Planning Target Volume Research Articles

Exploring the impact of field shape on predicted dose distribution in breast cancer patients using deep learning in radiation therapy

BackgroundGeometrical information such as field shape is essential for dose calculation in radiation therapy. However, new methods of dose prediction based on deep learning only use CT images and contouring of patients. The aim of this study is to develop a deep learning method for three-dimensional dose prediction for breast cancer radiotherapy using field shape as well as CT and contouring images of patients. MethodsA total of 150 breast cancer patients' data treated with 3D conformal radiation therapy (CRT) technique were used to train and test 3D-U-Res-F-Net model. The model inputs were CT images, patients' contouring and field shape. The network output was the corresponding the patients’ dose distribution. Then, the dosimetric parameters extracted from the dose volume histograms related to the planned and predicted dose distributions were compared and were statistically analysed with the paired-samples t-test. These parameters include Dmean and Dmax for planning target volume and organs at risk, D95%, D50%, V47.5Gy for PTV, V30Gy and V25Gy for heart and V20Gy for left lung. The gamma index with 3%/3 mm criteria was calculated for PTV and OARs. ResultsThe average absolute difference of the Dmean relative to the prescribed dose for the PTV, heart, left lung, right lung and spinal cord were 1.37 ± 0.4%, 2.02 ± 2%, 2.12 ± 1%, 0.37 ± 0.3% and 0.41 ± 0.3%, respectively. The average absolute difference of the Dmax relative to the prescribed dose for the PTV and OARs varied from 0.23 ± 0.2% to 2.04 ± 2%. The 3D gamma pass rate with 3mm/3% criteria for planning target volume, heart, left lung, right lung, spinal cord and body were 89 ± 3%, 91 ± 5%, 93 ± 5%, 99 ± 3%, 99 ± 1% and 96 ± 2% respectively. ConclusionsThe results of the proposed model demonstrate that there is no significant difference between the predicted and planned dose distributions. The deep learning model can directly predict the 3D dose distribution faster than treatment planning systems. Further studies with more patients and on other cancer sites are essential to fully validate the proposed method.

Analysis of Wedge Angle Variations in the Treatment Planning System Based on Dose Volume Histogram on Ca Mammae Sinistra

Breast cancer ranks first in terms of the highest number of cancers in Indonesia and is one of the first contributors to cancer deaths. According to IARC, radiotherapy is one of the most important modalities in the treatment of breast cancer. Radiotherapy is a type of treatment that uses ionizing radiation to kill cancer cells without damaging surrounding healthy tissue. To obtain an even or homogeneous dose distribution on an uneven skin surface, a wedge is used so that the radiation given to the tumor area is truly optimal and the surrounding healthy tissue receives a minimum dose. This research was carried out by evaluating the Planning Target Volume (PTV) value based on ICRU-83 and dose distribution in Organs at Risk (OAR) based on QUANTEC standards at four different wedge angles, namely 15°, 30°, 45°, and 60°, used the 3D-CRT technique of tangential radiation with a dose of 50 Gy in 25 fractions on 5 left-sided breast cancer patients. The research results showed that the average Homogeneity Index (HI) values for the 15°, 30°, 45° and 60° wedges were 0.286, 0.346, 0.436 and 0.578, respectively. In the left and right lung dose distribution, the results obtained for the 15°, 30°, 45°, and 60° wedge were respectively 2231.4 and 116.2 cGy, 2257.8 and 114.6 cGy, 2141 and 100 cGy, and 2059.4 and 88.8 cGy. For the average dose distribution to the heart, the values obtained at the 15°, 30°, 45°, and 60° wedges were 2005.6 cGy, 2040.4 cGy, 1930.6 cGy, and 1844.4 cGy, respectively. where the average dose received by OAR is still below the limit allowed by QUANTEC. Using a wedge angle of 15° provides a homogeneous dose distribution for the PTV and a wedge angle of 60° provides the lowest dose distribution for the OAR.

A patient-specific auto-planning method for MRI-guided adaptive radiotherapy in prostate cancer

