Identification of unique rectal cancer-specific subtypes.

BACKGROUND: Existing colorectal cancer subtyping methods were generated without much consideration of potential differences in expression profiles between colon and rectal tissues. Moreover, locally advanced rectal cancers at resection often have received neoadjuvant chemoradiotherapy which likely has a significant impact on gene expression. METHODS: We collected mRNA expression profiles for rectal and colon cancer samples (n = 2121). We observed that (i) Consensus Molecular Subtyping (CMS) had a different prognosis in treatment-naïve rectal vs. colon cancers, and (ii) that neoadjuvant chemoradiotherapy exposure produced a strong shift in CMS subtypes in rectal cancers. We therefore clustered 182 untreated rectal cancers to find rectal cancer-specific subtypes (RSSs). RESULTS: We identified three robust subtypes. We observed that RSS1 had better, and RSS2 had worse disease-free survival. RSS1 showed high expression of MYC target genes and low activity of angiogenesis genes. RSS2 exhibited low regulatory T cell abundance, strong EMT and angiogenesis signalling, and high activation of TGF-ß, NF-κB, and TNF-α signalling. RSS3 was characterised by the deactivation of EGFR, MAPK and WNT pathways. CONCLUSIONS: We conclude that RSS subtyping allows for more accurate prognosis predictions in rectal cancers than CMS subtyping and provides new insight into targetable disease pathways within these subtypes.

Molecular typing and mutational characterization of rectal neuroendocrine neoplasms.

BACKGROUND: Rectal neuroendocrine neoplasms (NENs) are rare neoplasms with limited understanding of its genomic alterations and molecular typing. METHODS: The paraffin-embedded tissue specimens of 38 patients with rectal NENs after surgery were subjected to whole gene sequencing (WGS), and mutation profilings were drawn to identify high-frequency mutation genes, copy-number variations (CNVs), tumor mutation burden (TMB), signal pathways, mutation signatures, DNA damage repair (DDR) genes, and molecular types. The differences of mutated genes and signaling pathways in different pathological grades and metastatic/non-metastatic groups were compared. It helped to search for potential targets. RESULTS: C > T and T > C transitions are the most common base substitutions in rectal NENs. DNA mismatch repair deficiency, DNA base modifications, smoking and exposure to ultraviolet light might play a role in the occurrence of rectal NENs. DAXX, KMT2C, BCL2L1, LTK, MERTK, SPEN, PKN1, FAT3, and LRP2 mutations were found in only low-grade rectal NETs, whereas APC, TP53, NF1, SOX9, and BRCA1 mutations were common in high-grade rectal NECs/MiNENs. These genes helped in distinguishing poorly-differentiated or well-differentiated rectal NENs. Alterations in P53, Wnt and TGFß signaling pathways were more pronounced in rectal NECs and MiNENs. Alterations in Wnt, MAPK and PI3K/AKT signaling pathways promoted metastases. Rectal NENs were classified into two molecular subtypes by cluster analysis based on the mutant genes and signaling pathways combined with clinicopathological features. Patients with mutations in the LRP2, DAXX, and PKN1 gene showed a trend of well-differentiated and early-stage tumors with less metastasis (p = 0.000). CONCLUSIONS: This study evaluated risk factors for regional lymphatic and/or distant metastases, identified high-frequency mutated genes, mutation signatures, altered signaling pathways through NGS. Rectal NENs were divided into two molecular types. This helps to evaluate the likelihood of metastasis, formulate follow-up strategies for patients and provide a target for future research on precision treatment of rectal NENs. PARP inhibitors, MEK inhibitors, mTOR/AKT/PI3K and Wnt signaling pathway inhibitors may be effective drugs for the treatment of metastatic rectal NENs.

Evaluation of the histopathologic status of rectal adenocarcinoma and its regional lymph nodes after neoadjuvant therapy, and its relation to the duration of disease-free survival.

