The investigators evaluated the incidence of BRCA loss in patients with advanced gastric cancer and observed the treatment outcome and prognosis according to BRCA loss. And the investigators evaluated the possibility of BRCA loss as a predictive and prognostic factor.

Stomach cancer is still the leading cause of cancer deaths globally and is reported to be the second leading cause of cancer deaths in Korea (18.7%). Although the number of radical resection has increased due to the development of early diagnosis, many patients experience recurrence after radical resection. It is also diagnosed as a non - resectable disease locally advanced at the time of initial diagnosis, or with a metastasis. In patients with recurrent / metastatic gastric cancer, conventional palliative chemotherapy is the best treatment, and in advanced gastric cancer, combination therapy with fluoropyrimidine (fluorouracil, capecitabine, S1) and platinum (oxaliplatin, cisplatin). The progression-free survival was 3-5 months, and overall survival of 6-10 months in metastatic gastric cancer patients.

The investigators evaluated the incidence of BRCA loss in patients with advanced gastric cancer and observed the treatment outcome and prognosis according to BRCA loss. And the investigators evaluated the possibility of BRCA loss as a predictive and prognostic factor.

Inclusion Criteria:

• Metastatic gastric cancer( Adenocarcinoma)
• Eastern Cooperative Oncology Group (ECOG) performance 0-2
• one more measure lesion
• White blood cell count (WBC) > 3000/ul , Platelet > 75,000/ul
• Normal kidney function (serum creatinine < 1.5 ULN)
• Normal Liver function (Aspartate aminotransferase (AST)/ Alanine aminotransferase (ALT) < 3 times of upper normal limit, if liver metastasis, AST/ALT < 5 times of upper normal limit)
• life expectancy is more than 3 months
• Conventional surgery that does not cause the transformation of the target lesion is allowed
• The patient who voluntarily decided to participate in this study and agreed in writing

Exclusion Criteria:

• Her-2 positive advanced gastric cancer
• Central nervous system metastases requiring treatment with symptoms
• Major uncontrolled cardiovascular disease (including myocardial infarction and congestive heart failure within 6 months)
• Uncontrolled infection or other serious diseases
• Patients with serious medical conditions or serious illnesses
• Patient who is pregnant or lactating
• Adjuvant chemotherapy before 6 months (patients who have not received platinum-based chemotherapy even if they are 6 months old can register)
• In the past, if the primary lesion or target lesion was treated with radiation (if the recurred lesion is outside the range of radiation therapy)