The Effects of Neoadjuvant Chemoradiation in Locally Advanced Rectal Cancer-The Impact in Intratumoral Heterogeneity

Risks of Organ Preservation in Rectal Cancer: Data From Two International Registries on Rectal Cancer

PURPOSE

Organ preservation has become an attractive alternative to surgery (total mesorectal excision [TME]) among patients with rectal cancer after neoadjuvant therapy who achieve a clinical complete response (cCR). Nearly 30% of these patients will develop local regrowth (LR). Although salvage resection is frequently feasible, there may be an increased risk for development of subsequent distant metastases (DM). The aim of this study is to compare the risk of DM between patients with LR after Watch and Wait (WW) and patients with near-complete pathologic response (nPCR) managed by TME at the time of reassessment of response.

METHODS

Data from patients enrolled in the International Watch & Wait Database (IWWD) with cCR managed by WW and subsequent LR were compared with patients managed by TME (with ≤10% cancer cells-nPCR) from the Spanish Rectal Cancer Project (VIKINGO project). The primary end point was DM-free survival at 3 years from decision to WW or TME. The secondary end point was possible risk factors associated with DM.

RESULTS

Five hundred and eight patients with LR were compared with 893 patients with near-complete response after TME. Overall, DM rate was significantly higher among LRs (22.8% v 10.2%; P ≤ .001). Independent risk factors for DM included LR (v TME at reassessment; P = .001), ypT3-4 status (P = .016), and ypN+ status (P = .001) at the time of surgery. 3-year DM-free survival was significantly worse for patients with LR (75% v 87%; P = .001). When stratified for pathologic stage, patients with LR did significantly worse through all stages (P ≤ .009).

CONCLUSION

Patients with LR appear to have a higher risk for subsequent DM development than patients with nPCR managed by TME at restaging irrespective of final pathology. Leaving the primary undetectable tumor in situ until development of LR may result in worse oncologic outcomes.

The Landmark Series: Organ Preservation in Rectal Cancer-The Watch and Wait Strategy

Radical treatment of rectal cancer has evolved quite significantly over the last few decades with the development of optimal local disease staging with magnetic resonance (MR), refined surgical techniques including total mesorectal excision (TME) with or without sphincter-preservation, and multimodality treatment with the use of chemotherapy and radiation. While oncological outcomes have shown some significant improvements in terms of local disease control and distant metastases rates, complication rates and functional sequelae remain quite significant for patients undergoing TME surgery. In this setting, organ-preserving alternatives, including transanal local excision (TAE) and Watch and Wait (WW), have become increasingly attractive to patients in an attempt to avoid major surgery (TME) as an alternative treatment strategy with no oncological compromise. In the present narrative review, the fundamentals of selection and outcomes of patients undergoing WW will be covered to provide updated information for colorectal surgeons and surgical oncologists interested in this treatment alternative in clinical practice.

Association between cancer-associated fibroblasts and prognosis of neoadjuvant chemoradiotherapy in esophageal squamous cell carcinoma: a bioinformatics analysis based on single-cell RNA sequencing

BACKGROUND

Esophageal squamous cell carcinoma (ESCC) is a prevalent and aggressive subtype of esophageal cancer, posing a significant mortality and economic burden, especially in East and Southeast Asia. Current therapeutic strategies have limitations in improving patient survival, particularly regarding disease progression and resistance. This study aimed to investigate the impact of neoadjuvant chemoradiotherapy (NCRT) on the ESCC microenvironment.

METHODS

We utilized single-cell RNA sequencing to systematically characterize the tumor and cancer-associated fibroblasts (CAFs) subtypes. Marker genes of myofibroblastic CAFs (myCAFs) were employed to establish a prognostic model and verify its application in other datasets. Other experiments were conducted on clinical samples to explore potential ESCC risk-related genes.

RESULTS

Our bioinformatics and statistical analyses revealed an increased proportion of fibroblasts and epithelial cells in NCRT and identified the Ep_c1 subtype associated with a better prognosis. Further results indicated a complex communication network between Ep_c1 and myCAFs. The top 30 marker genes of myCAFs were used to construct a prognostic signature with a significant response to immunotherapy. Finally, experiments identified Complement C1s subcomponent (C1S), Decorin (DCN), and Neuroblastoma suppression of tumorigenicity 1 (NBL1) as potential ESCC risk-related genes.

