[Advances in research on organ-at-risk protection in pelvic tumor external beam radiotherapy].

The simultaneous objectives of destroying tumor cells while protecting normal pelvic organs present a dual clinical and technical challenge within the realm of pelvic tumor radiotherapy. This article reviews the latest literatures, focusing on technological innovations in key aspects of radiotherapy such as positioning, planning, and delivery. These include positioning fixation techniques, organ-at-risk avoidance irradiation, non-coplanar irradiation techniques, as well as organ displacement protection and image-guided adaptive techniques. It summarizes and discusses the research progress made in the protection of critical organs during pelvic tumor radiotherapy. The paper emphasizes technological advancements in the protection of critical organs throughout the processes of radiotherapy positioning, planning, and implementation, aiming to provide references for further research on the protection of critical organs in the external irradiation treatment of pelvic tumors.

Incidence and Characterization of Rectal Complications From Fecal Management Systems.

BACKGROUND: Fecal management systems have become ubiquitous in hospitalized patients with fecal incontinence or severe diarrhea, especially in the setting of perianal wounds. Although fecal management system use has been shown to be safe and effective in initial series, case reports of rectal ulceration and severe bleeding have been reported, with a relative paucity of clinical safety data in the literature. OBJECTIVE: The purpose of this study was to determine the rate of rectal complications attributable to fecal management systems, as well as to characterize possible risk factors and appropriate management strategies for such complications. DESIGN: This was a retrospective cohort study. SETTINGS: The study was conducted at a large academic medical center. PATIENTS: All medical and surgical patients who underwent fecal management system placement from December 2014 to March 2017 were included. MAIN OUTCOME MEASURES: We measured any rectal complication associated with fecal management system use, defined as any rectal injury identified after fecal management system use confirmed by lower endoscopy. RESULTS: A total of 629 patients were captured, with a median duration of fecal management system use of 4 days. Overall, 8 patients (1.3%) experienced a rectal injury associated with fecal management system use. All of the patients who experienced a rectal complication had severe underlying comorbidities, including 2 patients on dialysis, 1 patient with cirrhosis, and 3 patients with a recent history of emergent cardiac surgery. In 3 patients the bleeding resolved spontaneously, whereas the remaining 5 patients required intervention: transanal suture ligation (n = 2), endoscopic clip placement (n = 1), rectal packing (n = 1), and proctectomy in 1 patient with a history of pelvic radiotherapy. LIMITATIONS: The study was limited by its retrospective design and single institution. CONCLUSIONS: This is the largest study to date evaluating rectal complications from fecal management system use. Although rectal injury rates are low, they can lead to serious morbidity. Advanced age, severe comorbidities, pelvic radiotherapy, and anticoagulation status or coagulopathy are important factors to consider before fecal management system placement. See Video Abstract at http://links.lww.com/DCR/B698. INCIDENCIA Y CARACTERIZACIN DE LAS COMPLICACIONES RECTALES DE LOS SISTEMAS DE MANEJO FECAL: ANTECEDENTES:Los sistemas de manejo fecal se han vuelto omnipresentes en pacientes hospitalizados con incontinencia fecal o diarrea severa, especialmente en el contexto de heridas perianales. Aunque se ha demostrado que el uso del sistema de tratamiento fecal es seguro y eficaz en la serie inicial, se han notificado casos de ulceración rectal y hemorragia grave, con una relativa escasez de datos de seguridad clínica en la literatura.OBJETIVO:Determinar la tasa de complicaciones rectales atribuibles a los sistemas de manejo fecal. Caracterizar los posibles factores de riesgo y las estrategias de manejo adecuadas para tales complicaciones.DISEÑO:Estudio de cohorte retrospectivo.ENTORNO CLINICO:Centro médico académico de mayor volumen.PACIENTES:Todos los pacientes médicos y quirúrgicos que se sometieron a la colocación del sistema de manejo fecal desde diciembre de 2014 hasta marzo de 2017.PRINCIPALES MEDIDAS DE VALORACION:Cualquier complicación rectal asociada con el uso del sistema de manejo fecal, definida como cualquier lesión rectal identificada después del uso del sistema de manejo fecal confirmada por endoscopia baja.RESULTADOS:Se identificaron un total de 629 pacientes, con una duración media del uso del sistema de manejo fecal de 4,0 días. En general, 8 (1,3%) pacientes desarrollaron una lesión rectal asociada con el uso del sistema de manejo fecal. Todos los pacientes que mostraron una complicación rectal tenían comorbilidades subyacentes graves, incluidos dos pacientes en diálisis, un paciente con cirrosis y tres pacientes con antecedentes recientes de cirugía cardíaca emergente. En tres pacientes el sangrado se resolvió espontáneamente, mientras que los cinco pacientes restantes requirieron intervención: ligadura de sutura transanal (2), colocación de clip endoscópico (1), taponamiento rectal (1) y proctectomía en un paciente con antecedentes de radioterapia pélvica.LIMITACIONES:Diseño retrospectivo, institución única.CONCLUSIONES:Este es el estudio más grande hasta la fecha que evalúa las complicaciones rectales del uso del sistema de manejo fecal. Si bien las tasas de lesión rectal son bajas, pueden provocar una morbilidad grave. La edad avanzada, las comorbilidades graves, la radioterapia pélvica y el estado de anticoagulación o coagulopatía son factores importantes a considerar antes de la colocación del sistema de manejo fecal. Consulte Video Resumen en http://links.lww.com/DCR/B698.

