Comparative Planning Study Research Articles

Planungssysteme vergleichen – aber wie?

International comparative planning studies is a growing field of planning research that enjoys increasing recognition. In Europe in particular, various approaches have emerged over recent decades that can be considered established in the scholarly literature. However, a closer look at the literature reveals some weaknesses, particularly against the background of the methodological quality criteria of social science comparative research. For example, explanatory comparisons are rare in comparative planning studies. Often, case study research designs are chosen, while large N studies and qualitative comparative analysis (QCA) are still rarely used. This paper summarises these weaknesses and points out avenues for further development.English title: How can we best compare different planning systems?

Individualised Estimation of Quality-adjusted Survival Benefit and Cost-effectiveness of Proton Beam Therapy in Intermediate-stage Hodgkin Lymphoma

AimsRadiotherapy for Hodgkin lymphoma leads to the irradiation of organs at risk (OAR), which may confer excess risks of late effects. Comparative dosimetry studies show that proton beam therapy (PBT) may reduce OAR irradiation compared with photon radiotherapy, but PBT is more expensive and treatment capacity is limited. The purpose of this study is to inform the appropriateness of PBT for intermediate-stage Hodgkin lymphoma (ISHL). Materials and methodsA microsimulation model simulating the course of ISHL, background mortality and late effects was used to estimate comparative quality-adjusted life years (QALYs) lived and healthcare costs after consolidative pencil beam scanning PBT or volumetric modulated arc therapy (VMAT), both in deep-inspiration breath-hold. Outcomes were compared for 606 illustrative patients covering a spectrum of clinical presentations, varying by two age strata (20 and 40 years), both sexes, three smoking statuses (never, former and current) and 61 pairs of OAR radiation doses from a comparative planning study. Both undiscounted and discounted outcomes at 3.5% yearly discount were estimated. The maximum excess cost of PBT that might be considered cost-effective by the UK's National Institute for Health and Care Excellence was calculated. ResultsOAR doses, smoking status and discount rate had large impacts on QALYs gained with PBT. Current smokers benefited the most, averaging 0.605 undiscounted QALYs (range –0.341 to 2.171) and 0.146 discounted QALYs (range –0.067 to 0.686), whereas never smokers benefited the least, averaging 0.074 undiscounted QALYs (range –0.196 to 0.491) and 0.017 discounted QALYs (range –0.030 to 0.086). For the gain in discounted QALYs to be considered cost-effective, PBT would have to cost at most £4812 more than VMAT for current smokers and £645 more for never smokers. This is below preliminary National Health Service cost estimates of PBT over photon radiotherapy. ConclusionIn a UK setting, PBT for ISHL may not be considered cost-effective. However, the degree of unquantifiable uncertainty is substantial.

3D-CRT, IMRT and VMAT for flank irradiation due to pediatric Wilms tumor: A comparative planning study with XCAT phantoms

PurposeTo compare the dosimetric parameters and radiogenic risks from 3D-CRT, IMRT and VMAT for flank irradiation due to pediatric Wilms tumor. MethodsTwo computational XCAT phantoms simulating an average 5- and 10-year-old patient were used. Four different planning target volumes (PTVs) for right flank (RF) and left flank (LF) irradiation with or without paraaortic lymph nodes (LNs) and eight surrounding organs-at-risk (OARs) were contoured on the phantoms’ CT sections. Forty-eight 3D-CRT, IMRT and VMAT plans were created using 6 and 10-MV photons on the two phantoms. The target coverage index (TCI), homogeneity index (HI), conformity index (CI), conformation number (CN) and OAR exposure were determined through dose-volume histogram (DVH) analysis. Second cancer risks were estimated using a non-linear model and DVH data. ResultsThe IMRT and VMAT for LF + LN and RF + LN irradiation reduced the radiation dose to four to six out of the eight OARs compared to 3D-CRT. Conventional treatment provided a better organ sparing for RF and LF irradiation. The IMRT and VMAT led to superior planning parameters in respect to 3D-CRT for all PTVs and both patient’s ages (3D-CRT: TCI = 59.80 % - 82.26 %, CI = 0.55–0.81, CN = 0.40–0.64, HI = 1.11–1.15; IMRT: TCI = 96.04 % - 99.72 %, CI = 0.85–0.91, CN = 0.85–0.88, HI = 1.03–1.05; VMAT: TCI = 96.02 % - 99.69 %, CI = 0.86–0.91, CN = 0.85–0.89, HI = 1.03–1.06). The excess-absolute-risk for developing secondary small intestine, liver and stomach malignancies from 3D-CRT were (7.99–19.32) × 10-4, (0.29–3.83) × 10-4 and (0.37–4.50) × 10-4 persons-year, respectively. The corresponding risks from intensity modulated techniques reached to 22.26 × 10-4, 4.58 × 10-4 and 5.42 × 10-4 persons-year. ConclusionsThis dataset related to plan quality, radiation dose and risks to OARs allows the selection of the proper treatment technique for flank irradiation based on the patient’s age and target site.