CONCLUSION

Our findings highlight the dynamic alterations in the post-NCRT ESCC microenvironment and provide a foundation for the development of personalized treatment and immunotherapeutic approaches. Future studies are warranted to further validate these findings and explore their clinical implications.

Is clinical complete response as accurate as pathological complete response in patients with mid-low locally advanced rectal cancer?

PURPOSE

The standard treatment for locally advanced rectal cancer involves neoadjuvant chemoradiation followed by total mesorectal excision surgery. A subset of patients achieves pathologic complete response (pCR), representing the optimal treatment outcome. This study compares the long-term oncological outcomes of patients who achieved pCR with those who attained clinical complete response (cCR) after total neoadjuvant therapy, managed using a watch-and-wait approach.

METHODS

This study retrospectively evaluated patients with mid-low locally advanced rectal cancer who underwent neoadjuvant treatment from January 1, 2005, to May 1, 2023. The pCR and cCR groups were compared based on demographic, clinical, histopathological, and long-term survival outcomes.

RESULTS

The median follow-up times were 54 months (range, 7-83 months) for the cCR group (n=73), 96 months (range, 7-215 months) for the pCR group (n=63), and 72 months (range, 4-212 months) for the pathological incomplete clinical response (pICR) group (n=627). In the cCR group, 15 patients (20.5%) experienced local regrowth, and 5 (6.8%) developed distant metastasis (DM). The pCR group had no cases of local recurrence, but 3 patients (4.8%) developed DM. Among the pICR patients, 58 (9.2%) experienced local recurrence, and 92 (14.6%) had DM. Five-year disease-free survival rates were 90.0% for cCR, 92.0% for pCR, and 69.5% for pICR (P=0.022). Five-year overall survival rates were 93.1% for cCR, 92.0% for pCR, and 78.1% for pICR. There were no significant differences in outcomes between the cCR and pCR groups (P=0.810); however, the pICR group exhibited poorer outcomes (P=0.002).

CONCLUSIONS

This study shows no significant long-term oncological differences between patients who exhibited cCR and those who experienced pCR.

Progress in research of local regrowth after neoadjuvant therapy in rectal cancer

The issue of local regrowth after neoadjuvant therapy in rectal cancer patients has attracted significant clinical attention. Following preoperative chemoradiotherapy, the persistence or regrowth of local tumors presents a critical clinical challenge. Research into the mechanisms, potential risk factors, and management strategies for local tumor persistence or regrowth is underway. Existing studies suggest that neoadjuvant therapy can reduce the occurrence of local regrowth in rectal cancer, but prevention and management of local regrowth remain urgent clinical issues. Future research needs to further clarify the role of the tumor microenvironment in local regrowth, delve into the potential mechanisms of rectal cancer local regrowth, and develop more precise and personalized treatment strategies. In addition, in-depth research on minimal residual disease and development of imaging genomics technology provide new perspectives and possibilities for the management of "watch and wait" strategies. This article provides a summary of the current research on local regrowth in rectal cancer patients after neoadjuvant therapy and prospects for future research directions.

Progress in research of local regrowth after neoadjuvant therapy in rectal cancer

The issue of local regrowth after neoadjuvant therapy in rectal cancer patients has attracted significant clinical attention. Following preoperative chemoradiotherapy, the persistence or regrowth of local tumors presents a critical clinical challenge. Research into the mechanisms, potential risk factors, and management strategies for local tumor persistence or regrowth is underway. Existing studies suggest that neoadjuvant therapy can reduce the occurrence of local regrowth in rectal cancer, but prevention and management of local regrowth remain urgent clinical issues. Future research needs to further clarify the role of the tumor microenvironment in local regrowth, delve into the potential mechanisms of rectal cancer local regrowth, and develop more precise and personalized treatment strategies. In addition, in-depth research on minimal residual disease and development of imaging genomics technology provide new perspectives and possibilities for the management of "watch and wait" strategies. This article provides a summary of the current research on local regrowth in rectal cancer patients after neoadjuvant therapy and prospects for future research directions.

