Intraoperative Radiation Therapy (IORT)

Introduction

If your cancer team has mentioned intraoperative radiation therapy — usually shortened to IORT — you are probably trying to understand what it means for your surgery and your overall treatment plan. IORT is a way of giving radiation during the operation itself, in a single concentrated dose, directly to the area where the tumour was. It is not a separate set of hospital visits stretched over weeks; it happens once, in the operating room, while you are still under anaesthesia.

IORT is not used for every cancer or every patient. It is a specialised technique offered in carefully selected situations, usually as part of a wider plan that may include surgery, other forms of radiation, chemotherapy or targeted therapy. The decision to use it is made by a multidisciplinary team — typically a surgical oncologist, a radiation oncologist and a medical physicist — based on the type of cancer, its location, the risk of local recurrence and how the surgery is being planned.

This article explains what IORT is, how it differs from other forms of radiation, which cancers it is used for, what happens on the day of surgery, what side effects to expect, and how recovery and follow-up unfold. The aim is to give you a clear picture of the technique so that the conversation with your own treating team is easier to follow.

What Is Intraoperative Radiation Therapy?

Intraoperative radiation therapy (IORT) is a technique in which a single, high dose of radiation is delivered directly to the tumour bed — the area where a tumour was just removed, or in some cases the tumour itself if it cannot be fully removed — during the same operation. The radiation is applied through a special applicator or device that is placed inside the surgical opening. Healthy organs nearby can be physically moved out of the way or shielded with protective material before the radiation is delivered.

Radiation dose is measured in units called Gray (Gy). With external radiation, the total dose is usually divided into many small daily fractions over several weeks. With IORT, a much larger dose is given in one go, but only to a very small, well-defined area. This is possible because the radiation does not have to pass through skin, fat and muscle to reach the target. It is delivered directly to the tissue at risk, so a high biological effect can be achieved while sparing surrounding structures.

The technique has been used in clinical practice for several decades and is described in guidance from major radiation oncology societies, including the American Society for Radiation Oncology (ASTRO) and the European Society for Radiotherapy and Oncology (ESTRO). It is considered an established option in selected indications, although it remains a specialised service offered by centres with the required equipment and trained teams.

How IORT Differs from Other Forms of Radiation

To understand IORT, it helps to see how it sits alongside the other radiation techniques you may have heard about:

• External beam radiation therapy (EBRT) — radiation is delivered from a machine outside the body, usually in many daily sessions over three to six weeks.
• Intensity-modulated radiation therapy (IMRT) — a refined form of EBRT in which the beams are shaped and varied in intensity to match the tumour, sparing nearby organs.
• Stereotactic body radiation therapy (SBRT) — very high-dose, very precise external radiation given in a small number of sessions, used for small, well-defined targets.
• Brachytherapy — radioactive sources placed temporarily or permanently inside or next to the tumour through catheters or applicators, often as an outpatient procedure.
• IORT — a single dose delivered through an applicator placed directly in the surgical wound, while the patient is in the operating room.

IORT is not a replacement for these other techniques in most situations. It is one tool among several, and is often combined with external radiation or systemic treatment.

Why Is IORT Performed?

The main reason IORT is offered is to reduce the chance that cancer comes back in the area where it started — called local recurrence. After surgery, microscopic cancer cells can sometimes remain in the tissue around the removed tumour. Radiation is one of the standard ways to reduce this risk. With IORT, radiation can be aimed at the highest-risk area at the precise moment when that area is exposed and visible to the surgical team.

Doctors may consider IORT when one or more of the following apply:

• The tumour is in a location where surgical margins (the rim of healthy tissue around the removed tumour) are likely to be narrow or close to important structures.
• The cancer has a known higher risk of coming back locally if treated with surgery alone.
• The patient has already received radiation to the same area in the past, and additional external radiation would be difficult or unsafe.
• Shortening the overall treatment course is clinically reasonable — for example, in selected early breast cancers, IORT may replace some or all of the post-operative external radiation course.
• The surgical team can fully expose the tumour bed and shield nearby healthy organs.

IORT is most often used as a “boost” — an extra dose to the highest-risk area — in combination with external radiation given over the following weeks. In some specific situations, particularly selected early-stage breast cancers, it may be used as the sole radiation treatment. This choice depends on tumour biology, margins and the patient’s overall risk profile, and is made by the treating team according to current guidelines.

Which Cancers Are Treated with IORT?