Latin American spatial governance and planning systems and the rising judicialisation of planning

Recent studies on Latin American Spatial Governance and Planning Systems (SGPSs) have highlighted the need to focus on alternative processes and mechanisms of land-use management and transformation that, arising and operating alongside the formal ones, contribute to shaping the nature of SGPSs themselves. This paper taps into this ongoing debate by further unfolding this ‘other institutionality’ and broadening its scope. It does so through the exploration of three case studies – namely the SGPSs of Argentina, Chile, and Uruguay – here analysed in relation to their institutional and legal frameworks and the instruments that are produced. In relation to each case, the local spatial planning practices in intermediary cities are examined, enabling understanding of the nuances of the ‘other institutionality’ mentioned and the role that the latter plays in the overall SGPS. The analysis shows an ongoing ‘judicialisation’ of spatial planning in the form of an increasing number of legal actions undertaken by civil society and the mobilisation of legal expertise in addressing the urban conflicts. This phenomenon seems to be related to the lack of updated spatial planning tools and public participatory processes to accompany official spatial planning practices. Overall, these findings open a pathway for further comparative spatial planning studies broadening the concept of the ‘other institutionality’ in Latin America and beyond and shedding light on the role and impact of the latter within existing SGPSs.

Inverse planning in Gamma Knife radiosurgery: A comparative planning study.

To determine the advantages of inverse planning using a prerelease version of Leksell Gamma Knife® (LGK) Lightning (Elekta AB, Sweden) compared to manual forward planning. Thirty-eight patients with metastases (MET, n=15), vestibular schwannomas (VS, n=11) and meningiomas (MEN, n=12), treated with LGK Icon™ at our institution, were analyzed retrospectively. For each case, an inverse (inv) and inverse full coverage (fc) treatment plan was generated using LGK Lightning and compared to the clinical plans. Several dosimetry and efficiency characteristics were compared for each indication. The mean, median difference and interquartile range were reported and the significance was assessed with a paired-sample Wilcoxon test (significance level<0.05). Further, the inter operator variability was analyzed for multiple users. Inv and fc treatment plans show improved target coverage (up to 3.6%) for all analyzed paradigms. For inv plans, the selectivity is enhanced (MET: 2.9%; VS: 1.8%; MEN: 1%) and the organ at risk doses are significantly reduced (VS: up to 4.5%; MEN: up to 17.5%). For inv and fc plans, the beam on time (BOT) is shortened (MET: up to 7.9%; benign tumors: 49.5%). The inter operator variability analysis shows similar treatment plan quality with small differences in plan efficiency (difference in BOT: 1-3.3min). LGK Lightning allows to generate improved LGK treatment plans regarding plan quality with reduced BOT compared to manual forward plans. The inter operator variability showed that multiple users with different experiences can generate similar treatment plan quality using LGK Lightning.

Testing comparative spatial planning studies in the Latin American context: theoretical implications and challenges for regional development

Até ao momento, os estudos comparativos de planeamento territorial têm-se foco predominantemente no continente europeu. Desde o final da década de 1980, um crescente número de estudos tem contribuído para a proliferação de abordagens teóricas e metodológicas, bem como para uma melhor definição do objeto de estudo. Ao mesmo tempo, a comparação orientada a outros países do mundo é menos frequente, se excluídos os 'estéreis' relatórios desenvolvidos por organizações internacionais. Com enfoque na investigação das razões por detrás deste vazio empírico, o artigo analisa as implicações teóricas e os desafios que emergem quando se aplicam no Sul Global estruturas conceptuais e analíticas desenvolvidas no Hemisfério Norte. Para fazer isso, o artigo enfatiza o papel do legado colonial e, em seguida, argumenta a necessidade de ‘ir além da eficiência técnica’ do planeamento e considerar as relações de poder dominantes escondidas por trás da aparente neutralidade dos sistemas de planeamento e governança do território, particularmente em contextos onde as desigualdades espaciais são mais profundas. Nesse sentido, o artigo sugere considerar as práticas informais paralelamente às formais, como uma maneira de entender melhor os elementos que estruturam os sistemas de planeamento territorial e governança no Sul Global. Em suma, testar estudos comparativos de planeamento territorial na América Latina pode oferecer um valor agregado ao desenvolvimento regional, estabelecendo uma agenda regional para um planeamento do território mais integrado e cooperativo.

