There is none. No women with DCIS have been included in a randomized controlled trial.
Cosmetic outcomes are unclear; Second operations to fix the cosmetic outcome may be needed, but reasonable estimates for harm and complications do not exist as bilateral mastectomy has not been systematically studied in DCIS. A paper in Annals of Surgery found that out of 600 women at one institution, 42% of 209 women undergoing bilateral mastectomy had complications versus 29% of 391 women undergoing unilateral mastectomy (42-29% = 13%, added harm). Serious complications of bilateral mastectomy occurred in 14%; 4% with unilateral(14-4% = 10%, added harm).
There is no trade-off between benefit and harm. Since there is no benefit, only harm is possible. Informed medical-decision-making requires a trade-off between added benefit and added harm. This is not the case for DCIS and bilateral mastectomy.