Objective: To compare neoadjuvant chemotherapy (nCT) with CAPOX alone versus neoadjuvant chemoradiotherapy (nCRT) with capecitabine in locally advanced rectal cancer (LARC) with uninvolved mesorectal fascia (MRF). Background Data: nCRT is associated with higher surgical complications, worse long-term functional outcomes, and questionable survival benefits. Comparatively, nCT alone seems a promising alternative treatment in lower-risk LARC patients with uninvolved MRF. Methods: Patients between June 2014 and October 2020 with LARC within 12 cm from the anal verge and uninvolved MRF were randomly assigned to nCT group with 4 cycles of CAPOX (Oxaliplatin 130 mg/m2 IV day 1 and Capecitabine 1000 mg/m2 twice daily for 14 d. Repeat every 3 wk) or nCRT group with Capecitabine 825 mg/m² twice daily administered orally and concurrently with radiation therapy (50 Gy/25 fractions) for 5 days per week. The primary end point is local-regional recurrence-free survival. Here we reported the results of secondary end points: histopathologic response, surgical events, and toxicity. Results: Of the 663 initially enrolled patients, 589 received the allocated treatment (nCT, n=300; nCRT, n=289). Pathologic complete response rate was 11.0% (95% CI, 7.8-15.3%) in the nCT arm and 13.8% (95% CI, 10.1-18.5%) in the nCRT arm (P=0.33). The downstaging (ypStage 0 to 1) rate was 40.8% (95% CI, 35.1-46.7%) in the nCT arm and 45.6% (95% CI, 39.7-51.7%) in the nCRT arm (P=0.27). nCT was associated with lower perioperative distant metastases rate (0.7% vs. 3.1%, P=0.03) and preventive ileostomy rate (52.2% vs. 63.6%, P=0.008) compared with nCRT. Four patients in the nCT arm received salvage nCRT because of local disease progression after nCT. Two patients in the nCT arm and 5 in the nCRT arm achieved complete clinical response and were treated with a nonsurgical approach. Similar results were observed in subgroup analysis. Conclusions: nCT achieved similar pCR and downstaging rates with lower incidence of perioperative distant metastasis and preventive ileostomy compared with nCRT. CAPOX could be an effective alternative to neoadjuvant therapy in LARC with uninvolved MRF. Long-term follow-up is needed to confirm these results.

Background: Increasing evidence suggests that the immune score is significantly associated with cancer prognosis. However, the prognostic role of primary tumor immune score in colorectal cancer liver metastases (CRLM) after hepatectomy in Chinese patients has not been reported. The present study is designed to investigate whether the immune score of primary tumor can predict the postoperative survival of liver metastases in Chinese patients.Methods: A total of 131 patients diagnosed with CRLM were included, and the corresponding primary tumor and liver metastasis specimens were acquired. An immune score ranging from 0 to 4 was established based on the counts and densities of CD3 + and CD8 + T cells in the core tumor (CT) and the invasive margin (IM). Relapse-free survival (RFS) and overall survival (OS) were analyzed by Kaplan-Meier curves to assess the prognostic role of primary tumor immune score. Furthermore, we conducted a comprehensive search of the Gene Expression Omnibus (GEO) and selected stage IV colorectal cancer (CRC) patients with liver metastasis to compare the tumor-infiltrating T cell profiles of the primary tumor and liver metastases by CIBERSORT.Results: Patients with high immune scores in the primary tumor has no significantly better RFS and OS after hepatectomy than those with low immune scores [

OBJECTIVES:This study aimed to evaluate the safety and efficacy of a new nickel-titanium shape memory alloy compression anastomosis ring, NiTi CAR 27, in constructing an anastomosis for colorectal cancer resection compared with conventional staples.METHODS:In total, 234 consecutive patients diagnosed with colorectal cancer receiving sigmoidectomy and anterior resection for end-to-end anastomosis from May 2010 to June 2012 were retrospectively analyzed. The postoperative clinical parameters, postoperative complications and 3-year overall survival in 77 patients using a NiTi CAR 27 compression ring (CAR group) and 157 patients with conventional circular staplers (STA group) were compared.RESULTS:There were no statistically significant differences between the patients in the two groups in terms of general demographics and tumor features. A clinically apparent anastomotic leak occurred in 2 patients (2.6%) in the CAR group and in 5 patients (3.2%) in the STA group (p=0.804). These eight patients received a temporary diverting ileostomy. One patient (1.3%) in the CAR group was diagnosed with anastomotic stricture through an electronic colonoscopy after 3 months postoperatively. The incidence of postoperative intestinal obstruction was comparable between the two groups (p=0.192). With a median follow-up duration of 39.6 months, the 3-year overall survival rate was 83.1% in the CAR group and 89.0% in the STA group (p=0.152).CONCLUSIONS:NiTi CAR 27 is safe and effective for colorectal end-to-end anastomosis. Its use is equivalent to that of the conventional circular staplers. This study suggests that NiTi CAR 27 may be a beneficial alternative in colorectal anastomosis in Chinese colorectal cancer patients.

