Early Local Tumour Control and Feasibility of Intratumoral P-32 Microparticle Implantation in Patients with Locally Advanced Pancreatic Cancer: A Prospective Single-Center Observational Cohort Study

Background: Pancreatic cancer is a leading cause of cancer-related mortality. Locally advanced pancreatic cancer (LAPC) remains associated with low resection rates and poor survival despite advances in systemic therapy. Intratumoral Phosphorus-32 (P-32) microparticle implantation is an emerging locoregional brachytherapy approach for unresectable LAPC. Methods: This prospective single-center observational cohort study included patients with unresectable LAPC treated with gemcitabine plus nab-paclitaxel and EUS-guided intratumoral P-32 microparticle implantation. Intratumoral distribution was assessed by SPECT/CT. Tumour response was evaluated according to RECIST 1.1, with local disease control rate (LDCR) assessed at approximately 16 weeks. Adverse events were graded according to CTCAE version 4.0. Results: Seventeen patients underwent P-32 implantation (median age, 70 years; ECOG PS 0–1). SPECT/CT confirmed appropriate intratumoral distribution in all patients, with no implantation-related procedural complications. At 16 weeks, 7/16 evaluable patients (43.8%) achieved partial response and 9/16 (56.2%) had stable disease, resulting in an LDCR of 100% among evaluable patients and 94.1% in the all-treated analysis. Mean target-lesion diameter decreased from 3.4 to 2.8 cm, with a median reduction of 21.4%. CA19-9 decreased by ≥50% in 13/16 evaluable patients (81.2%). Four patients (23.5%) underwent surgical resection, all achieving R0 resection. Adverse events were predominantly grade 1–2; one grade 3 event and no grade 4–5 events occurred. Conclusions: P-32 microparticle implantation combined with systemic chemotherapy was feasible and demonstrated encouraging early local activity with an acceptable safety profile. These findings support further prospective evaluation in larger cohorts.