Signature of microsatellite instability, KRAS and BRAF gene mutations in German patients with locally advanced rectal adenocarcinoma before and after neoadjuvant 5-FU radiochemotherapy

Comparative Efficacy of Magnetic Resonance Cholangiopancreatography vs. Percutaneous Transhepatic Cholangiography With Percutaneous Transhepatic Biliary Drainage Stenting in Evaluating Obstructive Jaundice: A Prospective Study in South India

Introduction Obstructive jaundice due to proximal biliary obstruction presents significant diagnostic and therapeutic challenges. Accurate and timely diagnosis is essential for effective management. Objective/aim This study aimed to evaluate and compare the diagnostic accuracy of magnetic resonance cholangiopancreatography (MRCP) and percutaneous transhepatic cholangiography (PTC) along with percutaneous transhepatic biliary drainage (PTBD) stenting in obstructive jaundice, while also incorporating the comparison of ultrasonography (USG) and computed tomography (CT) findings. Materials and methods A prospective study was conducted at a tertiary healthcare center in South India from January 2020 to June 2022. Comprehensive diagnostic evaluations were performed using USG, contrast-enhanced computed tomography (CECT), MRCP, and PTC. The diagnostic outcomes from USG and CECT were initially assessed, followed by MRCP for every patient. These results were then compared with PTC, focusing on identifying the causes and levels of biliary obstruction. Results Fifty patients with suspected obstructive jaundice were included in the study. The study predominantly involved patients aged between the fourth and eighth decades (80%). Choledocholithiasis was identified as the leading cause (30%). MRCP demonstrated superior sensitivity in identifying both the cause (80%) and level (88%) of obstruction. It was particularly effective in detecting hilar masses with 100% sensitivity. Conversely, PTC, while less sensitive in detection, offered the advantage of simultaneous therapeutic intervention through stenting, with a sensitivity rate of 93% in detecting hilar masses. Conclusion MRCP outperforms PTC in diagnostic sensitivity for obstructive jaundice caused by proximal biliary obstruction. However, the advantage of PTC lies in its capacity for immediate therapeutic intervention via stent placement, addressing both diagnostic and treatment needs.

Radiomics Analysis of Multi-Sequence MR Images For Predicting Microsatellite Instability Status Preoperatively in Rectal Cancer

Background

Immunotherapy, adjuvant chemotherapy, and prognosis of colorectal cancer are associated with MSI. Biopsy pathology cannot fully reflect the MSI status and heterogeneity of rectal cancer.

Purpose

To develop a radiomic-based model to preoperatively predict MSI status in rectal cancer on MRI.

Assessment

The patients were divided into two cohorts (training and testing) at a 7:3 ratio. Radiomics features, including intensity, texture, and shape, were extracted from the segmented volumes of interest based on T2-weighted and ADC imaging.

Statistical Tests

Independent sample t test, Mann-Whitney test, the chi-squared test, Receiver operating characteristic curves, calibration curves, decision curve analysis and multi-variate logistic regression analysis

Results

The radiomics models were significantly associated with MSI status. The T2-based model showed an area under the curve of 0.870 with 95% CI: 0.794–0.945 (accuracy, 0.845; specificity, 0.714; sensitivity, 0.976) in training set and 0.895 with 95% CI, 0.777–1.000 (accuracy, 0.778; specificity, 0.887; sensitivity, 0.772) in testing set. The ADC-based model had an AUC of 0.790 with 95% CI: 0.794–0.945 (accuracy, 0.774; specificity, 0.714; sensitivity, 0.976) in training set and 0.796 with 95% CI, 0.777–1.000 (accuracy, 0.778; specificity, 0.889; sensitivity, 0.772) in testing set. The combined model integrating T2 and ADC features showed an AUC of 0.908 with 95% CI: 0.845–0.971 (accuracy, 0.857; specificity, 0.762; sensitivity, 0.952) in training set and 0.926 with 95% CI: 0.813-1.000 (accuracy, 0.852; specificity, 1.000; sensitivity, 0.778) in testing set. Calibration curve showed that the combined score had a good calibration degree, and the decision curve demonstrated that the combined score was of benefit for clinical use.

Data Conclusion

Radiomics analysis of T2W and ADC images showed significant relevance in the prediction of microsatellite status, and the accuracy of combined model of ADC and T2W features was better than either alone.

