Causes of Death Among Patients With Initially Inoperable Pancreas Cancer After Induction Chemotherapy and Ablative 5-fraction Stereotactic Magnetic Resonance Image Guided Adaptive Radiation Therapy

Purpose: Nearly all patients with pancreatic ductal adenocarcinoma (PDAC) eventually die of progressive cancer after exhausting treatment options. Although distant metastases (DMs) are a common cause of death, autopsy studies have shown that locoregional progression may be directly responsible for up to one-third of PDAC-related deaths. Ablative stereotactic magnetic resonance-guided adaptive radiation therapy (A-SMART) is a novel treatment strategy that appears to improve locoregional control compared with nonablative radiation therapy, potentially leading to improved overall survival.Methods and Materials: A single-institution retrospective analysis was performed of patients with nonmetastatic inoperable PDAC treated between 2018 to 2020 using the MRIdian Linac with induction chemotherapy, followed by 5-fraction A-SMART. We identified causes of death that occurred after A-SMART.Results: A total of 62 patients were evaluated, of whom 42 (67.7%) had died. The median follow-up time was 18.6 months from diagnosis and 11.0 months from A-SMART. Patients had locally advanced (72.6%), borderline resectable (22.6%), or resectable but medically inoperable PDAC (4.8%). All patients received induction chemotherapy, typically leucovorin calcium (folinic acid), fluorouracil, irinotecan hydrochloride, and oxaliplatin (69.4%) or gemcitabine/nab-paclitaxel (24.2%). The median prescribed dose was 50 Gy (range, 40-50), corresponding to a median biologically effective dose of 100 Gy10. Post-SMART therapy included surgery (22.6%), irreversible electroporation (9.7%), and/or chemotherapy (51.6%). Death was attributed to locoregional progression, DMs, cancer-related cachexia/malnutrition, surgery/irreversible electroporation complications, other reasons not due to cancer progression, or unknown causes in 7.1%, 45.2%, 11.9%, 9.5%, 11.9%, and 14.3% of patients, respectively. Intra-abdominal metastases of the liver and peritoneum were responsible for 84.2% of deaths from DMs.Conclusions: To our knowledge, this is the first contemporary evaluation of causes of death in patients with PDAC receiving dose -escalated radiation therapy. We demonstrated that the predominant cause of PDAC-related death was from liver and peritoneal metastases; therefore novel treatment strategies are indicated to address occult micrometastatic disease at these sites. (c) 2022 The Author(s). Published by Elsevier Inc. on behalf of American Society for Radiation Oncology. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).