Clinical Target Volume Volume Research Articles

Evaluation of radiotherapy planning approaches for head and neck patients with tumors close to the skin surface.

In radiotherapy of the head and neck (H&N) it is common for the clinical target volume (CTV) to extend to the patient's skin. Adding a margin for set-up uncertainty and delivery creates a planning target volume (PTV) that extends beyond the patient surface. This can result in excessive fluence being delivered to the build-up region and therefore the skin. This study evaluates four different planning methods used when inverse-planning H&N radiotherapy treatments with CTV extending to the skin. The aim of the study was to determine which planning method gives superior plan quality. Ten H&N cancer patients with a CTV contoured to the skin were inverse-planned using four planning methods. The planning methods compared were: cropping the optimization PTV back from the skin surface by 5.0, 3.0, and 0.0mm and a virtual bolus method. For each planning method, the increased fluence at the skin surface was analyzed. The CTV coverage and skin doses were compared. Plan robustness was evaluated by applying an isocenter shift of ±3.0mm in the major axes. The planning method cropping the PTV 0.0mm from the skin surface results in an increased fluence in the build-up region. The average volume of CTV receiving 98% of the prescription dose was 89.6%±3.4%, 91.6%±2.4%, and 93.5%±1.7% when cropped 5.0, 3.0, and 0.0mm, respectively, and 93.4%±2.1% for the virtual bolus method. Introducing plan uncertainty affects CTV coverage the most when cropping 5.0mm. When plan uncertainties are considered the methods of cropping 5.0, 3.0mm, and the virtual bolus method have the same average skin dose within ±0.3%. This study shows that a virtual bolus planning method results in no increased fluence at the patient's surface, improves CTV coverage, and is the most robust to changes in setup and patient anatomy.

Intra-fractional geometric and dose/volume metric variations of magnetic resonance imaging-guided stereotactic radiotherapy of prostate bed after radical prostatectomy

Background and purposeMagnetic Resonance Imaging (MRI)-guided Stereotactic body radiotherapy (SBRT) treatment to prostate bed after radical prostatectomy has garnered growing interests. The aim of this study is to evaluate intra-fractional anatomic and dose/volume metric variations for patients receiving this treatment. Materials and methodsNineteen patients who received 30–34 Gy in 5 fractions on a 0.35T MR-Linac were included. Pre- and post-treatment MRIs were acquired for each fraction (total of 75 fractions). The Clinical Target Volume (CTV), bladder, rectum, and rectal wall were contoured on all images. Volumetric changes, Hausdorff distance, Mean Distance to Agreement (MDA), and Dice similarity coefficient (DSC) for each structure were calculated. Median value and Interquartile range (IQR) were recorded. Changes in target coverage and Organ at Risk (OAR) constraints were compared and evaluated using Wilcoxon rank sum tests at a significant level of 0.05. ResultsBladder had the largest volumetric changes, with a median volume increase of 48.9 % (IQR 28.9–76.8 %) and a median MDA of 5.1 mm (IQR 3.4–7.1 mm). Intra-fractional CTV volume remained stable with a median volume change of 1.2 % (0.0–4.8 %). DSC was 0.97 (IQR 0.94–0.99). For the dose/volume metrics, there were no statistically significant changes observed except for an increase in bladder hotspot and a decrease of bladder V32.5 Gy and mean dose. The CTV V95% changed from 99.9 % (IQR 98.8–100 %) to 99.6 % (IQR 93.9–100 %). ConclusionDespite intra-fractional variations of OARs, CTV coverage remained stable during MRI-guided SBRT treatments for the prostate bed.

Dosimetric Comparison Study of Proton Therapy Using Line Scanning versus Passive Scattering and Volumetric Modulated Arc Therapy for Localized Prostate Cancer.

The proton irradiation modality has transitioned from passive scattering (PS) to pencil beam scanning. Nevertheless, the documented outcomes predominantly rely on PS. Thirty patients diagnosed with prostate cancer were selected to assess treatment planning across line scanning (LS), PS, and volumetric modulated arc therapy (VMAT). Dose constraints encompassed clinical target volume (CTV) D98 ≥ 73.0 Gy (RBE), rectal wall V65 < 17% and V40 < 35%, and bladder wall V65 < 25% and V40 < 50%. The CTV, rectal wall, and bladder wall dose volumes were calculated and evaluated using the Freidman test. The LS technique adhered to all dose limitations. For the rectal and bladder walls, 10 (33.3%) and 21 (70.0%) patients in the PS method and 5 (16.7%) and 1 (3.3%) patients in VMAT, respectively, failed to meet the stipulated requirements. The wide ranges of the rectal and bladder wall volumes (V10-70) were lower with LS than with PS and VMAT. LS outperformed VMAT across all dose-volume rectal and bladder wall indices. The LS method demonstrated a reduction in rectal and bladder doses relative to PS and VMAT, thereby suggesting the potential for mitigating toxicities.

Single- versus Multi-computed Tomography Simulation for High-dose-rate Postoperative Gynecological Intracavitary Brachytherapy.