An in silico comparative planning study investigating the predicted benefit of dysphagia-optimised volumetric arc therapy (Do-VMAT), relative to standard VMAT (S-VMAT), to reduce radiotherapy-associated dysphagia (RAD) in oropharyngeal cancers (OPC).

e18540 Background: RAD is a significant treatment-related functional morbidity in OPC and is associated with irradiation of the pharyngeal constrictor muscle (PCM). This study investigated whether a novel PCM-sparing Do-VMAT technique reduced the risk of RAD, compared to S-VMAT. Methods: Twenty OPC patients who previously underwent radiotherapy (RT) to bilateral neck were selected for this retrospective study. For each patient, S-VMAT and Do-VMAT plans were created. In both arms, the mucosal and nodal tumour received 65 Gy while the remaining oropharynx and at-risk nodal levels received 54 Gy; delivered in 30 fractions over 6 weeks. For Do-VMAT, a mandatory mean dose constraint of &lt; 50 Gy to the volume of the combined superior (SPCM) and middle PCM (MPCM) together with an optimal dose constraint of &lt; 20 Gy to the volume of inferior PCM (IPCM), lying outside the high-dose clinical target volume, were additionally defined and optimised to minimise PCM dose. Normal tissue complication probabilities for physician-scored RAD at 6 months (RAD6M) were determined as per the model by Christianen et al in which the 2 variables were mean dose to SPCM and supraglottic larynx (SGL). Statistical analysis was performed using paired t tests. Results: All plans had adequate target volume coverage, and dose to critical organs were within acceptable parameters. Dose to the parotid and submandibular glands were similar between the 2 RT techniques. The mean integral dose was 110.8 Gy-litre (standard deviation 17.1) with S-VMAT and 103.4 Gy-litre (15.4) with Do-VMAT, p &lt; 0.001. With Do-VMAT, the average of the mean dose to PCM, SPCM, MPCM, IPCM, and SGL were 9.3 Gy (1.4), 4.7 Gy (1.7), 7.4 Gy (3.6), 22.7 Gy (4.1), and 2.6 Gy (2.3) respectively lower than S-VMAT (p &lt; 0.001 for all). The mean predicted risk for RAD6M was 31.0 % (4.4) with S-VMAT, and 23.9 % (3.8) with Do-VMAT, p &lt; 0.001. The absolute reduction in estimated toxicity risk with Do-VMAT was &gt; 5 %, the minimally clinically important difference, in every patient. Conclusions: Do-VMAT demonstrated clinically relevant reductions in the predicted risk of RAD, compared to S-VMAT, by reducing dose to the PCM in OPC. The clinical benefits of Do-VMAT is being prospectively evaluated in DARS (CRUK/14/014), a randomised phase III study.

Intensity modulated proton therapy compared to volumetric modulated arc therapy in the irradiation of young female patients with hodgkin\u2019s lymphoma. Assessment of risk of toxicity and secondary cancer induction

