C. Cardone

Mechanisms of resistance to anti-epidermal growth factor receptor inhibitors in metastatic colorectal cancer

The prognosis of patients with metastatic colorectal cancer (mCRC) remain poor despite the impressive improvement of treatments observed over the last 20 years that led to an increase in median overall survival from 6 mo, with the only best supportive care, to approximately 30 mo with the introduction of active chemotherapy drugs and targeted agents. The monoclonal antibodies (moAbs) cetuximab and panitumumab, directed against the epidermal growth factor receptor (EGFR), undoubtedly represent a major step forward in the treatment of mCRC, given the relevant efficacy in terms of progression-free survival, overall survival, response rate, and quality of life observed in several phase III clinical trials among different lines of treatment. However, the anti-EGFR moAbs were shown only to be effective in a subset of patients. For instance, KRAS and NRAS mutations have been identified as biomarkers of resistance to these drugs, improving the selection of patients who might derive a benefit from these treatments. Nevertheless, several other alterations might affect the response to these drugs, and unfortunately, even the responders eventually become resistant by developing secondary (or acquired) resistance in approximately 13-18 mo. Several studies highlighted that the landscape of responsible alterations of both primary and acquired resistance to anti-EGFR drugs biochemically converge into MEK-ERK and PIK3CA-AKT pathways. In this review, we describe the currently known mechanisms of primary and acquired resistance to anti-EGFR moAbs together with the various strategies evaluated to prevent, overcame or revert them.

Cetuximab continuation after first progression in metastatic colorectal cancer (CAPRI-GOIM): a randomized phase II trial of FOLFOX plus cetuximab versus FOLFOX.

BACKGROUND Cetuximab plus chemotherapy is a first-line treatment option in metastatic KRAS and NRAS wild-type colorectal cancer (CRC) patients. No data are currently available on continuing anti-epidermal growth factor receptor (EGFR) therapy beyond progression. PATIENTS AND METHODS We did this open-label, 1:1 randomized phase II trial at 25 hospitals in Italy to evaluate the efficacy of cetuximab plus 5-fluorouracil, folinic acid and oxaliplatin (FOLFOX) as second-line treatment of KRAS exon 2 wild-type metastatic CRC patients treated in first line with 5-fluorouracil, folinic acid and irinotecan (FOLFIRI) plus cetuximab. Patients received FOLFOX plus cetuximab (arm A) or FOLFOX (arm B). Primary end point was progression-free survival (PFS). Tumour tissues were assessed by next-generation sequencing (NGS). This report is the final analysis. RESULTS Between 1 February 2010 and 28 September 2014, 153 patients were randomized (74 in arm A and 79 in arm B). Median PFS was 6.4 [95% confidence interval (CI) 4.7-8.0] versus 4.5 months (95% CI 3.3-5.7); [hazard ratio (HR), 0.81; 95% CI 0.58-1.12; P = 0.19], respectively. NGS was performed in 117/153 (76.5%) cases; 66/117 patients (34 in arm A and 32 in arm B) had KRAS, NRAS, BRAF and PIK3CA wild-type tumours. For these patients, PFS was longer in the FOLFOX plus cetuximab arm [median 6.9 (95% CI 5.5-8.2) versus 5.3 months (95% CI 3.7-6.9); HR, 0.56 (95% CI 0.33-0.94); P = 0.025]. There was a trend in better overall survival: median 23.7 [(95% CI 19.4-28.0) versus 19.8 months (95% CI 14.9-24.7); HR, 0.57 (95% CI 0.32-1.02); P = 0.056]. CONCLUSIONS Continuing cetuximab treatment in combination with chemotherapy is of potential therapeutic efficacy in molecularly selected patients and should be validated in randomized phase III trials.

EGFR in Tumor-Associated Myeloid Cells Promotes Development of Colorectal Cancer in Mice and Associates With Outcomes of Patients