Background and purposeFast and automated generation of treatment plans is desirable for magnetic resonance imaging (MRI)-guided adaptive radiotherapy (MRIgART). This study proposed a novel patient-specific auto-planning method and validated its feasibility in improving the existing online planning workflow. Materials and methodsData from 40 patients with prostate cancer were collected retrospectively. A patient-specific auto-planning method was proposed to generate adaptive treatment plans. First, a population dose-prediction model (M0) was trained using data from previous patients. Second, a patient-specific model (Mps) was created for each new patient by fine-tuning M0 with the patient’s data. Finally, an auto plan was optimized using the parameters derived from the predicted dose distribution by Mps. The auto plans were compared with manual plans in terms of plan quality, efficiency, dosimetric verification, and clinical evaluation. ResultsThe auto plans improved target coverage, reduced irradiation to the rectum, and provided comparable protection to other organs-at-risk. Target coverage for the planning target volume (+0.61 %, P = 0.023) and clinical target volume 4000 (+1.60 %, P < 0.001) increased. V2900cGy (−1.06 %, P = 0.004) and V1810cGy (−2.49 %, P < 0.001) to the rectal wall and V1810cGy (−2.82 %, P = 0.012) to the rectum were significantly reduced. The auto plans required less planning time (−3.92 min, P = 0.001), monitor units (−46.48, P = 0.003), and delivery time (−0.26 min, P = 0.004), and their gamma pass rates (3 %/2 mm) were higher (+0.47 %, P = 0.014). ConclusionThe proposed patient-specific auto-planning method demonstrated a robust level of automation and was able to generate high-quality treatment plans in less time for MRIgART in prostate cancer.

Effects of electron density force to 1.0 and fill to 1.0 on VMAT treatment plans for lung SBRT.

The aim of this study is to determine the effect of forcing and filling the electron density (ED) to 1.0 of the planning target volume (PTV) overdose distribution in lung SBRT treatment leading to shortening patient treatment time and increasing patient comfort by reducing MU/fraction due to ED manipulation effect. In this study, 36 lung SBRT plans of 12 suitable patients who prescribed a total dose of 50Gy in five fractions were generated with Monaco v.5.10 TPS using the Monte Carlo (MC) algorithm and volumetric modulated arc therapy (VMAT) technique by PTV ED values forcing as well as filling to 1.0 and comparatively assessed. The first group of plans was created by using the patient's original ED, second and third groups of plans were reoptimized by forcing and filling the ED of PTV to 1.0, respectively, therefore acquiring a new dose distribution which lead to comparatively assessment the effects of changes in ED on PTV and OAR doses. Assessment of treatment plans revealed that mean MU/fx numbers were decreased by 76% and 75.25% between Groups 1 and 2, Groups 1 and 3, respectively. The number of segments was also reduced in Group 1 by up to 15% compared with Groups 2 and 3. Maximum HI and CI differences for PTV between Groups 1 and 2 were less than 1% and Groups 1 and 3 were 1.5% which indicates all 3 group plans were comparable in terms of dose distribution within PTV. Forcing and filling the ED of PTV to 1.0 strategy has provided reduced a number of segments and MU/fx without a significant change in PTV mean and maximum doses, thereby decreasing treatment time and patient discomfort during treatment. This process should be considered in line of a potential number of patients as well as prescribed dose and MU/fx numbers.

Analisis Distribusi Dosis pada Treatment Planning System Pasien Kanker Payudara dengan Sumber Foton 6 MV pada Instalasi Radioterapi Rumah Sakit X

The internship at X Hospital aimed to gain practical experience as a medical physicist over two months, particularly in the treatment planning system activities in the radiotherapy unit. Additionally, this internship aimed to evaluate the Dose Volume Histogram (DVH) and analyze the effectiveness of the isodose lines. The treatment planning system is a simulation of cancer or tumor treatment using radiation with 3D conformal radiotherapy (3D-CRT) techniques. The patient study object was a woman with post-mastectomy breast cancer who was to undergo adjuvant curative therapy. The prescribed dose was 50 Gy, divided into 25 fractions, using a 6 MV photon source. The irradiation was conducted with four fields, gantry angle 129° with collimator angle 270°, 310° with collimator angle 90°, 130° with collimator angle 0°, and 270° with collimator angle 0°, field size 14 x 14 cm, and irradiation distance of 100 cm. The TPS simulation results indicated that the dose received by the Planning Target Volume (PTV) covered more than 90% of the target volume (special treatment), while the dose received by the Organ at Risk (OAR) tended to be below the threshold limit, and the isodose lines ensured optimal radiation dose distribution to the breast cancer target area. This was demonstrated by the DVH curve.

