Radiotherapy Target Volume Research Articles

Prostate-Specific Membrane Antigen Positron Emission Tomography/Computed Tomography-Based Clinical Target Volume Delineation Guideline for Postprostatectomy Salvage Radiation Therapy: The PERYTON Guideline

Prostate-specific membrane antigen positron emission tomography/computed tomography (PSMA PET/CT) scan is the standard imaging procedure for biochemical recurrent prostate cancer postprostatectomy because of its high detection rate at low serum prostate-specific antigen levels. However, existing guidelines for clinical target volume (CTV) in prostate bed salvage external beam radiation therapy (sEBRT) are primarily based on experience-based clinical consensus and have been validated using conventional imaging modalities. Therefore, this study aimed to optimize CTV definition in sEBRT by using PSMA PET/CT-detected local recurrences (LRs). Patients with suspected LR on PSMA PET/CT postprostatectomy were retrospectively enrolled in 9 Dutch centers. Anonymized scans were centrally reviewed by an expert nuclear medicine physician. Each boundary of the CTV guideline from the Groupe Francophone de Radiothérapie en Urologie (GFRU) was evaluated and adapted to improve the accuracy and coverage of the area at risk of LR (CTV) on PSMA PET/CT. The proposed CTV adaptation was discussed with the radiation oncologists of the participating centers, and final consensus was reached. To assess reproducibility, the participating centers were asked to delineate 3 new cases according to the new PERYTON-CTV, and the submitted contours were evaluated using the Dice similarity coefficient (DSC). After central review, 93 LRs were identified on 83 PSMA PET/CTs. The proposed CTV definition improved the coverage of PSMA PET/CT-detected LRs from 67% to 96% compared with the GFRU-CTV, while reducing the GFRU-CTV by 25%. The new CTV was highly reproducible, with a mean DSC of 0.82 (range, 0.81-0.83). This study contributes to the optimization of CTV definition in postprostatectomy sEBRT by using the pattern of LR detected on PSMA PET/CT. The PERYTON-CTV is highly reproducible across the participating centers and ensures coverage of 96% LRs while reducing the GFRU-CTV by 25%.

A Survey on Automatic Delineation of Radiotherapy Target Volume based on Machine Learning

ABSTRACTRadiotherapy is one of the main treatment methods for cancer, and the delineation of the radiotherapy target area is the basis and premise of precise treatment. Artificial intelligence technology represented by machine learning has done a lot of research in this area, improving the accuracy and efficiency of target delineation. This article will review the applications and research of machine learning in medical image matching, normal organ delineation and treatment target delineation according to the procudures of doctors to delineate the target volume, and give an outlook on the development prospects.

A comparison of loco-regional relapse pattern in HPV positive vs negative oropharyngeal cancers following radiotherapy; relation to pretreatment FDG-PET and radiotherapy target volumes

Background Previous studies have shown that a large proportion of relapses in head-and neck squamous cell carcinoma (HNSCC) following radiotherapy (RT) occur in the pretreatment FDG-PET avid volume (GTV-PET). The aim of the current work was to see if this was valid also in an oropharynx squamous cell carcinoma (OPSCC) only population, and to compare the loco-regional relapse pattern between HPV positive and HPV negative patients. Material and methods Among 633 OPSCC patients treated between 2009 and 2017, 46 patients with known HPV (p16) status and isolated loco-regional relapse were included. Oncologists contoured relapse volumes (RV) on relapse scans (PET/CT, CT or MR), which were thereafter deformed to match the anatomy of the planning CTs. The point of origin (center of volume) of the deformed RVs were determined and analyzed in relation to the RT target volumes (GTV-PET, GTV and CTVs). The relapse pattern was compared between HPV positive and HPV negative patients using Fischer’s exact test. Results Sixty RVs were contoured in the 46 patients. 55% (95% CI 44–67%) of relapses originated in GTV-PET, while the other RT volumes harbored 12% (5–20%) (GTV), 18% (9–28%) (high risk CTV) and 5% (0–11%) (low risk CTV) of relapses. Six relapses were found outside the RT target volumes. No significant difference in relapse pattern between HPV positive and HPV negative patients was found (p = .95). Conclusion There were no signs of difference in loco-regional relapse pattern between HPV positive and HPV negative patients. In agreement with previous findings, GTV-PET was the most frequent RT target volume of relapse.

