, i.e. the optimal treatment gaps and dose levels.Results:We analyze treatments consisting of two stages in detail. The analysis confirms the intuition that the second stage should be delivered just before the tumor size reaches a minimum and repopulation overcompensates shrinking. Furthermore, it was found that, for a large range of model parameters, approximately one third of the dose should be delivered in the first stage. The projected benefit of split‐course treatments in terms of liver sparing depends on model assumptions. However, the model predicts large liver dose reductions by more than a factor of two for plausible model parameters.Conclusion:The analysis of the tumor model suggests that substantial reduction in normal tissue dose can be achieved by exploiting tumor shrinkage via an optimal design of multi‐stage treatments. This suggests taking a fresh look at split‐course radiotherapy for selected disease sites where substantial tumor regression translates into reduced target volumes.

Development and validation of a treatment decision model for optimal delivery of liver stereotactic body radiation therapy (SBRT): Photons versus protons.

264 Background: Treatment of liver tumors with SBRT provides excellent local control rates, but is often limited by liver dose constraints. Protons offer potential for more liver sparing, but clinical situations where protons may be superior to photons are not well described. We developed and validated a treatment decision model to determine whether patients with liver tumors of certain sizes and locations are more suited for photon vs proton SBRT. Methods: Six spherical mock tumors from 1-6 cm in diameter were contoured on axial CT images of one patient at each of 4 locations (24 total tumors): peripheral/dome, caudal, left medial, central. We generated photon and proton plans (48 plans) to deliver 50 Gy* in 5 fractions with ~135% dose max within the gross tumor volume. Mean liver dose was constrained to &lt; 14 Gy and at least 700 cc received &lt; 15 Gy. Using these plans, we developed a hypothesis-generating model to predict the optimal modality for maximal liver sparing based on tumor size and location. We validated this model in 10 actual liver tumor patients by generating and comparing photon and proton plans. Results: Proton plans spared significantly more liver volume and decreased mean liver dose, particularly for tumors ≥ 3 cm in the dome or central locations− peripheral/dome: 134 ± 21 cc (p = 0.03), 912 cGy vs 1303 cGy (p = 0.01); central: 108 ± 4 cc (p &lt; 0.01), 1179 cGy vs 1454 cGy (p &lt; 0.01). Our model correctly predicted the optimal SBRT modality for all 10 patients. There was a significant increase in the volume of liver spared (176 ± 21 cc, p &lt; 0.01) and decrease in mean liver dose (841 cGy vs 1223 cGy, p &lt; 0.01) with protons for patients with dome or central tumors ≥ 3 cm. As predicted, in patients with tumors &lt; 3 cm at any location or caudal and left medial tumors of any size, there was no significant difference in liver sparing between photon and proton SBRT (33 ± 18 cc, p = 0.13). Conclusions: Tumor size and location are important determining factors in generating deliverable liver SBRT plans. When feasible, protons should be considered as the radiation modality of choice for dome or central tumors ≥ 3 cm to allow maximal liver sparing and potentially reduce radiation toxicity. *All doses are in Gy (RBE).

Comparison of contrast-enhanced ultrasonography with grey-scale ultrasonography and contrast-enhanced computed tomography in diagnosing focal fatty liver infiltrations and focal fatty sparing

Fatty liver infiltrations and fatty sparing impair diagnostic performance of grey-scale ultrasonography in differentiating malignant and benign focal liver lesions. In the study, we present our experience in diagnosing focal fatty liver infiltrations and focal fatty sparing with contrastenhanced ultrasonography (CEUS) in comparison to grey-scale ultrasonography and contrast-enhanced computed tomography (CECT). The retrospective study group (n=82 patients), included 44 (53.7%) men, 38 (46.3%) women (aged 29- 81 years, mean 55.8 years) with 48 focal fatty liver infiltrations and 34 focal fatty sparing. All patients underwent grey-scale ultrasonography (US), CEUS using SonoVue® and CECT executed within the 7 days. With US, CEUS and CECT focal fatty liver infiltrations were diagnosed in 22, 46 and 44 cases, respectively. The following values were obtained: sensitivity - 45.8%, 95.8% and 91.7%, specificity - 100% for all, accuracy - 95.2%, 99.6% and 99.3%, respectively. Focal fatty sparing was diagnosed in 16, 31 and 30 cases, respectively. The following values were obtained: sensitivity - 47.1%, 91.2% and 88.2%, specificity - 99.8%, 100% and 100%, accuracy - 95.6%, 99.4% and 99.3%, respectively. No statistically significant differences were found in sensitivity of diagnosing focal fatty liver infiltrations and focal fatty liver sparing between CEUS and CECT. Sensitivity of grey-scale ultrasonography was significantly lower when compared to those of CEUS and CECT (p<0.001). CEUS is as sensitive as CECT in focal fatty infiltrations and focal fatty sparing diagnosing. However, CEUS provides more information than CECT about the vasculature and enhancement pattern of focal fatty liver infiltrations.

