Primary Colorectal Tumors Research Articles

The role of primary tumor (PT) site as prognostic factor after resection of colorectal (CRC) liver metastases (LM): A mono-institutional cohort study.

4081 Background: Radical resection of LM is the only chance of cure for liver-only mCRC pts. Besides the evaluation of technical resectability, several factors must be taken into account for the evaluation of recurrence risk. Among them we should consider the Fong Risk Score and its modified version, including RAS/BRAF status (Brudvik’s score). Tumor sidedness is an important prognostic factor in CRC. The impact of PT site on the outcome of LM resection is still debated. Hence, we retrospectively analysed mCRC pts, underwent to radical LM resection at our Institution, investigating the impact of PT site on DFS and OS. Methods: Liver-only mCRC pts underwent to radical LM resection were included. The association of PT site with DFS and OS was evaluated. The following variables were collected: gender; age (≥ vs < 75 years ); ECOG PS; CEA baseline level; PT site; RAS and BRAF status; mucinous histology; grading (G1-2 vs G3); RECIST response during preoperative treatment; resected PT; synchronous vs metachronous; number of LM; bilobar vs unilobar LM; LM diameter ≥ 5 cm; R0 vs R1 resection. Univariate and multivariate analyses for DFS and OS were performed. Results: A total of 463 liver-only mCRC pts underwent to radical LM resection were included. Seventy (15%) pts had a right-sided (r-s) tumor and 393 (85%) pts a left-sided (l-s) tumor. R-s CRC pts more often had RAS/BRAF mutations in comparison to l-s tumors (76% vs 37%; p < 0.0001). Median DFS and OS was 13.1 and 41.6 months, respectively, in r-s CRC vs 16.0 (p = 0.65) and 62.2 months (p = 0.033), respectively, in l-s tumors. At the multivariate analysis no significant association with survival parameters was shown for tumor sidedness. At the multivariate analysis, R0 resection was independently associated both with better DFS and OS; RAS/BRAF wt CRC and resected PT were significantly associated with improved OS. Considering all wt CRC pts (N = 237), 14 (6%) pts had r-s tumor and 223 (94%) l-s tumor. No significant association of tumor sidedness with survival was shown (DFS r = 10.0 vs l = 16.0 months, p = 0.62; OS r = 40.3 vs l = 66.2 months, p = 0.12). Conclusions: Our results showed that a significant smaller proportion of r-s CRC underwent to radical LM resection, indirectly confirming its worse prognosis. Among radically resected pts, r-s CRC was associated to a shorter OS (significant) and DFS (not significant) compared to l-s CRC, but it was not confirmed at the multivariate analysis. We can conclude that right PT site should not be considered as a contraindication for radical LM surgery, when feasible.

Emerging RAS, BRAF, and EGFR mutations in cell-free DNA of metastatic colorectal patients are associated with both primary and secondary resistance to first-line anti-EGFR therapy.

Oncogenic RAS mutations are negative biomarkers of response to epidermal growth factor receptor (EGFR) blockade. RAS mutations are usually detected in biopsies of primary colorectal tumors. However, the genomic profiles of primary tumors and metastases are not always concordant, and chemotherapeutic agents can alter the tumor molecular landscape. Cell-free DNA (cfDNA) is a novel tool to detect molecular heterogeneity. This study evaluated the clinical utility of cfDNA to predict primary or secondary resistance to EGFR blockade in patients with metastatic colorectal cancer. Thirty metastatic colorectal cancer patients without RAS and BRAF mutations were prospectively enrolled and treated with cytotoxic agents and EGFR blockade as first-line therapy. cfDNA was analyzed for the presence of RAS, BRAF, and EGFR (S492R) point mutations before initiating chemotherapy and every 2months during chemotherapy. The analysis was performed in 223 plasma samples from all 30 patients. Of the 30 patients, five had RAS mutations in their cfDNA before starting chemotherapy and did not respond. Twenty-four of the remaining 25 patients without cfDNA RAS mutations had a response. Twenty of the 24 responders developed secondary resistance and cfDNA RAS mutations were found in 17 of the 20. cfDNA BRAF mutations were found in seven, and EGFR mutations were found in eight of the 20 patients. Emerging RAS, BRAF, and EGFR mutations occurred in patients with primary and secondary resistance to EGFR blockade. The detection of these mutations in cfDNA is a promising approach to predict treatment response and secondary resistance.

