The prognosis for pancreatic ductal adenocarcinoma (PDAC) remains poor owing to its aggressive nature and the limited efficacy of current therapies. While immune checkpoint inhibitors (ICIs) have shown promise in various malignancies, their effectiveness in PDAC is substantially low.

One potential strategy to enhance their efficacy is through radiotherapy, which was expected to activate the antitumor immune response by releasing tumor antigens and cytokines, possibly also increasing PD-L1 expression. In the CA209-9KH trial, the safety and efficacy of stereotactic radiotherapy (SRT) followed by nivolumab therapy were evaluated in patients with unresectable non-metastatic PDAC.

Although the study confirmed the safety of this treatment approach, it did not lead to significant long-term benefits. The administration of SRT in this regimen did not overcome the resistance to ICIs observed in PDAC.