Clinical Impact of PI3K/BRAF Mutations in RAS Wild Metastatic Colorectal Cancer: Meta-analysis Results

Prognostic and predictive biomarkers for anti-EGFR monoclonal antibody therapy in RAS wild-type metastatic colorectal cancer: a systematic review and meta-analysis

BACKGROUND

RAS mutations affect prognosis in patients with metastatic colorectal cancer (mCRC) and have been identified as strong negative predictive markers for anti-epidermal growth factor receptor monoclonal antibody (anti-EGFR mAb) therapy, but many tumors containing wild-type RAS genes still do not respond to these therapies. Some additional biomarkers may have prognostic or predictive roles, but conclusions remain controversial.

METHODS

We performed a meta-analysis and systematic review of randomized controlled trials comparing anti-EGFR mAb therapy with alternative therapy that investigated the prognostic and predictive impact of additional biomarkers in RAS wild-type (wt) mCRC patients. Hazard ratios (HRs) and 95% confidence intervals (CIs) for progression-free survival (PFS) and overall survival (OS) and odds ratios (ORs) for objective response rate (ORR) were calculated. The prognostic value of biomarkers was investigated by separately pooling HR and OR for different treatment groups in an individual study. The predictive value was assessed by pooling study interactions between treatment effects and biomarker subgroups.

RESULTS

Thirty publications reporting on eighteen trials were selected, including a total of 13,507 patients. In prognostic analysis, BRAF mutations were associated with poorer PFS [HRs = 3.76 (2.47-5.73) and 2.69 (1.82-3.98)] and OS [HRs = 2.66 (1.95-3.65) and 2.45 (1.55-3.88)] in both the experimental and control arms; low miR-31-3p expression appeared to have longer PFS and OS. In terms of predictive effect, a lack of response to anti-EGFR therapy was observed in patients with BRAF mutant tumors (Pinteraction < 0.01 for PFS). Patients with tumors with any mutation in the KRAS/NRAS/BRAF/PIK3CA gene also showed similar results compared with all wild-type tumors (Pinteraction for PFS, OS, and ORR were < 0.01, < 0.01 and 0.01, respectively). While low miR-31-3p expression could predict PFS (Pinteraction = 0.01) and OS (Pinteraction = 0.04) benefit. The prognostic and predictive value regarding PIK3CA mutations, PTEN mutations or deletions, EGFR, EREG/AREG, HER2, HER3, and HER4 expression remains uncertain.

CONCLUSIONS

In RAS wt mCRC patients receiving EGFR-targeted therapy, BRAF mutation is a powerful prognostic and therapy-predictive biomarker, with no effect found for PIK3CA mutation, PTEN mutation or deletion, but the combined biomarker KRAS/NRAS/BRAF/PIK3CA mutations predict resistance to anti-EGFR therapy. Low miR-31-3p expression may have positive prognostic and therapy predictive effects. Evidence on the prognostic and predictive roles of EGFR and its ligands, and HER2/3/4 is insufficient.

Clinical, Pathological and Molecular Insights on KRAS, NRAS, BRAF, PIK3CA and TP53 Mutations in Metastatic Colorectal Cancer Patients from Northeastern Romania

Mutations in RAS, BRAF, PIK3CA, and TP53 are well-established genetic abnormalities in metastatic colorectal cancer (mCRC). However, limited information is available for patients from Eastern Europe, including Romania. In this retrospective analysis, we investigated 104 mCRC patients from the Northeastern region of Romania to determine the frequency, distribution, coexistence, and clinicopathological and molecular correlations of these mutations. TP53 was the most frequently mutated gene (73.1%), followed by KRAS (45.2%) and PIK3CA (6.7%). Patients with KRAS mutant tumors and wild-type TP53 genotype were found to have no personal history of gastrointestinal cancer (p = 0.02, p = 0.007). KRAS mutations in exon 3 were associated with the female gender (p = 0.02) and the absence of lymph node invasion (p = 0.02). PIK3CA mutations were linked to the absence of lymph node invasion (p = 0.006). TP53 mutations were associated with KRAS mutations in exon 2 (p = 0.006), ulcerated histopathologic type (p = 0.04), and G2 differentiation (p = 0.01). It provides novel insights into genetic variations specific to the population from Northeastern Romania, which has been underrepresented in previous studies within Eastern Europe. Furthermore, our findings enable the development of genetic profiles in a developing country with limited access to specialized genetic tests and facilitate comparisons with other populations.

