KRAS and BRAF Mutations as survival prognostic factors for Metastatic Colorectal Cancer patients after Lung metastasectomy: A Systematic Review and Meta-Analysis

While knowledge has grown extensively regarding the impact of mutations on colorectal cancer prognosis, their role in outcomes after pulmonary metastasectomy (PM) remains minimally understood. Therefore, in this paper, we conduct a systematic review and meta-analysis of retrospective and prospective studies to evaluate whether KRAS or BRAF mutation status can be independent predictors in colorectal cancer patients undergoing complete lung metastasis surgery. A systematic literature review was performed to identify articles reporting overall survival (OS) of patients who underwent lung metastasectomy for colorectal cancer lung metastases (CRLM), stratified according to KRAS and BRAF mutational status. Hazard ratios (HRs) from multivariate analyses were pooled in the meta-analysis. the Based on the random effect model, the total frequency of in 1305 undergone the metastasectomy was 45% and the total these patients was 55.7%. five of reported OS stratified according to KRAS mutation. The pooled analysis revealed that KRAS mutation was negatively associated with OS (HR, 1.674; 95% confidence interval [CI], 1.341-2.089; P < .001). the rate of KRAS mutations were lower in the studies with higher male to female ratio. There was statistically significant linear trend in univariate meta-regression to explain effect size variation by male to female ratio of study with coefficient = 0.47 (95% CI 0.03, 0.91), P = 0.03. disease free survival (DFS), thoracic metastases and origin of primary tumor were significantly influenced by KRAS mutation status. Our meta-analysis confirms the KRAS mutation as a strong and predictive biomarker which makes overall survival lower in patients with colorectal cancer undergoing pulmonary metastasis surgery. Certainly, this interesting evidence represents the first step towards a deeper understanding of the molecular mechanisms underlying tumor behavior and patient outcomes in a subgroup of clinically selected colorectal cancer patients. By considering tumor molecular characteristics and other clinical-pathological factors, our results confirm the use of new therapeutic models to predict outcomes of patients undergoing colorectal lung metastasis surgery and to isolate both systemic and loco-regional treatment strategies. The presence of mutations in the K-RAS gene does not affect survival after resection of pulmonary metastases from colorectal cancer. ISRN


Introduction
Colorectal cancer is the third most common cancer and the second leading cause of cancer deaths in the world. Despite advances in its treatment, colorectal cancer is still one of the leading causes of cancer deaths (1). Reports show that in 25%-30% of patients with metastatic disease, the lung is the most common extra-abdominal metastatic site (2).
Approximately 10%-20% of all patients with colorectal cancer develop pulmonary metastasis during the course of their disease (3,4). Therefore, identifying high-risk patients with pulmonary metastasis is one of the current research areas (5)(6)(7). Pulmonary metastasectomy is an integral part of the interdisciplinary treatment of these patients.
Although randomized, controlled trials on pulmonary metastasectomy have not been performed, resection of metastases via a multidisciplinary treatment program is crucial for selective patients (8,9). Besides, the concept of repeated metastasectomy for recurrent disease leads to long-term treatment in metastatic colorectal cancer (10,11). Predicting the outcome of treatment for patients with recurrent pulmonary metastasis is an obstacle in oncology surgery (12). Prior identification of patients at high risk of pulmonary 4 recurrence may influence the treatment strategy. Therefore, the search for precise biomarkers in pulmonary metastasectomy is increasing (13). Numerous studies have used genetic, familial, and sporadic mutations in the pathogenesis of colorectal cancer.
Besides, the association of these mutations with poorer prognosis has also been demonstrated. One study has found that mutations in RAS genes are independent predictors of overall survival and DFS in patients with colorectal cancer (14). Also, a comprehensive population-based study showed that mutations can increase the risk of mortality (15). Mutations in APC and TP53 tumors may be hereditary especially familial adenomatous polyposis and Li-Fraumeni syndrome but may represent a sporadic process in the development of colorectal cancer (16,17). Like RAS, these two mutated genes are also used in the pathogenesis of colorectal cancer (18)(19)(20). Colorectal cancer patients with liver metastases who have a mutated KRAS gene have been shown to have lower overall survival (OS) and DFS(disease free survival) after liver metastasectomy (21). However, despite all available data from the assessment of the effect of genetic mutations on this disease, the role of these mutations after pulmonary metastasectomy for pulmonary metastases in colorectal cancer is not well understood. Little data are available about the role of KRAS mutations in predicting death after pulmonary metastases, but RAS family mutations have not been fully evaluated (22,23). Therefore, in this paper, we conduct a systematic review and meta-analysis of retrospective and prospective studies to evaluate whether KRAS or BRAF mutation status can be independent predictors in colorectal cancer patients undergoing complete lung metastasis surgery.

