Rectal Dose Research Articles

Case Report: Anaplastic Astrocytoma Treated with Postoperative Radiotherapy Using Flattening Filter-Free Volumetric Arc Therapy (FFF-VMAT) during Pregnancy—Acceptable Fetal Dosimetry

Background: Postoperative irradiation for brain tumor in pregnant women is a matter of concern. Aim: We aimed to assess the safety of radiotherapy for brain tumors in pregnancy. We here report a successful treatment for anaplastic astrocytoma during pregnancy: surgery + postoperative irradiation. We wish to emphasize how we devised irradiation procedure to achieve both therapeutic effectiveness and safety to the fetus/infant. Case Presentation: A 34-year-old pregnant woman suffered with brain anaplastic astrocytoma. Tumor resection under craniotomy was performed with success. We decided to conduct postoperative radiotherapy at 25 weeks of gestation to reduce the risk of recurrence. We used a flattening filter-free volumetric arc therapy (FFF-VMAT) technique, which can achieve lower out-of-field dose than VMAT with a flattening filter or helical tomotherapy. We prescribed 60 Gy over 30 fractions. During actual beam delivery, surface and rectal dose to the patient (mother) were measured. The total fetal dose was estimated at 0.006 - 0.018 Gy, which is under the threshold set by the ICRP. A male healthy infant was born vaginally at the 37th week of pregnancy. The patient (mother) and the infant are healthy at the time of writing. Conclusion: FFF-VMAT is a good choice for brain tumors during pregnancy.

Dosimetric comparison of two different applicators and rectal retraction methods used in inverse optimization-based intracavitary brachytherapy for cervical cancer.

PurposeThe purpose of this study was to evaluate the dosimetric differences between two different applicators and rectal-retraction methods used in image-guided brachytherapy (IGBT) for locally advanced cervical cancer (LACC).Material and methodsTen patients with LACC treated with definitive chemoradiotherapy and inverse optimization-based IGBT were included in this study. In each patient, at least one fraction of IGBT was performed using tandem-ovoids (TO) with vaginal gauze packing (VGP) or tandem-ring (TR) with rectal-retractor (RR). High-risk clinical target volume (CTVHR) and intermediate-risk CTV (CTVIR) were defined as CTVs, and bladder, rectum, sigmoid, small bowel, urethra, and vaginal mucosa were defined as organs at risk (OARs). All patients received 50.4 Gy external beam radiotherapy (EBRT) in 28 fractions. After EBRT, 28 Gy high-dose-rate (HDR) IGBT in 4 fractions was delivered to central disease. A plan comparison was performed using dose-volume histogram (DVH) and treatment planning parameters for CTVs and OARs.ResultsThere were no significant differences in D90 values of CTVHR. In terms of rectum dose, TR with RR was found to be significantly better than TO with VGP (p < 0.0001 for D2cm3 and p < 0.013 for V5Gy). Although, there were no statistically significant differences in D2cm3 value of bladder, sigmoid, small bowel, upper vaginal mucosa, and urethra, mean value of D2cm3 for all defined OARs were found lower in TR than in TO. Bladder V7Gy, upper vaginal mucosa V7Gy, middle and lower vaginal mucosa D2cm3 values were all found to be significantly lower for TR than for TO (p < 0.035). CTVHR and CTVIR volumes contoured in TR were approximately 11% and 9% smaller than TO, respectively.ConclusionsThe results showed that there were no statistically differences in D90 value of CTVHR and CTVIR. However, all DVH parameters for OARs in TR with RR were found to be better than in TO with VGP.

The impact of rectal/bladder filling and applicator positioning on in vivo rectal dosimetry in vaginal cuff brachytherapy using an enhanced therapy setting

PurposeThe impact of rectal filling and bladder volume on in vivo rectal dosimetry (IVD) in vaginal cuff brachytherapy (VCBT) is unknown. The purpose of this study was to compare rectal doses from IVD with those calculated from treatment planning and to identify influencing factors. Materials and MethodsWe collected data of 80 VCBT sessions, four for each of 20 patients. Each was retrospectively compared with doses determined by the treatment planning system. Factors potentially predicting the IVD rectum dose were analyzed. ResultsFor a series of 80 brachytherapy applications, the calculated mean dose to the rectum was 2.52 Gy. The mean difference between all calculated and measured doses for the 80 applications with five probe positions each was 0.09 Gy (p = 0.952) proving high overall accordance between IVD and calculated doses at the rectum. The mean volume of the rectum was 119 ± 57 cm³. The rectal volume was not statistically significantly associated with the IVD or the calculated rectum doses. At the third and fourth rectal probe position in craniocaudal ordering, increased filling of the urinary bladder resulted in decreased measured and calculated doses (p < 0.05 for both). A rectum pointing position of the applicator significantly increased the maximum rectum dose compared with a bladder-oriented position (p < 0.05). ConclusionsIVD provided valuable data for rectal exposure in VCBT. Increased bladder filling and vaginal applicator positioning off the rectum elicited related with less rectal radiation exposure, whereas rectal filling did not. Further confirmation including assessment of IVD in bladder is pending to define optimal dosimetric conditions in VCBT.

