Low prevalence of deficient mismatch repair (dMMR) protein in locally advanced rectal cancers (LARC) and treatment outcomes

Digitally assessed lymphocyte infiltration in rectal cancer biopsies is associated with pathological response to neoadjuvant therapy

A frequently used treatment strategy in locally advanced rectal cancer (RC) is neoadjuvant therapy followed by surgery. Patients treated with neoadjuvant therapy achieve varying pathological response, and currently, predicting the degree of response is challenging. This study examined the association between digitally assessed histopathological features in the diagnostic biopsies and pathological response to neoadjuvant therapy, aiming to find potential predictive biomarkers. 50 patients with RC treated with neoadjuvant chemotherapy and/or radiotherapy followed by surgery were included. Deep learning-based digital algorithms were used to assess the epithelium tumor area percentage (ETP) based on H&E-stained slides, and to quantify the density of CD3+ and CD8+ lymphocytes, as well as the CD8+/CD3+ lymphocyte percentage, based on immunohistochemically stained slides, from the diagnostic tumor biopsies. Pathological response was assessed according to the Mandard method. A good pathological response was defined as tumor regression grade (TRG) 1-2, and a complete pathological response was defined as Mandard TRG 1. Associations between the ETP and lymphocyte densities in the diagnostic biopsies and the pathological response were examined. The density of CD8+ lymphocytes, and the CD8+/CD3+ lymphocyte percentage, were associated with both good and complete response to neoadjuvant therapy, while the density of CD3+ lymphocytes was associated with complete response. The ETP did not correlate with response to neoadjuvant therapy. It is well-known that infiltration of lymphocytes in colorectal cancer is a prognostic biomarker. However, assessment of CD8+ and CD3+ lymphocytes in the diagnostic tumor biopsies of patients with RC may also be useful in predicting response to neoadjuvant therapy.

Modified FOLFIRINOX (mFOLFIRINOX) as neoadjuvant therapy and 'salvage' in patients with high risk locally advanced rectal cancers - tolerance and early outcomes

BACKGROUND

There is limited data with regard to the use of modified 5-fluoroural-leucovorin-irinotecan-oxaliplatin (mFOLFIRINOX) in terms of tolerance and enabling total mesorectal excision (TME) of locally advanced rectal adenocarcinomas (LARC) with high-risk characteristics (T4b status, signet ring histology etc) post standard neoadjuvant long course chemoradiation (NACTRT) or short course radiation (SCRT) and chemotherapy.

MATERIALS AND METHODS

Patients with LARC from January 2018 to December 2020 receiving mFOLFIRINOX post NACTRT/SCRT to facilitate TME were evaluated. The primary endpoint was assessment of grade 3 and grade 4 treatment related toxicity and TME rates. Event free survival (EFS), where event was defined as disease progression or recurrence post resection after mFOLFIRINOX, was calculated by Kaplan Meier method.

RESULTS

Forty-seven patients were evaluated with a median age of 33 years (Range:18-59), 45% T4b status, 96% radiological circumferential margin (CRM) involved (79% CRM positive post NACTRT/SCRT), 43% extramural venous invasion (n=33) and 36% signet ring histology. 62% had received prior NACTRT and 38% had received SCRT with chemotherapy before receiving mFOLFIRINOX. The most common grade 3 and grade 4 treatment related side effects included diarrhoea (7%), anaemia (4%) and infections (4%). Intended duration of mFOLFIRINOX or beyond was completed in 94% of patients. 60% of patients underwent curative local resection with R0 resection rates of 100% (n=28) and pathological complete response rates of 21%. The most common surgeries done were exenterations and abdominoperineal in 22% and 17% patients respectively. With a median follow up of 19 months, 24 patients had recurred or progressed for a median EFS of 20 months [95% confidence interval (CI): 15-24].

CONCLUSIONS

Locally advanced rectal cancers with high-risk characteristics are a niche group of cancers with less-than-optimal outcomes post standard neoadjuvant strategies. mFOLFIRINOX appears to be well tolerated and enables TME in a significant proportion of these patients.

