Currently, more than 70% of women with ductal carcinoma in situ (DCIS) receive breast-conserving surgery (BCS) but then are at risk of a second cancer diagnosis in the same breast. Radiation therapy (RT) after BCS decreases recurrence in the 10 years after diagnosis by half but does not improve survival. Women with DCIS are also at elevated risk for cancer in the contralateral breast. Radiation after BCS for DCIS limits therapy choice to mastectomy if a woman has a second cancer in the treated breast because radiation can be given only once due to limits of normal tissue tolerance. If radiation was not received initially, a patient may be able to avoid mastectomy after a second ipsilateral breast cancer. For these reasons, the choice of treatment for DCIS is complex. A web-based decision aid would help a patient quantify the tradeoffs between her long-term survival and breast preservation.