Development of a Decision Tree Analysis Tool for Optimal Delivery of Liver Stereotactic Body Radiation Therapy: Photons Versus Protons

Stereotactic body radiation therapy (SBRT) is playing an increasingly prominent role in the treatment of liver tumors with excellent local control rates, but is often limited due to organs at risk (OAR) constraints. Characteristics of liver tumors that may derive maximal clinical benefit from liver SBRT are not well described. We performed a systematic dosimetric study to determine whether liver tumors of certain sizes and locations are more suited for photon vs proton SBRT. Six spherical tumors ranging from 1 to 6 cm in diameter were contoured on axial CT simulation images of one patient at each of four locations (24 total tumors): Segment 7/8 “Peripheral/Dome”, Segment 6 “Caudal”, Segment 2/3 “Left Medial”, Segment 1 “Central”. We generated and compared photon and proton plans for each of these tumors (48 plans) to deliver 50 Gy in 5 fractions of 10 Gy with a hot spot of ∼135% within the gross tumor volume (GTV). OAR dose constraints included liver minus GTV (mean < 14 Gy, volume receiving < 15 Gy to be ≥ 700 cc), cord, heart, chest wall, bowel, and stomach. Photon SBRT plans were optimized with OAR avoidance using volumetric modulated arc therapy (VMAT). Proton SBRT plans were created with two pencil beam scanning (PBS) fields using single field uniform dose technique. Student t-test was used to compare doses and volumes between photon and protons plans. All 24 proton plans were able to deliver PTV V95% = 100% while meeting all OAR tolerance constraints. Three of 24 photon plans (Left Medial 5 cm and 6 cm, Caudal 6 cm) required minor deviations in PTV coverage in order to meet non-liver OAR dose constraints. For tumors < 3 cm at any location or Caudal and Left Medial tumors of any size, there was no significant difference in normal liver sparing between photon and proton SBRT. For Peripheral/Dome and Central ≥ 3 cm tumors, there was a statistically significant increase in the volume of liver spared and decrease in mean liver dose with protons: Peripheral/Dome: 134 ± 21 cc (p = 0.03), 912 cGy vs 1303 cGy (p = 0.01); Central: 108 ± 4 cc (p = 0.002), 1179 cGy vs 1454 cGy (p = 0.001), respectively. Proton SBRT allowed dose escalation up to 80 Gy (16 Gy per fraction) for Central tumors ≥ 3 cm while meeting all OAR constraints. For all tumors, proton SBRT reduced the mean whole body integral dose by two-fold compared with photons (p < 0.001). Tumor size and location in the liver are important determining factors in generating deliverable liver SBRT plans. Compared with VMAT photon SBRT, PBS proton SBRT allows for lower integral dose as well as significantly increased sparing of normal liver tissue, particularly for tumors ≥ 3 cm in the dome or central locations. Improved liver sparing has the potential to allow for dose escalation in the treatment of large centrally located liver tumors.