Report from the 24th Annual Western Canadian Gastrointestinal Cancer Consensus Conference on Colorectal Cancer, Richmond, British Columbia, 28-29, October 2022

The 24th annual Western Canadian Gastrointestinal Cancer Consensus Conference (WCGCCC) was held in Richmond, British Columbia, on 28-29 October 2022. The WCGCCC is an interactive multidisciplinary conference attended by healthcare professionals from across Western Canada (British Columbia, Alberta, Saskatchewan, and Manitoba) who are involved in the care of patients with gastrointestinal cancer. Surgical, medical, and radiation oncologists; pathologists; radiologists; and allied health care professionals such as dieticians, nurses and a genetic counsellor participated in presentation and discussion sessions for the purpose of developing the recommendations presented here. This consensus statement addresses current issues in the management of colorectal cancer.

Controversies and management of deficient mismatch repair gastrointestinal cancers in the neoadjuvant setting

High microsatellite instability (MSI-H)/deficient mismatch repair (dMMR) phenotype is a distinct molecular signature across gastrointestinal cancers characterized by high tumor mutational burden and high neoantigen load. Tumors harboring dMMR are highly immunogenic and heavily infiltrated by immune cells; consequently, they are uniquely vulnerable to therapeutic strategies enhancing immune antitumor response such as checkpoint inhibitors. The MSI-H/dMMR phenotype arose as a powerful predictor of response to immune checkpoint inhibitors with evidence supporting significantly improved outcomes in the metastatic setting. On the other hand, the genomic instability characteristic of MSI-H/dMMR tumors appears to be associated with decreased sensitivity to chemotherapy, and the benefits of standard adjuvant or neoadjuvant chemotherapy approaches in this subtype are being increasingly questioned. Here, we review the prognostic and predictive impact of MMR status in localized gastric and colorectal cancers, and highlight the emerging clinical data incorporating checkpoint inhibitors in the neoadjuvant setting.

Clinicopathological characteristics of high microsatellite instability/mismatch repair-deficient colorectal cancer: A narrative review

Colorectal cancers (CRCs) with high microsatellite instability (MSI-H) and deficient mismatch repair (dMMR) show molecular and clinicopathological characteristics that differ from those of proficient mismatch repair/microsatellite stable CRCs. Despite the importance of MSI-H/dMMR status in clinical decision making, the testing rates for MSI and MMR in clinical practice remain low, even in high-risk populations. Additionally, the real-world prevalence of MSI-H/dMMR CRC may be lower than that reported in the literature. Insufficient MSI and MMR testing fails to identify patients with MSI-H/dMMR CRC, who could benefit from immunotherapy. In this article, we describe the current knowledge of the clinicopathological features, molecular landscape, and radiomic characteristics of MSI-H/dMMR CRCs. A better understanding of the importance of MMR/MSI status in the clinical characteristics and prognosis of CRC may help increase the rates of MMR/MSI testing and guide the development of more effective therapies based on the unique features of these tumors.

Treatment of Metastatic Colorectal Cancers in Resource-Constrained Low- and Middle-Income Countries (LMICS) Scenario-Outcomes, Practice Patterns, and Commentary on Treatment Costs

Anant RamaswamyIntroduction  The overall survival (OS) of metastatic colorectal cancers (mCRCs) in clinical practice and resource-constrained low- and middle-income countries (LMICS) like India is not known. Materials and Methods  Data of patients with mCRC treated between January 2013 and August 2017 were accessed from a prospectively maintained database. Demographics, disease characteristics, chemotherapeutic regimens, use of monoclonal antibodies, and survival outcomes in treated patients were collected and analyzed. Costs of treatment options as off 2017 were also interpreted. Results  The data of 403 patients satisfied prespecified inclusion criteria and were included for analysis. The median age of the cohort was 48 years (range: 17-86) with a predominance of rectal cancers (63.3%), liver alone metastases (47.1%), and resected primary (69.7%). Signet ring histology was present in 82 patients (20.3%). The most commonly used first-line regimen (CT1) was modified capecitabine-oxaliplatin (53.3%). Two hundred and nineteen patients (54.3%) received second-line systemic therapy (CT2). Patients received a median of two lines of therapy (range: 1-6). MoAbs were used by 48 patients (13.4%) with CT1 and 34 patients (15.5%) with CT2. Median OS of the entire cohort was 17.61 months (95% confidence interval: 15.48-19.74), which was within the predicted range, as per investigator hypothesis. The presence of signet ring histology ( p <0.001), raised carcinoembryonic antigen at baseline ( p =0.017), and the absence of a resected primary ( p <0.001) predicted inferior median OS. Conclusions  Survival of patients with mCRC in a resource-constrained LMIC scenario like India is approximately 12 to 15 months lower than published trial data. Limited access to targeted therapy and newer expensive treatment options due to financial constraints may contribute to this disparity.

