KRAS mutant colorectal cancer (CRC) patients develop lung and brain metastases more frequently than KRAS wild-type (WT) counterpart. We retrospectively investigated the prognostic role of KRAS, BRAF, and PIK3CA (exon 20) mutations and loss of phosphatase and tensin homolog (PTEN) in surgically resected lung metastases. Lung specimens from 75 metastatic CRC (mCRC) patients treated with one or more metastasectomies with curative intent were analyzed. Sixty-four percent of patients had KRAS WT lung metastases. PTEN loss-of-function was found in 75%. BRAF and PIK3CA exon 20 mutations were not found. Seven patients subsequently developed brain metastases and 43% of them had KRAS mutation. In univariate analysis, median overall survival (OS) for KRAS WT patients was longer, compared to KRAS mutant patients (median 60.9 vs. 36.6 months, P = 0.035). In addition, both progression-free survival (PFS) and lung disease-free survival (LDFS) between lung surgery and relapse were not associated with KRAS and PTEN status. In multivariate analysis, the risk of death was significantly increased by KRAS mutational status (OS Hazard ratio (HR) 2.17, 95% IC 1.19-3.96, P = 0.012) and lack of adjuvant chemotherapy (OS HR 0.10, 95% IC 0.01-0.74, P = 0.024). The proportion of KRAS mutations in lung metastases was similar to the expected proportion in primary tumors. Patients harboring KRAS mutation had a poorer survival rate compared to WT group both in univariate and multivariate analysis. Moreover, administration of adjuvant chemotherapy after lung metastasectomy (LM) significantly improved both PFS and OS. KRAS mutation is a negative prognostic factor in mCRC patients undergoing LM. Further larger and prospective studies are necessary to confirm these findings.

RAS and BRAF mutations impact treatment and prognosis of metastatic colorectal cancer patients (mCRC), but the knowledge is based on trial patients usually not representative for the general cancer population. Patient characteristics, treatment and efficacy according to KRAS, BRAF and MSI status were analyzed in a prospectively collected unselected population-based cohort of 798 non-resectable mCRC patients. The cohort contained many patients with poor performance status (39% PS 2-4) and elderly (37% age>75), groups usually not included in clinical trials. Patients without available tissue micro array (TMA) (42%) had worse prognostic factors and inferior survival (all patients; 7m vs 11m, chemotherapy-treated;12m vs 17m). The 92 patients (21%) with BRAF mutation had a poor prognosis regardless of microsatellite instability, but receipt of 1-2nd chemotherapy was similar to wildtype BRAF patients. Median survival in this cohort varied from 1 month in BRAF mutated patients not given chemotherapy to 26 months in wildtype KRAS/BRAF patients <75 years in good PS. TMA availability, BRAF mutation and KRAS mutation were all independent prognostic factors for survival. The observed 21% BRAF mutation incidence is higher than the previously and repeatedly reported incidence of 5-12% in mCRC. Screening for BRAF mutations before selection of treatment is relevant for many patients, especially outside clinical trials. A BRAF mutation only partly explained the very poor prognosis of many mCRC patients. Survival in unselected metastatic colorectal cancer patients is extremely variable and subgroups have an extremely short survival compared to trial patients. Patients without available TMA had worse prognostic factors and shorter survival, which questions the total generalizability of present TMA studies and implies that we lack information on the biologically worst mCRC cases. Lack of available tissue is an important underexposed issue which introduces sample bias, and this should be recognized more clearly when conclusions are made from translational mCRC studies.

Evaluation of molecular tumour heterogeneity relies on the tumorous nuclei percentage (TNP) assessment by a pathologist, which has been criticised for being inaccurate and suffering from interobserver variability. Based on the 'Big Bang theory' which states that mutation in colorectal cancer is mostly homogeneous, we investigated this issue by performing a critical analysis of the correlation of the mutant allele fraction with the TNP in 99 colorectal tumour samples with a positive mutation status as determined by next-generation sequencing. Our results yield indirect evidence that the KRAS zygosity status influences the correlation between these parameters and we show that a well-trained pathologist is indeed capable of accurately assessing TNP. Our findings indicate that tumour zygosity, a feature which has largely been neglected until now, should be taken into account in future studies on (colorectal) molecular tumour heterogeneity.

