Rectal Wall Research Articles

Abstract A026: Identifying unique genomic and clinical characteristics of radiation-associated rectal cancer

Abstract Introduction: Prostate cancer patients treated with radiation therapy (RT) are at risk of developing radiation-associated rectal cancer (RARC). Previous literature reports worse overall survival in these patients compared to those with non-radiation associated primary rectal cancer (PRC), yet the genomic and clinical characteristics of RARC are not well understood. We compared molecular profiles of RARC and PRC patients to better understand the mechanism of RARC tumorigenesis and its interplay with clinical outcomes. Methods: We performed a retrospective analysis of 22 patients who had stage I-IV rectal cancer (within 12 cm of the anal verge) and had received previous RT for prostate cancer. Patients were excluded if they had a latency period between cancers of <5 years or additional metachronous cancers. Tumors were profiled using MSK-IMPACT, a targeted DNA-sequencing panel that identifies somatic mutations, copy number changes and fusions in a panel of 341-505 genes using a combination of solid tissue and matched blood specimens. The cohort included patients who had received external beam radiation therapy (EBRT, n=8), brachytherapy (BT, n=7), and combined EBRT-BT (n=7). All the RARC patients were microsatellite stable (MSS). To compare molecular features while accounting for clinical differences, we performed propensity score matching (1:1 ratio) using a background set of 616 patients with MSS PRC who had also been sequenced with MSK-IMPACT. Patients were matched for gender, age at diagnosis, distance from anal verge, tumor size, tumor location (anterior, lateral or posterior) and stage. Results: When compared to the general background set of 616 MSS PRC cases, RARC patients tended to be older at diagnosis (median 74 vs. 54 years, P=<0.0001). RARC tumors were more likely to have size <4cm at diagnosis (70% vs. 36%, P=0.01), to originate in the distal rectum, within 0-4 cm from the anal verge (55% vs. 25%, P=<0.001) and also to develop along the anterior rectal wall (41% vs 22%, P=<0.001). We then compared the genomic features of RARC to the clinically matched PRC set. RARC exhibited lower tumor mutational burden than PRC (median 4.4 vs. 6.0 mut/Mb, P=0.011), but no difference was observed in terms of chromosomal instability measured as the fraction of genome altered by copy number changes [median 0.11 vs. 0.17, P=0.49]. RARC patients also exhibited significantly lower frequency of APC mutations (41% vs. 82%, P=0.012) compared to PRC patients. Conclusion: We have identified clinical and molecular differences between RARC and PRC, including distal and anterior locations as well as lower TMB and lower frequency of APC mutations in RARC patients. The results provide clinically relevant insights into the unique attributes of RARC and may ultimately help to improve prognostication and treatment for this unique population. Citation Format: Dana M. R. Omer, Anisha Luthra, Hannah M. Thompson, Jonathan B. Yuval, Paul B. Romesser, Philip B. Paty, Julio Garcia-Aguilar, Francisco Sanchez-Vega. Identifying unique genomic and clinical characteristics of radiation-associated rectal cancer [abstract]. In: Proceedings of the AACR Special Conference on Colorectal Cancer; 2022 Oct 1-4; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;82(23 Suppl_1):Abstract nr A026.

Endoscopic Closure of Iatrogenic Rectal Perforation Using the Tulip Bundle Technique.

CASE REPORT Cleansing enemas are commonly used for constipation, but rectal perforation is a rare complication, with a mean incidence of 0.02%–0.23%.1,2 A 75-year-old woman was referred to the emergency department with severe constipation. Physical examination revealed solid stools in the rectum, and a cleansing enema was applied. Immediately, she presented with abundant hematochezia. Rectosigmoidoscopy revealed a large perforation in the posterior rectal wall because of the tip of the enema. Pelvic computed tomography showed extraluminal air in the perirectal fat, suggestive of rectal perforation (Figure 1). To prevent complications, she was admitted under antibiotics and repeated rectosigmoidoscopy.Figure 1.: Pelvic computed tomography showing perirectal free air and fat stranding, suggestive of rectal perforation.We attempted to close the perforation (Figure 2) using an over-the-scope clip, but it did not adequately fit the defect. Because therapeutical failure was imminent, we performed mucosal closure using a clip-fixed endoloop in a single-channel colonoscope. First, a clip was inserted in the working channel of the endoscope; as an independent device outside the scope, the tip of the endoloop was attached to the clip's teeth; next, the clip and endoloop were housed inside the scope channel until completely hidden, and both the scope and the endoloop were inserted in the rectum. The clip-fixed endoloop was then fixed onto the normal mucosa near the mucosal defect; 3 additional clips were used to anchor the endoloop circumferentially along the tear margins. Finally, the endoloop was tightened to close the perforation (Figure 3). The patient recovered uneventfully and was discharged after 7 days. Two weeks later, only a small scar was identified.Figure 2.: Rectosigmoidoscopy revealing a rectal perforation in the posterior rectal wall.Figure 3.: Endoscopic closure of the rectal perforation after using an endoloop. The endoloop was anchored with clips to the normal mucosa near the perforation's edges and closed in a purse-string fashion.An early approach of rectal perforations is critical to prevent complications and reduce mortality.1 Endoscopic techniques, such as over-the-scope clips or through-the-scope clips, are preferred when surgery has high risk of morbimortality.3 New techniques, such as endoloop, have been increasingly used, but choice depends on the type and size of the perforation, available devices, and endoscopist expertise (Video 1, https://links.lww.com/AJG/C770).4,5 {"href":"Single Video Player","role":"media-player-id","content-type":"play-in-place","position":"float","orientation":"portrait","label":"Video 1","caption":"Endoscopic closure of iatrogenic rectal perforation after a cleansing enema, by using the tulip bundle technique.","object-id":[{"pub-id-type":"doi","id":""},{"pub-id-type":"other","content-type":"media-stream-id","id":"10.14309/crj.0000000000000898.vid1"},{"pub-id-type":"other","content-type":"media-source","id":"Kaltura"}]} DISCLOSURES Author contributions: F. Pires acquired data, drafted the manuscript, and performed video editing. AC Carvalho acquired data and performed video editing. R. Araújo was responsible for conception and performance of the endoscopic procedure and critically revised the report. All authors read and approved the final version of the manuscript. F. Pires is guarantor of the article. Financial disclosure: None to report. Informed consent was obtained for this case report.

