Review Urges Parameter-Specific Radiotherapy to Amplify Immunotherapy Responses in Localized PDAC

The review, coordinated by researchers at Liège University Hospital with collaborators at Gustave Roussy and Fox Chase, examines how conventional 1.8–2 Gy fractions often fail to overcome the dense stroma and immunosuppressive microenvironment of PDAC. It highlights that hypofractionated or stereotactic regimens combined with PD-1/CTLA-4 blockade or KRAS-targeted agents have produced measurable increases in CD8+ T-cell density in window-of-opportunity studies. Sequencing data indicate that delivering radiotherapy 1–3 days before checkpoint inhibitors maximizes MHC-I upregulation while limiting lymphopenia.

Observational cohorts cited in the review report that only 10–15% of localized PDAC patients currently receive immunotherapy outside trials, with objective response rates below 5% when radiotherapy follows standard schedules. The authors note that adaptive trial designs incorporating ctDNA monitoring could enrich for patients whose tumors show radiation-induced interferon signatures, potentially raising response rates above 25% in selected subgroups.

Remaining uncertainties include optimal target volumes that spare draining lymph nodes and the durability of abscopal effects against micrometastases. The review concludes that next-step randomized phase II/III trials must test these parameter-optimized regimens against current standards rather than simply adding immunotherapy to existing radiotherapy protocols.