Colorectal adenocarcinoma metastasis to palatine tonsil as the first presentation: A case report and literature review

AbstractMetastases account for only 0.8% of all tonsillar malignancies and the lung, breast, kidney and melanoma are the commonest primary sites. Metastasis of colorectal carcinoma to the palatine tonsil is rare. We report of a 73‐year‐old man who presented with metastatic colorectal carcinoma in the right tonsil as the first presentation; the primary colorectal adenocarcinoma was diagnosed retrospectively. On magnetic resonance imaging, a 3.45 cm tumour was identified in the right oropharynx with associated lymphadenopathy. Tonsillectomy histology confirmed metastatic colorectal adenocarcinoma. On further imaging, an 8cm mass was identified in the sigmoid colon and a biopsy confirmed a poorly differentiated adenocarcinoma. The patient received two cycles of palliative chemotherapy but died 5 months following presentation. Literature review identified 13 case reports in the English scientific literature and clinicopathological analysis of these is presented. The mean age was 55.21 years (age range – 37–81) with male predominance. Half of the patients had a primary tumour in the rectum. Tonsillar involvement was either primary presentation or has been present at the time of diagnosis of primary colorectal tumour in five cases; in all of these, the differentiation of tumour was poor and 3/5 had signet ring morphology. These tumours showed poor prognosis and the life expectancy was 6–15 months irrespective of the type of treatment. This case highlights the importance of considering metastatic carcinoma in the differential diagnosis even at unlikely sites.

Abstract A26: Precise characterization and comparison of KRAS proteoforms by top-down mass spectrometry

Abstract The two KRAS isoforms, 4A and 4B, exhibit high sequence identity, differing mainly in their C-terminal “hypervariable regions”, which bear post-translational modifications (PTMs) governing their association with the plasma membrane and downstream signaling effectors. Moreover, the KRAS gene bears three “mutation hotspot” residues (Gly12, Gly13, and Gln61) represented in a high percentage of human cancers. The similarity between KRAS isoforms, in addition to HRAS and NRAS, renders linking KRAS mutations and PTMs significantly challenging by standard proteomic methods based on digestion of proteins into short peptides. However, intact modified protein forms, or proteoforms, of KRAS4A and KRAS4B can be identified and characterized by “top-down” (TD) proteomic methods, elucidating crosstalk between N-terminal mutations and C-terminal PTMs with precise molecular detail. Previously, we employed the TD approach as part of a novel workflow to precisely characterize KRAS4B proteoforms isolated from colorectal cancer cell lines and primary tumor samples by immunoprecipitation (IP) and subsequent analysis on a benchtop Orbitrap mass spectrometer (1). Here, we modified our IP-TD protocol to include KRAS4A, then applied our workflow to the characterization, quantification, and direct comparison of KRAS4A and KRAS4B proteoforms within the context of multiple cancer cell lines. We hypothesized that we would be able to identify distinct proteoform populations for each KRAS isoform, which could then be compared both within and between different contexts. We have thus far identified nine novel proteoforms of KRAS4A, which not only exhibits differential PTM to KRAS4B, but varies widely in both abundance and PTM profile across all cell lines evaluated. We have also applied IP-TD to the analysis of endogenous KRAS4A and KRAS4B proteoforms using a more powerful 21 Tesla FT-ICR mass spectrometer at the National High Magnetic Field Laboratory. The high mass resolving power, mass measurement accuracy, and spectral acquisition rate achieved at high field combined with use of efficient dissociation methods and an external fragment ion accumulator to improve signal-to-noise ratios of MS/MS spectra produced unparalleled results with respect to degree of KRAS proteoform characterization. We were able to identify up to ten new KRAS proteoforms per context, several of which appear to be mutation- or context-specific. These latest advances have broadened our understanding of KRAS biology and provided new insights into the potential roles of KRAS4A and KRAS4B proteoforms in colorectal and other cancers. Reference 1. Ntai I, Fornelli L, DeHart CJ, Hutton JE, Doubleday PF, LeDuc RD, van Nispen AJ, Fellers RT, Whiteley G, Boja ES, Rodriguez H, Kelleher NL. Precise characterization of KRAS4b proteoforms in human colorectal cells and tumors reveals mutation/modification crosstalk. Proc Natl Acad Sci U S A 2018 Apr 17;115(16):4140-5. Citation Format: Caroline J. DeHart, Lissa C. Anderson, Lauren M. Adams, Luca Fornelli, Christopher L. Hendrickson, Neil L. Kelleher. Precise characterization and comparison of KRAS proteoforms by top-down mass spectrometry [abstract]. In: Proceedings of the AACR Special Conference on Targeting RAS-Driven Cancers; 2018 Dec 9-12; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(5_Suppl):Abstract nr A26.