Oncological risks associated with the planned watch-and-wait strategy using total neoadjuvant treatment for rectal cancer: A narrative review

Overall survival benefit of total neoadjuvant treatment (TNT) remains unconfirmed. Thus, in our opinion, the main rationale for using TNT is a planned watch-and-wait (w&w) strategy to improve patients' long-term quality of life through organ preservation. The OPRA randomized trial, which examined a planned w&w strategy using TNT, showed a higher organ preservation rate but also a higher regrowth rate compared to studies on the opportunistic w&w strategy. Higher rates of complete clinical response with TNT did not improve disease-free survival compared to historical controls. Therefore, the gain in organ-sparing capability might not be balanced by the increased oncological risk. The ultimate local failure rate in the intention-to-treat analysis of the OPRA trial was 13% for induction chemotherapy and 16% for consolidation chemotherapy, which seems higher than expected compared to 8% in a meta-analysis of w&w studies or 12% after TNT and surgery in the PRODIGE-23 and RAPIDO trials, which enrolled patients with more advanced cancers than the OPRA trial. Other studies also suggest worse local control when surgery is delayed for radio-chemoresistant cancers. Our review questions the safety of the planned w&w strategy using TNT in unselected patients. To reduce the oncological risk while maintaining high organ preservation rates, we suggest that the planned w&w strategy using TNT requires a two-tier patient selection process: before treatment and after tumor response assessment at the midpoint of consolidation chemotherapy. These robust selections should identify patients who are unlikely to achieve organ preservation with TNT and would be better managed by preoperative chemoradiotherapy (without consolidation chemotherapy) and surgery, or by discontinuing consolidation chemotherapy and proceeding directly to surgery.

Genomic landscape of locally advanced rectal adenocarcinoma: Comparison between before and after neoadjuvant chemoradiation and effects of genetic biomarkers on clinical outcomes and tumor response

PURPOSE

To explore genomic biomarkers in rectal cancer by performing whole-exome sequencing.

MATERIALS AND METHODS

Pre-chemoradiation (CRT) biopsy and post-CRT surgical specimens were obtained from 27 patients undergoing neoadjuvant CRT followed by definitive resection. Exomes were sequenced to a mean coverage of 30×. Somatic single-nucleotide variants (SNVs) and insertions/deletions (indels) were identified. Tumor mutational burden was defined as the number of SNVs or indels. Mutational signatures were extracted and fitted to COSMIC reference signatures. Tumor heterogeneity was quantified with a mutant-allele tumor heterogeneity (MATH) score. Genetic biomarkers and frequently occurred copy number alterations (CNAs) were compared between pre- and post-CRT specimens. Their associations with tumor regression grade (TRG) and clinical outcomes were explored.

RESULTS

Top five mutated genes were APC, TP53, NF1, KRAS, and NOTCH1 for pre-CRT samples and APC, TP53, NF1, CREBBP, and ATM for post-CRT samples. Several gene mutations including RUNX1, EGFR, and TP53 in pre-CRT samples showed significant association with clinical outcomes, but not with TRG. However, no such association was found in post-CRT samples. Discordance of driver mutation status was found between pre- and post-CRT samples. In tumor mutational burden analysis, higher number of SNVs or indels was associated with worse treatment outcomes. Six single-base substitution (SBS) signatures identified were SBS1, SBS30, SBS29, SBS49, SBS3, and SBS44. The MATH score decreased after CRT on paired analysis. Less than half of CNAs frequent in post-CRT samples were present in pre-CRT samples.

CONCLUSION

Pre- and post-CRT samples showed different genomic landscape. Potential genetic biomarkers of pre-CRT samples found in the current analysis call for external validation.

Challenges presented by complete response to immune checkpoint blockade in patients with dMMR colorectal cancer: A case report

INTRODUCTION

Early clinical trials have demonstrated remarkable responses to immune checkpoint blockade (ICB) in patients with colorectal cancers with deficient mismatch repair (dMMR) mechanisms. The precise role immunotherapy will play in the treatment of these patients is undefined, with these agents likely to produce new challenges as well as opportunities.

PRESENTATION OF CASE

A 74-year-old patient was diagnosed with a locally advanced dMMR adenocarcinoma in the transverse colon with clinical suspicion of peritoneal metastases (cT4N2M1). The burden of disease was assessed as incurable, and a referral was made for palliative oncological treatment. After 5 months of treatment with pembrolizumab, a complete radiological response in the primary tumour was seen although there was still radiological suspicion of peritoneal and lymph node metastases. The patient underwent cytoreductive surgery and hyperthermic intraperitoneal chemotherapy but unfortunately died 6 weeks later due to complications. Final histology of the surgical specimen showed no evidence of residual disease (ypT0N0M0).

