Rare side effects of radiotherapy

Some side effects of radiotherapy are rare (or very rare) but can be serious.

Always contact your treating team if you experience any serious side effect. Tell them if you are worried about a new side effect or symptom.

Damage to the heart

When treating the left breast, a very small amount of the heart receives a very low dose of radiation.

This has become much less likely over the past 10 to 15 years due to:

• better technology that allows the radiation oncologist to minimise the dose to the heart.
• a technique called deep inspiration breath-hold (DIBH) that moves the heart away from the radiation area.

Read about Radiotherapy treatment.

Damage to the lungs

Damage to the lungs is a rare complication of radiotherapy to treat breast cancer. Due to improvements in how radiotherapy is delivered, problems are very uncommon.

Inflammation of the lung (‘radiation pneumonitis’) can happen 1 to 3 months after radiotherapy. This usually settles over a few weeks.

The symptoms include dry cough, breathlessness and chest pain.

The risk of this developing depends on several things, such as:

• how much of the lung was treated with radiation
• whether treatment included lymph nodes above the collarbone (‘supraclavicular nodes’)
• previous chemotherapy
• taking Tamoxifen at the same time
• if you currently smoke.

Fibrosis is a condition that can appear months to years after you finish radiotherapy treatment. The cells that line the lungs can harden and thicken.

This causes ongoing ('chronic') breathlessness and dry cough. These symptoms can be worse if you already have a lung condition such as asthma, or if you smoke. Less than 1% of patients will experience this side effect.

Nerve damage

If the nerves are damaged in the arm of the treated side, you may have:

• tingling
• pain
• numbness
• loss of movement.

Rib weakness/fracture

In rare situations, radiation can make the rib bones weaker, causing fractures.

Development of a second cancer

This is the rarest of all of the side effects. This is not a new deposit of breast cancer, but a new cancer caused by the radiotherapy.