Investigating the concordance in molecular subtypes of primary colorectal tumors and their matched synchronous liver metastasis.

To date, no systematic analyses are available assessing concordance of molecular classifications between primary tumors (PT) and matched liver metastases (LM) of metastatic colorectal cancer (mCRC). We investigated concordance between PT and LM for four clinically relevant CRC gene signatures. Twenty-seven fresh and 55 formalin-fixed paraffin-embedded pairs of PT and synchronous LM of untreated mCRC patients were retrospectively collected and classified according to the MSI-like, BRAF-like, TGFB activated-like and the Consensus Molecular Subtypes (CMS) classification. We investigated classification concordance between PT and LM and association of TGFBa-like and CMS classification with overall survival. Fifty-one successfully profiled matched pairs were used for analyses. PT and matched LM were highly concordant in terms of BRAF-like and MSI-like signatures, (90.2% and 98% concordance, respectively). In contrast, 40% to 70% of PT that were classified as mesenchymal-like, based on the CMS and the TGFBa-like signature, respectively, lost this phenotype in their matched LM (60.8% and 76.5% concordance, respectively). This molecular switch was independent of the microenvironment composition. In addition, the significant change in subtypes was observed also by using methods developed to detect cancer cell-intrinsic subtypes. More importantly, the molecular switch did not influence the survival. PT classified as mesenchymal had worse survival as compared to nonmesenchymal PT (CMS4 vs CMS2, hazard ratio [HR] = 5.2, 95% CI = 1.5-18.5, P = .0048; TGFBa-like vs TGFBi-like, HR = 2.5, 95% CI = 1.1-5.6, P = .028). The same was not true for LM. Our study highlights that the origin of the tissue may have major consequences for precision medicine in mCRC.

Association of lncRNA-p53 regulatory network (lincRNA-p21, lincRNA-ROR and MALAT1) and p53 with the clinicopathological features of colorectal primary lesions and tumors.

Colorectal cancer (CRC) is a common intestinal cancer with a high mortality rate. Early detection of this type of cancer is fundamental to the prevention of the disease, which results in improved survival rates. In the human colon tissue, transition from normal epithelium to adenoma is considered to be caused by unknown molecular incidents occurring over 5–10 years. The detection of CRC has proved problematic when in the early stages of disease. In addition, identifying suitable biomarkers for the detection of CRC progress in patients remains one of the most significant challenges. Long non-coding RNAs have been demonstrated to contribute to the promotion of CRC. The aim of the present study was to investigate the clinical and biological significance of long intergenic non-coding (linc)RNA-p21, lincRNA-regulator of reprogramming (ROR) and metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) in the colon tumor and polyp tissue, and the association that these have with the expression of p53 at the mRNA level. Neoplastic and paired adjacent normal tissue samples were obtained from 72 patients (46 polyps and 26 tumors). Reverse transcription-quantitative PCR was performed to determine the relative fold changes in the expression of lincRNA-p21, lincRNA-RoR, MALAT1 and p53 in the samples. A significant association was observed between the levels of MALAT1 and p53 in neoplasm tissues (R=0.073; P<0.05). The relative expression of the MALAT1 gene revealed a statistically significant difference between the different polyp types and number of polyps (P=0.0028 and 0.022, respectively). Adjuvant therapy in patients with tumors revealed an association between the levels of lincRNA-ROR and lincRNA-p21 expression (P=0.015 and 0.038, respectively). MALAT1 may be selected as an early detection biomarker for CRC. Furthermore, lincRNA-ROR and lincRNA-p21 may serve as prognostic and therapeutic biomarkers in patients with CRC.

Identifying a Novel Pathogenic Mutation in Exon 3 of ARID1A Gene in Colon Cancer

ARID1A, a bona fide tumor suppressor, is the third most mutated gene in human colorectal cancer. In this paper, we reported the identification of a novel mutation in one of 20 primary human colorectal cancer tumors. Sanger sequencing of the exon 3 of the ARID1A gene revealed a novel heterozygous non-sense mutation of the c.1653C>G. This resulted in the premature termination of the 2285 amino acid protein at the 551st codon. Mutation Taster predicted this novel mutation to be pathogenic. Immunohistochemical analysis revealed the loss of ARID1A protein expression in cancerous tissues harboring ARID1A mutation. As far as we know, this is the first report on the mutation of ARID1A gene in an Iranian patient. This mutation can expand the spectrum of ARID1A gene pathogenic mutations among colorectal cancer patients.