Evaluating the geometric and dosimetric impact of applying anisotropic CTV to PTV margins in image-guided post-prostatectomy radiation therapy.

Guidelines for clinical target volume (CTV) to planning target volume (PTV) margins in post-prostatectomy radiation therapy (PPRT) are varied and often not clearly defined. Assessment of appropriateness of margins is commonly measured on prevalence of geographic miss. Cone-beam CT (CBCT) images (n = 92) for 10 PPRT patients were incorporated to provide on-treatment information on the appropriateness of six different CTV expansion margins in terms of geographic miss and change in dose-volume statistics for CTV, rectum and bladder. Uniform margins included 10 mm, 5 mm, 10 mm + 5 mm posteriorly and 5 mm + 3 mm posteriorly. In addition, two anisotropic margins were evaluated by separating the superior and inferior portions of the CTV before expansion. Treatment plans were created for each PTV retrospectively. The frequency of geographic miss was the smallest for the large uniform expansions but resulted in the highest organ-at-risk (OAR) doses. Geographic miss in the smaller uniform and anisotropic PTVs was more prevalent but commonly to a small volume < 1% of CTV. When averaged over all CBCT fractions, V95% dose for all CTV margins remained > 99%. The anisotropic expansions generated smaller irradiated target volumes and consequently saw up to 7.3% reduction in bladder dose when compared with similar uniform expansion margins. Supplementing the incidence of geographic miss with dosimetric information on target coverage and OAR doses provides more informed assessment of the appropriateness of different CTV expansion margins. Our study extends the evaluation of anisotropic margins for PPRT.

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.

Bladder only versus bladder plus pelvic lymph node chemoradiation for muscle-invasive bladder cancer.

Bladder-sparing chemoradiation therapy (CRT) is a definitive first-line treatment for muscle-invasive bladder cancer. The optimal radiotherapy target volume, either bladder-only (BO) or bladder plus pelvic lymph nodes (BPN), remains unclear. We identified 2,104 patients in the National Cancer Database with cT2-4N0M0 urothelial cell carcinoma of the bladder treated with CRT following maximal transurethral resection of bladder tumor from 2004 to 2016. The exposure of interest was BO vs. BPN treatment volume. The primary outcome was overall survival (OS), compared between groups using Kaplan-Meier and multivariable Cox proportional hazards. Sensitivity analysis tested an interaction term for clinical T stage (T2 vs. T3-4) and radiation modality (3-dimensional conformal radiotherapy vs. intensity modulated radiotherapy or proton therapy). Annual use of BO vs. BPN from 2004 to 2016 was compared using Cochran-Armitage test. A total of 578 patients were treated with BO and 1,526 patients treated with BPN CRT. There was a significant increase in BPN use from 2004 to 2016 (66.9%-76.8%, P < 0.0001). With a median follow-up of 6.2 years, there was no survival difference between groups: 5- and 10-year OS 27.4% (95% CI 23.4%-31.4%) in the BO group vs. 31.9% (95% CI 29.3%-34.6%) in the BPN group, and 13.1% (95% CI 9.7%-17.1%) in the BO group vs. 13.2% (95% CI 10.6%-16.0%) in the BPN group, respectively (log-rank P = 0.10). On multivariable analysis, there was no significant association between BPN and OS (adjusted HR 0.90, 95% CI 0.81-1.02, P = 0.09). On sensitivity analysis, we found no differential effect by T stage or radiation modality. Use of pelvic lymph node radiation has risen in the US but may not impact long-term survival outcomes for patients with node-negative muscle-invasive bladder cancer (MIBC). Optimizing radiation treatment volumes for CRT for MIBC will be important to study under prospective trials, such as the SWOG/NRG 1806.