This study aimed to investigate whether there is a dosimetric difference of implementing single instead of multi-computed tomography (CT) simulation treatment planning for high-dose-rate postoperative gynecological intracavitary brachytherapy (BT). Eighty patients were registered in the study. They received three BT fractions of 7 Gy/week (three CTs, three original plans). The organs at risk (OAR), the rectal wall, and the clinical target volume (CTV) were delineated. The delivered doses for the 2cc of OARs (D2cc), 1cc of rectal wall (D1cc), as well as for the 90% and 100% of CTV volume (DCTV90%, DCTV100%) were evaluated. To evaluate the values of the above parameters if the single-CT-simulation method has been chosen, the time of the first treatment plan was corrected for the decay and applied as the second and third CT, retrospectively, creating the next fractions (two revised plans). No statistically significant (P > 0.05) differences were found between the original and revised plans for the OARs and CTV. However, for the single-CT-simulation method, it was noted that the dose constraints for the total rectal dose were exceeded in some cases (36.3%). The fact that rectal dose constraints were exceeded in 1/3 of patients with the single-CT-simulation method is dosimetrically significant.

Determination of internal target volume with Cine-MRI sequence for prostate MRI-Guided radiotherapy.

In prostate radiotherapy, the intrafractional target motion negatively affects treatment accuracy. Generating internal target volume (ITV) using four-dimensional (4D) images may resolve the issue of intrafractional target motion induced by bladder filling and bowel movement. However, no 4D imaging techniques suitable for the prostate are currently available in clinical practice. This study aimed to determine the ITV based on cine magnetic resonance imaging (MRI) sequence for intrafractional target motion management in prostate MRI-guided radiotherapy. A reference ITV was generated in simulation process. Then, the reference ITV was adapted with cine MRI sequence before online planning in each fraction. Finally, the reference ITV was updated with the cine MRI sequence acquired during beam delivery after each fraction. Cine MRI sequences and positioning three-dimensional (3D) MRI from 35 patients were retrospectively collected. Clinical target volume (CTV) coverage was computed according to the two-dimensional contour of CTV and ITV on cine MRI images. Relative target size was calculated as the ratio of the volume of ITV and CTV. Isotropic planning target volume (PTV; 5mm margin) and anisotropic PTV (3mm margin in the posterior direction and 5mm margin in other directions) were generated for comparison. The CTV coverage rate of the proposed ITV had a mean value of 98.61%±0.51%, whereas the CTV coverage rates of the isotropic and anisotropic PTVs were 97.43%±0.41% and 96.58%±0.73%, respectively. The proposed ITV had a relative target size of 1.79±0.17, whereas the anisotropic and isotropic PTVs had relative target sizes of 1.92±0.12 and 2.21±0.19, respectively. For both the CTV coverage rate and target relative size, significant differences were observed between the proposed ITV and the other two PTVs (p<0.05). The ITV achieved higher CTV coverage with smaller size than conventional isotropic and anisotropic PTVs, indicating that it can effectively deal with the intrafractional movement of the prostate.

Is bilateral radiotherapy necessary for patients with unilateral squamous cell carcinoma of unknown primary of the head and neck region?

Background and PurposeSquamous cell carcinoma of unknown primary (SCC-CUP) of the head and neck region remains a clinical challenge, with uncertainty surrounding the necessity of contralateral irradiation of cervical lymphatic drainage in cases of unilateral involvement. Materials and MethodsA retrospective study was conducted at the Department of Radiation Oncology, University Medical Center Mainz, on a cohort of 50 patients with unilateral SCC-CUP of the head and neck region treated between 2005 and 2019. 30 patients received bilateral and 20 received unilateral cervical radiotherapy. The majority (n = 38, 76 %) were treated with modern IMRT/ VMAT (Intensity-modulated Radiation Therapy/ Volumetric Modulated Arc Therapy) techniques. ResultsAfter a median follow-up of 64.5 months, locoregional recurrences occurred in 26 % of cases (n = 13/50), all of which were ipsilateral and predominantly within the volume of the previous irradiated CTV (clinical target volume) (85 %, n = 11/13). No patient treated unilaterally developed a contralateral recurrence in the neck. After 3 years, we observed 7 locoregional recurrences in the bilateral irradiated group (n = 7/30, 23 %), and 5 locoregional recurrences in the unilateral irradiated group (n = 5/20, 25 %). After 3 years, 12 patients had died in the bilateral irradiated group (n = 12/30, 40 %), and 7 in the unilateral irradiated group (n = 7/20, 35 %). 7 Patients showed distant metastases after 3 years in the bilateral irradiated group (n = 7/30, 23 %), and 2 in the unilateral irradiated group (n = 2/20, 10 %). Locoregional control (LRC) at 5 years was 66.2 % in the bilaterally irradiated group, and 70.0 % in the unilaterally irradiated group. Overall survival (OS) was 52.6 % (bilateral) and 64.0 % (unilateral). Distant metastasis-free survival (DMFS) was 74.7 % (bilateral) and 84.4 % (unilateral). No significant differences were observed in OS (p = 0.37), LRC (p = 0.91), and DMFS (p = 0.91) between the groups.Acute toxicity ≥ °2 accordingly CTCAE (Common Terminology Criteria of Adverse Events) was high with 97% while late toxicity ≥ °2 was moderate with 31%. There was no statistically significant difference between the group of unilateral and bilateral irradiated patients. ConclusionThese data suggest that contralateral cervical irradiation may be of limited benefit in patients with SCC-CUP, as recurrences occured ipsilaterally, and predominantly within the area of prior irradiation. Unilateral irradiation seems to be adequate for carefully selected patients.

