What is IORT? IORRT is radiation therapy used in breast cancer surgery.

IORT (Intraoperative Radiation Therapy) is a treatment that directs radiation to the site of a cancerous tumor during surgery, completed in a single session, instead of repeated external radiation treatments that require weeks of hospital visits. At Namarak Hospital, we use the Intrabeam 600 machine to deliver low-energy radiation directly to the scar cavity immediately after tumor removal. This treatment is suitable for appropriately selected patients with early-stage breast cancer, as determined by our medical team.

IORT is not an option for all patients. The decision of whether it is appropriate or not depends on an individual assessment by a team of specialist physicians.

What is IORT?

IORT stands for Intraoperative Radiation Therapy. It's a localized radiation therapy technique (Partial Breast Irradiation) that delivers a high dose of radiation in a single dose directly to the tissue surrounding the surgical site where the tumor was recently removed. This is done while the patient is still in the operating room and under anesthesia.

The concept behind IORT is that locally recurrent breast cancer often occurs closest to the original tumor site. Direct radiation therapy in the operating room helps reduce the chance of recurrence in the most vulnerable area, while also minimizing radiation exposure to normal tissues and surrounding organs such as the heart and lungs.

How does IORT differ from conventional light therapy?

Standard post-breast-conserving radiotherapy involves whole-breast external beam radiotherapy (EBRT), requiring patients to visit the hospital almost every weekday for 3 to 6 weeks. In contrast, IORT is a single-dose treatment administered in the operating room. A comparison of the two methods is as follows:

IORT (In-Surgical Radiation Therapy): A single treatment performed during surgery, eliminating the need for additional travel. Radiation is directed only around the surgical site, minimizing radiation exposure to surrounding organs. Suitable for selected, early-stage patients.

EBRT (Traditional External Radiation Therapy): A series of treatments over 3 to 6 weeks requires hospital visits almost every weekday. The entire breast is exposed, and surrounding organs receive higher radiation levels. Suitable for a wide range of patients.

However, the two methods are not always interchangeable. In some cases, a doctor may recommend IORT in combination with EBRT if postoperative pathology reveals higher-than-expected risk factors, a process known as a risk-adapted approach.

How does IORT work? What are the steps involved?

In breast-conserving surgery, the surgeon removes the cancerous tumor along with the surrounding normal tissue. After the tumor is removed, a scar remains in the breast tissue. Then...

• The radiologist inserts a spherical applicator that is sized to fit the wound cavity, with sizes ranging from approximately 1.5 to 5 centimeters.

• The Intrabeam machine emits low-energy X-rays, approximately 50 kilovolts, from the tip of the probe to the surrounding tissue.

• The radiation is concentrated at the surface of the wound cavity and decreases rapidly with distance, thus limiting its effect on deeper or more distant tissues.

• The treatment takes approximately 20 to 50 minutes, depending on the size of the projector head. The surgeon then closes the incision as usual.

The entire procedure requires coordination between the breast surgeon and the radiologist who are present in the operating room.

Advantages of IORT

For suitable patients, IORT offers several advantages.

• Reduce the number of treatment sessions and duration from weeks of radiation therapy to a single session during surgery.

• Shine directly onto the most vulnerable point, reducing the chance of missing the mark because the beam is projected while the wound is exposed, revealing the actual location.

• It reduces radiation damage to surrounding organs, especially the heart and lungs, because low-energy radiation decreases rapidly over time.

• Convenient and reduces the burden of travel, ideal for patients who live far away or have difficulty traveling.

• The aesthetic results are good; research reports satisfaction with breast appearance is rated as good to very good.

Who is suitable for IORT and who is not?

Patient selection is the most important factor in the success of IORT treatment. Based on the criteria used in the TARGIT-A research, groups considered for IORT typically have the following characteristics:

• Ages 45 and above.

• This is an invasive ductal carcinoma type of breast cancer that is suitable for breast-conserving surgery.

• Small nodules, generally no larger than about 3.5 centimeters, and usually solitary (unifocal).

• There was no extensive lymph node spread.

IORT alone may not be suitable for patients with large, multifocal tumors, significant lymph node invasion, or high pathological risk factors. These patients may require standard whole-breast radiation therapy or a combination of IORT and EBRT. Final evaluation must be performed by a specialist team based on each individual patient's information.

medical evidence

There are two large randomized trials studying IORT in breast cancer.