INTRODUCTION: Colorectal cancer is one of the most common malignant tumors and has a relatively poor prognosis. Lymph node involvement is considered the most important prognostic factor. MATERIALS AND METHODS: During a retrospective cohort study, 132 patients with locally advanced rectal cancer who underwent neoadjuvant chemoradiotherapy followed by surgery for resectable rectal cancer from 2010 to 2015 in Sina hospital were reviewed. RESULTS: Multivariable analysis was performed and shown the clinical stage was not a representative factor for disease-free survival (P = 0.187), but Dworak Tumor Regression Grading were significantly associated with higher disease-free survival (P = 0.000) in stage II and stage III. The total number of retrieved lymph nodes and involved lymph nodes in the same clinical stage were statistically associated with higher mean disease-free survival in patients (P = 0.000 in both conditions). CONCLUSION: In the same clinical stage, increasing the Dworak Tumor Regression Grading reduced the risk of rectal cancer recurrence. Increasing total number of retrieved lymph nodes and involved lymph nodes, 2.14 times and 3.87 times increased the risk of recurrence, respectively.

Development and validation of a novel classification scheme for combining pathological T stage and log odds of positive lymph nodes for colon cancer.

AIM: Log Odds of Positive Lymph Nodes (LODDS) have a better predictive ability than N stage for colon cancer. However, the prognostic value of developing a novel prognostic classification by combining T stage and LODDS (TLODDS) for colon cancer remains unknown. Therefore, in the present study, we aimed to develop a TLODDS classification for colon cancer, and assess whether or not the novel TLODDS classification could improve survival stratification by comparing its discrimination, model-fitting, and net benefits, with the American Joint Committee on Cancer (AJCC) Tumor/Node/Metastasis (TNM) classification. METHODS: 45,558 Western colon cancers were identified in the Surveillance, Epidemiology, and End Results database as a training set. A novel LODDS stage was established and patients with similar survival rates were grouped by combining T and LODDS stages to develop a novel TLODDS classification. The TLODDS classification was further assessed in a Chinese validation set of 3,515 colon cancers and an application set of 3,053 rectal cancers. RESULTS: We developed a novel TLODDS classification that incorporated 7 stages: stage I (T1LODDS1), IIA (T2LODDS1, T1LODDS2, T1LODDS3), IIB (T2LODDS2-3, T3LODDS1, T1LODDS4), IIC (T3LODDS2, T2LODDS4, T4aLODDS1), IIIA (T3LODDS3, T1-2LODDS5, T4bLODDS1, T4aLODDS2), IIIB (T3LODDS4-5, T4aLODDS3-4, T4bLODDS2) and IIIC (T4bLODDS3-5, T4aLODDS5). In the training set, it showed significantly better discrimination (area under the receiver operating characteristic (ROC) curve, 0.691 vs. 0.664, P < 0.001), better model-fitting (Akaike information criteria, 265,644 vs. 267,410), and superior net benefits, than the latest AJCC TNM classification. The predictive performance of the TLODDS classification was further validated in colon cancers and was successfully applied in rectal cancers with regards to both overall and disease-free survival. CONCLUSIONS: The TLODDS classification has better discriminatory ability, model-fitting, and net benefits than the existing TNM classification, and represents an alternative to the current TNM classifications for colon and rectal cancers.

Comparison of model fit and discriminatory ability of M category as defined by the 7th and 8th editions of the tumor-node-metastasis classification of colorectal cancer and the 9th edition of the Japanese classification.

