Radiation therapy (radiotherapy) and lymphedema risk

What is radiation therapy (radiotherapy)?

Radiation therapy — also called radiotherapy — is a major treatment modality for cancer that uses high‑energy ionizing radiation to damage the DNA of tumor cells, thereby preventing their division and growth. Modern radiotherapy is precise: it focuses the radiation on the target area while sparing surrounding healthy tissues when possible. This is achieved with imaging techniques (CT, MRI), 3D planning and intensity‑modulated radiation therapy techniques (IMRT, VMAT).

Radiotherapy is one of the three main pillars of cancer treatment alongside surgery and systemic therapies (chemotherapy, targeted biological therapy, immunotherapy, hormonal therapy). Globally, more than 50% of cancer patients receive some form of radiation therapy.

When is radiotherapy used?

Radiation therapy is used in three main scenarios as part of a cancer treatment plan:

• Curative intent: to eradicate the tumor completely, often as an alternative to or in addition to surgery. Typical examples: breast cancer, prostate cancer, cervical cancer, head and neck cancers.
• Adjuvant (supplementary) therapy: after surgery to destroy residual microscopic tumor cells and reduce the risk of recurrence.
• Palliative (symptom‑relieving) therapy: to alleviate pain, bleeding or other symptoms in advanced, incurable disease.

From the perspective of lymphedema risk, the critical factor is whether the irradiated area involves regional lymphatic regions. For example, breast cancer treatment often includes irradiation of the axillary (underarm) lymphatic region, which is a major risk factor for arm lymphedema (BCRL). Similarly, pelvic tumor irradiation (cervical, prostate) increases the risk of lower‑limb lymphedema, while head and neck irradiation may lead to cervical and facial lymphedema.

Radiotherapy and the risk of lymphedema

Radiation increases the risk of lymphedema because ionizing radiation damages not only tumor cells but also nearby lymphatic vessels and lymph nodes. Radiation‑induced changes include:

• Acute inflammation in the treated area, which over weeks to months can evolve into subacute and then chronic processes.
• Radiation fibrosis — scarring of connective tissue causing narrowing or obstruction of lymphatic lumens.
• Lymph node damage — reduced or lost function of lymph nodes within the irradiated field.
• Microvascular injury — endothelial damage in small blood and lymphatic vessels that progressively impairs fluid exchange.

An important feature is that lymphedema 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 edema onset. This "late lymphedema" is particularly problematic because patients may not link new symptoms to past oncologic treatment and therefore seek care late.

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

Breast cancer‑related lymphedema (BCRL) – the most common radiation‑associated lymphedema

Breast cancer‑related lymphedema (BCRL) is the most frequent and best‑studied form of radiation‑associated lymphedema. Between 20–30% of breast cancer patients will develop BCRL during their lifetime — the risk is especially high in those who:

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

The good news: much of this risk is preventable. Contemporary clinical practice favors sentinel lymph node removal (instead of full axillary dissection when indicated), and postoperative prophylactic pneumatic compression significantly reduces BCRL incidence.

Other radiation‑associated lymphedemas

Although BCRL is the most common and best researched form, radiotherapy can cause lymphedema in other anatomical regions as well:

• Head and neck lymphedema: after treatment of head and neck cancers (oral, pharyngeal, laryngeal, tongue tumors) swelling may occur in the face, neck and submandibular region. Clinical trials have also demonstrated the effectiveness of at‑home advanced pneumatic compression devices (APCD) in this area.
• Lower‑limb lymphedema after pelvic cancers: irradiation of pelvic lymphatic regions during treatment of cervical, prostate or endometrial cancers can lead to chronic lower‑limb swelling.
• Genital lymphedema: pelvic irradiation can less commonly cause swelling of the scrotum or vulva.
• Peritoneal and abdominal lymphedema: after extensive abdominal or retroperitoneal irradiation, often presenting as chyloperitoneum (chyle accumulation).

Radiotherapy: preparation and treatment process

Planning and delivering radiotherapy is a multistep process that typically begins with 1–2 weeks of preparation:

1. Consultation with a radiation oncologist. Determination of tumor type, extent and patient‑tailored treatment goals. Review of prior diagnostics (CT, MRI, PET‑CT).
2. Planning CT (simulation CT). Imaging is performed with the patient in the exact treatment position (using immobilization devices) to plan the radiation fields.
3. 3D planning. The radiation physicist and oncologist define doses and field arrangements using computer‑based planning.
4. Treatment sessions. With conventional fractionation, one session daily, usually five days a week. Sessions are short (10–30 minutes) and outpatient.