Unilateral perineal hernia surgery. Case report

Perineal hernia results from weakening and/or the inability of the pelvic diaphragm to support the rectal wall, promoting caudal displacement of abdominal or pelvic organs in the perineum. Unneutered male dogs aged between 7 and 10 years are the most affected, being rare in females. The main clinical signs are unilateral or bilateral swelling of the perineal region, associated or not with tenesmus, dysuria, urinary and/or fecal incontinence, anuria and pain during defecation. The diagnosis is based on clinical history, anamnesis, physical examination, and complementary tests such as radiography and ultrasound. Clinical treatment can be done in some cases, but surgical intervention is required to resolve the problem. The present work aims to report the case of a patient treated at the FullPet Veterinary Clinic in Guarulhos, São Paulo, Brazil, a 7-year-old male Yorkshire canine, unneutered, weighing 4.5 kg. The same was submitted to surgery by the tradi­tional method of suture with nylon thread and enteropexy. When there was recurrence, surgical reintervention was necessary to correct the hernia using a polypropylene mesh.

TAIL GUT CYST- A RARE FINDING- CASE REPORT AND REVIEW OF LITERATURE

Introduction: Tailgut cysts are rare congenital entity that arises from the embryological hindgut and usually located in presacral space. Here we report a case of tail gut cyst which is an infrequent condition. Case report: Here, we report a nineteen year old male with lower abdominal pain. The relevant investigations were performed. The CT abdomen revealed a well-dened cystic lesion in the pelvis in lower presacral region and posterior to rectum with small calcied foci suggestive of tail gut cyst with scalloping of sacrum. MRI pelvis suggested large well dened unilocular cystic lesion in the retro-rectal and pre-sacral region extending from S2 to mid coccygeal level showing thin imperceptible walls few tiny projections and small rounded non enhancing nodule along its posterior wall with thin focal calcication seen in its wall with no evidence of malignancy and no signs of osseous destruction. The patient was explored and intraoperatively ndings revealed a cyst of size 8 cm * 5 cm behind the rectum and in front of sacrum which was densely adhered to the posterior wall of rectum but free from sacrum. The mass was resected as a whole and sent for histopathological exam which was suggestive of tailgut cyst. Tailgut cysts is infrequent condition which manifests as chronic lower abdominal pai Conclusion: n. It is crucial that such entity be diagnosed and surgically excised early in its presentation. It is important to rule out malignancy in the post operative biopsy

A two-team approach for the complete resection of a bulky gastrointestinal stromal tumor on the anterior wall of the lower rectum after neoadjuvant treatment.

A two-team approach for the complete resection of a bulky gastrointestinal stromal tumor on the anterior wall of the lower rectum after neoadjuvant treatment.

Primary S100 Negative Amelanotic Spindle Vaginal Melanoma

Abstract Introduction/Objective Vaginal melanoma is a rare malignancy composed of cells showing melanocytic differentiation and represents less than 3% of malignant vaginal tumors. It occurs in older women, typically in the distal third of the vagina. Outcomes are poor and median survival is less than 2 years. Macroscopically, 90% of these lesions are pigmented, polypoid and ulcerated. Microscopically they demonstrate diffuse, nested, trabecular, and/or fascicular patterns and are comprised of epithelioid cells with or without a spindle cell component. They are typically pigmented and S100 positive. Methods/Case Report Here we present a rare case of purely spindled amelanotic S100 negative vaginal melanoma. The patient is a 75 year old woman who presented with a 6 month history of vaginal discharge, and a one month history of new foul odor and vaginal bleeding, constipation, and unintentional weight loss. A large vaginal mass was palpated on physical exam. Subsequent computed tomography demonstrated a 8.2 x 8.2 x 9.4 cm mass occupying the vaginal vault with abutment of the urinary bladder anteriorly and the rectal and anal walls posteriorly. A biopsy was performed and a 3.8 x 2.2 x 1.2 cm aggregate of pink tan friable tissuse was obtained. Histopathologic examination showed a malignant neoplasm composed purely of spindled cells in a fasicular pattern. Tumor cells showed marked nuclear pleomorphism with inconspicuous nucleoli. Tumor necrosis was present. No pigment was seen. By immunohistochemistry, tumor was positive for SOX10, HMB45, and Melan A, and negative for S100, AE1/3, EMA, myogenin, desmin, smooth muscle actin, synaptophysin, chromogranin, Pax8, and GATA3. BRAF mutation analysis showed no mutations. Patient received radiation therapy with a good clinical reponse. Results (if a Case Study enter NA) NA. Conclusion Amelanotic S100 negative spindled vaginal melanoma is an unusual presenation of a rare tumor and should be considered in the workup of malignant vaginal tumors with a spindle cell morphology.

