New radiation therapy technique for breast cancer : should the IOERT boost be a standard technique ?

The standard treatment for early breast cancer comprises wide local excision, sentinel lymph node biopsy or axillary lymph node dissection and whole-breast radiotherapy (WBRT), including boost radiation if indicated, and adjuvant medical treatment. Multiple randomized clinical trials and meta-analyses demonstrated the effectiveness and safety of WBRT, and revealed that local control plays a crucial role in overall survival [1,2]. The European Organisation for Research and Treatment of Cancer (EORTC) boost versus no boost trial demonstrated that the additional dose escalation to the tumor bed, the tumor bed boost, further improved local control rates [3]. The Early Breast Cancer Trialists’ Collaborative Group (EBCTCG [Oxford, UK]) overview suggested that differences in local treatment that substantially affect local recurrence rates would avoid approximately one breast cancer death over the next 15 years for every four local recurrences avoided and should reduce 15-year overall mortality [2]. The local recurrence rate is estimated for 1% per year, and varies according the literature between 4 and 7% after 5 years and up to 10–20% in the long-term follow-up [1,4–6]. The majority of patients who develop local recurrences do so within 2–5 years [1,7]. Patients with local recurrences have an increased risk of distant metastases, and local recurrence seems to be an independent predictor of distant metastasis [7–15]. Patients who develop recurrences in the short term have a worse prognosis than patients who develop recurrences in the long term [1,7]. Based on these data the reduction of local recurrence rates should be one of our treatment goals. Many factors contribute to the reduction of local recurrence rates, such as improved diagnostic tools, modern surgical techniques, the extensive pathologic evaluation of specimen and margins, the increasing use of adjuvant systemic therapies and the extensive use of radiation therapy. Standard radiation therapy comprises 50–55 Gy in daily fractionations for 5–6 weeks. The additional application of an external boost radiation of 10–16 Gy to the tumor bed can reduce the local failure rate by 40% [3,16–19]. With this therapy an excellent local tumor control can be achieved.