Inverse Intensity-modulated Radiotherapy Research Articles

Comparative Analysis of Dosimetry: IMRT versus 3DCRT in Left-Sided Breast Cancer Patients with Considering Some Organs in Out - of - Field Borders.

The local management approach for node-positive breast cancer has undergone substantial evolution. Consequently, there exists a pressing need to enhance our treatment strategies by placing greater emphasis on planning and dosimetric factors, given the availability of more conformal techniques and delineation criteria, achieving optimal goals of radiotherapy treatment. The primary aim of this article is to discuss how the extent of regional nodal coverage influences the choice between IMRT and 3D radiation therapy for patients. A total of 15 patients diagnosed with left breast cancer with disease involved lymph nodes were included in this study. Delivering the recommended dose required the use of a linear accelerator (LINAC) with photon beams energy of 6 mega voltage (6MV). Each patient had full breast radiation using two planning procedures: intensity-modulated radiotherapy (IMRT) and three-dimensional radiotherapy (3D conformal). Following the guidelines set forth by the Radiation Therapy Oncology Group (RTOG), the planned treatment coverage was carefully designed to fall between 95% and 107% of the recommended dose. Additionally, Dose Volume Histograms (DVHs) were generated the dose distribution within these anatomical contours. The DVH parameters were subjected to a comparative analysis, focusing on the doses absorbed by both Organs at Risk (OARs) and the Planning Target Volume (PTV). The findings suggest that low doses in IMRT plan might raise the risk of adverse oncological outcomes or potentially result in an increased incidence of subsequent malignancies. Consequently, the adoption of inverse IMRT remains limited, and the decision to opt for this therapy should be reserved for situations where it is genuinely necessary to uphold a satisfactory quality of life. Additionally, this approach helps in reducing the likelihood of developing thyroid problems and mitigates the risk of injuries to the supraclavicular area and the proximal head of the humerus bone.

Dosimetric comparison of dual arc- volumetric modulated arc therapy (DA-VMAT) and seven-field inverse intensity modulated radiotherapy (IMRT) applied in the curative treatment of cervical cancer

Dosimetric comparison of dual arc- volumetric modulated arc therapy (DA-VMAT) and seven-field inverse intensity modulated radiotherapy (IMRT) applied in the curative treatment of cervical cancer

‌Dosimetric comparison of forward and inverse intensity modulated radiation therapy planning, and volumetric modulated arc therapy for (6and10) MV x-ray photons for left breast cancer

Purpose of work To study the best planning techniques for post operative breast radiotherapy either F-IMRT or I-IMRT and VMAT . Another strategy is to check the dosimetric difference between using 6 or 10 MV energies for both I-IMRT and VMAT . Materials and Method: In the present study, four different inverse plans and one forward plan of randomly selected twenty left breast cancer patients were compared dosimetrically.Plans were done on Monaco (5.1) treatment planning system and data analyses were accomplished using one-way Anova test using IBM SPSS (20) data editor software. Results: Inverse planning achieve superior target coverage over forward planning (p value =0.001 ,0.07) and conformity index (p value < 0.05) maintaining adequate homogeneity index (p value = 0.461, 0.138) . Left lung and heart high dose levels decreased using I-IMRT, VMAT ( p value <0.05) at the cost of increasing volume irradiated by low doses (p value < 0.05 ). For contralateral lung VMAT increased absorbed dose over F-IMRT ( p < 0.05) but I-IMRT showed non significant increase of V5 GY ( p value = 0.14) .For contralateral breast both I-IMRT and VMAT increased absorbed dose over F-IMRT (P < 0.05 ) . Conclusion: It may be concluded that with inverse planning achieved better target coverage that increases tumor control . Inverse planning also achieved lower volume of high doses that reduces acute radiation effect and increased irradiated volume by low doses significantly that increases the probability of late radiation effect.

Postmastectomy Radiation Therapy Planning After Immediate Implant-based Reconstruction Using the European Society for Radiotherapy and Oncology-Advisory Committee in Radiation Oncology Practice Consensus Guidelines for Target Volume Delineation