Phase 2 Clinical Trial of Simultaneous Boost Intensity Modulated Radiation Therapy With 3 Dose Gradients in Patients With Stage I-II Nasal Type Natural Killer/T-Cell Lymphoma: Long-Term Outcomes of Survival and Quality of Life

The aim of this study was to investigate the treatment results and long-term quality of life in patients with early-stage extranodal natural killer/T-cell lymphoma who were prospectively treated with simultaneous boost intensity modulated radiation therapy (SIB-IMRT) with 3 dose gradients. Sixty patients with stage I-II nasal cavity natural killer/T-cell lymphoma (NKTCL) and Waldeyer's ring NKTCL were enrolled in a single-arm, prospective, phase 2 clinical trial from August 2011 to April 2015. All patients were treated with definitive radiation therapy combined with short-course induction chemotherapy. A newly designed SIB-IMRT scheme was uniformly adopted, with 54.6 Gy for the gross tumor volume (GTV) of the primary tumor and GTV of the positive lymph nodes, 50.7 Gy for the high-risk clinical target volume (CTV), and 45.5 Gy for the low-risk CTV, all delivered in 26 daily fractions. Before SIB-IMRT, L-asparaginase-based induction chemotherapy was used in 95.0% (57/60) of patients. With a median follow-up time of 95.8 months, the 5-year locoregional recurrence-free survival, progression-free survival, and overall survival rates were 83.3%, 81.7%, and 88.3%, respectively. Dosimetric analysis in the first 21 patients showed satisfying conformality for planning target volume of GTV, high-risk CTV, and low-risk CTV, while the organs at risk were well protected. The results of long-term quality-of-life investigations in patients without progression were favorable, and nasal discomfort was the most common symptom. No grade 3 or 4 acute or late toxicities were observed. The scheme of target volume delineation and dose setting that we designed has favorable clinical effects with mild side effects in treating patients with stage I-II nasal cavity NKTCL and Waldeyer's ring NKTCL.

Dosimetric Implications of Prostate Bed Deformability: An Analysis of the SCIMITAR Clinical Trial.

The post-operative prostate bed is a dynamic target volume due to the deformable nature of the bladder and rectum. These changes can lead to incorrect dosing of the prostate bed and organs at risk (OARs). Our objective was to quantify the dosimetric impact of prostate bed and OAR deformation. SCIMITAR (NCT03541850) is a prospective phase II clinical trial evaluating stereotactic body radiotherapy (SBRT) in the post-prostatectomy setting. This analysis included a subset of patients who received 5 fractions of 6-6.8 Gy to the prostate bed under CT-based image guidance. The clinical target volume (CTV) and OARs were contoured on fractional CBCT images. Changes in volume, shape (via the dice similarity coefficient [DSC]), and dosimetry were quantified. Student's t-test was used to analyze the differences between planning and daily treatment outcomes. A total of 29 patients (145 fractional images) were analyzed. We found the CTV volume remained stable (median change 1.1%; IQR: -15.1% - 16.1%), whereas the CTV shape was deformable (DSC of 0.76 [IQR: 0.71 - 0.79]). The bladder and rectum exhibited changes with median volume change of 5.7% (IQR: -24.3% - 51.0%) and 5.5% (IQR: -8.7% - 21.9%), respectively and median DSC of 0.77 (IQR: 0.68 - 0.84) and 0.74 (IQR: 0.69 - 0.80) respectively. The CTV received less radiation dose than planned (volume receiving 95%: 93.2% actual vs 99.6% planned, p < 0.01). 39% (56/145) of total fractions and 52% (15/29) of patients met criteria for CTV under-coverage (volume receiving 95% of the prescription dose < 93%). The rectum received higher dose than planned on several parameters (e.g., V27.5 Gy increased from 15.4% to 21.0% [p = 0.009] and V32.5 Gy increased from 6.0% to 10.9% [p = 0.006]) (Table 1). We found underdosing of the prostate CTV and overdosing of the rectum in patients receiving CT-guided postoperative SBRT. While future work will correlate these dosimetric consequences with toxicity, these data suggest that approaches such as adaptive radiotherapy may be beneficial.