Predicting tumor deposits in patients with rectal cancer: Using the models of multiple mathematical parameters derived from diffusion-weighted imaging

PurposeUsing mono-exponential, bi-exponential, and stretched-exponential models of multi-b-value diffusion-weighted imaging (DWI) to predict tumor depositions (TDs) in patients with rectal cancer (RC). Material and methodsThis retrospective study, between January 2018 and November 2021, enrolled 30 TDs-positive and 38 TDs-negative of patients with rectal cancer. The mathematical parameters including ADC from mono-exponential model, D, D* and f from bi-exponential model, and DDC and α from stretched-exponential model, clinical factors (such as age, gender, pathological stage, etc.) and image features (such as length, thickness, location, etc.) from tumor characteristics were obtained to identify the two groups of patients. The results were evaluated by the receiver operating characteristic curve (ROC) analysis and area under the ROC curve (AUC). Multivariate binary logistic regression analysis was conducted to determine the independent risk factors. ResultsThe D* and α values, pt. stage, tumor location, mesorecta fascia (MRF) / peritoneum status and percentage of rectal wall circumference invaded (PCI) were significantly different between the TDs-positive and TDs-negative groups (P < 0.001, P < 0.001, P = 0.029, P = 0.008, P < 0.001 and P = 0.002, respectively), with the AUC were 0.838, 0.901, 0.618, 0.698 0.694 and 0.758, respectively. The D* and α values were proved to be independent risk factors after multivariate binary logistic regression analysis (p = 0.022 and 0.004, respectively). The AUC of the model consisting of the D* and α values was 0.913 (95 % CI 0.820 ∼ 0.968).The combined model constructed by D*, α and tumor location demonstrated superior diagnostic performance, with the AUC, sensitivity, specificity, and accuracy of 0.947 (95 % confidence interval, CI, 0.865–0.987), 0.900, 0.868 and 0.853, respectively. ConclusionMultiple mathematical parameters can be used as preoperative auxiliary diagnostic tools to predict TDs of RC. The combined model constructed by D*, α and tumor location show better diagnostic performance for TDs.

Severe Chronic Rectocolitis Associated With a Characteristic Sunflower Magnetic Resonance Imaging Pattern

Severe Chronic Rectocolitis Associated With a Characteristic Sunflower Magnetic Resonance Imaging Pattern

ICG Enema to Make Rectal Shaving Easier and Safer

Study Objective To use ICG enema to improve the surgical quality during rectal shaving. Design Surgical video. Setting Local GYN MIS hospital, single surgeon. Patients or Participants Patients with solitary rectal DIE nodule. Interventions After complete adhesiolysis and excision of all other pelvic endometriosis lesions except the rectal nodule, 12.5 mg ICG was diluted in 60 cc normal saline. The diluted ICG solution was injected into rectal lumen through anus and was retained in rectum (ICG enema) during the whole rectal shaving procedure. Measurements and Main Results After ICG enema, we started the rectal shaving procedure, carefully mapped the lesion margin, cut into rectal muscular layer with monopolar scissors under pure cutting mode. The submucosa layer can be easily recognized by the ICG green color. As long as we identified the green submucosa layer, we can easily stay precisely between the muscle layer and submucosa layer, keep the green submucosa and mucosa layer intact, with minimal risk of enterotomy. After rectal shaving, the muscular defect of the rectal wall can also be clearly identified by the exposed green submucosa layer. Rectal wall repair can then be confidently performed, transversely re-approximating the seromuscular layer, embedding all the green submucosa layer. Conclusion By ICG enema, staining the mucosa and submucosa layer with green ICG color, we can easily identify the submucosa layer during the rectal shaving procedure. The risk of enterotomy, and incomplete rectal wall repair after shaving can both be minimized. To use ICG enema to improve the surgical quality during rectal shaving. Surgical video. Local GYN MIS hospital, single surgeon. Patients with solitary rectal DIE nodule. After complete adhesiolysis and excision of all other pelvic endometriosis lesions except the rectal nodule, 12.5 mg ICG was diluted in 60 cc normal saline. The diluted ICG solution was injected into rectal lumen through anus and was retained in rectum (ICG enema) during the whole rectal shaving procedure. After ICG enema, we started the rectal shaving procedure, carefully mapped the lesion margin, cut into rectal muscular layer with monopolar scissors under pure cutting mode. The submucosa layer can be easily recognized by the ICG green color. As long as we identified the green submucosa layer, we can easily stay precisely between the muscle layer and submucosa layer, keep the green submucosa and mucosa layer intact, with minimal risk of enterotomy. After rectal shaving, the muscular defect of the rectal wall can also be clearly identified by the exposed green submucosa layer. Rectal wall repair can then be confidently performed, transversely re-approximating the seromuscular layer, embedding all the green submucosa layer. By ICG enema, staining the mucosa and submucosa layer with green ICG color, we can easily identify the submucosa layer during the rectal shaving procedure. The risk of enterotomy, and incomplete rectal wall repair after shaving can both be minimized.