Superior liver sparing by combined coplanar/noncoplanar volumetric-modulated arc therapy for hepatocellular carcinoma: A planning and feasibility study

Compared with step-and-shoot intensity-modulated radiotherapy (sIMRT) and tomotherapy, volumetric-modulated arc therapy (VMAT) allows additional arc configurations in treatment planning and noncoplanar (NC) delivery. This study was first to compare VMAT planning with sIMRT planning, and the second to evaluate the toxicity of coplanar (C)/NC-VMAT treatment in patients with hepatocellular carcinoma (HCC). Fifteen patients with HCC (7 with left-lobe and 8 with right-lobe tumors) were planned with C-VMAT, C/NC-VMAT, and sIMRT. The median total dose was 49Gy (range: 40 to 56Gy), whereas the median fractional dose was 3.5Gy (range: 3 to 8Gy). Different doses/fractionations were converted to normalized doses of 2Gy per fraction using an α/β ratio of 2.5. The mean liver dose, volume fraction receiving more than 10Gy (V10), 20Gy (V20), 30Gy (V30), effective volume (Veff), and equivalent uniform dose (EUD) were compared. C/NC-VMAT in 6 patients was evaluated for delivery accuracy and treatment-related toxicity. Compared with sIMRT, both C-VMAT (p = 0.001) and C/NC-VMAT (p = 0.03) had significantly improved target conformity index. Compared with C-VMAT and sIMRT, C/NC-VMAT for treating left-lobe tumors provided significantly better liver sparing as evidenced by differences in mean liver dose (p = 0.03 and p = 0.007), V10 (p = 0.003 and p = 0.009), V20 (p = 0.006 and p = 0.01), V30 (p = 0.02 and p = 0.002), Veff (p = 0.006 and p = 0.001), and EUD (p = 0.04 and p = 0.003), respectively. For right-lobe tumors, there was no difference in liver sparing between C/NC-VMAT, C-VMAT, and sIMRT. In all patients, dose to more than 95% of target points met the 3%/3mm criteria. All 6 patients tolerated C/NC-VMAT and none of them had treatment-related ≥ grade 2 toxicity. The C/NC-VMAT can be used clinically for HCC and provides significantly better liver sparing in patients with left-lobe tumors.

Dosimetry Analysis of Three Kinds of Radiation Technique for Postoperative Gastric Cancer

Objective: To compare dose-volume histograms (DVHs) and the dose distribution of three-dimensional conformal radiotherapy(3DCRT),7 fields radiotherapy(7FRT) and intensity-modulated radiotherapy (IMRT) of treatment planning in gastric cancer. Methods: We selected 5 patients with gastric cancer, they were pathologically confirmed stage T3,T4 or N+ gastric cancer. All patients underwent radical gastrectomy. A dosimetry study was carried out on these five patients. For each patient, three kinds of treatment planning were designed with a prescribed dose of 45Gy to 95％of PTV.Many kinds of parameters of these plans in each patient were compared: isodose distributions line、dose-volume histogram(DVH)、V95%、V110%、CI、HI、EI of target volume and the dose of related critical organs. Results: IMRT was superior to 3DCRT and 7F-RT in dose uniformity（p＜0.05）, there was no statistical difference between 3DCRT and 7FRT in CI（p&gt;0.05）.IMRT had better dose conformity than 3DCRT and 7FRT（p＜0.05）, and 3DCRT was better than 7FRT in CI（p＜0.05）.IMRT showed better EI than 3DCRT and 7FRT（p＜0.05）,there was no statistical difference between 3DCRT and 7FRT in EI（p&gt;0.05）.IMRT had advantage at sparing liver compared with 3DCRT and 7FRT（p＜0.05）,7FRT showed better D1/3 of liver than 3DCRT（p＜0.05）,but there was no statistical difference between 3DCRT and 7FRT in Dmean of liver（p&gt;0.05）.IMRT expressed better Dmax of spinal cord than 3DCRT and 7F-RT（p＜0.05）, and 7FRT was better than IMRT in Dmax of spinal cord（p＜0.05）.But the dose received by the both kidneys were not significantly different. Conclusion: IMRT is superior to 3DCRT and 7FRT,and 3DCRT plans showed better CI and Dmax of spinal cord composed to 7FRT,and 7FRT was superior to 3DCRT in D1/3 of liver. IMRT for gastric cancer had physics advantage for clinical application.