609 Background: Though total mesorectal excision (TME) has proved to effectively decrease local recurrence rate of mid/low rectal cancer, the efficacy of preoperative radiotherapy in Asian patients remains unclear. The present study aimed to compare the efficacy of TME alone versus TME after preoperative radiotherapy and simultaneous chemotherapy with capecitabine plus oxaliplatin in Chinese patients with stage II and III mid/low rectal adenocarcinoma. Methods: Patients (n=192) aged between 18 and 70 years enrolled from March 23, 2008 to August 2, 2012 were randomly divided into two groups. Group A (n=97) received preoperative radiotherapy and simultaneous chemotherapy [46-50 GY/23-25 with oxaliplatin 100 mg/m2 (D1) and capecitabine 1,000 mg/m2 (bid, D1-15), repeated since D22], which was followed by TME; while patients in group B (n=95) underwent TME alone. While disease free survival (DFS) was the primary endpoint; the following were evaluated as secondary endpoints: pathological response rate, pathologic complete response (PCR) rate, anal preservation rate, local recurrence rate, distant metastasis rate, acute toxic effects, and late toxic effects. Results: Excluding the drop outs, 90 and 94 patients were analyzed in group A and B, respectively. The median follow-up time was 29 (range: 0 to 59) months. PCR was achieved for 32 patients (35.6%). The median survival time and overall survival (OS) rate in group A were 24 months and 92.5% (95% CI: 88.3-96.7), respectively; while the same were 34 months and 88.7% (95% CI: 84.8-92.6) in group B. The median DFS time was 22 and 31 months in group A and B, respectively; and the overall DFS was 86.1% (95% CI: 81.6-90.6%) and 80.6% (95% CI: 74.8-85.4%) in both groups. No significant differences were observed between groups in OS rate (p=0.323), overall DFS, (p=0.612), and anal preservation rate (p=0.849). Conclusions: Preoperative radiotherapy combined with chemotherapy of capecitabine plus oxaliplatin could result in higher PCR rate. However, studies with long follow up and large sample are recommended to demonstrate the efficacy of this treatment strategy over TME alone. Clinical trial information: ChiCTR-TRC-00000122.

213 Background: Identifying molecular residual disease (MRD) with tailored tumor-informed ctDNA-based next-generation sequencing (NGS) assays after curative surgery could facilitate the individualized management of resected colorectal cancer (CRC) patients. Here, we prospectively evaluated the clinical performance of tumor-informed ctDNA mutation analysis using a novel Burning Rock Patient-specific Prognostic and Potential Therapeutic Marker Tracking (brPROPHET) approach for assessing MRD in resected CRC patients. Methods: The brPROPHET assay was designed to track patient-specific somatic variants based on whole-exome sequencing (WES) of the tumor tissue and matched white blood cells (WBCs). Fixed panel with informed calling (FI) and fixed panel with agnostic calling (FA) assays were performed in a subset of patients with a 168-gene panel spanning 273 kb of the human genome for a head-to-head comparison. Results: A total of 117 patients (stage II/III 53[45.0%]/41[35.0%]) were analyzed. 60 (51.0%) patients were treated with adjuvant therapy after surgery. brPROPHET assay was designed to target up to 55 variants per patient. Only 6% (344/5835) of designed variants were included in the fixed panels. 75% (2908/3886) of genes selected for panel design were private to a specific patient. Preoperative ctDNA was detected in 97% (113/117) of the patients with 88% (14/16), 98% (52/53), 98% (40/41), and 100% (7/7) in stage I, II, III and IV, respectively. The median ctDNA levels were observed to be higher in patients with advanced stages and significantly correlated with tumor volume. MRD status was tested postoperatively on day 7 and day 30 with a positivity rate of 18% (21/117) and 15% (14/93), respectively. Due to a short follow-up period, only two patients had recurred, and ctDNA was detected prior to radiological relapse, with a lead time of 1 and 2 months, respectively. Among 74 patients enrolled for parallel comparing three MRD assays, preoperative ctDNA was detected in 97.3%, 75.7%, and 68.9% of patients with brPROPHET, FI and FA fixed panel assays, respectively. 20.3% (15/74) of patients had baseline ctDNA captured by brPROPHET assay only. The ctDNA levels of these patients (median:0.3 mean tumor molecules [MTM] / milliliter [mL]) were lower than those captured by FI/FA fixed panels (median:3.0 MTM/mL, p<0.05). A total of 135 postoperative blood samples were tested by all three assays, the positive rates with brPROPHET, FI and FA fixed panel assays were 14.8%, 8.1%, and 6.7% respectively. Conclusions: This initial study reported the clinical performance of the patient-specific brPROPHET assay in CRC, demonstrating superior sensitivity in detecting preoperative and postoperative ctDNA than the fixed panel assays. The ongoing study including correlation with clinical outcomes and serial testing will be presented.

