The Impact of Combined Chemotherapy and Intra-Tumoural Injection of Phosphorus-32 Microparticles on Vascularity in Locally Advanced Pancreatic Carcinoma.

Background: Poor intra-tumoural vascularity contributes to a lack of response to chemotherapy in pancreatic cancers. Preliminary data suggest that the addition of endoscopic ultrasound (EUS)-guided intra-tumoural injection of phosphorus-32 (P) microparticles to standard chemotherapy is potentially beneficial in locally advanced pancreatic cancer (LAPC). We aimed to assess changes in pancreatic tumour vascularity following P implantation, using contrast-enhanced EUS (CE-EUS).

Methods: This was a prospective single-centre trial from January 2022 to 2024 of patients with unresectable, non-metastatic LAPC undergoing standard FOLFIRINOX chemotherapy and P implantation. We performed CE-EUS pre-implantation after two chemotherapy cycles and 4 and 12 weeks after implantation. Time-intensity curves were analysed for 90 s after IV contrast bolus to ascertain peak intensity and intensity gain.

Results: A total of 20 patients underwent P implantation, with 15 completing 12-week follow-up. The technical success of P implantation was 100%. The median primary tumour size reduced from 32 mm (IQR 27.5-38.75) pre-implantation to 24 mm (IQR 16-26) 12 weeks post-implantation ( < 0.001). Five patients (25%) had tumour downstaging, and four underwent resections. The baseline (pre-implantation, post-chemotherapy) median intensity gain of contrast enhancement within the tumour was 32.15 (IQR 18.08-54.35). This increased to 46.85 (IQR 35.05-76.6; = 0.007) and 66.3 (IQR 54.7-76.3; = 0.001) at 4 weeks and 12 weeks post-implantation, respectively. Over a median follow-up of 11.2 months (IQR 7.8-12.8), 15/20 (75%) of patients remained alive, with 3/20 (15%) demonstrating local disease progression. Overall survival was not significantly different between patients with or without an increased intensity of 10 a.u. or more at 12 weeks post-implantation.

Conclusion: This is the first clinical study to demonstrate treatment-induced increased vascularity within pancreatic primary tumours, which followed P implantation and FOLFIRINOX chemotherapy. Larger comparative trials are warranted.