Breast Cancer

In early-stage breast cancer treated with breast-conserving surgery (lumpectomy), IORT can be used either as a single-dose treatment to the tumour bed or as a boost combined with later external radiation. Two well-known clinical trials — TARGIT-A (using low-energy X-rays) and ELIOT (using electrons) — helped define the patient groups in whom this approach has been studied. National Comprehensive Cancer Network (NCCN) and ASTRO guidance describe IORT as one of the partial breast irradiation options, with patient selection criteria related to age, tumour size, hormone receptor status and margins.

Colorectal Cancer

For locally advanced rectal or colon cancers, and especially for cancers that have come back in the pelvis after earlier treatment, IORT may be considered when the surgical margins are at risk of being positive or very close. In these situations, the radiation dose is delivered directly to the area at highest risk while the bowel and other pelvic organs are moved aside.

Pancreatic Cancer

Pancreatic tumours often sit very close to major blood vessels, which makes wide surgical margins difficult to achieve. IORT may be used in carefully selected pancreatic cancer operations to deliver additional radiation to the area near these vessels, as part of a combined treatment plan that usually also includes chemotherapy and sometimes external radiation.

Soft Tissue Sarcomas

Sarcomas in the abdomen, pelvis or limbs — particularly retroperitoneal sarcomas, which lie behind the abdominal organs — can be challenging to remove with wide margins because of nearby kidneys, bowel and major vessels. IORT is sometimes used to add a focused dose to the area at highest risk of recurrence.

Gynaecologic Cancers

In selected recurrent gynaecologic cancers, such as recurrent cervical or endometrial cancers in the pelvic sidewall, IORT may be considered when surgery is being attempted and the margins are likely to be narrow.

Other Selected Tumours

IORT has also been used in head and neck cancers, certain paediatric tumours and selected recurrent cancers in areas previously treated with external radiation. These are specialised situations decided case by case in a tumour board.

Who Is a Candidate?

Whether IORT is appropriate is a clinical decision that depends on several factors. The treating team will usually consider:

• Tumour type and stage — IORT is supported by stronger evidence in some cancers (such as early breast cancer and locally advanced or recurrent rectal cancer) than others.
• Location — the tumour bed must be reachable with the applicator, and healthy organs must be able to be shielded or moved.
• Margins and risk of recurrence — IORT is most useful where the risk of microscopic disease left behind is meaningful.
• Prior radiation — in patients who have already had radiation to the same area, IORT can sometimes deliver an extra dose more safely than repeating external radiation.
• Overall fitness for surgery — IORT extends the operating time by some minutes to half an hour or so, so the patient must be fit enough for the combined procedure.
• Patient preference and goals — shorter overall treatment, fewer hospital visits and the trade-offs of different radiation approaches are part of the conversation.

Not every hospital offers IORT. The equipment is specialised and requires a coordinated team. Patients are usually referred to a centre with experience in the technique once the multidisciplinary team has agreed it may be appropriate.

Alternatives to IORT

Because IORT is one of several ways to deliver radiation to a cancer site, it is helpful to understand the alternatives the team may discuss.

Standard External Beam Radiation Therapy

Conventional EBRT, including IMRT and image-guided variants, is the most widely used form of post-operative radiation in most cancers. It is delivered in many short daily sessions over several weeks. It is well established, available in most cancer centres, and supported by decades of evidence across virtually every solid tumour.

Hypofractionated and Stereotactic Radiation

In some cancers, particularly early breast cancer and certain lung, liver and prostate cancers, shorter courses of external radiation using larger daily doses (hypofractionation) or very focused stereotactic techniques have become standard or accepted options. These can also shorten the overall treatment time without the need for an intraoperative procedure.

Brachytherapy

Brachytherapy places radioactive sources inside or next to the tumour through catheters. It can be given as a separate procedure, sometimes over a few sessions, and is used in cancers such as cervical, prostate, skin and selected breast cancers. In some breast cancer protocols, multi-catheter or balloon-based brachytherapy serves a similar purpose to IORT.

Surgery Alone

In some early or favourable cancers, surgery without any radiation may be appropriate. The decision rests on tumour biology, margins and the estimated risk of recurrence.

Systemic Therapy

Chemotherapy, hormonal therapy, targeted therapy and immunotherapy address cancer cells throughout the body. These are not alternatives to local radiation in the strict sense, but the overall treatment plan balances local control (surgery and radiation) and systemic control (drug therapies).

The right combination depends on the cancer type, stage and individual circumstances. Major societies recommend that radiation options — including IORT where relevant — be discussed in a multidisciplinary tumour board so that the patient receives a coordinated recommendation.

