Immunotherapy in Gastrointestinal Cancers.

Immunotherapy has revolutionised cancer treatment over the past decade. Long-term durable responses can be achieved in some cancer patient populations that were previously facing terminal disease. In this chapter, we summarise current phase 3 clinical trial evidence for the use of immunotherapy in gastrointestinal cancers (oesophageal squamous cell carcinoma, oesophago-gastric adenocarcinoma, pancreatic cancer, biliary cancer, hepatocellular carcinoma, colorectal cancer, and squamous cell cancer of the anus). We discuss meaningful biomarkers used in clinical trials to select patients most likely to benefit from immunotherapy, such as mismatch-repair deficiency (MMRd)/microsatellite instability (MSI) and programmed-death-ligand-1 (PD-L1) immunohistochemistry (IHC) expression. Clinical questions are arising regarding the role of immunotherapy in the adjuvant/perioperative setting, optimal timing of surgery in patients who respond to immunotherapy, and toxicities specific to patients with gastrointestinal malignancies. We outline the current landscape and future horizon of immunotherapy in gastrointestinal cancers, such as strategies to increase effectiveness of checkpoint blockade through combinations with other checkpoint inhibitors, cytotoxic chemotherapy, targeted agents, radiotherapy, CAR-T therapy, and cancer vaccines.

MicroRNAs as biomarkers for trastuzumab-based therapy in HER2-positive advanced oesophago-gastric cancer patients.

Background: This study aimed to identify microRNAs (miRs) as circulating biomarkers of resistance to first-line trastuzumab-based therapy in advanced HER2-positive oesophago-gastric cancer patients. Methods: A high-throughput 1015 Exiqon miRCURY LNA™ microRNA inhibitor library screen was performed in trastuzumab-treated HER2-positive NCI-N87 and HER2-negative FLO-1 oesophago-gastric cancer cell lines. NanoString nCounter® miR analysis was performed in NCI-N87, FLO-1, and MAGIC trial (ISRCTN93793971) formalin-fixed paraffin-embedded (FFPE) oesophago-gastric cancer patient samples. MiR-148a-3p copies in plasma samples were quantified using digital droplet polymerase chain reaction (ddPCR) from HER2-positive oesophago-gastric cancer patients treated with standard-of-care trastuzumab-based therapy within the FOrMAT (NCT02112357) and PLATFORM (NCT02678182) clinical trials. The primary endpoints were overall survival (OS) for plasma miR-148a-3p HIGH (>median) versus LOW (≤median). The secondary endpoints were progression-free survival (PFS) and 3-month progression-free rates (PFRs) miR-148a-3p HIGH versus LOW. PLATFORM sensitivity analysis normalised miR-148a-3p (NmiR-148a-3p). Results: The inhibition of miR-148a-3p reduced NCI-N87 relative cell viability (<0.6) and expression was high (>242) in NCI-N87 and HER2-positive MAGIC trial patients (n=5). Normalised-miR-148a-3p (NmiR-148a-3p) LOW versus HIGH demonstrated a statistically significant difference in 3-month PFRs (n=23; OR, 0.11 [0.02-0.78]; p=0.027; aOR, 0.03 [0.001-0.71], p=0.029) but no difference in OS or PFS. There was no statistically significant relationship between miR-148-3p LOW versus HIGH for OS (PLATFORM, n=62; hazard ratio [HR], 0.98 [0.57-1.66]; p=0.933; FOrMAT, n=8; HR, 0.54 [0.13-2.31]; p=0.322), PFS (n=62; HR, 1.08 [0.65-1.81]; p=0.759; FOrMAT, n=8; HR, 1.26 [0.31-5.07]; p=0.714), or PFRs (PLATFORM, n=31; odds ratio [OR], 0.67 [0.2-2.8]; p=0.577). Conclusion: Normalised miR-148a-3p may be a relevant biomarker for trastuzumab-based therapy in advanced HER2-positive oesophago-gastric cancer patients.

Advances in immunotherapy for MMR proficient colorectal cancer.

Survival in mismatch-repair proficient (MMRp) metastatic colorectal cancer (mCRC) remains poor and chemotherapy is the mainstay of treatment. Immunotherapy has demonstrated durable responses and a favourable side-effect profile in various cancer types and multiple clinical trials have been conducted in MMRp mCRC. In this review we summarise emerging trial data which demonstrate promising immunotherapy combinations in MMRp mCRC. We outline barriers to success, evaluate emerging biomarkers and discuss potential strategies to increase the effectiveness of immunotherapy in MMRp mCRC.

Emerging HER2-directed therapeutic agents for gastric cancer in early phase clinical trials.

