Objective: The aim of this study was to evaluate the utility of cell-free DNA (cfDNA) as a biomarker in the treatment of BRAF V600E mutation-positive colorectal cancer.

Methods: Ten stage IV patients (Cohort 1) and 21 stage II/III patients who underwent radical resection (Cohort 2) with BRAF V600E mutation-positive colorectal cancer were included. We extracted cfDNA from peripheral blood and assessed BRAF V600E mutation using Droplet Digital PCR.

Results: [Cohort 1] Although there was no significant difference in survival between patients whose cfDNA BRAF became negative during treatment and the others (P＝0.524), the survival curves of patients whose cfDNA BRAF became negative tended to be better than those of the others. Regarding the decision for conversion surgery and progression of metastases, cfDNA BRAF was more in line with disease status than tumor markers. [Cohort 2] Postoperative cfDNA BRAF-negative patients were recurrence-free. The postoperative cfDNA BRAF-positive patients had an earlier recurrence and earlier disease progression.

Conclusion: In BRAF V600E mutation-positive colorectal cancer, cfDNA BRAF may be useful in determining the response to treatment of unresectable advanced disease and in determining minimal residual disease in curatively resected patients.

Objective: To evaluate the safety of robot-assisted rectal cancer surgery with lateral lymph node dissection in elderly patients.

Methods: We compared short-term outcomes for elderly patients (≥75 years old) and younger patients (＜74 years old) undergoing this operation.

Results: Seven elderly patients and 32 younger patients were included in the study. There were no differences in background factors without age, comorbidity and previous disease between the two groups. Surgical outcomes also did not differ between the two groups. There were no cases of conversion laparotomy in either group. Postoperative complication rates were 42.9% and 46.9% in the older group and younger group respectively (including duplicate cases). Postoperative mortality was not observed in either group.

Conclusions: Rectal cancer surgery with lateral lymph node dissection using the da Vinci system in elderly patients did not tend to cause more postoperative complications than in younger cases. Although the number of cases was small, the results of this study demonstrated the general safety and feasibility of the operation for elderly patients.

Purpose: To evaluate the applicability of definitive surgery for anal fistula in Crohn's disease (CD).

Methods: We studied 81 CD fistula cases (42 “CD-operated cases”, 39 “CD-non-operated cases”) and 119 “non-CD-operated cases”. Indications for definitive surgery were as follows: controlled intestinal lesions, primary opening of the fistula situated caudal to the puborectalis muscle, and lesions that were relatively localized and formed fistula tracts. Definitive surgery was performed by fistulotomy between the internal opening and the primary lesion, and resection or seton procedure for the ducts distant from the primary lesion.

Results: Although the average healing time (130.6±75.0 days) was about twice that of non-CD-operated cases (64.9±35.4 days) due to excessive granulation and prolonged epithelialization, 41 of 42 CD-operated cases (97.6%) were cured without incontinence. There was no difference in the number of fistulas, detection rates of non-caseating epithelioid granulomas, or average healing time between secondary and incidental lesion cases. These results suggest that they should be treated as similar conditions. Healing tended to be earlier in cases where biologics were used.

Conclusion: We believe that definitive surgery may be indicated for anal fistulas in CD, provided indications for surgery are strictly applied and appropriate surgery can be performed.

Purpose: To verify the outcome of diltiazem ointment in patients with chronic anal fissure.

Methods: Between January 2014 and February 2022, a total of 203 patients with chronic anal fissure were treated with diltiazem ointment. The safety and efficacy of topical diltiazem were evaluated retrospectively in these patients. Patients were advised to apply 2% diltiazem ointment twice a day. The efficacy of topical diltiazem was judged when epithelization or scarring of the fissure was confirmed on inspection or anoscope.

Results: The efficacy rate of topical diltiazem in the treatment of chronic fissure was 71% (118/167). As for adverse effects of topical diltiazem, anal itching was reported in 18% (33/182) and headache in under 1% (1/182). Recurrence of anal fissure was found in 21 of 118 patients (18%).

