Safety and feasibility of implantable, uni-directional planar low-dose rate (LDR) brachytherapy in borderline resectable pancreatic adenocarcinoma

Abstract

Presenter: Herman Peters MD | VCU Health Background: The treatment of borderline resectable pancreatic adenocarcinoma continues to evolve as promising evidence toward neoadjuvant chemoradiation strategies emerge. These strategies, ultimately, aim to facilitate a R0 resection for patients whose radiographic staging characteristics place them at risk for positive margins. Despite reported R0 rates after neoadjuvant chemoradiation ranging from 70-98%, those patients with positive margins or patients not eligible for surgery after neoadjuvant treatment (40-60%) have significantly decreased survival. A novel technique for delivering radiation therapy to the area at risk for margin positivity at the time of surgery, while eliminating the pitfalls and constraints for a post-operative external beam RT (EBRT) boost could expand surgical candidacy and offer survival benefits to patients with positive margins. This study details our experience with a surgically implantable, uni-directional LDR brachytherapy sheet as a boost to targeted anatomy in patients with pancreatic adenocarcinoma after neoadjuvant chemoradiation. Methods: Patients with a diagnosis of borderline resectable pancreatic adenocarcinoma who underwent neoadjuvant chemoradiation (2017-2019) and had concern for positive margins based on imaging were eligible for treatment with the implantable LDR sheet at the time of surgery. CivaSheet® (CivaTech Oncology) is an FDA-cleared product consisting of a matrix of Pd-103 radioisotopes on a bio-absorbable membrane with a gold shield providing unidirectional radiation exposure. Dose is prescribed to 5mm depth and in this study was between 38-45Gy equivalent dose in 2Gy fractions. Intra-operatively, the sheet is cut to size for the area of concern, plus a 1cm margin, and secured in place with absorbable suture and/or fibrin glue by the surgical oncologist. Outcomes evaluated included procedural time, time to implant the device, procedural complications related to sheet placement, length of hospital stay, post-operative complications, and survival. Results: From March 2017 to December 2018, 7 patients received LDR sheets. Median age was 63.7 (range 51-75) and 5 patients were female. At initial diagnosis, all 7 patients had borderline resectable disease. All patients received neoadjuvant chemotherapy with 4 to 6 cycles of FOLFINIROX followed by concurrent chemoradiation to a dose of 50.4 Gy in 28 fractions prior to surgery and sheet placement. Surgical procedures included 4 pancreaticoduodenectomy (PD) and 3 distal pancreatectomy (DP). 2 PD required venous reconstruction and 1 DP required arterial reconstruction. Mean procedure time was 6hr 51min out of which sheet placement added an average of 15min. Mean hospital stay was 6.1 days. There were no post-operative complications attributable to the sheet placement. Median follow up is 13 months (range 6-25 months). One patient died with local & distant recurrence at 13 months & one patient is alive with local recurrence at 22 months. 5 patients are alive with no evidence of disease. Conclusion: This is the first study to report the safety and feasibility of an implantable, uni-directional, LDR brachytherapy sheet in patients with borderline resectable pancreatic adenocarcinoma. This novel treatment strategy can be implanted safely and efficiently with potential to improve rates of local control & survival.