Posterior Neck Coverage in Patients Receiving Regional Nodal Irradiation for Breast Cancer

Patterns-of-failure studies suggest the posterior neck (PN) may harbor microscopic disease in patients with locally advanced breast cancer. We compared target coverage, lung dose, and toxic effects in patients treated with either an anterior oblique field (AO) or opposed oblique fields (OO) to address the superior axillary and supraclavicular nodal (SCV) regions. We identified 119 consecutively treated patients who received regional nodal irradiation, including a "third field," to address the superior axillary and supraclavicular nodal regions with a monoisocentric technique in our institution. Coverage of the axillary clinical target volume (CTV), SCV CTV and PN CTV was determined based on the delivered treatment plan. Wilcoxon rank-sum test and Fisher's exact test were used to compare coverage of the axillary, SCV, and PN CTVs, lung dosimetry, and toxic effects (graded by the Common Terminology Criteria for Adverse Events v4.0) between patients receiving an AO or OO. There were 29 patients in the AO group and 80 in the OO group. All patients in the AO group received conventionally fractionated radiation versus 61% in the OO group. Modestly hypofractionated plans were delivered to 39% of the OO group. The body mass index and anterior-posterior separation at the matchline (measured at the center of the carotid artery) were similar in both groups. The median volume (%) of the SCV CTV receiving at least 90% of the prescription dose (V90%) was 91% (85, 99) in the AO group and 93% (91, 95) in the OO group (P = 0.2). The median V90% of the PN CTV was 30% (12, 49) in the AO group and 100% (100, 100) in the OO group (P<0.001). The median V90% in the axillary levels I, II and III CTVs were 98%, 95% and 90%, respectively, in the AO group and all 100% in the OO group (P<0.001). Maximum dose and heterogeneity in the SCV CTV were similar in both groups. Including only patients who received conventionally fractionated plans, the mean lung dose (cGy) was 1216 in the AO group and 1328 in the OO group (P = 0045). The lung V5 Gy, V10 Gy and V20 Gy were similar in both groups. Ipsilateral upper extremity lymphedema (all grade 1) was 3.4% in the AO group and 2.5% in the OO group (p>0.9). Moist desquamation in the neck was 0% in the AO group and 1.2% in the OO group (p>0.9). Pneumonitis (all grade 1) was 0% in the AO group and 1.2% in the OO group (p>0.9). Compared to a single anterior field, opposed oblique fields provide superior axillary and posterior neck coverage without increasing toxicity.

Consensus Delineation Guidelines for Pelvic Lymph Node Radiation Therapy of Prostate Cancer: On Behalf of the Francophone Group of Urological Radiation Therapy (GFRU)

Clinical target volume (CTV) delineation for pelvic lymph nodes in prostate cancer is currently based on 3 consensus guidelines with some inherent discrepancies. To improve the reproducibility in nodal delineation, the Francophone Group of Urological Radiotherapy (Groupe Francophone de Radiothérapie Urologique [GFRU]) worked toward proposing an easily applicable, reproducible, and practice-validated contouring guideline for pelvic nodal CTV. The nodal CTV data sets of a high-risk node-negative prostate cancer clinical case contoured by 86 radiation oncologists participating in a GFRU contouring workshop were analyzed. CTV volumes were defined before and after a structured presentation of literature data on lymphatic drainage pathways and patterns of nodal involvement and relapse, illustrated using a reference contour (CRef) defined by 3 GFRU experts. The consistency between the participants' contours and CRef was assessed quantitively by means of the Simultaneous Truth and Performance Level Estimation (STAPLE) method, the Dice coefficient, and the Hausdorff distance and qualitatively using a count map. These results combined with the literature review were thoroughly discussed among GFRU experts to reach a consensus. From the 86 workshop participants, the volume of the STAPLE CTV was 591 cc compared with 502 cc for CRef. The Dice coefficient of the STAPLE CTV compared with the experts' CRef was 0.736 (±0.084) before and 0.823 (±0.070) after the workshop; the standard deviation decreased from 11.5% to 8.5% over the workshop. The Hausdorff distance of the STAPLE CTV compared with the CRef was 34.5 mm (±12.4) before the workshop and 21.8 mm (±9.3) after the workshop. Four areas of significant interobserver variability were identified, and a consensus was reached. Using a robust methodology, our cooperative group proposed an easily applicable, reproducible, and practice-validated guideline for the delineation of the pelvic CTV in prostate cancer, useful for implementation in daily practice and clinical trials.

Daily Head and Neck Treatment Assessment for Optimal Proton Therapy Planning Robustness.

Robust optimization in proton therapy ensures adequate target coverage; however, validation of fractional plan quality and setup uncertainty in patients has not been performed. We aimed to assess plan robustness on delivered head and neck proton plans classified into two categories: (1) primary only (PO) and (2) primary and neck nodal (PNN) coverage. Registration at the machine was utilized for daily CBCT to generate a synthetic CT. The dose for the clinical target volume (CTV) and organs at risk (OAR) was compared to the expected robustness bands using 3.5% range uncertainty and 3 mm vs. 5 mm setup uncertainty. The fractional deviation was defined as D95% and V100% outside of uncertainty constraints. About 203 daily fractions from 6 patients were included for analysis. The percentage of fractions that exceeded robustness calculations was greater in 3 mm as compared to 5 mm setup uncertainty for both CTV and OAR volumes. PO plans had clinically insignificant average fractional deviation, less than 1%, in delivered D95% and V100%. In comparison, PNN plans had up to 2.2% average fractional deviation in delivered V100% using 3 mm robustness. Given the need to balance dose accuracy with OAR sparing, we recommend the utilization of 3 mm setup uncertainty as an acceptable simulation of the dose delivered.

