BACKGROUND:Clinical guidelines recommend 30-day extended venous thromboembolism (VTE) prophylaxis after major abdominal cancer surgery, though equipoise exists among experts. We developed a patient decision aid (PtDA) to support patient decision-making and evaluated its perioperative usability. METHODS:Patients undergoing major abdominal cancer surgery and discharging healthcare professionals at two academic centers were recruited. Usability was assessed using the Post Study System Usability Questionnaire (PSSUQ) for patients and the Pragmatic Assessment Tool (pCAT) for clinicians. PtDA revisions occurred iteratively every three participants. RESULTS:Of 108 eligible patients, 79 (73%) enrolled, and 20 (25%) completed the PtDA. Among them, 65% used it to decide on extended VTE prophylaxis. The median PSSUQ score was 2 (IQR 2-3.75). Fifteen clinicians completed the pCAT, reporting more facilitators than barriers to its implementation. CONCLUSION:The PtDA was highly useable, but low completion rates suggest systemic barriers that require further study to improve implementation.

Background/Objectives: Merkel cell carcinoma (MCC) is an uncommon but aggressive skin malignancy with a rising incidence. Limited data exist on the survival of MCC patients in Canada. This study analyzes the survival of patients diagnosed with MCC in Canada between 2000 and 2018 compared to those reported by the American Joint Committee on Cancer (AJCC) 8th edition. Risk factors included in the database were sex, age, and immunosuppression. Methods: We conducted a multicenter retrospective cohort study including patients diagnosed with stage I–IV MCC aged ≥18 from 10 Canadian university centers and three provinces. We evaluated differences in survival compared to the cohort included in the AJCC 8th edition. Results: Among 899 patients diagnosed with MCC in Canada, 327 (36.4%) had stage I, 195 (21.7%) had stage II, 305 (33.9%) had stage III, and 72 (8.0%) had stage IV at presentation. When examining risk factors, 61.1% (549) were male, 10.2% (92) were immunosuppressed, and age at diagnosis was 75 years (±11). The five-year overall survival for patients diagnosed in Canada at stage I was 56.8%, stage IIA 54.0%, stage IIB 28.0%, stage IIIA 52.7%, stage IIIB 40.2%, and stage IV 13.9%. Conclusions: Survival from MCC is low in Canada across all stages. Compared to the AJCC 8th edition, patients diagnosed with MCC in Canada have similar survival rates, except for patients diagnosed with stage IIIB, who have lower survival rates in the AJCC 8th edition. Further research is needed to improve the survival of this rare malignancy.

BACKGROUND:Perivascular epithelioid cell tumors (PEComa) are a rare family of mesenchymal tumors that include several subtypes. There are very limited data describing the natural history of patients with extra-visceral retroperitoneal PEComas of the retroperitoneum. The aim of this study is to describe the clinical features, treatment patterns, outcomes, and diagnostic challenges of primary extra-visceral retroperitoneal or abdominopelvic PEComa over the past decade. PATIENTS AND METHODS:This is a retrospective analysis of all extra-visceral, non-renal, retroperitoneal, or abdominopelvic PEComas treated at participating centers over the past 10 years. RESULTS:A total of 77 patients from 13 centers were included. The median age at diagnosis was 56 years (range 18-81 years); 73% were female. The median size was 9 cm. The tumor was classified as a PEComa not otherwise specified (NOS) in 55 (71%), sclerosing PEComa in 11 (15%), and angiomyolipoma (AML) in 11 (15%). Treatment intent was curative in 59 (77%) patients. Adjuvant radiation was given in five (8%) patients, and (neo)adjuvant systemic therapy was given to six (10%). Of those who did not undergo curative intent treatment, four (22%) patients had metastatic disease and three (17%) had primary unresectable disease. With a median follow-up of 26 months (2.3-147 months), 24 (40%) of the 59 patients having curative treatment had recurred. Recurrence rates differed by subtype, with 20 (37%) of the PEComa NOS group, 3 (27%) of the sclerosing PEComa group, and 1 (9%) of the AML group developing recurrence. The estimated 5-year OS of the whole cohort was 63% and 75% for the curative intent group. CONCLUSIONS:Retroperitoneal and abdominopelvic PEComas show distinct behaviors by subtype. PEComa NOS had the highest recurrence and mortality, sclerosing PEComa showed intermediate risk, and AML was indolent. Histological classification is essential for prognosis and management.

