Abstract B131: Application of proton beam therapy for pancreatic cancer at a single institution
Jacob B. Leary, Christina Snider, Iain MacEwan, Gregory P. BottaAbstract
Background:
There is no standard paradigm for the use of radiation therapy in pancreatic ductal adenocarcinoma (PDAC). It is used on a case-by-case basis in the neoadjuvant, adjuvant, locally recurrent, and metastatic settings. Pancreatic cancer clinical trials traditionally utilize photon-based therapy (PhBT), though an increasing number of patients (pts) are being treated with proton beam therapy (PrBT) due to availability and side effect profile. However, the use of PrBT in PDAC has not yet clearly been established.
Methods:
Electronic medical records were retrospectively reviewed to identify adult pts with pancreatic cancer at the University of California San Diego (UCSD) who were evaluated for PrBT over a 4 year period from 01/01/2021- 08/18/2024 regardless of stage. Median progression-free survival (mPFS) and median overall survival (mOS) were calculated as the time period from the date of PrBT initiation to the date of disease progression or death, respectively.
Results:
Twenty-six total pts with PDAC were identified and referred for PrBT during the study period. The average age was 66.7 ± 9.6 yrs (range 46 – 83 yrs). Fifteen (57%) pts were male. Average follow-up was 12.5 ± 14.2 mos (range 0 – 48 mos). Four pts did not initiate PrBT due to clinical decline, two pts were ineligible due to receipt of prior radiation to the target area, and two pts were lost to follow up before radiation began. Of the 18 evaluable pts, two pts with borderline resectable disease received neoadjuvant concurrent capecitabine and proton therapy; one pt later underwent surgery. Four previously resected patients developed local recurrences and received locoregional PrBT (with concurrent capecitabine in three pts) to the pancreatic tumor and/or tumor bed (mPFS = 13.3 mos, range 1.4 - 21 mo; mOS = 17.6, range 7.3 - 38 mos). Six pts received palliative intent PrBT for symptom control (median OS = 3.0, range 0.63 - 3.1 mos). Six pts received PrBT to oligometastatic sites (defined as ≤ 5 distant lesions; mPFS 11.2 mos; range 1.7 - 21.2 and mOS = 44.5; range 4.5 - 47 mos). All six pts with oligometastatic disease received PrBT directed to liver metastases, and two of these pts received PrBT concurrently with capecitabine. Seven pts (one had received neoadjuvant PrBT, two had received locoregional PrBT to areas of recurrence, and four initially treated with oligometastatic disease) later received additional courses of PrBT to new distant disease sites, including the liver, spleen, lung, and lymph nodes (mOS 38.1 mos, range 11.4 - 47.1 mos)
Conclusions:
In pts with PDAC, PrBT was used in a variety of settings and was directed at multiple disease sites, sometimes in combination with concurrent systemic therapy. PrBT may serve as an important tool in the multimodal management of patients with PDAC, particularly those with oligometastatic disease, who benefit from an individualized approach due to limited disease burden. Ongoing analysis of this group includes toxicity assessment, next generation sequencing, and evaluation of minimal residual disease.
Citation Format:
Jacob B. Leary, Christina Snider, Iain MacEwan, Gregory P. Botta. Application of proton beam therapy for pancreatic cancer at a single institution [abstract]. In: Proceedings of the AACR Conference on Pancreatic Cancer: New Frontiers in Biology and Therapeutic Development; 2026 Sep 25-28; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(18_Suppl_2):Abstract nr B131.