INTRODUCTION: HER2 positive gastric cancer is a distinct subgroup overexpressing the HER2 receptor. For a decade, first-line Trastuzumab was the only licensed HER2-directed therapy for HER2 positive advanced gastric cancer following results from the ToGA trial in 2010 demonstrating a survival benefit when added to chemotherapy. Within the last year, significant advances have taken place in the field of HER2-directed gastric cancer therapy. AREAS COVERED: This review discusses pivotal clinical trial results and summarizes current clinical trials of HER2-directed therapy in gastric cancer. Evidence for HER2-directed antibodies, immunotherapy, immune stimulating antibody conjugates, antibody-drug conjugates (including DESTINY trial results), and tyrosine kinase inhibitors are placed into clinical context. Key challenges including resistance mechanisms and drug toxicities are outlined. Search terms 'HER2' and 'gastric cancer' were entered into ClinicalTrials.gov, PubMed, and Google. Only English-language studies were included. EXPERT OPINION: Clinical management of HER2 positive gastric cancer patients is likely to change significantly over the next 5 years. Checkpoint inhibition is likely to be used alongside HER2-directed therapy and chemotherapy first-line in advanced disease. Trastuzumab deruxtecan is likely to be offered second-line and beyond. The sheer number of clinical trials of HER2-directed therapy in gastric cancer are testament to progress and potential.

miR-31-3p Expression and Benefit from Anti-EGFR Inhibitors in Metastatic Colorectal Cancer Patients Enrolled in the Prospective Phase II PROSPECT-C Trial.

PURPOSE: Anti-EGFR mAbs are effective in the treatment of metastatic colorectal cancer (mCRC) patients. RAS status and tumor location (sidedness) are predictive markers of patients' response to anti-EGFR mAbs. Recently, low miR-31-3p expression levels have been correlated with clinical benefit from the anti-EGFR mAb cetuximab. Here, we aimed to validate the predictive power of miR-31-3p in a prospective cohort of chemorefractory mCRC patients treated with single-agent anti-EGFR mAbs. EXPERIMENTAL DESIGN: miR-31-3p was tested by in situ hybridization (ISH) in 91 pretreatment core biopsies from metastatic deposits of 45 patients with mCRC. Sequential tissue biopsies obtained before treatment, at the time of partial response, and at disease progression were tested to monitor changes in miR-31-3p expression overtreatment. miR-31-3p expression, sidedness, and RAS status in pretreatment cell-free DNA were combined in multivariable regression models to assess the predictive value of each variable alone or in combination. RESULTS: Patients with low miR-31-3p expression in pretreatment biopsies showed better overall response rate, as well as better progression-free survival and overall survival, compared to those with high miR-31-3p expression. The prognostic effect of miR-31-3p was independent from age, gender, and sidedness. No significant changes in the expression of miR-31-3p were observed when sequential tissue biopsies were tested in long-term or poor responders to anti-EGFR mAbs. miR-31-3p scores were similar when pretreatment biopsies were compared with treatment-naïve archival tissues (often primary colorectal cancer). CONCLUSIONS: Our study validates the role of miR-31-3p as potential predictive biomarker of selection for anti-EGFR mAbs.

Longitudinal Liquid Biopsy and Mathematical Modeling of Clonal Evolution Forecast Time to Treatment Failure in the PROSPECT-C Phase II Colorectal Cancer Clinical Trial.

Sequential profiling of plasma cell-free DNA (cfDNA) holds immense promise for early detection of patient progression. However, how to exploit the predictive power of cfDNA as a liquid biopsy in the clinic remains unclear. RAS pathway aberrations can be tracked in cfDNA to monitor resistance to anti-EGFR monoclonal antibodies in patients with metastatic colorectal cancer. In this prospective phase II clinical trial of single-agent cetuximab in RAS wild-type patients, we combine genomic profiling of serial cfDNA and matched sequential tissue biopsies with imaging and mathematical modeling of cancer evolution. We show that a significant proportion of patients defined as RAS wild-type based on diagnostic tissue analysis harbor aberrations in the RAS pathway in pretreatment cfDNA and, in fact, do not benefit from EGFR inhibition. We demonstrate that primary and acquired resistance to cetuximab are often of polyclonal nature, and these dynamics can be observed in tissue and plasma. Furthermore, evolutionary modeling combined with frequent serial sampling of cfDNA allows prediction of the expected time to treatment failure in individual patients. This study demonstrates how integrating frequently sampled longitudinal liquid biopsies with a mathematical framework of tumor evolution allows individualized quantitative forecasting of progression, providing novel opportunities for adaptive personalized therapies.Significance: Liquid biopsies capture spatial and temporal heterogeneity underpinning resistance to anti-EGFR monoclonal antibodies in colorectal cancer. Dense serial sampling is needed to predict the time to treatment failure and generate a window of opportunity for intervention. Cancer Discov; 8(10); 1270-85. ©2018 AACR. See related commentary by Siravegna and Corcoran, p. 1213 This article is highlighted in the In This Issue feature, p. 1195.

HER2 inhibition in gastro-oesophageal cancer: A review drawing on lessons learned from breast cancer.

