ASCO Provisional Clinical Opinion: KRAS, Cetuximab, and Panitumumab-Clinical Implications in Colorectal Cancer

A New Perspective on the Effectiveness of FDG PET/CT in Predicting KRAS Mutation in Colon Cancer Cases

Aim: The main aim of this study was to evaluate the effectiveness of 18F-fluorodeoxyglucose (18FDG) positron emission tomography/computerized tomography (PET/CT) parameters in predicting the Kristen rat sarcoma viral oncogene(KRAS) mutation status of patients with colon cancer. Materials and Methods: Between April 2013 and December 2020, 79 patients who were diagnosed with colon cancer by colonoscopy underwent staging 18FDG PET/CT with this diagnosis and met all the inclusion criteria were included in this study. Clinical and prognostic features and also imaging (18FDG PET/CT and magnetic resonance imaging) reports of the patients were collected and analyzed retrospectively. Results: KRAS mutation was seen in 32 of patients (40.5%). No significant difference was observed between KRAS mutant and wild-type patients in terms of clinical features (tumor location, findings regarding metastasis, T stage, and tumor differentiation grade in patients who underwent surgery) and overall survival. Progression-free survival was significantly shorter in KRAS mutant patients (p = 0.018). Primary tumor standardized uptake value (SUVmean) was significantly higher in KRAS mutant cases in the whole group (p = 0.024) and in patients in whom KRAS analysis was performed only in the primary lesion (p = 0.036). The cutoff value for predicting KRAS mutation status was 7.01 g/mL (area under the curve [AUC]: 0.650, confidence interval [CI] 95%, 0.56-0.74). Conclusions: When colon and rectal cancer cases were evaluated separately, the primary tumor SUVmean value was significantly higher in KRAS mutant colon cancer cases. However, its effectiveness in predicting KRAS mutation status was low, similar to other parameters in the literature.

Phase I first-in-human study of HLX07, a novel and improved recombinant anti-EGFR humanized monoclonal antibody, in patients with advanced solid cancers

Purpose This study aimed to evaluate the safety and pharmacokinetic (PK) profiles of HLX07, a novel, recombinant, humanized anti-epidermal growth factor receptor (EGFR) antibody, in patients with advanced solid cancers who had failed standard therapy or for whom no standard therapy was available. Methods In this prospective, open-label, Phase I dose escalation study, patients aged ≥18 years (≥20 years for patients in Taiwan) with histologically-confirmed metastatic or recurrent epithelial carcinoma that had no K-RAS or B-RAF mutations were enrolled in a ‘3 + 3’ escalation design. HLX07 was administered weekly by 2-h intravenous infusion at doses ranging from 50 to 800 mg. The primary endpoint was summary listing of participants reporting treatment-emergent adverse events (TEAEs). Secondary endpoints included PK analysis, serum anti-HLX07 antibody assessments and efficacy. Results In total, 19 patients were enrolled between 1 October 2016 and 16 July 2019 to receive HLX07 at doses of 50 (n = 3), 100 (n = 3), 200 (n = 3), 400 (n = 3), 600 (n = 3) and 800 (n = 4) mg per week. All patients experienced at least one TEAE, most commonly fatigue (68.4%), nausea (47.4%), paronychia (31.6%) and vomiting (31.6%). Serious TEAEs were reported in 11 patients but only one serious TEAE (dyspnea in 600 mg cohort) was regarded as possibly related to study treatment. No dose limiting toxicity (DLT) was reported. Systemic exposure to HLX07 increased proportionally with dose. Anti-HLX07 antibodies were not detected in any patients. Conclusion HLX07 was well tolerated (at dose levels up to 800 mg/week) and promising in patients with advanced solid cancers.

Clinical Trial Registration: The study was registered at ClinicalTrials.gov: NCT02648490 (Jan 7, 2016).

