If you or someone you love is facing a cancer diagnosis, you want a team with deep experience — one that helped write the standards everyone else follows. WashU Medicine radiation oncologists at Siteman Cancer Center were among the first in the country to deliver many of today’s most precise radiation technologies, and they continue to lead the field. At Siteman, you have access to the most advanced external beam radiation options in the Midwest, delivered by specialists focused entirely on your cancer type.
Our Siteman care coordinators – oncology-trained nurses who help with scheduling, finding the right specialist, and guidance – can help you through the process.
Call us directly or submit a form, and we will call you back.
About External Beam Radiation Therapy (EBRT)
External beam radiation therapy (EBRT) uses carefully aimed beams of high-energy radiation to destroy cancer cells from outside the body. Unlike surgically implanted radiation sources, EBRT is delivered by a machine — precisely targeting the tumor while protecting the healthy tissue surrounding it.
What sets Siteman apart is how that precision is achieved. Your care team combines the most advanced imaging available with individualized treatment planning, so every session is built around your cancer — its exact size, location, and biology. No two plans are the same, because no two patients are the same.
Siteman offers the widest range of radiation options in the Midwest, including proton therapy, MRI-guided radiation, IMRT, and SBRT. Whichever approach your team recommends, you will receive care from physicians who helped develop it.
EBRT Options at Siteman
Not all radiation is the same. WashU Medicine radiation oncologists at Siteman offer the full spectrum of external beam radiation technologies — the widest range available in the Midwest. Your care team will recommend the approach, or combination of approaches, best matched to your cancer type, tumor location, stage, and overall health. Here is what each option means for you.
Proton therapy
Proton therapy is one of the most precise forms of radiation available. Unlike traditional X-rays, proton beams deposit the majority of their energy directly at the tumor and then stop — sparing the healthy tissue beyond it from unnecessary radiation exposure. This physical property, called the Bragg peak, makes proton therapy especially valuable for cancers near critical structures such as the spine, brain, heart, or developing organs in children.
Siteman opened the world’s first single-room compact proton therapy facility in 2013 and expanded to a second pencil-beam scanning unit in 2020. A landmark study co-led by WashU Medicine and the University of Pennsylvania found that proton therapy delivers equivalent cure rates to traditional X-ray radiation with significantly fewer serious side effects — including fewer hospitalizations and emergency room visits across nearly 1,500 patients.
Proton therapy is used at Siteman for brain tumors, head and neck cancers, lung cancer, gastrointestinal cancers, and pediatric solid tumors, among others. It is a cornerstone of Siteman Kids’ pediatric cancer program, where protecting growing bodies from radiation’s long-term effects is a clinical priority.
MRI-guided radiation therapy (MRIdian)
In January 2014, Siteman became the world’s first center to treat patients with MRI-guided radiation therapy — a distinction that reflects the depth of experience your team brings to every treatment session.
MRI-guided radiation uses real-time magnetic resonance imaging to visualize the tumor and surrounding anatomy during each treatment. This live imaging allows your radiation oncologist to see exactly where the tumor is as the machine delivers radiation — and to adapt the treatment on the fly if the tumor shifts due to breathing, digestion, or other normal body movement. Conventional radiation systems cannot do this.
The result is a highly personalized treatment that can deliver higher doses to the tumor with greater confidence, while reducing the margin of radiation that must extend into surrounding healthy tissue. Siteman was also the first center to perform adaptive MRI-guided radiation therapy, redesigning each patient’s treatment plan in real time based on that day’s imaging. By 2019, the team had treated more than 1,000 patients and published close to 40 peer-reviewed studies. MRI-guided radiation is particularly effective for pancreatic, liver, prostate, and lung cancers.
Intensity-modulated radiation therapy (IMRT)
Intensity-modulated radiation therapy shapes multiple radiation beams to match the three-dimensional contour of a tumor. Rather than delivering radiation in a single uniform beam, IMRT modulates — or varies — the intensity of dozens of small beam segments from different angles. The result is a dose distribution that conforms tightly to the tumor’s shape, allowing higher and more effective doses to reach the cancer while reducing exposure to the organs and tissue surrounding it.
WashU Medicine radiation oncologists at Siteman were among the first in the United States to deliver IMRT and were the first in St. Louis and the Midwest to offer IMRT alongside 3D treatment planning. The technique is now the national standard of care for prostate cancer and is widely used for head and neck, gynecologic, gastrointestinal, and many other cancer types.
Stereotactic body radiation therapy (SBRT)
Stereotactic body radiation therapy delivers a small number of very high, precisely focused radiation doses to a tumor — typically in one to five sessions, compared to weeks of daily treatment with conventional radiation. SBRT uses advanced imaging and immobilization techniques to target tumors with sub-millimeter accuracy, making it especially effective for small, well-defined tumors in the lung, liver, spine, prostate, and other sites.
WashU Medicine’s Dr. Clifford Robinson leads one of the largest SBRT lung cancer programs in the country and led a Phase III clinical trial directly comparing SBRT to surgery for early-stage non-small cell lung cancer — establishing SBRT as a surgery-equivalent option for patients who cannot tolerate an operation.