AimsTo evaluate how common radiation therapy techniques perform in the setting of the new European Society for Radiotherapy and Oncology-Advisory Committee in Radiation Oncology Practice (ESTRO-ACROP) delineation recommendations for immediate breast reconstruction (IBR). Materials and methodsSeven Danish radiation therapy centres and six international European centres participated in this project. Two breast cancer cases (one left-sided and one right-sided) with a retropectoral implant were chosen for radiation therapy planning using deep-inspiration breath-hold. Target volumes were delineated according to ESTRO-ACROP delineation recommendations. The centres were asked to plan the cases using any radiation therapy technique according to the Danish Breast Cancer Group plan objectives. ResultsIn total, 35 treatment plans were collected. Half of the submitted plans, for both the left-sided and the right-sided case, used the field-in-field (FiF) technique (nine for each), a quarter used volumetric arc radiation therapy (VMAT; five for right-sided, four for left-sided) and the remaining quarter was a mix of inverse intensity-modulated radiation therapy (IMRT), helicoidal therapy and hybrid (combined open fields and VMAT) techniques. Mean clinical target volume doses were in the range 99–102% of the prescribed dose. The median FiF mean heart dose (MHD) for right-sided radiation therapy was 1 Gy (range 0.8–3.7) and 5.2 Gy for left-sided radiation therapy (range 2.2–6.5). For right-sided radiation therapy, the median VMAT MHD was 3.42 Gy, for IMRT was 2.3 Gy and for helicoidal therapy was 5.1 Gy. For left-sided radiation therapy, the median VMAT MHD was 6.3 Gy, for IMRT was 7.8 Gy and for helicoidal therapy was 7.3 Gy. ConclusionsDifferent radiation therapy techniques could be used to plan radiation therapy in the setting of IBR. FiF provided good coverage with acceptable organ at risk doses. The best dose distribution results as a trade-off between the objectives of target volume coverage and high-dose organ at risk inclusion. The radiation therapy technique affects the interplay between these objectives.

Evaluation of the clinical application of Auto-Planning module for IMRT plans of left breast cancer

Even with advanced inverse intensity modulated radiation therapy (IMRT) technique, the optimization of treatment plans remains a time-consuming task and the outcome is highly influenced by the experience of the planner and time pressure. Automated treatment planning is a current hot topic and new frontier in radiotherapy, which is expected to minimize the above problems. The quality and efficacy of the IMRT plans generated by the Auto-Planning module of the Pinnacle3 treatment planning system (TPS) were evaluated by comparing with traditional manual plans (MPs) for left breast cancer. Dose distributions of planning target volume (PTV) and organs at risk (OARs), treatment parameters including monitor units and number of control points, the planning time, and the quality assurance (QA) results were statistically compared for two types of treatment plans by Wilcoxon matched-pair signed-rank test followed by Bonferroni correction with a corrected significance threshold of 0.2%. Dose homogeneity of the PTV was better with automated plans (APs) (p < 0.001), but automatically generated plans showed inferior dose conformity (p < 0.001), when similar target coverage was obtained between the two planning methods. The low-dose distributions of left lung and heart were dramatically improved by Auto-Planning approach, which has the potential to reduce the risk of secondary cancer, and the V5, V10 and V15 were respectively decreased by 15.9%, 14.7% and 8.8% for left lung and 43.1%, 39.2%, and 24.9% for heart, compared with the corresponding values for the human-driven plans (all p < 0.001). AP had a significantly lower mean dose for all OARs compared with MP (all p < 0.001). Meanwhile, the D1 of contralateral breast was reduced by 1.86 Gy using Auto-Planning engine (p < 0.001). Additionally, significant difference was found for the average planning time (p < 0.001) which was reduced to just 10.10 min by using the Auto-Planning module. IMRT quality assurance was implemented by MartiXX detector, and both types of plans were practically acceptable on delivery and had no statistically significant differences. Moreover, the radiation oncologist preferred APs for all cases in terms of sparing of OARs. Overall, the evaluated automated planning algorithm is a good option for treating left breast cancer, which generates high quality treatment plans quickly and effectively. Auto-Planning method has wide clinical applicability since it is in favour of sharing knowledge and standardization of treatment plans.

&lt;p&gt;Postmastectomy radiotherapy using three different techniques: a retrospective evaluation of the incidental dose distribution in the internal mammary nodes&lt;/p&gt;