Post-operative small pelvic intensity-modulated radiation therapy for early-stage cervical cancer with intermediate-risk factors: efficacy and toxicity.

OBJECTIVE: The aim of the present study was to retrospectively evaluate the toxicity and efficacy of post-operative small pelvic intensity-modulated radiotherapy in early-stage cervical cancer patients with intermediate-risk factors. METHODS: Between 2012 and 2016, 151 patients who had cervical cancer (International Federation of Gynecology and Obstetrics stage I-IIA) with intermediate-risk factors were treated with post-operative small pelvic intensity-modulated radiotherapy. The median dose of 50.4 Gy in 28 fractions with small pelvic intensity-modulated radiotherapy was prescribed to the planning target volume. The intensity-modulated radiotherapy technique used was conventional fixed-field intensity-modulated radiotherapy or helical tomotherapy. RESULTS: The median follow-up was 37 months. The 3-year disease-free survival and overall survival rates were 89 and 96%, respectively. A total of 144 patients (95.3%) were alive at the last follow-up. In total, 6 patients (3.9%) had recurrence: locoregional recurrence in 3 patients (2%), distant metastasis in 2 (1.3%), and both in 1 (0.6%). Diarrhoea was the most common acute toxicity. There were no patients suffering from acute or late grade ≥ 3 toxicity. Only 4 patients (2.6%) had late grade 2 toxicities. CONCLUSIONS: For early-stage cervical cancer patients with intermediate-risk factors, post-operative small pelvic intensity-modulated radiotherapy was safe and well tolerated. The rates of acute and late toxicities were quite satisfactory.

A randomized controlled trial to assess operator radiation exposure from cardiac catheterization procedures using RAD BOARD® with standard pelvic shielding versus standard pelvic shielding alone.

OBJECTIVE: To study radiation exposure to the primary operator during diagnostic cardiac catheterizations using a radio-dense RAD BOARD® radial access arm board. BACKGROUND: The use of radial access for catheterization in the United States has increased from 1% in 2007 to 41% in 2018. Compared to femoral access, operator radiation exposure from radial access is similar or higher. The RAD BOARD radio-dense radial access arm board has been marketed as reducing radiation to operators by 44%. MATERIALS AND METHODS: We randomized 265 patients undergoing catheterization via right radial access to standard pelvic lead drape shielding (nonboard group) versus RAD BOARD in addition to pelvic drape (board group). Operator radiation exposure was measured using Landauer Microstar nanoDot™ badges worn by the operator. RESULTS: Board and nonboard groups were similar with respect to demographic and procedural variables. Mean operator dose per case was higher in the board group (.65mSieverts) than in the nonboard group (.56mSieverts, P < 0.0001). In sub-group analyses, radiation doses were higher in the board group compared to the nonboard group in patients across all body mass index groups (P < 0.03). In multivariate analysis, operator dose correlated with use of the RAD BOARD more closely than any other variable (P < 0.001). Post hoc analysis of the table setup with RAD BOARD revealed that use of RAD BOARD prevented placement of a shield normally inserted into the top of the standard below-table shield. CONCLUSION: RAD BOARD with the pelvic shield was associated with higher radiation exposure to the operator compared with pelvic shield alone, likely due to inability to use standard radiation shielding along with the RAD BOARD.

Incorporation of whole pelvic radiation into treatment of stage IVB cervical cancer: A novel treatment strategy.

