Purpose The relationship between microsatellite instability (MSI) and tumor response after neoadjuvant chemoradiotherapy (nCRT) in rectal cancer remains unclear. The present study aimed to evaluate the association between MSI and tumor response to nCRT in rectal cancer treatment. Methods Patients with rectal cancer from 2 tertiary hospitals who underwent nCRT, followed by radical surgery, were included. The microsatellite status was determined using a PCR-based Bethesda panel. Tumors with a Dworak’s tumor regression grade of 3 or 4 were considered to have a good response. Predictive factors for a good response to nCRT were analyzed. Results Of the 1,401 patients included, 910 (65.0%) had MSI results and 1.5% (14 of 910) showed MSI-H. Among all the patients, 519 (37.0%) showed a good response to nCRT. A univariate analysis showed that MSI-H tended to be negatively associated with a good response to nCRT, but no statistical significance was observed (7.1% vs. 24.1%, P = 0.208). Multivariate analysis showed that well-differentiated tumors were the only predictive factor for good response to nCRT (odds ratio [OR], 2.241; 95% confidence interval [CI], 1.492–3.364; P < 0.001). MSI status tended to be associated with the response to nCRT (OR, 0.215; 95% CI, 0.027–1.681; P = 0.143). Conclusion MSI-H was not associated with response to nCRT in patients with rectal cancer.

Purpose Some studies have suggested that circumferential tumor location (CTL) of rectal cancer may affect oncological outcomes. However, studies after preoperative chemoradiotherapy (CRT) are rare. This study aimed to evaluate the impact of CTL on oncologic outcomes of patients with mid to low rectal cancer who received preoperative CRT. Methods Patients with mid to low rectal cancer who underwent total mesorectal excision after CRT from January 2013 to December 2018 were included in this retrospective study. The impact of CTL on the pathological circumferential resection margin (CRM) status, local recurrence-free survival (LRFS), disease-free survival (DFS), and overall survival (OS) was analyzed. Results Of the 381 patients, 98, 70, 127, and 86 patients were categorized into the anterior, posterior, lateral, and circumferential tumor groups, respectively. Tumor location was not significantly associated with the pathological CRM involvement (anterior, 12.2% vs. posterior, 14.3% vs. lateral, 11.0% vs. circumferential, 17.4%; P = 0.232). Univariate analyses revealed no correlation between CTL and 3-year LRFS (93.0% vs. 89.1% vs. 91.5% vs. 88%, P = 0.513), 3-year DFS (70.3% vs. 70.2% vs. 75.3% vs. 75.7%, P = 0.832), and 5-year OS (74.7% vs. 78.0% vs. 83.9% vs. 78.2%, P = 0.204). Multivariate analysis identified low rectal cancer and pathological CRM involvement as independent risk factors for all survival outcomes (all P < 0.05). Conclusion CTL of rectal cancer after preoperative CRT was not significantly associated with the pathological CRM status, recurrence, and survival.

BACKGROUND/OBJECTIVES This study aimed to evaluate the effect of preoperative immunonutrition on the composition of fecal microbiota following a colon cancer surgery. MATERIALS/METHODS This study was a secondary analysis of a randomized controlled trial assessing the impact of preoperative immunonutrition on the postoperative outcomes of colon cancer surgery. Patients with primary colon cancer were enrolled and randomly assigned to receive additional preoperative immunonutrition or a normal diet alone. Oral nutritional supplementation (400 mL/day) with arginine and ω-3 fatty acids were administered to patients in the immunonutrition group for 7 days prior to surgery. Thirty-two fecal samples were collected from 16 patients in each group, and the composition of fecal microbiota was compared between the 2 groups. RESULTS At the phylum level, no significant difference was observed in the composition of microbiota between the 2 groups ( Firmicutes , 69.1% vs. 67.5%, P = 0.624; Bacteroidetes , 19.3% vs. 18.1%, P = 0.663; Actinobacteria , 6.7% vs. 10.6%, P = 0.080). The Firmicutes / Bacteroidetes ratio (4.43 ± 2.32 vs. 4.55 ± 2.51, P = 0.897) was also similar between the 2 groups. At the genus level, the proportions of beneficial bacteria such as Faecalibacterium spp. (8.1% vs. 6.4%, P = 0.328) and Prevotella spp. (6.9% vs. 4.8%, P = 0.331) were higher, while that of Clostridium spp. was lower (0.5% vs. 1.2%, P = 0.121) in the immunonutrition group, but the difference was not significant. CONCLUSIONS Immunonutrition showed no significant association with the composition of fecal microbiota. The relationship between immunonutrition and the fecal microbiota should be investigated further in large-scale studies.

Background: Very few studies have been conducted on the treatment strategy for enlarged para-aortic lymph nodes (PALNs) incidentally detected during surgery. The purpose of this study was to investigate the benefit of lymph node dissection in patients with incidentally detected enlarged PALNs.Methods: We retrospectively reviewed left colon and rectal cancer patients who underwent surgical resection with PALN dissection between January 2010 and December 2018. The predictive factors for pathologic PALN metastasis (PALNM) were analyzed, and survival analyses were conducted to identify prognostic factors.Results: Among 263 patients included, 19 (7.2%) patients showed pathologic PALNM, and 5 (26.33%) of them had enlarged PALNs incidentally detected during surgery. These 5 patients accounted for 2.2% of 227 patients who had no evidence of PALNM in preoperative radiologic examination. Radiologic PALNM (odds ratio [OR] 12.737, 95% confidence interval [CI] 3.472–46.723) and radiologic distant metastasis other than PALNM (OR = 4.090, 95% CI 1.011–16.539) were independent predictive factors for pathologic PALNM. Pathologic T4 stage (hazard ratio [HR] 2.196, 95% CI 1.063–4.538) and R2 resection (HR 4.643, 95% CI 2.046–10.534) were independent prognostic factors for overall survival (OS). In patients undergoing R0 resection, pathologic PALNM was not associated with the 5-year OS (90% vs. 82.2%, p = 0.896). Conclusions: Dissection of enlarged PALNs incidentally detected during colorectal surgery may benefit patients, with favorable survival outcomes.