30 GY IN 4 STEREOTACTIC BODY RADIOTHERAPY (SBRT) FRACTIONS FOR COMPLEX SPINAL METASTASES: MATURE OUTCOMES SUPPORTING THIS NOVEL REGIMEN

Abstract We designed a 30 Gy in 4 fractions stereotactic body radiotherapy (SBRT) protocol, as an alternative option to our standard 2-fraction approach, for primarily large volume, multilevel, or previously radiated spinal metastases. We report imaging-based outcomes of this novel fractionation scheme. MATERIALS AND METHODS: Retrospective analysis of all patients who underwent 30 Gy/4 fractions from 2010-2021 identified from an institutional database. Primary outcomes were magnetic resonance-based vertebral compression fracture (VCF) and local failure (LF). RESULTS: We reviewed 245 treated segments in 116 patients. The median number of consecutive segments within the treatment volume was 2 (range, 1-6) and clinical target volume (CTV) was 126.2 cc (range, 10.4-863.5). Fifty-four percent had received at least one prior course of radiotherapy. The cumulative incidence of LF was 10.7% (95% CI 7.1-15.2) at 1 year and 16% (95% CI 11.5-21.2) at 2 years. The cumulative incidence of VCF was 7.3% (95% CI 4.4-11.2) at 1 and 11.2% (95% CI 7.5-15.8) at 2 years. On multivariable analysis, age ≥68 years (p=0.038), CTV volume ≥72 cc (p=0.021), and no prior surgery (p=0.021) predicted for VCF. The risk of VCF for CTV volumes &amp;lt;72 cc/≥72 cc was 1.8%/14.6% at 2 years. No case of radiation-induced myelopathy was observed. CONCLUSION: 30 Gy in 4 fractions was safe and efficacious despite a population at increased risk of toxicity. The lower risk of VCF in previously stabilized segments highlights the potential for a multi-modal treatment approach for complex metastases, especially for those with CTV volume ≥72 cc.

30 Gy in 4 Stereotactic Body Radiotherapy Fractions for Complex Spinal Metastases: Mature Outcomes Supporting This Novel Regimen.

We designed a 30 Gy in 4 fractions stereotactic body radiotherapy protocol, as an alternative option to our standard 2-fraction approach, for primarily large volume, multilevel, or previously radiated spinal metastases. We report imaging-based outcomes of this novel fractionation scheme. The institutional database was reviewed to identify all patients who underwent 30 Gy/4 fractions from 2010 to 2021. Primary outcomes were magnetic resonance-based vertebral compression fracture (VCF) and local failure per treated vertebral segment. We reviewed 245 treated segments in 116 patients. The median age was 64 years (range, 24-90). The median number of consecutive segments within the treatment volume was 2 (range, 1-6), and the clinical target volume (CTV) was 126.2 cc (range, 10.4-863.5). Fifty-four percent had received at least 1 previous course of radiotherapy, and 31% had previous spine surgery at the treated segment. The baseline Spinal Instability Neoplastic Score was stable, potentially unstable, and unstable for 41.6%, 51.8%, and 6.5% of segments, respectively. The cumulative incidence of local failure was 10.7% (95% CI 7.1-15.2) at 1 year and 16% (95% CI 11.5-21.2) at 2 years. The cumulative incidence of VCF was 7.3% (95% CI 4.4-11.2) at 1 year and 11.2% (95% CI 7.5-15.8) at 2 years. On multivariate analysis, age ≥68 years ( P = .038), CTV volume ≥72 cc ( P = .021), and no previous surgery ( P = .021) predicted an increased risk of VCF. The risk of VCF for CTV volumes <72 cc/≥72 cc was 1.8%/14.6% at 2 years. No case of radiation-induced myelopathy was observed. Five percent of patients developed plexopathy. 30 Gy in 4 fractions was safe and efficacious despite the population being at increased risk of toxicity. The lower risk of VCF in previously stabilized segments highlights the potential for a multimodal treatment approach for complex metastases, especially for those with a CTV volume of ≥72 cc.

PD15-08 PROSTATE BED DEFORMATIONS AND DOSIMETRIC IMPLICATIONS: AN EXPLORATORY ANALYSIS OF A PHASE II CLINICAL TRIAL (SCIMITAR)