The management and survival outcomes of patients with Merkel cell carcinoma (MCC) in Canada are currently unknown. The objective of this study was to investigate the management and outcomes of patients diagnosed with MCC in Canada from 2000 to 2018. This retrospective cohort study evaluates management and temporal survival differences among patients diagnosed with MCC in ten large urban university centers in three provinces during three periods: 2000–2005, 2006–2011, and 2012–2018. There were 899 patients included with a median follow-up of 22.8 months. There were no significant changes in patient and tumor characteristics between the three periods. There were increases in the use of radiologic staging (2000–2005, 53.4

Background: Clinical guidelines recommend patients receive extended duration thromboprophylaxis for 30 days following major abdominopelvic cancer surgery. There is equipoise regarding this recommendation amongst providers and patients. We developed a risk-stratified patient decision aid (PtDA) for patients undergoing major abdominopelvic cancer surgery considering extended duration thromboprophylaxis. We previously demonstrated the PtDA was acceptable to patients and clinicians and enhanced decision-making quality. However, the PtDA made was difficult to use in the perioperative setting. The objective of this study was to evaluate and improve the usability of the PtDA in the perioperative setting. Methods: We used an iterative process guided by a user-centered design framework. Consecutive patients undergoing major abdominopelvic cancer surgery from two major cancer centers in Canada, The Ottawa Hospital Cancer Center (TOHCC) and CancerCare Manitoba (CCMB), were recruited. Healthcare professionals involved in discharging patients who completed the PtDA were also recruited. Recruitment rate was defined as the number of total patients approached divided by the total eligible patients who consented to be contacted. Eligible and consented patients were invited to complete the PtDA and the Post Study System Usability Questionnaire (PSSUQ), and to record their decision regarding extended duration thromboprophylaxis. Adherence rate was defined as the number of eligible patients thereafter who actually completed the PSSUQ. Usability was also assessed by healthcare professionals discharging patients using the Consolidated Framework for Implementation Research (CFIR) Barrier Buster Tool. Results: Across both sites patients were recruited from November 2023 until May 2024. 108 consecutive patients were approached with study details, 22 refused to be contacted and 7 were ineligible The recruitment rate was 73% (79/108). Of the eligible and consented patients, the adherence rate was 25% (20/79). Overall, 15 patients from TOHCC and 5 from CCMB used the PtDA to help their decision regarding extended duration thromboprophylaxis. Eight (40%) patients were males, and 12 (60%) were females. Out of the 20 patients who used the PtDA, 18 (90%) completed the PSSUQ and reported their decision regarding extended duration thromboprophylaxis: 13 (65%) patients made a decision using our PtDA compared to 5 (25%) who preferred not to decide. Among the 13 who made a decision, 7 (54%) decided not to take extended duration thromboprophylaxis and 6 (46%) decided to take extended duration thromboprophylaxis. Regarding usability, the overall median score was 2 (range 2 - 6) on the PSSUQ. The usefulness subdomain median score was 3 (range 2 - 7). The median quality of information subdomain score was 2 (1 - 7). The median quality of design score was 2 (1 - 7). A total of 15 healthcare professionals were involved in discharging patients who used the PtDA and completed the PSSUQ. All healthcare professionals were resident physicians. Eight (53%) were males and seven (47%) were females. All 15 (100%) completed the follow-up CFIR Tool. From the 12 factors evaluated in the CFIR Tool, healthcare professionals identified a median number of six (range 1-11) facilitators and a median number of one (range 0-8) barrier. The factor most commonly identified as a facilitator was that the use of the PtDA is aligned with the healthcare professional's value, and the factor most commonly identified as a barrier was the lack of access to data to track the changes in outcomes related to the PtDA. Conclusion: The PtDA was found to be usable by patients based on PSSUQ scores. Healthcare professionals reported more facilitators than barriers to using the PtDA in the perioperative setting. However, few patients eligible for the study completed the PtDA in both centers, which may suggest ongoing challenges with implementing PtDAs in the perioperative setting. Additional research is required to assess clinical outcomes associated with its use in routine practice for patients, and address implementation barriers for providers.