Angiogenesis in primary colorectal cancer and matched metastatic tissues: Biological and clinical implications for anti-angiogenic therapies.

Metastasis remains a notable issue in patients with newly diagnosed colorectal carcinomas (CRC). Although anti-angiogenic therapies target metastatic diseases, hypoxia-inducible factor-1 α (HIF-1α) and vascular endothelial growth factor (VEGF) status are routinely evaluated in primary tumors as metastatic sites are infrequently biopsied. The present study aimed to investigate the expression and significance of HIF-1α, VEGF and microvascular density (MVD) in primary tumors and corresponding metastatic CRC tissues. HIF-1α, VEGF and CD34 status were analyzed via immunohistochemistry analysis in 46 patients who underwent surgical resection of primary CRC (35 colon and 11 rectum) and matched metastases (lymph node and liver metastases) in Shandong Cancer Hospital. The association between selected biomarker status and clinicopathological characteristics was analyzed, and expression levels in primary tumors and corresponding metastases were compared. A total of 46 paired colorectal primary tumor and synchronous metastases samples were acquired for analysis using a standardized HIF-1α, VEGF and CD34 immunohistochemical procedure. The results demonstrated that the positive rates of HIF-1α and VEGF in primary CRC were 70 and 73.9%, respectively. HIF-1α (60.9%) and VEGF (58.7%) expression decreased in the lymph metastatic samples compared with primary CRC. Conversely, the level of MVD in primary tumors was significantly higher compared with metastatic tumors. No significant differences were demonstrated between HIF-1α and VEGF expression and the different clinicopathological features in primary CRC and corresponding metastases. Primary carcinomas and matched metastatic tissues demonstrated a moderate level of consistent immunoreactivity for HIF-1α and VEGF. HIF-1α, VEGF and CD34 were expressed in both primary tumors and corresponding metastases of CRC, suggesting that they may be involved in the development of metastasis. HIF-1α and VEGF expression in primary sites was consistent with that observed in metastases; however, it varied from that exhibited in MVD. The current analysis will improve the current understanding of the metastasis models and provide further evidence for evaluating the response to HIF-1α and VEGF inhibitors.

High mutational concordance between primary colorectal tumors and associated pulmonary metastases.

Precision medicine has altered the management of colorectal cancer (CRC). However, the concordance of mutational findings between primary CRC tumors and associated pulmonary metastases (PM) is not well-described. This study aims to determine the concordance of genomic profiles between primary CRC and PM. Patients treated for colorectal PM at a single institution from 2000 to 2017 were identified. Mutational concordance was defined as either both wild-type or both mutant alleles in lung and colorectal lesion; genes with opposing mutational profiles were reported as discordant. Thirty-eight patients met inclusion criteria, among whom KRAS, BRAF, NRAS, MET, RET, and PIK3CA were examined for concordance. High concordance was demonstrated among all evaluated genes, ranging from 86% (KRAS) to 100% concordance (NRAS, RET, and MET). De novo KRAS mutations were detected in the PM of 4 from 35 (11%) patients, 3 of whom had previously received anti-epidermal growth factor receptor (EGFR) therapy. Evaluation of Cohen's κ statistic demonstrated moderate to perfect correlation among evaluated genes. Because high intertumoral genomic homogeneity exists, it may be reasonable to use primary CRC mutational profiles to guide prognostication and targeted therapy for PM. However, the possibility of de novo KRAS-mutant PM should be considered, particularly among patients previously treated with anti-EGFR therapy.