The TARGIT-A trial compared IORT (Intrabeam Radiation Therapy) with risk-modified low-energy X-rays (intrabeam) with standard whole-breast radiotherapy in 2,298 patients. Long-term follow-up (median 8-9 years) showed that the IORT group provided comparable cancer control to standard radiotherapy in terms of local recurrence, survival, and breast cancer mortality. The 5-year local recurrence rate was approximately 2.1%, compared to 0.95%, which is considered non-inferior. Furthermore, mortality from non-breast cancer causes was lower in the IORT group compared to the standard radiotherapy group.

The ELIOT trial, which studied IORT with electron beams, found that less rigorous patient selection resulted in a higher relapse rate compared to standard radiation therapy. However, in low-risk groups selected according to appropriate criteria, the relapse rate was very low, reinforcing the importance of appropriate patient selection.

In summary, evidence supports IORT as an effective option for appropriately selected patients with early-stage breast cancer, but it is not for everyone, and there is still detailed debate within the medical community, which is why decisions should be made in consultation with a specialist.

IORT at Numarak Hospital.

Numarak Hospital provides IORT treatment using the Intrabeam 600 machine, an intraoperative radiation therapy technology used in leading cancer centers worldwide. The strength of Numarak's treatment lies not only in the equipment but also in the collaborative planning of a multidisciplinary team comprising breast surgeons, radiation oncologists, and medical oncologists. This team assesses each patient's suitability for IORT, under the "High Tech High Touch" concept.

If you are planning breast cancer surgery and want to know if IORT is the right option for you, you can consult with our medical team for more information. Read more about breast cancer surgery at Namarak Hospital and our services on the Services page.

Risks and limitations

Although IORT has many advantages, it also has limitations that should be understood.

• The pathology results were not yet complete at the time of radiation therapy because it was administered during surgery. Therefore, the final pathology results are not yet known. If high-risk factors are later identified, additional radiation therapy may be necessary.

• It's not suitable for everyone, depending on the size of the tumor, its location, and how it has spread.

• Local side effects such as swollen wounds, fluid accumulation, or minor skin changes are generally manageable.

Having a detailed discussion with your doctor about the advantages, limitations, and alternatives is an important step before making a decision.

In 2025, the American Society for Radiation Oncology (ASTRO) issued a statement clarifying information about IORT, emphasizing that long-term follow-up data for some IORT techniques remain limited and that the technique has not been incorporated as a primary recommendation in standard clinical practice guidelines. This position aligns with the principle Namarak Hospital follows: IORT should be offered only to carefully selected patients, with both its benefits and limitations clearly explained so that patients can make an informed decision together with their medical team. It is not appropriate for every patient.

Frequently Asked Questions (FAQ)

What is IORT? How does it differ from regular radiation therapy?

IORT is a method of direct radiation therapy that targets the cancerous tumor during surgery in an operating room, completing the procedure in a single session. In contrast, traditional EBRT (External Breast Radiation Therapy) irradiates the entire breast externally, requiring multiple hospital visits over several weeks. IORT helps reduce the time and number of sessions for a suitable patient.

Is IORT suitable for all patients?

Non-IORT is suitable for selected patients with early-stage breast cancer who meet certain criteria, such as being 45 years of age or older, having a small, solitary tumor, and not having extensive lymph node invasion. Patient selection is the most important factor and must be evaluated individually by a team of specialist physicians.

Is there any evidence that IORT is actually effective?

A large, randomized, long-term trial, TARGIT-A, found that in eligible patients, IORT provided cancer control comparable to standard radiation therapy. However, no treatment is 100% effective, and outcomes depend on the selection of suitable patients.

Is IORT painful? How long does it take?

The patient feels no pain during the treatment because it is performed in the operating room while under anesthesia. The treatment takes approximately 20 to 50 minutes, depending on the size of the projector head. The wound is then sutured closed as usual.

If I've already received IORT treatment, do I need additional radiation therapy?

In most cases, this is not necessary. However, if post-operative pathology reveals higher-than-expected risk factors, your doctor may recommend additional whole-breast radiation therapy. This is a risk-adapted approach to ensure maximum safety.

Does IORT use radiation that is dangerous to people around it?

IORT (Intermittent Radiation Therapy) uses low-energy X-rays that decrease rapidly over time and is performed in an operating room with standard radiation protection measures. After treatment, there is no residual radiation that harms those around the patient.

About Numarak Hospital

Numarak Hospital is a comprehensive breast and breast cancer specialist hospital in Bangkok, offering services ranging from screening and diagnosis to surgery and treatment using state-of-the-art technology, including IORT, by a team of specialist physicians. For consultations or further advice on breast cancer treatment options, please contact the hospital.

Related: Breast-Conserving Therapy (BCT)