Background & Aims Inhibitors of the epidermal growth factor receptor (EGFR) are the first-line therapy for patients with metastatic colorectal tumors without RAS mutations. However, EGFR inhibitors are ineffective in these patients, and tumor level of EGFR does not associate with response to therapy. We screened human colorectal tumors for EGFR-positive myeloid cells and investigated their association with patient outcome. We also performed studies in mice to evaluate how EGFR expression in tumor cells and myeloid cells contributes to development of colitis-associated cancer and ApcMin-dependent intestinal tumorigenesis. Methods We performed immunohistochemical and immunofluorescent analyses of 116 colorectal tumor biopsies to determine levels of EGFR in tumor and stroma; we also collected information on tumor stage and patient features and outcomes. We used the Mann-Whitney U and Kruskal-Wallis tests to correlate tumor levels of EGFR with tumor stage, and the Kaplan-Meier method to estimate patients’ median survival time. We performed experiments in mice lacking EGFR in intestinal epithelial cells (Villin-Cre; Egfrf/f and Villin-CreERT2; Egfrf/f mice) or myeloid cells (LysM-Cre; Egfrf/f mice) on a mixed background. These mice were bred with ApcMin/+ mice; colitis-associated cancer and colitis were induced by administration of dextran sodium sulfate (DSS), with or without azoxymethane (AOM), respectively. Villin-CreERT2 was activated in developed tumors by administration of tamoxifen to mice. Littermates that expressed full-length EGFR were used as controls. Intestinal tissues were collected; severity of colitis, numbers and size of tumors, and intestinal barrier integrity were assessed by histologic, immunohistochemical, quantitative reverse transcription polymerase chain reaction, and flow cytometry analyses. Results We detected EGFR in myeloid cells in the stroma of human colorectal tumors; myeloid cell expression of EGFR associated with tumor metastasis and shorter patient survival time. Mice with deletion of EGFR from myeloid cells formed significantly fewer and smaller tumors than the respective EGFR-expressing controls in an ApcMin/+ background as well as after administration of AOM and DSS. Deletion of EGFR from intestinal epithelial cells did not affect tumor growth. Furthermore, tamoxifen-induced deletion of EGFR from epithelial cells of established intestinal tumors in mice given AOM and DSS did not reduce tumor size. EGFR signaling in myeloid cells promoted activation of STAT3 and expression of survivin in intestinal tumor cells. Mice with deletion of EGFR from myeloid cells developed more severe colitis after DSS administration, characterized by increased intestinal inflammation and intestinal barrier disruption, than control mice or mice with deletion of EGFR from intestinal epithelial cells. EGFR-deficient myeloid cells in the colon of DSS-treated LysM-Cre; Egfrf/f mice had reduced expression of interleukin 6 (IL6), and epithelial STAT3 activation was reduced compared with controls. Administration of recombinant IL6 to LysM-Cre; Egfrf/f mice given DSS protected them from weight loss and restored epithelial proliferation and STAT3 activation, compared with administration of DSS alone to these mice. Conclusions Increased expression of EGFR in myeloid cells from the colorectal tumor stroma associates with tumor progression and reduced survival time of patients with metastatic colorectal cancer. Deletion of EGFR from myeloid cells, but not intestinal epithelial cells, protects mice from colitis-induced intestinal cancer and ApcMin-dependent intestinal tumorigenesis. Myeloid cell expression of EGFR increases activation of STAT3 and expression of survivin in intestinal epithelial cells and expression of IL6 in colon tissues. These findings indicate that expression of EGFR by myeloid cells of the colorectal tumor stroma, rather than the cancer cells themselves, contributes to tumor development.

Maintenance Treatment with Cetuximab and BAY86-9766 Increases Antitumor Efficacy of Irinotecan plus Cetuximab in Human Colorectal Cancer Xenograft Models

Purpose: The use of cetuximab in the treatment of metastatic colorectal cancer is limited by development of resistance. Experimental Design: We have investigated in three models of highly epidermal growth factor receptor (EGFR)–dependent colorectal cancer xenografts, the effect of maintenance therapy with different kinase inhibitors alone or in combination with cetuximab, after cytotoxic treatment induction with irinotecan plus cetuximab. Results: SW48, LIM 1215, and GEO colorectal cancer cell lines were engrafted into nude mice and treated for 3 weeks with irinotecan and/or cetuximab. The combined treatment induced a significant reduction of tumor size. A subsequent experiment was performed in all three xenograft models in which after an induction treatment with irinotecan plus cetuximab, mice were randomly assigned to one of the following treatments: control, cetuximab, regorafenib, a selective PIK3CA inhibitor (PIK3CAi), a selective MEK inhibitor (MEKi), and/or the combination of each inhibitor with cetuximab. The cetuximab plus MEKi treatment determined the best antitumor activity with suppression of tumor growth. This effect was prolonged for 13 to 15 weeks after cessation of therapy and was accompanied by prolonged survival. Antitumor activity was accompanied by inhibition of the MAPK and MEK pathways. Moreover, in the cetuximab plus MEKi-treated SW48 xenograft group, KRAS mutations as a mechanism of acquired resistance were detected in 25% of cases compared with 75% KRAS mutations in the MEKi-treated group. Conclusions: A possible strategy to prevent and/or overcome resistance to anti-EGFR inhibitors in metastatic colorectal cancer is a maintenance therapy with cetuximab plus MEKi after an initial treatment with irinotecan plus cetuximab. Clin Cancer Res; 21(18); 4153–64. ©2015 AACR.