Multiple Computed Tomography Robust Optimization to Account for Random Anatomic Density Variations During Intensity Modulated Proton Therapy

PurposeTo propose a method of optimizing intensity modulated proton therapy (IMPT) plans robust against dosimetric degradation caused by random anatomic variations during treatment. Methods and MaterialsFifteen patients with prostate cancer treated with IMPT to the pelvic targets were nonrandomly selected. On the repeated quality assurance computed tomography (QACTs) for some patients, bowel density changes were observed and caused dose degradation because the treated plans were not robustly optimized (non-RO). To mitigate this effect, we developed a robust planning method based on 3 CT images, including the native planning CT and its 2 copies, with the bowel structures being assigned to air and tissue, respectively. The RO settings included 5 mm setup uncertainty and 3.5% range uncertainty on 3 CTs. This method is called pseudomultiple-CT RO (pMCT-RO). Plans were also generated using RO on the native CT only, with the same setup and range uncertainties. This method is referred to as single-CT RO (SCT-RO). Doses on the QACTs and the nominal planning CT were compared for the 3 planning methods. ResultsAll 3 plan methods provided sufficient clinical target volumes D95% and V95% on the QACTs. For pMCT-RO plans, the normal tissue Dmax on QACTs of all patients was at maximum 109.1%, compared with 144.4% and 116.9% for non-RO and SCT-RO plans, respectively. On the nominal plans, the rectum and bladder doses were similar among all 3 plans; however, the volume of normal tissue (excluding the rectum and bladder) receiving the prescription dose or higher is substantially reduced in either pMCT-RO plans or SCT-RO plans, compared with the non-RO plans. ConclusionsWe developed a robust optimization method to further mitigate undesired dose heterogeneity caused by random anatomic changes in pelvic IMPT treatment. This method does not require additional patient CT scans. The pMCT-RO planning method has been implemented clinically since 2017 in our center.

Rectum Dose Constraints for Carbon Ion Therapy: Relative Biological Effectiveness Model Dependence in Relation to Clinical Outcomes.

The clinical application of different relative biological effectiveness (RBE) models for carbon ion RBE-weighted dose calculation hinders a global consensus in defining normal tissue constraints. This work aims to update the local effect model (LEM)-based constraints for the rectum using microdosimetric kinetic model (mMKM)-defined values, relying on RBE translation and the analysis of long-term clinical outcomes. LEM-optimized plans of treated patients, having suffered from prostate adenocarcinoma (n = 22) and sacral chordoma (n = 41), were recalculated with the mMKM using an in-house developed tool. The relation between rectum dose-volume points in the two RBE systems (DLEM|v and DMKM|v) was fitted to translate new LEM-based constraints. Normal tissue complication probability (NTCP) values, predicting late rectal toxicity, were obtained by applying published parameters. No late rectal toxicity events were reported within the patient cohort. The rectal toxicity outcome was confirmed using dosimetric analysis: DMKMVHs lay largely below original constraints; the translated DLEM|v values were 4.5%, 8.3%, 18.5%, and 35.4% higher than the nominal DMKM|v of the rectum volume, v—1%, 5%, 10% and 20%. The average NTCP value ranged from 5% for the prostate adenocarcinoma, to 0% for the sacral chordoma group. The redefined constraints, to be confirmed prospectively with clinical data, are DLEM|5cc ≤ 61 Gy(RBE) and DLEM|1cc ≤ 66 Gy(RBE).

