Medically reviewed by Ritchie Stevens, MD, Radiation Oncologist on June 8, 2026.
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Adaptive radiotherapy for pancreatic cancer
The pancreas sits in one of the most challenging neighborhoods in the body — surrounded by the stomach, duodenum, kidneys, and major blood vessels, all of which shift daily based on digestive contents and body positioning. Conventional radiation must use wide margins to account for this uncertainty, limiting the dose that can be safely delivered. Adaptive SBRT on the Akesis Gemini 360 re-images and re-plans at every session, enabling ablative doses that were previously impossible to deliver safely.
Why Pancreatic Cancer needs more than a fixed plan
Pancreatic cancer is one of the most challenging cancers to irradiate precisely. These three factors explain why dose escalation — which improves outcomes — requires adaptive technology to achieve safely.
Crowded anatomical neighborhood
The stomach, duodenum, small bowel, kidneys, and spinal cord lie within millimeters of most pancreatic tumors. These are among the most radiation-sensitive structures in the body. Conventional plans must treat wide margins to compensate for daily position uncertainty — but those margins contain these critical organs.
Daily organ position variability
The stomach and bowel change filling continuously. On any given treatment day, the duodenum may be in a very different position relative to the tumor than it was at simulation — meaning a fixed plan may deliver high dose to the duodenum even when it has shifted away from the target.
Dose limits constrain tumor coverage
Without adaptation, radiation oncologists must keep the total dose low enough to protect the surrounding organs at worst-case positions. This dose compromise limits local control. Adaptive replanning allows dose constraints to be applied to today's anatomy — where the bowel actually is — enabling safe dose escalation.
What the evidence shows
Evidence for SBRT and dose escalation in pancreatic cancer continues to mature, with key studies establishing the relationship between biologically effective dose and survival.
Herman et al.: BED ≥70 Gy improves survival in locally advanced disease
This multi-institutional study of SBRT for locally advanced pancreatic cancer (LAPC) found that delivering a biologically effective dose of ≥70 Gy was associated with improved local control and overall survival. Achieving these dose levels safely requires the kind of adaptive precision the Gemini 360 provides.
doi.org/10.1002/cncr.29161SBRT enables conversion to resectability
Multiple prospective studies have demonstrated that ablative SBRT or chemoradiation can convert borderline resectable pancreatic cancer to surgical candidates in a subset of patients. Patients who proceed to R0 resection after neoadjuvant radiation have significantly better survival than those who receive radiation alone.
doi.org/10.1371/journal.pmed.1000267Reyngold et al.: ablative radiation doses improve survival in inoperable pancreatic cancer
This institutional series from Memorial Sloan Kettering found that ablative radiation therapy (dose-escalated SBRT delivering high biologically effective doses) was associated with significantly improved overall survival compared to standard-dose radiation for patients with inoperable pancreatic cancer. Delivering these ablative doses safely requires the kind of per-fraction adaptive replanning the Gemini 360 provides — adapting each plan around the actual position of the stomach and bowel on that day.
doi.org/10.1001/jamaoncol.2021.0057Your treatment workflow
At 5D Cancer Services, pancreatic adaptive SBRT is planned and delivered with meticulous attention to adjacent organ-at-risk positions — which are re-evaluated at every session before treatment is delivered.
Simulation CT with fasting and bowel preparation
A planning CT is acquired after standardized fasting (typically 2–4 hours). Contrast helps delineate tumor from surrounding vasculature. The radiation oncologist contours the GTV, CTV, and all adjacent organs at risk — stomach, duodenum, small bowel, kidneys, spinal cord, and liver.
Plan optimization with strict OAR constraints
The SBRT plan is optimized to deliver ablative dose to the tumor while maintaining published tolerances for all surrounding structures. OAR constraints are applied as absolute volume limits to prevent duodenal and gastric toxicity.
Daily CBCT imaging and adaptation (sessions 1–5 or more)
Before each session, a CBCT is acquired with the patient in the same fasted state. The Gemini 360 evaluates today's bowel and stomach positions. If a critical organ has shifted into a high-dose region, the plan is adapted to protect it before treatment is delivered.
Surgical reassessment and systemic therapy coordination
For borderline resectable patients, imaging restaging occurs 4–6 weeks after SBRT to assess resectability. The radiation oncology team works closely with surgical oncology to coordinate the neoadjuvant pathway. For locally advanced patients, systemic therapy typically continues after radiation.
Adaptive vs. conventional radiation
| Factor | Adaptive RT (Gemini 360) | Conventional Radiation |
|---|---|---|
| Total sessions | 5–15 sessions over 1–3 weeks | 25–28 sessions over 5–6 weeks |
| Daily imaging | CBCT at every session | Periodic imaging only |
| Bowel position management | Re-planned around today's actual position | Fixed plan — worst-case margins assumed |
| Achievable tumor dose (BED) | Ablative doses possible (BED ≥70 Gy) | Dose limited by fixed bowel margins |
| Duodenal toxicity risk | Reduced via adaptive OAR protection | Higher with static margins |
| Resectability conversion | Possible with ablative doses | Limited with subtherapeutic doses |
Frequently asked questions
Can adaptive SBRT treat inoperable pancreatic cancer?
Yes. Adaptive SBRT is a primary treatment option for locally advanced pancreatic cancer (LAPC) — tumors that surround major blood vessels and cannot be safely resected. The adaptive approach allows delivery of higher, more effective doses than conventional radiation, which may improve local control and in some cases convert the tumor to a resectable state.
Can adaptive radiotherapy help before surgery for borderline resectable disease?
Yes. Neoadjuvant adaptive SBRT — radiation given before attempted surgery — can shrink borderline resectable tumors and improve the chance of achieving clear surgical margins. Some patients who undergo SBRT and then surgery achieve long-term remission. Your multidisciplinary team will review imaging to determine whether neoadjuvant radiation is appropriate.
Why is pancreatic cancer so hard to treat with conventional radiation?
The pancreas is surrounded by the stomach, duodenum, and small bowel — all radiation-sensitive structures that shift position daily. Conventional radiation must keep total dose low to protect these organs at their worst-case positions. Adaptive replanning allows constraints to be applied to where the bowel actually is on that day, enabling safe dose escalation.
What gastrointestinal side effects should I expect?
With adaptive radiotherapy, gastrointestinal side effects are typically milder than with conventional radiation. Some patients experience mild nausea, fatigue, or appetite changes during treatment. Because the Gemini 360 adapts each session's plan around the actual positions of the stomach and bowel, the dose delivered to these structures is minimized.
Educational information — not medical advice
The content on this page is provided for general educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay seeking it because of something you have read on this site. If you think you may have a medical emergency, call your doctor or 911 immediately.
References
- 1.Herman JM, Chang DT, Goodman KA, et al. Phase 2 multi-institutional trial evaluating gemcitabine and stereotactic body radiotherapy for patients with locally advanced unresectable pancreatic adenocarcinoma. Cancer. 2015;121(7):1128–1137. doi.org/10.1002/cncr.29161
- 2.Gillen S, Schuster T, Meyer Zum Büschenfelde C, et al. Preoperative/neoadjuvant therapy in pancreatic cancer: a systematic review and meta-analysis of response and resection percentages. PLoS Med. 2010;7(4):e1000267. doi.org/10.1371/journal.pmed.1000267
- 3.Reyngold M, O'Reilly EM, Varghese AM, et al. Association of Ablative Radiation Therapy With Survival Among Patients With Inoperable Pancreatic Cancer. JAMA Oncol. 2021;7(5):735–738. doi.org/10.1001/jamaoncol.2021.0057
Also see: Adaptive RT by cancer type
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