Target Volume Delineation In Radiotherapy Research Articles

PATTERNS OF RADIOTHERAPY PRACTICE FOR FUNCTIONING PITUITARY TUMOURS - A SURVEY OF UK CENTRES

Abstract AIMS Pituitary adenomas are benign tumours that are classified as functioning or non-functioning based on the production of excess pituitary hormones. Functioning adenomas (FA) typically present as hypersecretory syndromes including acromegaly and Cushing’s disease. In FA, radiotherapy is used when surgery fails to achieve hormone normalisation and/or when medical treatment does not control hormone excess. In the absence of prospective studies that clearly define the optimal radiotherapy technique in FA, it is expected that there will be variability in practice. A survey of UK neuro-oncology centres was undertaken, aiming to establish the extent of this variability in FA. METHOD A survey was distributed electronically to 20 neuro-oncology departments across the UK. Data were collected on patient numbers, radiotherapy indications, techniques, dosing, and target volume delineation. RESULTS Responses were received from eight centres (40% response rate), treating a total of approximately 32 FA per annum. There was variability in techniques employed to treat FA. While four centres treated most FA with IMRT, two treat most with stereotactic radiosurgery (SRS), and two with fractionated stereotactic radiotherapy (fSRT). The most common dose used for IMRT treatment was 45Gy in 25 fractions (n=7), with 50.4Gy in 28 fractions, 50Gy in 30 fractions and 54Gy in 30 fractions also reported. Use of margins around residual disease (n=5) and inclusion of involved cavernous sinuses and surgical tract (n=3) within clinical target volumes also varied. Most centres (n=7) would agree to a change in target volume delineation practices for the purpose of a clinical trial in FA. CONCLUSION This survey found that there is variability in radiotherapy dosing, technique, and target volume delineation practices for radiotherapy to FA across the UK. All centres but one would accept changes in their practice within the context of a prospective clinical trial of radiotherapy for FA.

Clinical target volume (CTV) automatic delineation using deep learning network for cervical cancer radiotherapy: A study with external validation.

To explore the accuracy and feasibility of a proposed deep learning (DL) algorithm for clinical target volume (CTV) delineation in cervical cancer radiotherapy and evaluate whether it can perform well in external cervical cancer and endometrial cancer cases for generalization validation. A total of 332 patients were enrolled in this study. A state-of-the-art network called ResCANet, which added the cascademulti-scale convolution in the skip connections to eliminate semantic differences between different feature layers based on ResNet-UNet. The atrous spatial pyramid pooling in the deepest feature layer combined the semantic information of different receptive fields without losing information. A total of 236 cervical cancer cases were randomly grouped into 5-fold cross-training (n=189) and validation (n=47) cohorts. External validations were performed ina separate cohort of 54 cervical cancer and 42 endometrial cancer cases. The performances of the proposed network were evaluated by dice similarity coefficient (DSC), sensitivity (SEN), positive predictive value (PPV), 95% Hausdorff distance (95HD), and oncologist clinical score when comparing them with manual delineation in validation cohorts. In internal validation cohorts, the mean DSC, SEN, PPV, 95HD for ResCANet achieved 74.8%, 81.5%, 73.5%, and 10.5mm. In external independent validation cohorts, ResCANet achieved 73.4%, 72.9%, 75.3%, 12.5mm for cervical cancer cases and 77.1%, 81.1%, 75.5%, 10.3mm for endometrial cancer cases, respectively. The clinical assessment score showed that minor and no revisions (delineation time was shortened to within 30min) accountedforabout 85% of all cases in DL-aided automatic delineation. We demonstrated the problem of model generalizability for DL-based automatic delineation. The proposed network can improve the performance of automatic delineation for cervical cancer and shorten manual delineation time at no expense to quality. The network showed excellent clinical viability, which can also be even generalized for endometrial cancer with excellent performance.

Preferred Imaging for Target Volume Delineation for Radiotherapy of Recurrent Glioblastoma: A Literature Review of the Available Evidence.

