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      Rare genetic heterogeneity within single tumor discovered for the first time in colorectal liver metastases after liver resection

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          Abstract

          Effective individualized treatment of patients with colorectal liver metastases (CLM) requires tumor genotyping, usually based on the analysis of one single sample per patient. Therapy failure may partially be explained by sampling errors and/or intratumoral genetic heterogeneity. We aimed to demonstrate intratumoral genetic heterogeneity in CLM and enable pathologists to select tumor tissue for genotyping. All the tumors of 86 patients who underwent liver resection for a single CLM were reviewed. Of the 86 patients, 66 patients received chemotherapy and 20 patients did not receive chemotherapy before liver resection. All the tumor areas sampled were analyzed for KRAS, BRAF, PIK3CA, and NRAS mutations. The mutational status was tested in 74 cases, 7 cases had no tumoral cells due to complete responses and 5 blocks were unavailable. Of the 59/74 CLM with > 1 sample, 56 showed the same mutational status between the samples. The remaining 3 cases (5% of all cases) showed genetic heterogeneity for KRAS in 2 and BRAF in 1 patient. Genetic heterogeneity correlated with lower rate of viable tumor cells (p=0.009) and higher rate of mucin pools (p=0.013). We demonstrate for the first time the existence of genetic intratumoral heterogeneity in 5% of CLM. In routine practice, this low incidence does not require the genotyping of additional tumor samples. The correlation between the genetic heterogeneity and some histological components of the CLM should be verified by further in situ mutation assay.

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          Most cited references14

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          Prevalence and heterogeneity of KRAS, BRAF, and PIK3CA mutations in primary colorectal adenocarcinomas and their corresponding metastases.

          Epidermal growth factor receptor (EGFR) antibody therapy is established in patients with wild-type KRAS colorectal carcinoma; however, up to 50% of these patients do not respond to this therapy. To identify the possible causes of this therapy failure, we searched for mutations in different EGFR-dependent signaling proteins and analyzed their distribution patterns in primary tumors and corresponding metastases. Tumor tissues, macrodissected from tumor centers, invasion fronts (n = 100), lymph nodes (n = 55), and distant metastases (n = 20), respectively, were subjected to DNA extraction and mutation analysis of KRAS, BRAF, and PIK3CA. Activating mutations were detected in 41% (KRAS), 7% (BRAF), and 21% (PIK3CA) of the primary tumors. By comparing tumor centers and invasion fronts, the intratumoral heterogeneity of KRAS, BRAF, and PIK3CA mutations was observed in 8%, 1%, and 5% of primary tumors, respectively. Heterogeneity between primary tumors and lymph node metastases was found in 31% (KRAS), 4% (BRAF), and 13% (PIK3CA) of the cases. Heterogeneity between primary tumors and distant metastases was present in two patients (10%) for KRAS and one patient for PIK3CA (5%), but not for BRAF. Discordant results between primary tumors and metastases could markedly be reduced by testing the additional tumor samples. Failure of EGFR antibody therapy in patients with wild-type KRAS colorectal cancer may result from activating BRAF or PIK3CA mutations and false-negative sequencing results caused by intratumoral heterogeneity. Due to the particularly high rates of heterogeneity between primary tumors and lymph node metastases, the latter are least suitable for diagnostic mutation analysis.
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            Comparative genomic analysis of primary versus metastatic colorectal carcinomas.