Cetuximab in Patients with Breast Cancer, Non-Small Cell Lung Cancer, and Ovarian Cancer Without KRAS, NRAS, or BRAF Mutations: Results from the Targeted Agent and Profiling Utilization Registry (TAPUR) Study

BACKGROUND

The Targeted Agent and Profiling Utilization Registry (TAPUR) Study, a phase II basket study, evaluates anti-tumor activity of commercially available targeted agents in patients with advanced cancers harboring genomic alterations known as drug targets.

OBJECTIVE

With no known genomic targets predictive of sensitivity to cetuximab, cetuximab was evaluated in patients with breast cancer (BC), non-small cell lung cancer (NSCLC), and ovarian cancer (OC), without KRAS, NRAS, or BRAF mutations.

PATIENTS AND METHODS

Eligible patients with advanced BC, NSCLC, and OC received a cetuximab loading dose, then weekly infusions (250 mg/m2 over 60 min). A Simon two-stage design, requiring ten patients in stage I, was employed per each disease-specific cohort. The primary endpoint was disease control (objective response or stable disease for at least 16 weeks). If two or more patients in stage I achieved disease control, the cohort would enroll 18 more patients in stage II. Power and alpha of the design are 85% and 10%, respectively. Secondary endpoints included progression-free survival, overall survival, and safety.

RESULTS

Patients with BC (n = 10), NSCLC (n = 10), and OC (n = 29) were enrolled between June 2016 and September 2018. No objective responses or stable disease for at least 16 weeks were observed in the BC and NSCLC cohorts. No objective responses and four patients with stable disease for at least 16 weeks were observed in the OC cohort. Six of 49 patients reported grade 3 or higher adverse events or serious adverse events at least possibly related to cetuximab.

CONCLUSIONS

Cetuximab does not have clinical activity in patients with advanced BC, NSCLC, and OC without KRAS, NRAS, or BRAF mutations.

CLINICAL TRIAL REGISTRATION

NCT02693535 (26 February, 2016).

KRAS Testing, Tumor Location, and Survival in Patients With Stage IV Colorectal Cancer: SEER 2010-2013

Purpose:KRAS mutations and tumor location have been associated with response to targeted therapy among patients with stage IV colorectal cancer (CRC) in various trials. This study performed the first population-based examination of associations between KRAS mutations, tumor location, and survival, and assessed factors associated with documented KRAS testing. Methods: Patients with stage IV adenocarcinoma of the colon/rectum diagnosed from 2010 to 2013 were extracted from SEER data. Analyses of patient characteristics, KRAS testing, and tumor location were conducted using logistic regression. Cox proportional hazards models assessed relationships between KRAS mutations, tumor location, and risk of all-cause death. Results: Of 22,542 patients, 30% received KRAS testing, and 44% of these had mutations. Those tested tended to be younger, married, and metropolitan area residents, and have private insurance or Medicare. Rates of KRAS testing also varied by registry (range, 20%-46%). Patients with right-sided colon cancer (vs left-sided) tended to be older, female, and black; have mucinous, KRAS-mutant tumors; and have a greater risk of death (hazard ratio [HR], 1.27; 95% CI, 1.22-1.32). KRAS mutations were not associated with greater risk of death in the overall population; however, they were associated with greater risk of death among patients with left-sided colon cancer (HR, 1.19; 95% CI, 1.05-1.33). Conclusions: This large population-based study showed that among patients initially diagnosed with stage IV CRC, right-sided colon cancer was associated with greater risk of death compared with left-sided cancer, and KRAS mutations were only associated with risk of death in left-sided colon cancer. An unexpected finding was that among patients with stage IV disease, right-sided cancer was more commonly seen in black patients versus whites. Future studies should further explore these associations and determine the role of biology versus treatment differences. In addition, use of KRAS testing is increasing, but there is wide geographic variation wherein disparities related to insurance coverage and rurality may warrant further study.

