Clinical factors affecting the distal margin in rectal cancer surgery

Comparison of apparent diffusion coefficients of resectable mid‑high rectal adenocarcinoma and distal paracancerous tissue

Paracancerous tissues actively communicate with the tumor and undergo molecular alterations associated with tumorigenesis. Apparent diffusion coefficient (ADC) can help distinguish between rectal adenocarcinoma (RA), tumor-adjacent and tumor-distant tissues. Preoperative determining optimal distal resection margin (DRM) is crucial for formulating surgical options. The present study aimed to assess ADC differences between RA and 1 cm-layer distal paracancerous tissues, providing a potential reference basis for preoperatively determining optimal DRM. A total of 110 consecutive patients with mid-high RA undergoing preoperative diffusion-weighted imaging were included. ADCs of RA and distal paracancerous tissues located ~1, 2 and 3 cm from the tumor margin (defined as D1, D2 and D3, respectively) were measured using five b-value pairs (0 and 50; 0 and 100; 0 and 800; 0 and 1,000; and 0 and 1,500 sec/mm2). Differences in ADCs between RA, D1, D2 and D3 were compared using the Friedman test with a post hoc Bonferroni correction. Variables that demonstrated statistical differences in multiple pairwise comparisons underwent receiver operating characteristic (ROC) analysis to assess diagnostic performance of ADCs in distinguishing between tissues. ADC at all b-value pairs demonstrated satisfactory performance in distinguishing RA from D1, D2 and D3 [areas under the ROC curves (AUCs), 0.838 to 0.996)]. When the maximum b-value was ≥800 sec/mm2, the ADC of D1 was significantly lower compared with those of D2 and D3 (P<0.001). ADC exhibited an optimal performance in differentiating D1 from D2 at b-values of 0 and 800 sec/mm2, and D1 from D3 at b-values of 0 and 1,000 sec/mm2 (AUCs: 0.652 and 0.692, respectively). However, ADCs of D2 and D3 demonstrated no differences at all b-value pairs (all P>0.05). In conclusion, ADC may distinguish RA from D1, D2 and D3, and D1 from D2/D3, but cannot distinguish between D2 and D3.

Safety and feasibility of a new rectoscope in rectal cancer surgery. First clinical trial

We present a first in human clinical trial of a new rectoscope that shows, by means of transillumination, the optimal point of transection of the rectum in oncologic surgery. The device was developed together with a team of engineers and was manufactured by 3D printing. Eighteen patients with a mean age of 71 years and a mean distance from the tumor to the anal margin measured by colonoscopy of 10.4 ± 3.9 cm and by MRI of 10 ± 2.4 cm were included in the trial. Transillumination was feasible in all cases, and the use of the rectoscope was safe, as no adverse events due to its use were recorded.

Association of levels of metabolites with the safe margin of rectal cancer surgery: a metabolomics study

Background

Rectal cancer is one of the most lethal of gastrointestinal malignancies. Metabonomics has gradually developed as a convenient, inexpensive and non-destructive technique for the study of cancers.

Methods

A total of 150 tissue samples from 25 rectal cancer patients were analyzed by liquid chromatography–mass spectrometry (LC–MS), and 6 tissue samples were collected from each patient (group 1: tumor; group 2: 0.5 cm from tumor; group 3:1 cm from tumor; group 4:2 cm from tumor; group 5:3 cm from tumor and group 6:5 cm from tumor). The differential metabolites of tumor tissues and 5 cm from the tumor (normal tissues) were first selected. The differential metabolites between tumor tissues and normal tissues were regrouped by hierarchical clustering analysis, and further selected by discriminant analysis according to the regrouping of clustering results. The potential safe margin of clinical T(cT)1,cT2 stage rectal cancer and cT3,cT4 stage rectal cancer at the metabolomic level was further identified by observing the changes in the level of differential metabolites within the samples from group 1 to group 6.

Results

We found 22 specific metabolites to distinguish tumor tissue and normal tissue. The most significant changes in metabolite levels were observed at 0.5 cm (cT1, cT2) and 2.0 cm (cT3, cT4) from the tumor, while the changes in the tissues afterwards showed a stable trend.

Conclusions

There are differential metabolites between tumor tissues and normal tissues in rectal cancer. Based on our limited sample size, the safe distal incision margin for rectal cancer surgery in metabolites may be 0.5 cm in patients with cT1 and cT2 stage rectal cancer and 2.0 cm in patients with cT3 and cT4 stage rectal cancer.

Distal resection margins in rectal cancer specimens: differences in assessment between surgeons and pathologists and the influence of neoadjuvant chemoradiation

To investigate the discrepancy between the distal resection margin (DRM) assessed by surgeons and pathologists, and the impact of neoadjuvant chemoradiotherapy (nCRT) on DRM. This study included 67 rectal cancer patients undergoing elective surgery. DRMs were assessed through four different techniques: in vivo subjective estimative, made by the surgeon before the rectal resection (by palpation and visual estimative); in vivo objective, measured with a ruler before the rectal transection; ex vivo objective, measured right after resection of the specimen; post-fixation objective measurement, conducted by the pathologist. The DRMs subjectively and objectively assessed by the surgeons were not significantly different (3.40 cm vs. 3.45 cm). There was a mean reduction in the length of DRMs of 35.6%, from 3.45 cm objectively measured by the surgeon to 2.20 cm measured by the pathologist. This difference was significant among patients that did not receive nCRT (3.90 cm vs. 2.30 cm, P < 0.001), but not among those who received nCRT (2.30 vs. 2.05 cm). Surgeons are accurate in assessing rectal cancer DRMs. There are significant differences between intraoperative measurements of DRMs and the final pathologic results. However, these differences are not seen when nCRT is used, a finding that may be useful when sphincter preservation is being considered.