TL;DR: Lymphedema, a chronic swelling of the arm or other body region, develops in roughly 1 in 5 breast cancer survivors and is one of the most distressing long-term complications of cancer treatment. Hyperbaric oxygen therapy (HBOT) has been studied for chronic, radiation-related lymphoedema since the early 2000s, with several small clinical trials reporting reductions in arm volume, improvements in tissue softness, and better quality of life. The evidence base is small but consistent. This Daffodil Month, we explain what lymphedema is, what the research says about HBOT, and what Canadian patients need to know.

Estimated reading time: 7 minutes

What Is Lymphedema?

Lymphedema is the abnormal build-up of lymph fluid in the soft tissues, most often the arm, hand, or chest wall after breast cancer treatment, but it can also develop in the leg, trunk, head and neck, or genital area depending on which lymph nodes were involved. The lymphatic system normally drains protein-rich fluid out of tissues; when surgery or radiation damages this drainage network, fluid accumulates and the tissue becomes progressively swollen, heavy, and fibrotic.

  • Early signs: a feeling of heaviness, tightness, or aching in the limb; rings, sleeves, or watches feeling tight; mild visible swelling that comes and goes
  • Established lymphedema: persistent visible swelling, reduced range of motion, skin thickening, recurrent infections (cellulitis)
  • Late stage: hardening of the tissue (fibrosis), loss of skin elasticity, severe limitation of function

The Canadian Cancer Society notes that approximately 1 in 5 women treated for breast cancer will develop arm lymphedema, with risk highest after axillary node dissection combined with radiation. During Daffodil Month, it is important to recognise lymphedema as a chronic, lifelong condition – and to know that adjunctive treatment options are being actively investigated.

Why Does Lymphedema Develop After Cancer Treatment?

Two cancer treatments are most commonly implicated in lymphedema:

  1. Lymph node surgery (sentinel node biopsy or axillary lymph node dissection) physically removes part of the lymphatic drainage pathway
  2. Radiation therapy to the regional nodes causes long-term damage to the small lymphatic vessels and surrounding soft tissue, often years before symptoms appear

Radiation-induced lymphedema is a form of delayed radiation tissue injury – the same family of late complications that includes radiation cystitis, proctitis, and osteoradionecrosis of the jaw. The underlying problem is the same: progressive scarring and reduced blood supply (microvascular ischaemia) in tissue that received high doses of radiation. This shared mechanism is one reason hyperbaric oxygen therapy has been investigated as a possible treatment.

How Might HBOT Help Lymphedema?

HBOT delivers 100% oxygen at elevated atmospheric pressure, dissolving large amounts of oxygen directly into blood plasma. In tissue damaged by radiation – including the lymphatic vessels of the arm or chest wall – this elevated oxygen environment is thought to support several recovery processes:

  • Stimulating new blood vessel growth (angiogenesis) in irradiated soft tissue, restoring perfusion to areas with chronic ischaemia
  • Reducing fibrosis by modulating the activity of fibroblasts and the extracellular matrix
  • Promoting lymphangiogenesis – new lymphatic vessel formation – in animal and pre-clinical models
  • Improving tissue elasticity, which patients often report as the arm feeling softer or less tight after a treatment course
  • Reducing the inflammatory environment that drives chronic swelling

HBOT is not a replacement for the standard cornerstones of lymphedema care – complete decongestive therapy (CDT), compression garments, manual lymph drainage, and exercise. Instead, it is being studied as an adjunctive treatment, particularly in patients whose lymphedema is associated with prior radiation therapy and is not well controlled with conservative care alone.

What Does the Research Show?

Hyperbaric oxygen for chronic arm lymphoedema after breast cancer has been studied in a series of small clinical trials over the past two decades. The findings are modest but generally consistent.

2004 – First Phase II Trial

An early non-randomised Phase II trial in patients with chronic arm lymphoedema and tissue fibrosis after breast cancer radiotherapy reported reductions in arm volume and improved tissue softness following a course of HBOT. The trial laid the groundwork for further investigation but lacked a control group.

2010 – Randomised Phase II Trial

A larger randomised Phase II trial compared HBOT against best standard care in patients with chronic, radiation-associated arm lymphoedema. The study found measurable improvements in arm volume and patient-reported symptoms in the HBOT group, though absolute benefits were modest and not all secondary endpoints reached significance.