Evaluation of rectal dose discrepancies between planned and in vivo dosimetry using MOSkin detector and PTW 9112 semiconductor probe during 60Co HDR CT-based intracavitary cervix brachytherapy

PurposeDose to the rectum during brachytherapy treatment may differ from an approved treatment plan which can be quantified with in vivo dosimetry (IVD). This study compares the planned with in vivo doses measured with MOSkin and PTW 9112 rectal probe in patients undergoing CT based HDR cervical brachytherapy with Co-60 source. MethodsDose measurement of a standard pear-shaped plan carried out in phantom to verify the MOSkin dose measurement accuracy. With MOSkin attached to the third diode, RP3 of the PTW 9112, both detectors were inserted into patients’ rectum. The RP3 and MOSkin measured doses in 18 sessions as well as the maximum measured doses from PTW 9112, RPmax in 48 sessions were compared to the planned doses. ResultsPercentage dose differences ΔD (%) in phantom study for two MOSkin found to be 2.22 ± 0.07% and 2.5 ± 0.07%. IVD of 18 sessions resulted in ΔD(%) of −16.3% to 14.9% with MOSkin and ΔD(%) of −35.7% to −2.1% with RP3. In 48 sessions, RPmax recorded ΔD(%) of −37.1% to 11.0%. MOSkin_measured doses were higher in 44.4% (8/18) sessions, while RP3_measured were lower than planned doses in all sessions. RPmax_measured were lower in 87.5% of applications (42/47). ConclusionsThe delivered doses proven to deviate from planned doses due to unavoidable shift between imaging and treatment as measured with MOSkin and PTW 9112 detectors. The integration of MOSkin on commercial PTW 9112 surface found to be feasible for rectal dose IVD during cervical HDR ICBT.

Evaluating the predictive value of quantec rectum tolerance dose suggestions on acute rectal toxicity in prostate carcinoma patients treated with IMRT.

To investigate the predictive value of convenience of rectum dosimetry with Quantitative Analysis of Normal Tissue Effects in the Clinic (QUANTEC) dose limits, maximum rectum dose (Dmax), total rectal volume (TVrectum), rectal volume included in PTV (VrectumPTV) on Grade 2-3 acute rectal toxicity for utilization in clinical practice. Numerous previous data have reported frequent acute proctitis after external-beam RT of prostate cancer. Predicting toxicity limited with dose information is inadequate in clinical practice due to comorbidities and medications used. Sixty-four non-metastatic prostate cancer patients treated with IMRT were enrolled. Patients were treated to a total dose of 70-76Gy. Rectal dose volume histograms (DVH) of all patients were evaluated retrospectively, and a QUANTEC Score between 0 and 5 was calculated for each patient. The correlation between the rectal DVH data, QUANTEC score, TVrectum, VrectumPTV, rectum Dmax and Grade 2-3 rectal toxicity was investigated. In the whole group grade 1, 2 and 3 acute rectal toxicities were 25%, 18.8% and 3.1%, respectively. In the DVH data, rectum doses of all patients were under RTOG dose limits. Statistically significant correlation was found between grade 2-3 rectal toxicity and TVrectum (p=0,043); however. It was not correlated with QUANTEC score, VrectumPTV and Dmax. Our results were not able to show any significant correlation between increasing convenience with QUANTEC limits and lower rectal toxicity. Conclusively, new dosimetric definitions are warranted to predict acute rectal toxicity more accurately in prostate cancer patients during IMRT treatment.

Framework for Evaluation of Automated Knowledge-Based Planning Systems Using Multiple Publicly Available Prostate Routines

PurposeTo establish a framework for the evaluation of knowledge-based planning routines that empowers new adopters to select systems that best match their clinical priorities. We demonstrate the power of this framework using 4 publicly available prostate routines. Methods and MaterialsFour publicly available prostate routines (CCMB, Miami, UCSD, WUSTL) were automatically applied across a 25-patient cohort using Eclipse scripting and a PTV prescription of V81 Gy = 95%. The institutions’ routines differed in contouring guidelines for planning target volume (PTV) and organs at risk, beam arrangements, and optimization parameters. Model-estimated dose-volume histograms (DVHs) and deliverable postoptimization DVHs were extracted from plans to calculate average DVHs for each routine. Each routine’s average calculated DVH was subtracted from the average DVH for all plans and from the model’s average predicted DVH for comparison. DVH metrics for PTV (DMAX, D1%, D99%, DMIN), Rectum (DMAX, V70, V60, V40), Bladder (V75, V40), Femur (DMAX), and PenileBulb (DMEAN) were compared with the average using 2-sided paired t tests (Bonferroni-corrected P < .05). To control for contouring effects, the full analysis was conducted for 2 PTV margin schemas: 5 mm uniform and 3 mm or 7 mm posterior/else. ResultsCalculated plans generally aligned with their routine’s DVH estimations, except CCMB organ-at-risk Dmaxes. Dosimetric parameter differences were not significant, with the exception of PTV DMAX (Miami = 111.1% [P < .001]), PTV D99% (Miami = 97.4% [P = .05]; UCSD = 97.4% [P = .03]; CCMB = 98.5% [P = .001]), Rectum V40 (Miami = 19.1% [P < .001]; UCSD = 22.7% [P = .003]; CCMB = 53.5% [P < .001]), and Femur DMAX (WUSTL = 48.6% [P = .001.]; CCMB = 37.9% [P < .001]). Overall, UCSD and Miami had lower rectum doses, and CCMB and WUSTL had higher PTV homogeneity. Conclusions were unchanged with different PTV margin schemas. ConclusionsUsing publicly available knowledge-based planning routines spares clinicians substantial effort in developing new models. Our results allow clinicians to select the prostate routine that matches their clinical priorities, and our methodology sets the precedent for comparing routines for different treatment sites.