BACKGROUND: In transitioning from the 7th edition of the tumor-node-metastasis classification (TNM-7) to the 8th edition (TNM-8), colorectal cancer with peritoneal metastasis was newly categorized as M1c. In the 9th edition of the Japanese Classification of colorectal, appendiceal, and anal carcinoma (JPC-9), M1c is further subdivided into M1c1 (without other organ involvement) and M1c2 (with other organ involvement). This study aimed to compare the model fit and discriminatory ability of the M category of these three classification systems, as no study to date has made this comparison. METHODS: The study population consisted of stage IV colorectal cancer patients who were referred to the National Cancer Center Hospital from 2000 to 2017. The Akaike information criterion (AIC), Harrell's concordance index (C-index), and time-dependent receiver operating characteristic (ROC) curves were used to compare the three classification systems. Subgroup analyses, stratified by initial treatment year, were also performed. RESULTS: According to TNM-8, 670 (55%) patients had M1a, 273 (22%) had M1b, and 279 (23%) had M1c (87 M1c1 and 192 M1c2 using JPC-9) tumors. Among the three classification systems, JPC-9 had the lowest AIC value (JPC-9: 10546.3; TNM-7: 10555.9; TNM-8: 10585.5), highest C-index (JPC-9: 0.608; TNM-7: 0.598; TNM-8: 0.599), and superior time-dependent ROC curves throughout the observation period. Subgroup analyses were consistent with these results. CONCLUSIONS: While the revised M category definition did not improve model fit and discriminatory ability from TNM-7 to TNM-8, further subdivision of M1c in JPC-9 improved these parameters. These results support further revisions to M1 subcategories in future editions of the TNM classification system.

Interobserver variation in the classification of tumor deposits in rectal cancer-is the use of histopathological characteristics the way to go?

The focus on lymph node metastases (LNM) as the most important prognostic marker in colorectal cancer (CRC) has been challenged by the finding that other types of locoregional spread, including tumor deposits (TDs), extramural venous invasion (EMVI), and perineural invasion (PNI), also have significant impact. However, there are concerns about interobserver variation when differentiating between these features. Therefore, this study analyzed interobserver agreement between pathologists when assessing routine tumor nodules based on TNM 8. Electronic slides of 50 tumor nodules that were not treated with neoadjuvant therapy were reviewed by 8 gastrointestinal pathologists. They were asked to classify each nodule as TD, LNM, EMVI, or PNI, and to list which histological discriminatory features were present. There was overall agreement of 73.5% (κ 0.38, 95%-CI 0.33-0.43) if a nodal versus non-nodal classification was used, and 52.2% (κ 0.27, 95%-CI 0.23-0.31) if EMVI and PNI were classified separately. The interobserver agreement varied significantly between discriminatory features from κ 0.64 (95%-CI 0.58-0.70) for roundness to κ 0.26 (95%-CI 0.12-0.41) for a lone arteriole sign, and the presence of discriminatory features did not always correlate with the final classification. Since extranodal pathways of spread are prognostically relevant, classification of tumor nodules is important. There is currently no evidence for the prognostic relevance of the origin of TD, and although some histopathological characteristics showed good interobserver agreement, these are often non-specific. To optimize interobserver agreement, we recommend a binary classification of nodal versus extranodal tumor nodules which is based on prognostic evidence and yields good overall agreement.

A signature predicting relapse based on integrated analysis on relapse-associated alternative mRNA splicing in I-III rectal cancer.

Researches focusing on the effects of alternative splicing (AS) on relapse of rectal cancer is little and signature based on the AS is blank. In this study, bioinformatic analysis was performed to identify and analyze the relapse-associated ASs, a signature was also constructed. In conclusion, 829 relapse-associated ASs of 676 mRNA were identified. 603 proteins with 2119 interactions were involved in the PPI (protein-protein interactions) network. 43 relapse-associated ASs and 64 SFs (splicing factors) with 160 interactions were indicated. Finally, we built a robust signature to predict the relapse of I-III rectal cancer with a high AUC (0.98) of ROC at 1 year. Based on the ASs involved in the signature, 4 molecular subgroups that could distinguish the relapse rate in diverse groups were identified. Our research provided an overview of relapse-associated ASs in I-III rectal cancer.

A proposal of an updated classification for pelvic relapses of rectal cancer to guide surgical decision-making.