PIK3CA mutation and clinicopathological features of colorectal cancer: a systematic review and Meta-Analysis

Background: There is conflicting evidence regarding the association between PIK3CA mutations and clinicopathological features of colorectal cancer (CRC). We performed a comprehensive meta-analysis investigating the association between PIK3CA mutations and clinicopathological features in CRC, including subgroup analysis of mutations in exons 9 and 20, to elucidate the role of PIK3CA mutations in CRC.Materials and Methods: A detailed literature search was performed within the PubMed, Web of Science, and Embase databases, examining the associations between PIK3CA mutations and demographic characteristics, clinicopathologic parameters, and molecular features in patients with CRC. The odds ratios with 95% confidence intervals were used to estimate the effect of PIK3CA mutations on outcome parameters.Results: Forty-four studies enrolling 17621 patients were eligible for inclusion. PIK3CA mutations were associated with proximal tumor location, mucinous differentiation, KRAS mutations, and microsatellite instability (MSI). Subgroup analysis demonstrated that PIK3CA exon 9 mutations were positively associated with proximal tumor location and KRAS mutations, and negatively associated with BRAF mutations and MSI; exon 20 mutations were associated with proximal tumor location, KRAS mutations, BRAF mutations and MSI.Conclusions: Our findings suggest that overall or exon-specific PIK3CA mutations showed null associations with key clinicopathological parameters, including disease stage and tumor differentiation, indicating that PIK3CA mutations do not predict aggressive clinicopathological characteristics in CRC. As PIK3CA mutations were found to be closely associated with KRAS mutations, their relationship warrants further investigation. Since PIK3CA exon 9 and 20 mutations showed different tendencies with regard to BRAF mutation and MSI status, they may have distinct molecular impacts on CRC.

Prognostic value of the combination of microsatellite instability and BRAF mutation in colorectal cancer

Purpose

The aim of this study was to investigate the prognostic value of the combination of microsatellite instability (MSI) and BRAF V600E mutation in colorectal cancer (CRC).

Materials and methods

We compare the prognosis difference among CRC patients with four subtypes according to MSI and BRAF mutation, ie, microsatellite stable/BRAF wild type (MSS/BRAFwt), MSS/BRAF mutation (MSS/BRAFmut), MSI/BRAFwt, and MSI/BRAFmut, by pooling the previous related reports and public available data sets till December 2017 for the first time.

Results

Twenty-seven independent studies comprising 24,067 CRC patients were included. Meta-analysis suggested that, compared with MSS/BRAFwt subtype, MSS/BRAFmut was associated with shorter overall survival (OS) (N=25, HR = 2.018, 95% CI = 1.706-2.388, P=2.220E-16), while there was a trend of association of MSI/BRAFmut with OS (N=13, HR = 1.324, 95% CI = 0.938-1.868, P=1.096E-01) and no association of MSI/BRAFwt with OS (N=17, HR = 0.996, 95% CI = 0.801-1.240, P=9.761E-01). Compared with MSI/ BRAFwt subtype, MSI/BRAFmut was a poor factor for OS (N=22, HR = 1.470, 95% CI = 1.243-1.740, P=7.122E-06). Compared with MSS/BRAFmut subtype, both MSI/BRAFwt (N=11, HR = 0.560, 95% CI = 0.433-0.725, P=1.034E-05) and MSI/BRAFmut (N=16, HR = 0.741, 95% CI = 0.567-0.968, P=2.781E-02) were favorable for OS. Subgroup analysis revealed similar results in all subgroups except the subgroup of stage IV cancer, in which MSI showed poor effects on OS in BRAF wild-type patients (N=6, HR = 1.493, 95% CI = 1.187-1.879, P=6.262E-04) but not in BRAF-mutated patients (N=5, HR = 1.143, 95% CI = 0.789-1.655, P=4.839E-01). Meta-analysis regression and test of interaction revealed no interaction of MSI with BRAF mutation when evaluating the associations of MSI/BRAF mutation subtypes with OS in CRC.

Conclusion

Among the four subtypes according to MSI and BRAF mutation, MSS/BRAFmut was a poor prognostic factor, while MSS/BRAFwt and MSI/BRAFwt were comparable and favorable and MSI/BRAFmut was moderate in CRC. The combination of MSI/BRAF mutations could facilitate the planning of individualized treatment strategies and prognosis improvement in CRC.

Targeting the PI3K Signalling as a Therapeutic Strategy in Colorectal Cancer

Colorectal cancer (CRC) remains one of the leading causes of cancer mortality worldwide. Regarded as a heterogeneous disease, a number of biomarkers have been proposed to help in the stratification of CRC patients and to enable the selection of the best therapy for each patient towards personalized therapy. However, although the molecular mechanisms underlying the development of CRC have been elucidated, the therapeutic strategies available for these patients are still quite limited. Thus, over the last few years, a multitude of novel targets and therapeutic strategies have emerged focusing on deregulated molecules and pathways that are implicated in cell growth and survival. Particularly relevant in CRC are the activating mutations in the oncogene PIK3CA that frequently occur in concomitancy with KRAS and BRAF mutations and that lead to deregulation of the major signalling pathways PI3K and MAPK, downstream of EGFR. This review focus on the importance of the PI3K signalling in CRC development, on the current knowledge of PI3K inhibition as a therapeutic approach in CRC and on the implications PI3K signalling molecules may have as potential biomarkers and as new targets for directed therapies in CRC patients.