A lung SBRT treatment planning technique to focus high dose on gross disease

This study investigated a straightforward treatment planning technique for definitive stereotactic body radiation therapy (SBRT) for patients with early-stage lung cancer aimed at increasing dose to gross disease by strategically penalizing the normal tissue objective (NTO) in the EclipseTM treatment planning system. Twenty-five SBRT cases were replanned to 50 Gy in 5 fractions using static and dynamic NTO methods (50 plans total). The NTO had a start dose of 100% at the target border, end dose of 20%, fall-off rate of 0.4/mm, and a priority of 150. For the static NTO plans, a lower planning target volume (PTV) objective was placed at 52 Gy with a priority of 100. Maximum dose was not penalized. Optimization was performed without user interaction. In contrast, the planner incrementally increased the priority of the NTO on the dynamic NTO plans until 95% of the target volume was covered by the prescription dose. Further, the dynamic NTO plans used both PTV lower and upper objectives at 63-64 Gy with priorities of 50. Maximum dose was penalized to ensure that the hot spot was within ± 2% of the static NTO global maximum dose. Following optimization, all plans were normalized so that the prescription dose covered 95% of the PTV. Plans were scored based on RTOG 0813 criteria, and dose to the internal target volume (ITV) and PTV was evaluated. The Wilcoxon signed-rank test (threshold = 0.05) was used to evaluate differences between the static and dynamic NTO plans. All plans met RTOG 0813 planning guidelines. In comparison to the static NTO plans, the dynamic NTO plans exhibited statistically significant increases in PTV mean dose, ITV mean dose, and PTV-ITV mean dose. Notably, the dynamic NTO plans more effectively concentrated the high dose on gross disease at the center of the PTV. As compared to the static NTO plans, the mean dose was 4.6 Gy higher in the ITV while only 1.3 Gy higher in the PTV-ITV rind of the dynamic NTO plans. Global maximum doses were similar. There were some small yet statistically significant differences in dose conformity between plan types. Furthermore, the dynamic NTO plans demonstrated a significant reduction in total monitor units (MU). This study demonstrated an efficient optimization strategy for lung SBRT plans that concentrates the highest dose in the gross disease, which may improve local control.

Treatment Time and Dosimetric Advantage in Cone Beam Computed Tomography-Guided Online Adaptive Radiation Therapy Considering Interfractional and Intrafractional Changes in Patients With Gastric Mucosa-Associated Lymphoid Tissue Lymphoma

Radiation therapy is the standard treatment for localized gastric mucosa-associated lymphoid tissue (MALT) lymphoma. The ETHOS system (Varian Medical System) has enabled us to perform cone beam computed tomography (CBCT)-guided online adaptive radiation therapy (oART). This study presents a retrospective dosimetric analysis for interfractional and intrafractional change and treatment time in oART for gastric MALT lymphoma. We included 3 male patients with gastric MALT lymphoma who underwent exhalation breath-hold fasting oART using the SpiroDynr'X system. Treatment details and plans (3 reference [REF] plans, 51 scheduled [SCH] plans, and adapted [ADP] plans) were retrospectively analyzed. Doses to the clinical target volume in planning CT (CTV_REF), CTV1, and CTV2 (representing the stomach in planning and preirradiation CBCT, respectively) and planning target volume (PTV) in the planning CBCT were estimated. D2%, D98%, D50%, and Dmean for these volumes, along with organ-at-risk doses, were examined across the 3 plans. The PTV dose coverage of CTV2 on preirradiation CBCT was calculated. CBCT-guided oART was completed within the scheduled period, using the ADP plans instead of the SCH plans on each treatment day in all cases. The average treatment time was approximately 45 minutes. CTV1 and CTV2 exhibited intrafractional and interfractional variations, fluctuating above and below CTV_REF. Some ADP plans resulted in incomplete PTV coverage of CTV2, but the unincluded volume was <1% of CTV2. D50%, D98%, and Dmean of CTV1, CTV2, and PTV were significantly improved in the ADP plans than in the SCH plans. Moreover, the Dmean to the liver and kidneys was reduced in the ADP plans. CBCT-guided oART in patients with gastric MALT lymphoma demonstrated that ADP plans improved CTV1, CTV2, and PTV doses and reduced the mean bilateral kidney and liver doses, suggesting that it may offer enhanced treatment precision for gastric MALT lymphoma.

Lung SBRT: Dose gradient optimization based on target size

This study investigated optimization settings that steepen the dose gradient as a function of target size for lung stereotactic body radiation therapy (SBRT). Sixty-eight lung SBRT patients with planning target volumes (PTVs) ranging from 2-203 cc were categorized into small (<20 cc), medium (20-50 cc), and large (>50 cc) groups. VMAT plans were generated using the normal tissue objective (NTO) to penalize the dose gradient at progressively steeper NTO fall-off values (0.1, 0.2, 0.3, 0.4, 0.5 mm-1). Dose was calculated using the AcurosXB algorithm and was normalized so the prescription dose covered 95% of the PTV. Mann-Whitney, Kruskal-Wallis and ANOVA tests were used to assess for statistical differences in the Conformity Index at the 50% isodose level (CI50%), global maximum dose (Dmax), and monitor units (MU) across the various NTO settings. All plans adhered to institutional criteria and met the guidelines of the Radiation Therapy Oncology Group 0813. Steeper NTO fall-off values significantly increased Dmax and MUs across all groups (p < 0.05). CI50% significantly differed with fall-off values in small (0.3 mm-1) and medium (0.2 mm-1) targets, indicating steeper NTO fall-off values improve CI50% for small and medium targets (p < 0.05). Large targets showed no significant CI50% difference across these fall-off values. As target size increases, the importance of fall-off values in achieving an acceptable CI50% diminishes. Smaller targets benefit from steeper fall-off values despite increased Dmax and MUs. Consideration of fall-off value relative to target size is crucial to limit dose spillage outside the target.