Stereotactic ablative radiation therapy for pulmonary metastases: Improving overall survival and identifying subgroups at high risk of local failure

Background & purposeStereotactic ablative radiation therapy (SABR) is an emerging treatment option for patients with pulmonary metastases; identifying patients who would benefit from SABR can improve outcomes. Materials & methodsWe retrospectively analyzed local failure (LF), distant failure (DF), overall survival (OS), and toxicity in 317 patients with 406 pulmonary metastases treated with SABR in January 2006–September 2017 at a tertiary cancer center. ResultsMedian follow-up time was 23 months. Primary adrenal, colorectal, sarcoma, or pancreatic (“less responsive”) tumors led to high rates of LF. LF rates for patients with less responsive vs. responsive tumors were 4.6% vs. 1.6% at 12 months and 12.8% vs. 3.9% at 24 months (hazard ratio [HR] 0.29, 95% confidence interval [CI] 0.11–0.73; Log-Rank P = 0.0087). A nomogram for 24-month local control was created using Cox multivariate factors (surgical history, planning target volume, primary disease site, lung lobe location). Treating patients with ≤3 pulmonary metastases vs. >3 pulmonary metastases was associated with improved 24-month (74.2% vs. 59.3%) and 48-month (47.7% vs. 35.1%) OS (HR 0.66, 95% CI 0.47–0.95; Log-Rank P = 0.043), and reduced 12-month (22.5% vs. 50.8%) and 24-month (31.8% vs. 61.4%) intrathoracic DF (HR 0.53, 95% CI 0.38–0.74; Log-Rank P < 0.0001). The most common toxicity was asymptomatic pneumonitis (14.8%). Six patients had grade 3 events (5 pneumonitis, 1 brachial plexus). ConclusionsSABR for pulmonary metastases was effective and well tolerated. Irradiating limited intrathoracic sites of disease led to improved OS and intrathoracic DM. Higher SABR doses or surgery could be considered for less radio-responsive primary tumors.

Platinum-based therapy of patients with gastrointestinal cancers that harbor homologous recombination DNA damage response (HR-DDR) mutations: A single institutional retrospective analysis.

836 Background: HR-DDR deficiencies have been described across cancer types and associated with response to specific therapies, including platinum (Pt)-based drugs and poly ADP-ribose polymerase (PARP) inhibitors. We sought to estimate the frequency of HR-DDR gene mutations in gastrointestinal (GI) cancers and determine if these patients (pts) benefit from Pt-based therapy. Methods: A retrospective chart review was performed on 421 pts with GI cancers treated at our institution. Tumors were categorized as colorectal (CRC), gastroesophageal (GE), pancreatic (PDA), hepatobiliary (HB), or other. All had next-generation sequencing with mutations in one or more of the following HR-DDR genes: BRCA1, BRCA2, PALB2, CHEK2, ATM, ARID1A, MRE11A, NBN, BARD1, and BL M. Overall survival (OS) of pts was analyzed using Log-rank test. Results: Of those analyzed, 127 pts (84 women and 43 men) met the inclusion criteria. Forty-eight percent had primary CRC tumors, and the remainder had primary GE (17%), PDA (14%), HB (10%), and other GI (11%) tumors. Fifty-four percent had stage IV disease. Sixty-five percent received Pt-based therapy at some point during their disease course. HR-DDR analysis revealed the following mutation rates: 34% ARID1A; 16% ATM; 19% BRCA2; and 9% BRCA1. OS analysis showed no significant survival advantage based on stage or mutation type for any of the disease-specific cohorts. There was no significant OS benefit in pts who received Pt-based therapy vs. those who did not, although pts with ARID1A-mutated tumors did show a trend towards improved OS (P = 0.09). Conclusions: Despite our limited cohort, our data suggest that pts with GI tumors harboring certain HR-DDR gene mutations might benefit from Pt-based therapy, supporting the development of mutation-specific Pt-based clinical trials.

An Optimised Protocol Harnessing Laser Capture Microdissection for Transcriptomic Analysis\xa0on Matched Primary and Metastatic Colorectal Tumours

Generation of large amounts of genomic data is now feasible and cost-effective with improvements in next generation sequencing (NGS) technology. Ribonucleic acid sequencing (RNA-Seq) is becoming the preferred method for comprehensively characterising global transcriptome activity. Unique to cytoreductive surgery (CRS), multiple spatially discrete tumour specimens could be systematically harvested for genomic analysis. To facilitate such downstream analyses, laser capture microdissection (LCM) could be utilized to obtain pure cell populations. The aim of this protocol study was to develop a methodology to obtain high-quality expression data from matched primary tumours and metastases by utilizing LCM to isolate pure cellular populations. We demonstrate an optimized LCM protocol which reproducibly delivered intact RNA used for RNA sequencing and quantitative polymerase chain reaction (qPCR). After pathologic annotation of normal epithelial, tumour and stromal components, LCM coupled with cDNA library generation provided for successful RNA sequencing. To illustrate our framework’s potential to identify targets that would otherwise be missed with conventional bulk tumour sequencing, we performed qPCR and immunohistochemical technical validation to show that the genes identified were truly expressed only in certain sub-components. This study suggests that the combination of matched tissue specimens with tissue microdissection and NGS provides a viable platform to unmask hidden biomarkers and provides insight into tumour biology at a higher resolution.