Recurrence in glioblastoma lacks a standardized treatment, prompting an exploration of re-irradiation's efficacy. A comprehensive systematic review from January 2005 to May 2023 assessed the role of MRI sequences in recurrent glioblastoma re-irradiation. The search criteria, employing MeSH terms, targeted English-language, peer-reviewed articles. The inclusion criteria comprised both retrospective and prospective studies, excluding certain types and populations for specificity. The PICO methodology guided data extraction, and the statistical analysis employed Chi-squared tests via MedCalc v22.009. Out of the 355 identified studies, 81 met the criteria, involving 3280 patients across 65 retrospective and 16 prospective studies. The key findings indicate diverse treatment modalities, with linac-based photons predominating. The median age at re-irradiation was 54 years, and the median time interval between radiation courses was 15.5 months. Contrast-enhanced T1-weighted sequences were favored for target delineation, with PET-imaging used in fewer studies. Re-irradiation was generally well tolerated (median G3 adverse events: 3.5%). The clinical outcomes varied, with a median 1-year local control rate of 61% and a median overall survival of 11 months. No significant differences were noted in the G3 toxicity and clinical outcomes based on the MRI sequence preference or PET-based delineation. In the setting of recurrent glioblastoma, contrast-enhanced T1-weighted sequences were preferred for target delineation, allowing clinicians to deliver a safe and effective therapeutic option; amino acid PET imaging may represent a useful device to discriminate radionecrosis from recurrent disease. Future investigations, including the ongoing GLIAA, NOA-10, ARO 2013/1 trial, will aim to refine approaches and standardize methodologies for improved outcomes in recurrent glioblastoma re-irradiation.

Towards deep-learning (DL) based fully automated target delineation for rectal cancer neoadjuvant radiotherapy using a divide-and-conquer strategy: a study with multicenter blind and randomized validation

PurposeManual clinical target volume (CTV) and gross tumor volume (GTV) delineation for rectal cancer neoadjuvant radiotherapy is pivotal but labor-intensive. This study aims to propose a deep learning (DL)-based workflow towards fully automated clinical target volume (CTV) and gross tumor volume (GTV) delineation for rectal cancer neoadjuvant radiotherapy.Materials & methodsWe retrospectively included 141 patients with Stage II-III mid-low rectal cancer and randomly grouped them into training (n = 121) and testing (n = 20) cohorts. We adopted a divide-and-conquer strategy to address CTV and GTV segmentation using two separate DL models with DpuUnet as backend-one model for CTV segmentation in the CT domain, and the other for GTV in the MRI domain. The workflow was validated using a three-level multicenter-involved blind and randomized evaluation scheme. Dice similarity coefficient (DSC) and 95th percentile Hausdorff distance (95HD) metrics were calculated in Level 1, four-grade expert scoring was performed in Level 2, and head-to-head Turing test in Level 3.ResultsFor the DL-based CTV contours over the testing cohort, the DSC and 95HD (mean ± SD) were 0.85 ± 0.06 and 7.75 ± 6.42 mm respectively, and 96.4% cases achieved clinical viable scores (≥ 2). The positive rate in the Turing test was 52.3%. For GTV, the DSC and 95HD were 0.87 ± 0.07 and 4.07 ± 1.67 mm respectively, and 100% of the DL-based contours achieved clinical viable scores (≥ 2). The positive rate in the Turing test was 52.0%.ConclusionThe proposed DL-based workflow exhibited promising accuracy and excellent clinical viability towards automated CTV and GTV delineation for rectal cancer neoadjuvant radiotherapy.

Target volume delineation for radiotherapy of meningiomas: an ANOCEF consensus guideline

PurposeRadiotherapy is, with surgery, one of the main therapeutic treatment strategies for meningiomas. No prospective study has defined a consensus for the delineation of target volumes for meningioma radiotherapy. Therefore, target volume definition is mainly based on information from retrospective studies that include heterogeneous patient populations. The aim is to describe delineation guidelines for meningioma radiotherapy as an adjuvant or definitive treatment with intensity-modulated radiation therapy and stereotactic radiation therapy techniques. This guideline is based on a consensus endorsed by a multidisciplinary group of brain tumor experts, members of the Association of French-speaking Neuro-oncologists (ANOCEF).Materials and methodsA 3-step procedure was used. First, the steering group carried out a comprehensive review to identify divergent issues on meningiomas target volume delineation. Second, an 84-item web-questionnaire has been developed to precisely define meningioma target volume delineation in the most common clinical situations. Third, experts members of the ANOCEF were requested to answer. The first two rounds were completed online. A third round was carried out by videoconference to allow experts to debate and discuss the remaining uncertain questions. All questions remained in a consensus.ResultsLimits of the target volume were defined using visible landmarks on computed tomography and magnetic resonance imaging, considering the pathways of tumor extension. The purpose was to develop clear and precise recommendations on meningiomas target volumes.ConclusionNew recommendations for meningiomas delineation based on simple anatomic boundaries are proposed by the ANOCEF. Improvement in uniformity in target volume definition is expected.

PD-0653 Target volume delineation for radiotherapy of meningiomas: an ANOCEF consensus guideline.