BackgroundTo investigate the role of intensity modulated proton therapy (IMPT) compared to volumetric modulated arc therapy (VMAT) for advanced supradiaphragmatic Hodgkin’s lymphoma (HL) in young female patients by assessing dosimetric features and modelling the risk of treatment related complications and radiation-induced secondary malignancies.MethodsA group of 20 cases (planned according to the involved-site approach) were retrospectively investigated in a comparative planning study. Intensity modulated proton plans (IMPT) were compared to VMAT RapidArc plans (RA). Estimates of toxicity were derived from normal tissue complication probability (NTCP) calculations with either the Lyman or the Poisson models for a number of endpoints. Estimates of the risk of secondary cancer induction were determined for lungs, breasts, esophagus and thyroid. A simple model-based selection strategy was considered as a feasibility proof for the individualized selection of patients suitable for proton therapy.ResultsIMPT and VMAT plans resulted equivalent in terms of target dose distributions, both were capable to ensure high coverage and homogeneity. In terms of conformality, IMPT resulted ~ 10% better than RA plans. Concerning organs at risk, IMPT data presented a systematic improvement (highly significant) over RA for all organs, particularly in the dose range up to 20Gy. This lead to a composite average reduction of NTCP of 2.90 ± 2.24 and a reduction of 0.26 ± 0.22 in the relative risk of cardiac failures. The excess absolute risk per 10,000 patients-years of secondary cancer induction was reduced, with IMPT, of 9.1 ± 3.2, 7.2 ± 3.7 for breast and lung compared to RA. The gain in EAR for thyroid and esophagus was lower than 1. Depending on the arbitrary thresholds applied, the selection rate for proton treatment would have ranged from 5 to 75%.ConclusionIn relation to young female patients with advanced supradiaphragmatic HL, IMPT can in general offer improved dose-volume sparing of organs at risk leading to an anticipated lower risk of early or late treatment related toxicities. This would reflect also in significantly lower risk of secondary malignancies induction compared to advanced photon based techniques. Depending on the selection thresholds and with all the limits of a non-validated and very basic model, it can be anticipated that a significant fraction of patients might be suitable for proton treatments if all the risk factors would be accounted for.

Hippocampal sparing radiotherapy in adults with primary brain tumours: a comparative planning and dosimetric study using IMPT, IMRT and 3DCRT.

Abstract Introduction We assessed the feasibility of hippocampal sparing in adults with primary brain tumours using Intensity Modulated Proton Therapy (IMPT) and compared this with Intensity Modulated Radiotherapy (IMRT) and 3D-Conformal Radiotherapy (3DCRT). Methods and Materials 20 patients were identified, and each patient underwent a radiotherapy planning CT scan and 2 MRI scans. A pre-operative diagnostic MRI scan was fused with the planning CT and used for target delineation and a dedicated 3T MRI scan at the time of planning was fused with the CT for hippocampus delineation. 3 hippocampal sparing plans were generated for each patient with specific prescriptions (54Gy/30 fractions, 60Gy/30 fractions and 59.4Gy/33 fractions) using IMPT, IMRT and 3DCRT. Hippocampal sparing was defined as median dose to contralateral hippocampus ≤25Gy without compromising target coverage and organ at risk dose constraints. Results Hippocampal sparing was achieved in 19 patients (95%) with IMPT, 16 patients (80%) with IMRT and 13 patients (65%) with 3DCRT. The largest median hippocampal dose reduction was seen with IMPT, with a mean median hippocampal dose of 4.8Gy (range: 0.0Gy-24.9Gy), 14.6Gy (range: 1.9Gy-21.7Gy), and 16.2Gy (range: 2.3Gy-25.0Gy) for IMPT, IMRT and 3DCRT respectively. Hippocampal sparing IMPT failed in one case with the largest tumour volume (650cc) where 2/3 of the hippocampus overlapped the target volume. Conclusion IMPT as compared to IMRT and 3DCRT plans showed a trend towards significant and effective hippocampal sparing in adult patients with primary brain tumours. We are currently evaluating this in a larger patient cohort and comparing IMPT with VMAT.

Comparative analysis between interstitial brachytherapy and stereotactic body irradiation for local ablation in liver malignancies

PurposeInterstitial high-dose-rate brachytherapy (BT) is an alternative treatment option to stereotactic body radiotherapy (SBRT) for the ablative treatment of liver malignancies. The aim of the present comparative planning study was to reveal the possibilities and limitations of both techniques with regard to dosimetric properties. Methods and MaterialsEighty-five consecutive patients with liver malignancy diagnosis were treated with interstitial BT between 12/2008 and 09/2009. The prescription dose of BT varied between 15 and 20 Gy, depending on histology. For dosimetric comparison, virtual SBRT treatment plans were generated using the original BT planning CTs. Additional margins reflecting the respiratory tumor motion were added to the target volumes for SBRT planning. ResultsThe mean PTVBT was 34.7 cm3 (0.5–410.0 cm3) vs. a mean PTVSBRT of 73.2 cm3 (6.1–593.4 cm3). Regarding the minimum peripheral dose (D99.9), BT achieved the targeted prescription dose of 15 Gy/20 Gy better without violating organ at risk constraints. The dose exposure of the liver was significantly influenced by treatment modality. The liver exposure to 5 Gy was statistically lower with 611 ± 43 cm3 for BT as compared with 694 ± 37 cm3 for SBRT plans (20-Gy group, p = 0.001), corresponding to 41.8% vs. 45.9% liver volume, respectively. ConclusionsTo the best of our knowledge, this is the first report on the comparison of clinically treated liver BT treatments with virtually planned SBRT treatments. The planning study showed a superior outcome of BT regarding dose coverage of the target volume and exposed liver volume. Nevertheless, further studies are needed to determine ideal applicability for each treatment approach.

