SBRT Assisted By Real-Time Tracking And Duodenal Wall Sparing In Unresectable Locally Advanced Pancreatic Cancer

Abstract

The aim of this prospective dose scalation study is to evaluate clinical efficacy and safety of stereotactic body radiotherapy (SBRT) in patients with unresectable locally advanced pancreatic cancer (LAPC) in addition to chemotherapy (CT). From August 2017 to November 2019, 21 patients with a median age of 61 (57-84) with unresectable LAPC received SBRT following CT (Gemcitabine-Abraxane or FOLFIRINOX). All patients had a confirmatory biopsy of pancreatic adenocarcinoma. Nine were located in the pancreatic head, 5 in the uncinate process, 5 in the body and 2 in the tail. All tumors were node negative by CT-scan. SBRT was delivered in 5 consecutive fractions by volumetric arc therapy and IGRT. The study was designed as a dose scalation study in three tiers: 33 Gy (6.6 Gy/fx, 3 patients), 45 Gy (9 Gy/fx, 10 patients) and 50 Gy (10 Gy/fx, 8 patients). Intrafractional tumor tracking with electromagnetic Calypso® beacons implanted in the tumor bed was performed in those receiving ≥45 Gy. Additional duodenal wall sparing was achieved by injecting lipiodol contrast in the duodenum to use it as a visual guide in the cone-beam CT. Toxicity was assessed weekly during the first 3 months of follow-up following CTCAEv4.0. Dose limiting toxicity (DLT) was defined as gastrointestinal grade ≥3 acute toxicity. Clinical outcomes were evaluated by CT-scan/MRI/PET-CT-scan as needed every 3 months. All 21 patients were evaluated until their last visit or death. Follow-up closed February 1st, 2020. Mean follow-up was 10.8 (range, 3-26.2). All but one patient were treated with CT according to protocol and received a median of 6 cycles (range, 3-12) before SBRT and subsequently up to medical decision. Five patients presented grade 1-2 acute toxicities and no grade 3 toxicity was observed at any dose tier. After SBRT, median OS and PFS were 23.6 months and 8.3 months, respectively. Local control was 85% at 12 months. Median FFLP has not been reached. Median OS since diagnosis was 29.8 months. Dose escalation with SBRT assisted by real-time tracking (electromagnetic Calypso® beacons) and duodenal wall sparing is a safe and effective treatment for the management of unresectable LAPC, with high local control and acceptable toxicity. The five-day schedule allows for the completion of CT without interruptions. Given that doses of 50 Gy were not associated with DLT, higher doses should be explored.