Breast cancer is a disease that affects about 1 in 9 women in Belgium before the age of 75, but it is nowadays a highly curable disease for a majority of people. Radiotherapy plays an essential role in the treatment of breast cancer. When the breast is preserved during surgery, the addition of radiotherapy leads to a clear reduction in the risk of local relapse, i.e. relapse in the treated breast or the draining lymph nodes. For every 4 local relapses prevented, 1 breast cancer death can be prevented. This survival benefit is also seen after mastectomy, but only in lymph node positive patients. Because of the high survival rates, most patients live for decades after their treatment. High-quality treatment should therefore not only focus on curing the disease but also on reducing late side effects and improving quality of life of the long-term survivors. The introduction of innovative radiotherapy technology fulfils these aims: it allows improving the dose delivery to the breast and if needed lymph nodes, but also allows better sparing of the adjacent normal tissues such as the heart, lungs, oesophagus, thyroid and contralateral breast.
In breast cancer radiotherapy, a major concern is radiation injury to the heart which might even lead to death due to cardiac disease in a small number of cases. It has been shown that this risk is closely related to the radiation dose delivered to the heart. There are several modern radiation techniques available that significantly spare the heart from receiving high radiation doses. One possibility is the use of more beam angles, by which the dose can be spread out over a larger part of the body thus reducing the high dose regions to the heart. These techniques are especially useful in patients with an unfavourable position of the heart (e.g. funnel chest) or when treating the lymph node regions. This approach is also efficient to reduce the high dose regions to the ipsilateral lung since breast cancer survivors also have an excess risk of lung cancer mortality. Again, this risk is related to the lung dose. For smokers the excess risk is significantly higher than for non-smokers.
Innovations in breast radiotherapy can be simple. One option is to irradiate only the part of the breast where the tumour was located, i.e. partial breast irradiation instead of whole breast irradiation. However, this option is restricted to a small group of carefully selected breast cancer patients with a low risk of relapse. Another option, available for a larger group of patients, is prone treatment which means that the patients is treated while lying on the belly instead of on the back. In prone breast radiotherapy, the breast hangs down through an aperture in the treatment table. By gravity, the breast falls away from the healthy organs such as the heart and lungs. Both partial breast irradiation and prone treatment are promising techniques to reduce the dose to heart and lungs. A third simple option is to use respiration as a help to reduce the heart dose. When breathing in, the heart moves towards the feet of the patient and the distance between the breast and the heart is increased. Delivering radiation while breathing in and interrupting treatment while breathing out, is a strategy that can be used to lower radiation to the heart.
With increasing cure rates, quality of life of long-term breast cancer survivors becomes more and more important. Breast radiotherapy can result in side effects to the skin and suboptimal cosmetic results. It has been shown that these side effects have an impact on patients’ quality of life. With intensity-modulated radiation techniques (IMRT) the dose can be tailored to the specific shape of the breast. This leads to less skin effects and a better cosmetic outcome. Prone breast radiotherapy and partial breast irradiation are other strategies to reduce the risk of changes in breast appearance.
Innovative breast radiation techniques have also made it possible to reduce the number of treatment sessions. In the past at least 25 daily sessions, 5 times a week, were needed, while nowadays, 13-16 sessions have become state-of-the-art for breast irradiation without lymph node irradiation. Lowering the number of treatment sessions has obvious advantages for the patient and the radiotherapy department: a reduction of the overall treatment time with less transportations to the department and shorter waiting lists.
In summary, breast radiotherapy saves lives and innovative techniques increase that benefit by reducing the rate of non-breast cancer death, i.e. death due to treatment toxicity. Use of modern techniques also results in less long-term side effects and a better quality of life in breast cancer survivors.
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