Factors Associated With Guideline-recommended KRAS Testing in Colorectal Cancer Patients: A Population-based Study

OBJECTIVES

Response to epidermal growth factor receptor inhibitors is poorer among stage IV colorectal cancer (CRC) patients with KRAS mutations; thus KRAS testing is recommended before treatment. KRAS testing was collected by Surveillance, Epidemiology, and End Results (SEER) registries for 2010 CRC cases, and our goal was to provide the first population-based estimates of testing in the United States.

METHODS

SEER CRC cases diagnosed in 2010 were evaluated (n=30,351). χ tests and logistic regression were conducted to determine patient characteristics associated with KRAS testing, stratified by stages I-III versus stage IV. Log-rank tests were used to examine survival by testing status.

RESULTS

KRAS testing among stage IV cases ranged from 39% in New Mexico to 15% in Louisiana. In the model, younger age, being married, living in a metropolitan area, and having primary site surgery were associated with greater odds of receiving KRAS testing. Those who received testing had significantly better survival than those who did not (P<0.0001). Among those who received testing, there was no significant difference in survival by mutated versus wild-type KRAS. Five percent of stage I-III cases received testing.

CONCLUSIONS

Wide variation in documented KRAS testing for stage IV CRC patients exists among SEER registries. Age remained highly significant in multivariate models, suggesting that it plays an independent role in the patient and/or provider decision to be tested. Further research is needed to determine drivers of variation in testing, as well as reasons for testing in stage I-III cases where it is not recommended.

Clinical Pharmacogenetic Testing and Application: Laboratory Medicine Clinical Practice Guidelines

Pharmacogenetic testing for clinical applications is steadily increasing. Correct and adequate use of pharmacogenetic tests is important to reduce unnecessary medical costs and adverse patient outcomes. This document contains recommended pharmacogenetic testing guidelines for clinical application, interpretation, and result reporting through a literature review and evidence-based expert opinions for the clinical pharmacogenetic testing covered by public medical insurance in Korea. This document aims to improve the utility of pharmacogenetic testing in routine clinical settings.

Comparison of KRAS and PIK3CA gene status between primary tumors and paired metastases in colorectal cancer

PURPOSE

In metastatic or recurrent colorectal cancer (MRCRC), the concordance of Kirsten rat sarcoma viral oncogene homolog (KRAS) and phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) mutation status between the primary tumors and metastases is still controversial. The purpose of this study was to evaluate the association between KRAS and PIK3CA mutational status and various clinicopathologic features, and compare their genotype in primary tumors with that of the paired metastatic tumors.

METHOD

We compared the mutation status of KRAS and PIK3CA between the primary tumors and the paired metastases of 59 MRCRC patients with available tissues (resection or biopsy). The presence of KRAS and PIK3CA mutations were determined by direct sequencing analysis.

RESULTS

Seventeen patients (28.8%) had the KRAS mutation and 46 patients (80.0%) had the PIK3CA mutation when considering both the primary and metastatic sites. KRAS mutation was observed in ten primary tumors and eleven related metastases (16.9% vs 18.6%), while PIK3CA mutation was found in 26 primary tumors and 32 related metastases (44.1% vs 54.2%). KRAS status was concordant between primary and metastatic sites in 45 patients (76.3%, kappa =0.157), while the concordance of PIK3CA status was only found in 25 patients (42.4%, kappa =-0.141). The PIK3CA status discordance rate was significantly higher in 40 patients undergoing metachronous resection of primary tumor or metastasis, compared with that in 19 patients with synchronous resection of primary tumor or metastasis (67.5% [27/40] vs 36.8% [7/19]; P=0.026).

CONCLUSION

Our results demonstrate that low concordance of KRAS and high discordance of PIK3CA mutational status exist between the primary tumors and paired metastasis, and these findings remind us to have second thoughts about the need to evaluate metastatic tumors separately rather than only based on the primary tumor data when targeted therapy is considered.