Conclusion: Topical diltiazem in the treatment of chronic fissure was confirmed to be effective for Japanese patients.

Aim: The aim of this study was to investigate risk factors for lymph node metastasis (LNM) in pathological T1 colorectal cancer (CRC).

Patients and Methods: Among the 1245 patients who underwent colorectal surgical resection at our institute between January 2014 and December 2020, 186 patients who were diagnosed with pathological T1 CRC were retrospectively reviewed in this study.

Results: The overall incidence rate of LNM was 13.9% (26/186). Multivariate analyses identified lymphatic invasion as being a significant risk factor for LNM (HR 12.5 [95% CI, 4.76-32.8], p＜0.0001). The incidence rate of LNM in SM invasion＞1000μm without any other risk factors was 5.9% (6/101).

Conclusions: Lymphatic invasion was the only risk factor for LNM in pT1 CRC. These results could be useful for making an appropriate clinical decision for additional surgical resection in patients with pT1 CRC.

Functional end to end anastomosis (FEEA) is frequently used in colon cancer resection. There is a greater possibility of higher recurrence rate in an anastomosis site developed by implantation of exfoliated cancer cells due to its wide anastomotic hole. To prevent such recurrence, we performed lavage of the remnant intestinal lumen just before implementation of FEEA. We collected the washout fluid at the end of lavage and performed cytological examination of the fluid. Then we examined the clinicopathological features of cytology-positive cases, and compared the recurrence rate in lavage cases with former cases without lavage. The detection rate of exfoliated cancer cells was 20.3%. The existence of exfoliated cancer cells tended to be associated with smaller tumor size, shorter circumference and shorter longitudinal surgical margin. Rate of recurrence occurring in the anastomotic site was 2.7% in the lavage group and 2.2% in the control group. From the present study, we clarified the existence of exfoliated cancer cells, but could not show the effectiveness of lavage to prevent anastomotic recurrence. Further investigations should be performed to determine the effects of these procedures.

The case was an 89-year-old female. She had abdominal pain and lower abdominal abnormalities that appeared after defecation. Her small intestine had protruded through the anus. The patient was diagnosed with small intestinal prolapse associated with rectal perforation and underwent emergency surgery. She had a history of rectal prolapse and the colon had adhered to the pelvic floor. We managed to identify the rectal perforation site and performed rectal prolapse closure and colostomy. After discharge, she underwent colostomy closure due to inconvenience in colostomy management. There was no recurrence thereafter. Reported cases of rectal perforation with small bowel prolapse are extremely rare. Most cases are of elderly people with a history of surgery for rectal prolapse and uterine prolapse triggered by an increase in intra-abdominal pressure such as defecation. Emergency surgery is performed relatively early because of specific morphological abnormalities and the prognosis is relatively good, but it may be difficult to select the optimal surgical method. We report a rare case of rectal perforation accompanied by prolapse of the small intestine through the anus in which we obtained a good result on surgical treatment while considering such factors as age, PS, patient background, and surgical safety.

Neuroendocrine carcinoma (NEC) of the colon is a rare disease with few reports. Although the tumor progresses rapidly and is highly aggressive and malignant, no effective treatment has been established. In this study, we report four cases of NEC between 2010 and 2020：one male and three females aged 61 to 87 years old. The tumor location was one in the cecum, one in the ascending colon, one in the descending colon, and one in the rectum. Two cases that could not be clearly diagnosed underwent surgery. All cases had lymph node metastases. Three cases died of NEC within 3 to 6 months. Patients with colorectal NEC are often diagnosed at an advanced stage. Multidisciplinary strategies, including systemic chemotherapy, are common in the treatment of colorectal NEC. However, no effective treatment has been established. Further cases need to be accumulated to clarify the best treatment options for colorectal NEC.