Outcomes of phosphorus-32 microparticle intratumoral implantation added to chemotherapy in patients with metastatic pancreatic adenocarcinoma

Background and Aims: Metastatic pancreatic ductal adenocarcinoma (mPDAC) has a 5-year survival rate of 3%. In nonmetastatic, locally advanced pancreatic cancer, the addition to chemotherapy of EUS-guided intratumoral phosphorus-32 (³²P) microparticle implantation has achieved good local disease control. The aim of this study was to report the clinical outcomes of this treatment in patients with mPDAC. Methods: Patients with mPDAC treated with chemotherapy and intratumoral ³²P-microparticles from 5 centers in Australia and the United Kingdom were analyzed retrospectively. Results: Fourteen patients were treated (7 female subjects; median age, 64.5 years; Eastern Cooperative Oncology Group performance status scores 0/1/2, 21.4%/57.1%/21.4%). The median baseline primary tumor longest diameter was 40.5 mm. Patients had a median of 3 metastases (interquartile range, 2.25 to 5) and received either 5-fluorouracil, leucovorin, irinotecan, and oxaliplatin (n = 4) or gemcitabine/nab-paclitaxel (n = 10). ³²P microparticles were implanted at a median 3.1 months from chemotherapy commencement. Local disease control rate at 3 months’ postimplantation was 100%. Primary tumor longest diameter decreased by 25% (interquartile range, –31.4% to –16.7%; P = .008), and serum cancer antigen 19-9 levels declined from 134 U/mL to 66 U/mL (P = .018). Local progression-free survival was 12.2 months (95% CI, 9.0-15.4 months) from chemotherapy commencement and 8.3 months (95% CI, 2.6-16.0 months) from ³²P microparticle implantation. Therapy was associated with improved quality of life, including global health status at 12 weeks’ postimplantation (P = .037). Median overall survival was 13.8 months (95% CI, 10.5-17.1 months) from chemotherapy commencement and 11 months (95% CI, 5.6-17.4 months) from ³²P microparticle implantation. No grade 4/5 acute toxicities were observed. Conclusions: This first multicenter analysis of combined chemotherapy and EUS-guided ³²P microparticle implantation in mPDAC shows the potential clinical benefits of local tumor control in a cohort for whom outcomes are historically poor.