Dosimetric evaluation of bladder and rectal radiation dose in Ca Cervix patients using CT planning with Iridium 192, Cobalt 60 in HDR Brachytherapy- Single Institutional Experience

Dosimetric evaluation of bladder and rectal radiation dose in Ca Cervix patients using CT planning with Iridium 192, Cobalt 60 in HDR Brachytherapy- Single Institutional Experience

Rectal indometacin dose escalation for prevention of pancreatitis after endoscopic retrograde cholangiopancreatography in high-risk patients: a double-blind, randomised controlled trial

Although rectal indometacin 100 mg is effective in reducing the frequency and severity of pancreatitis after endoscopic retrograde cholangiopancreatography (ERCP) in high-risk patients, the optimal dose is unknown, and pancreatitis incidence remains high. The aim of this study was to compare the efficacy of two dose regimens of rectal indometacin on the frequency and severity of pancreatitis after ERCP in high-risk patients. In this randomised, double-blind, comparative effectiveness trial, we enrolled patients from six tertiary medical centres in the USA. Eligible patients were those at high risk for the development of pancreatitis after ERCP. We randomly assigned eligible patients (1:1) immediately after ERCP to receive either two 50 mg indometacin suppositories and a placebo suppository (standard-dose group) or three 50 mg indometacin suppositories (high-dose group). 4 h after the procedure, patients assigned to the high-dose group received an additional 50 mg indometacin suppository, whereas patients in the standard-dose group received an additional placebo suppository. The randomisation schedule, stratified according to study centre and with no other restrictions, was computer generated by an investigator who was uninvolved in the clinical care of any participants, distributed to the sites, and kept by personnel not directly involved with the study. These same personnel were responsible for packaging the drug and placebo in opaque envelopes. Patients, study personnel, and treating physicians were masked to study group assignment. The primary outcome of the study was the development of pancreatitis after ERCP. Analyses were done on an intention-to-treat basis. This trial is registered with ClinicalTrials.gov, number NCT01912716, and enrolment is complete. Between July 9, 2013, and March 22, 2018, 1037 eligible patients were enrolled and randomly assigned to receive either standard-dose (n=515) or high-dose indometacin (n=522). Pancreatitis after ERCP occurred in 141 (14%) of 1037 patients-76 (15%) of 515 patients in the standard-dose indometacin group and 65 (12%) of 522 patients in the high-dose indometacin group (risk ratio [RR] 1·19, 95% CI 0·87-1·61; p=0·32). We observed 19 adverse events that were potentially attributable to study drug. Clinically significant bleeding occurred in 14 (1%) of 1037 patients-six (1%) of 515 patients in the standard-dose indometacin group and eight (2%) of 522 patients in the high-dose indometacin group (p=0·79). Three (1%) of 522 patients in the high-dose indometacin group developed acute kidney injury versus none in the standard-dose group (p=0·25). A non-ST elevation myocardial infarction occurred in the standard-dose indometacin group 2 days after ERCP. A transient ischaemic attack occurred in the high-dose indometacin group 5 days after ERCP. All 19 adverse events, in addition to the 141 patients who developed pancreatitis after ERCP, were considered serious as all required admission to hospital. We observed no allergic reactions or deaths at 30 day follow-up. Dose escalation to rectal indometacin 200 mg did not confer any advantage compared with the standard 100 mg regimen, with pancreatitis incidence remaining high in high-risk patients. Current practice should continue unchanged. Further research should consider the pharmacokinetics of non-steroidal anti-inflammatory drugs to determine the optimal timing of their administration to prevent pancreatitis after ERCP. American College of Gastroenterology.