Sequential HER2 blockade as effective therapy in chemorefractory, HER2 gene-amplified, RAS wild-type, metastatic colorectal cancer: learning from a clinical case

Background Constitutive activation of HER2-dependent intracellular signalling by HER2 gene amplification or by HER2 mutations has been demonstrated as a mechanism of primary and secondary cancer resistance to cetuximab or panitumumab in preclinical and clinical models of metastatic colorectal cancer (mCRC). Both HER2 Amplification for Colorectal Cancer Enhanced Stratification (HERACLES) cohort A and My Pathway clinical trials provided clinical evidence that anti-HER2 therapies could be active in these patients. Patient and methods HER2 gene amplification and HER2 protein overexpression analysis were performed in tumour tissue by fluorescence in situ hybridisation and immunohistochemistry. HER2 positivity was defined according to HERACLES CRC-specific HER2 scoring criteria. DNA analysis for multiple assessment of gene mutations or amplifications was carried out with the next-generation sequencing (NGS) Ion AmpliSeq Colon and Lung Cancer Panel and by using a more extensive targeted high-multiplex PCR-based NGS panel (OncoMine Comprehensive Assay). Results We report the clinical case of a patient with HER2 gene amplified and RAS/BRAF wild-type mCRC who experienced a long lasting and relevant clinical efficacy from sequential anti-HER2 therapies (trastuzumab plus lapatinib, pertuzumab plus trastuzumab, trastuzumab emtansine, trastuzumab plus capecitabine) achieving a cumulative clinical benefit of 29 months, after failure of the first three lines of standard treatments, which included all the potentially active drugs in mCRC, and which accounted for only 14 months of disease control. HER gene amplification was confirmed by NGS on two different metastatic lesions during the evolution of the disease. Conclusion The clinical case highlights the role of HER2 gene amplification as a key genetic driver of cancer development and progression in mCRC and suggests that sequential HER2 blockade could be a potential therapeutic strategy.

Clinical outcome and molecular characterisation of chemorefractory metastatic colorectal cancer patients with long-term efficacy of regorafenib treatment

Please click here to see linked paper Background To investigate the potential predictors of response to regorafenib, in chemorefractory metastatic colorectal cancer (mCRC) patients with long-term efficacy from regorafenib treatment. Methods Retrospective, single institution analysis of patients with chemorefractory mCRC treated with regorafenib, in clinical practice setting. 123 patients were treated and stratified into two groups according to number of cycles received (<7 and ≥7). Overall survival (OS), progression-free survival (PFS) and safety were evaluated. 20 tumour samples (10 poor and 10 long responders) were analysed with the OncoMine Comprehensive Assay for 143 genes. Results A good Eastern Cooperative Oncology Group performance status, a lung limited metastatic disease and a long history of metastatic disease were significantly associated with better OS and PFS from treatment with regorafenib. Mutations were mostly found in TP53, KRAS and PIK3CA as well as in NRAS, ERBB2, SMAD4 and PTEN genes. BCL2L1, ERBB2, KRAS, MYC, GAS6 gene amplifications were detected as well as ALK rearrangement. No significant correlation between molecular alterations and response to regorafenib was observed. However, HER2 gene alterations were found in three poor responder patients, suggesting a potential role in regorafenib resistance. Conversely, GAS6 amplification and SMAD4 mutation, detected in two long responder patients, might suggest a role of epithelial–mesenchymal transition phenotype in regorafenib response. Conclusion A subgroup of long responder patients to regorafenib treatment was identified and a comprehensive molecular characterisation was performed; however, further research efforts are essential to confirm our data.

E46Phase III study of regorafenib versus placebo as maintenance therapy in RAS wild type metastatic colorectal cancer (RAVELLO trial)

TPS789 Background: Treatment of metastatic colorectal cancer (mCRC) has improved due to the introduction of more active chemotherapies (CT) and novel targeted agents that have significantly increased response rate (RR), progression free survival (PFS) and overall survival (OS). Recently, CORRECT and CONCUR trials have demonstrated both activity and efficacy of regorafenib, a small multi-kinase inhibitor, as monotherapy in pretreated mCRC. The wide range of action of regorafenib makes it an ideal candidate for monotherapy in earlier disease treatment lines in which different pathways could be involved in the acquisition of resistance. To improve long term efficacy of first line therapy several therapeutic approaches of maintenance treatment have been explored in mCRC. Methods: RAVELLO is an academic randomized, double-blind, placebo-controlled, multi-center, phase III study designed to evaluate efficacy and safety of regorafenib as maintenance treatment after first line therapy. Eligible patients: patholog...

