Dose Escalation SBRT in Patients with Localized Pancreatic Cancer

Abstract

<h3>Purpose/Objective(s)</h3> Localized pancreatic cancer can benefit from local therapy with radiation therapy (RT); however, such tumors are often radioresistant, making low dose RT not effective. Here, we compare the use of low (<40Gy/5fx) versus high dose (40Gy or more in 5 fractions) stereotactic body radiation therapy (SBRT) in patients with localized pancreatic cancer. <h3>Materials/Methods</h3> We performed a retrospective analysis of patients with borderline resectable (BRPC) or locally advanced pancreatic cancer (LAPC) treated with 5 fraction-SBRT at the University of Texas MD Anderson Cancer Center. Patients were divided into two cohorts: those that were treated with <40Gy/5fx, and those that received 40Gy or more in 5fx. Our main endpoint was local-regional recurrence (LRR) post-SBRT. <h3>Results</h3> A total of 89 patients (42 females, 47 males; median age: 69years) were included in our study: 58 patients (65.2%) were treated with <40Gy, and 31 patients (34.8%) were treated with 40Gy or more. In patients treated with lose dose SBRT, 35 (35/58; 60.3%) had BRPC, and in patients treated with high dose SBRT, 13 (13/31; 41.9%) had BRPC. For patients with BRPC, the 1- and 2-year post-SBRT LRR rates were 20.0% vs 0%, and 28.6% vs 7.7%, for the low vs high dose cohorts, respectively. Those results were not statistically significant on Cox regression (HR: 0.5, 95%CI 0.1-2.1, <i>P</i>=0.32). Moreover, in patients with LAPC, the 1- and 2-year LRR rates were 30.4% vs 16.7%, and 39.1% vs 27.8%, for the low vs high dose cohorts, respectively. Those results were also not statistically significant on Cox regression (HR: 0.8, 95%CI 0.3-2.5, <i>P</i>=0.75). <h3>Conclusion</h3> Escalating SBRT dose in patients with localized pancreatic cancer may lead to improved local control, however larger series are still needed to better assess this effect.