PLAP -CAR Tcells mediate high specific cytotoxicity against colon cancer cells.

Placental alkaline phosphatase, PLAP encoded by ALPP gene in humans is mainly expressed in placenta and testis, and not expressed in any other normal tissues. PLAP is overexpressed in colorectal cancers which makes it an attractive target for CAR (chimeric antigen receptor)-T cell therapy. PLAP mRNA expression was detected in 21.5% (25 out of 116) of colorectal cancer cell lines and this expression was confirmed by FACS at the protein level. In addition, IHC staining on primary colorectal cancer tumors demonstrated PLAP expression in >20% of colorectal cancer tumors. We generated mouse and humanized PLAP ScFv-CAR-T cells and demonstrated high specificity against PLAP-positive colon cancer cells using RTCA (real-time cytotoxicity assay) and IFN-gamma secretion. In addition, humanized-CAR-T cells significantly decreased Lovo xenograft tumor growth in vivo. The combination of hPLAP-CAR-T cells with PD-1, PD-L1 or LAG-3 checkpoint inhibitors significantly increased the activity of hPLAP-CAR-T cells. This study demonstrates ability of novel PLAP-CAR-T cells to kill colorectal cancers and that the extent of killing can be increased by combination with checkpoint inhibitors.

Laparoscopic colorectal resection combined with simultaneous thermal ablation or surgical resection of liver metastasis: a retrospective comparative study

Objective Colorectal liver metastasis is a critical cause of mortality. However, the safety and long-term prognosis of simultaneous colorectal tumor resection along with hepatic lesion ablation are debated. The current analysis was conducted to further clarify the controversy. Methods In this retrospective study, we collected data of 68 patients who underwent ablation or resection for liver lesions combined with simultaneous laparoscopic primary colorectal tumor resection between September 2011 and October 2016 at the Third Affiliated Hospital of Sun Yat-sen University. Perioperative outcomes and long-term follow-up data were compared between patients in the resection and ablation groups. Results Both groups had similar surgical duration (286.70 ± 78.33 vs. 313.67 ± 80.90 min), conversion rate (2 vs. 0), total expenses (81.51 ± 20.20 vs. 82.21 ± 27.81 kRMB, p = .914) and morbidities (11 vs. 24, p = .667). However, the postoperative hospital stays (12.82 ± 9.25 vs. 8.40 ± 2.38 d) and transfusion rates (56.52% vs. 8.89%) were significantly lower in the ablation group. The long-term overall survival (p = .714), disease-free survival (p = .680) and intra-hepatic recurrent-free survival (p = .496) were comparable between both groups. Conclusion With respect to simultaneous treatment for both primary colorectal cancer and liver metastasis, hepatic lesion ablation was associated with lower blood loss and hospital stay duration than liver resection, without compromising the surgical safety and long-term prognosis.

Mismatch repair status between primary colorectal tumor and metastatic tumor, a retrospective consistent study

Objectives Mismatch repair (MMR) and Microsatellite instability (MSI) are critical when considering immunotherapy and chemotherapeutic drugs an option for patients with colorectal cancer (CRC). We investigated the consistence of MMR status as well as MSI between primary CRC and metastatic tumor to see if the expression of four MMR proteins and the status of MSI are congruent in primary tumor and metastatic tumor. With the results of the study and future more relevant studies, the sites of MMR testing may be more precise for individualized treatment.Study design Patients with clear diagnosis of sporadic CRC and distal organ metastasis were identified from a prospectively established database. The status of MMR and MSI was evaluated by immunohistochemistry (IHC) and Polymerase Chain Reaction (PCR) respectively of synchronously obtained tissue samples.Results Forty patients with complete clinical date were enrolled. For primary tumor, 36/40 samples were tested as MMR-proficient (pMMR) and 4 were MMR-deficient (dMMR). For metastatic samples, 30 samples were tested as pMMR while 10 samples were dMMR. Six out of forty patients were tested as inconsistent status of MMR and MSI. After statistical analysis, the expression status of MMR was not statistically significant between primary and metastatic tumors (P=0.1405, larger than 0.05).Conclusion Based on our samples, the status of MMR between primary CRC and metastatic tumor was consistent, thus test of MMR status can be performed at both sites. However, due to the limited samples enrolled in our study, the results should be interpreted carefully.