            To compare the mutational and copy number profiles of primary and metastatic colorectal carcinomas (CRCs) using both unpaired and paired samples derived from primary and metastatic disease sites. We performed a multiplatform genomic analysis of 736 fresh frozen CRC tumors from 613 patients. The cohort included 84 patients in whom tumor tissue from both primary and metastatic sites was available and 31 patients with pairs of metastases. Tumors were analyzed for mutations in the KRAS, NRAS, BRAF, PIK3CA, and TP53 genes, with discordant results between paired samples further investigated by analyzing formalin-fixed, paraffin-embedded tissue and/or by 454 sequencing. Copy number aberrations in primary tumors and matched metastases were analyzed by comparative genomic hybridization (CGH). TP53 mutations were more frequent in metastatic versus primary tumors (53.1% v 30.3%, respectively; P 90% concordance for all five genes). Clonality analysis of array CGH data suggested that multiple CRC primary tumors or treatment-associated effects were likely etiologies for mutational and/or copy number profile differences between primary tumors and metastases. For determining RAS, BRAF, and PIK3CA mutational status, genotyping of the primary CRC is sufficient for most patients. Biopsy of a metastatic site should be considered in patients with a history of multiple primary carcinomas and in the case of TP53 for patients who have undergone interval treatment with radiation or cytotoxic chemotherapies.
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              Pathologic response to preoperative chemotherapy: a new outcome end point after resection of hepatic colorectal metastases.

              The primary goal of this study was to evaluate whether pathologic response to chemotherapy predicts patient survival after preoperative chemotherapy and resection of colorectal liver metastases (CLM). The secondary goal of the study was to identify the clinical predictors of pathologic response. A retrospective review was performed of 305 patients who underwent preoperative irinotecan- or oxaliplatin-based chemotherapy, followed by resection of CLM. Pathologic response was systematically evaluated and reported as the mean of the percentage of cancer cells remaining within each tumor. Univariate and multivariate analyses were performed to identify the predictors of pathologic response and survival. Cumulative 5-year overall survival rates by pathologic response status were as follows: 75% complete response (no residual cancer cells), 56% major response (1% to 49% residual cancer cells), and 33% minor response (> or = 50% residual cancer cells; complete v major response, P = .037; major v minor response, P = .028). Multivariate analysis revealed that only surgical margin status (P = .050; hazard ratio [HR], 1.77) and pathologic response (major response: P = .034; HR, 4.80; minor response: P = .007; HR, 6.93) were independent predictors of survival. Multivariate analysis of the predictors of pathologic response revealed that carcinoembryonic antigen level < or = 5 ng/mL, tumor size < or = 3 cm, and chemotherapy with fluoropyrimidine plus oxaliplatin and bevacizumab were independent predictors of pathologic response. Pathologic response predicts survival after preoperative chemotherapy and resection of CLM. Degree of pathologic response represents a new outcome end point for prognosis after resection of CLM.
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                Author and article information

                Journal
                Oncotarget
                Oncotarget
                Oncotarget
                ImpactJ
                Oncotarget
                Impact Journals LLC
                1949-2553
                24 April 2018
                24 April 2018
                : 9
                : 31
                : 21921-21929
                Affiliations
                1 AP-HP Hôpital Paul Brousse, Laboratoire d’Anatomie Pathologique, Villejuif, France
                2 Inserm, Unité 1193, Université Paris-Saclay, Villejuif, France
                3 Univ Paris-Sud, UMR-S 1193, Université Paris-Saclay, Villejuif, France
                4 DHU Hepatinov, Villejuif, France
                5 AP-HP Hôpital Paul Brousse, Département d’Oncogénétique, Villejuif, France
                6 AP-HP Hôpital Paul-Brousse, Centre Hépato-Biliaire, Villejuif, France
                7 Inserm, Unité 935, Université Paris-Saclay, Villejuif, France
                8 University Medical Center Utrecht, Department of Surgery, Utrecht, The Netherlands
                Author notes
                Correspondence to: Mylène Sebagh, mylene.sebagh@ 123456pbr.aphp.fr
                Article
                25119
                10.18632/oncotarget.25119
                5955166
                9f019246-818d-4eed-b377-0f1e87ddcf8f
                Copyright: © 2018 Sebagh et al.

                This is an open-access article distributed under the terms of the Creative Commons Attribution License 3.0 (CC BY 3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

                History
                : 5 June 2017
                : 21 March 2018
                Categories
                Research Paper

                Oncology & Radiotherapy
                colorectal liver metastases,intratumoral genetic heterogeneity,pathological response,mutations

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