Refining Target Volume Coverage After Parotidectomy for Cutaneous Squamous Cell Carcinoma: Omission of the Cervical Neck From the Radiation Field

For patients without pathologic evidence of cervical disease after neck dissection for cutaneous squamous cell carcinoma involving the parotid region, inclusion of the ipsilateral cervical neck in the postparotidectomy radiation volume is routinely performed. We report our experience with selective avoidance of the ipsilateral neck for patients undergoing postoperative radiation to the parotid bed. From January 2014 to December 2023, a total of 30 consecutive patients underwent postoperative radiation after parotidectomy for cutaneous squamous cell carcinoma involving the parotid area. All patients had previously had a neck dissection confirming pathologic N0 disease. Treatment was delivered using intensity modulated radiation therapy to a median dose of 60 Gy (range, 56-66 Gy). The radiation target volumes included the parotid bed only, with deliberate avoidance of the ipsilateral cervical neck. The median pathologic tumor size of the parotid tumor was 3.3 cm (range, 0.2-9.4 cm). Final pathologic evaluation showed positive microscopic margins in 8 patients (27%), perineural invasion in 17 patients (57%), and facial nerve involvement in 6 patients (20%). There were no isolated nodal failures. One patient developed an ipsilateral neck recurrence approximately 8 months after completion of radiation therapy. This occurred 2 months subsequent to the development of local recurrence. The 5-year actuarial rates of local (parotid) control, neck control, and overall survival were 87%, 97%, and 76%, respectively. Omission of the ipsilateral neck from the parotid volume does not compromise disease control for pathologically N0 patients undergoing postoperative radiation for cutaneous squamous cell carcinoma involving the parotid region. Practical implications are discussed.

Emerging evidence for adapting radiotherapy to immunotherapy.

Immunotherapy has revolutionized the clinical management of many malignancies but is infrequently associated with durable objective responses when used as a standalone treatment approach, calling for the development of combinatorial regimens with superior efficacy and acceptable toxicity. Radiotherapy, the most commonly used oncological treatment, has attracted considerable attention as a combination partner for immunotherapy owing to its well-known and predictable safety profile, widespread clinical availability, and potential for immunostimulatory effects. However, numerous randomized clinical trials investigating radiotherapy-immunotherapy combinations have failed to demonstrate a therapeutic benefit compared with either modality alone. Such a lack of interaction might reflect suboptimal study design, choice of end points and/or administration of radiotherapy according to standard schedules and target volumes. Indeed, radiotherapy has empirically evolved towards radiation doses and fields that enable maximal cancer cell killing with manageable toxicity to healthy tissues, without much consideration of potential radiation-induced immunostimulatory effects. Herein, we propose the concept that successful radiotherapy-immunotherapy combinations might require modifications of standard radiotherapy regimens and target volumes to optimally sustain immune fitness and enhance the antitumour immune response in support of meaningful clinical benefits.

Brain radiotherapy in patients treated for a newly diagnosed primary central nervous system lymphoma: professional practice evaluation in 19 French centers

Introduction The objective of this study was a multicentric evaluation of professional practices, analyzing the irradiation technique itself and its impact on survival and recurrence sites, in primary central nervous system lymphomas (PCNSLs). Methods We retrospectively analyzed the technical and clinical records of 79 PCNSL patients included in the database of the national expert network for oculocerebral lymphoma (‘LOC’) who were treated with brain radiotherapy as first-line treatment for newly diagnosed primary central nervous system lymphoma between 2011 and 2018. Results The number of patients treated with brain radiotherapy gradually decreased over time. The heterogeneity of radiotherapy prescriptions was significant, and 55% of them did not comply with published recommendations in terms of irradiation dose and/or volume. The proportion of complete responders to induction chemotherapy treated with reduced-dose radiotherapy increased over time. Partial brain radiotherapy was associated with significantly lower overall survival in univariate analysis. In partial responders to induction chemotherapy, increasing the total dose to the brain >30 Gy and adding a boost to the WBRT induced a trend toward improved progression-free and overall survival. Five recurrences (13%) occurred exclusively in the eyes, all in patients whose eyes had been excluded from the irradiation target volume and including 2 patients without ocular involvement at diagnosis. Conclusion The visibility of recommendations for prescribing brain radiotherapy for the treatment of newly diagnosed primary central nervous system lymphoma needs to be improved to harmonize practices and improve their quality. We propose an update of the recommendations.