PD-0653 Target volume delineation for radiotherapy of meningiomas: an ANOCEF consensus guideline.

The Impact of Interactive MRI-Based Radiologist Review on Radiotherapy Target Volume Delineation in Head and Neck Cancer.

Peer review of head and neck cancer radiation therapy target volumes by radiologists was introduced in our center to optimize target volume delineation. Our aim was to assess the impact of MR imaging-based radiologist peer review of head and neck radiation therapy gross tumor and nodal volumes, through qualitative and quantitative analysis. Cases undergoing radical radiation therapy with a coregistered MR imaging, between April 2019 and March 2020, were reviewed. The frequency and nature of volume changes were documented, with major changes classified as per the guidance of The Royal College of Radiologists. Volumetric alignment was assessed using the Dice similarity coefficient, Jaccard index, and Hausdorff distance. Fifty cases were reviewed between April 2019 and March 2020. The median age was 59 years (range, 29-83 years), and 72% were men. Seventy-six percent of gross tumor volumes and 41.5% of gross nodal volumes were altered, with 54.8% of gross tumor volume and 66.6% of gross nodal volume alterations classified as "major." Undercontouring of soft-tissue involvement and unidentified lymph nodes were predominant reasons for change. Radiologist review significantly altered the size of both the gross tumor volume (P = .034) and clinical target tumor volume (P = .003), but not gross nodal volume or clinical target nodal volume. The median conformity and surface distance metrics were the following: gross tumor volume Dice similarity coefficient = 0.93 (range, 0.82-0.96), Jaccard index = 0.87 (range, 0.7-0.94), Hausdorff distance = 7.45 mm (range, 5.6-11.7 mm); and gross nodular tumor volume Dice similarity coefficient = 0.95 (0.91-0.97), Jaccard index = 0.91 (0.83-0.95), and Hausdorff distance = 20.7 mm (range, 12.6-41.6). Conformity improved on gross tumor volume-to-clinical target tumor volume expansion (Dice similarity coefficient = 0.93 versus 0.95, P = .003). MR imaging-based radiologist review resulted in major changes to most radiotherapy target volumes and significant changes in volume size of both gross tumor volume and clinical target tumor volume, suggesting that this is a fundamental step in the radiotherapy workflow of patients with head and neck cancer.

Interobserver variation in clinical target volume (CTV) delineation for stereotactic radiotherapy to non-spinal bone metastases in prostate cancer: CT, MRI and PET/CT fusion

Background and purposeThe use of SBRT for the treatment of oligometastatic prostate cancer is increasing rapidly. While consensus guidelines are available for non-spinal bone metastases practice continues to vary widely. The aim of this study is to look at inter-observer variability in the contouring of prostate cancer non-spinal bone metastases with different imaging modalities. Materials and methods15 metastases from 13 patients treated at our centre were selected. 4 observers independently contoured clinical target volumes (CTV) on planning CT alone, planning CT with MRI fusion, planning CT with PET-CT fusion and planning CT with both MRI and PET-CT fusion combined. The mean inter-observer agreement on each modality was compared by measuring the delineated volume, generalized conformity index (CIgen), and the distance of the centre of mass (dCOM), calculated per metastasis and imaging modality. ResultsMean CTV volume delineated on planning CT with MRI and PET-CT fusion combined was significantly larger compared to other imaging modalities (p = 0.0001). CIgen showed marked variation between modalities with the highest agreement between planning CT + PET-CT (mean CIgen 0.55, range 0.32–0.73) and planning CT + MRI + PET-CT (mean CIgen 0.59, range 0.34–0.73). dCOM showed small variations between imaging modalities but a significantly shorter distance found on planning CT + PET-CT when compared with planning CT + PET-CT + MRI combined (p = 0.03). ConclusionsHighest consistency in CTV delineation between observers was seen with planning CT + PET-CT and planning CT + PET-CT + MRI combined.

ANOCEF Consensus Guideline on Target Volume Delineation for Meningiomas Radiotherapy