Evaluation and Comparison of the Dose Received by the Mandible, Maxilla, and Teeth in Two Methods of Three-dimensional Conformal Radiation Therapy and Helical Tomotherapy.

Using three-dimensional conformal radiation treatment (3D-CRT) and helical tomotherapy (HT), this study examines and contrasts the dosage received by the mandible, maxilla, and teeth. Sixteen patients with head-and-neck cancer (H and NC) were the subject of treatment planning at the Seyyed Al-Shohada Hospital in Isfahan, Iran. This study examined target coverage quality, exposure of healthy tissue, and radiation delivery effectiveness. In terms of a number of measures, including D2%, D50%, Dmean, V95%, conformity index (CI), and homogeneity index (HI) for the planning target volume (PTV) and D2%, D98%, Dmean, V95%, CI, and HI for the nodal PTV, HT showed considerable gains over 3D-CRT. The brainstem, D1cc, and D10cc received considerably lower maximum dosages in HT. Measurements of the right and left cochleas (Dmean, V55, and Dmax) revealed decreases in HT, with Dmean revealing the most significant variations. The Dmean and Dmax values for HT significantly decreased in constrictors as well. In terms of several HT-related indicators, the larynx, optic chiasm, optic nerves, oral cavity, mandible, thyroid, and parotid glands all showed considerable decreases. The findings of the comparison of the two treatment approaches revealed that the HT method was more than 50% more effective than the 3D-CRT method in sustaining organs at risk (OARs) and the target volume dose. In general, dosimetric coverage, homogeneity, conformity indices, and the absence of cold and hot patches showed that HT produced targets with greater accuracy than 3D-CRT. In addition, HT outperformed 3D-CRT in protecting important structures (OARs). HT as a result has the potential to be a more effective method of treatment for those with H and NC and involvement of regional lymph nodes.

Planning Benchmark Study for Stereotactic Body Radiation Therapy of Pancreas Carcinomas With Simultaneously Integrated Boost and Protection: Results of the DEGRO/DGMP Working Group on Stereotactic Radiation Therapy and Radiosurgery

The proximity or overlap of planning target volume (PTV) and organs-at-risk (OARs) poses a major challenge in stereotactic body radiation therapy (SBRT) of pancreatic cancer (PACA). This international treatment planning benchmark study investigates whether simultaneous integrated boost (SIB) and simultaneous integrated protection (SIP) concepts in PACA SBRT can lead to improved and harmonized plan quality. A multiparametric specification of desired target doses (gross target volume [GTV]D50%, GTVD99%, PTVD95%, and PTV0.5cc) with 2 prescription doses of GTVD50% = 5 × 9.2Gy (46 Gy) and GTVD50% = 8 × 8.25 Gy (66 Gy) and OAR limits were distributed with planning computed tomography and contours from 3 PACA patients. In phase 1, plans were ranked using a scoring system for comparison of trade-offs between GTV/PTV and OAR. In phase 2, replanning was performed for the most challenging case and prescription with dedicated SIB and SIP contours provided for optimization after group discussion. For all 3 cases and both phases combined, 292 plans were generated from 42 institutions in 5 countries using commonly available treatment planning systems. The GTVD50% prescription was performed by only 76% and 74% of planners within 2% for 5 and 8 fractions, respectively. The GTVD99% goal was mostly reached, while the balance between OAR and target dose showed initial SIB/SIP-like optimization strategies in about 50% of plans. For plan ranking, 149 and 217 score penalties were given for 5 and 8 fractions, pointing to improvement possibilities. For phase 2, the GTVD50% prescription was performed by 95% of planners within 2%, and GTVD99% as well as OAR doses were better harmonized with notable less score penalties. Fourteen of 19 planners improved their plan rank, 9 of them by at least 2 ranks. Dedicated SIB/SIP concepts in combination with multiparametric prescriptions and constraints can lead to overall harmonized and high treatment plan quality for PACA SBRT. Standardized SIB/SIP treatment planning in multicenter clinical trials appears feasible after group consensus and training.

Effect of primary tumor volume on survival of concurrent chemoradiotherapy in stage IV non-small cell lung cancer.

