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3515 Background: Neoadjuvant radiochemotherapy is the standard treatment for locally advanced rectal cancer. However, radiation therapy can lead to bowel, urinary and sexual dysfunction. The study aims to clarify whether locally advanced rectal cancer with a distance of 6 to 12 cm from the anus with negative circumferential margins (CRM) predicted by MRI can be exempted from preoperative radiotherapy. Methods: PSSR (NCT02121405), a multicentre, randomized, open-label, non-inferiority, phase 3 trial, was done across 10 hospitals in China. Patients aged from 18 to 75 years with locally advanced rectal cancer (including all cT3/4 and/or Nany) with negative MRI-predicted CRM and tumor distance of 6 to 12 cm from anus were randomly assigned (1:1), by central randomization, to intervention group (surgery directly, in which positive CRM was supplemented with chemoradiotherapy, negative CRM received adjuvant chemotherapy according to surgical pathologic staging), or control group (neoadjuvant chemoradiotherapy then underwent surgery and adjuvant chemotherapy). The primary endpoint is the rate of 3-year disease-free survival (DFS). A sample size of 350 was set according to the original non-inferiority margin of 15% for the difference of rates for 3-year DFS, which was changed to 5% under the Data Safety Monitoring Board (DSMB) suggestion after an interim analysis. The efficacy analysis followed the per-protocol (PP) principle. Results: From December 2015 to February 2021, 299 patients were recruited. DSMB stopped this trial due to the difference of 3-year DFS’s rate between two groups more than 5% at the interim analysis in July 2021. A total of 275 were included for the final analysis. Based on the PP dataset, 238 patients followed the original protocol (135 patients in the intervention group and 103 patients in the control group). Patients who had positive CRM were 2(1.5%) and 1(1.0%) in two groups, respectively ( P= 1.00). After a median follow-up of 34.6 (IQR: 18.2-45.7) months, a total of 42 patients had positive events (30 patients in the intervention group and 12 patients in the control group). There were 5 (3.7%) patients with local recurrence in the intervention group ( P= 0.062). Patients with pathological complete response (pCR) and near pCR were 19 (18.4%) and 21 (20.4%) in the control group. The rate of 3-year DFS was 81.1% (77.3%-84.9%) (HR = 2.02, 95%CI: 1.01-4.06, P= 0.048) in the intervention group and 86.6% (82.7%-90.5%) in the control group, with difference of 5.4% (5.3%-5.6%), which did not meet the criteria for non-inferiority. Conclusions: In terms of DFS, initial surgery was inferior to conventional preoperative radiochemotherapy for locally advanced middle rectal cancer with MRI negative circumferential margin. Clinical trial information: NCT02121405.

For double network (DN) hydrogels, their performance can be tuned by adjusting the interaction between their two networks. A novel DN hydrogel toughening approach is proposed by employing Janus nanoparticles (JNs) as crosslinkers to gain a conjoined‐network hydrogel. First, a kind of JNs modified by amino groups and quaternary ammonium salt is synthesized, named R3N+‐JN‐NH2. The DN hydrogel is fabricated based on ionic coordination between calcium chloride (CaCl2) and sodium alginate (Alg), as well as covalent (benzoic imine) between glycol chitosan (GC) and benzaldehyde‐capped poly(ethylene oxide) (BzCHO−PEO−BzCHO). Based on the same covalent and ionic dynamic crosslinking mechanism, the added R3N+‐JN‐NH2 interacts with two networks to promote crosslinking to form a dually crosslinked structure. The R3N+‐JN‐NH2 effectively provides more energy dissipation, and the hydrogel with conjoined networks shows better compression resistance.

Purpose: Our study was aimed to depict and summarize the technique, short and long term outcomes of laparoscopic transverse colectomy in one single clinical center and compare with laparoscopic hemicolectomy.Methods: This was a retrospective cohort study of patients with mid-transverse colon cancer in one single clinical center from February 2012 to October 2020. The enrolled patients were divided into two groups undergoing laparoscopic transverse colectomy and laparoscopic hemicolectomy, respectively. The intraoperative, postoperative complications, oncological outcomes and functional outcomes were compared between the two groups. The primary endpoint was disease free survival (DFS).Results: The study enrolled 70 patients with 40 patients undergoing laparoscopic transverse colectomy and 30 patients undergoing hemicolectomy. The intraoperative accidental hemorrhage and multiple organ resection occurred similarly in the two groups. In transverse colectomy, caudal-to-cephalic approach was likely to harvest more lymph nodes although require more operation time than cephalic-to-caudal approach (23.1(14.3) versus 13.4(5.4) lymph nodes, P=0.004; 184.3(37.1)min versus 146.3(44.4)min, P=0.012). The laparoscopic transverse colectomy was marginally associated with lower incidence of overall postoperative complications and shorter postoperative hospital stay although without statistical significance (8(20.0%) versus 12(40.0%), P=0.067; 7(5-12) VS 7(5-18), P=0.060). The 3-year DFS showed no significant difference (3-year DFS 89.7% in transverse colectomy versus 89.9% in hemicolectomy, P=0.688) between the two groups. The alternating consistency of defecation occurred significantly less after transverse colectomy (15(51.7%) VS 20(80.0%), P=0.030). Conclusions: The laparoscopic transverse colectomy is technically, oncologically and functionally feasible for mid-transverse colon cancer. Performing the caudal-to-cephalic approach might be more advantageous in lymphadenectomy.