<h3>Purpose/Objective(s)</h3> Meningiomas are the most common primary intracranial tumor. They are developed at the expense of the dura, with an overall incidence which has increased over the past decade. To date, there is no published specific guideline about meningiomas target volume. No prospective study has defined a consensus for delineation in meningiomas' radiotherapy. Therefore, target volume definition is mainly based on retrospective studies, with a heterogeneous population of patients. The aim of this paper is to describe delineation guidelines for meningiomas' radiotherapy as an adjuvant or definitive treatment with Intensity Modulated Radiation Therapy (IMRT) and stereotactic radiation therapy (SRT) techniques. <h3>Materials/Methods</h3> This guideline is based on a consensus endorsed by a global multidisciplinary group of brain tumor experts' member of the ANOCEF (French neuro-oncology association). A two round modified Delphi consensus was achieved, and the consensus was adopted by the RAND/UCLA method. The third round was carried out in videoconference, in order to allow experts to debate and argue on remaining uncertain proposals. <h3>Results</h3> Twenty experts from 17 radiotherapy center participated. After 3 rounds, all the proposals resulted in a consensus. The ANOCEF guideline committee proposed to perform an unenhanced planning CT scan, merged with a post-contrast MRI obtained at the time of radiotherapy and preoperative MRI in case of adjuvant treatment. GTV is defined by T1 contrast-enhancing lesion, thickened meninges, and directly invaded bone. For IMRT, the CTV include: Grade I: No margin around the GTV. Grade II: Margin of 5mm to expand GTV in normal brain tissue, hyperostosis, along the unthickened meninges and venous sinuses if the GTV is coming into contact. Grade III: Margin of 10mm to expand GTV in normal brain tissue, hyperostosis, along the unthickened meninges, and optic or cranial nerves in contact with GTV. In case of bone invasion, a margin of 5 or 10mm in the healthy bone around the GTV is recommended, for grade II or III respectively. Otherwise, it is considered as an anatomical barrier and does not need to be included in the target volume. In case of post-operative radiotherapy, no additional margin is required for CTV for grade I around tumor bed. A 5 and 10mm margin is required for grade II and III. The cranial flap should only be included in the CTV only over 5 or 10mm for grades II or III, in case of initially invaded bone. The drill holes and osteotomy areas should be included if they come into contact with target volume. SRT is not recommended for grades II and III, excluding relapse situation. CTV corresponds to GTV without additional margin. <h3>Conclusion</h3> The current consensus provides a detailed delineation guideline for meningioma, suggesting smaller margins than the major studies published to date.

The Impact of Chemoradiotherapy on Biophysical Properties of Glioblastoma Utilizing a Novel Murine Model

<h3>Purpose/Objective(s)</h3> Glioblastoma, historically viewed as a single disease entity, is now known to be composed of various subtypes. Here, we present our work evaluating the effects of chemoradiotherapy on cellular biophysical processes using a novel murine model of glioblastoma developed by our group. <h3>Materials/Methods</h3> Primary tumor cell lines were established from a murine glioma model generated from a synthetic DNA transposon system delivered oncogenic drivers SV40-LgTA and either NRASV12 or PDGFB. We have previously shown these cell lines, termed NRAS and PDGF, respectively, recapitulate the mesenchymal and proneural tumor subtypes. Treatment was administered with temozolomide (TMZ) to a maximum of 100µM, single fraction radiation therapy (RT) to a maximum of 10 Gy, or both. Cells were stained with Hoechst dye, imaged with an epifluorescence microscope with 10X objective lens, and counted with an image segmentation algorithm daily for 4 days to estimate cell survival and proliferation. On post-treatment day 4, surviving cells were plated on Matrigel coated 9.3kPa polyacrylamide gel and imaged with an inverted, transmitted light microscope with 10X objective lens every 5 minutes for 4 hours. Single cell mean squared displacement (MSD) was measured from time lapse images via an image segmentation algorithm. The random motility coefficient (µ) was calculated by the relationship MSD(t) = 4µt, where t is time. Data was compared via the Kruskal-Wallis test with Bonferroni correction for multiple comparisons when appropriate. <h3>Results</h3> There was no significant difference in cellular death or proliferation between treatment and control arms for the PDGF cell lines. In the NRAS cell lines, TMZ alone did not induce cell death while RT (P < 0.01) and combined modality therapy (P < 0.01) yielded cellular killing in a dose dependent manner. Furthermore, RT-treated NRAS cells proliferated more slowly than non-treated cells (0.05 vs. 0.20 hr-1, P=0.04). Control NRAS cell lines migrated faster than their PDGF counterparts at baseline (3.82 vs. 0.73 µm2/hr, P<1E-5). Within each cell line, the use of combined modality therapy significantly reduced cellular motility (PDGF: 0.73 vs. 0.21 µm2/hr, P=0.008; NRAS: 0.65 vs. 3.82 µm2/hr, P<1E-5). RT monotherapy additionally reduced motility in NRAS cell lines (1.07 vs. 3.82 µm2/hr, P<1E-5) while no difference was observed in PDGF cells. TMZ monotherapy did not affect motility within either cell line. <h3>Conclusion</h3> We evaluated biophysical properties of a novel murine glioma model utilizing oncogenic drivers overexpressing NRASV12 or PDGFB which we have previously shown recapitulates the mesenchymal and proneural subtypes of human glioblastoma, respectively. Here, we observed phenotypic differences in cellular migration following RT and TMZ regimens which could have subtype-specific ramifications for radiotherapy dose and target volume delineation.

