Highlight
- Hypofractionated ablative radiation therapy (A-RT) administered after induction chemotherapy enabled surgical resection in 27% of patients with initially unresectable locally advanced pancreatic cancer (LAPC).
- The two-year overall survival rate was notably higher in patients who underwent resection (54%) compared to unresected cases (31%).
- A-RT did not increase postoperative morbidity and served as effective local disease control even when surgery was not possible.
- Late radiation-related adverse events were manageable, with ascites being the most common complication.
Study Background
Pancreatic cancer remains a formidable oncologic challenge, characterized by aggressive biology and often late presentation. Locally advanced pancreatic cancer (LAPC) is defined by tumor involvement encasing major vascular structures, rendering upfront surgical resection infeasible in most cases. Despite advances in systemic chemotherapy, the optimal local therapy strategy for LAPC remains controversial, with limited data guiding the role of radiation therapy and surgery after tumor downstaging. The lack of randomized trials leaves uncertainty in best practices to maximize survival and quality of life for this population.
Study Design
This phase 2, single-arm, nonrandomized clinical trial was conducted at Memorial Sloan Kettering Cancer Center from June 2018 to April 2024, enrolling 48 patients with histologically confirmed pancreatic adenocarcinoma deemed unresectable after induction chemotherapy. Eligible patients had undergone at least three months of first-line therapy with either modified FOLFIRINOX or gemcitabine plus nab-paclitaxel.
Participants subsequently received hypofractionated ablative radiation therapy (A-RT) at doses of 67.5 Gy in 15 fractions or 75 Gy in 25 fractions concurrently with capecitabine, followed by reevaluation for surgical candidacy. Primary endpoints included the rate of surgical resection and 2-year overall survival. Secondary endpoints evaluated surgical morbidity within 90 days, as well as locoregional progression and distant metastasis incidences over two years.
Key Findings
Among the study cohort, arterial and venous involvement was ubiquitous (98%), indicating significant tumor encasement. Median tumor size was 4.1 cm. Nearly all patients (94%) received mFOLFIRINOX chemotherapy before radiation. After A-RT, 17 patients underwent laparoscopy, and 13 of those proceeded with surgical resection, representing a 27% resection rate from the initial cohort. The majority of resections were pancreaticoduodenectomies (84.6%).
At a median follow-up of three years, the two-year overall survival rate was 38% across the cohort. Patients who underwent resection demonstrated superior survival (54%) compared to those remaining unresected (31%). Local progression rates remained low at 11% and 15% for unresected and resected groups, respectively. However, distant metastasis was common, observed in 73% of patients within two years.
Treatment toxicity was acceptable; no perioperative deaths occurred within 90 days post-surgery. Surgical adverse events were documented in 12 evaluated patients, including four with Clavien-Dindo grade III complications. Radiation-induced grade III or higher acute adverse events occurred in 12.5% of participants, and late grade III or higher events occurred in 26.1%. Ascites was the predominant late radiation-related complication noted in 15.2% of patients.
Expert Commentary
The trial provides encouraging evidence supporting the integration of ablative radiation therapy after induction chemotherapy in LAPC patients with extensive vascular encasement. The ability to convert a subset of initially unresectable tumors to resectable ones underscores the potential of this multimodal approach to improve long-term survival.
Importantly, A-RT was associated with durable local control without increasing postoperative complications, highlighting advances in radiation techniques that enable high-dose delivery while sparing critical structures. The high rate of distant metastases emphasizes the continued need for effective systemic therapies alongside local treatment modalities.
Limitations include the nonrandomized design, single-institution setting, and moderate sample size, which may affect generalizability. Further randomized controlled trials are warranted to establish definitive standards of care and optimize patient selection based on biology and treatment response.
Conclusion
For patients with LAPC demonstrating encasement of major vessels despite induction chemotherapy, hypofractionated ablative radiation therapy offers a promising therapeutic avenue. It facilitates surgical resection in a significant minority, improves two-year survival outcomes, and provides effective local disease control without excess treatment-related morbidity.
This therapeutic strategy represents a compelling option for managing this difficult-to-treat population and merits further prospective evaluation in larger, controlled clinical trials to refine protocols and extend benefits broadly.
Funding and Clinical Trial Registration
The trial was conducted with the support of Memorial Sloan Kettering Cancer Center resources. It is registered under ClinicalTrials.gov Identifier: NCT03523312.
References
1. Reyngold M, Wei AC, O’Reilly EM, et al. Maximal Ablative Irradiation Because of Encasement for Patients With Locally Advanced Pancreatic Cancer: A Nonrandomized Clinical Trial. JAMA Surg. 2026 Jul 29. PMID: 42525419.
2. Hammel P, Huguet F, van Laethem JL, et al. Effect of chemoradiotherapy vs chemotherapy on survival in patients with locally advanced pancreatic cancer controlled after 4 months of gemcitabine with or without erlotinib: the LAP07 randomized clinical trial. JAMA. 2016;315(17):1844-1853.
3. Rose BS, et al. Radiation therapy dose escalation improves survival in patients with unresectable pancreatic adenocarcinoma treated with chemoradiation. Int J Radiat Oncol Biol Phys. 2014;88(4):830-838.