The development of high quality training program for real tine trans rectal ultrasound low dose rate (LDR) prostate brachytherapy

Although ultrasound forms a critical component of transrectal ultrasound image guided brachytherapy for prostate cancer, ultrasound training is not required as part of radiation oncology training programs, nor does any objective competency measure exist to independently assess clinical performance [ [1] Davis B.J. et al. American Brachytherapy Society consensus guidelines for transrectal ultrasound-guided permanent prostate brachytherapy. Brachytherapy. 2012; Abstract Full Text Full Text PDF Scopus (360) Google Scholar ]. Physical simulation training and objective clinical competency testing can provide a structured approach to training [ [2] McGaghie W.C. et al. A critical review of simulation-based medical education research: 2003–2009. Med. Educ. 2010; Google Scholar ], but only if suitably challenging training devices are available which replicate the complex anatomy of the male pelvis and prostate. This study describes the iterative process in the development of a range of training devices which simulate both the anthropomorphic and sonographic characteristics of the different presentations of patient specific prostate cancer. The design of the clinical features involved selection of patient cases and then rapid prototyping the different anatomical features and inverse casting these features in tissue mimicking materials (TMM). Novel TMMs were developed that had the sonographic appearance of the prostate and overlying tissues, as well as having the relevant mechanical compliance to give the training devices required haptic feedback. These devices will be used in the development of a training programme and will complement the learner’s development of the specific skills required for the procedure. The use of training strategies such as gamification allows trainees to track their own performance over time as well as relative to their peers; thereby, providing a structured and competitive approach to learning. The 3D prototyped clinical features in these devices provided a more clinically-relevant representation of the procedure, thus providing a more efficacious training opportunity.

A Novel 2D Probability Density Function Integrating the Rectal Motion and Wall Thickness in Prostate IMRT

Background and purposeThis study investigated the variations of rectal motion and wall thickness in prostate intensity-modulated radiotherapy using a novel 2D probability density function. To evaluate the impact of the position, thickness, and deformation of the rectum on the dose distribution in prostate intensity-modulated radiotherapy plans, probability density functions (pdf) of the deformation of rectal cross-section (DW), rectal dose distribution (RM), and changes in rectal wall thickness (TW) were used in the planning optimization. Materials and MethodsThe problem of approximating the product of a number of Gaussian mixture distributions arises in the number of parameters describing the specific mean value, standard deviation, and weight in every Gaussian. In this work, a pdf model has been developed which specifies the variability of the average rectal wall thickness. The model is based on the histogram of 587 randomly selected patients with prostate cancer. ResultsThe average wall thicknesses were determined based on the rectal structure contours drawn on the planning CT image set of the patient. The pdf describing the variability of the rectal wall thickness (pdfTW) is represented as a three-mode Gaussian mixture of specific (μF,σF); (μPF,σPF) and (μE,σE) and individual weights (wF, wPF, and wE) representing full, partially full, and empty rectal states, respectively. ConclusionA 2D Gaussian pdf of rectal motion and rectal thickness (2D pdfM&TW) function, as a product-mixture model of the pdf of the rectal motion (pdfM) and the pdfTW, was developed using published and experimental data, respectively, and presented mathematically. Using correlation values between the functions pdfM and pdfTW, the sensitivity of profiles and projections to the 2D pdfM&TW is numerically demonstrated.

Cross-modality applicability of rectal normal tissue complication probability models from photon- to proton-based radiotherapy

Background and purposeProton therapy (PT) is currently being studied to improve normal tissue (NT) sparing beyond what can be achieved with conventional photon-based therapy. Compared to photons, PT dose distributions have a reduced NT low-to-intermediate ‘dose bath’ and a different biological effectiveness, questioning the applicability of photon-based NT complication probability (NTCP) models to PT. The aim of this study was to assess the applicability of photon-based NTCP models to rectum morbidity outcomes following PT. Materials and methodsTreatment planning and morbidity data from 1151 prostate cancer patients treated with passive scattering PT and from 159 patients treated with conventional 3D conformal four-field photon therapy were analysed. Prospectively scored gastrointestinal morbidities (grade >=2) were analysed, with a total of 184 events (protons; medical and procedural) and 12 events (photons; procedural only), respectively. Rectal dose volume histograms were extracted for all patients in both cohorts and used as input to two different NTCP models, with up to six different published photon-based parameter sets. ResultsPhoton-based rectal NTCP models either over- or underestimated the clinically observed gastrointestinal morbidity when used on the proton cohort, depending on the choice of endpoint (p < 0.05 for all parameter sets, for both morbidity classifications). Four of the six photon-based NTCP models showed a good fit to the photon outcome data (p > 0.05). ConclusionThere were large differences in morbidity predictions between cohorts and modalities, indicating that the validity of NTCP models and parameters across institutions and treatment modalities should be carefully investigated prior to clinical application.