OBJECTIVES: Chemotherapy is the standard treatment in stage IVB cervical cancer (CC). However, given that many women have a significant pelvic disease burden, whole pelvic radiation (WPR) in addition to chemotherapy for primary treatment may have utility. The aim of this study was to compare the overall survival (OS) and complication rates between women who received both WPR and chemotherapy (CT) versus CT alone in the management of stage IVB CC. METHODS: A multi-institutional, IRB-approved, retrospective review of patients (pts) with stage IVB CC, diagnosed between 2005 and 2015, was performed. Descriptive statistics of the demographic, oncologic, and treatment characteristics were performed. OS was estimated using the Kaplan Meier method. RESULTS: A total of 126 pts met inclusion criteria. Thirty one patients elected for hospice care at diagnosis and were excluded from further analysis. In the remaining population, median age was 53 yrs. The majority (72%) had squamous cell carcinoma and 82% had FIGO grade 2 or 3 tumors. Thirty four patients (35.8%) received WPR in addition to CT as a part of planned primary therapy and 64.2% (n = 61) received CT alone, with 88.2% and 80.3% receiving a cisplatin-based chemotherapy regimen, respectively. The OS was significantly longer in the WPR with CT group (41.6 vs 17.6 mo, p < 0.01). The rates of ureteral obstruction, vaginal bleeding, pelvic infection, pelvic pain, and fistula were not significantly different between the 2 groups (all p > 0.05). CONCLUSION: This study found WPR in addition to CT gives a significant OS benefit. Further study is warranted to determine which subgroups may benefit the most from this novel treatment strategy.

Definitive radiotherapy consisting of whole pelvic radiotherapy with no central shielding and CT-based intracavitary brachytherapy for cervical cancer: feasibility, toxicity, and oncologic outcomes in Japanese patients.

BACKGROUND: This prospective study investigated the feasibility, toxicity, and oncologic outcomes of definitive radiotherapy (RT) consisting of whole pelvic radiotherapy with no central shielding (noCS-WPRT) and CT-based intracavitary brachytherapy (ICBT) in Japanese patients with cervical cancer. METHODS: Patients with cervical cancer of FIGO stages IB1-IVA were eligible. The treatment protocol consisted of noCS-WPRT of 45 Gy in 25 fractions and CT-based high dose-rate ICBT of 15 or 20 Gy in 3 or 4 fractions prescribed at point A. The prescribed ICBT dose was decreased if the manual dwell time/position optimization failed to meet organs-at-risk constraints. Graphical optimization and additional interstitial needles were not applied. RESULTS: We enrolled 40 patients. FIGO stages were IB1: 11, IB2: 13, IIA2: 1, IIB: 11, IIIB: 3, and IVA: 1. Median (range) pretreatment tumor diameter was 47 (14-81) mm. Point A doses were decreased in 19 of 153 ICBT sessions (12%). The median follow-up duration was 33 months. The 2-year rates of pelvic control, local control (LC), and progression-free survival were 83%, 85%, and 75%, respectively. Pre-ICBT tumor diameter, high-risk clinical target volume (HR-CTV), total HR-CTV D90, and overall treatment time (OTT) significantly affected LC. Late adverse events (grade ≥ 3) were observed in 3 patients (2 in the bladder, 1 in the rectum). CONCLUSIONS: Definitive RT consisting of noCS-WPRT and CT-based ICBT was feasible for Japanese patients with cervical cancer. To further improve LC, additional interstitial needles for patients with a large HR-CTV and shorter OTT should be considered.

Robotic Vesicovaginal Fistula Repair.

STUDY OBJECTIVE: To illustrate a technique of robotic vesicovaginal fistula repair in a patient with a previous history of pelvic radiation therapy and multiple abdominal surgeries. DESIGN: Stepwise demonstration of the technique with narrated video footage. SETTING: This 59-year-old woman presented with vesicovaginal fistula. She had a history of rectosigmoidectomy followed by pelvic radiotherapy for stage III colon cancer 23 years earlier and subsequent robotic hysterectomy, bilateral salpingo-oophorectomy, and omentectomy with bilateral pelvic and para-aortic lymphadenectomy for stage II mixed cell endometrial carcinoma, which required surgical reintervention because of a pelvic hematoma and complete vaginal cuff dehiscence. INTERVENTIONS: We performed a robotic approach to vesicovaginal fistula with several key steps to repair the fistula and maintain the integrity of the abdominopelvic structures: (1) careful bowel adhesiolysis involving multiple segments of the intestine to the abdominal and pelvic peritoneum; (2) cystotomy with vaginal probe guidance; (3) fistulectomy by monopolar scissors after ureteral orifice visualization; (4) dissection of the retropubic space of Retzius, relieving bladder tension; (5) transverse sutures to coapt the raw surfaces on the vaginal side and the bladder in 2 layers with minimal tension; and (6) transurethral instillation of methylene blue into the bladder. CONCLUSIONS: Traditionally, patients with vesicovaginal fistula after pelvic radiation therapy and multiple abdominal surgeries are managed by laparotomy. This video demonstrates a feasible robotic approach to vesicovaginal fistula repair, with superior imaging affording 3-dimensional visualization and stabilization of instruments, allowing wrist-like movements.

Dual benefit of supplementary oral 5-aminolevulinic acid to pelvic radiotherapy in a syngenic prostate cancer model.