The Impact of Real-Time MRI Radiology-Based Peer Review on Head and Neck Radiotherapy Target Volume Delineation

<h3>Purpose/Objective(s)</h3> As part of the introduction of planning MRI into the Radiotherapy (RT) workflow of Head Neck (HN) patients, we included HN radiology peer review to optimize target delineation. We hypothesized that this would result in significant target volume changes. <h3>Materials/Methods</h3> Radical cases with a fused diagnostic or RT planning MRI were prospectively identified. Gross Tumor Volumes (GTV) defined by HN oncologists were reviewed and modified, where indicated, by a HN radiologist and labelled (GTVonc, GTVrad). Following peer review, clinical target volumes (CTVonc, CTVrad) were created by adding a 10mm isotropic margin to each GTV-tumor (GTVT) or GTV-nodal (GTVN), then edited off anatomical barriers. The rate of changes, anatomical patterns of change, and factors associated with volume discrepancy were prospectively recorded. Amended and original volumes were compared using Dice Similarity Coefficient (DSC), Jaccard Index (JI) and Hausdorff Distance (HD). ‘Major' changes were defined as: editing of GTV by ≥10mm, editing to avoid a GTV geographical miss, inclusion of suspicious nodes within the high-dose CTV, and retrospectively assessed. <h3>Results</h3> 50 cases were reviewed between April 2019 and March 2020; 76% of GTVTs (38/50) and 42.8% of GTVNs (18/42) were modified. 31 GTVTs and 10 GTVNs were available for conformity assessment. Volume changes and conformity results are described in Table 1. Despite high conformity indices, 54.8% of GTVT (17/31) and 70% of GTVN (7/10) changes were considered ‘major'. The most frequent anatomical patterns of change were: GTVT soft tissue changes (92.1%; 35/38), and GTVN identification of additional nodes (83.3%; 15/18). The commonest qualitative reason for modifications to any GTV (n=41) were: imaging misinterpretation (75.6%, 31), changes made after collaborative discussion (17%, 7), and use of diffusion-weighted sequences (17%, 7). <h3>Conclusion</h3> Small, albeit statistically significant, differences in volume size were found on both GTVT and CTVT. While conformity index measures such as DSC were acceptable, the modifications were categorized as a "major" qualitative change in two thirds of patients. This highlights the importance of expert HN radiologist peer review of target volumes.

ReIGNITE RT Boost: An International Study Testing the Feasibility, Accuracy and Reliability of Using Restriction Spectrum Imaging (RSI) MRI to Guide Radiotherapy Target Volume Delineation for Prostate Cancer Tumor Boost

<h3>Purpose/Objective(s)</h3> Recently the FLAME clinical trial showed adding a radiation boost to the visible tumor improves prostate cancer control without additional toxicity. In FLAME, a radiologist assisted in each tumor delineation. Even for radiologists, there is substantial dependence on reader experience for prostate MRI. Radiation oncologists' ability to reliably identify prostate tumors is critical to wide adoption and patients benefitting from tumor radiotherapy boost. We have developed a quantitative diffusion MRI metric for prostate cancer based on the restriction spectrum imaging (RSI) framework, called the RSI restriction score (RSI_rs). RSI_rs has been shown to improve accuracy over guideline-recommended standard ADC maps. RSI_rs maps can be overlaid on conventional T2-weighted MRI sequences and used to identify prostate cancer. We hypothesize that contouring on RSI_rs maps will improve the accuracy and reliability of prostate tumor delineation. <h3>Materials/Methods</h3> Radiation oncologists (participants) from multiple institutions contoured prostate tumors on 20 patient cases. An expert radiologist contoured each tumor to establish ground truth. Participants were either board certified or a resident who had completed a clinical genitourinary cancer rotation. Participants were provided the patient's age, PSA level, biopsy result and radiologist's report (e.g., "PI-RADS 5 lesion in right lateral peripheral zone at the base"). Participants delineated volumes on either standard MRI alone (50% of cases; included T2-weighted, DWI, ADC) or standard MRI with RSI_rs map. Accuracy was quantified by comparing to the expert volume by distance to agreement, Dice coefficient, and Jaccard coefficient. Reliability was measured as variation across participants by the Volume Ratio (VR) method. <h3>Results</h3> In this interim analysis of an ongoing study, 126 target volumes have been analyzed from 6 participants. Comparing participant and expert volumes, use of RSI_rs maps significantly improved the mean distance to agreement (3.87mm vs. 1.68mm, p<0.01), Dice coefficient (0.45 vs. 0.65, p<0.001), and Jaccard coefficient (0.32 vs. 0.50, p<0.001). Target volume variability was also significantly improved; VR was reduced from 19.23 to 5.90 (p<0.05). Notably, there were 9 complete misses when participants contoured on standard MRI alone but no misses when RSI_rs maps were provided. 63 global participants have been enrolled in this study and additional data collection and analysis are in process. <h3>Conclusion</h3> The addition of RSI_rs maps to standard MRI improves the reliability and accuracy of target delineation for prostate tumor boost. RSI_rs maps have the potential to increase the feasibility of widely implementing the benefits of focal tumor boost for patients undergoing prostate radiotherapy.