Vulvar Cancer: Dosimetric Comparison of Advanced 3D Conformal Radiation Therapy Technique with Anteroposterior and Posteroanterior Irradiation Techniques

Introduction: The commonly used technique of radiation therapy for vulvar cancer consists of anteroposterior (AP) and posteroanterior (PA) fields. This is the first study that reports the dosimetric comparison between the AP-PA techniques and the new 3D advanced conformal technique (3D-ACT) based on the multiplicity of treatment fields in patients with squamous cell cancer of the vulva in the postoperative setting. Material and Methods: This comparative planning study was conducted on15 patients with vulvar carcinoma treated with adjuvant radiation therapy at the National Institute of Oncology in Rabat, Morocco. Three treatment plans were performed, corresponding to three techniques, namely photons with source-skin distance inguinal supplement, modified segmental boost technique and 3D advanced conformal technique. For each plan, the dose-volume histogram was used to generate planning target volumes (total and inguinal PTV) and organs at risk (bladder, rectum, bowel and femoral heads) parameters. Results: The 95% isodose volume was significantly reduced with the advanced conformal technique (p <0.0001) without compromising the total PTV coverage (P= 0.94). This technique resulted in the best conformity and homogeneity index. The 3D-ACT decreased significantly the PTVs Dmax and Dmean (p <0.0001), and offered better homogeneity for inguinal PTV (i.e., 1.07±0.01, p <0.0001).The 3D-ACT decreased the rectum absorbed dose, V40 (volume receiving ≥40Gy), V45, and Dmaxto50.21±27.21, 22.81±10.22, and 46.56±1.11, respectively. With regard to femoral heads, the 3D-ACT decreased the Dmax and V45 in comparison to the other two techniques. Conclusion: The 3D-ACT seems to be an alternative to the AP-PA irradiation techniques in postoperative setting when IMRT is unavailable.

23 Vulvar cancer: Comparative study of novel 3D radiation therapy technique “ Advanced conformal technique ” and AP-PA irradiation techniques

Introduction The commonly used technique of vulvar cancer radiation therapy consists of antero-posterior “AP” and postero-anterior “PA” fields. This is the first study that reports dosimetric comparison between the AP-PA techniques and the new 3D radiation therapy technique “advanced conformal technique ACT” based on the multiplicity of treatment fields in patients with squamous cell cancer of the vulva in post-operative setting. Methods This is a comparative planning study of fifteen patients with vulvar carcinoma treated with adjuvant radiation therapy at the National Institute of Oncology in Rabat. Three treatment plans were performed, corresponding to three techniques; photons with source skin distance inguinal supplement, modified segmental boost technique, advanced conformal technique. For each plan, the dose-volume histogram was used to generate target volumes (total and inguinal PTV) and organs at risk OAR (bladder, rectum, bowel and femoral heads) parameters. Results The isodose 95% volume was significantly reduced with the advanced conformal technique (p 0.0001) without compromising the total PTV coverage (p: 0.94). This technique resulted in the best conformity and homogeneity index. The ACT decreased significantly the PTVs Dmax and Dmean (p 0.0001), and offered better homogeneity for inguinal PTV 1.07 ± 0.01 respectively (p 0.0001). The ACT decreased the rectum absorbed dose; V40, V45 and Dmax with 50.21 ± 27.21 22.81 ± 10.22 and 46.56 ± 1.11 respectively. Concerning femoral heads, the ACT decreased the Dmax and V45 in comparison to the both other techniques. Conclusions The ACT seems to be an alternative to the AP-PA irradiation techniques in post-operative setting when IMRT is not available.

