ArticlesWhole-breast irradiation with or without a boost for patients treated with breast-conserving surgery for early breast cancer: 20-year follow-up of a randomised phase 3 trial
Introduction
Radiotherapy after breast-conserving treatment halves the chance of disease recurrence and reduces breast cancer mortality by about a sixth.1 However, uncertainty remains as to the radiation dose needed for patients treated with lumpectomy for early breast cancer. For this reason, the European Organisation for Research and Treatment of Cancer (EORTC) did a phase 3 randomised trial2 investigating the potential advantage of delivering a higher radiation dose to the tumour bed after whole-breast irradiation of 50 Gy in 5 weeks. 5318 patients with microscopically complete excision followed by whole-breast irradiation of 50 Gy were randomly assigned to receive either a boost dose of 16 Gy or no boost dose. The preliminary analysis after 5 years' follow-up suggested that the risk of ipsilateral breast tumour recurrence was reduced in patients who received the boost dose.2 The largest absolute improvement occurred in patients aged 40 years or less. 10-year follow-up showed a favourable result in the boost group in terms of ipsilateral breast recurrence, with no significant interaction by age group.3 As a result, the number of salvage mastectomies was substantially reduced. However, severe fibrosis in the tumour bed area was more common in the boost group than in the no boost group. 10-year overall survival did not differ significantly between groups.
Romestaing and colleagues4 also investigated the effect of a boost dose in a trial including 1024 patients who received a boost of 10 Gy to the tumour bed after 50 Gy delivered with 2·5 Gy per fraction to the whole breast following limited surgery. They found that this approach significantly reduced the risk of early ipsilateral breast tumour recurrence, with no serious deterioration of the cosmetic result.
We assessed whether the initial benefit of a boost dose, resulting in improved local control, is sustained in the very long term in patients with stage I and II breast cancer who underwent breast-conserving treatment and whether this benefit translates into an improvement in survival.
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Study design and patients
We analysed the long-term results from the EORTC phase 3 randomised controlled trial.3 The trial was done at 31 hospitals and medical centres in Australia, Belgium, France, Germany, Israel, Netherlands, Spain, Switzerland, and the UK. The protocol is available online.
Patients with T1–2, N0–1, and M0 breast cancer (stage I and II breast cancer) who had undergone macroscopically complete local excision of the breast tumour and axillary dissection were eligible for the trial. Patients were
Results
Between May 24, 1989, and June 25, 1996, 5569 participants with early stage breast cancer underwent a lumpectomy followed by whole-breast irradiation of 50 Gy. 5318 patients had microscopically complete tumour excision and were randomly assigned—2661 to the boost group and 2657 to the no boost group (figure 1). 251 patients with microscopically incomplete excision were randomly assigned to a boost dose of 10 Gy or 26 Gy—however, these results have been described elsewhere6 and will not be
Discussion
20 years after breast-conserving treatment, about 60% of patients with breast cancer were still alive, but survival did not differ between patients who received or did not receive a boost of 16 Gy after whole-breast irradation. However, a boost dose did reduce the incidence of ipsilateral breast tumour recurrence.
The failure of improved local control to improve breast cancer mortality or overall survival seems contradictory to the findings of the EBCTCG trial.1 However, in our study only about
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