Approaches: Types of IORT Technology

Electron-Beam IORT (IOERT)

Electron-beam IORT uses a linear accelerator — either a dedicated mobile unit brought into the operating room or a shielded operating theatre next to a standard radiation bunker — to deliver high-energy electrons. Electrons penetrate to a controlled depth and then stop, which makes them useful for treating a layer of tissue at the tumour bed without affecting structures further below. This technique has the longest track record and was used in the ELIOT breast cancer trial and many sarcoma and gastrointestinal studies.

Low-Energy X-ray IORT

Low-energy (kilovoltage) X-ray IORT uses a small, portable device that produces low-energy X-rays at the tip of an applicator placed in the surgical cavity. The radiation falls off very steeply with distance, so tissues a few centimetres away receive a much lower dose. This system was used in the TARGIT-A breast cancer trial. Because the device is compact and shielding requirements are modest, it can be used in standard operating theatres.

High-Dose-Rate Intraoperative Brachytherapy (HDR-IORT)

HDR-IORT uses a high-dose-rate brachytherapy source delivered through flexible catheters arranged over the tumour bed in a custom applicator. It is often used in complex pelvic, abdominal or recurrent cancers where the surface to be treated is irregular. The applicator conforms to the shape of the cavity, and the source moves through the catheters to deliver the planned dose.

Each technology has practical strengths and limits. The radiation oncologist and physicist plan the dose and applicator based on the size and shape of the target area, the surrounding organs, and what the surgical exposure allows.

Preparing for Surgery with IORT

Preparing for an operation that includes IORT is similar to preparing for the surgery itself, with some additional planning steps led by the radiation oncology team.

Pre-Surgical Evaluation

Imaging such as CT or MRI is reviewed to map the tumour, plan the surgical approach and estimate the size of the area that will need radiation. Pathology from any prior biopsy is reviewed. Blood tests, heart and lung assessments and other pre-anaesthesia checks are done as usual.

Multidisciplinary Planning

Before the operation, the surgeon, radiation oncologist and medical physicist meet to agree:

• The likely target area for IORT
• The radiation dose in Gray
• The applicator size and type
• How nearby organs will be moved or shielded
• Whether additional external radiation will be planned afterwards depending on final pathology

Consent and Information

You will be given specific information about IORT in addition to the usual surgical consent. The consent conversation usually covers what IORT adds to the operation, the radiation-specific risks, and the chance that, based on what is found during surgery, IORT may not actually be delivered (for example, if the tumour cannot be reached safely or if the margins look unexpectedly wide and the radiation is not needed).

Day Before and Day of Surgery

Standard instructions apply: fasting from a set time before surgery, stopping certain medicines if your team has asked, and arranging support at home for the recovery period. The hospital will tell you when to arrive and what to bring. The IORT step is built into the operating room schedule, so the procedure may take somewhat longer than a non-IORT version of the same surgery.

What Happens During Surgery

1. Anaesthesia and surgical access. You are anaesthetised and the surgical team opens the operating field as planned.
2. Tumour removal or exposure. The surgeon removes the visible tumour. In some cases, frozen-section pathology is performed during surgery to check the edges.
3. Decision to proceed with IORT. Based on what is seen, the team confirms that IORT is still appropriate. If not, the operation continues without it.
4. Positioning of the applicator. The chosen applicator is placed against the tumour bed. For breast IORT, this is often a spherical applicator that fits inside the lumpectomy cavity. For pelvic or abdominal cases, a flat or shaped applicator may be used.
5. Protection of nearby tissues. Healthy organs near the radiation area are moved aside with retractors or covered with shielding material. The operating room team steps out or behind shielding during the radiation itself, depending on the technology.
6. Radiation delivery. The pre-planned dose is delivered. The active radiation portion usually takes around ten to thirty minutes, depending on the device and the dose.
7. Completion of surgery. The applicator is removed, the team returns to the surgical field, and the operation is closed in the standard way. Drains may be placed if needed.

The whole operation, including IORT, may take an additional thirty minutes to about an hour compared with the same surgery without IORT, although this varies by case.

Recovery and Healing

Hospital Stay

The length of the hospital stay depends on the type of surgery. A breast lumpectomy with IORT may be a same-day or overnight stay. Major abdominal or pelvic operations may need several days in hospital, the same as they would without IORT. Pain control, early mobilisation, breathing exercises and bowel function are managed as usual.

