--- title: "What Is Adaptive Radiotherapy? An Evidence-Based Guide | 5D Cancer Services" description: "A plain-language, evidence-based explainer on adaptive radiotherapy (ART): why static radiation plans fall short, online vs offline workflows, CT/CBCT/MRI imaging trade-offs, AI-assisted replanning, and the published outcomes behind shorter hypofractionated courses." canonical: https://www.5dcancerservices.com/adaptive-radiotherapy route: /adaptive-radiotherapy type: article lastUpdated: 2026-06-15 keywords: ["adaptive radiotherapy", "Akesis Gemini 360", "5D Cancer Services", "St. George Utah", "radiation oncology", "what is adaptive radiotherapy", "ART", "online adaptive", "offline adaptive", "CBCT", "image-guided radiation", "hypofractionation", "AI contouring", "plan adaptation"] --- # What Is Adaptive Radiotherapy? An Evidence-Based Guide | 5D Cancer Services > A plain-language, evidence-based explainer on adaptive radiotherapy (ART): why static radiation plans fall short, online vs offline workflows, CT/CBCT/MRI imaging trade-offs, AI-assisted replanning, and the published outcomes behind shorter hypofractionated courses. - HomeTechnologyAdaptive RTClinical DataConditionsInsuranceOur TeamFAQ (435) 900-7060Please do not send Protected Health Information (PHI) by email or voicemail. Standard email is not secure — call us and we will arrange a secure channel.Home - Adaptive RadiotherapyQuick summaryAdaptive radiotherapy (ART) re-images and re-plans the radiation treatment at every session, instead of locking in a single plan at the start. This lets clinicians safely deliver fewer, higher-dose treatments — typically 5 sessions instead of 20–45 — with sub-millimeter targeting accuracy. - Conventional radiation: a single plan delivered 20–45 times - Adaptive radiotherapy: 3D imaging + plan adaptation at every visit - Online vs. offline adaptation: re-planning during the visit vs. between visits - Hypofractionation enabled: 5–15 sessions instead of 20–45 - Strong evidence in prostate, lung, liver, pancreatic, and oligometastatic disease - Delivered at 5D Cancer Services on the Akesis Gemini 360Last reviewed: 2026-05-12 Education Hub # What is adaptive radiotherapy? Adaptive radiotherapy (ART) is an image-guided treatment approach that re-evaluates and updates the radiation plan against the patient's actual anatomy on the day of treatment — rather than treating from a plan made days or weeks earlier. This page is a plain-language, evidence-based introduction to ART: why static plans fall short, how online and offline adaptive workflows differ, the role of CT and CBCT imaging, and the published outcomes that explain why shorter, more precise courses are now becoming standard of care. Watch: what adaptive radiotherapy actually does By the Numbers ## Adaptive radiotherapy by the numbers Three peer-reviewed findings that explain why adaptation matters. ~90%5 of online-adapted fractions change the plan Multi-site CBCT-guided online ART experience: the daily plan is meaningfully different from the original plan in the large majority of fractions. up to ~5×6 fewer significant urinary side effects vs non-adaptive Randomized phase III data of tightly margined, image-guided adaptive prostate SBRT show substantially lower rates of clinically meaningful acute genitourinary symptom flares — with the largest differences seen in patient-reported endpoints — compared to conventionally guided treatment. 2–57 sessions can replace 20–35 conventional treatments Hypofractionated stereotactic regimens (e.g., 5-fraction prostate SBRT) reach cancer-control outcomes comparable to conventional 20–39 fraction courses. Numerals refer to the references listed below. Outcomes vary by disease site, technique, and patient factors; figures shown are representative of published trials. The Case for Adaptive ## Why a static plan isn't enough Conventional radiation plans are built once, on a single diagnostic CT, and then delivered unchanged across weeks. The body — and the cancer inside it — does not stay still that long.1,3 ### Tumors shrink and shift Between simulation and the final fraction, head & neck and lung tumors commonly lose 20–40% of their volume, while organs like the bladder, rectum, and uterus move centimeters with daily filling. ### Margins expose healthy tissue Because traditional planning can't see day-to-day anatomy, planners add a planning target volume (PTV) margin around the tumor to account for uncertainty — and that margin is healthy tissue receiving full dose. ### Setup error compounds over weeks Conventional courses run 20–35 fractions over 5–9 weeks. Small daily setup errors and anatomic drift accumulate, eroding the precision the original plan promised. See It in Action Workflows ## Online vs offline adaptive There are two flavors of adaptive radiotherapy in clinical use today. They differ in when the replan happens — and that timing changes how much the plan can react to the patient's day-to-day anatomy.2 ### Offline adaptive Replan between sessions After one or more fractions, the team reviews recent imaging, decides the plan no longer fits the patient's