The importance and evolution of radiation dose in DCIS

Paralleling breast conservation therapy for invasive breast cancers, treatment for ductal carcinoma in situ (DCIS) has followed the treatment paradigm of surgery and postoperative radiotherapy. Randomized studies evaluating the need for radiation therapy following lumpectomy in patients with DCIS from both the NSABP (B-17) and the EORTC (10853) demonstrated a local control benefit that was homogeneous across all treatment groups. In an era of medicine driven by characterization of tumors into molecular subsets and increasingly focused on individualizing treatment, this "one size fits all" mentality has been challenged. With respect to invasive disease, it has become clear that while prospective randomized studies continue to show a reduction in local recurrence with the addition of postoperative radiation therapy, the magnitude of benefit varies among subsets of patients. The variability in the magnitude of benefit from postoperative radiotherapy was additionally demonstrated in a study showing further reduction in recurrence risk with the addition of a boost following whole breast treatment for invasive disease. In DCIS large randomized trials evaluating the additional efficacy of a boost and which subsets of patients would benefit the most, are lacking. While an international trial evaluating the benefit of a boost in patients with DCIS continues to accrue, the question of the risk:benefit ratio with the use of a boost and whom it will best serve remains unanswered.