Neoadjuvant SBRT plus regional nodal irradiation with concurrent capecitabine for patients with resectable pancreatic cancer: Survival analysis of prospective phase 1 trial.

652 Background: Radiation may have a role in management of patients with early-stage pancreatic cancer. However, the role of regional nodal irradiation (RNI) is not well defined despite the high frequency of occult nodal disease. The goal of this trial was to evaluate the safety and feasibility of stereotactic body radiation therapy (SBRT) to primary disease with RNI, combined with capecitabine as a neoadjuvant approach for patients with resectable pancreatic cancer. Updated survival analysis will be presented here. Methods: This is a prospective, single institution, phase IA/B dose-escalation trial that enrolled patients with biopsy-proven, resectable, pancreatic adenocarcinoma between 2014 – 2019 (NCT1918644). Patients were enrolled into one of the 3 cohorts with escalating dose levels. Neoadjuvant SBRT to the primary tumor was delivered in 5 fractions of 5, 6, or 7 Gy with concomitant capecitabine. All patients received RNI 5 Gy x 5 fractions. Our initial report found no dose-limiting toxicities (Witt et al IJROBP 2020). Clinicopathologic features were summarized using descriptive statistics. Kaplan-Meier curves were employed for survival analysis. Results: Seventeen patients were enrolled on the protocol with sixteen evaluable (94.1%). Thirteen (76.5%) patients proceeded to surgery. Median follow up was 31.1 months (2.0 – 73.2). Among the evaluable patients, 63% were male, median age at diagnosis was 73 years (63 – 84), pre-treatment CA 19-9 149.5 U/mL (2.0 – 19358.0). The majority of patients had cT2-3 (94%) and cN0 (87.5%) disease. In patients who underwent resection, median time from radiation to surgery was 19.7 days (14.8 – 42.4), with median of 18 lymph nodes removed (11 – 27). Pathologically involved nodes were present in 69.2% of patients with a median of 2 nodes (1 – 10). Five patients (31.3%) received neoadjuvant chemotherapy, and ten (62.5%) received adjuvant chemotherapy. At the time of data cutoff, median overall survival was 31.1 months (2.3 – 73.6), and median locoregional control and distant metastasis free survivals were 32.8 months (4.0 – 59.5) and 15.3 months (0.4 – 73.6), respectively. No further radiation related toxicities were noted since the prior report. Conclusions: Neoadjuvant chemoradiation with SBRT and capecitabine to primary disease with RNI is feasible and provided a promising signal of durable local control in our study, despite high rates of pathological nodal involvement. Further investigation of this strategy is warranted in a larger cohort of patients. Clinical trial information: NCT1918644 .