Multiple focal nodular hyperplasias induced by oxaliplatin-based chemotherapy

Focal nodular hyperplasia (FNH) is a benign condition that affects normal liver with low prevalence. Recently, the extensive use of oxaliplatin to treat patients with colorectal cancer has been reported to be associated with the development of different liver injuries, as well as focal liver lesions. The present work describes two patients with multiple bilateral focal liver lesions misdiagnosed as colorectal liver metastases, and treated with liver resection. The first patient had up to 15 small bilateral focal liver lesions, with magnetic resonance imaging consistent with colorectal liver metastases (CLM), and fluorodeoxyglucose (FDG)-positron emission tomography (PET) negative. The second patient had up to 5 small focal liver lesions, with computed tomography consistent with CLM, and FDG-PET negative. They had parenchyma sparing liver surgery, with uneventful postoperative course. At the histology the diagnosis was multiple FNHs. The risks of oxaliplatin-based chemotherapy regimens in development of liver injuries, such as FNH, should not be further denied. The value of the modern multidisciplinary management of patients with colorectal cancer relies also on the precise estimation of the risk/benefit for each patient.

Multimodal management of colorectal liver metastases and the effect on regeneration and outcome after liver resection

Management of colorectal liver metastases (CRLM) has dramatically changed during the last decade and has now become more multimodal and aggressive, including the use of downstaging chemotherapy, portal vein embolization to increase the function of the liver remnant or both in combination. Radiofrequency ablation is also an option in CRLM, potentially combined with surgical resection. Results are quite convincing concerning the safety of liver resection also when performed following neoadjuvant chemotherapy. Sparing liver parenchyma in patients with bilobar liver metastatic disease subjected to liver resection may be possible without endangering surgical radicality. Sparing liver parenchyma when using neoadjuvant chemotherapy, a chemotherapy-free period of 6 weeks or more seems to positively affect liver regeneration. There is still the possibility to reresect recurrent liver lesions, though there seems to be a tendency toward fewer reresections following the use of adjuvant chemotherapy.

P3-082 - Volumetric Intensity-Modulated arc Therapy for Primary Hepatocellular Carcinoma: Comparison with 3D Conformal Radiotherapy

ABSTRACT Background To compare the volumetric intensity modulated arc (VMAT) plan for primary hepatocellular carcinoma (HCC) with 3-dimensional conformal radiation (3DCRT) with the using dosimetric analysis. Methods Nine patients of HCC were enrolled in this study. Total 10 lesions (one patient had bilateral lesions) measuring 1 ∼ 3 cm (median 2 cm) were analyzed. Dosimetric values for VMAT using two arcs and 3DCRT were calculated for total doses of 50 Gy using 2.5 Gy/day. The parameters included the quality of coverage (QOC), conformal index (CI), homogeneity index (HI) and hot spot (V105%) for the planning target volume (PTV) as well as the monitor units (MUs) for plan efficiency, the mean dose (Dmean) for the organs at risk (OAR) and the maximal dose at 1% volume (D1%) for the spinal cord. The percentage of the liver volume receiving ≥40, >30, >20, and >10 Gy (V40 Gy, V30 Gy, V20 Gy, and V10 Gy) were also evaluated to determine liver toxicity. Results VMAT achieved significantly better CI values (1.02 ± 0.07) than 3DCRT (1.54 ± 0.38) (P Conclusions In patients with primary hepatocellular carcinoma, VMAT plan showed more conformal tumor coverage and an improvement in liver sparing compared with 3DCRT, whereas 3DCRT provided more homogeneous tumor coverage compared with VMAT.

Dominant Advantage in Liver Sparing by Integrating Non-Coplanar Volumetric Modulated Arc Therapy for Left-Lobe Intrahepatic Malignancies

Dominant Advantage in Liver Sparing by Integrating Non-Coplanar Volumetric Modulated Arc Therapy for Left-Lobe Intrahepatic Malignancies

Normal liver tissue sparing by intensity-modulated proton stereotactic body radiotherapy for solitary liver tumours

