Intraoperative Radiation Therapy (IORT) delivers radiation directly to the area where a breast tumor has been removed while the patient is still in the operating room. For selected patients with early-stage breast cancer, IORT may be considered as part of a breast-conserving treatment plan after careful review by the breast surgeon and radiation oncologist.
At the Margie Petersen Breast Center, surgical and radiation oncology teams work together to determine whether IORT or another form of partial- or whole-breast radiation is most appropriate based on the cancer, pathology findings and current treatment guidelines.
What Is Intraoperative Radiation Therapy (IORT)?
IORT is a form of radiation therapy delivered during breast-conserving surgery. After the tumor is removed, radiation is directed to the surgical cavity where microscopic cancer cells are most likely to remain. Treatment is completed before the incision is closed.
Because the radiation is focused directly on the tumor bed, IORT limits exposure to much of the surrounding breast and can reduce radiation exposure to nearby organs such as the heart and lungs. In some treatment plans, it may also reduce the number of radiation treatments needed after surgery.
How IORT Is Delivered
After a lumpectomy removes the breast tumor and surrounding tissue, the radiation oncologist delivers a prescribed dose of radiation directly to the surgical cavity. Different IORT systems may use low-energy x-rays, electrons or other specialized radiation techniques.
Nearby tissues can be positioned or protected to limit unnecessary radiation exposure. Once the treatment is completed, the radiation equipment is removed and the surgeon completes the operation.
Why Some Patients Consider IORT
The main appeal of IORT is that radiation can be delivered at the same time as breast surgery. For some patients, this may reduce the number of separate radiation visits and concentrate treatment on the area of the breast at greatest risk for local recurrence.
IORT can also limit radiation exposure to healthy tissue outside the treatment area. However, convenience alone does not determine whether IORT is appropriate. The oncologic effectiveness of the treatment and the characteristics of the individual cancer remain the most important considerations.
Who May Be Considered for Breast IORT?
IORT is not appropriate for every patient with breast cancer. When it is considered, the strongest candidates generally have favorable features associated with early-stage breast cancer and are already being treated with breast-conserving surgery.
Factors that may influence whether partial-breast radiation is appropriate include tumor size, lymph node status, surgical margins, tumor grade, hormone receptor status, patient age, breast cancer subtype and inherited cancer risk.
Patient Selection Matters
Current partial-breast radiation guidelines favor patients with smaller, node-negative cancers and other lower-risk clinical and pathologic features. Patients with positive lymph nodes, positive surgical margins, certain inherited cancer mutations or other higher-risk findings generally require a different radiation approach.
Importantly, eligibility for partial-breast radiation does not automatically mean that IORT is the preferred technique. The radiation oncologist considers both the patient’s cancer characteristics and the evidence supporting the available radiation methods.
What Does the Evidence Show About IORT?
IORT has been studied as a way to deliver partial-breast radiation during surgery. Studies have shown that carefully selected patients can have excellent breast cancer survival outcomes, but some clinical trials have also reported higher rates of cancer returning in the treated breast compared with established external-beam partial-breast or whole-breast radiation techniques.
For this reason, current American Society for Radiation Oncology (ASTRO) guidance does not recommend electron or photon IORT as the sole form of partial-breast radiation outside a clinical trial or multi-institutional registry. Other partial-breast radiation techniques have stronger long-term evidence supporting their use as alternatives to whole-breast radiation.
Survival and Local Recurrence Are Different Measures
When evaluating IORT, it is important to distinguish overall survival from local breast cancer recurrence. Studies may show similar survival while still finding differences in how often cancer returns in the treated breast. Both outcomes are considered when physicians discuss radiation options with patients.
When Additional Radiation May Be Recommended
IORT is delivered before the final surgical pathology report is available. If the final pathology identifies higher-risk features that were not known at the time of surgery, additional external-beam radiation may be recommended.
Examples may include unexpected lymph node involvement, positive or close surgical margins, a larger or more extensive cancer than anticipated, or other pathologic findings that increase the risk of recurrence.
Potential Benefits and Limitations of IORT
Potential Benefits
- Radiation is delivered directly to the surgical site while the tumor bed is clearly visible.
- Much of the surrounding breast and nearby organs can receive less radiation exposure.
- Treatment occurs during the breast operation rather than requiring a separate visit that day.
- For selected treatment plans, IORT may reduce the number of radiation treatments needed after surgery.
Potential Limitations
- Final pathology results are not yet available when IORT is delivered.
- Some patients may still require additional external-beam radiation.
- Long-term evidence is stronger for other partial-breast radiation techniques.
- IORT can increase the length and complexity of the surgical procedure.
- Possible side effects include swelling, fluid collection, bruising, infection, wound-healing problems, fibrosis or other changes in the treated breast.