You have accessJournal of UrologyCME1 Apr 2023PD15-08 PROSTATE BED DEFORMATIONS AND DOSIMETRIC IMPLICATIONS: AN EXPLORATORY ANALYSIS OF A PHASE II CLINICAL TRIAL (SCIMITAR) Tommy Jiang, Lauren Smith, Luca Valle, Leslie Ballas, John Nikitas, Michael Steinberg, Robert Reiter, Minsong Cao, and Amar Kishan Tommy JiangTommy Jiang More articles by this author , Lauren SmithLauren Smith More articles by this author , Luca ValleLuca Valle More articles by this author , Leslie BallasLeslie Ballas More articles by this author , John NikitasJohn Nikitas More articles by this author , Michael SteinbergMichael Steinberg More articles by this author , Robert ReiterRobert Reiter More articles by this author , Minsong CaoMinsong Cao More articles by this author , and Amar KishanAmar Kishan More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003262.08AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: One major challenge of postoperative radiotherapy is the deformable nature of the bladder and rectum. These changes can potentially lead to underdosing of the prostate bed and overdosing of the organs at risk (OARs: bladder and rectum). Our objective was to quantify the dosimetric impact of interfractional prostate bed and OAR deformation. METHODS: SCIMITAR (NCT03541850) was a prospective phase II clinical trial evaluating stereotactic body radiotherapy (SBRT) for post-prostatectomy patients. This analysis included men receiving CT-guided SBRT. All patients received five fractions of 6−6.8 Gy to the prostate bed. The clinical target volume (CTV) and OARs were retrospectively contoured on fractional CBCT images using MIMVista. Volumetric, shape (via the dice similarity coefficient [DSC]) and dosimetric changes were quantified. Student’s t-test was used to analyze the differences between planning and daily treatment outcomes RESULTS: 31 patients were eligible for this analysis. We found the CTV volume remained stable (median change 1.1%; IQR: -15.1%–16.1%), while the shape was highly deformable (DSC of 0.76 [IQR: 0.71–0.79]). The bladder and rectum exhibited similar changes with median volume change of 5.7% (IQR: -24.3%–51.0%) and 5.5% (IQR: -8.7%-21.9%) respectively and median DSC of 0.77 (IQR: 0.68–0.84) and 0.74 (IQR: 0.69–0.80) respectively. Notably, the CTV received less radiation than planned (volume receiving 95% of dose 93.2% vs 99.6%, p<0.01). Additionally, 39% (56/145) of total fractions and 52% (15/29) of patients met criteria for under coverage (volume receiving 95% of the dose <93%). The rectum received more radiation than planned on several dosimetric parameters (volume receiving 27.5 Gy increased from 15.4% to 21.0% [p = 0.009] and volume receiving 32.5 Gy increased from 6.0% to 10.9% [p = 0.006]) (Table 1). CONCLUSIONS: We found underdosing of the prostate CTV and overdosing of the rectum in a fair percentage of patients receiving postoperative radiation, despite modern radiotherapy planning and delivery techniques. While future work will correlate these dosimetric consequences with toxicity and efficacy, these data suggest that approaches to improving dose delivery, such as adaptive radiotherapy, may be beneficial. Source of Funding: AUA Medical Student Fellowship © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e421 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Tommy Jiang More articles by this author Lauren Smith More articles by this author Luca Valle More articles by this author Leslie Ballas More articles by this author John Nikitas More articles by this author Michael Steinberg More articles by this author Robert Reiter More articles by this author Minsong Cao More articles by this author Amar Kishan More articles by this author Expand All Advertisement PDF downloadLoading ...

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.

Mature Outcomes of Stereotactic Body Radiotherapy for Spinal Metastases with 30 Gy in 4 Fractions

<h3>Purpose/Objective(s)</h3> At our institution, 30 Gy in 4 spine stereotactic body radiotherapy (SBRT) fractions is typically delivered for larger volume when multiple segments are included in the treatment volume and/or for the retreatment of spinal metastases. We report MRI-based local failure (LF) and vertebral compression fracture (VCF) rates for patients (pts) treated with 30 Gy/4Fx of spine SBRT. <h3>Materials/Methods</h3> A retrospective analysis of all pts with spine metastases treated with 30 Gy/4Fx from 2010 to 2021 from an institutional registry was performed. Demographic, clinical, dosimetric, and radiological data were summarized, and the primary endpoint was the MRI-based LF rate. Secondary endpoints included the incidence of VCF and overall survival (OS). Kaplan Meier was used to calculate LF and VCF per segment and OS per patient. <h3>Results</h3> Were included 116 pts with 245 treated segments in this analysis. The median number of consecutive segments in the treatment volume was 3 (1-7), and the median clinical target volume (CTV) was 126 cc (range, 10-863). Kidney (25%), lung (20%), breast (19%), prostate (19%), and colon (10%) cancer were the most common primary histologic types. 38% of pts had oligometastatic disease and 24% spine metastases only. 15% (17/116) of the patients were treated with postoperative SBRT. 31% of segments were re-irradiated for conventional palliative radiation, and 26% prior SBRT, failures. 25% of segments had a baseline VCF, 46% epidural disease, and 53% paraspinal tumor extension. The median follow-up per patient was 18.5 (range, 0.1-61) and per segment 10.7 mos (range, 0.1-59). The LF rates at 12 and 24 mos were 10.7% (95% CI 7.1-15.2) and 16% (95% CI 11.5-21.2), and for VCF were 7.3% (95% CI 4.4-11.2) and 11.2% (95% CI 7.5-15.8), respectively. 60% of failures had an epidural, and 23% a paraspinal, component. Age <68y (HR=0.43, 95% CI 0.19-0.95, p=0.038), volume of CTV <72cc (HR=0.09, 95% CI 0.01-0.70, p=0.021), and prior surgical stabilization (HR=0.25, 95% CI 0.07-0.81, p=0.021) were protective predictors for VCF on multivariable analyses (MVA). In particular, the VCF rate at 24 mos was 1.8% for pts with CTV volume <72 vs 14.6% for ≥72cc. Median OS was 20.3 mos (95% CI 14.8-27.1). Low grade or no epidural disease (HR=0.42, 95% CI 0.21-0.84, p=0.014), paraspinal disease (HR=3.07, 95% CI 1.68-5.62, p<0.001) and kidney primary cancer (HR=2.43, 95% CI 1.08-5.44, p=0.031) were predictors for OS on MVA, with a trend for oligometastatic disease (HR=0.56, 95% CI 0.31-1.02, p=0.059). No radiation-induced myelopathy was observed. <h3>Conclusion</h3> This first report for 30 Gy/4Fx as a novel fractionation for spine SBRT suggests high rates of local control and a low rate of VCF, particularly for those target volumes with a CTV<72 cc. However, our rate of VCF in very large treatment volumes (≥72cc) is comparable to the SBRT-induced VCF literature, where optimal management remains an active area of investigation.