Background: Whether primary tumor location of colorectal cancer (CRC) affects survival of patients after resection of liver metastases remains controversial. This study was conducted to investigate the differences in clinicopathological characteristics and prognosis between right-sided CRC and left-sided CRC patients with liver metastases after hepatectomy. Methods: From 2002 to 2018, 611 patients with colorectal liver metastases (CRLM) who underwent hepatectomy at our center were reviewed. Primary tumors located from cecum to transverse colon were defined as right-sided group (n = 141); tumors located from splenic flexure to rectum were defined as left-sided group (n = 470). Patients were compared between two groups before and after a 1:1 propensity score matching (PSM) analysis. Results: Before PSM, median survival time and 5-year overall survival (OS) rate in right-sided group were 77 months and 56.3%, and those in left-sided group were 64 months and 51.1%, respectively. After PSM, median survival time and 5-year OS rate in right-sided group were 77 months and 55.9%, and those in left-sided group were 58.8 months and 47.3%, respectively. The OS rates did not differ between two groups before and after PSM (P = 0.575; P = 0.453). However, significant different recurrence-free survival (RFS) rate was found before and after PSM between right-sided and left-sided group (P = 0.028, P = 0.003). Conclusions: Compared to patients with left-sided primary tumors, patients with right-sided primary tumors had a worse RFS but similar OS. Careful preoperative evaluation, intensive preoperative chemotherapy and frequent follow-up to detect early recurrence might be justified for CRLM patients with right-sided primary tumors.

Background Whether primary tumor location of colorectal cancer (CRC) affects survival of patients after resection of liver metastases remains controversial. This study was conducted to investigate the differences in clinicopathological characteristics and prognosis between right-sided CRC and left-sided CRC patients with liver metastases after hepatectomy. Methods From 2002 to 2018, 611 patients with colorectal liver metastases (CRLM) who underwent hepatectomy at our center were reviewed. Primary tumors located from cecum to transverse colon were defined as right-sided group (n = 141); tumors located from splenic flexure to rectum were defined as left-sided group (n = 470). Patients were compared between two groups before and after a 1:1 propensity score analysis (PSM). Results Before PSM, median survival time and 5-year overall survival (OS) rate in right-sided group were 77 months and 56.3%, and those in left-sided group were 64 months and 51.1%, respectively. After PSM, median survival time and 5-year OS rate in right-sided group were 77 months and 55.9%, and those in left-sided group were 58.8 months and 47.3%, respectively. The OS rates did not differ between two groups before and after PSM ( P = 0.575; P = 0.453). However, significant different recurrence free survival (RFS) rate was found before and after PSM between right-sided and left-sided group ( P = 0.028, P = 0.003). Conclusions Primary tumor location of CRC impacts RFS for patients with liver metastases after resection. A more frequent follow up to detect early recurrence might be justified for CRLM patients with a right-sided CRC.

Multimodal characterization of cell-free DNA (cfDNA) in blood can enable the sensitive and non-invasive detection of human cancers but remains technically challenging and costly. Here, we developed Multimodal Epigenetic Sequencing Analysis (MESA), a flexible and sensitive method of capturing and integrating multimodal epigenetic information of cfDNA using a single experimental assay, i.e., non-disruptive bisulfite-free methylation sequencing, such as Enzymatic Methyl-seq (EM-seq) and TET-assisted pyridine borane sequencing (TAPS). MESA can simultaneously infer four epigenetic modalities, namely cfDNA methylation, nucleosome occupancy, nucleosome fuzziness, and fragmentation profile for regions surrounding gene promoters and polyadenylation sites (PASs). When applied to 462 cfDNA samples from 2 independent clinical cohorts for colon cancer, new modalities (e.g., nucleosome fuzziness) and genomic features (e.g., PASs) introduced in MESA are highly complementary or superior to conventional ones, such as promoter DNA methylation, for cancer detection. Furthermore, MESA’s integrated analysis of multimodal epigenetic features significantly improved the detection accuracy for colon, liver, and pancreatic cancers compared to single modality models. Together, MESA captures additional and highly complementary epigenetic information from cfDNA without additional experimental assays, highlighting the importance and clinical potential of using multimodal epigenetic features for non-invasive cancer detection.