Carbon-Ion Radiotherapy for Local Recurrence Following Pancreatic Cancer Surgery

Abstract

70% of patients able to receive surgical resection for pancreatic adenocarcinoma may ultimately experience recurrence; 25-35% have disease in the remnant pancreas or tumor bed. Surgical re-resection carries notable risks for morbidity, while success with photon irradiation has been limited. Carbon-ion radiotherapy (CIRT) has demonstrated unique promise in the treatment of locally advanced pancreatic cancer (LAPC). An initial cohort from 2011-2015 was published in 2017; here, we provide an update on CIRT safety and efficacy for post-surgical salvage of locally recurrent pancreatic cancer, with 60 cases from 2007 to 2020.Patients with locoregional recurrence following resection of pancreatic cancer were eligible. CIRT was conducted using 48.0 to 55.2 Gy (RBE) in 12 fractions, delivered over 3 weeks. Inclusion criteria included: 1) unresectable disease due to tumor invasion or patient refusal of re-resection; 2) absence of distant metastasis, 3) ECOG performance of 0 to 2. Patients with disease invading the GI tract, previous radiotherapy, or metallic stent placement were excluded.A total of 60 patients treated between January 2007 and 2020 were retrospectively reviewed. Median age was 65, with pancreatic head primary in 34 cases and body/tail in 26 cases. 34 cases underwent pancreaticoduodenectomy, with 26 distal pancreatectomies. 14 cases recurred in the residual pancreas, while 46 cases recurred in surrounding tissue. 16 cases received 48 - 52.8 Gy (RBE) via dose escalation, with 44 cases receiving 55.2 Gy (RBE). Grade 3 hematologic toxicity was seen in 3 cases, with no other G3+ acute or late toxicity was noted. 2-year local control was achieved in 56% for 48-52.8 Gy (RBE) and 61% for 55.2 Gy (RBE) cohorts. 2-year survival was 48% in the high dose cohort, with median survival time (MST) of 23 months.CIRT for postoperative recurrence of pancreatic cancer compared favorably to conventional chemoradiation salvage (2-year survival 38%, 16-month MST), with acceptable toxicity. CIRT may be a viable treatment alternative when re-resection is difficult.