This study will be a prospective one conducted within a time frame between September 2022 and April 2023. One hundred adult patients already diagnosed with CRC and received bevacizumab and chemotherapy consisting of fluorouracil and leucovorin or capecitabine in combination with either oxaliplatin (FOLFOX or XELOX) or irinotecan (FOLFIRI or XELIRI). Three to six cycles will be given, and to explore the response to treatment, the Response Evaluation Criteria in Solid Tumors (RECIST) will be used to assess the response.

This study will be a prospective one conducted within a time frame between September 2022 and April 2023. One hundred adult patients already diagnosed with CRC and received bevacizumab and chemotherapy consisting of fluorouracil and leucovorin or capecitabine in combination with either oxaliplatin (FOLFOX or XELOX) or irinotecan (FOLFIRI or XELIRI). Three to six cycles will be given, and to explore the response to treatment, the Response Evaluation Criteria in Solid Tumors (RECIST) will be used to assess the response. It is a standard way to measure how well a cancer patient responds to treatment. It is based on whether tumors shrink, stay the same, or get bigger after there must be at least one tumor that can be measured by CT scans, MRI scans, or PET scan (every 8-12 weeks)where "Complete response" (CR) defined as the disappearance of all tumor lesions, "partial response" (PR) as a reduction of > 30% and they will be stable disease" (SD) as a reduction of < 30% or a growth of < 20% and "progressive disease" (PD) as growth of > 20% or the occurrence of new lesions; all changes will be relative to the baseline imaging. Non-responders are patients with stable disease (SD) or progressive disease (PD). Patients will be separated into three groups:

1. The first group is the responder (Complete response and partial response)
2. The second group is the no responder (progressive disease and stable disease) To explore the association between SNPs and BEV treatments, we will explore the association of VEGFA polymorphisms with BEV's therapeutic efficacy in CRC patients. ORR, DCR, and PFS will estimate the results.

ORR is the Objective response rate Percentage of patients whose disease decreased (Partial response - PR) and/or disappeared (Complete response - CR) after treatment. Disease Control Rate (DCR) is defined as the percentage of patients with advanced or metastatic cancer who have achieved complete response, partial response, and stable disease to therapeutic intervention in clinical trials of anticancer agents, and PFS (progression-free survival is defined as the interval from the date on which treatment with bevacizumab was initiated to tumor progression)

Inclusion Criteria:

• All eligible patients will be age over 18 years old. The risk of colorectal cancer increases with age; 90% of cases are diagnosed in individuals 50 years of age and older.
• Most patients had a performance status (WHO = 0-2), which is a score that estimates the patient's ability to perform certain activities of daily living (ADLs) without the help of others. Performance status (PS) is one of the strongest prognostic factors for survival in metastatic colorectal cancer patients.
• In all cases, the initial tumor site will be the colon.
• Adult patients already diagnosed with metastatic CRC and received bevacizumab and chemotherapy consisting of fluorouracil and leucovorin or capecitabine in combination with either oxaliplatin (FOLFOX or XELOX) or irinotecan (FOLFIRI or XELIRI).
• Chronic disease patients will be involved

Exclusion Criteria:

• Patient received bevacizumab and chemotherapy for inadequate cycles; the adequate cycle should be not less than three cycle
• Patients participating in the study and not receive bevacizumab owing to risk factors for serious adverse events like GI perforation, Wounds that don't heal, Serious bleeding, Severe high blood pressure