To explore the survival effect of thoracic gross tumor volume (GTV) in three-dimensional (3D) radiotherapy for stage IV non-small cell lung cancer (NSCLC). The data cases were obtained from a single-center retrospective analysis. From May. From 2008 to August 2018, 377 treatment criteria were enrolled. GTV was defined as the volume of the primary lesion and the hilus as well as the mediastinal metastatic lymph node. Chemotherapy was a platinum-based combined regimen of two drugs. The number of median chemotherapy cycles was 4 (2-6), and the cut-off value of the planning target volume (PTV) dose of the primary tumor was 63 Gy (30-76.5 Gy). The cut-off value of GTV volume was 150 cm3 (5.83-3535.20 cm3). The survival rate of patients with GTV <150 cm3 is better than patients with GTV ≥150 cm3. Multivariate Cox regression analyses suggested that peripheral lung cancer, radiation dose ≥63 Gy, GTV <150 cm3, 4-6 cycles of chemotherapy, and CR + PR are good prognostic factors for patients with stage IV non-small cell lung cancer. The survival rate of patients with GTV <150 cm3 was longer than patients with ≥150 cm3 when they underwent 2 to 3 cycles of chemotherapy concurrent 3D radiotherapy (p < 0.05). When performing 4 to 6 cycles of chemotherapy concurrent 3D radiotherapy, there was no significant difference between <150 cm3 and ≥150 cm3. The volume of stage IV NSCLC primary tumor can affect the survival of patients. Appropriate treatment methods can be opted by considering the volume of tumors to extend patients' lifetime to the utmost.

Automated plan generation for prostate radiotherapy patients using deep learning and scripted optimization

Background and PurposeTreatment planning is a time-intensive task that could be automated. We aimed to develop a “single-click” workflow, fully deployed within a commercial treatment planning system (TPS), for autoplanning prostate radiotherapy treatment plans using predictions from a deep learning model (DLM). Materials and MethodsAutomatically generated treatment plans were created with a single script, executed from within a commercial TPS scripting environment, that performed two stages sequentially. Initially, a 3D dose distribution was predicted with a ResUNet DLM. The DLM was trained and validated using previously treated datasets (n = 120) which used 3D contours as inputs. Following this, dose predictions were converted into treatment plans by extracting dose-volume metrics from the predictions to use as objectives for the inverse optimizer within the TPS. An independent test dataset (n = 20) was used to evaluate the similarity between automated and clinical plans. ResultsFor planning target volumes, the median percentage difference and interquartile range between the automatically generated plans and clinical plans were 0.4% [0.2-1.1%] for the V100%, −0.5% [(−1.0)-(−0.2)%] for D99% and −0.5% [(−1.0)-(−0.2)%] for D95%. Bladder and rectum volume-at-dose objectives agreed within −6.1% [(−12.5)-0.9%]. The conversion of the DLM prediction into a treatment plan took 15 min [13-16 min]. ConclusionsAn automatic plan generation workflow that uses a DL model with scripted optimization was fully deployed in a commercial TPS. Autoplans were compared to previously treated clinical plans and were found to be non-inferior.

COMPARATIVE RADIATION DOSIMETRY OF WHOLE BREAST RADIOTHERAPY USING IMRT AND VMAT TECHNIQUES IN LEFT SIDED BREAST CANCER PATIENTS AFTER BREAST CONSERVING SURGERY

Background:The radiotherapy of left sided breast cancers is mandatory and integral part of treatment and challenging because of surrounding critical structures posing increased risk of complications. The main objective of this study was to quantify doses toorgan at risk(OARs) including left lung, heart, contralateral breast, spinal cord, and planning target volume (PTV) using different radiation techniques like Intensity modulated radiation therapy (IMRT)&amp;volumetric modulated arc therapy (VMAT) and comparison of radiation dosimetry. Methods: A prospective study of 30 patients of left sided breast cancer who had undergone Breast Conservative Surgery (BCS) and chemotherapy was done for adjuvant radiation. For every patient radiation planning was done by two different techniques IMRT and VMAT. Then the comparison of radiation dosimetry parameters was done for all the techniques including the parameters like PTV coverage, doses to OAR like heart, left lung, contralateral breast and spinal cord and head of humerus. The Homogenity Index (HI) were calculated. Result: The Mean age of the patient was 46.7 years. When comparing the doses delivered in IMRT and VMAT Technique for left sided breast cancer post breast conservation surgery there was significant difference in PTV Breast and axilla V95 Gy. It was 96.2±1.9% (IMRT) vs 94.8±1.71% (VMAT), (p=0.004). However significant sparing of Organs at Risk was seen. With ipsilateral lung dose mean V5 Gy was 77.86± 9.68% (IMRT) v/s 83.04± 9.86 % (VMAT), (p=0.0446). Also mean V30 Gy was 14.6±4.82% with IMRT vs 16.54±5.86% with VMAT, (p=0.0169). Heart mean dose was 8.8±1.49 Gy with IMRT and 10.98±3.7 Gy with VMAT, (p=0.0227). Further V30 Gy for Heart was 4.61±3.8% with IMRT and 6.72±4.0% with VMAT, (p=0.0132).No significant difference was seen with IMRT and VMAT technique for contralateral lung, contralateral breast and spinal cord. Conclusion: In treatment of patients with radiation with left breast cancer patients post BCS using IMRT and VMAT technique it is seen significant dose reduction with IMRT Technique for ipsilateral lung and Heart as compared to VMAT technique. Significant V95 coverage for PTV Breast and axilla with IMRT as compared to VMAT. Hence in our Study IMRT technique was found to be superior for better sparing of Organ at risk and better PTV coverage.