Impact of microsatellite status on chemotherapy for colorectal cancer patients with KRAS or BRAF mutation

KRAS and BRAF mutations are frequently detected in cases of colorectal cancer (CRC). The microsatellite status of patients with CRC and mutated KRAS/BRAF is important when determining cancer therapy. In the present study, the microsatellite status and genetic polymorphisms of KRAS (codons 12 and 13) and BRAF (V600E) were characterized in CRC tissue. The mismatch repair activity and oncogenic potential of KRAS were assessed by immunoblots from two KRAS-mutated CRC cell lines, SW480 and HCT116, with different microsatellite statuses, following treatment with 5-fluorouracil (5-FU) and oxaliplatin. Of all the 205 patients with CRC enrolled in the present study, 31.2% (64 of 205) had a KRAS or BRAF mutation, and 79.7% (51 of 64) of these patients with a KRAS/BRAF mutation exhibited microsatellite stability (MSS), indicating that microsatellite status is correlated with KRAS/BRAF mutation (P=0.027). A higher proportion (39.0%, 41 of 105) of elderly patients (≥62.6 years) had mutated KRAS or BRAF than younger patients (<62.6 years; 23.0%, 23 of 100; P=0.013). In the subgroup of 154 patients with MSS, patients without the KRAS or BRAF mutation (n=110) had longer disease-specific survival rates (58.8±9.4%) than patients with KRAS or BRAF mutations (n=44; 50.6±11.0%; P=0.043). Cytoplasmic KRAS levels decreased whereas nuclear MutS protein homolog 2 (MSH2) levels increased slightly in CRC HCT116 cells that were microsatellite instable, following treatment with 76.9 µM 5-FU for 2 days. In microsatellite stable SW480 cells, MSH2 levels markedly increased in the nucleus following 150 µM oxaliplatin treatment for 3 days. However, no significant change was observed regarding KRAS distribution in these cells. The results of the present study suggest that it is important to identify patients with CRC who may benefit from adjuvant chemotherapy with 5-FU or oxaliplatin, particularly CRC patients with MSS and mutated KRAS or BRAF, who have poorer overall survival rates than patients with microsatellite instability. Knowledge of the microsatellite status of patients and whether they harbor KRAS or BRAF mutations may enable more effective therapeutic strategies to be developed. Further prospective studies are required to validate the findings of the current study.

Heterogeneity of KRAS Mutation Status in Rectal Cancer

INTRODUCTION

Anti-EGFR targeted therapy is of increasing importance in advanced colorectal cancer and prior KRAS mutation testing is mandatory for therapy. However, at which occasions this should be performed is still under debate. We aimed to assess in patients with locally advanced rectal cancer whether there is intra-specimen KRAS heterogeneity prior to and upon preoperative chemoradiotherapy (CRT), and if there are any changes in KRAS mutation status due to this intervention.

MATERIALS AND METHODS

KRAS mutation status analyses were performed in 199 tumor samples from 47 patients with rectal cancer. To evaluate the heterogeneity between different tumor areas within the same tumor prior to preoperative CRT, 114 biopsies from 34 patients (mean 3 biopsies per patient) were analyzed (pre-therapeutic intratumoral heterogeneity). For the assessment of heterogeneity after CRT residual tumor tissue (85 samples) from 12 patients (mean 4.2 tissue samples per patient) were analyzed (post-therapeutic intratumoral heterogeneity) and assessment of heterogeneity before and after CRT was evaluated in corresponding patient samples (interventional heterogeneity). Primer extension method (SNaPshot™) was used for initial KRAS mutation status testing for Codon 12, 13, 61, and 146. Discordant results by this method were reevaluated by using the FDA-approved KRAS Pyro Kit 24, V1 and the RAS Extension Pyro Kit 24, V1 Kit (therascreen® KRAS test).

RESULTS

For 20 (43%) out of the 47 patients, a KRAS mutation was detected. With 12 out of 20, the majority of these mutations affected codon 35. We did not obtained evidence that CRT results in changes of the KRAS mutation pattern. In addition, no intratumoral heterogeneity in the KRAS mutational status could be proven. This was true for both the biopsies prior to CRT and the resection specimens thereafter. The discrepancy observed in some samples when using the SNaPshot™ assay was due to insufficient sensitivity of this technique upon massive tumor regression by CRT as application of the therascreen® KRAS test revealed concordant results.

CONCLUSION

Our results indicate that the KRAS mutation status at the primary tumor site of rectal cancer is homogenous. Its assessment for therapeutic decisions is feasible in pre-therapeutic biopsies as well as in post-therapeutic resected specimens. The amount of viable tumor cells seems to be an important determinant for assay sensitivity and should thus be considered for selection of the analytical method.

Germline and somatic genetic predictors of pathological response in neoadjuvant settings of rectal and esophageal cancers: systematic review and meta-analysis

Oncologists have pointed out an urgent need for biomarkers that can be useful for clinical application to predict the susceptibility of patients to preoperative therapy. This review collects, evaluates and combines data on the influence of reported somatic and germline genetic variations on histological tumor regression in neoadjuvant settings of rectal and esophageal cancers. Five hundred and twenty-seven articles were identified, 204 retrieved and 61 studies included. Among 24 and 14 genetic markers reported for rectal and esophageal cancers, respectively, significant associations in meta-analyses were demonstrated for the following markers. In rectal cancer, major response was more frequent in carriers of the TYMS genotype 2 R/2 R-2 R/3 R (rs34743033), MTHFR genotype 677C/C (rs1801133), wild-type TP53 and KRAS genes. In esophageal cancer, successful therapy appeared to correlate with wild-type TP53. These results may be useful for future research directions to translate reported data into practical clinical use.