BACKGROUND AND OBJECTIVES: Selection of patients affected by pelvic recurrence of rectal cancer (PRRC) who are likely to achieve a R0 resection is mandatory. The aim of this study was to propose a classification for PRRC to predict both radical surgery and disease-free survival (DFS). METHODS: PRRC patients treated at the National Cancer Institute of Milan (Italy) were included in the study. PRRC were classified as S1, if located centrally (S1a-S1b) or anteriorly (S1c) within the pelvis; S2, in case of sacral involvement below (S2a) or above (S2b) the second sacral vertebra; S3, in case of lateral pelvic involvement. RESULTS: Of 280 reviewed PRRC patients, 152 (54.3%) were evaluated for curative surgery. The strongest predictor of R+ resection was the S3 category (OR, 6.37; P = .011). Abdominosacral resection (P = .012), anterior exenteration (P = .012) and extended rectal re-excision (P = .003) were predictive of R0 resection. S3 category was highly predictive of poor DFS (HR 2.53; P = .038). DFS was significantly improved after R0 surgery for S1 (P < .0001) and S2 (P = .015) patients but not for S3 cases (P = .525). CONCLUSIONS: The proposed classification allows selection of subjects candidates to curative surgery, emphasizing that lateral pelvic involvement is the main predictor of R+ resection and independently affects the DFS.

Verification of the Japanese staging system for rectal cancer, focusing on differences with the TNM classification.

PURPOSE: The 9th Japanese Classification of Colorectal Cancer (9th JSCCR) has two main differences from the TNM classification (8th AJCC): first, main or lateral lymph node metastasis is classified as jN3; second, tumor nodules (ND) are treated as lymph node metastasis. In this study, we verified the 9th JSCCR for rectal cancer, focusing on the differences with the 8th AJCC. METHODS: This retrospective analysis involved 212 patients with stage I-III rectal cancer. ND was evaluated using whole-mount sections. We evaluated the relapse-free survival of each staging system, and compared the prognostic significance of the different staging systems using the Akaike information criterion (AIC) and Harrell's concordance index (c-index). RESULTS: Main or lateral lymph node metastasis was detected in nine of 212 (4%) patients. ND was detected in 79 of 212 (37%) patients. The best risk stratification power was observed in the 9th JSCCR (AIC, 759; c-index, 0.708) compared with the 7th JSCCR (AIC, 771; c-index, 0.681), 8th JSCCR (AIC, 768; c-index, 0.696), and the 8th AJCC (AIC, 766; c-index, 0.691). CONCLUSIONS: The 9th JSCCR, which includes the concepts of jN3 and ND, is useful for the risk stratification of rectal cancer, and the contributes to precise decision-making for follow-up management and adjuvant therapy.

Decision tree algorithm in locally advanced rectal cancer: an example of over-interpretation and misuse of a machine learning approach.

PURPOSE: To analyse the classification performances of a decision tree method applied to predictor variables in survival outcome in patients with locally advanced rectal cancer (LARC). The aim was to offer a critical analysis to better apply tree-based approach in clinical practice and improve its interpretation. MATERIALS AND METHODS: Data concerning patients with histological proven LARC between 2007 and 2014 were reviewed. All patients were treated with trimodality approach with a curative intent. The Kaplan-Meier method was used to estimate overall survival (OS). Decision tree methods were was used to select important variables in outcome prediction. RESULTS: A total of 100 patients were included. The 5-year and 7-year OS rates were 76.4% and 71.3%, respectively. Age, co-morbidities, tumor size, clinical tumor classification (cT) and clinical nodes classification (cN) were the important predictor variables to the tree's construction. Overall, 13 distinct groups of patients were defined. Patients aged < 65 years with cT3 disease and elderly patients with a tumor size < 5 cm seemed to have highest rates of survival. But the process over-fitted the data, leading to poor algorithm performance. CONCLUSION: We proposed a decision tree algorithm to identify known and new pre-treatment clinical predictors of survival in LARC. Our analysis confirmed that tree-based machine learning method, especially classification trees, can be easily interpreted even by a non-expert in the field, but controlling cross validation errors is mandatory to capture its statistical power. However, it is necessary to carefully analyze the classification error trend to chose the important predictor variables, especially in little data. Machine learning approach should be considered the new unexplored frontier in LARC. Based on big datasets, decision trees represent an opportunity to improve decision-making process in clinical practice.