Efficacy and prognostic factors of stereotactic body radiotherapy combined with immunotherapy for pulmonary oligometastases: a preliminary retrospective cohort study.

Stereotactic body radiotherapy (SBRT) combined immunotherapy has a synergistic effect on patients with stage IV tumors. However, the efficacy and prognostic factors analysis of SBRT combined immunotherapy for patients with pulmonary oligometastases have rarely been reported in the studies. The purpose of this study is to explore the efficacy and prognostic factors analysis of SBRT combined immunotherapy for patients with oligometastatic lung tumors. A retrospective analysis was conducted on 43 patients with advanced tumors who received SBRT combined with immunotherapy for pulmonary oligometastases from October 2018 to October 2021. Local control (LC), progression-free survival (PFS), and overall survival (OS) were assessed using the Kaplan-Meier method. Univariate and multivariate analyses of OS were performed using the Cox regression model, and the P value <0.05 was considered statistically significant. The receiver operating characteristic (ROC) curve of neutrophil-to-lymphocyte ratio (NLR) after SBRT was generated. Spearman correlation analysis was used to determine the relationship of planning target volume (PTV) with absolute lymphocyte count (ALC) before and after SBRT and with neutrophil count (NE) after SBRT. Additionally, linear regression was used to examine the relationship between ALC after SBRT and clinical factors. A total of 43 patients with pulmonary oligometastases receiving SBRT combined with immunotherapy were included in the study. The change in NLR after SBRT was statistically significant (P<0.001). At 1 and 2 years, respectively, the LC rates were 90.3% and 87.5%, the OS rates were 83.46% and 60.99%, and the PFS rates were 69.92% and 54.25%, with a median PFS of 27.00 (17.84-36.13) months. Univariate and multivariate Cox regression analyses showed that a shorter interval between radiotherapy and immunization [≤21 days; hazard ratio (HR) =1.10, 95% confidence interval (CI): 0.06-0.89; P=0.02] and a low NLR after SBRT (HR =0.24, 95% CI: 1.01-1.9; P=0.03) were associated with improved OS. The ROC curve identified 4.12 as the cutoff value for predicting OS based on NLR after SBRT. NLR after SBRT ≤4.12 significantly extended OS compared to NLR after SBRT >4.12 (log-rank P=0.001). Spearman correlation analysis and linear regression analysis showed that PTV was negatively correlated with ALC after SBRT. Our preliminary research shows that SBRT combined with immunotherapy has a good effect, and NLR after SBRT is a poor prognostic factor for OS. Larger PTV volume is associated with decreased ALC after SBRT.

Clinical outcomes and safety of external beam radiotherapy with extensive intrahepatic targets for advanced hepatocellular carcinoma: A single institutional clinical experience.

This study observed the clinical outcome of radiotherapy to extensive intrahepatic targets for advanced hepatocellular carcinoma (HCC) in a single institution. From September 2009 to July 2021, patients who underwent fractionated radiotherapy to a planning target volume (PTV) of over 100 ml with biological effective dose >30 Gy10 for advanced HCC were enrolled. Overall survival (OS) and radiation-induced liver toxicity (RILD) were evaluated. RILD was defined as an increase in Child-Pugh (CP) score ≥2 or liver function tests ≥2.5 times at 3 months after the end of radiotherapy. A total of 136 patients were evaluated. Eighty-nine patients had portal vein tumor thrombus (PVTT), 37 patients were in CP B stage, and the median radiation dose to PTV was 48.8 Gy10. The median OS was 12.3 months. The factors most affecting OS were PVTT (P = 0.001), PTV (>500 ml, P = 0.001), incomplete coverage of the intrahepatic tumor (P = 0.004), and CP B (P = 0.006) in Cox regression. RILD occurred in 22.4% of the patients and was affected by PVTT (P = 0.003), PTV (P = 0.010), pretreatment bilirubin levels (>1.5 mg/ml, P = 0.016), and the mean normal liver dose (MNLD) (≥ EQD2 18 Gy3, P = 0.021) in binary logistic regression. As the PTV was in excess of >500 ml, RILD developed in 30.2% of patients and the prognostic importance of pretreatment bilirubin levels (P = 0.006) and the MNLD (P = 0.014) increased. As PTV is more extensive, the bilirubin level and the MNLD have to be taken into consideration for safe radiotherapy, in addition to the traditional prognostic factors.