Antitumor Efficacy of Dual Blockade of EGFR Signaling by Osimertinib in Combination With Selumetinib or Cetuximab in Activated EGFR Human NCLC Tumor Models

Introduction: Osimertinib showed great clinical efficacy for activated‐EGFR NCLC patient treatment. The aim of this work was to test the efficacy of a complete EGFR‐inhibition by osimertinib plus the monoclonal antibody cetuximab or the MEK1/2‐inhibitor selumetinib in EGFR‐mutated NCLC in vivo models. Methods: We evaluated combinations of osimertinib plus selumetinib/cetuximab in HCC827 (E746‐A759del/T790M‐), H1975 (L858R/T790M+), and PC9‐T790M (E746‐A759del /T790M+) xenografts in second‐line therapy after the development of resistance to osimertinib, and in first‐line therapy, and we explored mechanisms of resistance to these treatments. Results: The addition of selumetinib or cetuximab to osimertinib in second‐line therapy reverted the sensibility to osimertinib in the majority of mice, with a response rate (RR) of 50% to 80%, and a median progression‐free survival (mPFS) of first‐ plus second‐line of therapy of 28 weeks. The early use of combinations in first‐line therapy increased the RR to 90%, with an mPFS not reached in all combination arms in the three xenografts models, with a statistically significant superiority (p < 0.005) as compared to osimertinib, achieving in first‐line therapy an mPFS time of 17 to 18 weeks. Moreover, in ex vivo primary cell cultures obtained from osimertinib plus selumetinib‐resistant tumors, we found Hedgehog pathway activation and we showed that therapy with an SMO inhibitor plus osimertinib and selumetinib inhibited proliferation and migratory and invasive properties of resistant cells. Conclusions: We showed that a dual vertical EGFR blockade with osimertinib plus selumetinib/cetuximab is a novel effective therapeutic option in EGFR‐mutated NCLC and that hedgehog pathway activation and its interplay with MAPK is involved in resistance to these combination treatments.

Present and future of metastatic colorectal cancer treatment: A review of new candidate targets

In the last two decades, great efforts have been made in the treatment of metastatic colorectal cancer (mCRC) due to the approval of new target agents for cytotoxic drugs. Unfortunately, a large percentage of patients present with metastasis at the time of diagnosis or relapse after a few months. The complex molecular heterogeneity of this disease is not completely understood; to date, there is a lack of predictive biomarkers that can be used to select subsets of patients who may respond to target drugs. Only the RAS-mutation status is used to predict resistance to anti-epidermal growth factor receptor agents in patients with mCRC. In this review, we describe approved targeted therapies for the management of metastatic mCRC and discuss new candidate targets on the horizon.

Clinical outcome of patients with chemorefractory metastatic colorectal cancer treated with trifluridine/tipiracil (TAS-102): a single Italian institution compassionate use programme

Background TAS-102 improves overall survival (OS) in patients with metastatic colorectal cancer (mCRC) refractory to standard treatments. However, predictive biomarkers of efficacy are currently lacking. Patients and methods We treated a cohort of 43 chemorefractory mCRC patients treated with TAS-102, in a single institution expanded access, compassionate use programme. We stratified patients in two groups according to number of cycles received (<6 cycles and ≥6 cycles). OS, progression-free survival (PFS) and safety were evaluated. Results Thirteen out of 43 patients (30%) obtained a clinically relevant disease control with TAS-102 therapy. Eleven of them were treated for ≥6 cycles with TAS-102, reaching a median PFS of 7.5 months (95% CI 5.8 to 9.2 months) and a median OS of 11.2 months (95% CI range not reached yet). A trend towards significance (p=0.08) between a good performance status and response to TAS-102 was observed. Further, 7 out of the 11 TAS-102 long-treated patients achieved a clinical benefit from a previous treatment with regorafenib. A significant correlation between regorafenib and TAS-102 clinical efficacy was observed (p=0.008). Six out 13 regorafenib-naïve patients were treated with regorafenib after progression from TAS-102. All these patients achieved SD with a median duration of treatment with regorafenib of 6.1 months (range, 1.6–6.7). Conclusion Patients with mCRC in good clinical conditions, even though having been heavily pretreated with all the available treatment options, could obtain a significant clinical benefit from treatment with TAS-102. Moreover, a previous clinical benefit obtained with regorafenib is potentially predictive of clinical efficacy of subsequent TAS-102 treatment.