ObjectiveTo evaluate the incidental coverage dose to the internal mammary nodes (IMN) in patients treated with postmastectomy radiotherapy (PMRT) and its relationship with the treatment plan.Patients and methodsWe retrospectively analyzed 138 patients undergoing PMRT and divided them into three groups: three-dimensional conformal radiotherapy (3D-CRT), field-in-field forward intensity-modulated radiotherapy (F-IMRT), and inverse intensity-modulated radiotherapy (I-IMRT). The IMN were contoured according to the Radiation Therapy Oncology Group consensus and not included in the planning target volume. We analyzed incidental IMN dose coverage and its relationship with the lung and heart.ResultsThe mean dose (Dmean) to the IMN was 32.85 Gy for all patients, and the dose delivered to the IMN showed no differences in 3D-CRT, F-IMRT, and I-IMRT (33.80, 29.65, and 32.95 Gy, respectively). In addition, 10.42%, 2.04%, and 9.76% of patients achieved ≥45 Gy with 3D-CRT, F-IMRT, and I-IMRT, respectively. No differences were evident among the three treatment plans regarding IMN dose in the first three intercostal spaces (ICS1–3). The Dmean, V20, V30, V40, and V50 of ICS2 and ICS3 were superior to those of ICS1 for all three plans. For 3D-CRT, a moderate positive correlation was evident between the Dmean to the IMN and the Dmean to the heart. For F-IMRT and I-IMRT, positive correlations were evident between the Dmean of the IMN and the Dmean and V20 of the lung.ConclusionThe mean incidental dose to the IMN for IMRT (F-IMRT and I-IMRT) and 3D-CRT after modified radical mastectomy was insufficient to treat subclinical disease. A substantial dose was delivered to the IMN in some patients. Higher incidental doses to the IMN were associated with a higher heart mean dose for 3D-CRT and a higher dose to the lung for IMRT. Future prospective studies should further explore subgroups that do not require IMN irradiation.

Clinical implementation of magnetic resonance imaging guided adaptive radiotherapy for localized prostate cancer.

Background and purposeMagnetic resonance-guided radiation therapy (MRgRT) has recently become available in clinical practice and is expected to expand significantly in coming years. MRgRT offers marker-less continuous imaging during treatment delivery, use of small clinical target volume (CTV) to planning target volume (PTV) margins, and finally the option to perform daily plan re-optimization.Materials and methodsA total of 140 patients (700 fractions) have been treated with MRgRT and online plan adaptation for localized prostate cancer since early 2016. Clinical workflow for MRgRT of prostate cancer consisted of patient selection, simulation on both MR- and computed tomography (CT) scan, inverse intensity-modulated radiotherapy (IMRT) treatment planning and daily plan re-optimization prior to treatment delivery with partial organs at risk (OAR) recontouring within the first 2 cm outside the PTV. For each adapted plan online patient-specific quality assurance (QA) was performed by means of a secondary Monte Carlo 3D dose calculation and gamma analysis comparison. Patient experiences with MRgRT were assessed using a patient-reported outcome questionnaire (PRO-Q) after the last fraction.ResultsIn 97% of fractions, MRgRT was delivered using the online adapted plan. Intrafractional prostate drifts necessitated 2D-corrections during treatment in approximately 20% of fractions. The average duration of an uneventful fraction of MRgRT was 45 min. PRO-Q’s (N = 89) showed that MRgRT was generally well tolerated, with disturbing noise sensations being most commonly reported.ConclusionsMRgRT with daily online plan adaptation constitutes an innovative approach for delivering SBRT for prostate cancer and appears to be feasible, although necessitating extended timeslots and logistical challenges.

The Application of a New 3D Printed Individualized Bolus System for Superficial Lesions with Irregular Surface

To introduce a new 3D printed individualized bolus system for superficial lesions with irregular surface. Instead of the flat bolus, a new 3D printed individualized bolus system is used for patients of superficial lesions with irregular surface in Peking University First Hospital. The electron density of the 3D printed bolus is 1.00-1.01, which is close to water. Pre-clinical evaluations were done by using Alderson RANDO anthropomorphic phantom in three different modes: A) with no bolus; B) with a flat bolus; C) with a 3D printed bolus. Inverse Intensity modulated radiation therapy (IMRT) plans were designed for all modes respectively. For clinical evaluation, dosimetric parameters of 25 patients (28 IMRT plans) were analyzed. Daily kV-CBCT was used to assure the consistency of position. Acute and late toxicity, according to toxicity criteria of the Radiation Therapy Oncology Group (RTOG) and the European Organization for Research and Treatment of Cancer (EORTC), were record. The radiation dose prescribed to the PTV for the Alderson RANDO anthropomorphic phantom was 2Gy delivered in 1 fraction. Dmax of PTV of mode A, B, and C were 182.9cGY, 118.9cGY and 114.8cGY, respectively. Dmean of PTV of mode A, B, and C were 146.2cGY, 107.7cGY and 104.1cGY, respectively. HI (homogeneity index) in the IMRT plans of mode A, B, and C were 0.56, 0.15 and 0.11, respectively. 25 cases of superficial lesions with irregular surface were included. The primary lesions of 17 cases were on the penis and scrotum, 6 cases were on the head and face, and the last 2 cases were on the vulva. The dosimetric parameters of these 25 cases (28 IMRT plans) showed that all patients benefit from the 3D printed individualized bolus for its high conformity and dose uniformity (HImedian=0.09, range 0.03-0.29). 6 cases of Paget's disease of penis and scrotum benefit for their support and fixation. 3 cases had not finished the treatment.11 cases felt pain. 8 cases had edema. Serious treatment-related toxicity occurred (>G2) were seen in 4 cases. No recurrence was observed. The 3D-printed bolus can effectively improve the radiation dose of body surface for its high conformity and its function of support and fixation.