DISCUSSION

This case highlights the opportunities and challenges presented by the efficacy of ICB in dMMR colorectal cancer. These agents were able to cure a patient who had disseminated disease presumed to be incurable at the time of diagnosis. However, due to current limitations in determining the degree of response to ICB, this result could only be confirmed after major surgery, which ultimately led to the patient's death.

CONCLUSION

ICB can lead to dramatic responses in patients with dMMR colorectal cancers. Major challenges remain in differentiating complete and partial responders and determining the indications for conventional surgery.

Local tumor regrowth after clinical complete response following neoadjuvant therapy for rectal cancer: what happens when organ preservation falls short

Organ preservation strategies, especially watch and wait, after neoadjuvant treatment in locally advanced rectal cancer, have become topics that generate significant interest, for both patients and clinicians. The obvious advantage of these strategies is the avoidance of surgery with its associated risks and functional consequences. Over time, it has become evident that these strategies offer acceptable safety in oncological terms and, in most patients, allows preservation of the rectum without harming patients in terms of distant metastasis or survival. However, there is a small group of patients in whom the tumor returns after an initially diagnosed clinical complete response; patients with local tumor regrowth. The main threat in these patients is not simply local disease, which can be successfully managed in most cases, but the possible effects it may have on distant metastases. The pathophysiology of the phenomenon of local tumor regrowth is not well known and, therefore, strategies to minimize possible impact on survival are not well defined. Our aim is to review key issues in this subgroup that pose a substantial threat to the safety and viability of organ-preserving and watch-and-wait strategies. We also explore possible pathophysiologic explanations and future directions and perspectives that may improve both local and systemic disease control.

Comparative analysis of capture methods for genomic profiling of circulating tumor cells in colorectal cancer

The genomic profiling of circulating tumor cells (CTCs) in the bloodstream should provide clinically relevant information on therapeutic efficacy and help predict cancer survival. Here, we contrasted the genomic profiles of CTC pools recovered from metastatic colorectal cancer (mCRC) patients using different enrichment strategies (CellSearch, Parsortix, and FACS). Mutations inferred in the CTC pools differed depending on the enrichment strategy and, in all cases, represented a subset of the mutations detected in the matched primary tumor samples. However, the CTC pools from Parsortix, and in part, CellSearch, showed diversity estimates, mutational signatures, and drug-suitability scores remarkably close to those found in matching primary tumor samples. In addition, FACS CTC pools were enriched in apparent sequencing artifacts, leading to much higher genomic diversity estimates. Our results highlight the utility of CTCs to assess the genomic heterogeneity of individual tumors and help clinicians prioritize drugs in mCRC.

Correlative Significance of Tumor Regression Grade and ypT Category in Patients Undergoing Preoperative Chemoradiotherapy for Locally Advanced Rectal Cancer

BACKGROUND

In patients with locally advanced rectal cancer, the treatment response to preoperative chemoradiotherapy (PRCRT) varies, and the ypT stage may change as a result of tumor shrinkage. The purpose of this study was to evaluate the correlative significance and determine the prognostic value of tumor regression grade and ypT category staging systems.

MATERIALS AND METHODS

This retrospective observational study was conducted in a tertiary center. A total of 1240 patients with rectal cancer who underwent curative resection after PRCRT between January 2007 and December 2016 were consecutively included.

RESULTS

A significant association was found between the American Joint Committee on Cancer/College of American Pathology tumor regression grading system and ypT category, indicating a potential correlation between worse tumor regression grade and more advanced T stage (Cramer's V = 0.255, P < .001). The ypT stage and tumor regression grade were independent predictors of each other (P < .001). The good response group (tumor regression grades 0-1) had significantly higher 5-year disease-free survival (85.5% vs. 68.2%, P < .001) and overall survival (92.1% vs. 81.0%, P < .001) rates than the poor response group (tumor regression grades 2-3). However, the ypT and ypN categories were the most important independent prognostic factors for disease-free and overall survival.

CONCLUSIONS

Tumor regression grade and ypT category were significantly correlated. Although tumor regression grade alone is not definitive, it is closely related to the ypT stage and impacts oncologic outcomes. These findings should be taken into consideration when stratifying the prognosis of patients undergoing PRCRT.

MRI radiomics independent of clinical baseline characteristics and neoadjuvant treatment modalities predicts response to neoadjuvant therapy in rectal cancer

Background

To analyse the performance of multicentre pre-treatment MRI-based radiomics (MBR) signatures combined with clinical baseline characteristics and neoadjuvant treatment modalities to predict complete response to neoadjuvant (chemo)radiotherapy in locally advanced rectal cancer (LARC).