First Few Weeks

During the first weeks at home, the priorities are wound healing, gradual return to activity and managing tiredness. The treated area may feel firm, tender or slightly swollen for some time. Mild fatigue is common after any cancer surgery and is not specific to IORT. Your team will advise on:

• Wound and dressing care
• Pain medicines and how to step them down
• When to shower or bathe
• How much to walk and when to start gentle activity
• When to drive
• When to return to work
• Signs that should prompt urgent review (fever, increasing pain or redness, wound discharge, bleeding)

Follow-up Appointments

You will have surgical follow-up to check the wound and review the final pathology report. The pathology may confirm clean margins, in which case the planned treatment continues; or it may show features that lead the team to recommend additional treatment, such as further external radiation, chemotherapy or hormonal therapy. The IORT step does not replace this assessment — it is part of an overall plan that is finalised once all the pathology is available.

Long-Term Follow-up

Long-term follow-up is the same as for the underlying cancer. This typically includes physical examinations, imaging (such as mammograms, CT or MRI depending on the cancer), and sometimes blood tests, at intervals defined by the cancer type and stage.

Side Effects, Risks and Complications

IORT is generally well tolerated when performed by experienced multidisciplinary teams in appropriately selected patients. Most side effects are related to the surgery itself, with the addition of effects from the radiation dose delivered to the tumour bed.

Common Side Effects

• Local swelling and tenderness at the treated area
• Firmness or hardening of tissue (fibrosis) developing over months
• Mild delay in wound healing in some cases
• Fatigue after surgery, usually improving over several weeks
• Skin changes in the treated area, such as discoloration, in some patients

Site-Specific Effects

Breast IORT. Firmness in the lumpectomy area, a small fluid collection (seroma), localised tenderness, and sometimes changes in the shape or feel of the breast over time.

Abdominal and pelvic IORT. Changes in bowel or bladder function, nerve-related symptoms if a nerve was close to the treated area, and longer-term effects on tissues such as ureters or blood vessels in rare cases.

Rare Complications

• Wound infection or breakdown
• Tissue necrosis (areas of tissue damage) in or near the treated zone
• Fistulas or ulcers in the bowel or other hollow organs (rare, mainly in abdominal or pelvic cases)
• Nerve damage leading to pain or weakness, particularly in pelvic or limb sarcoma cases
• Damage to nearby blood vessels

Because IORT delivers a single high dose, the team plans carefully to keep the dose below the tolerance of nearby healthy tissues. Even so, the high single dose means that any late effects in the treated area can sometimes be harder to manage than after fractionated external radiation. This is one of the reasons IORT is reserved for selected cases.

Managing Side Effects

The care team will guide you through wound care, pain management, nutrition and gradual return to activity. Promptly reporting fever, new severe pain, increasing swelling, wound problems or unusual bowel or bladder symptoms allows early treatment if a complication develops.

Outcomes and What to Expect

Outcomes with IORT depend on the cancer type, its stage, the surgical margins, and what other treatments are part of the overall plan. Rather than thinking of IORT as a treatment with its own success rate, it is more accurate to think of it as one component of a combined approach whose overall success is judged by the cancer outcome.

In broad terms:

• In selected early-stage breast cancers, randomised trials have studied IORT as partial breast irradiation, with results that informed current guidelines on patient selection. Local control depends on tumour biology and margin status. Doctors usually discuss the trade-off between a single intraoperative dose and a full external radiation course.
• In locally advanced or recurrent rectal cancer, IORT is used to reduce local recurrence risk when margins are at risk; it is part of a strategy that usually also includes preoperative chemotherapy and external radiation.
• In pancreatic cancer, IORT is studied as part of multimodality treatment; outcomes depend heavily on whether the cancer can be completely removed and on the response to chemotherapy.
• In retroperitoneal and other sarcomas, IORT may be used to add a focused dose where wide surgical margins are not feasible.

Specific numerical estimates for your situation should come from your treating team, who can take into account the details of your tumour, imaging and pathology. Major societies recommend that these conversations include the realistic benefits, the alternatives and the possible side effects, so that the choice fits both the medicine and your priorities.

Life After IORT

For most patients, life after IORT is shaped by life after the underlying cancer treatment rather than by the IORT step itself. The treated area may feel different over time. Some long-term changes — such as firmness, mild skin or tissue changes, or subtle differences in shape — are common in the area that received radiation.

Surveillance for Recurrence

Cancer follow-up usually continues for several years and may include clinical examination, imaging and blood tests according to the cancer type. Even when IORT has been used, the same surveillance schedule applies as for the cancer itself.