WashU radiation oncologists have also co-authored national multi-institutional guidelines on SBRT use for lung cancer, further cementing Siteman’s role in shaping practice standards nationwide.
Stereotactic radiosurgery (SRS)
Stereotactic radiosurgery is a highly precise form of radiation therapy used to treat tumors in the brain and central nervous system. Despite its name, SRS does not involve surgery — it delivers a single, high-dose treatment (or a small number of treatments) using tightly focused beams that converge on a target from many angles. Because the beams overlap precisely at the tumor site and disperse quickly, nearby brain tissue receives a fraction of the dose delivered to the target.
SRS is used at Siteman to treat brain metastases, acoustic neuromas, meningiomas, arteriovenous malformations (AVMs), and select primary brain tumors. It is often used when a tumor is surgically inaccessible, when a patient is not a surgical candidate, or as a follow-up to surgery. Your neurosurgery and radiation oncology teams collaborate closely on every SRS case.
3D conformal radiation therapy (3D-CRT)
Three-dimensional conformal radiation therapy uses CT imaging to create a precise three-dimensional map of the tumor and surrounding structures. Radiation beams are then shaped and aimed from multiple directions to match the contour of the tumor. While IMRT offers even finer dose modulation, 3D-CRT remains an effective and appropriate choice for many tumor types and situations, and serves as a foundation for more advanced techniques.
WashU Medicine’s radiation oncology team has used 3D-CRT for decades and was among the first programs in the region to integrate it with advanced treatment planning systems. Siteman’s depth of experience with 3D-CRT means your team can select the right tool for your cancer with confidence, rather than defaulting to the newest technology when a proven approach is the better fit.
Volumetric modulated arc therapy (VMAT)
Volumetric modulated arc therapy is an advanced form of IMRT in which the radiation machine rotates continuously around the patient in one or more arcs while simultaneously modulating beam intensity, shape, and speed. VMAT delivers highly conformal dose distributions similar to IMRT — but can do so in a fraction of the time, reducing the duration of each treatment session and minimizing the chance that patient movement will affect delivery.
VMAT is used at Siteman for a range of cancer types where rapid, precise treatment delivery is advantageous, including prostate, head and neck, lung, and gynecologic cancers. Shorter treatment sessions also mean greater comfort for patients, particularly those managing pain or limited mobility.
Clinical trials are research studies that help us find new ways to prevent, diagnose, and treat cancer. If you have a rare or complex diagnosis or your treatment path seems uncertain, you might qualify for a clinical trial.
Our team will help you find a study that is right for you. Call us to speak with a Siteman care coordinator.
Why Choose Siteman
A history of being first — and staying ahead
Siteman’s history in radiation spans more than eight decades. From installing the first cyclotron at a U.S. academic medical center, to performing the world’s first MRI-guided radiation treatment, Siteman has been at the forefront of every major advance in the field. Our history is not just a pride point, it means your treatment reflects decades of real-world experience, not a recently adopted protocol.
- 1941 — WashU Medicine receives the first cyclotron installed at a U.S. academic medical center.
- 1963 — Mallinckrodt Institute of Radiology installs one of the country’s first high-energy linear accelerators to treat head and neck cancers.
- 1966 — Carlos Perez, MD, founds the first radiation therapy technologist training program in the United States, a nationally recognized model of excellence.
- 2013 — Siteman opens the world’s first single-room compact proton therapy facility.
- 2014 — Siteman becomes the world’s first center to treat patients with MRI-guided radiation therapy (MRIdian).
- 2020 — A second pencil-beam scanning proton unit expands precision treatment options for patients.
Siteman is also the only cancer center in Missouri to hold the NCI Comprehensive Cancer Center designation — and has earned the NCI’s highest “Exceptional” rating since 2015. Learn more.
Breakthroughs that became the standard of care
WashU Medicine radiation oncologists at Siteman treat cancer and design the trials and publish the research that changes how cancer is treated everywhere.
MRI-GUIDED RADIATION — WORLD FIRST
In January 2014, Siteman became the first center in the world to treat patients with MRI-guided radiation therapy. This approach allows your care team to see the tumor in real time and adapt each treatment to daily changes in your anatomy — something not possible with conventional radiation. By 2019, the team had treated more than 1,000 patients and published close to 40 peer-reviewed studies presented at more than 100 major medical meetings.
PROTON THERAPY — PROVEN FEWER SIDE EFFECTS
A landmark study co-led by WashU Medicine and the University of Pennsylvania — following nearly 1,500 patients across five cancer types — found that proton therapy delivers equivalent cure rates to traditional X-ray radiation with significantly fewer serious side effects. That included fewer hospitalizations and emergency room visits. Siteman opened the world’s first single-room compact proton system in 2013 and added a second pencil-beam unit in 2020.
