Dataset Information

Tumour gene expression predicts response to cetuximab in patients with KRAS wild-type metastatic colorectal cancer.

ABSTRACT:

Background

Although it is accepted that metastatic colorectal cancers (mCRCs) that carry activating mutations in KRAS are unresponsive to anti-epidermal growth factor receptor (EGFR) monoclonal antibodies, a significant fraction of KRAS wild-type (wt) mCRCs are also unresponsive to anti-EGFR therapy. Genes encoding EGFR ligands amphiregulin (AREG) and epiregulin (EREG) are promising gene expression-based markers but have not been incorporated into a test to dichotomise KRAS wt mCRC patients with respect to sensitivity to anti-EGFR treatment.

Methods

We used RT-PCR to test 110 candidate gene expression markers in primary tumours from 144 KRAS wt mCRC patients who received monotherapy with the anti-EGFR antibody cetuximab. Results were correlated with multiple clinical endpoints: disease control, objective response, and progression-free survival (PFS).

Results

Expression of many of the tested candidate genes, including EREG and AREG, strongly associate with all clinical endpoints. Using multivariate analysis with two-layer five-fold cross-validation, we constructed a four-gene predictive classifier. Strikingly, patients below the classifier cutpoint had PFS and disease control rates similar to those of patients with KRAS mutant mCRC.

Conclusion

Gene expression appears to identify KRAS wt mCRC patients who receive little benefit from cetuximab. It will be important to test this model in an independent validation study.

SUBMITTER: Baker JB

PROVIDER: S-EPMC3049558 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundThe anti-EGFR monoclonal antibody cetuximab is used in metastatic colorectal cancer (CRC), and predicting responsive patients garners great interest, due to the high cost of therapy. Mutations in the KRAS gene occur in ~40% of CRC and are a negative predictor of response to cetuximab. However, many KRAS-wildtype patients do not benefit from cetuximab. We previously published a gene expression predictor of sensitivity to erlotinib, an EGFR inhibitor. The purpose of this study was to determine if this predictor could identify KRAS-wildtype CRC patients who will benefit from cetuximab therapy.MethodsMicroarray data from 80 metastatic CRC patients subsequently treated with cetuximab were extracted from the study by Khambata-Ford et al. The study included KRAS status, response, and PFS for each patient. The gene expression data were scaled and analyzed using our predictive model. An improved predictive model of response was identified by removing features in the 180-gene predictor that introduced noise.ResultsForty-three of eighty patients were identified as harboring wildtype-KRAS. When the model was applied to these patients, the predicted-sensitive group had significantly longer PFS than the predicted-resistant group (median 88 days vs. 56 days; mean 117 days vs. 63 days, respectively, p = 0.008). Kaplan-Meier curves were also significantly improved in the predicted-sensitive group (p = 0.0059, HR = 0.4109. The model was simplified to 26 of the original 180 genes and this further improved stratification of PFS (median 147 days vs. 56.5 days in the predicted sensitive and resistant groups, respectively, p < 0.0001). However, the simplified model will require further external validation, as features were selected based on their correlation to PFS in this dataset.ConclusionOur model of sensitivity to EGFR inhibition stratified PFS following cetuximab in KRAS-wildtype CRC patients. This study represents the first true external validation of a molecular predictor of response to cetuximab in KRAS-WT metastatic CRC. Our model may hold clinical utility for identifying patients responsive to cetuximab and may therefore minimize toxicity and cost while maximizing benefit.

