The diagnosis of ductal carcinoma in situ (DCIS) has been controversial, in large part because few tumors go on to become dangerous. On the other hand, when DCIS does become invasive or recurs, it can be deadly.
Even though the 15-year survival rate after treatment for DCIS with tumor excision is excellent (95%), whether radiotherapy can improve that rate isn't clear. Patients with DCIS who were part of the European Organisation for Research and Treatment of Cancer (EORTC) 10853 study were randomly assigned to receive either adjuvant radiotherapy after local excision of the tumor or local excision only. For a median of 16 years the researchers followed 503 women who received excision only and 507 who were treated with excision and radiotherapy.
A total of 234 (23%) women experienced a local recurrence: 149 (30%) in the excision-only group and 85 (17%) in the radiotherapy group. In other words, the addition of radiotherapy almost halved the risk of recurrence overall. In both groups, recurrence risk was highest in the first five years after the initial DCIS diagnosis (4% per year in the excision-only group and 2% per year in the radiotherapy group). Recurrence-free rates at 15 years were 69% in the excision-only group and 82% in the radiotherapy group. The authors conducted additional analyses in an attempt to identify a subgroup with limited benefit from radiotherapy, but they were unable to do so.
Overall, the rates of death related to breast cancer were nearly identical in the two groups: 22 in the excision-only group and 24 in the radiotherapy group. Similarly, breast cancer-specific survival and overall survival were comparable across the two groups. However, the risk of death (from any cause) after invasive local recurrence was five times greater than the risk without local recurrence, and the risk of breast cancer-specific death after invasive local recurrence was 17 times as great. The authors conclude that despite the lack of survival benefit seen in their study, radiotherapy nevertheless makes sense; because patients with invasive local recurrence had significantly worse survival, they argue, "invasive [local recurrence] should be prevented."
Donker M, et al. J Clin Oncol 2013;31(32):4054-9.