Breast-conserving radiotherapy with simultaneous integrated boost; field-in-field three-dimensional conformal radiotherapy versus inverse intensity-modulated radiotherapy - A dosimetric comparison: Do we need intensity-modulated radiotherapy?

Background and Purpose:To examine the feasibility of improving breast-conserving radiotherapy with simultaneous integrated boost (SIB) and analyzing the efficiency of forward versus inverse intensity-modulated radiotherapy (IMRT) techniques in providing the same.Materials and Methods:Three-dimensional conformal radiotherapy (3DCRT) field-in-field (FIF) plans with simultaneous and sequential boost and IMRT SIB plans were generated for the datasets of 20 patients who had undergone breast-conserving surgery. The 3 plans were compared dosimetrically for efficiency in terms of planning target volume (PTV) coverage (PTV 95%), homogeneity and conformity, dose delivered to ipsilateral/contralateral lungs (I/L: V10, V20, C/L: Vmean, V5), heart and contralateral breast (Vmean, V30 for heart and Vmean, V1, V5 for C/L breast).Results:The FIF 3DCRT plan with SIB (PLAN B) was more homogeneous than the classical technique with sequential boost (PLAN A). There were less hot spots in terms of Dmax (63.7 ± 1.3) versus Dmax (68.9 ± 1), P < 0.001 and boost V107%, B (0.3 ± 0.7) versus A (3.5 ± 5.99), P = 0.001. The IMRT SIB (PLAN C) did not provide any significant dosimetric advantage over the 3DCRT SIB technique. IMRT SIB plan C was associated with increased dose to contralateral lung in-terms of V5 (10.35 +/- 18.23) vs. (1.13 +/- 4.24), P = 0.04 and Vmean (2.12 ± 2.18) versus Vmean (0.595 ± 0.89), P = 0.008. There was 3-fold greater exposure in terms of Monitor Unit (MU) (1024.9 ± 298.32 versus 281.05 ± 20.23, P < 0.001) and treatment delivery time.Conclusions:FIF 3DCRT SIB provides a dosimetrically acceptable and technically feasible alternative to the classical 3DCRT plan with sequential boost for breast-conserving radiotherapy. It reduces treatment time by 2 weeks. IMRT SIB does not appear to have any dosimetric advantage; it is associated with significantly higher doses to contralateral lung and heart and radiation exposure in terms of MU.

Intensity-modulated radiation therapy: a review with a physics perspective.

Intensity-modulated radiation therapy (IMRT) has been considered the most successful development in radiation oncology since the introduction of computed tomography into treatment planning that enabled three-dimensional conformal radiotherapy in 1980s. More than three decades have passed since the concept of inverse planning was first introduced in 1982, and IMRT has become the most important and common modality in radiation therapy. This review will present developments in inverse IMRT treatment planning and IMRT delivery using multileaf collimators, along with the associated key concepts. Other relevant issues and future perspectives are also presented.

Reproducible deep-inspiration breath-hold irradiation with forward intensity-modulated radiotherapy for left-sided breast cancer significantly reduces cardiac radiation exposure compared to inverse intensity-modulated radiotherapy.