Comparative planning and housing studies beyond taxonomy

Recent European comparative studies in the fields of housing policy and spatial planning have been dominated by taxonomical and linear approaches, and by normative calls for convergence toward systems considered more ‘mature’ or ‘advanced’. In this article, we adopt a genealogical perspective and consider those cultures that are central to the shaping of policy. We set out a long-term exploration of the intersection between spatial planning and housing policy in Portugal and focus on the Special Programme for Rehousing (Programa Especial de Realojamento, PER), a programme that has had changing roles (from a financial instrument to a core component of policies of urban regeneration) in connection with political and planning cultures changing in time and space. In this way, we provide evidence of the limited capacity of taxonomic and linear approaches to describe planning and housing systems undergoing processes of change and, conversely, show the potential of genealogical research.

Effect of continuous positive airway pressure administration during lung stereotactic ablative radiotherapy: acomparative planning study.

By increasing lung volume and decreasing respiration-induced tumour motion amplitude, administration of continuous positive airway pressure (CPAP) during stereotactic ablative radiotherapy (SABR) could allow for better sparing of the lungs and heart. In this study, we evaluated the effect of CPAP on lung volume, tumour motion amplitude and baseline shift, as well as the dosimetric impact of the strategy. Twenty patients with lung tumours referred for SABR underwent 4D-computed tomography (CT) scans with and without CPAP (CPAP/noCPAP) at two timepoints (T0/T1). First, CPAP and noCPAP scans were compared for lung volume, tumour motion amplitude, and baseline shift. Next, CPAP and noCPAP treatment plans were computed and compared for lung dose parameters (mean lung dose (MLD), lung volume receiving 20 Gy (V20Gy), 13 Gy (V13Gy), and 5 Gy (V5Gy)) and mean heart dose (MHD). On average, CPAP increased lung volume by 8.0% (p < 0.001) and 6.3% (p < 0.001) at T0 and T1, respectively, but did not change tumour motion amplitude or baseline shift. As a result, CPAP administration led to an absolute decrease in MLD, lung V20Gy, V13Gy and V5Gy of 0.1 Gy (p = 0.1), 0.4% (p = 0.03), 0.5% (p = 0.04) and 0.5% (p = 0.2), respectively, while having no significant influence on MHD. In patients referred for SABR for lung tumours, CPAP increased lung volume without modifying tumour motion or baseline shift. As aresult, CPAP allowed for aslight decrease in radiation dose to the lungs, which is unlikely to be clinically significant.

A comparative planning study for lung SABR between tri-Co-60 magnetic resonance image guided radiation therapy system and volumetric modulated arc therapy

Background and purposeTo compare the plan quality of tri-60Co magnetic-resonance image-guided radiation therapy (IGRT) to that of volumetric modulated arc therapy (VMAT) for lung stereotactic ablative radiotherapy (SABR). Materials and methodsA total of 22 patients with lung tumors located in the lower lobe were selected retrospectively. For each patient, VMAT plans with linac and intensity-modulated radiation therapy (IMRT) plans with the tri-60Co system were generated with prescription doses of 60Gy (daily dose=15Gy). For both plan types, identical CT image sets and structures were used, with the exception of planning target volumes (PTV). The PTV for VMAT was generated from the internal target volume (ITV) while the PTV for the tri-60Co system was generated from the gross tumor volume (GTV). Clinically relevant dose-volumetric parameters were calculated and analyzed. ResultsThe average PTV volumes of tri-60Co plans and VMAT plans were 10.5±12.3cc vs. 27.2±23.5cc, respectively (p<0.001). The maximum and mean doses to PTVs were 64.0±2.6Gy vs. 62.5±0.9Gy (p=0.005) and 61.4±1.7Gy vs. 60.0±0.5Gy (p<0.001), respectively. The conformity and homogeneity indices were 1.89±0.38 vs. 1.01±0.40 (p<0.001) and 0.06±0.02 vs. 0.04±0.00 (p<0.001), respectively. No considerable differences for organs at risk (OARs) were observed between tri-60Co plans and VMAT plans. In terms of target conformity, integral dose and lung mean dose, the plan quality of tri-60Co plans was inferior to that of VMAT plans when the PTV volumes of tri-60Co plans were less than 10cc. However, all treatment plans of tri-60Co system were clinically acceptable. ConclusionFor lung SABR, the quality of ITV-based VMAT plans was better than that of GTV-based tri-60Co plans especially when the PTV volumes of the tri-60Co plans were less than 10cc. If the breathing pattern of a patient is reproducible, VMAT is considered the optimal option for lung SABR, otherwise the tri-60Co IGRT should be considered due to the ability to monitor tumor motion during treatment.

