P-353 Outcomes of phosphorus-32 microparticle intratumoural implantation added to chemotherapy in patients with metastatic pancreatic adenocarcinoma

Metastatic pancreatic adenocarcinoma (mPDAC) has a poor prognosis with 5-year survival rate of 3%. In non-metastatic, unresectable locally advanced cancer (LAPC) patients, endoscopic-ultrasound (EUS)-guided intra-tumoral phosphorus-32 ( 32 P)-microparticles implantation resulted in local disease control [LDCR] (defined as Stable Disease [SD] or better) at 16 weeks (3 months post-implantation) 90.5%. This is the first multicentre analysis P-microparticles patients mPDAC. Patients mPDAC treated chemotherapy and intratumoural (OncoSil™; OncoSil Medical) delivering 100Gy target tumour absorbed dose from 5 centres Australia UK were retrospectively analysed. received PanCO study (metastases identified post-enrolment by PET-imaging) special access scheme. 14 (male: 50%; median age: 64.5 years; ECOG 0/1/2: 21.4%/57.1%/21.4%). Median primary longest diameter [LD] volume 40.5mm 21.8cm 3, respectively. had 3 metastases (range, 1-7) liver (42.9%), lung (35.7%), liver/lung (7.1%), liver/peritoneum (7.1%) lung/peritoneum (7.1%). (FOLFIRINOX [n=4; 1 2 nd -line] gemcitabine/nab-paclitaxel [n=10; -line]). implanted 3.1 initial commencing [baseline], 7 1.1 0.7-2.5 [early cohort]) 4.9 3.6-7.9 [delayed cohort]). Pre-implantation, RECIST response was (14.3%) Partial Response [PR], (35.7%) SD, Progressive [PD] distant PD; 4 (28.6%) no intermediate scan. LDCR post-implantation 100%. Best vs . pre-implantation scan PR, including patient PD pre-implantation, plus 10 (71.4%) SD. The early cohort mean –22.0% (median –25.0%) maximal decrease LD baseline. delayed –30.2% compared to –8.6% –4.2%) One good thus underwent surgical resection (R0 on histology). CA19-9 baseline >35U/mL decreased 856.5U/mL 72U/mL nadir; 6/10 >50% decrease. Site(s) progression were: 57.1% distant, 28.6% local/distant, 7.1% progression; developed (5 30 later). follow-up 35.3 months. Although progression-free (PFS) P-implantation 5.6 (95% CI: 4.3-non-calculable [nc]), PFS longer than (9.4 5.9-nc) 4.3-nc)). From commencement, overall 13.9 12.2-nc) No Grade 4/5 acute toxicities observed; (21.4%) device- procedure-related 1/2 AEs (abdominal pain; nausea; fatigue; dyspepsia) that also attributed chemotherapy. EUS-guided deliver appears safe receiving chemotherapy, encouraging outcomes 100% post-implantation. retrospective highlights potential clinical benefits, particularly survival, metastatic whom are often poor.