anatomy, and redesigns the plan in the planning system. The patient is treated on the new plan at the next visit. Lower per-fraction time on the couch Uses standard planning workflows Cannot react to today's anatomy Requires offline imaging review and a separate replanning session ### Online adaptive Replan at the moment of treatment The patient is imaged on the treatment couch, the plan is recalculated against today's anatomy, the physician approves the adapted plan, and treatment is delivered — all in one visit, before the patient gets up. Plan reflects today's tumor and organs Smaller margins, lower healthy-tissue dose No need to reschedule for replanning Longer time on the couch per fraction Requires automation and an integrated imaging + planning workflow The Akesis Gemini360RT we operate at 5D Cancer Services delivers online adaptive treatment — your plan is recalculated against your anatomy at every fraction, before a single beam fires. Imaging ## The role of imaging Adaptive radiotherapy is only as good as the picture it's reacting to. Different modalities make different trade-offs between speed, detail, and where in the workflow they live.3 Planning ### CT simulation Sets up the original treatment plan A high-resolution CT scan acquired days before treatment begins. Provides the electron-density information physicists need to compute dose, but represents a single moment in time. Accurate dose computation Excellent bone and gross-anatomy detail Acquired once, before fractions begin Cannot react to daily change Daily on-board imaging ### CBCT (cone-beam CT) What we use at 5D for daily adaptation A 3D scan acquired in the treatment room with the patient in treatment position, immediately before the beam is delivered. Modern CBCT supports automated contouring and online replanning. Same room, same setup, same fraction Visualizes soft tissue, bladder/rectal filling, and tumor position daily The on-board imaging modality on our Gemini360RT Lower soft-tissue contrast than diagnostic MRI Soft-tissue contrast (industry option) ### MRI Best soft-tissue contrast — used by MR-Linac systems Some adaptive systems integrate MRI directly into the treatment room (an MR-Linac) for the highest soft-tissue contrast. We do not operate an MR-Linac; this is included for educational comparison only. Superior soft-tissue contrast No ionizing radiation for the imaging itself Longer acquisition and workflow times Limited availability and significantly higher cost Not part of the Gemini360RT we use at 5D MRI is included for context only. The Gemini360RT we operate uses onboard CBCT for daily image guidance and adaptation — we do not offer MR-Linac treatment. Automation ## How AI makes online adaptation possible Online adaptation only works when contouring, dose calculation, and plan QA happen fast enough to keep the patient on the table. Modern AI-driven workflows have collapsed those steps from hours to minutes.5 ### Automated contouring Deep-learning models propose contours of the tumor and surrounding organs on the daily image in seconds, not the 20–60 minutes a manual recontour would take. Physicians review and approve, but they no longer start from a blank slate every fraction. ### On-couch replanning Rapid dose calculation and plan re-optimization compress a process that historically took hours into minutes — short enough to keep the patient on the treatment table for a single, adapted session. ### Quality assurance built in Independent dose checks and automated plan-quality metrics run in the background, so the adapted plan that reaches the beam has been verified before a single monitor unit is delivered. ## What this means for patients When the plan reflects today's anatomy instead of last month's, the dose actually delivered to the tumor goes up and the dose to surrounding healthy organs goes down. Multiple peer-reviewed analyses show that the majority of adapted fractions change the plan in clinically meaningful ways — confirming that the static plan was, in fact, drifting.5 That precision is what unlocks hypofractionation: replacing 20–35 daily treatments with a much smaller number of larger, highly targeted doses. Phase III trials in prostate cancer have shown that 5-fraction stereotactic courses achieve cancer-control outcomes comparable to conventional fractionation, with similar or lower acute toxicity.7 And when adaptive precision is used to tighten margins further, randomized data show meaningful drops in side effects — for example, the MIRAGE trial reported a roughly half-rate of significant acute genitourinary toxicity with daily-adapted, image-guided prostate SBRT compared to a conventionally guided arm.6 The MIRAGE trial used MR-guided adaptive SBRT. We cite it because it is the strongest published evidence that tighter, image-guided adaptation reduces side effects — not to imply we operate an MR-Linac. Our adaptation at 5D is delivered with onboard CBCT. ## References & further reading All citations link to the original peer-reviewed source. This page is educational and does not constitute medical advice; please consult our team or your physician for personalized care. - 1.Heukelom J, Fuller CD. Head and Neck Cancer Adaptive Radiation Therapy (ART): Conceptual Considerations for the Informed Clinician. Semin Radiat Oncol. 