Placement of SpaceOAR hydrogel spacer for prostate cancer patients treated with iodine-125 low-dose-rate brachytherapy.

The aim of the present study was to report on our early experience with hydrogel spacer (SpaceOAR) placement in combination with iodine-125 low-dose-rate brachytherapy for prostate cancer. From April 2018, SpaceOAR hydrogel spacer was placed in 100 consecutive patients undergoing iodine-125 low-dose-rate brachytherapy. Complications and the status of the placement were evaluated. Deformation of the prostate by the spacer was examined measuring prostate diameters and evaluating the change from preoperative status. The position of the prostate was similarly examined by evaluating the change in distance between the pubic symphysis and the prostate. Post-plan dosimetric data were compared with 200 patients treated without a spacer. No complications were found during either the intraoperative or perioperative periods. The mean displacement distance of 11.64mm was created, the mean value before spacer placement was 0.28mm (P<0.0001). The change of the prostate diameters showed a positive increase in all directions, with no significant negative change in any one direction. Regarding the change in distance between pubic symphysis and the prostate, no significant shortening trend was observed between the two groups (P=0.14). Whereas the dosimetric parameters showed means of 0.001 and 0.026cc for RV150 and RV100 in the spacer group, they were 0.025 and 0.318cc, respectively, in the non-spacer group, showing a significant decrease in both parameters (P<0.001). Prostate deformation secondary to hydrogel placement might adversely affect dosimetric parameters in patients undergoing low-dose-rate brachytherapy. However, a significant reduction in the rectal dose can be adopted without adversely affecting the other parameters related to treatment outcome.

78 What Is the Impact of a Delayed Presentation on Outpatients With Post-ERCP Pancreatitis? An Analysis of Clinical Predictors and Outcomes

INTRODUCTION: Post-ERCP pancreatitis (PEP) occurs in up to 15% of high risk patients. Symptoms after ERCP are common and usually determine admission. However, discharge of outpatients at risk for PEP is frequent after ERCP. In retrospective studies, discharged PEP patients are at increased risk for severity, possibly due to delays in IV fluid therapy. The aim of this study is to evaluate clinical predictors and outcomes in patients discharged and later admitted with delayed presentation of PEP. METHODS: We identified consecutive outpatients with PEP enrolled in a prospective study designed to evaluate the optimal rectal Indomethacin dose for prevention of PEP in high-risk patients. All patients received Indomethacin and were observed for at least 4 hours post-ERCP per protocol. All clinical data except IV fluids, recovery medications, and pain scores were collected prospectively. Diagnosis and severity of PEP was defined by Cotton criteria. RESULTS: 107/720 (14.9%) developed PEP. 135/720 (18.8%) were directly admitted after ERCP. While the direct admission rate in patients that developed PEP was higher (P &lt; 0.001), 58/107 (54.2%) were discharged and had a delayed presentation of PEP. Median time to presentation was 24 hours (IQR 15–31.75 h). Discharged patients were older (age 47.7 vs 41.1, P = 0.026), more often had a morning procedure (59.2% vs 39.7%, P = 0.044), less often had pancreatic stent placement (82.8% vs 95.9%, P = 0.032), spent less time in recovery (261 vs 312 minutes, P = 0.004), required less IV opioids (6.4 vs 17.3 MME, P &lt; 0.001) and had lower pain scores (2.8 vs 6.5, P &lt; 0.001) (Table 1). On multivariable analysis, an afternoon procedure (OR 4.00, P = 0.016) and pain score &gt;3 (OR 1.37, P = 0.001) were associated with admission. While discharged patients were more likely to present with SIRS on admission (43.1% vs 10.2%, P &lt; 0.001), a delayed presentation was not associated with severe PEP (Table 2). CONCLUSION: Delayed presentation of PEP after discharge of high-risk patients is frequent, but not associated with adverse outcomes or severe PEP. Systematic deployment of PEP prophylaxis with rectal Indomethacin, pancreatic stents, and IV fluids may attenuate the impact of delayed presentation on outcomes. Afternoon procedure time and increased pain appear to influence decisions to admit. However, given the frequency of delayed presentation of PEP, accurate and early diagnostic tests for PEP may be of clinical value.

Major Complications and Adverse Events Related to the Injection of the SpaceOAR Hydrogel System Before Radiotherapy for Prostate Cancer: Review of the Manufacturer and User Facility Device Experience Database.