Microsatellite instability in rectal cancer: what does it mean? A study of two randomized trials and a systematic review of the literature

Currently, compelling evidence illustrates the significance of determining microsatellite instability (MSI) in colorectal cancer (CRC). The association of MSI with proximal CRC is well established, however, its implications in patients with rectal cancer remain undefined. We therefore aimed to determine the role of MSI with respect to incidence and outcome in patients with rectal cancer, by the examination of patients from two prospective phase III trials: TME trial and PROCTOR-SCRIPT trial (n=1250). No differences in terms of overall survival (HR 1.00, 95%CI 0.69-1.47) and disease-free survival (HR 1.00, 95%CI 0.68-1.45) were observed in patients with MSI compared to microsatellite stable (MSS) rectal cancer. In addition, we performed a literature review to evaluate the overall prevalence, the effect on survival and the response to neo-adjuvant treatment in patients with MSI rectal cancer compared with MSS rectal cancer. The total number of MSI cases in the included studies (including our own) was 1220 (out of 16526 rectal cancer patients), with an overall prevalence of 6.7% (SE 1.19%). Both for overall survival as for disease-free survival there was no impact of MSI status on prognosis (HR 1.00, 95%CI 0.77-1.29 and HR 0.86, 95% CI 0.60-1.22, respectively). The risk ratio for downstaging and pCR showed also no impact of MSI status (RR 1.15, 95% CI 0.86-1.55 and RR 0.81, 95% CI 0.54-1.22 respectively). In conclusion, rectal cancer patients with MSI form a distinct and rare subcategory, however, there is no prognostic effect of MSI in rectal cancer patients.

Robotic and robotic-assisted vs laparoscopic rectal cancer surgery: A meta-analysis of short-term and long-term results

The usage of robotic surgery in rectal cancer (RC) is increasing, but there is an ongoing debate as to whether it provides any benefit. This study conducted a meta-analysis of rectal cancer surgery for short-term and long-term outcome by Robotic and robotic-assisted surgery (RS) vs laparoscopic surgery (LS).Pubmed, Embase, Ovid, CNKI, Cochrane Library and Web of Science databases were searched. Studies clearly documenting a comparison of short-term and long-term effect between RS and LS for RC were selected. Lymph node harvested, operation time, hospital stay, circumferential resection margins（CRM), complications, 3-year disease-free survival (DFS) and 5-year DFS parameters were evaluated. All data were performed by Review Manager 5.3 software. Nine studies were collected that included 1436 cases in total, 716 (49.86%) in the RS group, 720(50.14%) in the LS group. Compared with LS, RS was associated with longer operation time (MD 35.19, 95%CI [7.57, 62.81]; P = 0.01), but similar hospital stay (MD -0.43, 95%CI [-0.87,0.01]; P = 0.05).Lymph node harvested, CRM, complications, 3-year DFS, 5-year DFS had no significance difference between RS and LS groups（MD -0.67，95%CI[-1.53，0.19]；P = 0.13；MD 0.86，95%CI[0.54,1.37]；P = 0.52；MD 0.97，95%CI [0.73,1.29]；P = 0.86；MD 0.94，95%CI[0.60,1.48]；P = 0.79；MD 0.88，95%CI[0.52,1.47]；P = 0.61 respectively）.RS is feasible and safe for RC. It has an advantage in short -term outcome and a similar effect in long-term outcome compared with LS.

