Five-Fraction Stereotactic Body Radiation Therapy (SBRT) and Chemotherapy for the Local Management of Metastatic Pancreatic Cancer.

Background: The majority of patients with pancreatic cancer are diagnosed with metastatic disease at presentation. Nevertheless, local progression is responsible for up to 30% of deaths and can lead to significant morbidity. As a consequence, further exploration of effective methods of local control and palliation is essential. Stereotactic body radiation therapy (SBRT) is a widely utilized technique for the treatment of localized pancreatic cancer. Here, we report our experience with SBRT and chemotherapy for the local treatment of the metastatic patient population.
Methods: This single institution retrospective review analyzed 20 patients with pathologically diagnosed metastatic adenocarcinoma of the pancreas. All patients underwent fiducial placement under endoscopic ultrasound (EUS) guidance. SBRT was delivered in five fractions to a total dose of 25 to 30 Gy. Patients received concurrent (given within 1 week of the start of SBRT) or sequential chemotherapy. Local tumor control was evaluated using Response Evaluation Criteria in Solid Tumors. Toxicity was graded using Common Terminology Criteria for Adverse Events version 4.03. Local control and overall survival were reported using the Kaplan-Meier method.
Results: Patient median age was 64 years, and the median pre-treatment Eastern Cooperative Oncology Group performance status was 1. All patients received chemotherapy and half of the patients (10 of 20) received concurrent chemotherapy with folinic acid, fluorouracil, and oxaliplatin or fluorouracil, leucovorin, irinotecan, and oxaliplatin. Nearly all patients (19 of 20) received post-SBRT chemotherapy. Median time from pathological diagnosis to SBRT was 3.9 months. The twelve-month local control and overall survival were 43 and 53%, respectively. However, in patients with planning target volume (PTV) targets smaller than the population median, the 12-month local control was 78%. Median time to local progression (17.8 vs. 3.0 months, p = 0.02) and overall survival (24.9 vs. 8.8, p = 0.001) were also significantly improved in this smaller PTV cohort. Though not statistically significant, there was a trend towards improvement in local control (17.8 vs. 4.3 months, p = 0.17) and overall survival (16.7 vs. 9.7 months, p = 0.087) for those who received concurrent versus sequential chemotherapy, respectively. Lastly, there were no reported grade 3-5 late toxicities.
Conclusions: As systemic therapies improve, the local management of pancreatic cancer will become increasingly important. Here, we report significantly improved local control with SBRT of smaller PTV tumors with concurrent chemotherapy. Five-fraction SBRT offers a quick and effective modality of local tumor control with minimal toxicity in the metastatic pancreatic cancer population.