BACKGROUND: Normal tissue damage caused by radiotherapy remains the largest dose-limiting factor in radiotherapy for cancer. Therefore, the aim of this study was to investigate the supplementary oral 5-aminolevulinic acid (ALA) to standard radiation therapy as a novel radioprotective approach that would not compromise the antitumor effect of radiation in normal rectal and bladder mucosa in a syngenic prostate cancer (PCa) model. METHODS: To evaluate the radiosensitizing effect of ALA in vitro, clonogenic survival assays were performed in DU145, PC3, and MyC-CaP cell lines. To evaluate the effect of ALA in vivo a single dose (25 Gy) of radiation with or without ALA was given to healthy mice. Next, a syngenic PCa model of MyC-CaP cells in FVB mice was created, and multiple doses (12 Gy total) of radiation were administered to the mouse pelvic area with or without ALA administration. Resected tumors, recta, and urinary bladders were immunostained with antibodies against Ki-67, γ-H2AX, CD204, and uroplakin-III. Total RNA levels in recta and urinary bladders were analyzed via RT2 Profiler polymerase chain reaction (PCR) arrays related to "Stress & Toxicity PathwayFinder," "Mitochondria," and "Inflammasomes." RESULTS: The addition of in vitro single or in vivo repeated administration of exogenous ALA acted as a radiosensitizer for PCa cells. Rectal toxicity was characterized by histological changes including loss of surface epithelium, fibrosis, severe DNA damage, and the aggregation of M2 macrophages. Urinary bladder toxicity was characterized by bladder wall thickening and urothelium denuding. The higher dose (300 mg/kg/day) of ALA exerted a better radioprotective profile than the lower dose (30 mg/kg/day) in normal recta and urinary bladders. Out of the 252 genes tested, 35 (13.4%) were detected as relevant genes which may be involved in the radioprotective role of ALA administration. These included interleukin-1a (IL-1a), IL-1b, IL-12, chemokine (C-X-C motif) ligand 1 (CXCL1), CXCL3, and NLRP3. CONCLUSIONS: Our study provides novel and comprehensive insights into the dual benefits including radiosensitizing PCa tumor tissues and radioprotection of normal pelvic organs from radiation therapy. Knowledge of the underlying mechanism will facilitate the search for optimal treatment parameters for supplemental oral ALA during radiotherapy for PCa.

Radiation Dose for Pediatric CT: Comparison of Pediatric versus Adult Imaging Facilities.

Background The American College of Radiology Dose Index Registry for CT enables evaluation of radiation dose as a function of patient characteristics and examination type. The hypothesis of this study was that academic pediatric CT facilities have optimized CT protocols that may result in a lower and less variable radiation dose in children. Materials and Methods A retrospective study of doses (mean patient age, 12 years; age range, 0-21 years) was performed by using data from the National Radiology Data Registry (year range, 2016-2017) (n = 239 622). Three examination types were evaluated: brain without contrast enhancement, chest without contrast enhancement, and abdomen-pelvis with intravenous contrast enhancement. Three dose indexes-volume CT dose index (CTDIvol), size-specific dose estimate (SSDE), and dose-length product (DLP)-were analyzed by using six different size groups. The unequal variance t test and the F test were used to compare mean dose and variances, respectively, at academic pediatric facilities with those at other facility types for each size category. The Bonferroni-Holm correction factor was applied to account for the multiple comparisons. Results Pediatric radiation dose in academic pediatric facilities was significantly lower, with smaller variance for all brain, 42 of 54 (78%) chest, and 48 of 54 (89%) abdomen-pelvis examinations across all six size groups, three dose descriptors, and when compared with that at the other three facilities. For example, abdomen-pelvis SSDE for the 14.5-18-cm size group was 3.6, 5.4, 5.5, and 8.3 mGy, respectively, for academic pediatric, nonacademic pediatric, academic adult, and nonacademic adult facilities (SSDE mean and variance P < .001). Mean SSDE for the smallest patients in nonacademic adult facilities was 51% (6.1 vs 11.9 mGy) of the facility's adult dose. Conclusion Academic pediatric facilities use lower CT radiation dose with less variation than do nonacademic pediatric or adult facilities for all brain examinations and for the majority of chest and abdomen-pelvis examinations. © RSNA, 2019 See also the editorial by Strouse in this issue.

Does external beam radiation boost to pelvic lymph nodes improve outcomes in patients with locally advanced cervical cancer?