2020 – HBOT vs Complex Decongestive Therapy

A more recent pilot study compared the short-term effects of HBOT with complex decongestive therapy, the current standard of care. Both treatment groups improved, demonstrating that HBOT is a credible adjunct rather than a replacement for established therapies.

2023 – Early Intervention Trial

A 2023 explorative clinical trial investigated whether starting HBOT earlier in the course of post-radiation arm lymphedema could improve outcomes. Early-intervention HBOT was associated with arm volume reductions and improved quality-of-life scores, suggesting that timing may matter.

2025 – Long-Term Follow-Up Case Series

The most recent published evidence is a 2025 prospective case series of irradiated breast cancer patients with long-standing lymphedema. The investigators reported both short-term improvements and durable benefits at extended follow-up, suggesting the effects of HBOT in this population may persist beyond the immediate post-treatment period.

The current evidence is small in scale but consistent in direction: HBOT can produce meaningful, sometimes durable improvements in arm volume and quality of life for survivors with chronic, radiation-associated lymphedema. It is not a cure, and it does not replace conservative care – but it is a legitimate research-supported adjunct.

What Canadian Patients Need to Know

Lymphedema is not currently listed among Health Canada’s 14 recognised indications for hyperbaric oxygen therapy. The recognised radiation-injury indications are soft tissue radiation necrosis and radiation damage affecting bone, and lymphedema occupies a related but separate clinical category. As a result:

  • HBOT for lymphedema is generally not covered by provincial health plans in Canada, even where HBOT for other radiation-injury indications is covered
  • Treatment is typically self-funded at private hyperbaric clinics or accessed as part of a clinical trial
  • Patients should continue conservative care (compression, manual lymph drainage, exercise) regardless of any HBOT decision
  • A certified lymphedema therapist and the original treating oncology team should be involved in any decision to add HBOT to a care plan

The Canada Hyperbarics facility directory lists hospital-based and private hyperbaric programmes across Canada. Several private programmes have published patient outcomes for radiation-injury cohorts. Patients considering HBOT should ask any potential clinic about their experience with radiation-injury cases, the protocol they use, and the typical course length.

Frequently Asked Questions

How many HBOT sessions are typically used for lymphedema?

Published trials have used courses of 30 to 40 daily sessions at 2.0 to 2.4 ATA, similar to standard radiation-injury protocols. Specific protocols vary between centres and should be set by a hyperbaric medicine physician.

Can HBOT make lymphedema worse?

Across the published trials, HBOT has been generally well tolerated in this population. The most common side effects are mild middle-ear barotrauma and temporary myopia. Lymphedema worsening directly attributable to HBOT has not been a reported outcome, but compression garments and conservative care should continue throughout treatment.

Is HBOT safe after a cancer diagnosis?

Multiple safety reviews have concluded that HBOT does not promote tumour growth or recurrence. HBOT is widely used to treat late effects of cancer therapy. Patients with active malignancy should always discuss HBOT with their oncologist before starting treatment.

Will OHIP, MSP, or another provincial plan pay for this?

For lymphedema specifically, generally no. Provincial coverage is built around the 14 recognised conditions and does not currently extend to lymphedema as a stand-alone indication. Coverage may apply if a patient has a co-existing recognised indication (for example, soft tissue radiation necrosis in the same region). Confirm with the treating facility before assuming coverage.

Key Takeaway

Lymphedema after breast cancer treatment is common, chronic, and under-treated. The evidence for hyperbaric oxygen therapy is small but consistent: HBOT can produce measurable reductions in arm volume and improvements in symptoms for patients with chronic, radiation-associated lymphedema. It is an adjunct, not a replacement, for compression and complete decongestive therapy. Coverage in Canada is limited and most patients self-fund. Patients should pursue HBOT as part of a coordinated plan with their lymphedema therapist and oncology team.

References

This content is for informational purposes only and does not constitute medical advice. HBOT for lymphedema is an investigational use that is not currently listed under Health Canada’s recognised conditions for hyperbaric oxygen therapy. Patients should consult their oncologist, lymphedema therapist, and a certified hyperbaric medicine specialist before pursuing any HBOT-based treatment plan. Canada Hyperbarics is an independent educational resource and is not affiliated with any specific clinic or manufacturer.

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