Short- and long-term outcomes of transanal decompression tube and self-expandable metallic stent for obstructive colorectal cancer based on a multicenter database (KYCC2110).

AIM: There are well-known methods for decompressing the colorectal tract before surgery, including transanal decompression tubes (TDT) and self-expanding metallic stents (SEMS). This study aimed to compare the short and long-term results in patients with malignant large bowel obstruction in whom TDT or SEMS were placed before surgery. METHODS: This retrospective observational study enrolled 225 patients with malignant large bowel obstruction in whom TDT or SEMS were placed preoperatively and underwent R0 resection between 2008 and 2020. One-to-two propensity score matching was performed according to patient characteristics. Short- and long-term outcomes were compared. The primary endpoint was relapse-free survival (RFS). The secondary endpoints were the overall survival (OS) and postoperative complication rate. RESULTS: Fifty-seven patients in the TDT group and 114 in the SEMS group were matched. The 3-year RFS rates were 66.7% in the TDT group and 69.9% in the SEMS group (p = 0.54), and the 3-year OS rates were 90.5% in the TDT group and 87.1% in the SEMS group (p = 0.52). No significant differences in the long-term results were observed between the two groups. Regarding short-term results, the SEMS group had significantly fewer stoma construction (p = 0.007) and shorter postoperative hospitalization (p < 0.001). The incidence of postoperative complications (grade ≥ 2) was significantly lower in the SEMS group (p = 0.04). CONCLUSION: No significant differences in the long-term results were observed between the TDT and SEMS group. The SEMS showed significant usefulness in terms of improving short-term outcomes.

Chemotherapy-induced Reversion of Mutant RAS to Wild-type RAS in Metastatic Colorectal Cancer.

BACKGROUND/AIM: Secondary mutation of mutated RAS, induced by chemotherapy, is thought to be rare. However, introduction of liquid biopsy (LB) has made it possible to monitor RAS status in patients' plasma throughout the course of chemotherapy for metastatic colorectal cancer (mCRC), and disappearance of the RAS mutation (RAS-mt), i.e., the NeoRAS-wt phenomenon, has been reported and is receiving attention, especially with respect to treatment implications. PATIENTS AND METHODS: A prospective study of 129 patients undergoing chemotherapy for mCRC (RAS-wt, n=65; RAS-mt, n=64) was carried out. Plasma RAS status was monitored in these patients by LB. Relations between secondary genetic change, chemotherapy, and 6-month disease outcomes were analyzed. The effect of anti-EGFR mAb therapy on NeoRAS-wt mCRC was also examined. RESULTS: NeoRAS-wt was detected in 27 (43.5%) RAS-mt patients overall and in all patients with a G12S or Q61H mutation. First-line treatment was more effective among NeoRAS-wt patients than non-NeoRAS-wt patients (70.9% vs. 48.6% overall response rate, p=0.087), and the time from treatment to LB was shorter in this group. Six-month outcomes were significantly better in the NeoRAS-wt group (p<0.001), and conversion to NeoRAS-wt was found to be predictive of a good outcome (OR=7.886, 95% CI=2.458-25.30; p<0.001). Anti-EGFR mAb therapy was found to restrict disease progression in NeoRAS-wt patients. CONCLUSION: Conversion to NeoRAS-wt is relatively frequent, and it may predict good responses to treatment. Anti-EGFR mAb therapy was effective for our NeoRAS-wt patients. Detection of NeoRAS-wt by LB may significantly change the indication for anti-EGFR mAb therapy and the mCRC treatment strategy.

Prediction of lateral lymph node metastasis using OSNA method for mesorectal lymph nodes in low rectal cancer: A prospective study by the Kanagawa Yokohama Colorectal Cancer Study Group (KYCC1801).

BACKGROUND AND OBJECTIVES: Contrary to the Japanese guidelines recommendations regarding lateral lymph node dissection (LatLND) for rectal cancer, its omission is common in clinical practice without reliable omission criteria. Negative pathological mesorectal lymph node metastasis (MesLNM) is reportedly highly correlated with negative pathological lateral lymph node metastasis (p-LatLNM); however, this cannot be used as a criterion because pathological features are revealed postoperatively. Herein, we prospectively evaluated the negative predictive value (NPV) of MesLNM diagnosed via the one-step nucleic acid amplification (OSNA) method for p-LatLNM. METHODS: This prospective study was conducted at a single academic study group in Japan. The key eligibility criterion was mid-to-low rectal cancer planned to be treated using mesorectal excision with LatLND. According to the study protocol, the OSNA method was considered useful if the point estimate of the NPV exceeded 95%. RESULTS: Preoperative case registration was conducted between 2018 and 2020; 34 patients were registered. Among these, 16 were negative for OSNA-MesLNM, and negative p-LatLNM was confirmed in all cases. The point estimate of the NPV was 100%, with the 95% confidence interval ranging from 79.4% to 100.0%. CONCLUSIONS: The OSNA method is useful in selecting patients in whom LatLND can be omitted in real-world clinical practice.

Prospective analysis of tumor spread to the small bowel mesentery in cases of right-sided colon cancer.

PURPOSE: Guidelines advocate minimal ileal resection when right hemicolectomy is performed for right-sided colon cancer. The practice, thought to prevent malabsorption syndrome, does not appear to foster local recurrence. Little evidence based on rigorous study exists, however. To understand the pattern of lymphatic spread of right-sided colon cancer toward the small bowel and thus determine the appropriate margin size, we prospectively investigated anatomical distribution of lymph nodes (LNs) in the small bowel mesentery and of metastasis to these nodes in patients with right-sided colon cancer treated by such surgery. METHODS: In each case, the mesenteric specimen, which had been dissected along the ileocolic vessels and included intermediate LNs, was divided into 2 areas: that 0-3 cm from the vessel pedicle (area 1) and that 3-5 cm from the pedicle (area 2). The peri-intestinal mesentery was cut into 9 segments. RESULTS: Ninety-one patients were included in the study. Overall, 3366 LNs were dissected. Four hundred fifty-three of these LNs were located in area 1 (90 cases), and 15 (3.3%) were metastatic. Only 63 LNs were located in area 2 (34 cases; average of 0.69 per patient); none was metastatic. Overall, 269 LNs were found in the small bowel mesentery (in 56 of the 91 patients). Only 4 were positive (3 cases), and all were within 5 cm of the ileocecal valve. CONCLUSION: Our data indicate that a surgical margin 3 cm from the ileocecal pedicle and a short (5 cm) ileal margin are oncologically reasonable for effective right hemicolectomy.