Interobserver agreement on definition of the target volume in stereotactic radiotherapy for pancreatic adenocarcinoma using different imaging modalities

PurposeThe aim of this study was to evaluate interobserver agreement (IOA) on target volume definition for pancreatic cancer (PACA) within the Radiosurgery and Stereotactic Radiotherapy Working Group of the German Society of Radiation Oncology (DEGRO) and to identify the influence of imaging modalities on the definition of the target volumes.MethodsTwo cases of locally advanced PACA and one local recurrence were selected from a large SBRT database. Delineation was based on either a planning 4D CT with or without (w/wo) IV contrast, w/wo PET/CT, and w/wo diagnostic MRI. Novel compared to other studies, a combination of four metrics was used to integrate several aspects of target volume segmentation: the Dice coefficient (DSC), the Hausdorff distance (HD), the probabilistic distance (PBD), and the volumetric similarity (VS).ResultsFor all three GTVs, the median DSC was 0.75 (range 0.17–0.95), the median HD 15 (range 3.22–67.11) mm, the median PBD 0.33 (range 0.06–4.86), and the median VS was 0.88 (range 0.31–1). For ITVs and PTVs the results were similar. When comparing the imaging modalities for delineation, the best agreement for the GTV was achieved using PET/CT, and for the ITV and PTV using 4D PET/CT, in treatment position with abdominal compression.ConclusionOverall, there was good GTV agreement (DSC). Combined metrics appeared to allow a more valid detection of interobserver variation. For SBRT, either 4D PET/CT or 3D PET/CT in treatment position with abdominal compression leads to better agreement and should be considered as a very useful imaging modality for the definition of treatment volumes in pancreatic SBRT. Contouring does not appear to be the weakest link in the treatment planning chain of SBRT for PACA.

The Role of MRI and PET/CT in Radiotherapy Target Volume Determination in Gastrointestinal Cancers-Review of the Literature.

Positron emission tomography with computed tomography (PET/CT) and magnetic resonance imaging (MRI) could improve accuracy in target volume determination for gastrointestinal cancers. A systematic search of the PubMed database was performed, focusing on studies published within the last 20 years. Articles were considered eligible for the review if they included patients with anal canal, esophageal, rectal or pancreatic cancer, as well as PET/CT or MRI for radiotherapy treatment planning, and if they reported interobserver variability or changes in treatment planning volume due to different imaging modalities or correlation between the imaging modality and histopathologic specimen. The search of the literature retrieved 1396 articles. We retrieved six articles from an additional search of the reference lists of related articles. Forty-one studies were included in the final review. PET/CT seems indispensable for target volume determination of pathological lymph nodes in esophageal and anal canal cancer. MRI seems appropriate for the delineation of primary tumors in the pelvis as rectal and anal canal cancer. Delineation of the target volumes for radiotherapy of pancreatic cancer remains challenging, and additional studies are needed.

A Tool to Integrate Electrophysiological Mapping for Cardiac Radioablation of Ventricular Tachycardia

Cardiac radioablation is an emerging therapy for recurrent ventricular tachycardia. Electrophysiology (EP) data, including electroanatomic maps (EAM) and electrocardiographic imaging (ECGI), provide crucial information for defining the arrhythmogenic target volume. The absence of standardized workflows and software tools to integrate the EP maps into a radiation planning system limits their use. This study developed a comprehensive software tool to enable efficient utilization of the mapping for cardiac radioablation treatment planning. The tool, HeaRTmap, is a Python-scripted plug-in module on the open-source 3D Slicer software platform. HeaRTmap is able to import EAM and ECGI data and visualize the maps in 3D Slicer. The EAM is translated into a 3D space by registration with cardiac magnetic resonance images (MRI) or computed tomography (CT). After the scar area is outlined on the mapping surface, the tool extracts and extends the annotated patch into a closed surface and converts it into a structure set associated with the anatomic images. The tool then exports the structure set and the images as The Digital Imaging and Communications in Medicine Standard in Radiotherapy for a radiation treatment planning system to import. Overlapping the scar structure on simulation CT, a transmural target volume is delineated for treatment planning. The tool has been used to transfer Ensite NavX EAM data into the Varian Eclipse treatment planning system in radioablation on 2 patients with ventricular tachycardia. The ECGI data from CardioInsight was retrospectively evaluated using the tool to derive the target volume for a patient with left ventricular assist device, showing volumetric matching with the clinically used target with a Dice coefficient of 0.71. HeaRTmap smoothly fuses EP information from different mapping systems with simulation CT for accurate definition of radiation target volume. The efficient integration of EP data into treatment planning potentially facilitates the study and adoption of the technique.

