Personalising radiotherapy in locally advanced rectal cancer: can macrophages within the microenvironment predict response to radiotherapy?

Introduction: While neoadjuvant radiotherapy is the standard of care in locally invasive rectal carcinoma (LIRC), only half of patients show a response. A predictive test enabling better patient selection could avoid unneccessary radiation exposure to poor responders. Macrophages within the tumour immune microenvironment with tumoricidal M1 and tumour-protective M2 phenotypes could be modulating this response. This study investigated the possible predictive value of M1 and M2 subpopulations in identifying patients’ likely response to short-course preoperative radiotherapy. Method: Biopsy samples were taken from 29 patients with locally invasive rectal carcinoma before treatment with short course radiotherapy and surgical specimens obtained after resection following short-course preoperative radiotherapy. Dual-staining immunohistochemistry was performed with CD68 as macrophage marker, HLA-DR as M1 marker, and CD163 as M2 marker. Samples were scored for hot-and-random spots by Nuance software (version 3.0.2) and compared with patients’ outcome data. Tumour response was measured by assessment of reduction of tumour-cell density. Results: Samples revealing a low score for HLA-DR positive M1 macrophages exhibited a better response to short-course radiotherapy with up to 80% (median 80·38% [IQR 46·94–84·73]) reduction in the tumour cell density. On the other hand those with a high score exhibited a poor response with only up to 20% (20·26 [0–48·19]) reduction. The difference in response between the two groups was significant (p = 0·017). No such trends were observed for CD163+M2 macrophages. The ratio of HLA–DR+ to CD163+macrophages for biopsy and resection samples was significantly different showing a drop in the HLA-DR positive macrophages in the resection samples (p 0.024). The mean of the difference between the biopsy (median 2·53 [IQR 1.98 – 3.08]) and resection (1·38 [IQR 0.96 – 1.8]) was 1·15 (p = 0·024). Conclusion: Patients with a variable macrophage phenotype composition within biopsy samples from patients with locally invasive rectal carcinoma respond differently to short-course preoperative radiotherapy. Further investigation involving a panel of macrophage and other immune-cell markers could verify and validate these findings and develop them as predictive tests identifying good responders to radiotherapy in patients with locally invasive rectal carcinoma

Differential and longitudinal immune gene patterns associated with reprogrammed microenvironment and viral mimicry in response to neoadjuvant radiotherapy in rectal cancer

Background Rectal cancers show a highly varied response to neoadjuvant radiotherapy/chemoradiation (RT/CRT) and the impact of the tumor immune microenvironment on this response is poorly understood. Current clinical tumor regression grading systems attempt to measure radiotherapy response but are subject to interobserver variation. An unbiased and unique histopathological quantification method (change in tumor cell density (ΔTCD)) may improve classification of RT/CRT response. Furthermore, immune gene expression profiling (GEP) may identify differences in expression levels of genes relevant to different radiotherapy responses: (1) at baseline between poor and good responders, and (2) longitudinally from preradiotherapy to postradiotherapy samples. Overall, this may inform novel therapeutic RT/CRT combination strategies in rectal cancer. Methods We generated GEPs for 53 patients from biopsies taken prior to preoperative radiotherapy. TCD was used to assess rectal tumor response to neoadjuvant RT/CRT and ΔTCD was subjected to k-means clustering to classify patients into different response categories. Differential gene expression analysis was performed using statistical analysis of microarrays, pathway enrichment analysis and immune cell type analysis using single sample gene set enrichment analysis. Immunohistochemistry was performed to validate specific results. The results were validated using 220 pretreatment samples from publicly available datasets at metalevel of pathway and survival analyses. Results ΔTCD scores ranged from 12.4% to −47.7% and stratified patients into three response categories. At baseline, 40 genes were significantly upregulated in poor (n=12) versus good responders (n=21), including myeloid and stromal cell genes. Of several pathways showing significant enrichment at baseline in poor responders, epithelial to mesenchymal transition, coagulation, complement activation and apical junction pathways were validated in external cohorts. Unlike poor responders, good responders showed longitudinal (preradiotherapy vs postradiotherapy samples) upregulation of 198 immune genes, reflecting an increased T-cell-inflamed GEP, type-I interferon and macrophage populations. Longitudinal pathway analysis suggested viral-like pathogen responses occurred in post-treatment resected samples compared with pretreatment biopsies in good responders. Conclusion This study suggests potentially druggable immune targets in poor responders at baseline and indicates that tumors with a good RT/CRT response reprogrammed from immune “cold” towards an immunologically “hot” phenotype on treatment with radiotherapy

Heterogeneity in colorectal cancer incidence among people recommended 3-yearly surveillance post-polypectomy: a validation study

Background Colonoscopy surveillance is recommended for patients at increased risk of colorectal cancer (CRC) following adenoma removal. Low-, intermediate-, and high-risk groups are defined by baseline adenoma characteristics. We previously evaluated surveillance in intermediate-risk patients using UK hospital data, identifying a higher-risk subgroup who benefitted from surveillance and a lower-risk subgroup who may not require surveillance. Here we explored whether these findings apply in individuals undergoing CRC screening. Methods Retrospective study using data from the UK Flexible Sigmoidoscopy Screening Trial (UKFSST), English CRC screening pilot (ECP), and US Kaiser Permanente CRC prevention programme (KPCP). Screening participants aged 50–74 years and classed as intermediate-risk at baseline colonoscopy were included. CRC data were available through 2006 (KPCP) or 2014 (UKFSST, ECP). We classified participants into lower- and higher-risk subgroups using our previously identified baseline risk factors; higher-risk participants were those with incomplete colonoscopies, poor bowel preparation, adenomas ≥20mm or with high-grade dysplasia, or proximal polyps. We compared CRC incidence rates in these subgroups and in the presence versus absence of surveillance using Cox regression. Results Of 2291 intermediate-risk participants, 45% were classified as higher-risk. Median follow-up was 11.8 years. CRC incidence rates were significantly higher in the higher-risk than lower-risk subgroup (hazard ratio [HR]=2.08, 95%CI 1.07–4.06). Surveillance reduced CRC incidence rates in higher-risk participants (HR=0.35, 0.14–0.86), but not statistically significantly so in lower-risk participants (HR=0.41, 0.12–1.38). Conclusion As previously demonstrated for hospital patients, screening participants classed as intermediate-risk comprise two risk subgroups. Surveillance clearly benefits the higher-risk subgroup

Q&A on diagnosis, screening and follow-up of colorectal neoplasia

The impressive and brisk evolution of medical science prevents many physicians from a thorough update on all the research fields. Colorectal cancer diagnosis, screening and follow-up is well known to require a multi-disciplinary approach, as it is faced by several specialties such as primary care physicians, gastroenterologists, non-gastroenterologist internists, radiologists and surgeons. To address this issue in a mutual perspective, we focused on the main points of the epidemiology, diagnosis, screening and follow-up of colorectal neoplasia by using a simple "Question & Answers" structure