Stereotactic body radiotherapy in ultracentrally located lung tumors

Stereotactic body radiotherapy (SBRT) is a highly conformal radiotherapy technique that delivers high doses of radiation per fraction, typically in 1 &amp;ndash; 5 fractions. It is a standard treatment option for patients with early-stage non-small cell lung cancer that is peripherally located, for those who are medically inoperable, or for patients who do not opt for surgery. Similarly, SBRT is considered an effective treatment option for oligometastatic lung tumors. However, in the case of ultracentrally located lung tumors&amp;mdash;tumors situated close to the central airway and mediastinal region&amp;mdash;there is an increased risk of severe toxicities (grade 4 &amp;ndash; 5) due to the dose tolerances of the surrounding organs at risk. The definition of ultracentrally located lung tumors remains unclear. Some studies define an ultracentral lung tumor as one in which the gross tumor volume directly involves the proximal bronchial tree or trachea, while others define it as the planning target volume (PTV) that includes the trachea or main bronchial system. In addition, some studies consider tumors whose PTV touches or overlaps with the central bronchial tree, esophagus, pulmonary vein, or pulmonary artery as ultracentral. In addition, the optimal SBRT regime and organ-at-risk dose limitations for ultracentral tumors have yet to be clearly established. The aim of this review is to explore and discuss the role of SBRT in the treatment of ultracentrally located lung tumors.

In Silico Study of Simultaneous Integrated Boost Carbon-Ion Radiotherapy for Locally Advanced Pancreatic Cancer.

Carbon-ion radiotherapy (CiRT) has been used for the treatment of locally advanced pancreatic cancer (LAPC) with uniform dose plan. The aim of the present study is to investigate the effectiveness of a simultaneous integrated boost (SIB) technique with scanned CiRT against LAPC. Data of 21 patients with LAPC were used to compare two treatment planning approaches: a conventional uniform dose approach and a SIB approach. A relative biological effectiveness (RBE)-weighted dose (DRBE) of 55.2 Gy (RBE) in 12 fractions was prescribed to the planning target volume (PTV) in the conventional approach. In the SIB approach, DRBE of 67.2 Gy (RBE) and 43.2 Gy (RBE) in 12 fractions were prescribed to a high-risk PTV (HR-PTV) and low-risk PTV (LR-PTV), respectively. The DRBE and dose-averaged linear energy transfer (LETd) of targets and gastrointestinal tracts as organs at risk (OARs) were evaluated. The HR-PTV D90% and LR-PTV D90% were 64.4±0.6 and 42.5±0.1 Gy (RBE) in SIB approach compared to the PTV D90% of 54.1±0.4 Gy (RBE) in the conventional approach. All SIB plans achieved the D2cc lower than 46 Gy (RBE) and V30 lower than 4 cm3 within OARs. The SIB approach increased the minimum LETd within the GTV to 44 keV/μm or higher for 20 out of 21 patients as compared to 16 out of 21 patients in the conventional approach. The SIB approach effectively increased the RBE-weighted dose and LETd within the HR-PTV and GTV by accumulating the high-LET stopping carbon-ions into the HR-PTV in addition to the decreased RBE-weighted dose to OARs.

Comparison of two different VMAT radiotherapy TPSs for pancreatic cancer using flattening filter free photon beam energy