PO-1371 A simplified method for delineation of target volumes in 4D oesophageal cancer radiotherapy

PO-1371 A simplified method for delineation of target volumes in 4D oesophageal cancer radiotherapy

Clinical Outcomes of Thymic Carcinoma: The Role of Radiotherapy Combined with Multimodal Treatments

We aimed to identify the role of radiotherapy (RT) in the treatment of thymic carcinoma as well as the optimal RT target volume. This single-institution retrospective study included 116 patients diagnosed with thymic carcinoma between November 2006 and December 2021 who received multimodal treatment including RT with or without surgery or chemotherapy. Seventy-nine patients (68.1%) were treated with postoperative RT, 17 patients (14.7%) with preoperative RT, 11 patients (9.5%) with definitive RT, and nine patients (7.8%) with palliative RT. The target volume was defined as the tumor bed or gross tumor with margin, and selective irradiation of the regional nodal area was performed when involved. With a median follow-up of 37.0 (range, 6.7-174.3) months, the 5-year overall survival (OS), progression-free survival, and local recurrence-free survival rates were 75.2%, 47.7% and 94.7%, respectively. The 5-year OS was 51.9% in patients with unresectable disease. Overall, 53 recurrences were observed, of which distant metastasis was the most common pattern of failure (n = 32, 60.4%) after RT. No isolated infield or marginal failures were observed. Thirty patients (25.8%) who had lymph node metastases at the initial diagnosis had regional nodal areas irradiated. There was no lymph node failure inside the RT field. A tumor dimension of ≥5.7 cm (hazard ratio [HR] 3.01; 95% confidence interval [CI] 1.25-7.26; p = 0.030) and postoperative RT (HR 0.20; 95% CI 0.08-0.52; p = 0.001) were independently associated with OS. Intensity-modulated-RT-treated patients developed less overall toxicity (p < 0.001) and esophagitis (p < 0.021) than three-dimensional-conformal-RT-treated patients. A high local control rate was achieved with RT in the primary tumor sites and involved lymph node area in the treatment of thymic carcinoma. A target volume confined to the tumor bed or gross tumor plus margin with the involved lymph node stations seems reasonable. The advanced RT techniques with intensity-modulated RT have led to reduced RT-related toxicity.

Assessment of Setup Errors in Gynecological Malignancies Treated With Radiotherapy Using Onboard Imaging.

Introduction Radiotherapy plays a vital role in the management of gynecological malignancies. However, maintaining patient position poses a challenge during daily radiotherapy treatment of these patients. This study identifies and calculates setup errors in interfraction radiotherapy and optimum clinical target volume-planning target volume (CTV-PTV) margins in patients with gynecological malignancies. Material and methods A total of 38 patients with gynecological malignancies were included in the study. They were treated with a dose of 50 Gy in 25 fractions for five weeks, followed by brachytherapy. All patients were immobilized using a 4-point thermoplastic cast. Anteroposterior and lateral images were taken thrice weekly for five weeks. Setup verification was done using kilovoltage images obtained using Varian On-board Imager (Varian Medical System, Inc., Palo Alto, CA). Manual matching was done utilizing bony landmarks such as the widest portion of the pelvic brim, anterior border of S1 vertebrae, and pubic symphysis in the X, Y, and Z axes, respectively. Results A total of 1140 images were taken. The individual systematic errors ranged from -0.24 to 0.17 cm (LR), -0.15 to 0.19 cm (AP) and -0.36 to 0.29 cm (CC) while the individual random errors ranged from 0.04 to 0.36 cm (LR), 0.06 to 0.33 cm (AP) and 0.10 to 0.29 cm (CC). The calculated CTV-PTV margins in LR, AP and CC directions were 0.17, 0.18, and 0.25 cm (ICRU-62); 0.28, 0.31 and 0.47 cm in LR, AP and CC directions (Stroom's), and 0.32, 0.36 and 0.55 cm (Van Herk) respectively. Conclusion Based on this study, the calculated CTV-PTV margin is 6 mm in gynecological malignancies, and the present protocol of 7 mm of PTV margin is optimum.

Oral Sequelae after Head and Neck Radiotherapy: RCT Comparing 3D-Printed Tissue Retraction Devices with Conventional Dental Splints.

