Estimating the magnitude of clinical benefit of local therapy in patients with DCIS.

DCIS represents a heterogeneous disease with a wide range of outcomes according to biology. Without treatment, it is estimated that only 20-30% of DCIS will progress to invasive cancer. Long-term outcomes following treatment are at least as favorable as those for some other early stage cancer types such as prostate cancer, for which active surveillance is routinely offered as a standard of care option. However, active surveillance has not yet been tested in relation to DCIS. Worldwide, there are three international trials (LORIS, COMET, LORD) which are evaluating whether DCIS with favorable biologic features may be managed with close monitoring, with treatment only undertaken upon disease progression. These trials will determine whether there may be some women with low-risk DCIS who do not substantially benefit from treatment and who could thus be safely managed with close surveillance. If active monitoring for DCIS is deemed to be safe and feasible, additional work must be done to optimally implement this approach, involving effective communication between patients and their physicians about the risks and benefits of treatment versus surveillance. Importantly, these treatment decisions must take into account patient factors such as risk tolerance, age, and competing causes of mortality. Tailoring treatment to biology for early screen-detected cancers such as DCIS is an important goal of ongoing research. An improved understanding of the biology and clinical implications of this heterogeneous disease will improve the overall health and quality of life for hundreds of thousands of future women who will be diagnosed with DCIS.