Potential Metastatic Distance of Lymph Nodes in Different Metastatic Patterns for Nasopharyngeal Carcinoma: Implications for Caudal Border of Elective Nodal Target Volume Delineation

<h3>Purpose/Objective(s)</h3> To investigate the potential metastatic distance of involved lymph nodes (LNs) which can reveal possible pathways of microscopic spread and determine the delineation of caudal border of clinical target volume (CTV) for elective nodal irradiation (ENI) in nasopharyngeal carcinoma (NPC). <h3>Materials/Methods</h3> A total of 1412 patients with pathologically-proven NPC between January 2010 and December 2020 were enrolled. The center points of caudal edge of the most caudally involved LN, lateral process of C1, hyoid bone, cricoid cartilage and cranial edge of sternal manubrium were marked on treatment planning CT scans of each patient. The metastatic distance of the most caudally involved LN, lengths of entire neck, level II, III and IV were determined. Metastatic patterns and their respective metastatic distances covering 95% of patients were analyzed. The metastatic distance covering 95% of patients with LN involvement in lower level is recommended as the caudal border of CTV for patients with involved LN in the upper level. Recommendations in this study were compared with consensus guidelines to propose modifications to caudal border of CTV. <h3>Results</h3> In 1412 patients, lengths of level II, III, IV and II + III ranged widely from 2.9-8.4, 1.6-5.5, 1.2-9.6 and 5.5-12.6 cm, accounting for 21%-62%, 9%-41%, 9%-59% and 41%-91% of the entire neck, respectively. A total of 1933 LNs were delineated, LN metastasis was step by step with 1% skipping rate. Six main metastatic patterns were Level II (498, 25.8%), RPLN + II (801, 41.4%), Level II + III/Va (111, 5.7%), RPLN + Level II + III/Va (327, 16.9%), Level II + III/Va + IV/Vb (58, 3.0%) and RPLN + Level II + III/Va + IV/Vb (119, 6.2%), with significantly different mean metastatic distances. Their maximum distance covering 95% patients were 6.0, 6.3, 8.8, 9.8, 12.8, and 13.7 cm, respectively, based on which, caudal borders for metastatic patterns N0, RPLN, Level II, RPLN + Level II, RPLN + Level II, Level II + III/Va, RPLN + Level II + III/Va were recommended. Compared with current recommendations based on anatomic landmarks, the caudal borders of CTV shifted upward in 175 (99.4%) N0 patients, 88 (98.9%) with metastatic RPLN only and all patients with Level II and RPLN + Level II node involvement by 3.2, 2.9, 6.1, and 5.1 cm. However, 9(15.5%) and 6(5.0%) of patients with level III node involvement had lower recommended caudal borders of ENI than cranial edge of sternal manubrium (Table 1). <h3>Conclusion</h3> Delineation of the caudal border of CTV based on anatomical markers is highly heterogeneous and unstable. This study suggests using the potential metastatic distance (representing the metastatic capacity) of LNs in the lower level as the caudal border of CTV when with involved LN in the upper level. It could reduce the CTV volume in most patients, leading to an expected significant reduction in acute and late toxicity. However, potential metastatic distance in some patients suggests a lower CTV caudal border, indicating the anatomical marker-cased recommendation are insufficient.

Clinical Feasibility of Commercial Artificial Intelligence-Based Auto Contouring of Target Volumes and Organs-at-Risk in Breast Cancer Patients

