Radiotherapy uses carefully targeted beams of high-energy radiation to destroy any cancer cells that may remain in the breast, chest wall, or surrounding lymph node areas after surgery. It is a local treatment, meaning it acts on a specific targeted area rather than throughout the whole body, and it is one of the most important tools in reducing the risk of breast cancer returning after surgery.

For the majority of women who have breast-conserving surgery (lumpectomy), radiotherapy to the remaining breast tissue is a standard and essential part of treatment. It is the reason that lumpectomy achieves equivalent long-term survival outcomes to mastectomy and is not a compromise in cancer control. For some women who have had a mastectomy, post-mastectomy radiotherapy is also recommended.

Radiotherapy is delivered by a radiation oncologist, who specialises in the use of radiation for cancer treatment. At Breast & Surgical Oncology at The Poche Centre, your surgeon works closely with radiation oncologists across our hospital network, and your case is reviewed at the multidisciplinary team meeting before a referral for radiotherapy is made. Your radiation oncologist will then meet with you to explain your treatment in full, answer your questions, and plan the most appropriate approach for your situation.

Who Is Radiotherapy Recommended For?

Radiotherapy is not required for every patient with breast cancer. The decision is made by the multidisciplinary team based on the type of surgery performed, the characteristics of the tumour, and the individual patient's circumstances.

After breast-conserving surgery (lumpectomy), radiotherapy to the remaining breast tissue is recommended for almost all patients. The radiation targets any microscopic cancer cells that may remain in the breast after surgery, reducing the risk of the cancer returning locally (in the breast) by approximately two-thirds. The combination of lumpectomy and radiotherapy consistently achieves equivalent survival outcomes to mastectomy alone and is the internationally accepted standard of care for early-stage breast cancer.

After mastectomy, post-mastectomy radiotherapy (PMRT) is recommended in higher-risk situations. These include cases where the tumour was large (generally greater than 5 cm), where four or more axillary lymph nodes were involved, where the surgical margins were close or involved, or in some cases where one to three lymph nodes were involved alongside other high-risk features. PMRT targets the chest wall and, where relevant, the regional lymph node basins.

Nodal irradiation — radiotherapy extended to cover the axillary lymph nodes, internal mammary nodes, and supraclavicular nodes — is recommended in patients where lymph node involvement is confirmed or where there is a significant risk of regional lymph node disease. The extent of nodal irradiation is determined by the multidisciplinary team based on surgical and pathological findings.

Radiotherapy is not routinely recommended for some very low-risk breast cancers, particularly in older patients with small, hormone receptor-positive, node-negative tumours. Your radiation oncologist will discuss whether the benefits of radiotherapy outweigh the potential side effects for your specific situation.

The Radiotherapy Planning Process

Before treatment begins, a careful and detailed planning process takes place to ensure the radiation is targeted precisely to the correct areas while minimising dose to the surrounding normal tissues, particularly the heart and lungs.

Simulation and CT planning — you will attend a planning appointment (sometimes called a simulation) at the radiotherapy department before your treatment starts. A CT scan of your chest is taken in the exact position you will lie in during treatment, with your arm raised above your head. Small permanent tattoo dots or temporary marks are made on your skin to allow the treatment team to precisely position you the same way for every session. This meticulous planning ensures that the radiation beam consistently targets the correct area throughout the entire course of treatment.

Radiation planning — the radiation oncologist and a team of medical physicists and radiation therapists use the CT planning scan to design your individual treatment plan. They map out the precise area to be treated, calculate the dose required, and optimise the beam angles to maximise coverage of the target tissue while minimising radiation exposure to the heart, lungs, and opposite breast.

Heart-sparing techniques — modern radiotherapy planning uses a range of approaches to reduce the dose of radiation reaching the heart, which is particularly important for left-sided breast cancers. These include deep inspiration breath-hold (DIBH), where you hold a deep breath during each treatment to move the heart away from the chest wall; intensity-modulated radiotherapy (IMRT), which shapes the radiation beam to conform closely to the treatment area; and prone positioning for selected patients. Your radiation oncologist will explain which techniques are most appropriate for your treatment.

What Happens During Radiotherapy Treatment?

Radiotherapy is delivered as an outpatient treatment, meaning you attend the radiotherapy department for each session and go home the same day. No hospital admission is required.

Each treatment session (fraction) takes only a few minutes, though the total appointment time is longer to allow for precise positioning and verification. You will lie still on a treatment table in the same position as during your planning session, and the radiation therapists will align the treatment machine carefully before leaving the room to deliver the treatment. The process is completely painless and you will feel nothing during the radiation itself.

Between sessions, you go about your normal life. Most patients are able to continue working throughout radiotherapy, though fatigue may make some adjustment necessary.

Radiotherapy Schedules and Techniques

The number of radiotherapy sessions (fractions) and the schedule have changed significantly in recent years, and modern regimens are shorter and more convenient than those of the past.

Hypofractionated radiotherapy delivers a higher dose per fraction over a shorter number of treatments and is now the standard approach for whole-breast radiotherapy in most patients. A typical course involves fifteen treatments given daily over three weeks, or sixteen treatments over about three and a half weeks. Large clinical trials have established that hypofractionated schedules achieve equivalent cancer control and similar side effect profiles to the older longer courses of twenty-five fractions over five weeks.

Standard fractionation (twenty-five fractions over five weeks) is still used in some situations, particularly where nodal irradiation is required or in certain tumour types where longer schedules are preferred.

