A client's neck and jaw being treated with a gentle manual technique, the therapist's hands near the collarbone

Lymphedema risk after regional node radiation

Q: Does radiation to the nodes raise my lymphedema risk even if I only had a sentinel node biopsy?

Yes, by roughly double in the best prospective data. In the McDuff cohort, sentinel biopsy with regional node radiation carried a five-year rate of 12.2% against 5.6% for sentinel biopsy alone in pooled studies, and the onset peak was the latest of any group, at 36 to 48 months. Keep an eye on the arm for years, not months.

Q: Is radiation to the armpit safer than a dissection for lymphedema?

In the AMAROS trial, yes. Women with a positive sentinel node were randomized to axillary dissection or axillary radiotherapy; at five years lymphedema was recorded in 24.5% after dissection and 11.9% after radiotherapy, with no difference in survival at ten years. Whether that choice applies to you is a question for your surgeon and radiation oncologist together.

Q: How long after regional node radiation can lymphedema still start?

Late onset, beyond twelve months, was specifically associated with regional node radiation in the McDuff cohort, with peaks at 18 to 24 months after dissection plus radiation and 36 to 48 months after sentinel biopsy plus radiation. The NLN recommends screening continue for at least five years. Lymphedema risk never fully closes, but those windows are where attention pays most.

Q: Can a lymphedema therapist tell me which nodes were in my field?

No, and you should not rely on us to. Fields, doses and whether the supraclavicular or internal mammary nodes were included are the radiation oncologist's to explain, and the figures on this page vary by field. Ask for a copy of your treatment summary and bring it to your first lymphedema assessment.

Regional node radiation is an independent lymphedema risk factor that stacks with dissection (31.2% at five years) and pushes onset later, to 18 to 48 months.

By The Renu lymphatic and massage team · 7 min read

Radiation to the armpit, collarbone or chest-wall lymph nodes is an independent risk factor for arm lymphedema, and its effect adds to that of surgery. In a prospective cohort of 2,171 women, the five-year lymphedema rate was 31.2% after axillary dissection plus regional node radiation, 24.6% after dissection alone and 12.2% after sentinel node biopsy plus regional radiation. Radiation also shifts the onset later: the peak was 18 to 24 months after dissection with radiation and 36 to 48 months after sentinel biopsy with radiation, which is why measurement should continue for years rather than months.

If regional node radiation is on your plan, or already behind you, the two questions are how much it adds and when. Both have answers from prospective data, and both are easier to live with once you know the shape of the risk rather than only its existence.

What “regional node radiation” covers

Radiation after breast surgery may be directed at the breast or chest wall alone, or extended to the regional lymph nodes: the axilla (armpit), the supraclavicular nodes above the collarbone, and sometimes the internal mammary nodes beside the breastbone. Which of these were in your field, at what dose, is in your radiation treatment summary, and the radiation oncologist is the person to interpret it. The figures below come from studies that grouped “regional lymph node radiation” together, with one that looked at the supraclavicular field on its own.

The figures, side by side

McDuff and colleagues followed 2,171 women (2,266 at-risk arms) treated for breast cancer between 2005 and 2017, measuring arm volume with a perometer before surgery and at follow-up, and defining lymphedema as a relative arm-volume increase of 10% or more arising more than three months after surgery. With a median follow-up of four years:

Treatment	Five-year lymphedema rate
All treatments combined	13.7%
Sentinel node biopsy with regional node radiation	12.2%
Axillary dissection without regional node radiation	24.6%
Axillary dissection with regional node radiation	31.2%

Regional node radiation was one of three factors significantly associated with lymphedema on multivariable analysis, alongside high preoperative body mass index and axillary dissection. The same screening program’s earlier paper, by Ferguson, found regional lymph node irradiation associated with arm volume increase at P = .0364 in a model where blood draws, injections and flights were not.

Two other figures give the range. The NCI’s PDQ summary cites a randomized intervention study in which, by limb volume measurement or physician diagnosis, 42% of women had lymphedema at 18 months after surgery; the cohort had axillary dissection and radiation. And Horisawa’s 2024 Japanese cohort of 214 women at least a year after axillary dissection, using a 2 cm circumference difference between arms as the definition, found objective lymphedema in 52 (24%), with supraclavicular field irradiation the only statistically significant risk factor on univariate and multivariate analysis. The National Lymphedema Network lists regional nodal irradiation among the established risk factors in both its 2025 diagnosis and 2026 risk-reduction statements, second only to axillary dissection.

The definitions differ (10% volume, 2 cm girth, physician diagnosis), which is one reason the numbers differ. What they share is the direction: radiation to the nodes raises the rate, and raises it most when added to a dissection. The dissection-alone picture is on lymphedema after an axillary lymph node dissection, and the sentinel-biopsy picture on lymphedema risk after a sentinel node biopsy.

Radiation moves the onset later

The McDuff study was designed to ask when the risk is highest, and its central finding is that the timing depends on treatment. Overall, risk peaked between 12 and 30 months after surgery. Early-onset lymphedema, within twelve months, was associated with axillary dissection (hazard ratio 4.75) but not with regional node radiation (hazard ratio 1.21, P = .55). Late-onset lymphedema, beyond twelve months, was associated with regional node radiation (hazard ratio 3.86, P = .0001) and, less strongly, with dissection (hazard ratio 1.86).