<h3>Purpose/Objective(s)</h3> Manual clinical target volume (CTV) and organ at-risk (OAR) segmentation for planning remains a significant component of physician workload. In addition, inter-physician segmentation variability can introduce uncertainty in planning process. While current atlas-based auto-segmentation has proven to be useful for contouring, it typically requires significant upfront time investment and is physician dependent. Recently, artificial-intelligence-based contouring have been made commercially available. These systems are physician-independent, and rely on machine learning rather than a user-selected atlas of patient datasets. In this study, we evaluated the potential benefits of a commercially available artificial intelligence-based auto contouring (AI-AC) system by comparing AI-AC generated and manually delineated contours for breast patients. <h3>Materials/Methods</h3> CTVs (ipsilateral breast) and OARs (contralateral breast, heart, lungs, esophagus, and spinal cord) were manually contouring (MC) on planning computed tomography scans of 10 breast cancer patients (5 patients received breast-conserving surgery). Commercial AI auto-contouring software (AI-Rad Companion Organs RT) was then used to generate the same target and risk volumes. Volumes were compared using quantitative metrics, including the Dice Similarity Coefficient (DSC), and mean distance agreement (MDA). <h3>Results</h3> Correlation between the AI-AC and MC generated volumes was strong for the evaluated OARs, with a mean DSC higher than 0.90 for all OARs except the esophagus (mean DSC 0.83 ± 0.09)). In addition, Comparison of CTV volumes also showed excellent results, with a mean DSC higher than 0.93. For the OARs, mean DSC values ranged from 0.98 ± 0.01 to 0.83 ± 0.09, while the mean MDA ranged from 0.68 ± 0.3 to 0.84 +0.54 mm to mm. [Similar results were achieved for the CTV, with the mean DSC ranging from 0.93 ± 0.03 to 0.94 ± 0.06 to 0.93, and mean MDA from 1.71 ± 0.91 mm to 1.76 ± 0.68 mm. AI-AC generated volumes were produced in approximately 2 min, while MC of the same volumes takes the physician an estimated 30 min. <h3>Conclusion</h3> The feasibility of commercial AI-AC in breast RT planning was demonstrated. Immediately on activation, the AI-AC system was able to produce volumes showing significant agreement with physician-generated volumes. While AI-AC-generated volumes may require minor edits by the physician, clinical efficiency is substantially improved. Furthermore, initial volumes created by AI-AC are physician-independent, and may help to improve contour consistency in clinic compared to strictly manual approaches.

Endorectal contact radiation boosting: Making the case for dose AND volume reporting

IntroductionThe various rectal endoluminal radiation techniques all have steep, but different, dose gradients. In rectal contact brachytherapy (CXB) doses are typically prescribed and reported to the applicator surface and not to the gross tumor volume (GTV), clinical target volume (CTV) or organs at risk (OAR), which is crucial to understand tumor response and toxicity rates. To quantify the above-described problem, we performed a dose modeling study using a fixed prescription dose at the surface of the applicator and varied tumor response scenarios. MethodsEndorectal ultrasound-based 3D-volume-models of rectal tumors and the rectal wall were used to simulate the delivered dose to GTV, CTV and the rectal wall layers, assuming treatment with Maastro HDR contact applicator for rectal cancer with a fixed prescription dose to the applicator surface (equivalent to 3 × 30 Gy CXB) and various response scenarios. ResultsAn identical prescribed dose to the surface of the applicator resulted in a broad range of doses delivered to the GTV, CTV and the uninvolved intestinal wall. For example, the equieffective dose in 2 Gy per fraction (EQD2) D90% of the GTV varied between 63 and 231 Gy, whereas the EQD2 D2cc of the rectal wall varied between 97 and 165 Gy. ConclusionDoses prescribed at the surface are not representative of the dose received by the tumor and the bowel wall. This stresses the relevance of dose reporting and prescription to GTV and CTV volumes and OAR in order to gain insight between delivered dose, local control and toxicity and to optimize treatment protocols.

Improving the accuracy and consistency of clinical target volume delineation for rectal cancer by an education program.

BACKGROUNDAccurate target volume delineation is the premise for the implementation of precise radiotherapy. Inadequate target volume delineation may diminish tumor control or increase toxicity. Although several clinical target volume (CTV) delineation guidelines for rectal cancer have been published in recent years, significant interobserver variation (IOV) in CTV delineation still exists among radiation oncologists. However, proper education may serve as a bridge that connects complex guidelines with clinical practice.AIMTo examine whether an education program could improve the accuracy and consistency of preoperative radiotherapy CTV delineation for rectal cancer.METHODSThe study consisted of a baseline target volume delineation, a 150-min education intervention, and a follow-up evaluation. A 42-year-old man diagnosed with stage IIIC (T3N2bM0) rectal adenocarcinoma was selected for target volume delineation. CTVs obtained before and after the program were compared. Dice similarity coefficient (DSC), inclusiveness index (IncI), conformal index (CI), and relative volume difference [ΔV (%)] were analyzed to quantitatively evaluate the disparities between the participants’ delineation and the standard CTV. Maximum volume ratio (MVR) and coefficient of variation (CV) were calculated to assess the IOV. Qualitative analysis included four common controversies in CTV delineation concerning the upper boundary of the target volume, external iliac area, groin area, and ischiorectal fossa.RESULTSOf the 18 radiation oncologists from 10 provinces in China, 13 completed two sets of CTVs. In quantitative analysis, the average CTV volume decreased from 809.82 cm3 to 705.21 cm3 (P = 0.001) after the education program. Regarding the indices for geometric comparison, the mean DSC, IncI, and CI increased significantly, while ΔV (%) decreased remarkably, indicating improved agreement between participants’ delineation and the standard CTV. Moreover, an 11.80% reduction in MVR and 18.19% reduction in CV were noted, demonstrating a smaller IOV in delineation after the education program. Regarding qualitative analysis, the greatest variations in baseline were observed at the external iliac area and ischiorectal fossa; 61.54% (8/13) and 53.85% (7/13) of the participants unnecessarily delineated the external iliac area and the ischiorectal fossa, respectively. However, the education program reduced these variations.CONCLUSIONWide variations in CTV delineation for rectal cancer are present among radiation oncologists in mainland China. A well-structured education program could improve delineation accuracy and reduce IOVs.