Background. Stereotactic body radiotherapy (SBRT) is often the preferred treatment for the advanced liver tumours which owing to tumour distribution, size and multi-focality are out of range of surgical resection or radiofrequency ablation. However, only a minority of patients with liver tumours may be candidates for conventional SBRT because of the limited radiation tolerance of normal liver, intestine and other normal tissues. Due to the favourable depth-dose characteristics of protons, intensity-modulated proton therapy (IMPT) may be a superior alternative to photon-based SBRT. The purpose of this treatment planning study was therefore to investigate the potential sparing of normal liver by IMPT compared to photon-based intensity-modulated radiotherapy (IMRT) for solitary liver tumours. Material and methods. Ten patients with solitary liver metastasis treated at our institution with multi-field SBRT were retrospectively re-planned with IMRT and proton pencil beam scanning techniques. For the proton plans, two to three coplanar fields were used in contrast to five to six coplanar and non-coplanar photon fields. The same planning objectives were used for both techniques. A risk adapted dose prescription to the PTV surface of 12.5–16.75 Gy × 3 was used. Results. The spared liver volume for IMPT was higher compared to IMRT in all 10 patients. At the highest prescription dose level, the median liver volume receiving less than 15 Gy was 1411 cm3 for IMPT and 955 cm3 for IMRT (p < 0.005); also the mean liver dose was lower with IMPT compared to IMRT (median 9.1 Gy vs. 20.0 Gy; p < 0.005). All IMPT and IMRT plans met the VD < 15 Gy > 700 cm3 constraint. For the Dmean ≤ 15 Gy constraint, nine of 10 cases could be treated at the highest dose level using IMPT whereas with IMRT, only two cases met this constraint at the highest dose level and six at the lowest dose level. Conclusion. A considerable sparing of normal liver tissue can be obtained using proton-based SBRT for solitary liver tumours.

SU‐E‐E‐03: Advantageous Liver Sparing by Non‐Coplanar Volumetric Modulated Arc Therapy to Intrahepatic Malignancy: A Dosimetric and Feasibility Study

Purpose: Volumetric modulated arc therapy (VMAT) has been an evolving technique with improved conformity, normal organ sparing, and the additional freedom of non‐coplanar beam design as compared to helical tomotherapy. This study was to compare the dose‐volume liver sparing effect between coplanar (C) with and without non‐coplanar (NC) design for volumetric modulated arc therapy (VMAT), and to verify the delivery accuracy in patients with liver malignancy treated by the integrated NC‐VMAT. Methods: Sixteen patients with intrahepatic malignancies were planned with VMAT using coplanar with and without the additional non‐coplanar beams. All the prescribed doses were normalized to the fraction size of 2 Gy. The dose‐volume data of liver were calculated by the total liver minus the gross tumor volume. The mean dose, volume fraction receiving more than certain dose x Gy (Vx), and effective volume of liver (Veff) were compared with paired Student t test. Seven patients treated by the integrated NC‐VMAT were verified for dose accuracy using 2‐dimensional array method (MapCheck2). Results: With comparable target coverage, NC‐VMAT provided significantly better liver sparing effect than C‐VMAT in mean dose (16.52±7.8 Gy vs. 17.9±8.9 Gy, p=0.02), V5 (50.3±15.2% vs. 53.8±16.6%, p=0.02), V10 (33.1±10.8% vs. 35.3±13.1%, p=0.08), V20 (24.6±10.3% vs. 26.6±12.2%, p=0.04), V30 (20.1±10.3% vs. 22.0±11.9%, p=0.02), and Veff (9.6±5.2% vs. 10.6±5.9%., p=0.03), respectively. Among the 7 patients treated by NC‐VMAT with the average delivery time of 368±105 seconds, All but one patient with the dose accuracy met the 3%/3mm criteria of more than 95%, and all patients completed the treatment with no more than grade 2 liver toxicity. Conclusions: Liver is a sensitive organ to even low‐dose irradiation, is located asymmetrically in the abdomen, and has irregular shape. NC‐VMAT may be advantageous in liver sparing and feasible for the accurate delivery.

Abstract No. 203: Dose-escalating study of Yttrium-90 microspheres with capecitabine for intrahepatic cholangiocarcinoma or metastatic disease to the liver: Preliminary results

Abstract No. 203: Dose-escalating study of Yttrium-90 microspheres with capecitabine for intrahepatic cholangiocarcinoma or metastatic disease to the liver: Preliminary results