To evaluate oral sequelae after head and neck radiotherapy (RT) when using two different types of intraoral appliances. Thermoplastic dental splints (active control) protect against backscattered radiation from dental structures. Semi-individualized, 3D-printed tissue retraction devices (TRDs, study group) additionally spare healthy tissue from irradiation. A total of 29 patients with head and neck cancer were enrolled in a randomized controlled pilot trial and allocated to receive TRDs (n = 15) or conventional splints (n = 14). Saliva quality and quantity (Saliva-Check, GC), taste perception (Taste strips, Burghart-Messtechnik), and oral disability (JFLS-8, OHIP-14, maximum mouth opening) were recorded before and 3 months after RT start. Radiotherapy target volume, modality, total dose, fractionation, and imaging guidance were case-dependent. To evaluate intra-group developments between baseline and follow-up, nonparametric Wilcoxon tests were performed. Mann-Whitney-U tests were applied for inter-group comparisons. At follow-up, taste perception was unimpaired (median difference in the total score; TRDs: 0, control: 0). No significant changes were found regarding oral disability. Saliva quantity (stimulated flow) was significantly reduced with conventional splints (median -4 mL, p = 0.016), while it decreased insignificantly with TRDs (median -2 mL, p = 0.07). Follow-up was attended by 9/15 study group participants (control 13/14). Inter-group comparisons showed no significant differences but a tendency towards a better outcome for disability and saliva quality in the intervention group. Due to the small cohort size and the heterogeneity of the sample, the results must be interpreted with reservation. Further research must confirm the positive trends of TRD application. Negative side-effects of TRD application seem improbable.

Study of radiation-induced pneumonitis after arc and static irradiation in lungs of rats

The clinical application of the results of the experimental radiotherapy on animals is currently not widely used. The research of radiation injuries after irradiation target in rat lungs using the image-guided platform SmART+ (Precision, North Branford, Conn., USA) is a pilot study for the establishment of an animal model of radiation-induced pulmonary toxicity.Aim: To define the typical doses and target volumes in rat lung to o serve radiation pneumonitis.Material and methods. Four groups of Wistar and Wag rats, distinguishing by age (10–16,5 months) and weight (350-850 g.), were studied. Dosimetric treatment plans were calculated prior to irradiation, using arc or static methods, doses (10–30 Gy), target lung volumes (0,045–1,24 cm3), localization (right or left, top or bottom). Dosimetric planning provides optimal radiation exposure to the target and controls organ at risk doses. Computer tomography (CT) scans were performed for 16 weeks to observe radiation pneumonitisResults. To obtain the rat lung density in Hounsfield units (HU), healthy animals were scanned, CT images were processed, and the mean and standard deviation were calculated. Lung density values of rats (control values) are 519.6 ± 46.2 (HU). Comparison of experimental data on irradiated animals and control values was carried out. As a result, the relationship of the target volume, the delivered dose and the survival rate of animals after irradiation was established. It was shown that the “mean value of lung density” could be used for quantitative analysis of lung injuries after irradiation.Conclusion. Typical doses and target volumes in rat lungs to observe radiation pneumonitis were obtained. Decreasing aeration of lung tissue was derived at delivered dose 16 Gy and irradiated target volume in lung at least 0.5 cm3 (8%).

Excluding prepontine cistern from whole ventricle radiotherapy target volume in localized germinoma.

The target delineation of whole ventricle radiotherapy (WVRT) in germinoma varies among radiation oncologists, especially regarding the inclusion of the prepontine cistern (PC). We evaluated the outcome of PC-sparing WVRT in localized germinoma. We identified 87 localized intracranial germinoma patients who received radiotherapy (RT) following chemotherapy between 1999 and 2020. By institutional policy, RT for localized germinoma excluded PC from the target volume. WVRT was delivered to 65 patients (74.7%) and involved field radiotherapy (IFRT) to 22 patients (25.3%). The median dose was 45.0 Gy (range, 23.4 to 55.8 Gy) for the primary tumor and 19.8 Gy (rangem 14.4 to 36.0 Gy) for the whole ventricle. We analyzed the dosimetric differences of the organs at risk between the PC-excluding plans and the PC-including ones. The median follow-up duration was 7.8 years (range, 1.0 to 22.5 years). The 10-year recurrence-free survival and overall survival rates were 86.3% and 90.9%, respectively. The recurrences occurred in eight patients (8.7%), including five patients after IFRT and three after WVRT. Five of them showed recurrences at lateral ventricles and only one patient experienced spinal cord relapse. However, no relapse in the PC occurred. Endoscopic third ventriculostomy was not a significant prognostic factor. The dosimetric comparisons showed significantly lower mean doses to the brainstem and the cochleae when the PC was excluded. WVRT for localized germinoma can safely exclude the PC in the target volume, reducing radiation dose to the brain stem. The target protocol needs to reach a consensus regarding the PC in prospective trials.