The boost dose is an additional dose of radiation delivered specifically to the area of the breast where the tumour was removed (the tumour bed), following the whole-breast course. The boost is given as an additional five to eight sessions and is recommended particularly for younger patients and those with higher-risk tumours. It further reduces the risk of local recurrence in the treated area. The tumour bed is identified using the biopsy clip, surgical clips, and imaging.

Partial breast irradiation (PBI) targets only the region of the breast around the tumour bed, rather than the entire breast. It is delivered over a shorter period and may be suitable for a carefully selected group of patients with low-risk, early-stage breast cancer. PBI can be delivered externally using radiation beams or as intraoperative radiotherapy (IORT), where a single dose of radiation is delivered directly into the tumour cavity during surgery. Eligibility for PBI is determined by your radiation oncologist based on your tumour characteristics and pathology.

Post-mastectomy radiotherapy and reconstruction — the interaction between radiotherapy and breast reconstruction is an important planning consideration covered in the breast reconstruction section of this website. In general, radiotherapy after implant-based reconstruction carries a higher rate of complications (including capsular contracture and implant failure) than radiotherapy applied to the native chest wall. This timing consideration influences the sequencing of reconstruction and radiotherapy in your overall treatment plan.

Side Effects of Radiotherapy

Radiotherapy to the breast is generally well tolerated, and for most patients its side effects are manageable. Your radiation oncologist and treatment team will monitor you closely throughout treatment and provide guidance on managing any side effects that develop.

Short-Term Side Effects

Skin reaction is the most common and expected short-term effect of breast radiotherapy. The skin in the treatment area typically becomes red, dry, and irritated over the course of treatment, similar in appearance to sunburn. Most patients experience mild to moderate skin reaction. More severe reaction with moist desquamation (blistering or peeling of the skin) can occur, particularly in areas where skin folds, such as under the breast or in the armpit. Your radiation oncology team will provide specific skincare guidance and products, typically including regular use of a plain, fragrance-free moisturiser throughout treatment, gentle washing, and protection of the treated area from sun and friction.

Fatigue is very common during radiotherapy and tends to build gradually over the course of treatment, often peaking in the final week or two. It is distinct from chemotherapy-related fatigue in character and timing. Gentle exercise, adequate sleep, and pacing daily activities help manage radiotherapy fatigue. Most patients find their energy returns gradually in the weeks to months after treatment ends.

Breast swelling and tenderness can develop during or after treatment and may persist for several months before gradually improving. It is important to know that breast tenderness and firmness can increase for the first few months after radiotherapy finishes before it improves — this is a normal part of the healing process and not a sign that the cancer has returned.

Armpit discomfort and temporary arm stiffness may occur, particularly when the axilla is included in the radiotherapy field.

Longer-Term Side Effects

Breast changes over time are common and expected after radiotherapy. The treated breast may become firmer, denser, and slightly smaller over the months and years following treatment as the radiation causes a degree of fibrosis (scar tissue formation). Some women also notice a mild change in the appearance or colour of the breast skin. These changes are generally stable and do not worsen significantly beyond the first two years.

Lymphoedema — swelling of the arm from impaired lymphatic drainage — is a risk when the axillary lymph nodes are irradiated, particularly in women who have also had axillary surgery. The risk is higher when both axillary surgery and axillary radiotherapy are performed. Your treatment team will monitor for lymphoedema and provide referral to a lymphoedema physiotherapist if needed.

Cardiac effects — radiotherapy to the left breast carries a small long-term risk of effects on the heart, including a modest increase in the risk of ischaemic heart disease in the decades following treatment. Modern heart-sparing techniques (including DIBH and precise treatment planning) have substantially reduced this risk compared to older radiotherapy approaches. Your radiation oncologist will discuss what cardiac risk-reduction measures are included in your treatment plan.

Radiation-related fatigue in the longer term is uncommon with modern regimens and doses.

Rib fracture is a rare complication of breast radiotherapy and is more likely in patients who have also received chemotherapy.

Radiation-induced secondary cancers are a very rare but recognised long-term risk. The absolute risk is very small and is far outweighed by the benefits of radiotherapy in preventing breast cancer recurrence for the patients in whom it is recommended.

Practical Skincare During Radiotherapy

Following your radiation oncology team's skincare guidance closely throughout treatment reduces the severity of skin reaction and supports healing. General principles include using a plain, fragrance-free moisturiser generously and frequently (at least twice daily) to the treatment area from the start of radiotherapy; avoiding perfumed soaps, deodorants, and skin products on the treated area; washing the area gently with lukewarm water; wearing soft, loose-fitting clothing over the treated area to minimise friction; protecting the treated skin from sun exposure; and avoiding swimming pools, spas, and the ocean during treatment as chlorine and salt water can irritate the treated skin. If your skin becomes very sore or breaks down, contact your radiation oncology team promptly — there are effective treatments for more severe skin reactions.

Radiotherapy and Your Surgical Team

Your surgeon remains involved throughout your radiotherapy period. Any concerns about the breast, surgical site, or wound healing during radiotherapy should be discussed with your breast care nurse or surgeon. Radiotherapy can occasionally affect wound healing in the early months after surgery, and any changes that concern you should be assessed promptly.

After completing radiotherapy, you will return to your surgical team for ongoing follow-up and monitoring of the breast.