BACKGROUND: Current recommendation for locally advanced cervical cancer includes pelvic external beam radiation therapy (EBRT) with concurrent chemotherapy followed by brachytherapy. Involvement of pelvic lymph nodes is an important prognostic factor in locally advanced cervical cancer and recurrence commonly occurs despite definitive treatment. To date, there is no standard guideline on whether an EBRT boost should be applied to involved pelvic lymph nodes. Our study aims to assess if pelvic EBRT boost would reduce recurrence, benefit survival, and affect associated toxicities. METHODS: We conducted a retrospective review of locally advanced cervical cancer cases treated with definitive treatment at our institution. Involvement of pelvic lymph nodes were assessed on CT, MRI (> 10 mm or suspicious features) or PET scan (SUVmax > 2.5). EBRT dose ranged from 45 to 50.4 Gy with nodal boost ranging from 3.6-19.8 Gy. RESULTS: Between 2008 to 2015, 139 patients with locally advanced cervical cancer underwent treatment. Sixty-seven patients had positive pelvic lymph nodes, of which 53.7% received a nodal boost. Five-year recurrence free survival was 48.6% with vs. 64.5% without nodal boost (P = 0.169) and 5-year overall survival in those with positive pelvic lymph nodes was 74.3% with vs. 80.6% without nodal boost (P = 0.143). There was no significant difference in toxicity with nodal boost. CONCLUSIONS: EBRT boost to pelvic lymph nodes does not reduce recurrence or improve survival in locally advanced cervical cancer with lymph node involvement at diagnosis.

Early and late side effects, dosimetric parameters and quality of life after proton beam therapy and IMRT for prostate cancer: a matched-pair analysis.

Purpose: To compare early and late toxicities, dosimetric parameters and quality of life (QoL) between conventionally fractionated proton beam therapy (PBT) and intensity-modulated radiation therapy (IMRT) in prostate cancer (PCA) patients. Methods: Eighty-eight patients with localized PCA treated between 2013 and 2017 with either definitive PBT (31) or IMRT (57) were matched using propensity score matching on PCA risk group, transurethral resection of the prostate, prostate volume, diabetes mellitus and administration of anticoagulants resulting in 29 matched pairs. Early and late genitourinary (GU) and gastrointestinal (GI) toxicities according to Common Terminology Criteria for Adverse Events (CTCAE) and QoL based on EORTC-QLQ-C30/PR25 questionnaires were collected prospectively until 12 months after radiotherapy (RT). Associations between toxicities and dose-volume parameters in corresponding organs at risk (OARs) were modeled by logistic regression. Results: There were no significant differences in GI and GU toxicities between both treatment groups except for late urinary urgency, which was significantly lower after PBT (IMRT: 25.0%, PBT: 0%, p = .047). Late GU toxicities and obstruction grade ≥2 were significantly associated with the relative volume of the anterior bladder wall receiving 70 Gy and the entire bladder receiving 60 Gy, respectively. The majority of patients in both groups reported high functioning and low symptom scores for the QoL questionnaires before and after RT. No or little changes were observed for most items between baseline and 3 or 12 months after RT, respectively. Global health status increased more at 12 months after IMRT (p = .040) compared to PBT, while the change of constipation was significantly better at 3 months after PBT compared to IMRT (p = .034). Conclusions: Overall, IMRT and PBT were well tolerated. Despite the superiority of PBT in early constipation and IMRT in late global health status compared to baseline, overall QoL and the risks of early and late GU and GI toxicities were similar for conventionally fractionated IMRT and PBT.

Successful use of tissue expander and pelvic sling to exclude small bowel for high-dose pelvic irradiation.

OBJECTIVE: Our study seeks to describe our surgical technique of the use of a tissue expander and a pelvic sling in order to perform high-dose pelvic irradiation without incurring radiation toxicity to the small bowel. High-dose radiation therapy for pelvic tumours comes at a risk of radiation toxicity to the small bowel. Our study discusses our novel surgical technique of compartmentalising the abdomen and the pelvis through the use of a tissue expander and pelvic sling to avoid small bowel radiation toxicity. METHODS: We present a patient with an unresectable sacral chordoma. We describe our surgical technique incorporating both a tissue expander and an absorbable pelvic mesh sling to successfully compartmentalise the abdomen from the pelvis. RESULTS: The patient underwent an uneventful surgical procedure to place the tissue expander within the pelvis and deploy the pelvic mesh sling. Following surgery, a separation of at least 8 cm was achieved between bowel loops and the tumour. A dose of 70 Gy delivered over 35 fractions using intensity modulated radiotherapy (IMRT) was administered to the sacral chordoma, whilst managing to constrain the maximum bowel dose to 35.7 Gy. Surgery to remove the tissue expander was uneventful. The patient has not suffered any small bowel irradiation toxicity. CONCLUSIONS: Our technique to exclude small bowel from the pelvis is effective and safe. This technique not only can be applied in the setting of unresectable sacral chordomas but also may be applicable to other pelvic cancers which require radiation therapy.

Clinical outcomes following conventional external beam radiotherapy boost in Japanese patients with cervical cancer who are ineligible for intracavitary brachytherapy.

