Local Control and Survival After Induction Chemotherapy and Ablative Radiation Versus Resection for Pancreatic Ductal Adenocarcinoma With Vascular Involvement

Objective: We sought to compare overall survival (OS) and disease control for patients with localized pancreatic ductal adenocarcinoma (PDAC) treated with ablative dose radiotherapy (A-RT) versus resection. Summary background data: Locoregional treatment for PDAC includes resection when possible or palliative RT. A-RT may offer durable tumor control and encouraging survival. Methods: This was a single-institution retrospective analysis of patients with PDAC treated with induction chemotherapy followed by A-RT [>= 98 Gy biologically effective dose (BED) using 15-25 fractions in 3-4.5 Gy/fraction] or pancreatectomy. Results: One hundred and four patients received A-RT (49.8%) and 105 (50.2%) underwent resection. Patients receiving A-RT had larger median tumor size after induction chemotherapy [3.2 cm (undetectable-10.9) vs 2.6 cm (undetectable-10.7), P < 0.001], and were more likely to have celiac or hepatic artery encasement (48.1% vs 11.4%, P <0.001), or superior mesenteric artery encasement (43.3% vs 9.5%, P < 0.001); however, there was no difference in the degree of SMV/PV involvement (P = 0.123). There was no difference in locoregional recurrence/progression at 18-months between A-RT and resection; cumulative incidence was 16% [(95% confidence interval (CI) 10%-24%] versus 21% (95% CI 14%-30%), respectively (P= 0.252). However, patients receiving A-RT had a 19% higher 18-month cumulative incidence of distant recurrence/progression [58% (95% CI 48%-67%) vs 30% (95% CI 30%-49%), P= 0.004]. Median OS from completion of chemotherapy was 20.1 months for A-RT patients (95% CI 16.4-23.1 months) versus 32.9 months (95% CI 29.7-42.3 months) for resected patients (P < 0.001). Conclusion: Ablative radiation is a promising new treatment option for PDAC, offering locoregional disease control similar to that associated with resection and encouraging survival.