PRMT1-mediated methylation of the EGF receptor regulates signaling and cetuximab response

Posttranslational modifications to the intracellular domain of the EGFR are known to regulate EGFR functions; however, modifications to the extracellular domain and their effects remain relatively unexplored. Here, we determined that methylation at R198 and R200 of the EGFR extracellular domain by protein arginine methyltransferase 1 (PRMT1) enhances binding to EGF and subsequent receptor dimerization and signaling activation. In a mouse orthotopic colorectal cancer xenograft model, expression of a methylation-defective EGFR reduced tumor growth. Moreover, increased EGFR methylation sustained signaling activation and cell proliferation in the presence of the therapeutic EGFR monoclonal antibody cetuximab. In colorectal cancer patients, EGFR methylation level also correlated with a higher recurrence rate after cetuximab treatment and reduced overall survival. Together, these data indicate that R198/R200 methylation of the EGFR plays an important role in regulating EGFR functionality and resistance to cetuximab treatment.

Anti-HER3 Monoclonal Antibody Inhibits Acquired Trastuzumab-Resistant Gynecologic Cancers

BACKGROUND

Antibody resistance, both de novo and acquired, is usually related to high risk of recurrence and lower survival rate in gynecologic cancers. Prevention or reversal of the resistance often yields beneficial clinical results. It was reported that anti-human epidermal growth factor receptor 3 monoclonal antibody was effective against trastuzumab-resistant breast cancer cells. Here in our laboratory, an acquired trastuzumab-resistant ovarian cancer cell line, SKOV3-T, was established previously. Further, human epidermal growth factor receptor 3 was observed to be upregulated in this cell line by microarray detection, suggesting that the antagonist against human epidermal growth factor receptor 3 might be effective to inhibit the resistant cells.

METHODS

We developed an anti-human epidermal growth factor receptor 3 monoclonal antibody, LMAb3, and its affinity to bind human epidermal growth factor receptor 3 was calculated by the Biacore method. Preliminarily, LMAb3's antitumor activity was evaluated in vitro using cell growth/proliferation and clone formation assays in the breast cancer cell line MCF-7. Furthermore, LMAb3 was also evaluated for its inhibitory effect on the carcinogenicity of the SKOV3-T cells, which were induced to overexpress human epidermal growth factor receptor 3, both in vitro and in vivo. The possible underlying signal transduction mechanisms were also identified by Western blot in the MCF-7 and SKOV3-T cells.

RESULTS

LMAb3 was able to inhibit the cell growth/proliferation, clone, and tumor formation both in vitro (in the MCF-7 and SKOV3-T cells) and in vivo. The underlying mechanism of LMAb3 possibly involves inactivation of the HER family proteins (human epidermal growth factor receptor 1, human epidermal growth factor receptor 2, and especially human epidermal growth factor receptor 3) as well as the downstream mitogen-activated protein kinase and protein kinase B pathways.

CONCLUSION

Our work suggests that satisfactory curative effects might be achieved with LMAb3 to treat the trastuzumab-resistant, human epidermal growth factor receptor 3-positive cases of gynecologic cancers.

Analysis of stage and clinical/prognostic factors for colon and rectal cancer from SEER registries: AJCC and collaborative stage data collection system

BACKGROUND

The Collaborative Stage (CS) Data Collection System enables multiple cancer registration programs to document anatomic and molecular pathology features that contribute to the Tumor (T), Node (N), Metastasis (M) - TNM - system of the American Joint Committee on Cancer (AJCC). This article highlights changes in CS for colon and rectal carcinomas as TNM moved from the AJCC 6th to the 7th editions.

METHODS

Data from 18 Surveillance, Epidemiology, and End Results (SEER) population-based registries were analyzed for the years 2004-2010, which included 191,361colon and 73,341 rectal carcinomas.