OBJECTIVE: While external beam radiotherapy boost has been one of the standard management options for locally advanced cervical cancer that is not treatable with intracavitary brachytherapy, its efficacy remains unclear. We assessed clinical outcomes in Japanese patients with cervical cancer who underwent external beam radiotherapy alone and identified related prognostic factors. METHODS: Patients treated with definitive external beam radiotherapy for cervical cancer unsuitable for intracavitary brachytherapy, including whole pelvic irradiation and external beam radiotherapy boost, were retrospectively examined. The endpoints were progression-free survival, overall survival and adverse events. Additionally, various patient-, tumor- and treatment-specific factors were evaluated to identify significant predictors of progression-free survival. RESULTS: The study included 37 patients; 3 (8%), 5 (14%), 17 (46%) and 12 (32%) had clinical International Federation of Gynecology and Obstetrics (FIGO) stages I, II, III and IVA, respectively. A total radiation dose of 56-70.2 Gy was administered (84% of patients received 59.4-60.4 Gy). The median follow-up period after radiotherapy was 17 (range, 2-84) months. The progression-free survival rates at 1 and 2 years were 45 and 29%, respectively; the corresponding overall survival rates were 74 and 43%, respectively. On univariate and multivariate analyses of progression-free survival at 2 years, International Federation of Gynecology and Obstetrics stage IVA and a maximum primary tumor diameter >5 cm were associated with significantly worse outcomes (P = 0.026 and P = 0.027, respectively). CONCLUSION: Approximately 70% of patients with cervical cancer treated with external beam radiotherapy boost instead of intracavitary brachytherapy experienced disease progression within 2 years. These results stress the necessity of devising alternative non-intracavitary brachytherapy treatment approaches, particularly for patients with International Federation of Gynecology and Obstetrics stage IVA and bulky primary tumors.

Development and evaluation of a novel MR-compatible pelvic end-to-end phantom.

MR-only treatment planning and MR-IGRT leverage MRI's powerful soft tissue contrast for high-precision radiation therapy. However, anthropomorphic MR-compatible phantoms are currently limited. This work describes the development and evaluation of a custom-designed, modular, pelvic end-to-end (PETE) MR-compatible phantom to benchmark MR-only and MR-IGRT workflows. For construction considerations, subject data were assessed for phantom/skeletal geometry and internal organ kinematics to simulate average male pelvis anatomy. Various materials for the bone, bladder, and rectum were evaluated for utility within the phantom. Once constructed, PETE underwent CT-SIM, MR-Linac, and MR-SIM imaging to qualitatively assess organ visibility. Scans were acquired with various bladder and rectal volumes to assess component interactions, filling capabilities, and filling reproducibility via volume and centroid differences. PETE simulates average male pelvis anatomy and comprises an acrylic body oval (height/width = 23.0/38.1 cm) and a cast-mold urethane skeleton, with silicone balloons simulating bladder and rectum, a silicone sponge prostate, and hydrophilic poly(vinyl alcohol) foam to simulate fat/tissue separation between organs. Access ports enable retrofitting the phantom with other inserts including point/film-based dosimetry options. Acceptable contrast was achievable in CT-SIM and MR-Linac images. However, the bladder was challenging to distinguish from background in CT-SIM. The desired contrast for T1-weighted and T2-weighted MR-SIM (dark and bright bladders, respectively) was achieved. Rectum and bone exhibited no MR signal. Inputted volumes differed by <5 and <10 mL from delineated rectum (CT-SIM) and bladder (MR-SIM) volumes. Increasing bladder and rectal volumes induced organ displacements and shape variations. Reproduced volumes differed by <4.5 mL, with centroid displacements <1.4 mm. A point dose measurement with an MR-compatible ion chamber in an MR-Linac was within 1.5% of expected. A novel, modular phantom was developed with suitable materials and properties that accurately and reproducibly simulate status changes with multiple dosimetry options. Future work includes integrating more realistic organ models to further expand phantom options.

Dosimetric evaluation of an atlas-based synthetic CT generation approach for MR-only radiotherapy of pelvis anatomy.

