An argument against routine use of radiotherapy for ductal carcinoma in situ

Three prospective randomized trials have shown that postexcisional radiation therapy can reduce the relative risk of local recurrence by about 50% in conservatively treated patients with ductal carcinoma in situ (DCIS). In an era of evidence-based medicine, how then can one possibly take a stand against the routine use of radiation therapy after local excision? Surprisingly, the rationale is straightforward. In some low-risk DCIS patients, the costs may far outweigh the potential benefits. In spite of a relative 50% reduction in the probability of local recurrence, the absolute reduction may only be a few percentage points. In addition, the prospective trials focus on local recurrence as their primary end point because it is, by far, the most common untoward event following conservative treatment. Local recurrence is clearly important, but breast cancer-specific survival is, in fact, an even more important end point, and no trial in patients with DCIS has ever shown a survival benefit with the use of radiation. Moreover, radiation therapy is not without financial and physical cost. So, if there is no difference in breast cancer-specific survival regardless of the treatment and in some subgroups the absolute benefit from radiation therapy is extremely small, it seems reasonable to attempt to develop a system to select patients with DCIS who could be safely treated in the least aggressive way. The University of Southern California/Van Nuys Prognostic Index (USC/VNPI) uses five independent predictors of local recurrence to do exactly that. The combination of tumor size, margin width, nuclear grade, age, and the presence or absence of comedonecrosis can be used to identify subgroups of patients with an extremely low probability of developing a local recurrence after excision alone. When accurate measurements of tumor size cannot be made, margin width can be used as a surrogate parameter for the USC/VNPI. New oncoplastic techniques that allow more extensive excisions can be used to achieve both acceptable cosmesis and widely clear margins, helping to alleviate the need for radiation therapy in many cases.