Direction Modulated Brachytherapy for Treatment of Cervical Cancer. II: Comparative Planning Study With Intracavitary and Intracavitary–Interstitial Techniques

To perform a comprehensive comparative planning study evaluating the utility of the proposed direction modulated brachytherapy (DMBT) tandem applicator against standard applicators, in the setting of image guided adaptive brachytherapy of cervical cancer. A detailed conceptual article was published in 2014. The proposed DMBT tandem applicator has 6 peripheral grooves of 1.3-mm width, along a 5.4-mm-thick nonmagnetic tungsten alloy rod of density 18.0g/cm(3), capable of generating directional dose profiles. We performed a comparative planning study with 45 cervical cancer patients enrolled consecutively in the prospective observational EMBRACE study. In all patients, MRI-based planning was performed while utilizing various tandem-ring (27 patients) and tandem-ring-needles (18 patients) applicators, in accordance with the Groupe Européen de Curiethérapie-European Society for Radiotherapy and Oncology recommendations. For unbiased comparisons, all cases were replanned with an in-house-developed inverse optimization code while enforcing a uniform set of constraints that are reflective of the clinical practice. All plans were normalized to the same high-risk clinical target volume D90 values achieved in the original clinical plans. In general, if the standard tandem was replaced with the DMBT tandem while maintaining all other planning conditions the same, there was consistent improvement in the plan quality. For example, among the 18 tandem-ring-needles cases, the average D2cm(3) reductions achieved were -2.48%±11.03%, -4.45%±5.24%, and -5.66%±6.43% for the bladder, rectum, and sigmoid, respectively. An opportunity may also exist in avoiding use of needles altogether for when the total number of needles required is small (approximately 2 to 3 needles or less), if DMBT tandem is used. Integrating the novel DMBT tandem onto both intracavitary and intracavitary-interstitial applicator assembly enabled consistent improvement in the sparing of the OARs, over a standard "single-channel" tandem, though individual variations in benefit were considerable. Although at an early stage of development, the DMBT concept design is demonstrated to be useful and pragmatic for potential clinical translation.

SU‐F‐T‐27: A Comparative Case Study Among Four Modalities for the Superficial Treatment of Squamous Cell Carcinoma

Purpose:We performed a comparative planning study among High Dose Rate (HDR) brachytherapy, superficial electrons, Volume Modulated Arc Therapy (VMAT), and Helical IMRT (Tomotherapy) for squamous cell carcinoma of the abdominal wall with consideration for the underlining bowel.Methods:A 69‐year old female presented with squamous cell carcinoma protruding 8mm beyond the anterior skin surface of the midabdomen was considered for treatment. The patient had a ventral hernia which resulted in the reduction of the abdominal wall thickness and the adjacent small bowel being the dose limiting structure. Four plans were generated using different treatment modalities: a) an enface electron field (eMC, Eclipse v. 11), b) Tomotherapy (HI‐Art II v.5.0.5), c) VMAT (Acuros, Eclipse v. 11), and d) HDR using a Freiburg applicator (Oncentra v. 4.3). The following plan objectives were used for all four plans: for the CTV target, V90% ≥90% (61.8Gy2/2).For the small bowel, D0.1cc &lt; 56.2 Gy2/2 was a hard constraint and expressed as a percentage of the prescription for comparison to demonstrate the dose fall‐off achieved among the modalities.For HDR, V200% &lt;0.1cc was an additional constraint. Multiple dosimetric parameters, including those listed above, were compared among the four modalities.Results:The HDR plan showed comparable target coverage compared to the Tomotherapy plan and better coverage compared to the electron plan. Small bowel doses (D0.1cc) were lower in HDR plan compared to Tomotherapy, electron, &amp; VMAT plans (88.8%, 89.6%, 90.9%, &amp; 96.6%). Integral dose to the whole body (V5%) was much higher for HDR, VMAT, and Tomotherapy when compared to electron plan by factors of seven, eight, and ten, respectively. After reviewing all treatment modalities, the physician selected HDR owing to better control of the small bowel dose while maintaining adequate target coverage.Conclusion:This case study demonstrated HDR can successfully treat superficial lesions with superior sparing of underlying structures.