Methods

Baseline MRI and clinical characteristics with neoadjuvant treatment modalities at four centres were collected. Decision tree, support vector machine and five-fold cross-validation were applied for two non-imaging and three radiomics-based models’ development and validation.

Results

We finally included 674 patients. Pre-treatment CEA, T stage, and histologic grade were selected to generate two non-imaging models: C model (clinical baseline characteristics alone) and CT model (clinical baseline characteristics combining neoadjuvant treatment modalities). The prediction performance of both non-imaging models were poor. The MBR signatures comprising 30 selected radiomics features, the MBR signatures combining clinical baseline characteristics (CMBR), and the CMBR incorporating neoadjuvant treatment modalities (CTMBR) all showed good discrimination with mean AUCs of 0.7835, 0.7871 and 0.7916 in validation sets, respectively. The three radiomics-based models had insignificant discrimination in performance.

Conclusions

The performance of the radiomics-based models were superior to the non-imaging models. MBR signatures seemed to reflect LARC’s true nature more accurately than clinical parameters and helped identify patients who can undergo organ preservation strategies.

Sialyltransferase ST6GAL-1 mediates resistance to chemoradiation in rectal cancer

Locally advanced rectal cancer is typically treated with chemoradiotherapy followed by surgery. Most patients do not display a complete response to chemoradiotherapy, but resistance mechanisms are poorly understood. ST6GAL-1 is a sialyltransferase that adds the negatively charged sugar, sialic acid (Sia), to cell surface proteins in the Golgi, altering their function. We therefore hypothesized that ST6GAL-1 could mediate resistance to chemoradiation in rectal cancer by inhibiting apoptosis. Patient-derived xenograft and organoid models of rectal cancer and rectal cancer cell lines were assessed for ST6GAL-1 protein with and without chemoradiation treatment. ST6GAL-1 mRNA was assessed in untreated human rectal adenocarcinoma by PCR assays. Samples were further assessed by Western blotting, Caspase-Glo apoptosis assays, and colony formation assays. The presence of functional ST6GAL-1 was assessed via flow cytometry using the Sambucus nigra lectin, which specifically binds cell surface α2,6-linked Sia, and via lectin precipitation. In patient-derived xenograft models of rectal cancer, we found that ST6GAL-1 protein was increased after chemoradiation in a subset of samples. Rectal cancer cell lines demonstrated increased ST6GAL-1 protein and cell surface Sia after chemoradiation. ST6GAL-1 was also increased in rectal cancer organoids after treatment. ST6GAL-1 knockdown in rectal cancer cell lines resulted in increased apoptosis and decreased survival after treatment. We concluded that ST6GAL-1 promotes resistance to chemoradiotherapy by inhibiting apoptosis in rectal cancer cell lines. More research will be needed to further elucidate the importance and mechanism of ST6GAL-1-mediated resistance.

Assessing tumor heterogeneity: integrating tissue and circulating tumor DNA (ctDNA) analysis in the era of immuno-oncology - blood TMB is not the same as tissue TMB

Tissue tumor mutational burden (tTMB) is calculated to aid in cancer treatment selection. High tTMB predicts a favorable response to immunotherapy in patients with non-small cell lung cancer. Blood TMB (bTMB) from circulating tumor DNA is reported to have similar predictive power and has been proposed as an alternative to tTMB. Across many studies not only are tTMB and bTMB not concordant but also as reported previously by our group predict conflicting outcomes. This implies that bTMB is not a substitute for tTMB, but rather a composite index that may encompass tumor heterogeneity. Here, we provide a thorough overview of the predictive power of TMB, discuss the use of tumor heterogeneity alongside TMB to predict treatment response and review several methods of tumor heterogeneity assessment. Furthermore, we propose a hypothetical method of estimating tumor heterogeneity and touch on its clinical implications.