The peaks fell at different points:

Axillary dissection without radiation: 6 to 12 months.
Axillary dissection with regional node radiation: 18 to 24 months.
Sentinel node biopsy with regional node radiation: 36 to 48 months.

In plain terms, surgery tends to show its effect in the first year, and radiation in the second, third and fourth. The practical trap is that the third and fourth years are exactly when follow-up visits thin out and people stop thinking about the arm. How these windows compare across other cancers and treatments is on when does lymphedema start after cancer treatment.

Radiation instead of dissection: what AMAROS showed

Radiation is not only something added to surgery. In the EORTC AMAROS trial, 1,425 women with T1 or T2 breast cancer and a positive sentinel node were randomized to axillary lymph node dissection or axillary radiotherapy instead. The ten-year results, reported in 2023, found axillary recurrence of 0.93% after dissection and 1.82% after radiotherapy, with no difference in overall or disease-free survival. In the updated five-year morbidity analysis, lymphedema was recorded in 24.5% after dissection and 11.9% after radiotherapy (P < .001). The 2014 primary report had already noted lymphoedema significantly more often after dissection at one, three and five years, and the authors concluded that axillary radiotherapy results in significantly less morbidity. The ten-year paper states that, considering less arm morbidity, radiotherapy is preferred over dissection for this group.

So for someone with a positive sentinel node, axillary radiotherapy in place of a dissection carries roughly half the lymphedema rate at five years. For someone who has already had a dissection and then receives regional radiation, the two risks stack. The difference between those two scenarios is a matter for your surgeon and radiation oncologist, and it is worth asking which one you are in.

What this means for how long to keep measuring

The NLN’s 2026 statement asks that people at high risk be screened as often as every three months for the first two years after surgery, with continued but less frequent screening in years three to five, and its diagnosis statement says screening should continue for at least five years given the cumulative incidence over that period. For anyone whose nodes were irradiated, the McDuff peaks make the later years the ones not to skip. A measurement that is only taken when the arm already looks different has missed the point; the NLN wants objective measurements combined with symptom report and clinical examination, against a preoperative baseline wherever one exists.

The symptoms to report immediately are the same as for anyone at risk: heaviness, a perception that the arm is bigger, or a perception of swelling.

When to call your oncology team

Questions about which nodes were treated, at what dose, and what your own risk is: the radiation oncologist, with your treatment summary in hand.
Heaviness, tightness or a change in how a ring, watch or sleeve fits, at any point in the years after treatment, so the arm can be measured.
Redness, warmth, pain, swelling, fever or chills in the arm or chest on the treated side, the same day: the NLN treats a suspected infection in an at-risk limb as an urgent medical event.
Tightness or reduced range of motion in the shoulder or chest wall that is getting worse, which may be a late radiation effect needing a rehabilitation assessment.

Where Renu fits in

We do not interpret radiation fields or doses, and we will not guess at them. What we do is measure, examine and treat. Meeghan Mackenzie, our Certified Lymphedema Therapist, can take girth measurements of both arms at fixed landmarks and convert them to volume, compare them with any baseline you have, and keep a record so that a change in year three is caught against year one. If lymphedema is confirmed, treatment is complete decongestive therapy; if your team recommends a sleeve, we fit it, and the Learning Centre explains how compression garments are chosen. Many people in this situation are also recovering from a mastectomy or reconstruction, and the lymphatic side of that is covered in lymphatic care after mastectomy and reconstruction.

Questions people ask

Does radiation to the nodes raise my lymphedema risk even if I only had a sentinel node biopsy?

Yes, by roughly double in the best prospective data. In the McDuff cohort, sentinel biopsy with regional node radiation carried a five-year rate of 12.2% against 5.6% for sentinel biopsy alone in pooled studies, and the onset peak was the latest of any group, at 36 to 48 months. Keep an eye on the arm for years, not months.

Is radiation to the armpit safer than a dissection for lymphedema?

In the AMAROS trial, yes. Women with a positive sentinel node were randomized to axillary dissection or axillary radiotherapy; at five years lymphedema was recorded in 24.5% after dissection and 11.9% after radiotherapy, with no difference in survival at ten years. Whether that choice applies to you is a question for your surgeon and radiation oncologist together.

How long after regional node radiation can lymphedema still start?

Late onset, beyond twelve months, was specifically associated with regional node radiation in the McDuff cohort, with peaks at 18 to 24 months after dissection plus radiation and 36 to 48 months after sentinel biopsy plus radiation. The NLN recommends screening continue for at least five years. Lymphedema risk never fully closes, but those windows are where attention pays most.

Can a lymphedema therapist tell me which nodes were in my field?

No, and you should not rely on us to. Fields, doses and whether the supraclavicular or internal mammary nodes were included are the radiation oncologist's to explain, and the figures on this page vary by field. Ask for a copy of your treatment summary and bring it to your first lymphedema assessment.