What’s new in breast cancer radiotherapy?

Dr Maríza Tunmer tells us more about how the art of radiotherapy is being refined more and more, resulting in better treatment decisions for every patient.

Photo caption: A model demonstrating a patient’s position on the breast board of a linear accelerator machine, used to deliver external beam radiotherapy. * Courtesy of WITS Donald Gordon Radiation Oncology Unit.

Why is radiotherapy used?

When a patient requires radiotherapy for breast cancer (BC), it is done to reduce the risk of the tumour recurring in the breast, chest wall or in the draining lymph nodes (glands). There is also a small but significant reduction in the risk of dying from metastatic BC.

Traditional indications

There are different indications for giving radiotherapy to BC patients and, as we gain more insight from studies and improved technologies, these indications need to change. Traditionally, the main indications have been:

  • For all patients who have had breast conservation surgery (when only the breast lump or a section of the breast is removed).
  • For breast tumours 5cm or larger (tumour stage T3) or those involving the chest wall or skin (tumour stage T4).
  • For involved lymph nodes, initially for four or more nodes but more recently also for patients with one to three nodes.
  • For positive or close margins following surgery.

These days, as treatments are being tailored for the individual patient, there may be exceptions to the above indications and patients could be spared irradiation.

Conversely, there may also be other reasons why radiotherapy could be considered, such as when worrying features related to the hormonal markers and other features are found when the tumour is assessed in the laboratory.

Association guidelines

It’s important to note that while most associations have similar guidelines, there are subtle differences and this may complicate some treatment decisions. Examples of professional bodies that publish guidelines include, but are not limited to, the American Society of Radiation Oncology (ASTRO), UpToDate, and the National Clinical Cancer Network (NCCN). Many of these guidelines may be found online.

• Using shorter schedules of radiotherapy – hypofractionated radiotherapy and accelerated partial breast irradiation

Whole breast radiotherapy (WBRT) has usually been given over five to seven weeks, on consecutive days, Mon to Fri, for 25 – 28 treatments, followed, in most cases, by a ‘boost’ to the tumour bed for another five to eight days.

Hypofractionated WBRT 

For the last few years, this – a shorter schedule of radiotherapy – has been used for patients with early breast cancer requiring radiotherapy only to the breast (as opposed to the breast and the lymph nodes). This entails giving a slightly higher dose of radiotherapy per day for 15 – 16 days, again sometimes followed by a ‘boost’, so that the overall treatment time is reduced to about three to four weeks.

Studies have shown that not only are the cancer outcomes similar to the standard longer course, but the early side effects (skin reaction and breast pain), quality of life effects (convenience and fatigue), and the late cosmetic outcomes are better than the longer course. This has led to many international associations endorsing that the hypofractionated schedule is a recommended treatment for most patients with early breast cancer requiring radiotherapy to only the breast.

Accelerated Partial              

Breast Irradiation (APBI)

For some women, treating only the tumour bed may be considered as a reasonable alternative to WBRT. This entails delivery of an even higher dose of radiotherapy over one to several days to only the area of the breast at highest risk of recurrence.

There are different ways of achieving this. Further studies are underway to confirm which patients are the best candidates for APBI. It’s not yet standard but may be considered, after careful discussion, in women 50 – 60 years or older with hormone-receptor positive; early stage tumours up to 2cm in size; with surgical margins of at least 2mm; and who don’t have other poor prognostic features on histology. It’s not suitable for patients who carry genetic abnormalities, such as BRCA mutations.

• Omitting breast radiotherapy completely in patients

As mentioned, following breast conserving surgery, radiotherapy is usually required to reduce the risk of recurrence in the breast. Recently updated guidelines have provided recommendations for possible exceptions to this rule, following studies that have shown that some patients may have a very low-risk of recurrence, even without radiotherapy.

  • Older women (usually defined as over 65 – 70 years of age) with hormone-receptor positive; early stage cancer with tumours up to 3cm; without lymph nodes involved; and who receive endocrine therapy.

It’s important to note that although the risk of a cancer recurring in the breast may be very low, it’s still higher than with radiotherapy, and this should be taken into account.

Selecting patients to treat with a ‘boost’

Most patients receiving WBRT also receive a ‘boost’ to the tumour bed over five to eight days. Recent evidence suggests that certain patients may not benefit from this – again usually older women with small, low-grade, hormone receptor-positive breast cancer who have clear margins following surgery. Guidelines are being refined regarding which patients benefit most from the boost dose and whom may be spared.

• Radiotherapy for large tumours, or when lymph nodes are involved, or following mastectomy with or without reconstruction

When tumours are 5cm or larger or involve the chest wall or skin, or when lymph nodes are involved, it becomes necessary to treat not only the breast but also the lymph node areas at risk, such as under the arm (axilla), or above and below the collar bone (clavicle), or the nodes under the ribs next to the breast bone (sternum).

In such cases, the recommendation remains to give the standard treatment over the five to seven weeks. Similarly, for patients who have had a mastectomy with or without reconstruction, there is less evidence to support the use of the shorter treatments and, in most cases, the standard long course of radiotherapy is still recommended.

• Radiotherapy for patients at high-risk of local recurrence

Some patients may not meet the usual criteria for radiotherapy. However, they may still be considered for treatment, if there are certain features that are particularly worrying, such young patients who have triple-negative disease (if the hormonal and other markers are negative). Though, this is not yet standard everywhere and while further studies are awaited, some of these patients may also be offered radiotherapy after careful discussion with the medical team.

For any breast cancer patient who may need radiotherapy, it is important to have a discussion with your doctor, regarding which radiotherapy schedule is best for you. Don’t hesitate to ask questions when something is unclear. It is important to understand all the risks and benefits before making decisions regarding treatment.

MEET OUR EXPERT – Dr Maríza Tunmer

Dr Maríza Tunmer is a specialist radiation oncologist. She consults from the WITS Donald Gordon Medical Centre but treats patients all over Johannesburg. She also works twice a week as a sessional consultant in the Department of Radiation Oncology at Charlotte Maxeke Johannesburg Academic Hospital, where she sees patients in the clinic and assists with the teaching of specialists-in-training.