To investigate the objective utility of our clinical routine of reproducible deep-inspiration breath-hold irradiation for left-sided breast cancer patients on reducing cardiac exposure. Free-breathing and reproducible deep-inspiration breath-hold scans were evaluated for our 10 consecutive left-sided breast cancer patients treated with reproducible deep-inspiration breath-hold. The study was based on the adjuvant dose of 50 Gy in 25 fractions of 2 Gy/fraction. Both inverse and forward intensity-modulated radiotherapy plans were generated for each computed tomography dataset. Reproducible deep-inspiration breath-hold plans with forward intensity-modulated radiotherapy significantly spared the heart and left anterior descending artery compared to generated free-breathing plans based on mean doses - free-breathing vs reproducible deep-inspiration breath-hold, left ventricle (296.1 vs 94.5 cGy, P = 0.005), right ventricle (158.3 vs 59.2 cGy, P = 0.005), left anterior descending artery (171.1 vs 78.1 cGy, P = 0.005), and whole heart (173.9 vs 66 cGy, P = 0.005), heart V20 (2.2% vs 0%, P = 0.007) and heart V10 (4.2% vs 0.3%, P = 0.007) - whereas they revealed no additional burden on the ipsilateral lung. Reproducible deep-inspiration breath-hold and free-breathing plans with inverse intensity-modulated radiotherapy provided similar organ at risk sparing by reducing the mean doses to the left ventricle, left anterior descending artery, heart, V10-V20 of the heart and right ventricle. However, forward intensity-modulated radiotherapy showed significant reduction in doses to the left ventricle, left anterior descending artery, heart, right ventricle, and contralateral breast (mean dose, 248.9 to 12.3 cGy, P = 0.005). The mean doses for free-breathing vs reproducible deep-inspiration breath-hold of the proximal left anterior descending artery were 1.78 vs 1.08 Gy and of the distal left anterior descending artery were 8.11 vs 3.89 Gy, whereas mean distances to the 50 Gy isodose line of the proximal left anterior descending artery were 6.6 vs 3.3 cm and of the distal left anterior descending artery were 7.4 vs 4.1 cm, with forward intensity-modulated radiotherapy. Overall reduction in mean doses to proximal and distal left anterior descending artery with deep-inspiration breath-hold irradiation was 39% (P = 0.02) and 52% (P = 0.002), respectively. We found a significant reduction of radiation exposure to the contralateral breast, left and right ventricles, as well as of proximal and especially distal left anterior descending artery with the deep-inspiration breath-hold technique with forward intensity-modulated radiotherapy planning.

Comparison of incidental irradiation dose to the internal mammary nodes among I-IMRT, F-IMRT, and 3DCRT after breast-conserving surgery

Objective To explore the dosimetric variance in incidental irradiation to the internal mammary nodes among inverse intensity-modulated radiotherapy (I-IMRT), forward intensity-modulated radiotherapy (F-IMRT), and three-dimensional conformal radiotherapy (3DCRT) after breast-conserving surgery, and to provide a basis for deciding whether to spare the internal mammary nodes in clinical treatment. Methods A total of 84 patients undergoing breast-conserving surgery were enrolled as subjects. The internal mammary nodes in the first three intercostal spaces were contoured. Three radiotherapy plans were designed for each patient. The internal mammary nodes were not included in the planning target volume. Comparison was made among the three plans. The results were compared using Wilcoxon signed rank test. Results The I-IMRT, F-IMRT, and 3DCRT plans had similar median Dmean values for the internal mammary nodes, which were 2740.2, 2973.9, and 2951.4 cGy, respectively. The analyses of the three individual intercostal spaces showed that there was no difference in Dmean for the first intercostal space or the second intercostal space between the three plans; For the third intercostal space, however, I-IMRT had a significantly higher Dmean than 3DCRT and F-IMRT. The analyses of the three individual plans showed that for each plan, the Dmean was the highest in the third intercostal space, followed by the second intercostal space and the first intercostal space. Conclusions All the three plans fail to attain an adequate prescribed dose to cure subclinical disease, and there is no significant difference among the three plans. Therefore, it is risky to exclude the internal mammary nodes using any one of the three radiotherapy techniques for patients with clinical indications for internal mammary nodes radiation. In the combination therapy including chemotherapy, endocrine therapy, and targeted therapy, however, further follow-up is needed to determine whether the incidental irradiation dose to the internal mammary nodes could meet clinical requirement. Key words: Breast-conserving postoperative radiotherapy; Internal mammary lymph node region; Incidental irradiated dose; Treatment planning comparison

A knowledge-based approach to automated planning for hepatocellular carcinoma.

PurposeTo build a knowledge‐based model of liver cancer for Auto‐Planning, a function in Pinnacle, which is used as an automated inverse intensity modulated radiation therapy (IMRT) planning system.Methods and MaterialsFifty Tomotherapy patients were enrolled to extract the dose–volume histograms (DVHs) information and construct the protocol for Auto‐Planning model. Twenty more patients were chosen additionally to test the model. Manual planning and automatic planning were performed blindly for all twenty test patients with the same machine and treatment planning system. The dose distributions of target and organs at risks (OARs), along with the working time for planning, were evaluated.ResultsStatistically significant results showed that automated plans performed better in target conformity index (CI) while mean target dose was 0.5 Gy higher than manual plans. The differences between target homogeneity indexes (HI) of the two methods were not statistically significant. Additionally, the doses of normal liver, left kidney, and small bowel were significantly reduced with automated plan. Particularly, mean dose and V15 of normal liver were 1.4 Gy and 40.5 cc lower with automated plans respectively. Mean doses of left kidney and small bowel were reduced with automated plans by 1.2 Gy and 2.1 Gy respectively. In contrast, working time was also significantly reduced with automated planning.ConclusionsAuto‐Planning shows availability and effectiveness in our knowledge‐based model for liver cancer.