Endorectal ultrasound and magnetic resonance imaging for staging of early rectal cancers: how well does it work in practice?

BACKGROUND: Rectal tumor treatment strategies are individually tailored based on tumor stage, and yield different rates of posttreatment morbidity, mortality, and local recurrence. Therefore, the accuracy of pretreatment staging is highly important. Here we investigated the accuracy of staging by magnetic resonance imaging (MRI) and endorectal ultrasound (ERUS) in a clinical setting. MATERIAL AND METHODS: A total of 500 patients were examined at the rectal cancer outpatient clinic at Haukeland University Hospital between October 2014 and January 2018. This study included only cases in which the resection specimen had a histopathological staging of adenoma or early rectal cancer (pT1-pT2). Patients with previous pelvic surgery or preoperative radiotherapy were excluded. The 145 analyzed patients were preoperatively examined via biopsy (n = 132), digital rectal examination (n = 77), rigid rectoscopy (n = 127), ERUS (n = 104), real-time elastography (n = 96), and MRI (n = 84). RESULTS: ERUS distinguished between adenomas and early rectal cancer with 88% accuracy (95% CI: 0.68-0.96), while MRI achieved 75% accuracy (95% CI: 0.54-0.88). ERUS tended to overstage T1 tumors as T2-T3 (16/24). MRI overstaged most adenomas to T1-T2 tumors (18/22). Neither ERUS nor MRI distinguished between T1 and T2 tumors. CONCLUSIONS: In a clinical setting, ERUS differentiated between benign and malignant tumors with high accuracy. The present findings support previous reports that ERUS and MRI have low accuracy for T-staging of early rectal cancer. We recommend that MRI be routinely combined with ERUS for the clinical examination of rectal tumors, since MRI consistently overstaged adenomas as cancer. In adenomas, MRI had no additional benefit for preoperative staging.

[Clasificación molecular del carcinoma de colon y recto. Una revisión corta].

Traditionally, carcinoma classifications have been based on clinical or pathological features. However, with the development of molecular biology in recent decades, more tumors are increasingly being genetically studied and, in several of them, molecular classifications have been created (the most widely studied and used is that for breast cancer). Colon and rectum cancer are no exception. In this short review, the evolution of colon and rectum cancer molecular classification is explained and the consensus conclusions on the subject are addressed.

Tradicionalmente las clasificaciones de los carcinomas se han basado en características clínicas o patológicas. Sin embargo, en las últimas décadas, con el desarrollo de la biología molecular, cada vez más tumores se están estudiando genéticamente y en varios se han creado clasificaciones moleculares (la más estudiada y utilizada es la de cáncer de mama). El cáncer de colon y recto no es la excepción. En esta revisión corta se explica la evolución de la clasificación molecular del cáncer de colon y recto y se abordan los conclusiones consensuadas al respecto.

A meta-analysis assessing the survival implications of subclassifying T3 rectal tumours.