Mutations of KRAS, NRAS, BRAF and DNA mismatch repair (MMR) status have become an important part of the assessment of patients with colorectal cancer (CRC), while respective clinicopathologic features and prognostic significance in specific stages and related detection strategies remain unclear. We retrospectively analyzed clinicopathologic features and prognosis of 1,834 patients with Stage I-IV colorectal adenocarcinoma. Mutations in KRAS, NRAS and BRAF and DNA MMR status were determined. The mutation rates of KRAS, NRAS and BRAF were 46.4, 3.2 and 3.5%, respectively, and the mismatch repair gene deletion (dMMR) rate was 5.6%. In a multivariate analysis, female, advanced age, tumor type histology, mucinous carcinoma and positive tumor deposits were associated with a high KRAS mutation rate. A high BRAF mutation rate was associated with female, poor differentiation, lymphovascular invasion and positive tumor deposits. Factors associated with high dMMR rates included low age, large tumor size, poor differentiation, Stages I-III. Tumor site was independently associated with KRAS mutation, BRAF mutation and dMMR. KRAS and BRAF mutations were independent risk factors for shorter overall survival (OS) in Stage IV tumors but not in Stage I-III tumors. NRAS mutation was an independent risk factor for shorter OS in Stage I-II tumors. dMMR was independently associated with longer OS in Stage III tumors.

We determined prognostic impact of KRAS, BRAF, PIK3CA and TP53 mutation status and mutation heterogeneity among 164 colorectal cancer (CRC) patients undergoing liver resections for metastatic disease. Mutation status was determined by Sanger sequencing of a total of 422 metastatic deposits. In univariate analysis, KRAS (33.5%), BRAF (6.1%) and PIK3CA (13.4%) mutations each predicted reduced median time to relapse (TTR) (7 vs. 22, 3 vs. 16 and 4 vs. 17 months; p < 0.001, 0.002 and 0.023, respectively). KRAS and BRAF mutations also predicted a reduced median disease-specific survival (DSS) (29 vs. 51 and 16 vs. 49 months; p <0.001 and 0.008, respectively). No effect of TP53 (60.4%) mutation status was observed. Postoperative, but not preoperative chemotherapy improved both TTR and DSS (p < 0.001 for both) with no interaction with gene mutation status. Among 94 patients harboring two or more metastatic deposits, 13 revealed mutation heterogeneity across metastatic deposits for at least one gene. Mutation heterogeneity predicted reduced median DSS compared to homogeneous mutations (18 vs. 37 months; p = 0.011 for all genes; 16 vs. 26 months; p < 0.001 analyzing BRAF or KRAS mutations separately). In multivariate analyses, KRAS or BRAF mutations consistently predicted poor TRR and DSS. Mutation heterogeneity robustly predicted DSS but not TTR, while postoperative chemotherapy improved both TTR and DSS. Our findings indicate that BRAF and KRAS mutations as well as mutation heterogeneity predict poor outcome in CRC patients subsequent to liver resections and might help guide treatment decisions.

Previous studies suggested that the extramural distance (EMD) should be considered in therapeutic decision-making of rectal cancer because it can be used as an indicator of the T3 subclassification; however, reports of impact of EMD/mesorectum ratio on prognosis are rare.The objectives of this study were to evaluate the feasibility of the extramural distance EMD/mesorectum ratio as a maker of the T3 subclassification for T3 mid-low rectal cancer and find the potential radiological marker on MRI for neoadjuvant chemoradiotherapy (nCRT).From December 2012 to December 2016, 287 consecutive patients with MRI-staged T3 mid-low rectal cancer were enrolled. The EMD was defined as the distance from the outer edge of the muscularis propria to the outer edge of tumor, and the mesorectum was measured as the distance from outer edge of muscularis propria to mesorectal fascia (MRF) in the same layer. The association of the EMD/mesorectum ratio and other MRI or clinicopathological factors with survival was analyzed. The independent prognostic factors were estimated by Cox regression analysis.The mean EMD/mesorectum ratio was 0.43. Based on ROC analysis, we chose a EMD/mesorectum ratio of 0.3 for further analyses. Of 287 patients, 163 (56.8%) had a EMD/mesorectum ratio ≥ 0.3. Patients with an EMD/mesorectum ratio ≥ 0.3 had a decreased recurrence free survival (RFS) and overall survival (OS) (P < .001; P = .034, respectively). Of the 163 patients, patients with nCRT had a higher RFS than patients without nCRT (P = .001). Multivariate analysis showed that the EMD/mesorectum ratio was the only independent prognostic factors for RFS.Our study provided evidence that the EMD/mesorectum ratio could be used for T3 subclassification, the optimal cut-off value of EMD/mesorectum ratio was 0.3 when the ratio was applied to classify T3 mid-low rectal cancer patients, and nCRT should be performed for these patients when the EMD/mesorectum ratio is ≥ 0.3.