Dosimetric Implications of Margin-Reduced MRI-Guided Stereotactic Body Radiotherapy to the Prostate Bed Following Radical Prostatectomy: Post-Hoc Analysis of a Phase II Study

<h3>Purpose/Objective(s)</h3> Due to the highly deformable and mobile nature of the target volume and adjacent organs at risk (OARs), generous planning target volume (PTV) margins have historically been used in the context of radiotherapy after radical prostatectomy. MRI-guided radiotherapy systems have improved on-board imaging capabilities and the ability to perform automatic beam holds based on pre-specified structures. Herein, we evaluate the dosimetric implications of interfraction variations in the clinical target volumes (CTV) and OARs in patients receiving margin-reduced MRI-guided stereotactic body radiotherapy (SBRT) to the prostate bed. <h3>Materials/Methods</h3> 31 consecutive patients received MRI-guided SBRT to the prostate bed (30 – 34 Gy in 5 fractions) without adaptive planning on a phase II study. The OAR volumes, CTV, and PTV (created using a 3 mm isotropic expansion of the CTV) were retrospectively contoured on on-board 0.35T MRIs obtained prior to each fraction (n=155). Geometric comparisons were made between the initial planning contours and the 5 daily contours for each patient using change in volume and Dice similarity coefficient (DSC) calculations. Coverage of the CTV and PTV was assessed (CTV V95% >93% and PTV V95% >90%), as were bladder and rectal dose constraints (Bladder Dmax <36.7 Gy, Bladder V32.5 Gy <35%, Rectum Dmax <36.7 Gy, Rectum V27.5 Gy <45%, Rectum 32.5 Gy <30%, and Rectal Wall V24 <50%). <h3>Results</h3> The median change in volume was -24.5% (interquartile range [IQR], -35.5 – -2.2%) for the bladder, 6.95% (IQR, -6.94 – 23.0%) for the rectum, -0.2% (IQR, -8.3 – 8.7%) for the rectal wall, 0.48% (IQR, -3.87 – 7.6%) for the CTV, and -0.48% (IQR, -5.12 – 6.53%) for the PTV. The median DSC was 0.79 (IQR, 0.73 – 0.84) for the bladder, 0.76 (IQR, 0.69 – 0.81) for the rectum, 0.35 (IQR, 0.28 – 0.44) for the rectal wall, 0.89 (IQR, 0.83 – 0.93) for the CTV, and 0.90 (IQR, 0.87 – 0.95) for the PTV. 145/155 fractions (93.5%) met the CTV V95% >93% target and 134/155 fractions (86.5%) met both the CTV V95% >93% and PTV V95% >90% targets. When calculated over 5 cumulative fractions, 29/31 patients (93.5%) met the CTV goal of V95% >93%. 62/155 fractions (40%) failed at least one OAR constraint. The mean number of fractions per patient that failed at least one OAR constraint was 2/5 (median, 1; range, 0 – 5). <h3>Conclusion</h3> With MRI-guidance, a reduction of the PTV margin to 3 mm isotropically allows for adequate CTV coverage in over 90% of patients without the need for adaptive planning. However, OAR constraints are not met in 40% of delivered fractions despite meeting all dose constraints at the time of treatment planning. Online dose prediction and, if indicated, adaptive radiotherapy can optimize this to allow for improved OAR protection and potentially allow for further reductions in the PTV expansion while maintaining adequate CTV coverage.