Variation in clinical target volume delineation in postoperative radiotherapy for biliary tract cancer.

We aimed to evaluate the inter-clinician variability in the clinical target volume (CTV) for postoperative radiotherapy (PORT) for biliary tract cancer (BTC) including extrahepatic bile duct cancer (EBDC) and gallbladder cancer (GBC). Nine experienced radiation oncologists delineated PORT CTVs for distal EBDC (pT2N1), proximal EBDC (pT2bN1) and GBC (pT2bN1) patients. The expectation maximization algorithm for Simultaneous Truth and Performance Level Estimation (STAPLE) was used to quantify expert agreements. We generated volumes with a confidence level of 80% to compare the maximum distance to each CTV in six directions. The degree of agreement was moderate; overall kappa values were 0.573 for distal EBDC, 0.513 for proximal EBDC, and 0.511 for GBC. In the distal EBDC, a larger variation was noted in the right, post, and inferior direction. In the proximal EBDC, all borders except the right and left direction showed a larger variation. In the GBC, a larger variation was found in the anterior, posterior, and inferior direction. The posterior and inferior borders were the common area having discrepancies, associated with the insufficient coverage of the paraaortic node. A consensus guideline is needed to reduce inter-clinician variability in the CTVs and adequate coverage of regional lymph node area.

FAPI-PET/CT Improves Diagnostic Staging and Radiotherapy Planning of Adenoid Cystic Carcinomas ― Imaging Analysis and Histological Validation

Adenoid cystic carcinomas (ACCs) are rare epithelial tumors mostly situated in the head and neck region and characterized by infiltrative growth. The tumor stroma of ACCs includes cancer-associated fibroblasts (CAFs) expressing Fibroblast Activation Protein (FAP), a new target for positron emission tomography (PET) imaging. Here we describe the value of PET/ computed tomography (PET/CT) imaging using 68Ga-labelled FAP-Inhibitors (68Ga-FAPI-PET/CT) and their clinical potential for staging and radiotherapy planning in 12 ACC patients (7 primary, 5 recurrent).Patients underwent contrast enhanced CT (ceCT) and magnetic resonance imaging (ceMRI) before 68Ga-FAPI - PET/CT. PET-scans were acquired 10, 60 and 180 minutes after administration of 150-250 MBq of 68Ga-labelled FAPI tracers. SUVmax and SUVmean values of ACCs and healthy organs were obtained using a 60% of maximum iso-contour. FAP and alpha smooth muscle actin (α-SMA) immunohistochemistry was performed in 13 cases (3 with and 10 without 68Ga FAPI-PET/CT). Staging and radiotherapy planning based on 68Ga-FAPI-PET/CT versus ceCT/MRI alone were compared.We observed elevated tracer uptake in all ACCs. Immunohistochemistry showed FAP-expressing CAFs in the tumor. Compared to conventional staging, 68Ga-FAPI-PET/CT led to upstaging in 2/12 patients and to detection of additional metastases in 3 patients, thus in total 42% of patients had their staging altered. Moreover, 68Ga-FAPI PET improved the accuracy of target volume delineation for radiotherapy, as compared to CT and MRI.68Ga-FAPI-PET/CT is a promising imaging modality for ACC, providing additional information for staging and leading to altered radiotherapy planning compared to CT and MRI.