Multi-visceral resection often is used in the treatment of retroperitoneal sarcoma (RPS). The morbidity after distal pancreatectomy for primary pancreatic cancer is well-documented, but the outcomes after distal pancreatectomy for primary RPS are not. This study aimed to evaluate morbidity and oncologic outcomes after distal pancreatectomy for primary RPS. In this study, 26 sarcoma centers that are members of the Trans-Atlantic Australasian Retroperitoneal Sarcoma Working Group (TARPSWG) retrospectively identified consecutive patients who underwent distal pancreatectomy for primary RPS from 2008 to 2017. The outcomes measured were 90-day severe complications (Clavien-Dindo ≥ 3), postoperative pancreatic fistula (POPF) rate, and oncologic outcomes. Between 2008 and 2017, 280 patients underwent distal pancreatectomy for primary RPS. The median tumor size was 25 cm, and the median number of organs resected, including the pancreas, was three. In 96% of the operations, R0/R1 resection was achieved. The 90-day severe complication rate was 40 %. The grades B and C POPF complication rates were respectively 19% and 5% and not associated with worse overall survival. Administration of preoperative radiation and factors to mitigate POPF did not have an impact on the risk for the development of a POPF. The RPS invaded the pancreas in 38% of the patients, and local recurrence was doubled for the patients who had a microscopic, positive pancreas margin (hazard ratio, 2.0; p = 0.042). Distal pancreatectomy for primary RPS has acceptable morbidity and oncologic outcomes and is a reasonable approach to facilitate complete tumor resection.

# 01. Operative classification of ventral abdominal hernias: new and practical classification {#article-title-2} Ventral hernias of the abdomen are defined as a noninguinal, nonhiatal defect in the fascia of the abdominal wall. Unfortunately, there is not currently a universal classification system

9583 Background: There is controversy regarding sentinel lymph node biopsy (SLNB) in clinically node-negative Merkel Cell Carcinoma (MCC). We compared MCC recurrence and survival between patients who did versus did not undergo a SLNB. Methods: Patients with MCC across 13 Canadian centers were reviewed, from 2000-2018. Of a total cohort of 750 patients, 485 had clinically node-negative disease at presentation. A propensity score was created. The association between SLNB and local, regional and distant recurrence, and cancer-specific and overall survival were evaluated using competing risks and Cox proportional hazards regression. Results: 195 patients (40.2%) underwent a SLNB. SLNB was performed more commonly in younger, healthier patients with MCC located in the extremities or torso (Table). The results of 177 SLNBs were available; 60 (33.9%) were positive. SLNB-positive patients underwent completion dissection (n=15, 25%), completion dissection and nodal radiation (n=22, 36.7%), nodal radiation alone (n=18, 30%) or observation (n=5, 8.3%). Patients who did not undergo a SLNB underwent nodal radiation alone (n=40, 13.8%) or observation (n=250, 86.2%). The median follow-up was 2.7 years (range 0.2-14.4). The regional recurrence rate was 14.5% (n=17) among SLNB-negative versus 15% (n=9) among SLNB-positive patients. Among patients who did not undergo a SLNB, the regional recurrence rate was 25.2% (n=63) among those who underwent observation and 15% (n=6) among those who received nodal radiation alone. After propensity score matching, SLNB patients had a lower risk of regional recurrence (sHR 0.54 95% CI 0.34-0.86 p=0.01) and improved overall survival (HR 0.32 95% CI 0.23-0.45 p<0.01), but there was no difference in local recurrence (sHR 0.92 95% CI 0.50-1.69 p=0.79), distant recurrence (sHR 0.88 95% CI 0.52-1.49 p=0.63), or cancer-specific survival (HR 0.67 95% CI 0.31-1.45 p=0.31). Conclusions: SLNB is associated with a reduced risk of regional recurrence and improved overall survival. The role of SLNB in selecting patients for emerging therapies, such as immunotherapy, needs to be evaluated. [Table: see text]

Despite advances in adjuvant immuno- and targeted therapies, the risk of relapse for stage III melanoma remains high. With 43 active entries on clinicaltrials.gov (8 July 2020), there is a surge of interest in the role of contemporary therapies in the neoadjuvant setting. We conducted a systematic review of trials performed in the last decade evaluating neoadjuvant targeted, immuno- or intralesional therapy for resectable stage III or IV melanoma. Database searches of Medline, Embase, and the Cochrane Central Register of Controlled Trials were conducted from inception to 13 February 2020. Two reviewers assessed titles, abstracts, and full texts. Trials investigating contemporary neoadjuvant therapies in high-risk melanoma were included. Eight phase II trials (4 randomized and 4 single-arm) involving 450 patients reported on neoadjuvant anti-BRAF/MEK targeted therapy (3), anti-PD-1/CTLA-4 immunotherapy (3), and intralesional therapy (2). The safest and most efficacious regimens were dabrafenib/trametinib and combination ipilimumab (1 mg/kg) + nivolumab (3 mg/kg). Pathologic complete response (pCR) and adverse events were comparable. Ipilimumab + nivolumab exhibited longer RFS. Contemporary neoadjuvant therapies are not only safe, but also demonstrate remarkable pCR and RFS—outcomes which are regarded as meaningful surrogates for long-term survival. Studies defining predictors of pCR, its correlation with oncologic outcomes, and phase III trials comparing neoadjuvant therapy to standard of care will be crucial.