Objectives
The purpose of this analysis was to evaluate the status of the KRAS and BRAF mutations in 5 retrospective and prospective studies on patients undergoing radical surgery for colorectal cancer lung metastases. The primary objective was to evaluate overall survival and the secondary objective was to determine the disease-free survival (DFS)

Statistical analysis
This meta-analysis was performed using the inverse-variance method, in which the specific weight of each study was calculated as the standard error square among the studies reviewed. Heterogeneity among studies was assessed using Cochran Q and I 2 statistics. The fixed and random effects were reported.

Literature Search Result
The electronic search provided a total of 1198 results. After screening, 257 were eliminated because they were not in English language and/or duplicates; 684 were excluded because they were reviews, editorial letters, case reports, no full text available or no quality. Further, we excluded 249 articles because they included liver metastases, more than 1 (lung) metastatic site, pathways other than KRAS and BRAF, or were not focused on the effect of KRAS and BRAF mutations after lung metastasectomy as the main 7 topic. At the end of the review process, 9 studies were identified as meeting the inclusion criteria of this review. These articles constitute the study population ( Fig. 1). Study characteristics are shown in Table 1. The Cochrane database of systematic review was then cross-checked to ensure that no similar systematic reviews had been undertaken.   The total number of patients included in these studies was 1726, of whom 41% (787 patients) were KRAS-mutated. The mutation rate of KRAS ranges from 15% to 63%. BRAF mutation was analyzed only in 3 of 9 studies and it occurred in 20 patients (5.7%; Table  1). All patients included underwent macroscopic complete lung metastases resection.

Kirsten Rat Sarcoma Viral Oncogene Homolog (KRAS) Mutational Status and OS
four of 9 studies reported OS after resection of CRC lung metastases, stratified according to KRAS mutation. One study did not perform the multivariate analysis because KRAS status was not significant in the univariate analysis. One study did not provide the OS stratified according to KRAS status, but the multivariate HR of OS according to KRAS status was available. The Three studies for which HRs were available were then pooled in the meta-analysis, which at the end with these constraints included 699 patients. The KRAS mutation rate was 41% ( Figure 3). The pooled analysis, using a fixed effect model, revealed that KRAS mutation was negatively associated with OS (HR, 1.64; 95% CI, 1.12-2.16; P < .001) (Figure 2a). Similarly, using a random effect model, KRAS mutation was negatively associated with OS (HR, 1.64; 95% CI, 1.12-2.16; P < 0.24) (Figure 2a).

B-Viral Oncogene Homolog B1 (BRAF) Mutational Status and OS:
Only 3 of 9 studies analyzed OS stratified according to BRAF mutation. These studies have no provided the HR data of the multivariate analysis regarding OS according to BRAF mutational status. These 3 studies were pooled in a separate meta-analysis.
( Table 1) Meta-regression finding based on the mean of age and frequency of KRAS

mutations:
The studies' meta-regression was according to the association between frequency of KRAS mutations and the mean age of study and the overall rate of KRAS mutations. There was no statistically significant linear trend in univariate meta-regression to explain effect size variation by mean of age of study with coefficient = 0.14 (95% CI -2.17, 2.46), P = 0.88 ( Figure 4a).

Meta-regression finding based on the publication year and frequency of KRAS mutations:
The studies' meta-regression was according to the association between the publication Meta-regression finding based on the male to female ratio of study and frequency of KRAS mutations: The overall rate of KRAS mutations based on the female to male ratio of the studies is showed in (Figure 4-c),the rate of KRAS mutations was lower in studies with higher male to female ratio. There was statistically significant linear trend in univariate meta-regression to explain effect size variation by male to female ratio of study with coefficient = 0.47 (95% CI 0.03, 0.91), P = 0.03.

Sub-group analysis
Comparison of the prevalence of other prognostic factors in WT and mKRAS patients : The overall prevalence of CEA≥5 based on four articles was 53%(95%CI:47%-58% ,

Comparison of OS and DRS between WT and mKRAS patients
The

Discussion
Pulmonary metastasectomy for colorectal cancer is well accepted in the field of thoracic surgery, although due to the lack of comparative data between simple follow-up and 11 surgery, it is still a subject of discussion.  (39,40). In fact, the KRAS mutation has weaker biology and faster onset, and aggressive metastasis, especially in the lungs and bones that challenges clinical decision making (41)(42)(43)(44)(45)(46). In this meta-analysis, we found that in patients whose tumors had a KRAS mutation, overall survival and disease-free survival were lower, with an average KRAS mutation of 41%. Besides, the estimated overall survival was 54 months for the mKRAS (KRAS mutation) patients compared to 66 months for the non-mutated variant.
Also, in line with other studies, the HR was 1.64 )95% confidence interval) and equal to 1.12-2.16 for mKRAS (p < 0.24) which is considered as a negative predictor. However, Zabaleta et al. concluded that the presence of a K-RAS mutation in lung metastases did not affect overall survival, but was associated with a higher rate of pulmonary recurrence (34). Our findings are consistent with two recent meta-analyses. In their meta-analysis, We confirm that we have read the Journal's position on issues involved in ethical publication and affirm that this report is consistent with those guidelines.      Frequency of KRAS mutations and OS based on the country