LBODP097 Malignant Struma Ovarii: Long Term Successful Treatment. Outcome

Abstract 18 year old African American female saw her GYN in 9/2008 for abdominal pain. CT: bilateral adnexal masses (10×8 cm left; 6.3×3.1 cm right). Surgical pathology reported a left benign cystic teratoma and right corpus luteum cyst. Pain recurred in 2010. MRI showed: 9×7.5×4 cm right adnexal mass. Repeat surgery was done. Pathology: benign cystic teratoma with focal thyroid tissue - "Struma Ovarii". Abdominal pain recurred yet again in 2012. Sonography revealed a mixed solid/cystic pelvic mass measuring 10.6×7.9×7.6 cm. Exploratory laparotomy 9/2012 revealed a right adnexal mass and widespread peritoneal nodules. Pathology reported follicular tissue with colloid in the nodules - "Peritoneal Strumatosis" suggesting benignity. Upon further review was reclassified as metastatic well differentiated follicular thyroid cancer of ovarian origin with follicular thyroid tissue identified in peritoneal lymph nodes, spleen, bladder and rectal wall. The patient was then referred to endocrinology at our facility. On exam she was clinically euthyroid without thyromegaly or nodularity. Thyroid hormone levels were normal. Antithyroid antibodies were absent. Serum Thyroglobulin (Tg): elevated (229; normal 2-35 ng/ml) as was CA125 (64; normal &amp;lt;21 U/ml). Immunohistochemistry: positive for Tg and Thyroid transcription factor-1. Molecular markers: no mutations in BRAF, RAS, or TP53. In preparation for radioactive iodine (RAI) therapy, total thyroidectomy was performed 4/13/2013 and reported as normal thyroid tissue. Dosimetry findings: very iodine avid tissue with prolonged retention (33% at 6 days). Maximum tolerated dose: 200 mCi. A 62.8 mCi RAI was administered 7/13/2013. Post RAI whole body scan (WBS): numerous focal areas of increased uptake in abdomen and pelvis consistent with metastatic disease. Treatment with L-thyroxine was given to suppress TSH. Follow up WBS 12/26/2013 showed persistent increased uptake in abdomen and pelvis. Serum Tg was high (198. 0). A second RAI dose of 104.8 mCi was given. Post RAI WBS confirmed multiple areas of metastatic disease in abdomen and pelvis. Subsequent serum Tg levels down trended. WBS 11/12/2014: only two residual abnormal foci in the lower neck and one inferior to the liver without abdominal or pelvic foci. Given the dosimetry issue and the reassuring serum Tg levels, surveillance was continued. WBS 9/25/2015: unchanged. Now age 27, WBS 1/26/2022: only residual faint lower neck uptake, resolution of the focus inferior to the liver and no distant foci. Stimulated Tg was normal at 2.2 ng/ml with stimulated TSH &amp;gt;110. 0 uIU/ml. Presentation: No date and time listed

Laparoscopic-Assisted Transanal Total Mesorectal Excision for a Patient with Bowel Endometriosis

<h3>Study Objective</h3> To explore a less-invasive surgical route for patient with bowel endometriosis to undergo segmental colorectal resection. <h3>Design</h3> A case report. <h3>Setting</h3> A university-based tertiary hospital. <h3>Patients or Participants</h3> A 34-year-old female was readmitted two years post-conservative surgery for endometriosis due to consistent digestive dysfunction symptoms. A 3-cm nodule within the muscle layer of lower rectal wall was identified by pelvic MRI. <h3>Interventions</h3> A laparoscopic-assisted transanal total mesorectal excion (TaTME) was performed (a 4-minute video clip included). <h3>Measurements and Main Results</h3> The patient was placed in a Trendelenburg position. For the laparoscopic step, the rectovaginal space was dissected. Lateral, posterior and anterior experitoneal rectal and left sigmoid dissection was performed adequately. Pay attention to protect the ureter and hypogastric nerve. An articulated endoscopic cutter was used to transect the distal rectal segment. For the trans-anal step, the rectal lumen was irrigated, the distal end of rectum was grasped out through anus. A safe margin down to the endometriotic lesion was chosen, 3-0 suture was placed followed by reloaded staplers to close the distal rectal lumen. TME was performed utilizing a "bottom up" approach. An avil was placed inside of proximal sigmoid. Rectosigmoid anastomosis completed successfully by using a circular stapler. No protective ileostomy was adopted. The surgery was uncomplicated with minimal blood loss. Significant improvement of bowel symptoms was reported within the first month postoperatively. During 3-year follow-up period no recurrence of endometriosis or digestive dysfunction symptoms was observed. <h3>Conclusion</h3> As a novel technique, laparoscopic-assisted TaTME shows advantage over laparoscopic surgery, such as better visualization of the distal resection margin while avoiding a bigger abdominal scar. Young women with colorectal endometriosis can benefit for more radical but less invasive surgical outcome. An experienced multidisciplinary team making comprehensive evaluation and discussion before surgery will ensure this technically highly demanding operation feasible and safe.

MRI Visualization of Bowel Endometriosis: A Pilot Study

<h3>Study Objective</h3> To develop and validate a magnetic resonance imaging (MRI)-based nomogram to optimize the preoperative evaluation of bowel endometriosis (BE). <h3>Design</h3> A prospective cohort study. <h3>Setting</h3> University-based hospital. <h3>Patients or Participants</h3> Between 2018 and 2020, patients diagnosed as deep endometriosis were enrolled prospectively and distributed to the development and validation cohort equally. <h3>Interventions</h3> MRI parameters were extracted from T1-weighted and T2-fat saturated images. A Nomogram was developed based on potential predictors for BE by LASSO regression and validated in an external cohort to evaluate the accuracy of predicting BE by generating ROC curve and calibrating curve. <h3>Measurements and Main Results</h3> Among 220 deep endometriosis patients, 154 (70%) were diagnosed as BE. By using logistic regression analysis, thickness of rectal wall (OR=2.45, 95%CI: 1.60-3.73, <i>P</i><0.01) and traction sign (OR=5.62, 95%CI: 1.09-29.00, <i>P</i>=0.04) were integrated in the Nomogram to predict the presence of BE. Predictive accuracy with AUC value 0.94 (95%CI: 0.90-0.98, <i>P</i><0.01) was shown in the development cohort, and AUC=0.94 (95%CI: 0.89-0.98, <i>P</i><0.01) in the validation cohort. A cut-off value of 6.0mm for the thickness of rectal wall resulted in the highest predictive accuracy of BE (sensitivity: 78.6%, specificity: 90.9%, <i>P</i><0.01). <h3>Conclusion</h3> This pilot study indicates the MRI-based Nomogram is efficient for visualization and assessment of BE. The probability of BE tended to be greater in deep endometriosis patients with thickness of rectal wall over 6.0mm