(1) Background: The difficulty of pelvic operation is greatly affected by anatomical constraints. Defining this difficulty and assessing it based on conventional methods has some limitations. Artificial intelligence (AI) has enabled rapid advances in surgery, but its role in assessing the difficulty of laparoscopic rectal surgery is unclear. This study aimed to establish a difficulty grading system to assess the difficulty of laparoscopic rectal surgery, as well as utilize this system to evaluate the reliability of pelvis-induced difficulties described by MRI-based AI. (2) Methods: Patients who underwent laparoscopic rectal surgery from March 2019 to October 2022 were included, and were divided into a non-difficult group and difficult group. This study was divided into two stages. In the first stage, a difficulty grading system was developed and proposed to assess the surgical difficulty caused by the pelvis. In the second stage, AI was used to build a model, and the ability of the model to stratify the difficulty of surgery was evaluated at this stage, based on the results of the first stage; (3) Results: Among the 108 enrolled patients, 53 patients (49.1%) were in the difficult group. Compared to the non-difficult group, there were longer operation times, more blood loss, higher rates of anastomotic leaks, and poorer specimen quality in the difficult group. In the second stage, after training and testing, the average accuracy of the four-fold cross validation models on the test set was 0.830, and the accuracy of the merged AI model was 0.800, the precision was 0.786, the specificity was 0.750, the recall was 0.846, the F1-score was 0.815, the area under the receiver operating curve was 0.78 and the average precision was 0.69; (4) Conclusions: This study successfully proposed a feasible grading system for surgery difficulty and developed a predictive model with reasonable accuracy using AI, which can assist surgeons in determining surgical difficulty and in choosing the optimal surgical approach for rectal cancer patients with a structurally difficult pelvis.

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Background: To evaluate the efficacy and treatment related morbidity of neoadjuvant chemoradiotherapy and surgery in elderly patients (aged 75 years or older) with locally advanced rectal cancer (LARC). Methods: We reviewed clinical records of elderly patients with LARC treated with neoadjuvant chemoradiotherapy from January 2008 to June 2017 at our institute. A dose of 45-50Gy in 25 fractions was delivered to pelvis. The primary tumor received a dose of 55Gy concomitantly. The concurrent chemotherapy included capecitabine alone and capecitabine plus oxaliplatin (Xelox). Surgery was performed for suitable patients at least 6 weeks after neoadjuvant treatment. Overall survival (OS), disease specific survival (DSS), disease free survival (DFS) and local control (LC) were calculated with Kaplan-Meier method. Univariate and multivariate analyses were performed with cox proportional hazards model. A two-side value of P<0.05 was defined as statistical significance. Results: A total of 85 patients were enrolled in this study, the median age was 80 years old (range: 75-90 years). After neoadjuvant treatment, surgery was performed in 56 patients (65.9%). Twelve patients (21.4%) obtained pathological complete response (pCR). The incidence of grade 3 or greater acute hematological, gastrointestinal and genitourinary toxicities were 10.7%, 5.2% and 1.8%, respectively. Seven patients (12.5%) experienced postoperative complications. The median follow-up duration was 35.7 months (range: 4.3-100.3 months), The 3-year OS, DSS, DFS and LC were 68.9%, 75.8%, 68.2% and 83.9%, respectively. Surgery was a significant prognostic factor for OS (HR: 10.092, 95%CI: 2.082-36.351, P<0.001), DSS (HR: 4.681, 95%CI: 1.971-11.113, P<0.001), DFS (HR: 5.509, 95%CI: 1.964-15.454, P=0.001) and LC (HR: 3.089, 95%CI: 1.244-11.669, P=0.019). Clinical T downstaging after neoadjuvant treatment was significantly associated with better DFS (HR: 4.554, 95%CI: 1.601-12.958, P=0.004). Conclusion: In patients aged 75 years or older with LARC, neoadjuvant chemoradiotherapy followed by surgery was well tolerated with promising survival outcomes, which should be strongly suggested if medically suitable.