RESULTS

Overall, the incidence of colon and rectal cancers declined, with the greatest decrease in stage 0. The AJCC's 7th edition introduction of changes in the subcategorization of T4, N1, and N2 caused shifting within stage groups in 25,577 colon and 10,150 rectal cancers diagnosed in 2010. Several site-specific factors (SSFs) introduced in the 7th edition had interesting findings: 1) approximately 10% of colon and rectal cancers had tumor deposits - about 30%-40% occurred without lymph node metastases, which resulted in 2.5% of colon and 3.3% of rectal cases becoming N1c (stage III A/B) in the AJCC 7th edition; 2) 10% of colon and 12% of rectal cases had circumferential radial margins <1 mm; 3) about 46% of colorectal cases did not have a carcinoembryonic antigen (CEA) testing or documented CEA information; and 4) about 10% of colorectal cases had perineural invasion.

CONCLUSIONS

Adoption of the AJCC 7th edition by the SEER program provides an assessment tool for staging and SSFs on clinical outcomes. This evidence can be used for education and improved treatment for colorectal carcinomas.

Anti-IGF-1R monoclonal antibody inhibits the carcinogenicity activity of acquired trastuzumab-resistant SKOV3

Background

Antibody resistance, not only de novo but also acquired cases, usually exists and is related with lower survival rate and high risk of recurrence. Reversing the resistance often results in better clinical therapeutic effect. Previously, we established a trastuzumab-resistant ovarian cancer cell line, named as SKOV3-T, with lower HER2 and induced higher IGF-1R expression level to keep cell survival.

Methods

IGF-1R was identified important for SKOV3-T growth. Then, a novel anti-IGF-1R monoclonal antibody, named as LMAb1, was used to inhibit SKOV3-T in cell growth/proliferation, migration, clone formation and in vivo carcinogenicity.

Results

In both in vitro and in vivo assays, LMAb1 showed effective anti-tumor function, especially when being used in combination with trastuzumab, which was beneficial to longer survival time of mice as well as smaller tumor. It was also confirmed preliminarily that the mechanism of antibody might be to inhibit the activation of IGF-1R and downstream MAPK, AKT pathway transduction.

Conclusion

We achieved satisfactory anti-tumor activity using trastuzumab plus LMAb1 in trastuzumab-resistant ovarian cancer model. In similar cases, not only acquired but also de novo, good curative effect might be achieved using combined antibody therapy strategies.

Anti-epidermal growth factor receptor monoclonal antibody-based therapy for metastatic colorectal cancer: a meta-analysis of the effect of PIK3CA mutations in KRAS wild-type patients

INTRODUCTION

We conducted a meta-analysis to dissect the association between PIK3CA mutations (exon 9 and exon 20) and resistance to anti-epidermal growth factor receptor (EGFR) monoclonal antibodies (MoAbs) in KRAS wild-type metastatic colorectal cancer (mCRC) patients.

MATERIAL AND METHODS

In 11 previously published studies, 864 cancer patients were treated with cetuximab or panitumumab-based therapy. Primary outcomes included objective response (complete response + partial response vs. stable disease + progressive disease), progression-free survival (PFS), and overall survival (OS). We calculated the odds ratio (OR) or hazard ratio (HR) with 95% confidence intervals (CIs) to estimate the risk or hazard. We found consistent and clinically substantial risk or hazard for objective response, PFS, and OS in the cetuximab or panitumumab-treated mCRC patients.

RESULTS

PIK3CA mutations as a whole were associated with reduced response and poor PFS and OS in KRAS wild-type mCRC patients (objective response: OR = 0.42 and 95% CI 0.23-0.75; PFS: HR = 1.54 and 95% CI 1.13-2.09; and OS: HR = 1.4 and 95% CI 1.02-1.91). PIK3CA exon 9 mutations had no effect, whereas exon 20 mutations were associated with a worse outcome compared with wild types, with an OR of 0.21 (95% CI 0.05-0.93).

CONCLUSIONS

PIK3CA mutations as a whole might be useful prognostic factors for assessing clinical outcomes of anti-EGFR MoAb-based chemotherapies in KRAS wild-type mCRC patients. In particular, PIK3CA exon 20 mutations were significantly associated with lack of response.

