A first for radiation oncology: new ASTRO guideline focuses on radiation therapy for gastric cancer

Gastric cancer is the fifth most common cancer worldwide and makes up about 1.5% of all new cancer cases in the U.S. In 2025, over 30,000 American adults will have been diagnosed with gastric cancer. Because symptoms, such as bloating and indigestion, resemble those of more benign conditions, diagnoses are often made at advanced stages.

Treatment typically requires coordination of care across medical, surgical, and radiation experts. For patients with resectable tumors, survival rates have improved with chemotherapy regimens administered before and after surgery. In some instances, radiation therapy is combined with chemotherapy (chemoradiation) to help shrink the tumor before surgery or used as palliative care for patients with inoperable tumors or who opt out of undergoing surgery.

Although treatment guidelines exist for patients with gastric cancer, there have not been publications focusing on the use of radiation therapy in gastric cancer. Earlier this month, the American Society for Radiation Oncology (ASTRO) was the first to publish a guideline specifically outlining the role of radiation therapy in the treatment of gastric cancer. The detailed document was published on November 17, 2025, in ASTRO’s clinical practice journal, Practical Radiation Oncology.

The evidence-based guideline was developed by a multidisciplinary task force made up of medical, surgical, and radiation oncologists as well as a radiation oncology resident, a medical physicist, and a patient representative. Christopher G. Willett, M.D., the Mark W. Dewhirst professor of radiation oncology at Duke University in Durham, NC, is the chair of the expert panel. First author Christopher J. Anker, M.D., professor of radiation oncology at the University of Vermont Cancer Center, is the vice chair.

The guideline addresses recommendations for resectable tumors, locally advanced or metastatic (unresectable) disease, and optimal dosing and best practices for treatment planning and delivery of radiation therapy as definitive treatment or palliative care. The evolving role of perioperative immunotherapy is also discussed.

For patients with resectable gastric cancer, the guideline recommends surgery and a perioperative chemotherapy regimen of fluorouracil, oxaliplatin and docetaxel (FLOT). Presurgical radiation therapy combined with chemotherapy is recommended for patients not eligible for perioperative chemotherapy. The same presurgical chemoradiation regimen may also be used to increase the chance of total tumor removal in patients with borderline resectable tumors.

Radiation therapy can be used at different stages of gastric cancer. For patients who can undergo surgery, chemotherapy before and after surgery with the FLOT regimen is typically recommended. Patients with tumors that are difficult to remove may receive radiation combined with chemotherapy before surgery to shrink the tumor.

After surgery, radiation may be given if the tumor was not fully removed or if the surgery was limited. For patients who cannot have surgery or whose cancer returns, radiation can help control the tumor and relieve symptoms such as pain, bleeding or gastrointestinal blockage. The usual radiation dose is 4500 cGy delivered in 25 treatments.

Patients with unresectable locally advanced or metastatic disease are recommended by task force members to receive palliative radiation therapy to relieve symptoms, such as bleeding, pain, and gastrointestinal obstruction. For those with nonmetastatic disease who opt out of or are not candidates for surgery, the team recommends definitive radiation therapy combined with chemotherapy.

Recommendations from ASTRO’s clinical guideline are based on a systematic review of studies published between January 1, 2001, and June 9, 2025, and developed in collaboration with the Society of Surgical Oncology (SSO), the American Society of Clinical Oncology and the European Society for Radiotherapy and Oncology (ESTRO).