1133 - First Clinical Results of Carbon Ion Therapy for Pancreatic Cancer in Taiwan: Insights into Efficacy and Side Effects

Purpose/Objective(s): Pancreatic cancer has a poor prognosis with limited treatment options. Carbon ion radiotherapy (CIRT) offers high relative biological effectiveness (RBE) and precision, making it a promising treatment. This study evaluates the impact of CIRT on survival, hematological and biochemical markers, and treatment-related toxicities in pancreatic cancer patients in Taiwan.

Materials/Methods: This study analyzed the clinical outcomes of CIRT in patients with borderline resectable (BRPC), locally advanced (LAPC), or metastatic pancreatic cancer (MPC) treated at Taipei Veterans General Hospital (Apr 2023–Sep 2024). Patients had histopathologically confirmed pancreatic cancer, excluding those with poor performance status, diffuse metastases, gastrointestinal invasion, or metal implants along the treatment beam path. Dose prescriptions were 60–66 Gy RBE (high-dose) for PET-avid lesions and the tumor-vessel interface, 55.2 Gy RBE (medium-dose) for the primary tumor bed, and 43.2 Gy RBE (low-dose) for subclinical disease, lymphatic drainage, and the neuroplexus, all delivered in 12 fractions. Treatment planning incorporated respiratory-gated imaging and organ-at-risk constraints. Patients were treated in the prone position with raster scanning and image guidance. Clinical outcomes included overall survival (OS), local control (LC), and distant metastasis-free survival (DMFS), analyzed using Kaplan-Meier and Cox proportional hazards models. Toxicities were assessed per CTCAE v4.03. Biomarkers, including CA19-9 and complete blood count (CBC) with neutrophil-to-lymphocyte ratio (NLR), were monitored before, during, and after therapy. Total bilirubin (T.Bil) was assessed post-treatment, with controlled CA19-9 defined as levels = pre-neoadjuvant values. Statistical significance was set at p < 0.05.

Results: Total of 70 patients completed CIRT, with a median follow-up of 9.2 months. The estimated 1-year LC, OS, and DFS rates were 91%, 82.3%, and 43.5%, respectively. The conversion surgery rate was 22% in initially unresectable tumors. Patients with controlled CA19-9 before CIRT had significantly improved OS (p=0.013) and LC (p=0.0013), with a trend toward better DMFS (p=0.077). Metastatic status did not impact OS (p=0.46) or LC (p=0.28). Toxicity analysis showed significant declines in WBC (p<0.001), Hb (p<0.001), and PLT (p<0.05), primarily grade 2, with recovery by 90 days, indicating transient bone marrow suppression. NLR increased significantly (p<0.001), reflecting an acute inflammatory response. GI toxicity was minimal, with most acute events limited to Grade 1 and few Grade =3 toxicities.

Conclusion: CIRT is an effective and well-tolerated treatment for pancreatic cancer, achieving favorable 1-year OS and LC rates. Pre-treatment CA19-9 levels may serve as a predictive biomarker for determining the optimal timing of CIRT and assessing treatment response and prognosis.