Dosimetric study of three-dimensional conformal radiotherapy, electronic compensator technique, intensity-modulated radiation therapy and volumetric-modulated arc therapy in whole breast irradiation

AbstractBackgroundWhole breast irradiation is an essential treatment after breast-conserving surgery (BCS). However, there are some adverse effects from inhomogeneity and dose to adjacent normal tissues.ObjectiveAim of this study was to compare dosimetry among standard technique, three-dimensional conformal radiotherapy (3D-CRT), and advanced techniques, electronic compensator (ECOMP), inverse intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT).MethodsWhole breast irradiation treatment plans of patients who had underwent BCS and whole breast irradiation were re-planned with all four techniques. Clinical target volume was contoured according to the Radiation Therapy Oncology Group atlas for breast only in patients who had negative node or ductal carcinoma in situ and breast with chest wall for patients with positive node. Planning target volume was non-uniformly expanded. Dose prescription was 50 Gy in 25 fractions with 6 MV photon energy.ResultsIn total, 25 patients underwent whole breast irradiation with computed tomography simulation from November 2013 to November 2014 were included. Six patients with positive nodes were re-planned for breast with chest wall irradiation and 19 patients with negative nodes were re-planned for breast only irradiation. Primary outcome, radical dose homogeneity index (HI) of 3D-CRT, ECOMP, IMRT and VMAT were 0·865, 0·889, 0·890 and 0·866, respectively. ECOMP and IMRT showed significant higher HI than 3D-CRT (p-value&lt;0·001). Secondary outcome, conformity index (CI) of advanced technique were significantly better than 3D-CRT. Lung V20, mean ipsilateral lung dose (MILD), mean heart dose (MHD), heart V25, heart V30 of advanced techniques were also lower than 3D-CRT. ECOMP had better mean lung dose (MLD), mean contralateral lung dose (MCLD) and mean contralateral breast dose (MCBD) when compared with 3D-CRT. Monitor units of advanced techniques were significantly higher than 3D-CRT.ConclusionsHI of ECOMP and IMRT were significantly higher than 3D-CRT technique. All advanced techniques showed statistically better in CI. Lung V20, MILD, heart V25 and heart V30 of advanced techniques were lower than 3D-CRT. However, only ECOMP showed decreased MLD, MHD, MCLD and MCBD when compared with 3D-CRT.

Dosimetric comparison between automatic three-dimensional conformal radiotherapy, inverse three-dimensional conformal radiotherapy, and inverse intensity-modulated radiotherapy

Objective To compare dosimetric parameters between automatic three-dimensional conformal radiotherapy (a3DCRT), inverse three-dimensional conformal radiotherapy (i3DRT), inverse intensity-modulated radiotherapy (iIMRT). Methods Ten lung cancer patients with a single target and 10 intracranial tumor patients also with a single target, who were treated in our radiotherapy center from 2014 to 2015, were included in the study. Their image data were transferred to RayStation 4.5 via network, and then the treatment plans for a3DCRT, i3DCRT, and iIMRT were designed for the 20 patients. The dosimetric parameters for planning target volume (PTV) and organs at risk (OAR) were compared between the three plans using multiple dependent variables and two dependent variables. Results For lung cancer patients, iIMRT achieved better results in D98%, D50%, D2%, conformity index (CI), and homogeneity index (HI) than i3DCRT and a3DCRT (P=0.007, 0.001, 0.002, 0.000, and 0.000), and the CI of a3DCRT was superior to that of i3DCRT (P=0.000); there were no significant differences in heart D33, spinal cord Dmax and D1 cm3, and both lungs between the three plans (P=0.702, 0.237, 0.163, 0.739, 0.908, 0.832, 0.886, 0.722, 0.429, 0.840, and 0.702). For intracranial tumor patients, there were no significant differences in dosimetric parameters between the three plans, except that the CI of iIMRT and a3DCRT was superior to that of i3DCRT (P=0.648, 0.783, 0.256, 0.931, 0.002, and 0.034); there were no significant differences in whole brain irradiation dose between the three plans (P=0.446, 0.755, 0.772, 0.0266, 0.440, 0.290, and 0.939). Conclusions For the single target in patients with lung cancer and intracranial tumors, a3DCRT can improve the CI of PTV compared with i3DCRT, and shows no significant dosimetric disadvantage for OARs compared with iIMRT. Considering the simplicity and low cost of 3DCRT, a3DCRT holds promise as a novel radiotherapy technique. Key words: Beamset’s orientation auto-optimization; Inverse three-dementional conformal radiotherapy; Automatic three-dementional conformal radiotherapy; Inverse intensity-modulated radiotherapy

