Stereotactic body radiotherapy for resectable pancreatic ductal adenocarcinoma in patients unfit for surgical resection: A single-institution experience.

Abstract

715 Background: Approximately 1 in 5 patients with pancreatic ductal adenocarcinoma (PDAC) present with surgically resectable disease. Many patients are elderly at diagnosis, and coexisting medical comorbidities can limit surgical eligibility. Although surgery remains the only curative option for PDAC, stereotactic body radiotherapy (SBRT) may be offered to patients who are medically inoperable. However, data on the outcomes with this approach are limited. Here we report disease control, survival, and safety in patients with anatomically resectable but medically inoperable PDAC. Methods: Patients (n=52) were identified from a prospectively maintained database. All had been evaluated in a multidisciplinary setting by a surgical oncologist specialized in PDAC and deemed anatomically resectable but were medically unfit for or declined surgery. SBRT was delivered in all cases using a linear accelerator and fiducial guidance with BED 10 ranging from 51.3-81.6 Gy (median 79.2 Gy). Clinical data are summarized using descriptive statistics. Survival outcomes and clinical factors associated with overall survival (OS) and local progression-free survival (LPFS) were analyzed using the Kaplan-Meier method. Results: Median age at diagnosis was 83 years (range: 53-89). Medical comorbidity was the most common reason for inoperability (n=31; 59.7%), followed by patient choice (n=17; 32.7%). Median OS from diagnosis was 12.2 months (95%CI: 9.3-15.1). Receipt of induction chemotherapy was associated with improved OS (22.7 vs. 11.4 months; p=0.04). Additionally, high-dose RT was associated with worse OS; patients who received a BED 10 <median had longer OS (16.0 vs. 11.4 months; p=0.050). Local progression occurred in 24 patients (46.1%) with a median LPFS of 11.8 months (95%CI: 10.2-13.4). One patient required admission post-SBRT for a pain flare. Grade ≥3 gastrointestinal toxicity occurred in 7.7% (n=4), including one fatal pancreatic head pseudoaneurysm. Toxicity risk was not related to SBRT dosing regimen. There were 14 total hospital admissions from 11 patients (21.2%) within 90 days of SBRT, most commonly for uncontrolled pain. Conclusions: We report the largest series to date of patients with anatomically resectable PDAC who are ineligible for surgical resection, in which SBRT provided acceptable local control with a high-grade toxicity risk comparable to other reported series. The observed association between lower BED 10 and improved outcomes may be reflective of advances in RT delivery techniques and more effective systemic therapy regimens. Most patients who received a lower BED 10 were treated in later years when use of induction chemotherapy became more common. However, a detrimental effect of dose escalated RT in this population cannot be excluded. Induction chemotherapy should be offered to these patients when feasible.