Can particle beam therapy be improved using helium ions? – a planning study focusing on pediatric patients

Aim To explore the potential of scanned helium ion beam therapy (4He) compared to proton therapy in a comparative planning study focusing on pediatric patients. This was motivated by the superior biological and physical characteristics of 4He.Material and methods For eleven neuroblastoma (NB), nine Hodgkin lymphoma (HL), five Wilms tumor (WT), five ependymoma (EP) and four Ewing sarcoma (EW) patients, treatment plans were created for protons and 4He. Dose prescription to the planning target volume (PTV) was 21 Gy [relative biological effectiveness (RBE)] (NB), 19.8 Gy (RBE) (HL), 25.2 Gy (RBE) for the WT boost volume and 54 Gy (RBE) for EP and EW patients. A pencil beam algorithm for protons (constant RBE = 1.1) and 4He was implemented in the treatment planning system Hyperion. For 4He the relative biological effectiveness (RBE) was calculated with a ‘zonal’ model based on different linear energy transfer regions.Results Target constraints were fulfilled for all indications. For NB patients differences for kidneys and liver were observed for all dose-volume areas, except the high-dose volume. The body volume receiving up to 12.6 Gy (RBE) was reduced by up to 10% with 4He. For WT patients the mean and high-dose volume for the liver was improved when using 4He. For EP normal tissue dose was reduced using 4He with 12.7% of the voxels receiving higher doses using protons. For HL and EW sarcoma patients the combination of large PTV volumes with the position of the organs at risk (OARs) obliterated the differences between the two particle species, while patients with the heart close to the PTV could benefit from 4He.Conclusion Treatment plan quality improved with 4He compared to proton plans, but advantages in OAR sparing were depending on indication and tumor geometries. These first results of scanned 4He therapy motivate comprehensive research on 4He, including acquisition of experimental data to improve modeling of 4He.

Multicriteria optimization enables less experienced planners to efficiently produce high quality treatment plans in head and neck cancer radiotherapy.

ObjectivesTo demonstrate that novice dosimetry planners efficiently create clinically acceptable IMRT plans for head and neck cancer (HNC) patients using a commercially available multicriteria optimization (MCO) system.MethodsTwenty HNC patients were enrolled in this in-silico comparative planning study. Per patient, novice planners with less experience in dosimetry planning created an IMRT plan using an MCO system (RayStation). Furthermore, a conventionally planned clinical IMRT plan was available (Pinnacle3). All conventional IMRT and MCO-plans were blind-rated by two expert radiation-oncologists in HNC, using a 5-point scale (1–5 with 5 the highest score) assessment form comprising 10 questions. Additionally, plan quality was reported in terms of planning time, dosimetric and normal tissue complication probability (NTCP) comparisons. Inter-rater reliability was derived using the intra-class correlation coefficient (ICC).ResultsIn total, the radiation-oncologists rated 800 items on plan quality. The overall plan score indicated no differences between both planning techniques (conventional IMRT: 3.8 ± 1.2 vs. MCO: 3.6 ± 1.1, p = 0.29). The inter-rater reliability of all ratings was 0.65 (95% CI: 0.57–0.71), indicating substantial agreement between the radiation-oncologists. In 93% of cases, the scoring difference of the conventional IMRT and MCO-plans was one point or less. Furthermore, MCO-plans led to slightly higher dose uniformity in the therapeutic planning target volume, to a lower integral body dose (13.9 ± 4.5 Gy vs. 12.9 ± 4.0 Gy, p < 0.001), and to reduced dose to the contra-lateral parotid gland (28.1 ± 11.8 Gy vs. 23.0 ± 11.2 Gy, p < 0.002). Consequently, NTCP estimates for xerostomia reduced by 8.4 ± 7.4% (p < 0.003). The hands-on time of the conventional IMRT planning was approximately 205 min. The time to create an MCO-plan was on average 43 ± 12 min.ConclusionsMCO planning enables novice treatment planners to create high quality IMRT plans for HNC patients. Plans were created with vastly reduced planning times, requiring less resources and a short learning curve.

Particle therapy for non-small cell lung tumors: where do we stand? A systematic review of the literature.

This review article provides a systematic overview of the currently available evidence on the clinical effectiveness of particle therapy for the treatment of non-small cell lung cancer and summarizes findings of in silico comparative planning studies. Furthermore, technical issues and dosimetric uncertainties with respect to thoracic particle therapy are discussed.