Multidisciplinary Treatment Planning for IORT
At the Margie Petersen Breast Center, decisions about breast radiation are coordinated with the surgical and medical treatment plan. Breast surgeons, radiation oncologists, medical oncologists, breast imaging specialists and pathologists review the clinical findings that may influence both the choice of radiation and the sequence of treatment. For example, breast-conserving surgery may still be technically possible for a patient with a smaller breast, but the amount of tissue removed and the volume available around the surgical cavity can introduce additional technical and cosmetic considerations when IORT is being planned. The surgeon and radiation oncologist therefore consider the relationship between tumor size, breast volume, surgical margins, radiation delivery and the expected breast contour rather than evaluating each part of treatment separately.
If IORT is being considered, the discussion should include its potential benefits, the available alternatives, the possibility that additional radiation may still be needed and how the treatment fits with endocrine therapy, chemotherapy or other therapies when appropriate.
The Pros and Cons of IORT Treatment
Drs. Janie Grumley and April Vassantachart discuss how surgical and radiation oncology teams work together when considering IORT for breast cancer.
Frequently Asked Questions About IORT for Breast Cancer
Is IORT as effective as traditional radiation therapy?
IORT can produce excellent outcomes in carefully selected patients, but effectiveness depends on which outcome is being measured. Some studies have reported similar overall survival compared with other radiation approaches, while also finding higher rates of cancer returning in the treated breast.
Because of these local recurrence concerns and the relative strength of evidence supporting other partial-breast techniques, current ASTRO guidance does not recommend electron or photon IORT as the sole form of partial-breast radiation outside a clinical trial or multi-institutional registry. Patients who are candidates for partial-breast radiation may have several other radiation options with stronger long-term evidence.
Will I still need radiation after IORT?
Possibly. IORT is delivered before the final surgical pathology report is available. If the final pathology shows higher-risk features such as positive or close margins, unexpected lymph node involvement, a larger or more extensive tumor than anticipated, or other concerning findings, additional external-beam radiation may be recommended.
This possibility should be discussed before surgery so patients understand that receiving IORT does not guarantee that no further radiation will be needed.
What are the possible side effects of IORT?
IORT is generally focused on a limited area of the breast, which can reduce radiation exposure to surrounding healthy tissue. However, it can still cause treatment-related effects. Possible side effects include swelling, bruising, fluid collection, infection, wound-healing problems, skin irritation, fibrosis or firmness in the treated breast and, less commonly, nerve injury.
Because IORT is performed during the breast operation, some side effects may overlap with those caused by surgery itself. Your surgical and radiation oncology teams will discuss the risks that are most relevant to the treatment technique being considered.
How do I know if I am a candidate for IORT?
IORT is generally considered only for selected patients with favorable early-stage breast cancer characteristics who are undergoing breast-conserving surgery. Factors may include tumor size, lymph node status, surgical margins, tumor grade, hormone receptor status, age, breast cancer subtype and inherited cancer risk.
Being eligible for partial-breast radiation does not necessarily mean that IORT is the preferred technique. The radiation oncologist will compare IORT with other partial-breast and whole-breast radiation options and explain which approach is best supported by the clinical findings and available evidence.
Can I receive chemotherapy, endocrine therapy or other treatments if I have IORT?
IORT is considered as one part of the overall breast cancer treatment plan. Patients may still receive endocrine therapy, chemotherapy, targeted therapy or other systemic treatments when those therapies are recommended based on the characteristics of the cancer.
The sequence of treatment depends on the diagnosis and whether medication is being given before or after surgery. For this reason, decisions about IORT are coordinated with the breast surgeon, medical oncologist and radiation oncologist rather than made independently of the rest of the treatment plan.
Is IORT covered by insurance?
Insurance coverage for IORT varies by health plan, indication and treatment setting. Patients considering IORT should confirm coverage and any authorization requirements with their insurance provider before treatment. The care team can help provide the clinical information needed for authorization when appropriate.
Understanding Your Radiation Treatment Options
IORT is one of several ways radiation may be considered after breast-conserving surgery. Other approaches include whole-breast radiation and established forms of partial-breast radiation delivered with external-beam techniques or brachytherapy. The most appropriate option depends on the cancer, the surgical findings and the evidence supporting each treatment technique.
At Providence Saint John’s Health Center, radiation treatment is provided through Vasek Polak Radiation Oncology. Radiation oncologists work with the breast care team to help patients understand the purpose of radiation, the available treatment options and how radiation fits with surgery and medical therapy.
Learn more about the Vasek Polak Radiation Oncology Department at Saint John’s Health Center.
Choosing Your Treatment Path
IORT may be appealing because radiation can be delivered during surgery, but convenience should be weighed together with cancer control, final pathology, the possibility of additional radiation and the strength of evidence supporting each available treatment approach.
At the Margie Petersen Breast Center, our medical oncologists work with the multidisciplinary breast team to review the clinical findings, explain the available treatment options and guide each patient through a treatment plan based on the characteristics of the cancer and the individual’s needs and priorities.
Talk With Our Breast Clinic Team
The Breast Health Clinic can be reached at (310) 582-7209. If you have questions about a new breast symptom, need an evaluation or would like help determining your next step, call and a member of our team can assist you.
