Ep. 2: Up-Front PD-L1 Testing and Perioperative Immunotherapy in Gastric and GEJ Cancer
Key Points
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Up-front biomarker testing guides perioperative therapy decisions in gastric and gastroesophageal junction (GEJ) adenocarcinoma.
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Dose modifications and therapy adjustments are often needed based on patient frailty, comorbidities, or tolerability.
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Patient education and early recognition of immunotherapy-related toxicities are critical for safe and effective care.
Biomarker-Guided Treatment Decisions
At a Clinical Insights discussion held at an event coinciding with the 2026 American Society of Clinical Oncology Gastrointestinal Cancers Symposium, Rahul Gosain, MD, MBA, of Wilmot Cancer Institute, and Rohit Gosain, MD, of Roswell Park Comprehensive Cancer Center, were joined by Angela Alistar, MD, of Atlantic Health; Steven Maron, MD, MSc, of Memorial Sloan Kettering Cancer Center; Reetu Mukherji, MD, of MedStar Health; and Raji Shameem, MD, of Orlando Health to discuss the importance of up-front biomarker testing in perioperative gastric and GEJ cancer.
Testing for MMR, PD-L1, HER2, and circulating tumor DNA helps clinicians determine who may benefit from immunotherapy alone or combined with chemotherapy. “For all of my patients with gastric cancer, I’m testing MMR, PD-L1, and HER2, as well as claudin 18, often before staging is even complete, so we have this data up front,” Dr. Maron said.
The FDA approval for durvalumab is for all-comers; however, biomarker testing and clinical context allow for individualized risk–benefit discussions, particularly in patients with active autoimmune disease. Many patients are PD-L1 positive, and when autoimmune disease is well controlled, immunotherapy can still be safely administered. This up-front approach ensures tailored treatment while maximizing the potential benefit of perioperative therapy.
Dose Adjustments, Adverse Effect Management, and Patient Partnership
The panelists emphasized that the fluorouracil, leucovorin, oxaliplatin, and docetaxel (FLOT) regimen remains challenging but can be safely combined with durvalumab. Frail patients or those with comorbidities may require dose reductions of 15% to 20% or omission of certain chemotherapy agents while continuing immunotherapy.
Patient-centered care is critical; some patients may prefer to omit chemotherapy entirely postoperatively due to concerns about tolerability or weight loss, whereas others complete the full regimen. It’s important to promptly recognize immunotherapy-related adverse effects, such as inflammation affecting any organ system. “Any new or concerning symptoms, let us know. Early recognition and diagnosis can prevent severity and make a big difference,” Dr. Shameem added.