The 5th edition of the Japanese Gastric Cancer Treatment Guidelines, published in 2018, incorporates new evidence and reflects changes in methodology influenced by the Medical Information Network Distribution Service (MINDS). The guidelines are structured to provide detailed explanations and evidence levels for various treatments, including surgery, endoscopic resection, and systemic chemotherapy. **Surgery:** - **Types and Definitions:** Standard gastrectomy involves resection of at least two-thirds of the stomach with a D2 lymph node dissection. Non-standard gastrectomies include modified and extended surgeries. - **Non-curative Surgery:** Palliative surgery is used to relieve symptoms, while reduction surgery aims to prolong survival or delay symptom onset. - **Resection Margin:** Sufficient margins are recommended for different tumor stages and growth patterns. - **Lymph Node Dissection:** The extent of lymphadenectomy is classified into D1, D1+, and D2 levels, with specific indications for each level. - **Extensive Lymphadenectomy:** Extended lymphadenectomy beyond D2 is considered non-standard and is indicated in specific cases. **Endoscopic Resection:** - **Indications:** Endoscopic resection is indicated for tumors with a very low risk of lymph node metastasis and suitable for en bloc resection. - **Curability Evaluation:** Curability is assessed based on the completeness of tumor removal and the risk of lymph node metastasis. - **Follow-up:** Follow-up with endoscopy and imaging is recommended after curative endoscopic resection. **Systemic Chemotherapy:** - **Indications:** Systemic chemotherapy is indicated for patients with unresectable advanced/recurrent gastric cancer or those who underwent non-curative resection. - **Regimens:** Various chemotherapeutic and molecular targeted agents are used, with "Recommended" and "Conditionally Recommended" regimens listed based on evidence and patient-specific factors. - **First-Line Treatment:** Standard regimens include combinations of fluoropyrimidines and platinum, with specific regimens recommended for HER2-negative and HER2-positive cancers. - **Second-Line Treatment:** Second-line chemotherapy is recommended for patients with sufficient performance status, with specific regimens listed for both first-line and second-line treatments. The guidelines emphasize the importance of individualized treatment decisions and the need for careful consideration of patient-specific factors, including comorbidities and organ function.The 5th edition of the Japanese Gastric Cancer Treatment Guidelines, published in 2018, incorporates new evidence and reflects changes in methodology influenced by the Medical Information Network Distribution Service (MINDS). The guidelines are structured to provide detailed explanations and evidence levels for various treatments, including surgery, endoscopic resection, and systemic chemotherapy. **Surgery:** - **Types and Definitions:** Standard gastrectomy involves resection of at least two-thirds of the stomach with a D2 lymph node dissection. Non-standard gastrectomies include modified and extended surgeries. - **Non-curative Surgery:** Palliative surgery is used to relieve symptoms, while reduction surgery aims to prolong survival or delay symptom onset. - **Resection Margin:** Sufficient margins are recommended for different tumor stages and growth patterns. - **Lymph Node Dissection:** The extent of lymphadenectomy is classified into D1, D1+, and D2 levels, with specific indications for each level. - **Extensive Lymphadenectomy:** Extended lymphadenectomy beyond D2 is considered non-standard and is indicated in specific cases. **Endoscopic Resection:** - **Indications:** Endoscopic resection is indicated for tumors with a very low risk of lymph node metastasis and suitable for en bloc resection. - **Curability Evaluation:** Curability is assessed based on the completeness of tumor removal and the risk of lymph node metastasis. - **Follow-up:** Follow-up with endoscopy and imaging is recommended after curative endoscopic resection. **Systemic Chemotherapy:** - **Indications:** Systemic chemotherapy is indicated for patients with unresectable advanced/recurrent gastric cancer or those who underwent non-curative resection. - **Regimens:** Various chemotherapeutic and molecular targeted agents are used, with "Recommended" and "Conditionally Recommended" regimens listed based on evidence and patient-specific factors. - **First-Line Treatment:** Standard regimens include combinations of fluoropyrimidines and platinum, with specific regimens recommended for HER2-negative and HER2-positive cancers. - **Second-Line Treatment:** Second-line chemotherapy is recommended for patients with sufficient performance status, with specific regimens listed for both first-line and second-line treatments. The guidelines emphasize the importance of individualized treatment decisions and the need for careful consideration of patient-specific factors, including comorbidities and organ function.