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Clinical significance of the pT4 category in colon cancer is increasing with several therapeutic implications. The aim of this study was to evaluate variability in diagnosing pT4a colon cancer. Twelve pathologists classified 66 preselected scanned Hematoxylin/Eosin-stained slides with tumor cells at a distance of 25-1500 μm (n = 22), 0-25 μm (n = 22), or on (n = 22) the peritoneal surface. Inter- and intraobserver variability were calculated using Kappa statistics. For interlaboratory variability, pathology reports of pT3 and pT4a colon cancer were extracted from the Dutch Pathology Registry between 2012 and 2015. The proportion of pT4a (pT4a/(pT3+pT4a)) was compared between 33 laboratories. Potential risk of understaging was assessed by determining the average number of blocks taken from pT3 and pT4a N0-2M0 tumors with metachronous peritoneal metastasis. Interobserver variability among 12 pathologists was 0.50 (95%CI 0.41-0.60; moderate agreement). Intraobserver variability (8 pathologists) was 0.71 (substantial agreement). A total of 7745 reports with pT3 or pT4aN0-2M0 colon cancer from 33 laboratories were included for interlaboratory analysis. Median percentage of pT4a was 15.5% (range 3.2-24.6%). After adjustment for case mix, 8 labs diagnosed pT4a significantly less or more frequently than the median lab. Metachronous peritoneal metastases were histologically verified in 170 of 6629 pT3 and in 129 of 1116 pT4a tumors, with a mean number of blocks of 4.03(SD 1.51) and 4.78 (SD 1.76) taken from the primary tumors, respectively (p < 0.001). A substantial variability in diagnosing pT4a colon cancer exists, both at pathologist and laboratory level. Diagnosis of pT4a stage appears to be challenging and there is a need for standardizing assessment of this pathological entity.

Background: Esophagectomy for submucosal (T1b) esophageal adenocarcinoma (EAC) is performed in order to optimize patient outcomes given the risk of concurrent lymph node metastases (LNM). However, not seldom, comorbidity precludes these patients from surgery. Therefore, the aim of our study was to assess the course of follow-up after treatment in submucosal EAC patients undergoing surgery versus conservative therapy and to evaluate the incidence of metastatic disease., Methods: Between 2001 and 2012, all patients undergoing diagnostic endoscopic resection for EAC in two centers were reviewed. Only patients with histopathologically proven submucosal tumor invasion were included. Submucosal EACs were divided into tumors that were removed radically (R0) and irradically (R1). Subsequently, in the R0 group, EACs were classified as either low risk (LR; submucosal invasion <500 nm, G1-G2, no LVI) or high risk (HR; deep submucosal invasion >500 nm, G3-G4 and/or LVI). Metastatic disease was defined as LNM in surgical resection specimen and/or evidence of malignant disease during follow-up (FU)., Results: Sixty-nine patients with a submucosal EAC were included [23 R1-resections and 46 R0-resection (14 R0-LR and 32 R0-HR)]. Twenty-six patients underwent surgical treatment (1 R0-LR, 12 R0-HR and 13 R1). None of the 14 R0-LR patients developed metastatic disease after a median FU of 60 months. In the R0-HR group and R1 group, metastatic disease was diagnosed in 16 and 30 % of patients, respectively. Surgical patients tended to have a better overall survival than non-surgical patients (p = 0.09). Tumor-related deaths, however, were 12 % in both groups., Conclusions: In LR submucosal EAC, the risk of metastatic disease appears to be very low. In deep submucosal EAC (either R0- or R1-resection), the rate of metastatic disease is lower than reported in earlier surgical series. Given the reasonable disease-free survival and high background mortality, conservative management of these patients seems to be a valid alternative for surgery in selected cases.

Objective: This study investigates the predictive value of diffusion-weighted magnetic resonance imaging (DW-MRI) for good pathological response at different time points during and after preoperative chemoradiotherapy (CRT) in locally advanced rectal cancer., Background: Preoperative CRT followed by total mesorectal excision (TME) is the standard of care for locally advanced rectal cancer. The use of standard radical surgery in good treatment responders after CRT is being questioned., Methods: Patients with locally advanced rectal adenocarcinoma were treated with preoperative CRT followed by surgery. DW-MRI scans were performed before CRT, during the third week of CRT, 4 weeks post-CRT and presurgery. Tumor apparent diffusion coefficient (ADC) values were acquired from the DW-MRI scans. After surgery the pathological tumor regression grade was assessed according to the classification by Mandard et al [Cancer. 1994;73:2680-2686]. Patients with pathological complete or near-complete response (tumor regression grade 1-2) were classified as good responders (GRs)., Results: Twenty-two patients participated of which 9 were GRs (41%). Pre-CRT ADC values were lower in good versus moderate/poor responders (P = 0.04). ADC values during CRT and four weeks post-CRT were higher in GR. ADC values presurgery did not differ between response groups. For all time points the relative ADC increase (ΔADC) compared to the ADC pre-CRT was higher in GR (P < 0.001). The ΔADC during CRT and four weeks post-CRT were the best predictive parameters for pathological good response., Conclusions: This study shows that DW-MRI is feasible to select good treatment responders during preoperative CRT for locally advanced rectal cancer.