Adjuvant Radiotherapy for Breast Cancer: More than Meets the Eye

Radiotherapy has been used in the adjuvant treatment of breast cancer patients for several decades. Level 1 evidence has demonstrated improvements in locoregional control, breast cancer-specific survival, and overall survival in the setting of whole-breast radiotherapy after breast-conserving surgery, regional nodal irradiation, and postmastectomy radiotherapy [1, 2, 3]. However, times are changing. Radiotherapy is no longer a one-size-fits-all approach [4]. Numerous clinical trials have led to a significant increase in the level of complexity in the management of breast cancer patients [5, 6]. Biological risk stratification, systemic therapy, and surgical radicality have changed dramatically, as have the available options regarding individualization of radiotherapy in terms of fractionation and target volume.

In this special issue of Breast Care, the spotlight is on several important aspects of radiotherapy in this modern era.

The indication for adjuvant radiotherapy is mainly based on clinicopathologic factors such as patient age, tumor size, and lymph node involvement as well as hormone and HER2 receptor status. However, gene expression assays are commercially available and they are increasingly being used to determine the indication for adjuvant chemotherapy. Thus, patients frequently present for discussion of adjuvant radiotherapy with results from these assays. One of the articles accompanying this editorial is a review of the literature regarding the question of whether these readily available results may be used to determine the need for adjuvant radiotherapy [7].

Accelerated partial breast irradiation (APBI) is an exciting concept for patients with low-risk early-stage breast cancer. Targeting only the tumor bed and a clinical safety margin around it instead of the whole breast allows for the use of higher doses per fraction, a significant reduction of the overall treatment time, and, potentially, a decrease in the risk of side effects from adjuvant radiotherapy. However, randomized clinical trials studying APBI have used various techniques, fractionations, and study designs which demand a thorough examination. Forster et al. [8] summarize the current evidence on this topic, including recently published data, and present novel developments in terms of ongoing trials and technical improvements such as magnetic resonance-guided radiotherapy.

Regional nodal irradiation has seen a renaissance for early-stage breast cancer after publication of several trials demonstrating improved oncologic outcome with regional nodal irradiation including the internal mammary lymph nodes [9, 10, 11]. However, the techniques applied for radiotherapy delivery and the treated target volumes in these trials were outdated [12, 13]. Duma [14] summarizes the available clinical evidence as well as new and provocative data with implications for target volume definition.

Last but not least, Matuschek et al. [15] present the concept of neoadjuvant radiotherapy for breast cancer. Neoadjuvant radio(chemo)therapy is a concept well known to radiation oncologists and it is considered standard of care for many oncological diseases such as esophageal cancer, rectal cancer, and soft-tissue sarcoma. There are some historical trials using neoadjuvant radiotherapy in breast cancer, but it is not routinely used nowadays [16]. The authors provide an overview of the literature as a rationale for the planned phase 3 NeoRad trial.

In summary, these are exciting times for radiation oncologists. However, detailed knowledge of the available evidence is crucial for interdisciplinary discussions and for providing our patients with optimal guidance during the decision-making process.

Disclosure Statement

D. Krug has received personal fees from Merck Sharp & Dohme outside of the submitted work.

Funding Sources

No funding was provided for this work.