FDG-PET/CT and MR imaging for target volume delineation in rectal cancer radiotherapy treatment planning: a systematic review

AbstractAim:The aim of this systematic review was to synthesise and summarise evidence surrounding the clinical use of fluoro-2-deoxy-d-glucose positron emission tomography/computed tomography (FDG-PET/CT) and magnetic resonance imaging (MRI) for target volume delineation (TVD) in rectal cancer radiotherapy planning.Methods:PubMed, EMBASE, Cochrane library, CINAHL, Web of Science and Scopus databases and other sources were systematically queried using keywords and relevant synonyms. Eligible full-text studies were assessed for methodological quality using the QUADAS-2 tool.Results:Eight of the 1448 studies identified met the inclusion criteria. Findings showed that MRI significantly delineate larger tumour volumes (TVs) than FDG-PET/CT while diffusion-weighted magnetic resonance imaging (DW-MRI) defined smaller gross tumour volumes (GTVs) compared to T2 weighted-Magnetic Resonance Image. CT-based GTVs were found to be larger compared to FDG-PET/CT. FDG-PET/CT also identified new lesions in 15–17% patients and TVs extending outside the routinely used clinical standard CT TV in 29–83% patients. Between observers, delineated volumes were similar and consistent between MRI sequences, whereas interobserver agreement was significantly improved with FDG-PET/CT than CT.Conclusion:FDG-PET/CT and DW-MRI appear to delineate smaller rectal TVs and show improved interobserver variability. Overall, this study provides valuable insights into the amount of attention in the research literature that has been paid to imaging for TVD in rectal cancer.

Contouring Collaborative for Consensus in Radiation Oncology (C3RO): An International Crowdsourcing Challenge to Improve Radiotherapy Contour Delineation

Contour variation has been correlated with inferior disease control and increased toxicity. 1 Segedin B Petric P. Uncertainties in target volume delineation in radiotherapy - are they relevant and what can we do about them?. Radiol Oncol. 2016; 50: 254-262 Crossref PubMed Scopus (55) Google Scholar While automated algorithms could decrease variability and improve quality, development has been limited by the availability of large multi-segmented datasets. 2 Mak RH Endres MG Paik JH Sergeev RA Aerts H Williams CL et al. Use of Crowd Innovation to Develop an Artificial Intelligence-Based Solution for Radiation Therapy Targeting. JAMA Oncol. 2019; 5: 654-661 Crossref PubMed Scopus (32) Google Scholar This project aims to conduct a crowdsourced challenge informed by behavioral economics to engage radiation oncologists worldwide in cloud-based contouring. We hypothesize that recruitment strategies and incentives will vary by practice setting. We hypothesize that, among physicians, high volume and specialization will be associated with greater similarity to the consensus contour.

The Impact of Different Simulation Modalities on Target Volume Delineation in Breast-Conserving Radiotherapy.

PurposeIn the management of breast-conserving radiotherapy, computed tomography (CT) simulation is now commonly used to identify tumor bed while has difficulties defining precisely. We aimed to evaluate the impact of magnetic resonance (MR) and CT simulation on defining the postoperative tumor bed for breast-conserving radiotherapy in patients without the aid of surgical clips.MethodsFrom August 2018 to March 2019, twenty patients with T1-2N0M0 breast cancer at our institution were enrolled. All the patients underwent breast-conserving surgery without implantation of surgical clips and were prepared to receive radiotherapy. CT and MR images were acquired on the same day for each patient. Three radiation oncologists independently assigned cavity visualization score (CVS) and delineated the tumor bed based on first the CT then the MR images. Interobserver variability was assessed by volumes, generalized conformity index (CIgen) and the distance between the centers of mass (dCOM). Differences in mean values for parameters were tested by paired t-test or one-way analysis of variance, as appropriate.ResultsFirst, the mean volumes of tumor bed derived from MR were 22%, 27% and 21% smaller than those based on CT images for each observer. In addition, the mean CIgen was significantly superior, and dCOM was smaller for MR than for CT images (CIgen: 0.59 vs 0.52, P= 0.008; dCOM: 1.30 cm vs 1.39 cm, P= 0.095). Moreover, the mean CVS was 3.23±1.34 and 2.43±0.92 for MR and CT images, respectively (P= 0.035). Last, a positive association was observed between the CVS and CIgen for both modalities (P< 0.01).ConclusionCompared to CT, MR can improve the visualization of changes in the postoperative tumor bed. In addition, MR can yield a more precise definition of the tumor bed and improve the consistency of tumor bed contouring in patients without surgical clips.