Purpose: SpaceOAR® is a Food and Drug Administration-approved hydrogel injection used to create space between the prostate and rectum during prostate radiotherapy. It has shown to significantly reduce the rectal radiation dose with lower rates of rectal toxicity. Despite a high safety performance in initial trials, SpaceOAR remains in early clinical use. Thus, we examined emerging safety reports as the system becomes more widely utilized. Methods: We reviewed the SpaceOAR manufacturer website for the safety profile and complications associated with the SpaceOAR hydrogel. We then compared this with reports submitted to the Manufacturer and User Facility Device Experience (MAUDE) database. Results: The manufacturer website reported risks including pain, needle penetration, and/or gel injection into a nearby organ or blood vessel, local inflammation, infection, urinary retention, and local rectal injury or symptoms. There were 22 unique reports discussing 25 patient cases in the MAUDE database from January 2015 to March 2019, with an increasing number of reports each year up through 2018. Unique major complications including acute pulmonary embolism, severe anaphylaxis, prostatic abscess and sepsis, purulent perineal drainage, rectal wall erosion, and rectourethral fistula were reported. Conclusion: Despite well-documented clinical benefits of the SpaceOAR System, there are a number of severe and debilitating complications recently reported in proximity to gel injection. This highlights the need for further study of device complications in light of its increasing clinical use.

Comparison of dose statistics for bladder wall and rectum wall vs whole organs for VMAT prostate treatment

Dose-wall histograms (DWHs) have been used as alternatives to dose-volume histograms (DVHs) for hollow organs, with the rationale that the dose delivered to the interior of a hollow organ would be unrelated to the level of radiation damage. The purpose of this study is to conduct a statistical comparison of dose statistics for both walled and solid structure contours for both bladder and rectum in the treatment of intermediate risk prostate cancer with volumetric arc therapy (VMAT). Ten intermediate risk prostate cases were randomly selected. Rectum and bladder were first contoured as solid structures, and then the corresponding wall structures were generated using either a slice-by-slice cropping (2D method), or with a full 3D cropping tool (3D method). Each case was then inverse planned using a 2-arc VMAT technique. Two plans per case were created, 1 with a hypofractionated treatment and 1 with a standard fractionated treatment. DVHs were calculated for solid structure contours, and DWHs were calculated for the walled structure contours generated using 2D and 3D contouring tools. A nonparametric Spearman statistic correlation test was used to compare a large number of relevant dose histogram points, and to establish the relationship between dose statistics for walled and solid structures. Several notable relationships were observed. Maximum rectal dose was strongly correlated between the solid structure and both the 2D-generated (Spearman's correlation rs = 0.988, p < 0.01) and 3D-generated (rs = 0.952 p< 0.01) wall structures. This indicates that the rectal hot spot occurred in or near the wall for all cases, suggesting that both structure types give similar maximum dose information for rectum. Maximum bladder dose was not significantly correlated between solid structures and the 2D (rs = 0.596, p= 0.069) and 3D-generated (rs = 0.681, p= 0.03) counterparts. This suggests that the maximum dose is not consistently in or near the bladder wall. This favors the use of bladder wall contours when considering bladder toxicity, with the maximum dose to the wall potentially being more relevant radiobiologically. This analysis was extended to many other relevant points on the rectum and bladder histogram curves. Where correlations are strong, equations of best-fit are presented. This work establishes several statistically-significant relationships between bladder and rectum DVHs and DWHs for VMAT irradiation of intermediate-risk prostate cancer. This information may be used to inform contouring requirements for clinical trial design as well as for standard patient care.

Late toxicities of prostate cancer radiotherapy with and without hydrogel SpaceAOR insertion.

To investigate whether the implantation of a hydrogel spacer (SpaceOAR) reduces long-term rectal toxicity for prostate cancer patients treated with intensity-modulated radiotherapy (IMRT). Patients with localised prostate cancer treated with 81Gy in 45fx of IMRT over 9weeks were retrospectively compared: 65 patients with SpaceOAR and 56 patients without SpaceOAR. Planning aims restricted rectal doses to V40 Gy<35%, V65 Gy<17%, V75 Gy<10%. Toxicities were evaluated between 3months and 3years after the completion of radiotherapy and were based on the common terminology criteria for adverse events (CTCAE) assessment tool for diarrhoea, haemorrhoids, faecal incontinence and proctitis. The cumulative incidence of low-grade diarrhoea (G1) was significantly higher in the non-SpaceOAR group (21.4% vs 6.2%; P=0.016). The cumulative incidence of proctitis (grades G1 and G2) was also higher in the non-SpaceOAR group (26.7% vs 9.2%; P=0.015); the cumulative incidence of G2 proctitis was higher in the latter group (P=0.043). There were no differences between the treatment groups for cumulative incidences of faecal incontinence and/or haemorrhoids. Three years after IMRT, diarrhoea and proctitis were higher in the non-SpaceOAR group, without reaching statistical significance. This finding was unchanged after correcting for baseline symptoms. SpaceOAR is of benefit in reducing the cumulative incidence of low-grade diarrhoea and proctitis for up to 3years after intensity-modulated radiotherapy.