Sunday, June 19, 202210:00 AM - 10:15 AMPO47 Presentation Time: 10:00 AM: Dose Distribution of Permanent Interstitial Brachytherapy (Iodine-125) in Comparison to Temporary Interstitial Brachytherapy (Iridium-192) with a Hydrogel Spacer for Prostate Cancer

<h3>Purpose</h3> Brachytherapy (BT) for prostate cancer can be applied as permanent interstitial brachytherapy BT (LDR, low dose rate) and temporary interstitial brachytherapy BT (HDR, high dose rate), applied also alternatively in many centers. The aim of the study was to analyze the dose distribution in- and outside the prostate. <h3>Methods</h3> The intraoperative dose distribution of 102 LDR-BT patients was compared with the dose distribution of 109 HDR-BT patients (232 HDR-BT fractions). A hydrogel spacer (HS) (10ml) was only applied before HDR-BT. For the analysis of the dose coverage outside the prostate, a 5mm margin was added to prostate volume (PV+). Prostate V100 and V150 denote the PV covered by 100% and 150% of the prescription dose, while prostate D90 and urethra D30 denote the minimum dose in 90% of the PV and 30% of the urethral volume. <h3>Results</h3> The comparison of volume and dose values is shown in the table. HDR-BT patients had on average a slightly larger PV, but considerably larger PV+. The only not significantly different value comparing both methods was prostate V100. LDR-BT was characterized by a considerably more inhomogeneous dose distribution and higher doses to the urethra. However, the minimum dose in 90% of PV+ was lower. As a consequence of the HA in HDR-BT patients, the dose to the rectum was considerably lower. <h3>Conclusion</h3> In comparison to HDR-BT, LDR-BT is characterized by a more inhomogeneous dose inside the prostate, a higher dose to the urethra and a slightly less steep dose drop-off around the prostate. The dose to the rectal wall can be considerably reduced applying the HS.

PP10 Presentation Time: 11:00 AM: Assessment of NASHA Spacer Symmetry for Prostate Radiation Therapy

<h3>Purpose</h3> NASHA (non-animal stabilized hyaluronic acid) is a spacer that can increase the separation between the prostate and anterior rectal wall prior to prostate radiation therapy (RT). Since there is no pre-defined time limit for NASHA spacer injection, physicians can precisely distribute the product within the peri-rectal space. Furthermore, the spacer is highly visible on T2-weighted MR, and generally visible on CT with optimized view settings. We conducted a randomized controlled trial evaluating whether a NASHA spacer improves rectal dosimetry among patients receiving hypofractionated RT (NCT 04189913). The purpose of the study is to evaluate the symmetry of a NASHA spacer among all patients who received the device on that study. <h3>Materials and Methods</h3> We analyzed data for 131 of 136 patients, who were randomized to and received a NASHA spacer on trial (5 datasets were unavailable at the time of analysis). All patients had pre-implant and post-implant CT/MR simulation. We developed an automated system for evaluating symmetry based on a previously published method (Fischer-Valuck, PRO, 2017). Briefly, prostate, rectum and spacer contours that had been prospectively validated by a core laboratory were downloaded. From the prostate center-of-mass, we defined axial slices at mid-gland, 1-cm superior, and 1-cm inferior. For each axial slice, we calculated the center of the spacer (spacer width center) along the transverse axis. Axial slice symmetry scores were assigned based on the distance between the spacer width center and the prostate midline (1 = distance within 1 cm of midline (symmetric), 2L/2R = distance between 1-2 cm from midline, 3L/3R = distance more than 2 cm from midline). Patient-level symmetry scores were assigned based on the number of slices with an asymmetric distribution (1 = none, 2 = 1 of 3 slices with axial score of 2L/2R, 3 = 2 of 3 slices with axial score of 2L/2R, 4 = all 3 slices with axial score of 2L/2R). <h3>Results</h3> The percentages of patients with an axial slice symmetry score of 1 (symmetric) at mid-gland, superior, and inferior planes, were 97%, 98%, and 98%, respectively (see Figure). Following the Fischer rubric, planes without gel were omitted (N=2 mid-gland, N=2 superior and N=9 inferior planes). The percentage of patients with patient-level symmetry scores of 1, 2, 3 and 4, were 95.4%, 2.3%, 1.5%, and 0.8% respectively. <h3>Conclusions</h3> Over 95% of NASHA spacers placed in this prospective trial demonstrated patient-level symmetry. These results suggest that NASHA may also improve rectal dosimetry for prostate brachytherapy. Further study is ongoing to correlate the dosimetry and clinical outcomes to implant quality for these patients.

Endoscopic full-thickness resection with reconstruction of the rectal wall.

Endoscopic submucosal dissection (ESD) achieves high rates of en bloc resection and R0 resection regardless of lesion size and minimizes the risk of recurrence [1].