High-Risk Clinicopathological and Genetic Features and Outcomes in Patients Receiving Neoadjuvant Radiochemotherapy for Locally Advanced Rectal Cancer

Administering preoperative radiochemotherapy (RCT) in stage II-III tumors to locally advanced rectal carcinoma patients has proved to be effective in a high percentage of cases. Despite this, 20-30% of patients show no response or even disease progression. At present, preoperative response is assessed by a combination of imaging and tumor regression on histopathology, but recent studies suggest that various genetic abnormalities may be associated with the sensitivity or resistance of rectal cancer tumor cells to neoadjuvant therapy. In the present study we investigated the relationship between genetic lesions detected by high-density single-nucleotide polymorphisms (SNP) arrays 6.0 and response to neoadjuvant RCT, evaluated according to Dworak criteria in 39 rectal cancer tumors before treatment. The highest frequency of copy-number (CN) losses detected corresponded to chromosomes 18q (n = 27; 69%), 1p (n = 22; 56%), 15q (n = 19; 49%), 8p (n = 18; 48%), 4q (n = 17; 46%), and 22q (n = 17; 46%); in turn, CN gains more frequently involved chromosomes 20p (n = 22; 56%), 8p (n = 20; 51%), and 15q (n = 16; 41%). There was a significant association between alterations in the 1p, 3q, 7q, 12p, 17q, 20p, and 22q chromosomal regions and the degree of response to therapy prior to surgery. However, 4q, 15q11.1, and 15q14 chromosomal region alterations were identified as important by five prediction algorithms, i.e., those with the greatest influence on predicting the tumor response to treatment with preoperative RCT. Multivariate analysis of prognostic factors showed that gains on 15q11.1 and carcinoembryonic antigen (CEA) levels serum at diagnosis were the only independent variables predicting disease-free survival (DFS). Lymph node involvement also showed a prognostic impact on overall survival (OS) in the multivariate analysis. A deep-learning-based algorithm showed a 100% success rate in predicting both DFS and OS at 60 months after diagnosis of the disease. In summary, our results indicate the existence of an association between tumor genetic abnormalities at diagnosis, response to neoadjuvant therapy, and survival of patients with locally advanced rectal cancer. In addition to the clinical and biological characteristics of locally advanced rectal cancer patients, these could be used in the future as therapeutic and prognostic biomarkers, to identify patients sensitive or resistant to preoperative treatment, helping guide therapeutic decision-making. Additional prospective studies in larger series of patients are required to confirm the clinical utility of the newly identified biomarkers.

Treatment-induced evolutionary dynamics in nonmetastatic locally advanced rectal adenocarcinoma

Multi-modal treatment of non-metastatic locally advanced rectal adenocarcinoma (LARC) includes chemotherapy, radiation, and life-altering surgery. Although highly effective for local cancer control, metastatic failure remains significant and drives rectal cancer-related mortality. A consistent observation of this tri-modality treatment paradigm is that histologic response of the primary tumor to neoadjuvant treatment(s), which varies across patients, predicts overall oncologic outcome. In this chapter, we will examine this treatment response heterogeneity in the context of evolutionary dynamics. We hypothesize that improved understanding of eco-evolutionary pressures rendering small cancer cell populations vulnerable to extinction may influence treatment strategies and improve patient outcomes. Applying effective treatment(s) to cancer populations causes a "race to extinction." We explore principles of eco-evolutionary extinction in the context of these small cancer cell populations, evaluating how treatment(s) aim to eradicate the cancer populations to ultimately result in cure. In this chapter, we provide an evolutionary rationale for limiting continuous treatment(s) with the same agent or combination of agents to avoid selection of resistant cancer subpopulation phenotypes, allowing "evolutionary rescue." We draw upon evidence from nature demonstrating species extinction rarely occurring as a single event phenomenon, but rather a series of events in the slide to extinction. We posit that eradicating small cancer populations, similar to small populations in natural extinctions, will usually require a sequence of different external perturbations that produce negative, synergistic dynamics termed the "extinction vortex." By exploiting these unique extinction vulnerabilities of small cancer populations, the optimal therapeutic sequences may be informed by evolution-informed strategies for patients with LARC.

Intratumor heterogeneity: A new perspective on colorectal cancer research

Colorectal cancers generally consist of multiple subclones. These subclones have their own unique characteristics, resulting in intratumor heterogeneity (ITH). As the discussion of ITH has advanced, a model describing the relationship of ITH to the tumor has gradually emerged. ITH can be divided into two types of intraprimary tumor heterogeneity and intraindividual tumor heterogeneity, the former for further understanding of tumor composition, and the latter for providing more information about evolutionary patterns. With the rapid development of new methods, such as next‐generation, polyguanine region sequencing, and Image detection, researchers may unravel the secrets underlying ITH. The higher the ITH of the tumor, the richer the interaction between the subclones maybe, or the greater the chance of the tumor getting more powerful subclones may be, thus increasing the malignant potential of the tumor. Existing evidence suggests that ITH may increase the ability of tumors to resist treatment and can be used as an independent influence on the prognosis of colorectal cancer. We reviewed 80 recent studies to give researchers a new perspective on colorectal cancer. There is still a limited amount of research in this area. Further study of the relationship between ITH and clinical endpoints may lead to the development of new treatment strategies.