Comparative toxicity outcomes of proton-beam therapy versus intensity-modulated radiotherapy for prostate cancer in the postoperative setting.

Despite increasing utilization of proton-beam therapy (PBT) in the postprostatectomy setting, no data exist regarding toxicity outcomes relative to intensity-modulated radiotherapy (IMRT). The authors compared acute and late genitourinary (GU) and gastrointestinal (GI) toxicity outcomes in patients with prostate cancer (PC) who received treatment with postprostatectomy IMRT versus PBT. With institutional review board approval, patients with PC who received adjuvant or salvage IMRT or PBT (70.2 gray with an endorectal balloon) after prostatectomy from 2009 through 2017 were reviewed. Factors including combined IMRT and PBT and/or concurrent malignancies prompted exclusion. A case-matched cohort analysis was performed using nearest-neighbor 3-to-1 matching by age and GU/GI disorder history. Logistic and Cox regressions were used to identify univariate and multivariate associations between toxicities and cohort/dosimetric characteristics. Toxicity-free survival (TFS) was assessed using the Kaplan-Meier method. Three hundred seven men (mean±SD age, 59.7±6.3years; IMRT, n=237; PBT, n=70) were identified, generating 70 matched pairs. The median follow-up was 48.6 and 46.1months for the IMRT and PBT groups, respectively. Although PBT was superior at reducing low-range (volumes receiving 10% to 40% of the dose, respectively) bladder and rectal doses (all P ≤ .01), treatment modality was not associated with differences in clinician-reported acute or late GU/GI toxicities (all P≥.05). Five-year grade ≥2 GU and grade ≥1 GI TFS was 61.1% and 73.7% for IMRT, respectively, and 70.7% and 75.3% for PBT, respectively; and 5-year grade ≥3 GU and GI TFS was >95% for both groups (all P≥.05). Postprostatectomy PBT minimized low-range bladder and rectal doses relative to IMRT; however, treatment modality was not associated with clinician-reported GU/GI toxicities. Future prospective investigation and ongoing follow-up will determine whether dosimetric differences between IMRT and PBT confer clinically meaningful differences in long-term outcomes.

Assessment of Polyethylene Glycol Hydrogel Spacer and Its Effect on Rectal Radiation Dose in Prostate Cancer Patients Receiving Proton Beam Radiation Therapy

PurposeTo assess the efficacy of placing a polyethylene glycol (PEG) spacing hydrogel in patients undergoing proton beam radiation therapy for prostate cancer. This study also aims to assess the effect on rectal radiation dose of prostate–rectum separation in various anatomic planes. Methods and MaterialsSeventy-two consecutive prostate cancer patients undergoing conventionally fractionated pencil beam scanning proton radiation therapy with and without hydrogel placement were compared. Magnetic resonance images taken after hydrogel placement measured prostate–rectum separation and were correlated to rectal dosing and rectal toxicity. Univariate analysis of clinical variables and radiation dosing was conducted using nonparametric Wilcoxon rank-sum test with continuity correction between groups (hydrogel spacer vs controls). Spearman's rank correlation coefficient assessed relationships between the various anatomic dimensions of perirectal space and rectal radiation dosing. ResultsFifty-one patients had hydrogel placement before therapy and 21 did not. There was a 42.2% reduction in rectal dosing (mL3 rectum) in hydrogel patients (P < .001). Increasing midline sagittal lift resulted in a greater mitigation of total rectal dose (P = .031). The degree of prostate surface area coverage on coronal plane did not correlate with further reductions in rectal radiation dose (P = .673). Patients who had PEG hydrogels placed reported more rectal side effects during treatment compared with those patients who did not (35.3% vs 9.5%, P = .061). At median 9.5-month follow-up, there was no difference in reporting of grade ≤2 rectal toxicity between the 2 groups (7.7% vs 7.1%, P = .145). ConclusionsPolyethylene glycol hydrogel placement before pencil proton beam radiation therapy for prostate cancer reduced rectal radiation dose. The most important factor reducing total rectal dose was the degree of sagittal midline separation created by the PEG hydrogel. This is the largest study with the longest follow-up to investigate hydrogel placement in the proton beam radiation setting.