2019;29(3):258–273.doi.org/10.1016/j.semradonc.2019.02.008 - 2.Green OL, Henke LE, Hugo GD. Practical Clinical Workflows for Online and Offline Adaptive Radiation Therapy. Semin Radiat Oncol. 2019;29(3):219–227.doi.org/10.1016/j.semradonc.2019.02.004 - 3.Sonke JJ, Aznar M, Rasch C. Adaptive Radiotherapy for Anatomical Changes. Semin Radiat Oncol. 2019;29(3):245–257.doi.org/10.1016/j.semradonc.2019.02.007 - 4.Heijkoop ST, Langerak TR, Quint S, et al. Clinical Implementation of an Online Adaptive Plan-of-the-Day Protocol for Nonrigid Motion Management in Locally Advanced Cervical Cancer IMRT. Int J Radiat Oncol Biol Phys. 2014;90(3):673–679.doi.org/10.1016/j.ijrobp.2014.06.046 - 5.Sibolt P, Andersson LM, Calmels L, et al. Clinical implementation of artificial intelligence-driven cone-beam computed tomography-guided online adaptive radiotherapy in the pelvic region. Phys Imaging Radiat Oncol. 2021;17:1–7.doi.org/10.1016/j.phro.2020.12.004 - 6.Kishan AU, Ma TM, Lamb JM, et al. Magnetic Resonance Imaging-Guided vs Computed Tomography-Guided Stereotactic Body Radiotherapy for Prostate Cancer: The MIRAGE Randomized Clinical Trial. JAMA Oncol. 2023;9(3):365–373.doi.org/10.1001/jamaoncol.2022.6558 - 7.Brand DH, Tree AC, Ostler P, et al. Intensity-modulated fractionated radiotherapy versus stereotactic body radiotherapy for prostate cancer (PACE-B): acute toxicity findings from an international, randomised, open-label, phase 3, non-inferiority trial. Lancet Oncol. 2019;20(11):1531–1543.doi.org/10.1016/S1470-2045(19)30569-8 ## Want to see what adaptive looks like for your case? Our team in St. George reviews diagnostic imaging and pathology to determine whether adaptive radiotherapy is appropriate. Most consultations are scheduled within a week. [Call (435) 900-7060](tel:+14359007060)[Email info@5dcancerservices.com](mailto:info@5dcancerservices.com) Please do not send Protected Health Information (PHI) by email or voicemail. Standard email is not secure — call us and we will arrange a secure channel. [How our Gemini360RT works](/technology)[See real-world clinical data](/clinical-data) Deep Dives by Cancer Type ## Adaptive radiotherapy by cancer type Each cancer presents unique anatomy and motion challenges. Explore how the Akesis Gemini 360 addresses them — with clinical evidence, treatment workflows, and comparisons for your specific diagnosis. [### Prostate Cancer 5 sessions Daily prostate motion from bladder and rectal filling — re-planned at every session. As few as 5 treatments. Full evidence & workflow](/adaptive-radiotherapy/prostate) [### Lung Cancer 3–5 sessions Tumor tracked through each breath cycle, protecting healthy lung tissue. As few as 3–5 treatments. Full evidence & workflow](/adaptive-radiotherapy/lung) [### Liver Cancer 3–5 sessions Daily adaptation tracks the liver through respiratory motion, preserving maximum functional liver tissue. Full evidence & workflow](/adaptive-radiotherapy/liver) [### Gynecologic Cancer 5–25 sessions Online pelvic adaptation accounts for daily bladder and bowel filling, reducing rectal and bladder dose. Full evidence & workflow](/adaptive-radiotherapy/gynecologic) [### Pancreatic Cancer 5–15 sessions Daily replanning around the stomach, duodenum, and bowel enables ablative doses previously impossible to deliver safely. Full evidence & workflow](/adaptive-radiotherapy/pancreatic) ## Learn More [### Our Technology — Akesis Gemini 360 See how the Gemini 360 puts adaptive radiotherapy into practice with onboard CBCT imaging, automated tracking, and per-fraction replanning. Learn more](/technology) [### Adaptive vs. Conventional Radiation Side-by-side comparison of adaptive radiotherapy and conventional, statically-planned radiation. Learn more](/compare/adaptive-vs-conventional-radiotherapy) [### Akesis Gemini 360 vs. Traditional Linac How the Gemini 360 differs from a conventional linear accelerator on imaging, adaptation, and patient experience. Learn more](/compare/gemini360-vs-traditional-linac) [### Clinical Data & Real-World Implementation Case studies and peer-reviewed evidence behind adaptive radiotherapy across head & neck, cervical, prostate, and other disease sites. Learn more](/clinical-data) [### Conditions We Treat Cancers and benign conditions where adaptive radiotherapy meaningfully changes the dose actually delivered to the tumor and to healthy tissue. Learn more](/conditions) Take the next step ## There is no time for cancer. You deserve the most advanced care available. Schedule a consultation with our physicians and staff today to discuss your treatment options. 1308 E 900 South, Unit B, St. George, UT 84790 [Call (435) 900-7060](tel:+14359007060)[Request Consultation](https://www.5dcancerservices.com) Please do not send Protected Health Information (PHI) by email or voicemail. Standard email is not secure — call us and we will arrange a secure channel. 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