Human epidermal growth factor receptor 2 (HER2)-inhibition is an important therapeutic strategy in HER2-amplified gastro-oesophageal cancer (GOC). A significant proportion of GOC patients display HER2 amplification, yet HER2 inhibition in these patients has not displayed the success seen in HER2 amplified breast cancer. Much of the current evidence surrounding HER2 has been obtained from studies in breast cancer, and we are only recently beginning to improve our understanding of HER2-amplified GOC. Whilst there are numerous licensed HER2 inhibitors in breast cancer, trastuzumab remains the only licensed HER2 inhibitor for HER2-amplified GOC. Clinical trials investigating lapatinib, trastuzumab emtansine, pertuzumab and MM-111 in GOC have demonstrated disappointing results and have not yet changed the treatment paradigm. Trastuzumab deruxtecan may hold promise and is currently being investigated in phase II trials. HER2 amplified GOC differs from breast cancer due to inherent differences in the HER2 amino-truncation and mutation rate, loss of HER2 expression, alterations in HER2 signalling pathways and differences in insulin-like growth factor-1 receptor and MET expression. Epigenetic alterations involving different microRNA profiles in GOC as compared to breast cancer and intrinsic differences in the immune environment are likely to play a role. The key to effective treatment of HER2 amplified GOC lies in understanding these mechanisms and tailoring HER2 inhibition for GOC patients in order to improve clinical outcomes.

Patient-derived organoids model treatment response of metastatic gastrointestinal cancers.

Patient-derived organoids (PDOs) have recently emerged as robust preclinical models; however, their potential to predict clinical outcomes in patients has remained unclear. We report on a living biobank of PDOs from metastatic, heavily pretreated colorectal and gastroesophageal cancer patients recruited in phase 1/2 clinical trials. Phenotypic and genotypic profiling of PDOs showed a high degree of similarity to the original patient tumors. Molecular profiling of tumor organoids was matched to drug-screening results, suggesting that PDOs could complement existing approaches in defining cancer vulnerabilities and improving treatment responses. We compared responses to anticancer agents ex vivo in organoids and PDO-based orthotopic mouse tumor xenograft models with the responses of the patients in clinical trials. Our data suggest that PDOs can recapitulate patient responses in the clinic and could be implemented in personalized medicine programs.

KRAS and BRAF mutations in circulating tumour DNA from locally advanced rectal cancer.

There are limited data on circulating, cell-free, tumour (ct)DNA analysis in locally advanced rectal cancer (LARC). Digital droplet (dd)PCR was used to investigate KRAS/BRAF mutations in ctDNA from baseline blood samples of 97 LARC patients who were treated with CAPOX followed by chemoradiotherapy, surgery and adjuvant CAPOX ± cetuximab in a randomised phase II trial. KRAS mutation in G12D, G12V or G13D was detected in the ctDNA of 43% and 35% of patients with tumours that were mutant and wild-type for these hotspot mutations, respectively, according to standard PCR-based analyses on tissue. The detection rate in the ctDNA of 10 patients with less common mutations was 50%. In 26 cases ctDNA analysis revealed KRAS mutations that were not previously found in tissue. Twenty-two of these (84.6%) were detected following repeat tissue testing by ddPCR. Overall, the ctDNA detection rate in the KRAS mutant population was 66%. Detection of KRAS mutation in ctDNA failed to predict prognosis or refine patient selection for cetuximab. While this study confirms the feasibility of ctDNA analysis in LARC and the high sensitivity of ddPCR, larger series are needed to better address the role of ctDNA as a prognostic or predictive tool in this setting.

Functional imaging and circulating biomarkers of response to regorafenib in treatment-refractory metastatic colorectal cancer patients in a prospective phase II study.

OBJECTIVE: Regorafenib demonstrated efficacy in patients with metastatic colorectal cancer (mCRC). Lack of predictive biomarkers, potential toxicities and cost-effectiveness concerns highlight the unmet need for better patient selection. DESIGN: Patients with RAS mutant mCRC with biopsiable metastases were enrolled in this phase II trial. Dynamic contrast-enhanced (DCE) MRI was acquired pretreatment and at day 15 post-treatment. Median values of volume transfer constant (Ktrans), enhancing fraction (EF) and their product KEF (summarised median values of Ktrans× EF) were generated. Circulating tumour (ct) DNA was collected monthly until progressive disease and tested for clonal RAS mutations by digital-droplet PCR. Tumour vasculature (CD-31) was scored by immunohistochemistry on 70 sequential tissue biopsies. RESULTS: Twenty-seven patients with paired DCE-MRI scans were analysed. Median KEF decrease was 58.2%. Of the 23 patients with outcome data, >70% drop in KEF (6/23) was associated with higher disease control rate (p=0.048) measured by RECIST V. 1.1 at 2 months, improved progression-free survival (PFS) (HR 0.16 (95% CI 0.04 to 0.72), p=0.02), 4-month PFS (66.7% vs 23.5%) and overall survival (OS) (HR 0.08 (95% CI 0.01 to 0.63), p=0.02). KEF drop correlated with CD-31 reduction in sequential tissue biopsies (p=0.04). RAS mutant clones decay in ctDNA after 8 weeks of treatment was associated with better PFS (HR 0.21 (95% CI 0.06 to 0.71), p=0.01) and OS (HR 0.28 (95% CI 0.07-1.04), p=0.06). CONCLUSIONS: Combining DCE-MRI and ctDNA predicts duration of anti-angiogenic response to regorafenib and may improve patient management with potential health/economic implications.