Multibeam inverse intensity-modulated radiotherapy (IMRT) for whole breast irradiation: a single center experience in China

To present the clinical experience in our cancer center with multibeam inverse intensity-modulated radiotherapy (IMRT) for early stage breast cancer (BC) patients with whole breast irradiation (WBI). We retrospectively analyzed 622 patients with Stage 0 to III BC treated from 2008 to 2011 with wide local excision and WBI, using an inverse IMRT technique. All of the patients were prescribed a total dose of 50 Gy to the whole breast in 2-Gy fractions, followed by a tumor bed boost of 10 Gy in 5 fractions using an electron beam. Of all of the patients, 132 (21.2%) received whole breast plus regional lymph node (RLN) irradiation. 438 of 622 patients had records of acute skin toxicity based on common terminology criteria (CTC) for adverse events. Two hundred eighty (64%) patients had Grade 0/1 toxicity, 153 (35%) had Grade 2 and only 4 patients experienced grade 3 toxicity. Seventy patients (16%) had moist desquamation. Univariate analysis revealed that breast planning target volume was the only predictive factor for Grade ≥2 acute dermatitis (P = 0.002). After 4 years, 170 patients reported cosmetic results by self-assessment, of whom 151 (89%) patients reported good/excellent cosmetic results, and 17 (11%) patients reported fair assessments. For invasive cancer, the four-year rate of freedom from locoregional recurrence survival was 98.3%. Regarding carcinoma in situ, no patients experienced recurrence. BC patients who underwent conservative surgery followed by inverse IMRT plan exhibited acceptable acute toxicities and clinical outcomes. Longer follow-up is needed.

Challenges and differences in external radiation therapy for retinoblastoma: from standard techniques to new developments.

The purpose of this study is to calculate the treatment plans and to compare the dose distributions and dose-volume histograms (DVH) for 6 external radiotherapy techniques for the treatment of retinoblastoma as well as intensity-modulated radiotherapy (IMRT) and fractionated stereotactic radiotherapy (Cyberknife). Treatment plans were developed using 6 techniques, including an en face electron technique (ET), an anterior and lateral wedge photon technique (LFT), a 3D conformal (6 fields) technique (CRT), an inverse plan IMRT, tomotherapy, and conventional focal stereotactic external beam radiotherapy with Cyberknife (SBRT). Dose volume analyses were carried out for each technique. All techniques except electron provided similar target coverage. When comparing conformal plan with IMRT and SBRT, there was no significant difference in planning target volume dose distribution. The mean volume of ipsilateral bony orbit received more than 20 Gy, a suggested threshold for bone growth inhibition. The V20 Gy was 73% for the ET, 57% for the LFT, 87% for the CRT, 65% for the IMRT, 66% for the tomotherapy, and 2.7% for the SBRT. This work supports the potential use of IMRT and SBRT to spare normal tissues in these patients.

Dosimetric comparison of left-sided whole-breast irradiation with 3DCRT, forward-planned IMRT, inverse-planned IMRT, helical tomotherapy, and volumetric arc therapy

PurposeThis study evaluated the dose distribution and homogeneity of four different types of intensity-modulated radiotherapy (IMRT) in comparison with standard wedged tangential-beam three-dimensional conformal radiotherapy (3DCRT) of the left breast in patients who had undergone lumpectomy. Materials and methodsFive radiotherapy treatment plans, including 3DCRT, forward-planned IMRT (for-IMRT), inverse IMRT (inv-IMRT), helical tomotherapy (HT) and volumetric-modulated arc therapy (VMAT), were created for 15 consecutive patients. ResultsAll modalities presented similar target coverage. Target max doses were reduced with for-IMRT compared to 3DCRT, and these doses were further reduced with inv-IMRT and HT. HT resulted in the lowest max doses delivered to the heart, left anterior descending artery (LAD), and ipsilateral lung, but had higher mean, max, and low doses delivered to contralateral breast. HT resulted in increased low doses to a large volume of healthy tissue. Compared to other techniques, all inverse-planned modalities significantly improved conformity number; however, VMAT had worse homogeneity. The for-IMRT plan significantly lowered monitor unit (MU) compared to the inverse-planned techniques. ConclusionAll modalities evaluated provide adequate coverage of the whole breast. For-IMRT improves target homogeneity compared with 3DCRT, but to a lesser degree than the inverse-planned inv-IMRT and HT. HT decreases the ipsilateral OAR volumes receiving higher and mean doses with an increase in the volumes receiving low doses, which is known to lead to an increased rate of radiation-induced secondary malignancies.