96P - Incidence, characteristics and prognosis in colorectal cancer with CNS metastases

BackgroundBrain metastases (BM) due to colorectal cancer (CRC) are an infrequent event. Previous research suggests that patients with pulmonary metastases, rectal primaries and KRAS mutations are at an increased risk of BM. Despite multidisciplinary treatment, survival following BM remains poor. We aimed to analyse the incidence, genomic profiling, treatment administered and survival in patients with BM from CRC within our cancer service. MethodsA retrospective analysis of 1346 CRC patients at two comprehensive cancer centres in Western Sydney identified 52 patients with BM. Data was subsequently collected on patient demographics, tumour and treatment characteristics. KRAS and BRAF mutation status from primary colorectal tumour specimens and surgical resection of BM was assessed. Survival data was analysed by the Kaplan-Meier method. ResultsThe incidence of BM in our cohort was 3.9%. The mean age of patients was 66 (35-82) with 48% female and 52% male in the BM group compared to 36% female and 64% male in the non-BM group. 33% of patients were wildtype (WT), 62% had a RAS mutation and 5% were BRAF mutant. The median time between diagnosis of primary CRC and development of BM did not differ between RAS, RAF and WT (37, 50 and 43 months). 70% of WT patients presented with one BM compared to 45% of KRAS mutated patients although this was not statistically significant (p = 0.13). 38% of patients had surgery while 81% had radiotherapy (56% WBRT, 44% SRS) to treat their BM. The median PFS across all groups was 3.2 months and median OS was 3.9 months. Median PFS was significantly longer in patients who received surgery, chemotherapy and radiotherapy following their diagnosis of BM (12.3 months) versus surgery alone (1 month) or surgery and radiotherapy (4.4 months) (p = 0.022). Mutational status or number of BM did not impact on PFS or OS. Patients with synchronous liver metastases had a significantly shorter median OS of 3 months versus 13 months in those without liver metastases (p = 0.008). ConclusionsBrain metastases remains an infrequent event in patients with metastatic colorectal cancer. KRAS and BRAF mutations do not appear to have any effect on prognosis or response to treatment in CRC patients with BM. Survival of CRC patients following BM is poor and novel approaches are needed. Legal entity responsible for the studyThe authors. FundingWestern Sydney Local Health District. DisclosureK.Y.M. Wong: Advisory / Consultancy: Baxalta; Speaker Bureau / Expert testimony: Sirtex; Travel / ccommodation / Expenses: MSD Oncology. All other authors have declared no conflicts of interest.

Cost-effectiveness analysis of selective first-line use of biologics for unresectable RAS wild-type left-sided metastatic colorectal cancer.

Evidence from a retrospective analysis of multiple large phase iii trials suggested that primary tumour location (ptl) in RAS wild-type metastatic colorectal cancer (wtRAS mcrc) might have predictive value with respect to response to drug therapies. Recent studies also show a potential preferential benefit for epidermal growth factor inhibitors (egfris) for left-sided tumours. In the present study, we aimed to determine the incremental cost-effectiveness ratio (icer) for the first-line use of an egfri for patients with left-sided wtRAS mcrc. We developed a state-transition model to determine the cost effectiveness of alternative treatment strategies in patients with left-sided mcrc:■ Standard of care■ Use of an egfri in first-line therapyThe cohort for the study consisted of patients diagnosed with unresectable wtRAS mcrc with an indication for chemotherapy and previously documented ptl. Model parameters were obtained from the published literature and calibration. The perspective was that of a provincial ministry of health in Canada. We used a 5-year time horizon and an annual discount rate of 1.5%. Selecting patients for first-line egfri treatment based on left-sided location of their colorectal primary tumour was more effective than the standard of care, resulting in an increase in quality-adjusted life-years (qalys) of 0.226 (or 0.644 life-years gained). However, the strategy was also more expensive, costing an average of $60,639 more per patient treated. The resulting icer was $268,094 per qaly. A 35% price reduction in the cost of egfri would be needed to make this strategy cost-effective at a willingness-to-pay threshold (wtp) of $100,000 per qaly. Selective use of an egfri based on ptl was more cost-effective than unselected use of those agents; however, based on traditional wtp thresholds, it was still not cost-effective. While awaiting the elucidation of more precise predictive biomarkers that might improve cost-effectiveness, the price of egfris could be reduced to meet the wtp threshold.