AIM: Although T3 tumour subclassifications have been linked to prognosis, its mandatory adoption in histopathological reports has not been incorporated. This article focusses on the survival outcomes in patients with T3 rectal cancer according to extramural spread beyond the muscularis propria. METHODS: A systematic review of all studies up to January 2016, without language restriction, was identified from MEDLINE, Cochrane Controlled Trials Register (1960-2016) and Embase (1991-2016). All studies reporting on survival and T3 tumours with a defined cut-off of 5 mm ± 1 mm tumour invasion beyond the muscularis propria for rectal cancers were included. Hazard ratios were extracted directly from the studies or from survival curves using the technique described by Parmar. Quality assessment was performed using the Newcastle-Ottawa scale. RESULTS: Tumours with invasion more than 5 ± 1 mm from the muscularis propria had statistically significantly worse overall survival (natural log of the hazard ratio [lnHR]: 1.40 [1.06, 2.04], p < 0.001) and there was no statistically significant heterogeneity (χ2 = 1.541, df = 3, p = 0.673, I2 = 0). There was statistically significantly worse disease-free survival in more invasive tumours (lnHR: 1.49 [1.19, 2.00], p < 0.001) and cancer specific survival (lnHR: 1.22 [0.917, 1.838], p < 0.001). Overall survival in patients who had preoperative therapy was higher in patients with less invasion beyond the muscularis propria [p < 0.01]. CONCLUSIONS: Subclassifying all T3 rectal tumours according to the depth of spread with a cut-off of 5±1 mm beyond the muscularis propria is prognostically relevant for overall survival, disease-free survival and cancer-specific survival irrespective of the nodal status; therefore, subclassifying T3 tumours should be a reporting requirement in histopathology reports.

The role of imaging and biopsy in the management and staging of large non-pedunculated rectal polyps.

INTRODUCTION: Endoscopic mucosal resection (EMR) and endoscopic submucosal dissection (ESD) are often used for benign and Sm1 large non-pedunculated rectal polyps (LNPRPs), although other surgical techniques including transanal endoscopic microsurgery (TEMS) and transanal minimal invasive surgery remain available. This review covers the role of pre-excisional imaging and selective biopsy of LNPRPs. Areas covered: Polyps between 2 and 3 cm with favorable features (Paris 1, Kudo III/IV pit patterns, and non-lateral spreading type [LST]) may have a one-stage EMR without biopsy and imaging, provided adequate expertise is available with other technologies such as magnifying chromoendoscopy. Higher-risk polyps (moderate/severe dysplasia, 0-IIa+c morphology, nongranular LST, Kudo pit pattern V or submucosal carcinoma, or those >3 cm) should have pre-EMR/ESD imaging with magnetic resonance imaging (MRI) and/or endorectal ultrasound (ERUS) ± biopsies and photographs prior to multidisciplinary team discussion. Expert commentary: In some centers, EMR and ESD are considered the primary modality of treatment, with TEMS as a back-up, while elsewhere, TEMS is the main modality for excision of significant polyps and early colorectal cancer lesions. Likewise, the exact roles of ERUS and MRI will depend on availability of local expertise, although it is suggested that the techniques are complementary.

Tumor Regression Grade After Neoadjuvant Chemoradiation and Surgery for Low Rectal Cancer Evaluated by Multiple Correspondence Analysis: Ten Years as Minimum Follow-up.

BACKGROUND: The role of Mandard's tumor regression grade (TRG) classification is still controversial in defining the prognostic role of patients who have undergone neoadjuvant chemoradiation (CRT) and total mesorectal excision. The present study evaluated multiple correspondence analysis (MCA) as a tool to better cluster variables, including TRG, for a homogeneous prognosis. PATIENTS AND METHODS: A total of 174 patients with a minimum follow-up period of 10 years were stratified into 2 groups: group A (TRG 1-3) and group B (TRG 4-5) using Mandard's classification. Overall survival and disease-free survival were analyzed using univariate and multivariate analysis. Subsequently, MCA was used to analyze TRG plus the other prognostic variables. RESULTS: The overall response to CRT was 55.7%, including 13.2% with a pathologic complete response. TRG group A correlated strictly with pN status (P = .0001) and had better overall and disease-free survival than group B (85.1% and 75.6% vs. 71.1% and 67.3%; P = .06 and P = .04, respectively). The TRG 3 subset (about one third of our series) showed prognostically heterogeneous behavior. In addition to multivariate analysis, MCA separated TRG 1 and TRG 2 versus TRG 4 and TRG 5 well and also allocated TRG 3 patients close to the unfavorable prognostic variables. CONCLUSION: TRG classification should be used in all pathologic reports after neoadjuvant CRT and radical surgery to enrich the prognostic profile of patients with an intermediate risk of relapse and to identify patients eligible for more conservative treatment. Thus, MCA could provide added value.

