Impact of pathological characteristics on local relapse after breast-conserving therapy: a subgroup analysis of the EORTC boost versus no boost trial.

PURPOSE: To investigate the long-term impact of pathologic characteristics and an extra boost dose of 16 Gy on local relapse, for stage I and II invasive breast cancer patients treated with breast conserving therapy (BCT). PATIENTS AND METHODS: In the European Organisation for Research and Treatment of Cancer boost versus no boost trial, after whole breast irradiation, patients with microscopically complete excision of invasive tumor, were randomly assigned to receive or not an extra boost dose of 16 Gy. For a subset of 1,616 patients central pathology review was performed. RESULTS: The 10-year cumulative risk of local breast cancer relapse as a first event was not significantly influenced if the margin was scored negative, close or positive for invasive tumor or ductal carcinoma in situ according to central pathology review (log-rank P = .45 and P = .57, respectively). In multivariate analysis, high-grade invasive ductal carcinoma was associated with an increased risk of local relapse (P = .026; hazard ratio [HR], 1.67), as was age younger than 50 years (P < .0001; HR, 2.38). The boost dose of 16 Gy significantly reduced the local relapse rate (P = .0006; HR, 0.47). For patients younger than 50 years old and in patients with high grade invasive ductal carcinoma, the boost dose reduced the local relapse from 19.4% to 11.4% (P = .0046; HR, 0.51) and from 18.9% to 8.6% (P = .01; HR, 0.42), respectively. CONCLUSION: Young age and high-grade invasive ductal cancer were the most important risk factors for local relapse, while margin status had no significant influence. A boost dose of 16 Gy significantly reduced the negative effects of both young age and high-grade invasive cancer.

Impact of the boost dose of 10 Gy versus 26 Gy in patients with early stage breast cancer after a microscopically incomplete lumpectomy: 10-year results of the randomised EORTC boost trial.

PURPOSE: To assess the impact of the boost dose in patients with involved surgical margins. PATIENTS AND METHODS: In the EORTC "boost versus no boost" trial, 251 patients with a microscopically incomplete tumour excision were randomised to receive either a low boost dose of 10 Gy (126 patients) or a high boost dose of 26 Gy (125 patients). Overall survival and the cumulative incidence of local recurrence as first event were compared by Logrank and Gray test, respectively (2-sided alpha=0.05), with a median follow-up of 11.3 years. The planned sample size was 660 patients, but only 251 were recruited. RESULTS: The median age at randomisation was 54 years. Thirty-seven patient initially relapsed locally. At 10 years, the cumulative incidence of local recurrence was 17.5% (95% CI: 10.4-24.6%) versus 10.8% (95% CI: 5.2-16.4%) for the low and high boost dose groups, respectively (HR=0.83, 95% CI: 0.43-1.57, Gray p>0.1). Overall, 64 patients have died (25.5%), 47 of them of breast cancer, without a difference in duration of survival between the two groups (HR=0.97, 95% CI=0.59-1.5, p>0.1). Severe fibrosis was palpated in the breast in 1% versus 5% and in the boost area in 3% versus 13% in the low and high boost dose groups, respectively. CONCLUSIONS: There was no statistically significant difference in local control or survival between the high boost dose of 26 Gy and the low boost dose of 10 Gy in patients with microscopically incomplete excision of early breast cancer. Fibrosis, however, was noted significantly more frequently in cases treated with the high boost dose.