Surgical Management of Rectal Prolapse - Review Article

Rectal prolapse procidentia is an intussusception of the whole rectal wall through the anal canal, resulting in a portion of the rectum staying periodically or occasionally permanently distal to the anus. Full-thickness prolapse and partial-thickness prolapse are the two kinds of rectal prolapse. Rectal prolapse procidentia is an intussusception of the whole rectal wall through the anal canal, resulting in a portion of the rectum staying periodically or occasionally permanently distal to the anus. It is more frequent in older females. Rectal prolapse was first recorded on papyrus circa 1500 BC. Hippocrates described rectal prolapse therapy as hanging patient’s upside down from a tree, putting sodium hydroxide to the mucosa, and fixing for three days. Today, is mostly treated surgically. Perineal surgical repairs are typically well tolerated; however, they are linked with a greater incidence of recurrence. Abdominal repairs, however, have the lowest recurrence rates. The goal of therapy is to remove the prolapse, cure any related incontinence or constipation issues, and avoid de novo bowel dysfunction. When compared to laparotomy, laparoscopic rectopexy offers fewer side effects, a shorter hospital stays, faster healing, and quicker return to work. This review aims to assess recent updates on different surgical approaches for management of rectal prolapse.

Can Perirectal Spacing Help Reduce GI Toxicity in Patients Undergoing Post-Prostatectomy Radiotherapy?

<h3>Purpose/Objective(s)</h3> To report single institutional feasibility of recto-vesical hyaluronic acid or hydrogel spacer insertion for patients undergoing post prostatectomy radiotherapy (PPRT). <h3>Materials/Methods</h3> Spacer insertion was considered in patients referred for PPRT following an intra or interfascial radical prostatectomy who had no radiological evidence of local recurrence (based on prostate specific membrane antigen positron emission tomography). The spacer was inserted into the perirectal fat between the bladder and anterior rectal wall using a transperineal approach under transrectal ultrasound guidance. Two gold seed fiducial markers were also inserted at the level of the vesico-urethral anastomosis for image guided radiation therapy as per institutional practice. Pre and post spacer computerized tomography planning scans, together with post spacer magnetic resonance imaging scans, were acquired for dosimetric comparison. The prostate bed clinical target volume (CTV) was delineated according to Australian guidelines and the CTV was uniformly expanded by 7mm to create the planning target volume (PTV). The prescribed dose to the prostate bed was 70.2Gy in 1.8 Gy fractions using volumetric arc radiation therapy. The PTV and rectal dosimetry for the two sets of planning scans (PTV 7mm/pre spacer and PTV 7mm/post spacer) were compared. <h3>Results</h3> Sixty-one patients were recruited between 9/18 to 10/21. Fifty-eight patients successfully underwent rectal spacer insertion without postoperative complications. We did not attempt spacer insertion in 3 patients as we were unable to hydrodissect the perirectal fat plane. Only 33 patients had pre spacer planning scans available for dosimetric comparison. The distance between the bladder and rectal wall was increased from ≤1mm to a median of 11mm (9-13) at its greatest extent. The rectal volume for all patients (N=61) receiving 42.2Gy (rV60%), 49.1Gy (rV70%), 56.2 Gy (rV80%), 63.2Gy (rV90%) and 70.2Gy (rV100%)] were 28.1%, 23%, 17.9%, 12.5% and 3.8% respectively. With spacing, a statistically significant reduction was seen on all rectal volume end points from rV60% to rV100% in the 33 patients with both pre and post planning scans (see Table 1). The median follow up was 10.5 months (3-31). The risk of any grade acute GI toxicity was 28% (grade 1 26% and grade 2 2%). The risk of late GI toxicity was 7% (all grade 1 proctitis). <h3>Conclusion</h3> More than 90% of our selected PPRT patients were able to achieve recto-vesical separation, with no surgical complications, resulting in a 43.7% reduction in rV90%. The reduction in acute and late grade 2 GI toxicity is of notable significance, albeit with short follow up. Table 1 Pre and Post Spacer Rectal Dosimetry

The Dosimetric Effects of Long On-Couch Time of Adaptive Ultra-Hypofractionated Radiotherapy for Prostate Cancer Patients on a 1.5 MR Linac