Effect of Radiation Therapy Quality Assurance on Nasopharyngeal Carcinoma: Usage of a Novel, Web-Based Quality Assurance Application

We used a new web application for rapid review of radiotherapy (RT) target volumes to evaluate the relationship between target delineation compliance with the international guidelines and outcomes of definitive RT for nasopharyngeal carcinoma (NPC). The dataset consists of CT simulation scans, RT structures, and clinical data of 354 pathology-confirmed NPC patients treated with intensity-modulated RT between 2005 and 2017. Target volumes were peer-reviewed in RT QA rounds, and target contours were revised, if recommended, before treatment. We imported the contours of intermediate-risk clinical target volumes of the primary tumor (IR-CTVp) of 332 patients into the application. Inclusion of anatomic sites within IR-CTVp was determined in accordance with 2018 International guideline for CTV delineation for NPC and correlated with time to local failure (TTLF) using Cox-regression. In the peer-review QA analysis, local and distant control and overall survival (OS) rates were similar between peer-reviewed and non-reviewed cases and between cases with and without target contour changes. In the CTV compliance analysis, with a median follow-up of 5.6 years, 5-year TTLF and OS rates were 93.1% and 85.9% respectively. The most frequently non-guideline compliant anatomic sites were sphenoid sinus (n=69, 20.8%), followed by cavernous sinus (n=38, 19.3%), left and right petrous apices (n=37 and 32, 11.1% and 9.6%), and clivus (n=14, 4.2%). Among 23 patients with a local failure (6.9%), the number of non-compliant cases were 8 for sphenoid sinus, 7 cavernous sinus, 4 left and 3 right petrous apices, and 2 clivus. Cavernous sinus-conforming cases showed higher TTLF in comparison with non-conforming cases (93.6% vs 89.1%, p=0.013). Multivariable analysis confirmed that cavernous sinus non-compliance was prognostic for TTLF. Our application allowed rapid quantitative review of CTVp in a large NPC cohort. While compliance with the international guidelines was high, under-coverage of the cavernous sinus was correlated with TTLF.

Nasopharyngeal cancer: the impact of guidelines and teaching on radiation target volume delineation

Target volume delineation in the radiation treatment of nasopharyngeal cancer is challenging due to several reasons such as the complex anatomy of the site, the need for the elective coverage of definite anatomical regions, the curative intent of treatment and the rarity of the disease, especially in non-endemic areas. We aimed to analyze the impact of educational interactive teaching courses on target volume delineation accuracy between Italian radiation oncology centers. Only one contour dataset per center was admitted. The educational course consisted in three parts: (1) The completely anonymized image dataset of a T4N1 nasopharyngeal cancer patient was shared between centers before the course with the request of target volume and organs at risk delineation; (2) the course was held online with dedicated multidisciplinary sessions on nasopharyngeal anatomy, nasopharyngeal cancer pattern of diffusion and on the description and explanation of international contouring guidelines. At the end of the course, the participating centers were asked to resubmit the contours with appropriate corrections; (3) the pre- and post-course contours were analyzed and quantitatively and qualitatively compared with the benchmark contours delineated by the panel of experts. The analysis of the 19 pre- and post-contours submitted by the participating centers revealed a significant improvement in the Dice similarity index in all the clinical target volumes (CTV1, CTV2 and CTV3) passing from 0.67, 0.51 and 0.48 to 0.69, 0.65 and 0.52, respectively. The organs at risk delineation was also improved. The qualitative analysis consisted in the evaluation of the inclusion of the proper anatomical regions in the target volumes; it was conducted following internationally validated guidelines of contouring for nasopharyngeal radiation treatment. All the sites were properly included in target volume delineation by >50% of the centers after correction. A significant improvement was registered for the skull base, the sphenoid sinus and the nodal levels. These results demonstrated the important role that educational courses with interactive sessions could have in such a challenging task as target volume delineation in modern radiation oncology.