Radiotherapy and the risk of lymphoedema

What is radiotherapy?

Radiotherapy – also known as radiation therapy – is one of the main treatments for cancer. It uses high-energy ionising radiation to damage the DNA of cancer cells and prevent them from dividing and growing. Modern radiotherapy is precise: it concentrates radiation on the target area while sparing the surrounding healthy tissues as much as possible. This is achieved with imaging techniques (CT, MRI), 3D planning and intensity-modulated radiotherapy (IMRT, VMAT) techniques.

Radiotherapy is one of the three main pillars of cancer treatment, alongside surgery and drug therapy (chemotherapy, targeted biological therapy, immunotherapy and hormone treatment). Globally, more than 50% of people with cancer receive some form of radiotherapy.

When is radiotherapy used?

Radiotherapy is included in a cancer treatment plan in three main situations:

• With curative intent: to destroy the tumour completely, often as an alternative or addition to surgery. Typical examples include breast cancer, prostate cancer, cervical cancer and head and neck cancers.
• As adjuvant treatment: after surgery, to destroy remaining microscopic cancer cells and reduce the risk of recurrence.
• As palliative treatment: in advanced, incurable disease, to relieve pain, bleeding or other symptoms.

From the perspective of lymphoedema risk, the critical factor is whether the irradiated area includes the regional lymphatic regions. During breast cancer treatment, for example, the axillary lymphatic region is often irradiated. This is a major risk factor for breast cancer-related lymphoedema (BCRL) of the arm. Similarly, radiotherapy for pelvic tumours (cervical or prostate cancer) increases the risk of lymphoedema in the lower limbs, while irradiation of head and neck tumours may lead to lymphoedema in the neck and face.

Radiotherapy and the risk of lymphoedema

Radiotherapy increases the risk of lymphoedema because ionising radiation damages not only cancer cells but also the surrounding lymphatic vessels and lymph nodes. Radiation-induced changes include:

• Acute inflammation in the treated area, which may gradually become a subacute and chronic process over weeks and months.
• Radiation fibrosis – narrowing or blockage of the lymphatic vessel lumen due to connective-tissue scarring.
• Lymph-node damage – the function of lymph nodes in the irradiated region is reduced or lost.
• Microvascular damage – the endothelium of small blood and lymphatic vessels is injured, gradually impairing fluid exchange.

An important feature is that lymphoedema may develop years AFTER radiotherapy. In clinical practice, symptoms appear within 2–5 years in about one third of patients, but 10–15 years may pass between treatment and the development of oedema. This “late lymphoedema” is particularly dangerous because people may no longer connect the symptoms with cancer treatment received years earlier and often seek medical advice too late.

The basic function of the lymphatic system and the consequences of damage are explained in detail in the guide Lymphoedema – forms, causes and stages.

Arm swelling after breast cancer (BCRL) – the most common radiation-associated lymphoedema

Breast cancer-related lymphoedema (BCRL) of the arm is the most common and clinically best-studied form of radiation-associated lymphoedema. Between 20–30% of people treated for breast cancer will develop BCRL during their lifetime. The risk is particularly high in those who:

• have undergone extensive axillary lymph-node removal (axillary lymphadenectomy),
• have had the axillary or supraclavicular region irradiated,
• have had recurrent local infection (erysipelas) in the arm on the operated side,
• have a higher BMI,
• received chemotherapy immediately after surgery.

The good news is that a substantial part of the risk can be prevented. Modern clinical practice favours sentinel lymph-node removal instead of complete axillary dissection where the indication allows, and postoperative prophylactic pneumatic compression significantly reduces the development of BCRL.

Other radiation-associated lymphoedemas

Although BCRL is the most common and best-studied form, radiotherapy may also cause lymphoedema in other anatomical regions:

• Head and neck lymphoedema: after treatment for head and neck cancers (mouth, throat, larynx and tongue tumours), the face, neck and chin area may swell. Clinical studies have also supported the effectiveness of advanced pneumatic compression devices (APCDs) at home in this area.
• Lower-limb lymphoedema after pelvic cancer: during treatment for cervical, prostate or uterine cancer, irradiation of the pelvic lymphatic regions may lead to chronic swelling of the lower limbs.
• Genital lymphoedema: pelvic irradiation may less commonly cause swelling of the scrotum or vulva.
• Peritoneal and abdominal lymphoedema: after extensive abdominal or retroperitoneal irradiation, often in the form of chyloperitoneum (chyle accumulation).

Radiotherapy: preparation and treatment process

Radiotherapy planning and delivery is a multi-stage process that typically begins with 1–2 weeks of preparation:

1. Consultation with the radiation oncologist. The tumour type, extent and personalised treatment goal are determined. Previous diagnostic scans (CT, MRI, PET-CT) are reviewed.
2. Planning CT (simulation CT). Imaging is performed with the patient in a precise position, using immobilisation devices, to plan the radiation field.
3. 3D planning. The radiation physicist and oncologist use computer-based planning to determine the radiation dose and field arrangement.
4. Treatment sessions. With conventional fractionation, there is usually one session a day, 5 days a week. Sessions are short (10–30 minutes) and are provided on an outpatient basis.