Living with the Elekta Compact: Limitations and ways around them.

Elekta AB, Sweden has recently propagated the Elekta Compact--a low-cost, small-footprint, single energy (6MV), linear accelerator, in India. The absence of electron beams and the inability to seamlessly deliver inverse planned intensity modulated radiotherapy (IMRT) segments, mean that some out-of-the-box thinking is mandatory for the full range of required treatments in different clinical settings, but is ultimately very rewarding. Our department started off in July 2011, with the Elekta Compact, equipped with MLCi2 and a camera-based electron portal imaging device. For head-neck cancers, we have successfully utilized a 3D conformal class-solution of eight-to-nine oblique beams, with multiple segments, to deliver an adequate dose to the posterior neck, respecting spinal cord tolerance. Parotid gland sparing is possible in selected node-negative hypopharyngeal/laryngeal cancers. For prostate cancers, we have developed a forward-planned IMRT protocol to routinely deliver 76-80 Gy to the prostate, with margins, while conforming to the same rectal dose-volume constraints as in inverse IMRT. Response and tolerance have been excellent so far. In head-neck cancers, the majority (71%) of patients was locally advanced; however, complete response was achieved in 75% of the cases. Grade 3 acute toxicities were seen in only 7% of the cases and compliance overall was excellent, with no patients requiring a gap in treatment. We achieved biochemical control in 100% of the prostate cancer patients; no patients had grade 3 acute toxicities, and with a median follow-up of 12 months, have yet to see any late rectal bleeding. Although engineered for simplicity and versatility, the Compact requires some innovative thinking by clinicians/physicists to optimize the full range of its possibilities. However, upgrades like inverse IMRT delivery, which are in the pipeline, are urgently needed for it to be viable, especially in a single-accelerator department.

Dosage studies on simplified inverse intensity modulated radiotherapy in patients with early-stage breast cancer after breast-conserving surgery

Objective To compare the dosage characteristics between three-dimensional conformal radiotherapy （3DCRT）plan and simplified inverse dynamic intensity modulated radiotherapy （IMRT）in patients with early-stage breast cancer after breast-conserving surgery.Methods 3DCRT and IMRT treament plans were designed for 14 female patients with early-stage breast cancer after breast-conserving surgery,4 of whom were left breast cancer cases.A dose of 50 Gy in 25 fractions to the whole ipsilateral breast was delivered using 6 MV photons for 3DCRT or IMRT.For 3DCRT plans,tangential field irradiation was adopted.While for IMRT,reverse dynamic intensity modulated technology was done through two pairs of tangential-likely fields, and 10 Gy was boosted to the tumor bed concomitantly in 25 fractions.The conformity index （CI）,heterogenei-ty index （HI）,dose and volume of organs at risk were evaluated by dose volume histograms （DVH）.Results Compared with 3DCRT plans for ipsilateral lung,the high dose volumes were reduced and the low dose volumes were increased in IMRT plans.The same phenomenon was also observed for the heart of the patient with left breast cancer.The crosspoint doses of 3DCRT DVH and IMRT DVH for lung or heart were （25.16 ±9.11） Gy,（28.63 ±10.41 ）Gy respectively.There was no difference between the two plans in the V10 of contra-lateral breast [IMRT（4.13 ±5.17）%∶3DCRT（1.99 ±2.43）%,t=2.11,P>0.05],but the D30 and mean of IMRT plan were higher than that of 3DCRT [（2.23 ±1.77）Gy ∶（1.20 ±0.46）Gy,t=2.58,P 0.05].While the CI of IMRT plans were improved compared with 3DCRT [（0.75 ±0.07）∶（0.62 ±0.09）,t =5.68,P<0.000 1]. Conclusion Compared with 3DCRT plan in patients with early-stage breast cancer after breast-conserving surgery,the main advantages of four fields simplified inverse dynamic IMRT are concomitant tumor boosting, decreasing the high dose volumes of ipsilateral lung,and improving the CI of planning target volume at the same time,but the HI is not improved.The IMRT plan is a simple,rational and feasible design scheme. Key words: Breast neoplasms; Intensity-modulated radiotherapy; Radiotherapy dosage; Breast conser-ving surgery