BACKGROUND:Emergency general surgery (EGS) services are gaining popularity in Canada as systems-based approaches to surgical emergencies. Despite the high volume, acuity and complexity of the patient populations served by EGS services, little has been reported about the services' structure, processes, case mix or outcomes. This study begins a national surveillance effort to define and advance surgical quality in an important and diverse surgical population.METHODS:A national cross-sectional study of EGS services was conducted during a 24-hour period in January 2017 at 14 hospitals across 7 Canadian provinces recruited through the Canadian Association of General Surgeons Acute Care Committee. Patients admitted to the EGS service, new consultations and off-service patients being followed by the EGS service during the study period were included. Patient demographic information and data on operations, procedures and complications were collected.RESULTS:Twelve sites reported resident coverage. Most services did not include trauma. Ten sites had protected operating room time. Overall, 393 patient encounters occurred during the study period (195/386 [50.5%] operative and 191/386 [49.5%] nonoperative), with a mean of 3.8 operations per service. The patient population was complex, with 136 patients (34.6%) having more than 3 comorbidities. There was a wide case mix, including gallbladder disease (69 cases [17.8%]) and appendiceal disease (31 [8.0%]) as well as complex emergencies, such as obstruction (56 [14.5%]) and perforation (23 [5.9%]).CONCLUSION:The characteristics and case mix of these Canadian EGS services are heterogeneous, but all services are busy and provide comprehensive operative and nonoperative care to acutely ill patients with high levels of comorbidity.

BACKGROUND:Bariatric surgery in Canada is primarily delivered within publicly funded specialty clinics. Previous studies have demonstrated that bariatric surgery is superior to intensive medical management for reduction of weight and obesity-related comorbidities. Our objective was to compare the effectiveness and safety of laparoscopic Roux-en-Y gastric bypass (RYGB), sleeve gastrectomy (LSG) and adjustable gastric banding (LAGB) in a publicly funded, population-based bariatric treatment program.METHODS:We followed consecutive bariatric surgery patients for 2 years. The primary outcome was weight change (in kilograms). Between-group changes were analyzed using multivariable regression. Last-observation-carried-forward imputation was used for missing data.RESULTS:We included 150 consecutive patients (51 RYGB; 51 LSG; 48 LAGB) in our study. At baseline, mean age was 43.5 ± 9.5 years, 87.3% of patients were women, and preoperative body mass index (BMI) was 46.2 ± 7.4. Absolute and relative (% of baseline) weight loss at 2 years were 36.6 ± 19.5 kg (26.1 ± 12.2%) for RYGB, 21.4 ± 16.0 kg (16.4 ± 11.6%) for LSG and 7.0 ± 9.7 kg (5.8 ± 7.9%) for LAGB (p < 0.001). Change in BMI was greater for the RYGB (-13.0 ± 6.6) than both the LSG (-7.6 ± 5.7) and the LAGB (-2.6 ± 3.5) groups (p < 0.001). The reduction in diabetes, hypertension and dyslipidemia was greater after RYGB than after LAGB (all p < 0.05). There were no deaths. The anastomotic and staple leakage rate was 1.3%.CONCLUSION:In a publicly funded, population-based bariatric surgery program, RYGB and LSG demonstrated greater weight loss than the LAGB procedure. Bypass resulted in the greatest reduction in obesity-related comorbidities. All procedures were safe.

The optimal bariatric surgical procedure for severely obese individuals receiving bariatric care is currently unknown. The objective of this population-based prospective cohort study was to compare the effectiveness of laparoscopic Roux-en-Y gastric bypass (LRYGB), laparoscopic sleeve gastrectomy (LSG), and laparoscopic adjustable gastric banding (LAGB) in severely obese patients.