A panel of tumor biomarkers to predict complete pathological response to neo-adjuvant treatment in Locally Advanced Rectal Cancer

Pathological complete response after neoadjuvant chemoradiotherapy in locally advanced rectal cancer patients is related to a favorable prognosis. The identification of early biomarkers predictive of pathological complete response would help optimize the multimodality management of the patients. A panel of 11 tumor-related proteins was investigated by immunohistochemistry in the pretreatment biopsy of a group of locally advanced rectal cancer patients to identify early biomarkers of pathological complete response to neoadjuvant chemoradiotherapy. A mono-institutional retrospective cohort of 95 stage II/III locally advanced rectal cancer patients treated with neoadjuvant chemoradiotherapy and surgery was selected based on clinical–pathological characteristics and the availability of a pretreatment tumor biopsy. Eleven selected protein marker expression (MLH1, GLUT1, Ki67, CA-IX, CXCR4, COX2, CXCL12, HIF1α, VEGF, CD44, and RAD51) was investigated. The optimal cutoff values were calculated by receiver operating characteristic curve analysis. Classification and regression tree analysis was performed to investigate the biomarker interaction. Patients presenting either Ki-67 or HIF1α or RAD51 below the cutoff value, or CXCR4 or COX2 above the cutoff value, were more likely to get a pathological complete response. Classification and regression tree analysis identified three groups of patients resulting from the combination of Ki-67 and CXCR4 expression. Patients with high expression of Ki-67 had the lowest chance to get a pathological complete response (18%), as compared to patients with low expression of both Ki-67 and CXCR4 (29%), and patients with low Ki-67 and high CXCR4 expression (70%). Pretreatment Ki-67, CXCR4, COX2, HIF1α, and RAD51 in tumor biopsies are associated with pathological complete response after neoadjuvant chemoradiotherapy in locally advanced rectal cancer. A combined evaluation of Ki-67 and CXCR4 would increase their predictive potential. If validated, their optimal cutoff could be used to select patients for a tailored multimodality treatment.

Outcomes of Definitive Treatment of Signet Ring Cell Carcinoma of the Rectum: Is Minimal Invasive Surgery Detrimental in Signet Ring Rectal Cancers?

The outcome of surgery for signet ring adenocarcinoma of rectum is suboptimal with high predilection for locoregional and peritoneal metastases. Lack of intercellular adhesion due to focal loss of epithelial cell adhesion molecule (EpCAM) may account for this. In such patients, whether minimal invasive surgery carries a high risk of dissemination by pneumoperitoneum and tumor implantation remains uncertain. The aim of this study was to compare the outcomes of patients undergoing minimally invasive surgery (MIS) versus open surgery in patients with signet ring cell adenocarcinoma of rectum. A retrospective study was conducted at a tertiary care center over 3 years on 39 patients undergoing open surgery and 40 patients undergoing MIS diagnosed with signet ring cell carcinoma (SRCC) identified from our surgical database. Patient characteristics in terms of demographics, clinicoradiological staging, neoadjuvant therapy, and type of surgery with morbidity were compared in the two groups. Data on patients undergoing adjuvant therapy and 3 years disease-free survival (DFS) and overall survival (OS) were analyzed. Recurrence patterns in both groups were separately identified as locoregional, peritoneal, or systemic. The number of patients undergoing surgery in the two arms was 40 (MIS) and 39 (open). In the MIS arm, mean DFS was 29 months whereas in the open arm, it was 25.8 months. The mean OS was 33.65 months for the MIS arm and that for the open arm was 36.34 months. This retrospective study reveals no significant difference in outcomes of surgery for signet ring cell rectal cancers with either MIS or open approach.

Complete response in patients with locally advanced rectal cancer after neoadjuvant treatment with nivolumab

Introduction: PD-1 inhibitors have been approved for the treatment of dMMR patients with metastatic colorectal cancer, but the efficacy of neoadjuvant treatment with PD-1 in dMMR locally advanced rectal cancer (LARC) patients has not yet been defined.

Patients and methods: Two patients with LARC received Nivolumab as neoadjuvant treatment in July 2017. Whole-exome sequencing (WES) and multiplex immunofluorescence analysis were performed.

Results: Of the two patients, one achieved pathological complete response after six cycles of nivolumab followed by surgery. The other patient was confirmed to be clinical complete response after six cycles of nivolumab. “Watch and wait” strategy was performed for anal preservation. WES showed high tumor mutation burden. Multiplex immunofluorescence analysis showed immune microenvironment alternation between pretreatment specimen and post-treatment specimen.

Conclusion: Neoadjuvant nivolumab induced complete response in both of the two patients with LARC. Immunotherapy might be an alternative strategy for neoadjuvant treatment for dMMR/MSI rectal cancer.