The full treatment lasts 3–8 weeks, depending on the type of tumour. Adjuvant radiotherapy for breast cancer, for example, typically lasts 5–6 weeks, pelvic irradiation 7–8 weeks, while hypofractionated protocols take 1–3 weeks.

What can you expect? Side effects and lymphoedema risk

The side effects of radiotherapy can be divided into two groups: acute symptoms (during and immediately after treatment) and late symptoms (months or years later). Lymphoedema usually belongs to the late group.

Acute side effects (weeks):

• Redness, peeling and sensitivity in the treated area,
• fatigue and general weakness,
• nausea (with abdominal or pelvic irradiation),
• inflammation of the mucous membranes (mouth, bronchus, bladder or rectum, depending on the target area),
• acute lymphatic congestion in the treated region (usually temporary).

Late side effects (months to years):

• Chronic lymphoedema in the irradiated lymphatic region,
• radiation fibrosis (connective-tissue scarring) in the treated area,
• skin changes (atrophy and telangiectasia),
• organ dysfunction depending on the target area (for example, heart damage after left-sided breast irradiation or pulmonary fibrosis after irradiation near the bronchi).

Steps taken during treatment and immediately afterwards are also important in reducing the risk of lymphoedema. Early mobilisation, protecting the treated limb from injury and infection, and prophylactic compression garments are recommended, in consultation with the treating doctor.

How can the risk of radiation-associated lymphoedema be reduced?

Early detection and preventive measures are key to preventing chronic lymphoedema after radiotherapy or stopping it from worsening if it develops. The following 6 steps are an evidence-based approach:

1. Early detection. Measure the limb on the treated side regularly with a tape measure or bioimpedance, at the same points, preferably starting during treatment. A circumference difference greater than 2 cm or a rising bioimpedance value is an early warning sign.
2. Prophylactic compression garment. An individually fitted stocking or arm sleeve in compression class II (23–32 mmHg), during and after radiotherapy, in consultation with the treating doctor.
3. Prophylactic pneumatic compression. Based on the Su 2025 meta-analysis: ≤40 mmHg, >2 weeks, within ≤24 months after surgery/radiotherapy. This can be carried out at home with a Power Q device.
4. Early complex decongestive therapy (CDT). If swelling nevertheless appears, seek early professional advice (from a lymphologist or lymphoedema therapist) and begin CDT.
5. Lifestyle measures. Protect the treated limb from deep injuries, punctures, blood sampling and blood-pressure measurement. Maintain hydration and moderate sodium intake.
6. Long-term specialist follow-up. Alongside oncology check-ups, have an annual lymphological assessment, even if there are no symptoms, because late lymphoedema may appear 5–10 years after treatment.

Detailed descriptions of practical home protocols – compression, IPC, self-massage and movement – are available in the guide Lymphoedema treatment at home. For help choosing the right device, see Lymphatic drainage device – multi-indication hub. The difference between manual and device-based lymphatic drainage is explained in Lymphatic drainage – manual and device-based lymphatic massage.

Outcomes and long-term follow-up

The results of modern radiotherapy are excellent, depending on the type of tumour: breast cancer can be treated effectively locally, 5-year survival for head and neck cancers has improved considerably, and curative treatment outcomes for pelvic tumours are also continually improving. Treatment can therefore save lives.

Long-term quality of life, however, often depends not only on cancer-free survival but also on controlling treatment-associated side effects, including chronic lymphoedema. The good news is that complex decongestive therapy, home pneumatic compression and modern microsurgical reconstruction (LVA, VLNT) can work together to help people treated with radiotherapy maintain a good quality of life over the long term.

A detailed overview of surgical reconstruction options is available in the guide Lymphatic reconstruction surgery – types and indications. For a personal view of clinical practice, read the interview with surgeon Dr. Balázs Mohos.

More in-depth guides on this topic

Related guides on radiotherapy and lymphoedema in this cluster:

• Lymphoedema – forms, causes and stages – pillar guide
• Lymphoedema treatment at home – conservative treatment protocol
• Lymphatic drainage – manual and device-based lymphatic massage – physical methods
• Lymphatic reconstruction surgery – surgical overview
• Interview with surgeon Dr. Balázs Mohos – specialist opinion
• Lymphatic drainage device – multi-indication hub – device selection
• Lymphatic drainage device – what is it for and how do you choose one? – technical guide

Guides coming soon:

• Arm swelling after breast cancer (BCRL) – detailed clinical treatment (in preparation)
• Lymphoedema stages (ISL 0–3) – stage-specific guide (in preparation)