Identification of candidate mediators of chemoresponse in breast cancer through therapy-driven selection of somatic variants

Purpose

More than a third of primary breast cancer patients are treated with cytotoxic chemotherapy, typically without guidance from predictive markers. Increased use of neoadjuvant chemotherapy provides opportunities for identification of molecules associated with treatment response, by comparing matched tumour samples before and after therapy. Our hypothesis was that somatic variants of increased prevalence after therapy promote resistance, while variants with reduced prevalence cause sensitivity.

Methods

We performed systematic analyses of matched pairs of cancer exomes from primary oestrogen receptor-positive/HER2-negative breast cancers (n = 6) treated with neoadjuvant epirubicin/cyclophosphamide. We identified candidate genes as mediators of chemotherapy response by consistent subclonal changes in somatic variant prevalence through therapy, predicted variant impact on gene function, and enrichment of specific functional pathways. Influence of candidate genes on breast cancer outcome was tested using publicly available breast cancer expression data (n = 1903).

Results

We identified 14 genes as the strongest candidate mediators of chemoresponse: TCHH, MUC17, ARAP2, FLG2, ABL1, CENPF, COL6A3, DMBT1, ITGA7, PLXNA1, S100PBP, SYNE1, ZFHX4, and CACNA1C. Genes contained somatic variants showing prevalence changes in up to 4 patients, with up to 3 being predicted as damaging. Genes coding for extra-cellular matrix components or related signalling pathways were significantly over-represented among variants showing prevalence changes. Expression of 5 genes (TCHH, ABL1, CENPF, S100PBP, and ZFHX4) was significantly associated with patient survival.

Conclusions

Genomic analysis of paired pre- and post-therapy samples resulting from neoadjuvant therapy provides a powerful method for identification of mediators of response. Genes we identified should be assessed as predictive markers or targets in chemo-sensitization.

Electronic supplementary material

The online version of this article (10.1007/s10549-020-05836-7) contains supplementary material, which is available to authorized users.

Unintended consequences of treating early rectal cancers for complete clinical response with chemoradiotherapy

The aim was to examine the current trend in rectal cancer, which is to extend ’watch-and-wait’ to earlier-stage tumors, not normally treated with chemoradiotherapy, to define the up-side and down-side regarding quality of life (QOL) and anorectal/sexual/urinary function from this approach. We reviewed the literature regarding a ‘watch-and-wait’ strategy after neoadjuvant chemoradiotherapy. The primary outcome measure was complete clinical response. Secondary measures included colostomy rate, functional outcomes and QOL. There is a trend to use chemoradiotherapy in earlier tumors using dose-escalation of radiation and/or additional chemotherapy, resulting in high rates of complete clinical response, which may impact adversely on QOL if radical surgery is subsequently required. Focusing on organ-preservation as the primary goal of treatment rather than overall functional outcomes and QOL for the whole population, may not provide patients with sufficient information for optimal decision-making.

How to measure tumour response in rectal cancer? An explanation of discrepancies and suggestions for improvement

Various methods categorize tumour response after neoadjuvant therapy, including down-staging and tumour regression grading. Response categories allow comparison of different treatments within clinical trials and predict outcome. A reproducible response categorization could identify subgroups with high or low risk for the most appropriate subsequent treatments, like watch and wait. Lack of standardization and interpretation difficulties currently limit the usability of these approaches. In this review we describe these difficulties for the evaluation of chemoradiation in rectal cancer. An alternative approach of tumour response is based on patterns of residual disease, including fragmentation. We summarise the evidence behind this alternative method of response categorisation, which explains a number of very relevant clinical discrepancies. These issues include differences between downstaging and tumour regression, high local regrowth in advanced tumours during watchful waiting procedures, the importance of resection margins, the limited value of post-treatment biopsies and the relatively poor outcome of patients with a near complete pathological response. Recognition of these patterns of response can allow meaningful development of novel biomarkers in the future.