Project description:The selection of colorectal cancer patients for anti-epidermal growth factor receptor (EGFR) antibody therapy is based on the determination of their RAS mutation status-a strongly negative predictive factor-since the protein target, EGFR, is not a reliable predictor of therapeutic response. In this study, we revisited the EGFR protein issue using a cohort of 90 patients with KRAS exon2 wild-type colorectal cancer who have been treated with cetuximab therapy. Twenty-nine of these patients had metastatic tissue available for analysis. The level of EGFR protein expression in the patients was determined by immunohistochemistry and evaluated by H-score (HS) methodology. Progression-free survival (PFS) and overall survival (OS) of the patients were determined according to the EGFR-HS ranges of both the primary and metastatic tissues using Kaplan-Meyer statistics. In the case of primary tumors, EGFR scores lower than HS = 200 were associated with significantly longer OS. In the case of metastatic tissues, all levels lower than the EGFR-HS range chosen were associated with significantly longer OS. These results are explained by the fact that metastatic tissues rarely maintained the expression levels of the primary tumors. On the other hand, high EGFR expression levels in either primary tumors or metastatic tissues were associated with multiple metastatic disease. This suggests a negative prognostic role of EGFR expression. However, in a multivariate analysis, one-sidedness remained a strong independent predictive factor of survival. Previous studies demonstrated that the EGFR expression level depends on sidedness. Therefore, a subgroup analysis of the left- and right-sided cases was performed on both primary and metastatic tissues. In the case of metastic tissues, an analysis confirmed a better OS in low EGFR protein-expressing cases than in high EGFR protein-expressing cases. Collectively, these data suggest that EGFR protein expression is another negative predictive factor of the efficacy of cetuximab therapy of KRAS exon2 wild-type colorectal cancer.

Project description:ImportanceSecond-line treatment with chemotherapy plus bevacizumab or cetuximab is a valid option for metastatic colorectal cancer.ObjectiveTo evaluate the progression-free survival (PFS) rate at 4 months with chemotherapy plus bevacizumab vs cetuximab for patients with progression of metastatic colorectal cancer after bevacizumab plus chemotherapy.Design, setting, and participantsA prospective, open-label, multicenter, randomized phase 2 trial was conducted from December 14, 2010, to May 5, 2015. The main eligibility criterion was disease progression after bevacizumab plus fluorouracil with irinotecan or oxaliplatin in patients with wild-type KRAS exon 2 metastatic colorectal cancer. All analyses were performed on the modified intent-to-treat population.InterventionsPatients were randomized to arm A (FOLFIRI [fluorouracil and folinic acid combined with irinotecan] or modified FOLFOX6 [fluorouracil and folinic acid combined with oxaliplatin] plus bevacizumab) or arm B (FOLFIRI or modified FOLFOX6 plus cetuximab); the second-line chemotherapy regimen was chosen according to first-line treatment (crossover).Main outcomes and measuresThe primary end point was the 4-month PFS rate. Secondary end points included safety, objective response rate, overall survival, and PFS.ResultsA total of 132 patients (47 women and 85 men; median age, 63.0 years [range, 33.0-84.0 years]; 74 patients with an Eastern Cooperative Oncology Group performance status of 0, 54 patients with a performance status of 1, and 4 patients with unknown performance status) were included at 25 sites. The 4-month PFS rate was 80.3% (95% CI, 68.0%-88.3%) in arm A and 66.7% (95% CI, 53.6%-76.8%) in arm B. The median PFS was 7.1 months (95% CI, 5.7-8.2 months) in arm A and 5.6 months (95% CI, 4.2-6.5 months) in arm B (hazard ratio, 0.71; 95% CI, 0.50-1.02; P = .06), and the median overall survival was 15.8 months (95% CI, 9.5-22.3 months) in arm A and 10.4 months (95% CI, 7.0-16.2 months) in arm B (hazard ratio, 0.69; 95% CI, 0.46-1.04; P = .08). A central analysis of KRAS (exons 2, 3, and 4), NRAS (exons 2, 3, and 4), and BRAF (V600) was performed for 95 tumor samples. Eighty-one patients had wild-type KRAS and wild-type NRAS tumors.Conclusions and relevanceThe results of the PRODIGE18 (Partenariat de Recherche en Oncologie DIGEstive) study showed a nonsignificant difference but favored continuation of bevacizumab with chemotherapy crossover for patients with wild-type RAS metastatic colorectal cancer that progressed with first-line bevacizumab plus chemotherapy.Trial registrationClinicalTrials.gov identifier: NCT01442649 and clinicaltrialsregister.eu identifier: EUDRACT 2009-012942-22.