Meta-analysis of oncological outcomes of sigmoid cancers: A hidden epidemic of R1 “palliative” resections

Genetic analysis for diagnosing local recurrence of sigmoid colon cancer mimicking a small intestinal tumor: a case report

BACKGROUND

With recent advances in genetics research, genetic analysis is increasingly being used in clinical practice. We report a case in which genetic analysis aided in diagnosing a local recurrence of sigmoid colon cancer, initially suspected to be a primary neoplasm of the small intestine.

CASE PRESENTATION

A 61-year-old male underwent laparoscopic sigmoidectomy for stage IIIB sigmoid colon cancer, followed by 8 cycles of CAPOX adjuvant chemotherapy, one and a half years prior. A follow-up CT scan performed one and a half years postoperatively revealed a mass in the small intestine near the ileal end, adjacent to the staple line of the previous colonic anastomosis. PET imaging showed high uptake in the small intestine but no significant uptake at the site of the prior anastomotic ring. Based on these findings, a primary small intestine neoplasm was suspected, rather than a local recurrence of the sigmoid cancer, prompting laparoscopic surgery. Intraoperative findings revealed an inflamed mass in the ileum, approximately 30 cm proximal to the cecum, involving staples from the previous anastomotic site. Consequently, an ileocecal resection combined with resection of the prior colonic anastomosis was performed. Macroscopically, the resected specimen revealed a 25-mm Type 2 tumor in the ileum extending into the previous anastomotic site of the large intestine, while the colonic mucosa remained intact. Histopathological examination identified a moderately differentiated tubular adenocarcinoma, consistent with the histology of the primary sigmoid cancer, raising the possibility of local recurrence. To analyze the origin of the ileal tumor, we performed whole-genome sequencing and subsequent PCR direct sequencing. As a result, identical mutations in two key driver genes (KRAS c.35G > A and PIK3CA c.1624G > A), as well as a mutation in a passenger gene (BBS9 c.2218_2222del), were identified in the primary and ileal tumors. These findings confirmed that the ileal tumor was a local recurrence rather than a new primary malignancy.

CONCLUSIONS

The present case highlights the practical application of genetic analysis in clinical practice, particularly when clinical diagnosis and histopathological findings are inconclusive or conflicting.

Local recurrence in sigmoid cancer is a hidden problem, could CT prognostic factors be of value in their prevention? A multi-centre study of 414 patients

INTRODUCTION

The incidence and patterns of local recurrence of colon cancer are not well reported. The aim of this study was to investigate the contemporary rates and patterns of local recurrence after sigmoid cancer resection, comparing pre and post-operative biomarkers in predicting local disease recurrence.

MATERIALS AND METHODS

A multi-centre, retrospective analysis of 414 patients undergoing resectional surgery for sigmoid colon cancer was conducted. Multivariable Cox Proportional Hazard models were created to identify variables associated with local disease recurrence. Patterns of recurrence and prognostic significance of pre and post-operative variables were identified.

RESULTS

In 414 patients, the local recurrence rate was 12.6%. The R1/R2 rate was 2.4%. Local recurrence occurred most commonly within the peri-anastomotic region (50%), followed by the peritoneum (33%). On multivariate analysis, local recurrence was predicted by pathological T stage (HR 1.15) and R1 resection (HR 2.95), but also computerised tomography (CT) identified tumour deposits (HR 2.40) and local peritoneal infiltration (2.70).

CONCLUSIONS

Contemporary local recurrence rates for sigmoid cancer are high at 12.6%. Outcomes may be improved if local recurrence is reduced at the most common sites such as the peri-anastomotic area or peritoneum. Extra-nodal CT-imaging biomarkers of local peritoneal infiltration and tumour deposits were prognostically significant on multivariate analysis in addition to pathology staging variables.

Ex vivo specimen MRI and pathology confirm a rectosigmoid mesenteric waist at the junction of the mesorectum and mesocolon

AIM

Continuity of the mesentery has recently been established and may provide an anatomical basis for optimal colorectal resectional surgery. Preliminary data from operative specimen measurements suggest there is a tapering in the mesentery of the distal sigmoid. A mesenteric waist in this area may be a risk factor for local recurrence of colorectal cancer. This study aimed to investigate the anatomical characteristics of the mesentery at the colorectal junction.

METHOD

In this cross-sectional study, 20 patients were recruited. After planned colorectal resection, the surgical specimens were scanned in a MRI system and subsequently dissected and photographed as per national pathology guidelines. Mesenteric surface area and linear measurements were compared between MRI and pathology to establish the presence and location of a mesenteric waist.

RESULTS

Specimen analysis confirmed that a narrowing in the mesenteric surface area was consistently apparent at the rectosigmoid junction. Above the anterior peritoneal reflection, the surface area and posterior distance of the mesentery of the upper rectum initially decreased before increasing as the mesentery of the sigmoid colon. These anatomical properties created the appearance of a mesenteric 'waist' at the rectosigmoid junction. Using the anterior reflection as a reference landmark, the rectosigmoid waist occurred at a mean height of 23.6 and 21.7 mm on MRI and pathology, respectively.

CONCLUSION

A rectosigmoid waist occurs at the junction of the mesorectum and mesocolon, and is a mesenteric landmark for the rectum that is present on both radiology and pathology.