Radiotherapy for Patients With Resected Tumor Deposit-Positive Colorectal Cancer: A Surveillance, Epidemiology, and End Results-Based Population Study.

CONTEXT: - According to the American Joint Committee on Cancer's Cancer Staging Manual, 7th edition, TNM classification, tumor deposit (TD)-positive colorectal cancers (CRCs) are classified as N1c. The effects of radiotherapy and the effects of the updated American Joint Committee on Cancer 7th edition TNM N1c classification for patients with TD-positive CRC are unclear. OBJECTIVE: - To investigate outcomes of radiotherapy in patients with resected TD-positive CRC. DESIGN: - Resected TD-positive CRCs diagnosed from 2010 to 2014 were identified in the Surveillance, Epidemiology, and End Results 18 database. Factors associated with overall survival (OS) and cancer-specific survival (CSS) were investigated using Kaplan-Meier and Cox proportional hazards models. RESULTS: - We included 2712 qualified CRC patients, who either underwent adjuvant radiotherapy (n = 187; 6.9%) or received no radiotherapy (n = 2525; 93.1%). Univariate Cox proportional models showed improved CSS among all CRC patients who underwent adjuvant radiotherapy (CSS hazard ratio, 0.73; 95% CI, 0.57-0.95) and among rectal cancer patients when separated by location (hazard ratio, 0.57; 95% CI, 0.40-0.83), although these associations were attenuated in multivariable-adjusted models. There was improved OS among rectal cancer patients (hazard ratio, 0.77; 95% CI, 0.59-0.99). In subgroup analyses, radiotherapy was not associated with OS or CSS in either metastatic or nonmetastatic CRC patients. Instead, N1c category (versus N0) was associated with a worse OS (hazard ratio, 1.43; 95% CI, 1.31-1.57) but was not associated with CSS. CONCLUSIONS: - Radiotherapy did not independently improve OS among TD-positive CRC patients. In this study, classifying TD positivity as N1c was associated with worse OS than classifying TD positivity as N0. The findings seem to challenge the benefits of radiotherapy and the new N1c classification of TD for TD-positive CRC patients.

Prediction of pathological response to neoadjuvant treatment in rectal cancer with a two-protein immunohistochemical score derived from stromal gene-profiling.

BACKGROUND: Preoperative chemoradiotherapy followed by surgical mesorectal resection is the standard of care for locally advanced rectal carcinomas. Yet, predicting that patients will respond to treatment remains an unmet clinical challenge. EXPERIMENTAL DESIGN: Using laser-capture microdissection we isolated RNA from stroma and tumour glands from prospective pre-treatment samples (n = 15). Transcriptomic profiles were obtained hybridising PrimeView Affymetrix arrays. We modelled a carcinoma-associated fibroblast-specific genes filtering data using GSE39396. RESULTS: The analysis of differentially expressed genes of stroma/tumour glands from responder and non-responder patients shows that most changes were associated with the stromal compartment; codifying mainly for extracellular matrix and ribosomal components. We built a carcinoma-associated fibroblast (CAF) specific classifier with genes showing changes in expression according to the tumour regression grade (FN1, COL3A1, COL1A1, MMP2 and IGFBP5). We assessed these five genes at the protein level by means of immunohistochemical staining in a patient's cohort (n = 38). For predictive purposes we used a leave-one-out cross-validated model with a positive predictive value (PPV) of 83.3%. Random Forest identified FN1 and COL3A1 as the best predictors. Rebuilding the leave-one-out cross-validated regression model improved the classification performance with a PPV of 93.3%. An independent cohort was used for classifier validation (n = 36), achieving a PPV of 88.2%. In a multivariate analysis, the two-protein classifier proved to be the only independent predictor of response. CONCLUSION: We developed a two-protein immunohistochemical classifier that performs well at predicting the non-response to neoadjuvant treatment in rectal cancer.