Healthy Habits

General recommendations to support recovery and reduce future cancer risk — not smoking, limiting alcohol, staying physically active, eating a balanced diet and keeping a healthy weight — apply equally to patients who have received IORT.

Emotional Recovery

Going through cancer surgery, with or without IORT, is demanding. It is normal to feel tired, anxious or low for a period afterwards. Talking to your team, family or a counsellor, and connecting with others who have had similar treatment, can help. Mention any persistent low mood or anxiety to your doctor, as support is available.

IORT and Re-Irradiation

One situation where IORT plays a particular role is in cancers that come back in an area that has already received radiation. In these cases, repeating a full course of external radiation may not be safe because nearby tissues have already received close to their tolerance dose. IORT can sometimes deliver an additional, focused dose at the time of further surgery, with the help of physical shielding and careful planning, when external re-irradiation would be too risky. Whether this is feasible depends on the prior dose, the time since previous radiation, the location of the recurrence and the surgical access.

IORT in Children

IORT is used only rarely in children, in highly specialised paediatric oncology centres, for selected tumours where the technique may help reduce damage to growing tissues by avoiding a full course of external radiation. Decisions are made by paediatric oncology multidisciplinary teams with specific experience in this setting. The general principles — targeting the area at risk, shielding healthy tissues, and integrating IORT with other treatments — are the same as in adults.

Frequently Asked Questions

Is IORT painful?

No. IORT is delivered while you are under general anaesthesia for the surgery. You do not feel the radiation. Any discomfort afterwards comes from the surgical incision and healing, managed with standard post-operative pain control.

Will I still need external radiation after IORT?

It depends on the cancer, the tumour size, the margins and the final pathology. In some patients, particularly in selected early-stage breast cancers, IORT may be the only radiation given. In others, IORT is used as a boost and external radiation follows over several weeks. Your team will confirm the plan once pathology results are back.

How long does the radiation portion of the operation take?

The active radiation delivery usually takes around ten to thirty minutes, depending on the device, the dose and the size of the area. The total operating time is longer because positioning the applicator and shielding take additional minutes.

Is IORT considered safe?

IORT has been used for decades and is described in guidelines from major radiation oncology societies. In carefully selected patients, performed by experienced multidisciplinary teams in centres with the right equipment, it is considered an established option. Like any radiation treatment, it carries risks, which the team discusses as part of consent.

Am I radioactive after IORT?

No. IORT uses external radiation sources (electrons or X-rays) that do not make your body radioactive. Once the radiation has been delivered and the applicator removed, no radiation remains. It is safe to be around family members, including children and pregnant women, after the surgery.

Why is IORT not available everywhere?

IORT requires specialised equipment, shielding (depending on the technology), and a trained team of surgeons, radiation oncologists, medical physicists and nurses who can coordinate the procedure in the operating room. Only centres that have made this investment offer it. Patients are often referred to such centres when their case is felt to be suitable.

What if my surgeon and radiation oncologist disagree about whether IORT is right for me?

Decisions about IORT are usually made in a multidisciplinary tumour board where surgeons, radiation oncologists, medical oncologists, radiologists and pathologists discuss the case together. If you would like more clarity, you can ask for the reasoning behind the recommendation, what alternatives were considered, and what the expected benefits and risks are for your specific situation.

Can IORT be repeated if cancer comes back?

Repeating IORT at the same site is not usually possible because of the dose already delivered to the surrounding tissues. However, in some patients with a recurrence, IORT may be considered during a new operation if other forms of radiation are no longer feasible. This is decided case by case.

Conclusion

Intraoperative radiation therapy is a way of giving a single, focused dose of radiation directly to the tumour bed during cancer surgery. It is used in selected cancers — including some breast, colorectal, pancreatic, sarcoma and gynaecologic cancers — usually as part of a wider treatment plan that may also include external radiation and systemic therapy. Its value lies in delivering radiation at the moment the target tissue is exposed and visible, with healthy organs shielded or moved aside.

IORT is not the right choice for every cancer or every patient. The decision involves the type and stage of cancer, the surgical approach, the risk of local recurrence, the availability of equipment and the patient’s overall situation. Major societies recommend that these decisions be made by a multidisciplinary team, with a clear conversation about the benefits, the alternatives such as external radiation or brachytherapy, and the possible side effects.

If IORT has been raised as part of your treatment plan, the most useful next step is a detailed discussion with the surgical and radiation oncology teams who will look after you. Understanding how IORT fits into the overall plan — what it adds, what still needs to follow, and what to expect during recovery — can make a complex treatment journey clearer and easier to navigate.