Total treatment duration depends on tumor type, typically 3–8 weeks. Adjuvant radiotherapy for breast cancer commonly lasts 5–6 weeks, pelvic irradiation 7–8 weeks, while hypofractionated protocols may be 1–3 weeks.

What to expect? Side effects and lymphedema risk

Radiotherapy side effects are divided into acute (during and immediately after treatment) and late (months to years later). Lymphedema typically belongs to the late group.

Acute side effects (weeks):

• Redness, peeling, sensitivity at the treated area,
• fatigue, general weakness,
• nausea (with abdominal or pelvic irradiation),
• mucosal inflammation (oral cavity, bronchi, bladder, rectum depending on the target),
• acute lymphatic congestion in the treated region (usually transient).

Late side effects (months–years):

• Chronic lymphedema in the irradiated lymphatic region,
• radiation fibrosis (connective tissue scarring) in the treated area,
• skin changes (atrophy, telangiectasias),
• organ dysfunction depending on the target (e.g. cardiac damage with left‑sided breast irradiation, pulmonary fibrosis with thoracic irradiation).

Measures taken during and immediately after treatment can reduce lymphedema risk. Early mobilization, protecting the treated limb from injury and infection, and prophylactic compression garments are recommended — in consultation with your treating physician.

How can radiation‑associated lymphedema risk be reduced?

Early detection and preventive measures are key to preventing chronic lymphedema after radiotherapy or limiting its progression if it develops. The following six‑step, evidence‑based approach is recommended:

1. Early detection. Regular measurement of the irradiated limb with a tape measure or bioimpedance at the same points, preferably starting during treatment. A circumference difference >2 cm or rising bioimpedance is an early sign.
2. Prophylactic compression garment. Individually fitted compression garment, class II (23–32 mmHg) stocking/sleeve during and after radiotherapy, discussed with the treating physician.
3. Prophylactic pneumatic compression. Based on Su 2025 meta‑analysis: ≤40 mmHg, >2 weeks, started within ≤24 months after surgery/radiation. Feasible with a home Power Q device.
4. Early complex decongestive therapy (CDT). If swelling appears, prompt specialist consultation (lymphologist, lymphedema therapist) and initiation of CDT.
5. Lifestyle measures. Avoid deep injuries, punctures, phlebotomy and blood pressure measurement on the irradiated limb. Maintain hydration and moderate sodium intake.
6. Long‑term specialist follow‑up. In addition to oncologic follow‑ups, annual lymphology assessments — even if asymptomatic, as late lymphedema can appear 5–10 years after treatment.

Detailed home practical protocols — compression, IPC, self‑massage, exercise — are described in the Lymphedema treatment at home guide. For precise device selection see the Lymphatic massage device – multi‑indication hub, and the differences between manual and device‑assisted lymphatic drainage are explained in the Lymphatic drainage — manual and mechanical lymphatic massage guide.

Outcomes and long‑term follow‑up

Modern radiotherapy outcomes are excellent depending on tumor type: breast cancer can be effectively controlled locally, 5‑year survival for head and neck cancers has improved significantly, and curative results for pelvic tumors continue to improve. Thus, treatment saves lives.

Long‑term quality of life, however, often depends not only on cancer‑free survival but also on control of treatment‑related side effects — including chronic lymphedema. The good news is that complex decongestive therapy, at‑home pneumatic compression and modern microsurgical reconstructions (LVA, VLNT) together enable irradiated patients to maintain good long‑term quality of life.

A detailed overview of surgical reconstruction options is available in the Lymphatic reconstruction surgery – types and indications guide, and a clinician’s personal perspective in the interview with Dr. Balázs Mohos.

Further guides on the topic

Related guides in the cluster:

• Lymphedema – forms, causes and stages – pillar guide
• Lymphedema treatment at home – conservative treatment protocol
• Lymphatic drainage — manual and mechanical lymphatic massage – physical methods
• Lymphatic reconstruction surgery – surgical overview
• Interview with Dr. Balázs Mohos – specialist opinion
• Lymphatic massage device – multi‑indication hub – device selection
• Lymphatic massage device – what it’s for and how to choose – technical guide

Coming soon:

• Breast cancer‑related lymphedema (BCRL) – detailed clinical management (in preparation)
• Lymphedema stages (ISL 0–3) – stage‑specific guide (in preparation)