2178 - Pilot Study of Respiratory-Gated Stereotactic Body Radiation Therapy for Previously Treated Borderline Resectable, Unresectable, or Recurrent/Residual Adenocarcinoma of the Pancreas or Periampullary Region

Purpose/Objective(s): To prospectively evaluate the safety and preliminary efficacy of linac-based, respiratory-gated stereotactic body radiation therapy (SBRT) in patients with borderline resectable, unresectable, or recurrent/residual pancreatic or periampullary adenocarcinoma previously treated with chemotherapy ± surgery and/or radiation. The primary hypothesis was that acute (=3 months) grade =3 gastrointestinal (GI) and hematologic toxicity rates would be low. Secondary objectives included late toxicity, overall survival (OS), progression-free survival (PFS), metastasis-free survival (MFS), local control, pain response, and quality of life (QOL).

Materials/Methods: Eligible patients were =18 years, Karnofsky >70%, with histologically confirmed pancreatic/periampullary adenocarcinoma <8 cm, no metastatic disease, life expectancy >3 months, adequate organ function, and =2 prior chemotherapy cycles. In this single-center prospective pilot study, Cohort A (prior radiation) received SBRT 5 Gy × 5 fractions; Cohort B (no prior radiation) received 6.6 Gy × 5 fractions. Treatment incorporated fiducial-based image guidance and respiratory motion management. Kaplan–Meier methods estimated OS, PFS, MFS, and local progression. Pain and QOL (FACES, EORTC QLQ-C30) were analyzed using ordinal logistic regression with repeated measures under proportional-odds assumptions. Two-sided a=0.05 was used.

Results: Thirty-six patients were enrolled (median age 66; 83% White; 92% non-Hispanic). Acute grade =3 toxicity was uncommon. Grade 3–5 lymphocyte decrease occurred in 13.9% of cases; other grade =3 events (nausea, bilirubin increase, esophageal infection, INR increase, vomiting) each occurred in 2.8% of cases. No grade 4–5 non-hematologic toxicities were observed. Late grade =3 toxicity was rare, with one case (2.8%) of grade 3 lymphocyte decrease and no other grade =3 late GI events. In Cohort B (n=33), 12-month OS was 48.5% (90% CI 33.7–61.8%), PFS 39.4%, and both MFS and local progression-free survival 48.5%. Pain scores remained low without significant change (p=0.844). QOL was generally stable, with modest increases in fatigue and GI symptoms but no meaningful decline in global health status.

Conclusion: Respiratory-gated SBRT demonstrated an acceptable safety profile with low rates of high-grade acute and late toxicity in heavily pretreated pancreatic and periampullary cancer patients. Despite limitations of single-arm design, small sample size, and heterogeneous prior therapy, 1-year survival and local control outcomes are encouraging and support further multi-institutional study.