Genetic and epigenetic biomarkers of colorectal cancer

Cancer is a heterogeneous disease caused, in part, by genetic and epigenetic alterations. These changes have been explored in studies of the pathogenesis of colorectal cancer (CRC) and have led to the identification of many biomarkers of disease progression. However, the number of biomarkers that have been incorporated into clinical practice is surprisingly small. We review the genetic and epigenetic mechanisms of colorectal cancer and discuss molecular markers recommended for use in early detection, screening, diagnosis, determination of prognosis, and prediction of treatment outcomes. We also review important areas for future research.

Systematic review of pharmacogenetic testing for predicting clinical benefit to anti-EGFR therapy in metastatic colorectal cancer

Pharmacogenetic testing can help identify patients with metastatic colorectal cancer more likely to respond to anti-EGFR therapy. We systematically reviewed the benefits and harms of EGFR-related pharmacogenetic testing of molecular targets downstream to KRAS in the treatment of metastatic colorectal cancer. We searched five electronic databases from January 2000 through November 2010, and conducted separate grey literature and conference abstracts searches. Two reviewers independently assessed all articles for relevance and quality. We identified 27 studies, primarily fair- to marginal-quality, small retrospective, and single-arm cohort studies with significant overlap in patient populations. We identified seven studies that studied BRAF in independent patient populations, one that studied NRAS, four that studied PIK3CA, eight that studied PTEN expression, and five that studied AKT expression. The best evidence for BRAF, NRAS, and PIK3CA comes from the largest retrospective study (n=649) of chemorefractory patients from seven European countries. In this study, BRAF mutation was present in 6.5% of KRAS wild-type tumors. Only 8.3% of persons with BRAF mutations, compared to 38% of persons without BRAF mutations (p=0.0012), responded to chemotherapy with cetuximab. Clinical sensitivity and the false positive fraction (1- specificity) were estimated at 9.8% (95% CI 6.3, 14.5) and 1.6% (95% CI 0.2, 5.6), respectively. BRAF mutation was also associated with worse median progression-free survival (absolute difference 18 weeks, p<0.0001), and overall survival (absolute difference 28 weeks, p<0.0001). In the only study comparing outcomes in persons who did (n=227) and did not (n=332) receive cetuximab with combination chemotherapy, those with BRAF mutation had worse survival outcomes regardless of whether or not they received cetuximab. Although NRAS and PIK3CA exon 20 mutations were also associated with worse outcomes compared to persons without these mutations, evidence is based on a small number of identified mutations. Evidence for protein expression of PTEN and AKT is more sparse and limited by variable methods for assessing protein expression. Low-quality evidence addressing clinical validity of pharmacogenetic testing in metastatic colorectal cancer patients suggests that BRAF mutations are associated with poorer treatment response and survival outcomes, although this association may be independent of treatment with EGFR inhibitors.

Predicting response to EGFR inhibitors in metastatic colorectal cancer: current practice and future directions

The identification of KRAS mutational status as a predictive marker of response to antibodies against the epidermal growth factor receptor (EGFR) has been one of the most significant and practice-changing recent advances in colorectal cancer research. Recently, data suggesting a potential role for other markers (including BRAF mutations, loss of phosphatase and tension homologue deleted on chromosome ten expression, and phosphatidylinositol-3-kinase-AKT pathway mutations) in predicting response to anti-EGFR therapy have emerged. Ongoing clinical trials and correlative analyses are essential to definitively identify predictive markers and develop therapeutic strategies for patients who may not derive benefit from anti-EGFR therapy. This article reviews recent clinical trials supporting the predictive role of KRAS, recent changes to clinical guidelines and pharmaceutical labeling, investigational predictive molecular markers, and newer clinical trials targeting patients with mutated KRAS.

Adapting Practice in the Face of New Data

Oncologists are often faced with new information on tests, therapies, and treatment regimens. Determining how to incorporate that data into practice patterns is not easy. Regardless of what motivates you to make a change in practice, the explosion of new oncology data demands that you continually reevaluate how you practice.