328 Background: Stereotactic Body Radiation Therapy (SBRT) is emerging as a possible standard treatment for pancreatic cancer; however, there is limited data to support its efficacy. This study reviews our institution’s experience using SBRT in the treatment of pancreatic cancer (PCA). Methods: Charts of all PCA patients receiving SBRT from January 2010 to June 2013 were retrospectively reviewed. The primary end points were overall survival (OS) and tumor response assessed by RECIST criteria. 95% of the PTV (GTV + 2-3 mm) received a total dose of 20-33 Gy in five fractions (4-6.6 Gy/fraction), with up to 20% heterogeneity allowed. Pre- and post-SBRT chemotherapy regimens included gemcitabine, cisplatin, FOLFIRINOX, 5-FU or paclitaxel. Results: 84 patients received SBRT, with a median follow-up time of 15.3 months. Median age was 66.5 years, 57.1% were male and 65.5% had head tumors. 66 patients received definitive SBRT for locally advanced or borderline resectable PCA, 4 patients were treated with adjuvant SBRT, and 14 received SBRT for treatment of recurrent disease. Median OS from the date of diagnosis for patients receiving definitive radiation was 17.8 mos (95% CI 14.9-20.9).For recurrent patients the median OS from first day of SBRT was 11.8 mos (95%CI 8.3-15.3). In the definitive SBRT group, among patients who were alive and had follow-up scans, the 6 and 12 month local control rate (stable or partial response) based on RECIST criteria was 84.6% and 81.8%, respectively. Five patients underwent surgery following SBRT and all had negative resection margins. Acute toxicity was minimal with most experiencing grade 1 or 2 fatigue and no grade 3/4 acute toxicity. Late grade 3/4 GI toxicity was seen in 5% (4/84) and 1 patient had a grade 5 GI bleed due to direct tumor invasion into the duodenum. Conclusions: Our early results using SBRT in the definitive and recurrent settings show favorable local control, toxicity, and survival when compared to historical outcomes using chemoradiation. Acute and late toxicity was minimal however the optimal dose and fractionation as well as normal tissue dose constraints need to be determined. Integration of SBRT with more aggressive chemotherapy may result in improved outcomes in patients with PCA.
Dosimetric Predictors of Local Control After Stereotactic Body Radiation Therapy of Locally Advanced Pancreatic Ductal Adenocarcinoma