PURPOSE: To investigate the potential of an atlas-based approach in generation of synthetic CT for pelvis anatomy. METHODS: Twenty-three matched pairs of computed tomography (CT) and magnetic resonance imaging (MRI) scans were selected from a pool of prostate cancer patients. All MR scans were preprocessed to reduce scanner- and patient-induced intensity inhomogeneities and to standardize their intensity histograms. Ten (training dataset) of 23 pairs were then utilized to construct the coregistered CT-MR atlas. The synthetic CT for a new patient is generated by appropriately weighting the deformed atlas of CT-MR onto the new patient MRI. The training dataset was used as an atlas to generate the synthetic CT for the rest of the patients (test dataset). The mean absolute error (MAE) between the deformed planning CT and synthetic CT was computed over the entire CT image, bone, fat, and muscle tissues. The original treatment plans were also recomputed on the new synthetic CTs and dose-volume histogram metrics were compared. The results were compared with a commercially available synthetic CT Software (MRCAT) that is routinely used in our clinic. RESULTS: MAE errors (±SD) between the deformed planning CT and our proposed synthetic CTs in the test dataset were 47 ± 5, 116 ± 12, 36 ± 6, and 47 ± 5 HU for the entire image, bone, fat, and muscle tissues respectively. The MAEs were 65 ± 5, 172 ± 9, 43 ± 7, and 42 ± 4 HU for the corresponding tissues in MRCAT CT. The dosimetric comparison showed consistent results for all plans using our synthetic CT, deformed planning CT and MRCAT CT. CONCLUSION: We investigated the potential of a multiatlas approach to generate synthetic CT images for the pelvis. Our results demonstrate excellent results in terms of HU value assignment compared to the original CT and dosimetric consistency.

Impact of daily soft-tissue image guidance to prostate on pelvic lymph node (PLN) irradiation for prostate patients receiving SBRT.

PURPOSE: To determine the impact of using fiducial match for daily image-guidance on pelvic lymph node (PLN) coverage for prostate cancer patients receiving stereotactic body radiation therapy (SBRT). METHODS: Thirty patients underwent SBRT treatment to the prostate and PLN from 2014 to 2016. Each patient received either 800cGy × 5 or 500cGy × 5 to the prostate and 500cGy × 5 to the PLN. A 5 mm clinical target volume (CTV)-to-planning target volume (PTV) margin around the PLN was used for planning. Two registrations with planning computed tomography (PCT) for each of the daily cone beam CTs (CBCTs) were performed: a rigid registration to fiducials and to the bony anatomy. The average translational difference between fiducial and bony match as well as percentage of fractions with differences > 5mm were calculated. Changes in bladder and rectal volume as well as center-of-mass (COM) position from simulation parameters, and their correlation with translational difference were also evaluated. The dosimetric impact of the translational differences was calculated by shifting the plan isocenter. RESULTS: The average translational difference between fiducial and bony match was 0.06 ± 0.82, 2.1 ± 4.1, -2.8 ± 4.3, and 5.5 ± 4.2 mm for lateral, vertical, longitudinal, and vector directions. The average change in bladder and rectal volume from simulation was -67.2 ± 163.04 cc (-12 ± 52%) and -1.6 ± 18.75 (-2 ± 30%) cc. The average change in COM of bladder from the simulation position was 0.34 ± 2.49, 4.4 ± 8.1, and -3.9 ± 7.5 mm along the LR, AP, and SI directions. The corresponding COM change for the rectum was 0.17 ± 1.9, 1.34 ± 3.5, and -0.6 ± 5.2 mm. CONCLUSIONS: The 5 mm margin covered ~75% of fractions receiving PLN irradiation with SBRT, daily CBCT and fiducial-guided setup. The dosimetric impact on PLN coverage was significant in 19% of fractions or 25% of patients. A larger translational shift was due to variation in rectal volume and changes in COM position of the bladder and rectum. A consistent bladder positioning and/or rectum filling compared with presimulation volume were essential for adequate coverage of PLN in a hypofractionated treatment regime.

Impact of patient centering in CT on organ dose and the effect of using a positioning compensation system: Evidence from OSLD measurements in postmortem subjects.

The purpose of this study was to investigate the frequency and impact of vertical mis-centering on organ doses in computed tomography (CT) exams and evaluate the effect of a commercially available positioning compensation system (PCS). Mis-centering frequency and magnitude was retrospectively measured in 300 patients examined with chest-abdomen-pelvis CT. Organ doses were measured in three postmortem subjects scanned on a CT scanner at nine different vertical table positions (maximum shift ± 4 cm). Organ doses were measured with optically stimulated luminescent dosimeters inserted within organs. Regression analysis was performed to determine the correlation between organ doses and mis-centering. Methods were repeated using a PCS that automatically detects the table offset to adjust tube current output accordingly. Clinical mis-centering was >1 cm in 53% and 21% of patients in the vertical and lateral directions, respectively. The 1-cm table shifts resulted in organ dose differences up to 8%, while 4-cm shifts resulted in organ dose differences up to 35%. Organ doses increased linearly with superior table shifts for the lung, colon, uterus, ovaries, and skin (R2  = 0.73-0.99, P < 0.005). When the PCS was utilized, organ doses decreased with superior table shifts and dose differences were lower (average 5%, maximum 18%) than scans performed without PCS (average 9%, maximum 35%) at all table shifts. Mis-centering occurs frequently in the clinic and has a significant effect on patient dose. While accurate patient positioning remains important for maintaining optimal imaging conditions, a PCS has been shown to reduce the effects of patient mis-centering.