BackgroundPancreatic cancer is a devastating disease with a poor prognosis, and radiation therapy plays a crucial role in its treatment and management. Conventional radiation therapy (RT) techniques have limitations in delivering adequate doses to the tumor while sparing surrounding normal tissues. However, modern RT techniques such as intensity-modulated radiation therapy (IMRT), volumetric modulated arc therapy (VMAT), and stereotactic body radiation therapy (SBRT) have led to the development of novel approaches that can reduce toxicity. The incorporation of advanced imaging modalities, like four-dimensional computed tomography (4D-CT) and magnetic resonance imaging (MRI), enables enhancement of tumor control and improves conformality and treatment outcomes. Additionally, using flattening filter-free (FFF) beams can further enhance treatment efficiency and efficacy. PurposeThis study aims to compare two different VMAT techniques using two different treatment planning systems (TPSs), Monaco and Eclipse, in the treatment of pancreatic cancer II stage infiltrating duct carcinoma patients using an FFF photon beam. Materials and methods20 pancreatic cancer II stage infiltrating duct carcinoma patients were retrospectively analyzed, and each patient's plans were designed using the two TPSs. The dose distribution of the target using 6 MV FFF for TrueBeam-Varian and organs at risk (OARs) were compared. The monitor unit (MU), treatment time, conformity (CI), and homogeneity (HI) indices were also evaluated. ResultsFor pancreatic cancer patients, the mean dose of the planning target volume (PTV) in the Monaco plan was lower than the Eclipse plan. The plan evaluation parameters in Monaco and Eclipse were similar without significant differences (p-value = 0.152). The Monaco plan was better than the Eclipse plan regarding mean dose and V15Gy of the kidneys; the spinal cord was lowest in the Monaco plan, and the maximum dose and V45Gy of the spinal cord were 592.1 cGy and 1.37% lower than the Eclipse plan, respectively. ConclusionThe VMAT Monaco plan is a favorable TPS for pancreatic cancer patients, providing improved sparing of critical organs while maintaining adequate target coverage.

Hippocampal-Sparing Radiation Therapy in Primary Sinonasal and Cutaneous Tumors of the Head and Neck

Patients with primary sinonasal and cutaneous head and neck (H&N) malignancies often receive meaningful radiation dose to their hippocampi, but this not a classic avoidance structure in radiation planning. We aimed to characterize the feasibility and tradeoffs of hippocampal-sparing radiation therapy (HSRT) for patients with primary sinonasal and cutaneous H&N malignancies. We retrospectively selected patients who were treated definitively for primary sinonasal or cutaneous malignancies of the H&N at an academic medical center. All received (chemo)radiation alone or adjuvantly and substantial radiation dose to 1 or both hippocampi. We created new HSRT plans for each patient with intensity modulated radiation therapy using the original target and organ-at-risk (OAR) volumes. Hippocampi were contoured based on Radiation Therapy Oncology Group guidelines and reviewed by a neuroradiologist. Absolute and relative differences in radiation dose to the hippocampi, planning target volumes (PTVs), and OARs were recorded and compared. There were 18 sinonasal and 12 cutaneous H&N primary tumors (30 patients in total). Median prescription dose was 6600 cGy (range, 5000-7440 cGy), and 14 of the 30 patients received 120 cGy/fraction twice daily, 13 of the 30 patients received 200 cGy/fraction once daily, whereas others received 180-275 cGy/fraction once daily. The relative decrease in ipsilateral hippocampal Dmax and D100% using HSRT was 44% (median, 2009 cGy from 3586 cGy) and 65% (median 434 cGy from 1257 cGy), respectively. There were no statistically significant or clinically meaningful differences in PTV V100%, PTV D1%, or radiation dose to other OARs between HSRT and non-HSRT plans. HSRT is feasible and results in meaningful dose reduction to the hippocampi without reducing PTV coverage or increasing dose to other OARs. We suggest target hippocampal constraints of Dmax < 1600 cGy and D100% < 500 cGy when feasible (without compromising PTV coverage or impacting other critical OARs). The clinical significance of HSRT in patients with primary H&N tumors should be investigated prospectively.

FA-Net: A hierarchical feature fusion and interactive attention-based network for dose prediction in liver cancer patients

Dose prediction is a crucial step in automated radiotherapy planning for liver cancer. Several deep learning-based approaches for dose prediction have been proposed to enhance the design efficiency and quality of radiotherapy plan. However, these approaches usually take CT images and contours of organs at risk (OARs) and planning target volume (PTV) as a multi-channel input and is thus difficult to extract sufficient feature information from each input, which results in unsatisfactory dose distribution. In this paper, we propose a novel dose prediction network for liver cancer based on hierarchical feature fusion and interactive attention. A feature extraction module is first constructed to extract multi-scale features from different inputs, and a hierarchical feature fusion module is then built to fuse these multi-scale features hierarchically. A decoder based on attention mechanism is designed to gradually reconstruct the fused features into dose distribution. Additionally, we design an autoencoder network to generate a perceptual loss during training stage, which is used to improve the accuracy of dose prediction. The proposed method is tested on private clinical dataset and obtains HI and CI of 0.31 and 0.87, respectively. The experimental results are better than those by several existing methods, indicating that the dose distribution generated by the proposed method is close to that approved in clinics. The codes are available at https://github.com/hired-ld/FA-Net.