Research led by a Cambridge oncologist has found that targetting radiotherapy around the tumour site is just as effective as treating the whole breast for patients with low risk breast cancer, and has fewer side effects.
Giving radiotherapy to the whole breast after breast-conserving surgery is currently the standard treatment for women, even those who have a low risk of the disease coming back. However, such treatment may produce side effects, such as changes in the appearance of the breast, which may also become hard to the touch. These side effects can result in physical symptoms, such as discomfort, as well as causing psychological distress.
Dr Charlotte Coles, CUH consultant clinical oncologist, and colleagues from 30 radiotherapy centres across the UK recruited 2018 patients aged 50 or older who had early breast cancer with a low risk of returning.
Dr Coles said: “Five years after treatment we found clear evidence of benefit to patients in the partial breast radiotherapy group in terms of reduced side effects. These benefits were reported by the patients themselves, and also by their doctors. We also found very low rates of local recurrence in all the groups. However, we intend to continue to follow up the trial patients for at least ten years because we know that cancer recurrence can still occur more than five years after completion of treatment.”
The study, funded by Cancer Research UK and coordinated by the Institute of Cancer Research, was presented at the European Breast Cancer Conference in Amsterdam in March. The trial divided the women into three groups following breast conserving surgery: one had full dose radiotherapy to the whole breast – the current standard treatment; the second group had the full dose of radiotherapy to the area where the tumour had been and a lower dose to rest of the whole breast; and the third group received the full dose to the area where the tumour had been, but were given no radiotherapy to the rest of the breast.
Five years after their treatment, only 1 per cent or less of women in each group had a recurrence of their cancer in their breast, according to the researchers.
Dr Coles added: “We hope that the evidence of benefit we have shown in this trial will bring about a change in practice worldwide, and enable very many more women with early breast cancer to undergo this treatment. At a time when breast cancer mortality rates are falling and more women are surviving their cancer, we believe it is particularly important to keep any toxicity from treatment to the absolute minimum.”
The researchers believe that the use of partial breast irradiation with intensity modulated radiotherapy (IMRT) benefits patients in two ways. The IMRT produces an even dose of radiation across the breast and minimises the chances of hotspots of unwanted high dose that could increase the risk of late side effects in normal tissue. The partial breast irradiation also has an effect because it spares part of the breast from the treatment. And, because the patients in the trial were at low risk of recurrence, they could be spared an additional boost dose to the area where the cancer was taken out which can cause more side effects.
This form of IMRT is a simple, quick and cheap technique, which can be carried out with all standard radiotherapy equipment. It is now standard practice in the majority of radiotherapy centres in Europe.
Dr Coles said: “The radiotherapy beams have a glancing orientation that covers the breast but limits the dose to the lung and also the heart in left-sided breast cancers. There is, therefore, no concern about a higher volume of low dose radiation to normal tissue, which is sometimes a worry in more complex types of IMRT.”
In addition to the ten year follow-up, the researchers also intend to investigate in more depth the patient-reported outcome measures (PROMS). In addition to specific questions about the patient’s breast and related symptoms, which have been shown already to be better with partial breast radiotherapy, they also include more general questions about quality of life.
“This is another area where we would expect to see better results from the partial breast radiotherapy/IMRT group,” added Dr Coles.