IMRT — NOW THE NATIONAL STANDARD OF CARE
WashU Medicine radiation oncologists at Siteman were among the first in the United States to deliver intensity-modulated radiation therapy (IMRT) — a technique that shapes beams to the exact 3D contour of a tumor, delivering higher doses to cancer while protecting adjacent organs. IMRT is now the national standard of care for prostate cancer and many other cancer types. Siteman was the first center in St. Louis and the Midwest to offer IMRT and 3D treatment planning.
SBRT DELIVERING SURGERY-LEVEL OUTCOMES FOR LUNG CANCER
WashU Medicine physician Clifford Robinson. MD leads one of the largest SBRT lung cancer programs in the country. He led a Phase III clinical trial directly comparing SBRT to surgery for early-stage non-small cell lung cancer, advancing care for patients who cannot tolerate an operation. SBRT, which delivers precisely targeted radiation in five or fewer sessions, is now the standard of care for medically inoperable early-stage lung cancer. Learn about SBRT at Siteman.
With more than 600 active clinical trials, Siteman offers access to investigational therapies not broadly available elsewhere — including cutting-edge EBRT studies.
Specialized care for children
Treating cancer in a child requires a fundamentally different approach. Growing bodies are more sensitive to radiation, and your child’s developing organs, brain function, and long-term health are part of every decision the Siteman Kids team makes.
Siteman Kids at St. Louis Children’s Hospital has a dedicated pediatric radiation oncology program led by Stephanie Perkins MD, a nationally recognized leader in pediatric proton therapy. Proton therapy is especially protective for children: it deposits radiation directly into the tumor and stops, reducing dose to surrounding healthy tissue in a way that conventional radiation can’t.
Perkins and her colleagues published the first ever peer-reviewed study on clinical outcomes for children treated with proton therapy in Cancer (2023). Their documentation showcased the protective benefits their approach to proton therapy had for children with brain tumors and other pediatric cancers. They continue that same excellence today.
Your Second Opinion at Siteman
Siteman wants to be your first choice for cancer care, but that might not always be possible. If you have received a cancer diagnosis, started care somewhere else, or are a physician seeking specialized care for your patient, ask us about a second opinion. You can start the process. To make it easy, our care coordinators guide scheduling for yourself or your patient.
Many patients come to Siteman after being treated — or diagnosed — elsewhere. Our team welcomes second opinion consultations. In many cases, patients discover additional options they were not previously offered. You deserve to know every path available to you.
Frequently Asked Questions About External Beam Radiation Therapy
Your Siteman care team, including radiation oncologists, medical oncologists, and other specialists, will review your case together at a weekly multidisciplinary tumor board before making any treatment recommendations. That means multiple experts weigh in on your specific situation, not just one physician. You will not be asked to decide anything until you fully understand your options. You do not have to navigate this alone.
Siteman offers the widest range of radiation options in the Midwest — including proton therapy, MRI-guided radiation (MRIdian), intensity-modulated radiation therapy (IMRT), stereotactic body radiation therapy (SBRT), and 3D conformal radiation therapy. Your team will recommend the approach best suited to your cancer type, location, stage, and overall health. In some cases, a combination of approaches is used.
Radiation itself is painless during delivery. Most patients describe lying still on a table while the machine moves around them — the session typically lasts 15 to 30 minutes. Many people continue working and carrying on daily activities throughout treatment, though fatigue is common and worth planning for. Your care team will walk you through exactly what to expect before your first appointment and will check in with you regularly throughout. You will have support and resources for any side effect you might have.
Side effects vary depending on the cancer type, the treatment area, and the approach used. Common experiences include fatigue and localized skin sensitivity at the treatment site. With newer approaches like proton therapy and MRI-guided radiation, damage to surrounding healthy tissue is significantly reduced compared to older techniques — and that matters for your recovery and long-term quality of life. Your physician will discuss the specific risks relevant to your plan before treatment begins.
It depends on your cancer and the approach your team recommends. Some patients complete treatment in as few as five sessions with SBRT. Others receive daily sessions over several weeks. Your care team will give you a clear picture of what a typical schedule looks like for your before you begin. That way you can plan ahead with confidence.
Pediatric patients receive care from a dedicated team at Siteman Kids at St. Louis Children’s Hospital. Children receive smaller, more precisely targeted doses than adults — and whenever possible, proton therapy is used because it protects developing organs and tissue from unnecessary radiation exposure. Parents are included at every step of the process, and the pediatric and adult radiation oncology teams collaborate closely.
Most insured patients, including those with Medicare or Medicaid, have coverage for external beam radiation therapy. Cost should not be a barrier to getting the care you need. Siteman’s financial wellness team can help you understand your benefits, identify assistance programs, and navigate out-of-pocket costs. Reach out to our team to review all of your coverage options before treatment begins.
Yes. Siteman maintains more than 600 active therapeutic clinical trials each year. That includes studies on SBRT, MRI-guided radiation, proton therapy combinations, and more. These trials provide access to emerging therapies not broadly available elsewhere. Your care team will evaluate your diagnosis against every applicable trial and walk you through your options.
