Chapter 45

The European Organization for Research and Treatment of Cancer (EORTC) Breast Group and the Radiotherapy Group successfully completed several clinical trials that included thousands of patients with the goal of improving outcomes by evaluating different approaches in the locoregional treatment of breast cancer. These trials addressed the need for and feasibility of alternative or more aggressive treatment regimens and new ways to predict therapeutic outcomes. For ductal carcinoma in situ (DCIS), the contribution of radiotherapy in achieving local control was examined. For stage I and II breast cancer, mastectomy was compared with breast-conserving therapy. This was followed by a trial in which 2 different dose levels of irradiation were tested (ie, is an extra boost dose required after whole-breast irradiation?). Reduction of morbidity is the aim of the After Mapping of the Axilla Radiotherapy or Surgery (AMAROS) trial comparing axillary lymph node dissection with axillary irradiation in patients with proven axillary metastases in the sentinel nodes. For locally advanced breast cancer, the contribution of hormonal therapy and chemotherapy was investigated. Finally, the possibility of predicting treatment outcomes and therefore individualizing treatment regimens is explored in ongoing trials incorporating genomic profiles. A selection of the EORTC breast cancer trials is presented in this overview, followed by some of the new studies and suggestions for future research.

### The EORTC 10853 DCIS Trial: Whether or Not to Add Breast Radiotherapy after Local Excision

A randomized trial was conducted to investigate the role of breast radiotherapy after local excision of DCIS. We analyzed the efficacy of radiotherapy with 10 years of follow-up on both the overall risk of local recurrence (LR) and according to clinical, histologic, and treatment factors.

After microscopically complete local excision, women with DCIS were randomly assigned to no further treatment or radiotherapy (50 Gy whole-breast irradiation). One thousand and ten women with mostly (71%) mammographically detected DCIS were included. The median follow-up was 10.5 years.1,2

The 10-year LR-free rate was 74% in the group treated with local excision alone compared with 85% in the women treated by local excision plus radiotherapy (log-rank p < 0.0001; hazard ratio [HR] = 0.53). (Fig. 45-1A) The risk of DCIS and invasive LR was reduced by 48% (p = 0.0011) and 42% (p = 0.0065), respectively (Fig. 45-1B and 45-1C). Both groups had similar low risks of metastases and death. At multivariate analysis, factors significantly associated with an increased LR risk were young age (≤40 years; HR = 1.89), symptomatic detection (HR = 1.55), intermediately or poorly differentiated DCIS (as opposed to well-differentiated DCIS; HR = 1.85 and HR = 1.61, respectively), cribriform or solid growth pattern (as opposed to clinging/micropapillary subtypes; HR = 2.39 and HR = 2.25, respectively), doubtful margins (HR = 1.84), and treatment by local excision alone (HR = 1.82). The effect of radiotherapy was homogeneous across all assessed risk factors (Fig. 45-1D).

###### Figure 45-1

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