Microsatellite instability in rectal cancer: what does it mean? A study of two randomized trials and a systematic review of the literature.

AIM: Currently, compelling evidence illustrates the significance of determining microsatellite instability (MSI) in colorectal cancer (CRC). The association of MSI with proximal CRC is well established, however, its implications in patients with rectal cancer remain undefined. We therefore aimed to determine the role of MSI with respect to incidence and outcome in patients with rectal cancer. METHODS AND RESULTS: For this we examined patients from two prospective phase III trials: TME trial and PROCTOR-SCRIPT trial (n = 1250). In addition, we performed a literature review to evaluate the overall prevalence, the effect on survival and the response to neo-adjuvant treatment in patients with MSI rectal cancer compared with microsatellite stable (MSS) rectal cancer. Our TME and PROCTOR-SCRIPT cohort showed no differences in terms of overall survival (OS) (hazard ratio [HR] 1.00, 95% confidence interval [CI] 0.69-1.47) and disease-free survival (DFS) (HR 1.00, 95% CI 0.68-1.45) in patients with MSI compared to MSS rectal cancer. The total number of MSI cases in all included studies (including our own) was 1220 (out of 16,526 rectal cancer patients), with an overall prevalence of 6.7% (standard error 1.19%). Both for OS as for DFS there was no impact of MSI status on prognosis (HR 1.00, 95% CI 0.77-1.29 and HR 0.86, 95% CI 0.60-1.22, respectively). The risk ratio (RR) for downstaging and pathological complete response showed also no impact of MSI status (RR 1.15, 95% CI 0.86-1.55 and RR 0.81, 95% CI 0.54-1.22, respectively). CONCLUSION: Rectal cancer patients with MSI form a distinct and rare subcategory, however, there is no prognostic effect of MSI in rectal cancer patients.

Bite-on-bite biopsies for the detection of residual esophageal cancer after neoadjuvant chemoradiotherapy.

BACKGROUND: Active surveillance after neoadjuvant treatment is increasingly implemented. The success of this strategy relies on the accurate detection of residual cancer. This study aimed to assess the diagnostic value of a second (bite-on-bite) biopsy for the detection of residual esophageal cancer and to correlate outcomes to the distribution of residual cancer found in the resection specimen. METHODS: A multicenter prospective study of esophageal cancer patients undergoing active surveillance after neoadjuvant chemoradiotherapy was performed. At clinical response evaluations, an upper gastrointestinal (GI) endoscopy was performed with at least four bite-on-bite biopsies of the primary tumor site. First and second biopsies were analyzed separately. Patients with histopathological evidence of residual cancer were included in the primary analysis. Two pathologists blinded for biopsy outcome examined all resection specimens. RESULTS: Between October 2017 and July 2020, 626 upper GI endoscopies were performed in 367 patients. Of 138 patients with residual cancer, 112 patients (81 %) had at least one positive biopsy. In 14 patients (10 %) only the first biopsy was positive and in 25 patients (18 %) only the second biopsy (P = 0.11). Remarkably, the rates of patients with tumor-free mucosa and deeper located tumors were higher in patients detected by the first biopsy. The second biopsy increased the false-positive rate by 3 percentage points. No adverse events occurred. CONCLUSIONS: A second (bite-on-bite) biopsy improves the detection of residual esophageal cancer by almost 20 percentage points, at the expense of increasing the false-positive rate by 3 percentage points. The higher detection rate is explained by the higher number of biopsies obtained rather than by the penetration depth.

Sex Differences in Neoplastic Progression in Barrett's Esophagus: A Multicenter Prospective Cohort Study.

Recommendations in Barrett's esophagus (BE) guidelines are mainly based on male patients. We aimed to evaluate sex differences in BE patients in (1) probability of and (2) time to neoplastic progression, and (3) differences in the stage distribution of neoplasia. We conducted a multicenter prospective cohort study including 868 BE patients. Cox regression modeling and accelerated failure time modeling were used to estimate the sex differences. Neoplastic progression was defined as high-grade dysplasia (HGD) and/or esophageal adenocarcinoma (EAC). Among the 639 (74%) males and 229 females that were included (median follow-up 7.1 years), 61 (7.0%) developed HGD/EAC. Neoplastic progression risk was estimated to be twice as high among males (HR 2.26, 95% CI 1.11-4.62) than females. The risk of HGD was found to be higher in males (HR 3.76, 95% CI 1.33-10.6). Time to HGD/EAC (AR 0.52, 95% CI 0.29-0.95) and HGD (AR 0.40, 95% CI 0.19-0.86) was shorter in males. Females had proportionally more EAC than HGD and tended to have higher stages of neoplasia at diagnosis. In conclusion, both the risk of and time to neoplastic progression were higher in males. However, females were proportionally more often diagnosed with (advanced) EAC. We should strive for improved neoplastic risk stratification per individual BE patient, incorporating sex disparities into new prediction models.