<h3>Purpose/Objective(s)</h3> To quantitatively characterize the dosimetric effects of long on-couch time of adaptive radiotherapy for prostate cancer patients on 1.5-T MR-Linac. <h3>Materials/Methods</h3> Seventeen patients consecutively treated with ultra-hypofractionated radiotherapy (UHF-RT) on 1.5-T MR-Linac were recruited from an on-going prospective phase II trial (NCT05183074). UHF-RT with dose of 36.25Gy in 5 fractions to whole prostate w/o seminal vesicles (SVs) (N=12) was delivered every other day, with a boost dose of 40Gy to whole prostate (CTV4000, N=16). Except the Pre-MR for registration and re-contouring and Position Verification-MR (PV-MR) for dose/position check which were conventionally used in Adapt-To-Shape (ATS) workflow, we also collected 3D-MR during beam-on phase (Bn-MR) and after RT (Post-MR). For each fraction, the contours of targets and organs-at-risk (OARs) on PV-MR, Bn-MR and Post-MR were projected from the Pre-MR by deformable registration, and manually adapted by the physician, followed by dose-recalculation of the ATS plan. The dose parameters of target volumes and OARs on each scan were generated in a commercially available software for final analysis. <h3>Results</h3> In total, 290 MR-scans were collected, including 85 Pre-MR, 85 PV-MR, 49 Bn-MR and 71 Post-MR scans, respectively. For each fraction, the volume differences of prostate and CTV on different scans were less than 3.0cc, indicating good alignment of target contouring. With median 49 (24-78) minutes of on-couch time, the mean PTV-V95% (34.4Gy) of plans on PV-MR, Bn-MR and Post-MR was 97.69±2.03%, 97.04±2.29%, and 96.82±2.59%, respectively, compared with 99.27±0.75% of ATS plan. Furthermore, the mean CTV-V100% (36.25Gy) of plans on PV-MR, Bn-MR and Post-MR was 99.32±1.20%, 98.59±1.84% and 98.65±1.87, respectively, compared with 99.93±0.30% of ATS plan. With excellent dose coverage of prostate-V100% (36.25Gy) (99.73±0.79% on PV-MR, 99.41±1.35% on Bn-MR and 99.38±1.35% on post-MR), the main reason of lower CTV-V100% was due to mild underdose of SVs (96.97±6.26% on PV-MR, 93.62±12.94% on Bn-MR and 94.69±9.22% on post-MR). With comparison to values of ATS plan, the actual dose of rectum wall during the whole workflow also varied, with mean △V38_Gy of 0.23±0.28cc on PV-MR, 0.41±0.51cc on Bn-MR and 0.39±0.52cc on post-MR, with mean △V36_Gy of 0.27±0.57cc on PV-MR, 0.39±0.71cc on Bn-MR and 0.30±0.68cc on post-MR, respectively. However, the V29_Gy of rectum wall increased by >15% was only observed in one scan. On the contrary, no obvious increase of bladder wall dose was seen due to gradual growth of bladder over the workflow. <h3>Conclusion</h3> This dosimetry analysis demonstrated reliable dose coverage of target volumes during beam-on period with adaptive ATS workflow on 1.5-T MR-Linac. The 3 mm CTV-PTV margin applied in our study have proven to be large enough for prostate irradiation, but might be insufficient for SVs incidentally. More attention should be paid to restrict the rectum wall high dose when optimizing ATS plan.

Toxicity and Patient Reported Quality of Life Outcomes Following Prostate SBRT with Focal Boost to MRI Identified Prostate Cancer Lesions: Results of a Phase II Trial

<h3>Purpose/Objective(s)</h3> A focused boost to MRI identified prostate cancer lesions treated with radiotherapy has been shown to improve biochemical disease control without increased toxicity in standard fractionated radiation treatment. Prostate cancer is known to be sensitive to higher radiation doses per fraction and thus stereotactic body radiotherapy (SBRT) has become an increasingly popular treatment method. In this prospective phase II trial, we investigated the toxicity and patient reported quality of life outcomes in patients treated with SBRT to the prostate gland and a simultaneous focal boost to MRI identified intraprostatic lesions while also de-escalating dose to the adjacent organs at risk. <h3>Materials/Methods</h3> Eligible patients included low- or intermediate- risk prostate cancer (Gleason score ≤ 7, PSA ≤20, T stage ≤2b). SBRT was prescribed to 40 Gy in 5 fractions delivered every other day to the prostate, with areas of high disease burden (MRI-identified PI-RADS 4 or 5 lesions) escalated to 42.5-45 Gy and areas overlapping organs at risk (within 2 mm of urethra, anterior rectal wall, and bladder base) constrained to 36.25 Gy (n=98). Patients without a pre-treatment MRI were treated to dose of 37.5 Gy with no focal boost (n=14). Acute and late toxicity were graded using RTOG modified toxicity scales. Patient-reported outcome and quality of life was assessed using the AUA-IPSS lower urinary tract symptom score, IIEF-5 erectile function, and EPIC-26 surveys. Statistical testing was performed in statistical software. <h3>Results</h3> From 2015 to 2022, a total of 112 patients were enrolled with a median follow-up of 36 months. No acute or late grade 3+ GI or GU toxicity was observed. Within the focal boost arm, acute grade 2 GU toxicity during treatment or at 6-week follow-up was seen in 26% of patients. Acute grade 2 GI toxicity was seen in 1 patient. Cumulative late grade 2 GU toxicity was 8%. Rate of alpha blocker medication use following treatment was 26%. Cumulative late grade 2 GI toxicity was 2.3%. Patient reported outcomes showed no significant changes from baseline IPSS lower urinary tract, IIEF erectile function, or EPIC-26 urinary incontinence, urinary irritative, gastrointestinal, or sexual domain quality of life scores following treatment (p >0.05 for all tests via RANOVA). Two patients have had a biochemical recurrence to date, at 42 months and 60 months post treatment. <h3>Conclusion</h3> SBRT to a dose of 40 Gy to the prostate gland with a focal boost up to 45 Gy is well tolerated with no observed grade 3 toxicity and similar rates of acute and late grade 2 GI and GU toxicity as seen in other SBRT regimens without intraprostatic dose boost. Moreover, no significant changes were seen in patient reported urinary, bowel, or sexual outcomes from pre-treatment baseline at any follow-up date. Biochemical control data continue to mature but few treatment failures have been observed to date.