Prevalence of BRAF gene mutation in samples of primary and metastatic colorectal cancer: A meta-analysis.

Understanding the prevalence and biology of BRAF gene can improve the treatment methods of cancerous patients. This study aims to estimate the prevalence of BRAF gene mutation in samples of primary and metastatic colorectal cancer using meta-analysis method. We searched PubMed, Scopus, ScienceDirect, Ovid and Google Scholar motor engine using MeSH terms of relevant keywords. During the screening phase, titles, abstracts and full texts were reviewed and risk of bias was assessed for all selected papers based on Newcastle-Ottawa Scale (NOS) checklist. The results of the primary studies were combined using meta-analysis. Of 95 eligible studies entered into the meta-analysis, prevalence of BRAF gene mutation had been assessed among 19,484 primary tumour samples as well as 12,256 metastatic samples. The total prevalence of BRAF gene mutation among primary tumour samples was estimated as of 10.16% (8.09-12.22) in the world, 0.41% (0-1.89) in EMRO region, 10.06% (7.54-12.59) in EURO region, 10.33% (7.24-13.43) in SEARO region and 11.33% (7.29-15.37) in WPRO region. The pooled estimates for BRAF gene mutation in metastatic samples were 6.53% (5.09-7.96), 8.07% (5.57-10.56), 5.38% (3.75-7.02) and 5.55% (1.72-9.38) for all regions, EURO, WPRO and PAHO regions respectively. Our results showed evidences of BRAF gene mutation in one-tenth of primary colorectal tumour samples in EURO, PAHO, SEARO and WPRO regions which was considerably higher than that of the EMRO region.

Linking stemness with colorectal cancer initiation, progression, and therapy.

The discovery of cancer stem cells caused a paradigm shift in the concepts of origin and development of colorectal cancer. Several unresolved questions remain in this field though. Are colorectal cancer stem cells the cause or an effect of the disease? How do cancer stem cells assist in colorectal tumor dissemination to distant organs? What are the molecular or environmental factors affecting the roles of these cells in colorectal cancer? Through this review, we investigate the key findings until now and attempt to elucidate the origins, physical properties, microenvironmental niches, as well as the molecular signaling network that support the existence, self-renewal, plasticity, quiescence, and the overall maintenance of cancer stem cells in colorectal cancer. Increasing data show that the cancer stem cells play a crucial role not only in the establishment of the primary colorectal tumor but also in the distant spread of the disease. Hence, we will also look at the mechanisms adopted by cancer stem cells to influence the development of metastasis and evade therapeutic targeting and its role in the overall disease prognosis. Finally, we will illustrate the importance of understanding the biology of these cells to develop improved clinical strategies to tackle colorectal cancer.

Stenting as a bridge to surgery for obstructed stage IV colorectal cancers - long-term outcomes of a 10-year study.

Successful stenting of an obstructing colorectal tumor can avert upfront emergency surgery in malnourished obstructed patients with metastatic disease and poor physiological condition. This study aims to evaluate the outcomes of stenting followed by primary colorectal tumor resection among patients with obstructed stage IV colorectal cancer at presentation, over a 10-year period. From 2007 to 2016, a cohort comprising 25 consecutive patients were retrospectively reviewed from a prospectively collected database. The durability of palliation of bowel obstruction, oncological outcomes and factors influencing overall survival were analyzed. No re-interventions were required for bowel obstruction during the study period. The overall perioperative morbidity rate was 16%, with no postoperative 90-day mortality. Laparoscopic resection rate was 52% and stoma formation rate was 8%. The median overall survival was 24 months for the entire cohort, and the 1-, 3- and 5-year survival rates were 80%, 35% and 23.33% respectively. More than one site of distant metastases, peritoneal involvement, and elevated carcinoembryonic antigen levels were significantly associated with poorer survival outcomes. Patients with peritoneal-only metastasis had worse outcomes, with a median survival of 7 months and no patients surviving beyond 18 months. Stenting followed by resection of the primary obstructing colorectal cancer provides durable palliation among patients with stage IV disease, with low perioperative morbidity and stoma formation rates. Superior survival was observed among patients with single-site, non-peritoneal distant metastases.