Interobserver variability in target volume delineation in definitive radiotherapy for thoracic esophageal cancer: a multi-center study from China

PurposeTo investigate the interobserver variability (IOV) in target volume delineation of definitive radiotherapy for thoracic esophageal cancer (TEC) among cancer centers in China, and ultimately improve contouring consistency as much as possible to lay the foundation for multi-center prospective studies.MethodsSixteen cancer centers throughout China participated in this study. In Phase 1, three suitable cases with upper, middle, and lower TEC were chosen, and participants were asked to contour a group of gross tumor volume (GTV-T), nodal gross tumor volume (GTV-N) and clinical target volume (CTV) for each case based on their routine experience. In Phase 2, the same clinicians were instructed to follow a contouring protocol to re-contour another group of target volume. The variation of the target volume was analyzed and quantified using dice similarity coefficient (DSC).ResultsSixteen clinicians provided routine volumes, whereas ten provided both routine and protocol volumes for each case. The IOV of routine GTV-N was the most striking in all cases, with the smallest DSC of 0.37 (95% CI 0.32–0.42), followed by CTV, whereas GTV-T showed high consistency. After following the protocol, the smallest DSC of GTV-N was improved to 0.64 (95% CI 0.45–0.83, P = 0.005) but the DSC of GTV-T and CTV remained constant in most cases.ConclusionVariability in target volume delineation was observed, but it could be significantly reduced and controlled using mandatory interventions.

68Ga-FAPI-PET/CT improves diagnostic staging and radiotherapy planning of adenoid cystic carcinomas – Imaging analysis and histological validation

BackgroundAdenoid cystic carcinomas (ACCs) are rare epithelial tumors mostly situated in the head and neck region and characterized by infiltrative growth. The tumor stroma of ACCs includes cancer-associated fibroblasts (CAFs) expressing Fibroblast Activation Protein (FAP), a new target for positron emission tomography (PET) imaging. Here we describe the value of PET/ computed tomography (PET/CT) imaging using 68Ga-labelled FAP-Inhibitors (68Ga-FAPI-PET/CT) and their clinical potential for staging and radiotherapy planning in 12 ACC patients (7 primary, 5 recurrent). Patients and methodsPatients underwent contrast enhanced staging CT (ceCT) and magnetic resonance imaging (ceMRI) before 68Ga-FAPI - PET/CT. PET-scans were acquired 10, 60 and 180 minutes after administration of 150–250 MBq of 68Ga-labelled FAPI tracers. SUVmax and SUVmean values of ACCs and healthy organs were obtained using a 60% of maximum iso-contour. FAP and alpha smooth muscle actin (α-SMA) immunohistochemistry was performed in 13 cases (3 with and 10 without 68Ga FAPI-PET/CT). Staging and radiotherapy planning based on 68Ga-FAPI-PET/CT versus ceCT/MRI alone were compared. ResultsWe observed elevated tracer uptake in all ACCs. Immunohistochemistry showed FAP-expressing CAFs in the tumor. Compared to conventional staging, 68Ga-FAPI-PET/CT led to upstaging in 2/12 patients and to detection of additional metastases in 3 patients, thus in total 42% of patients had their staging altered. Moreover, 68Ga-FAPI PET improved the accuracy of target volume delineation for radiotherapy, as compared to CT and MRI. Conclusion68Ga-FAPI-PET/CT is a promising imaging modality for ACC, increasing the accuracy of staging exams and radiotherapy planning volumes, as compared conventional to CT and MRI.

A national cross-sectional survey investigating the use of endoscopic ultrasound in the diagnosis and treatment of oesophageal cancer in the UK

To evaluate variation in the pre-pandemic use of endoscopic ultrasound (EUS) for oesophageal cancer diagnosis and treatment planning up to 2019, and which factors contributed to this. A UK-wide online survey of oesophagogastric multidisciplinary team lead clinicians was undertaken to determine perceptions towards, and the use of, EUS to aid staging and treatment planning in oesophageal cancer. Thirty-five responses were received, representing 97 UK National Health Service Trusts/Health Boards. A majority of centres (n=21, 60%) did not have formal written guidance for EUS use. Although all respondents had access to EUS, a perceived lack of utility (n=7) and concerns about delaying treatment start dates (n=8) each restricted EUS use for a fifth of respondents. For most centres (n=24, 68.6%), EUS use is case-specific, whereas for 10 (28.6%) EUS is used for all patients with potentially curable disease. A majority of centres use diagnostic positron-emission tomography for radiotherapy target volume delineation (TVD), whereas 22 (62.9%) use EUS. The factors contributing to decisions to use EUS for staging, TVD and surgical planning varied between centres. The proportion of centre respondents who would request EUS in each of six clinical scenarios varied considerably. There were substantial differences in the patient and disease characteristics that are perceived to be indications for EUS use for both staging and treatment planning. Research to clarify in which patients with oesophageal cancer EUS affords benefit is required, as is urgent standardisation of its role in the diagnostic pathway.