Machine Learning Techniques Applied to Dose Prediction in Computed Tomography Tests.

Increasingly more patients exposed to radiation from computed axial tomography (CT) will have a greater risk of developing tumors or cancer that are caused by cell mutation in the future. A minor dose level would decrease the number of these possible cases. However, this framework can result in medical specialists (radiologists) not being able to detect anomalies or lesions. This work explores a way of addressing these concerns, achieving the reduction of unnecessary radiation without compromising the diagnosis. We contribute with a novel methodology in the CT area to predict the precise radiation that a patient should be given to accomplish this goal. Specifically, from a real dataset composed of the dose data of over fifty thousand patients that have been classified into standardized protocols (skull, abdomen, thorax, pelvis, etc.), we eliminate atypical information (outliers), to later generate regression curves employing diverse well-known Machine Learning techniques. As a result, we have chosen the best analytical technique per protocol; a selection that was thoroughly carried out according to traditional dosimetry parameters to accurately quantify the dose level that the radiologist should apply in each CT test.

Measurement of peripheral dose to the pelvic region and the associated risk for cancer development after breast intraoperative electron radiation therapy.

This study aimed to measure the received dose to the pelvic region of patients during breast intraoperative electron radiation therapy (IOERT). Furthermore, we compared the findings with those of external beam radiation therapy. Finally, secondary ovarian and uterus cancer risks following breast IOERT were estimated. In the current study, the received dose to the pelvic surface of 18 female patients during breast IOERT boosts were measured by thermoluminescent dosimeter (TLD-100) chips. All patients were treated with 12 Gy given in a single fraction. To estimate the dose to the ovary and uterus of the patients, conversion coefficients for depth from the surface dose were obtained in a Rando phantom. Given the received dose to the pelvic region of the patients, secondary ovarian and uterus cancer risks following breast IOERT were estimated. The received doses to the ovary and uterus surface of the patients were 0.260 ± 0.155 mGy to 31.460 ± 6.020 mGy and 0.485 ± 0.122 mGy to 22.387 ± 15.476 mGy, respectively. Corresponding intra-pelvic (ovary and uterus) regional doses were 0.012 ± 0.007 mGy to 1.479 ± 0.283 mGy and 0.027 ± 0.001 mGy to 1.164 ± 0.805 mGy, respectively. Findings demonstrated that the ratio of the received dose by the pelvic surface to the regional dose during breast IOERT was much less than external beam radiation therapy. The mean of the secondary cancer risks for the ovary in 8 and 10 MeV electron beam energies were 135.722 ± 117.331 × 10-6 and 69.958 ± 28.072 × 10-6, and for the uterus were 17.342 ± 10.583 × 10-6 and 2.971 ± 3.604 × 10-6, respectively. According to our findings, the use of breast IOERT in pregnant patients can be considered as a safe radiotherapeutic technique, because the received dose to the fetus was lower than 50 mGy. Furthermore, IOERT can efficiently reduce the unnecessary dose to the pelvic region and lowers the risk of secondary ovarian and uterus cancer following breast irradiation.

Ten-year results of the PORTEC-2 trial for high-intermediate risk endometrial carcinoma: improving patient selection for adjuvant therapy.

BACKGROUND: PORTEC-2 was a randomised trial for women with high-intermediate risk (HIR) endometrial cancer, comparing pelvic external beam radiotherapy (EBRT) with vaginal brachytherapy (VBT). We evaluated long-term outcomes combined with the results of pathology review and molecular analysis. METHODS: 427 women with HIR endometrial cancer were randomised between 2002-2006 to VBT or EBRT. Primary endpoint was vaginal recurrence (VR). Pathology review was done in 97.4%, combined with molecular analysis. RESULTS: Median follow-up was 116 months; 10-year VR was 3.4% versus 2.4% for VBT vs. EBRT (p = 0.55). Ten-year pelvic recurrence (PR) was more frequent in the VBT group (6.3% vs. 0.9%, p = 0.004), mostly combined with distant metastases (DM). Ten-year isolated PR was 2.5% vs. 0.5%, p = 0.10, and DM 10.4 vs. 8.9% (p = 0.45). Overall survival for VBT vs. EBRT was 69.5% vs. 67.6% at 10 years (p = 0.72). L1CAM and p53-mutant expression and substantial lymph-vascular space invasion were risk factors for PR and DM. EBRT reduced PR in cases with these risk factors. CONCLUSION: Long-term results of the PORTEC-2 trial confirm VBT as standard adjuvant treatment for HIR endometrial cancer. Molecular risk assessment has the potential to guide adjuvant therapy. EBRT provided better pelvic control in patients with unfavourable risk factors.