Because it's generally unethical to not give someone a treatment known already to be safe and effective. Studies of new vaccines where there is not an existing vaccine _do_ use placebo controls. Heck, my son got placebo during moderna's pediatric covid vaccine trial (to our frustration. grin.)

Subsequent trials generally compare against the best known current treatment as the control instead.

This study has no such concerns. It's ethical to include images of non-cancerous breast tissue. The things are not comparable.

> Its interesting to see this valid argument raised against this use of AI to identify breast cancer. The lack of control groups is one of the more common concerns raised related to vaccines as well, the argument lands like a lead balloon there.

Not just vaccines, in each study on the effectiveness of a drug, especially when dealing with potentially life-threatening conditions, the same question is posed. From[0]:

. . . ethical guidance permit the use of placebo controls in randomized trials when scientifically indicated in four cases: (1) when there is no proven effective treatment for the condition under study; (2) when withholding treatment poses negligible risks to participants; (3) when there are compelling methodological reasons for using placebo, and withholding treatment does not pose a risk of serious harm to participants; and, more controversially, (4) when there are compelling methodological reasons for using placebo, and the research is intended to develop interventions that can be implemented in the population from which trial participants are drawn, and the trial does not require participants to forgo treatment they would otherwise receive.

[0] https://pmc.ncbi.nlm.nih.gov/articles/PMC3844122/

Vaccine studies use a different experimental design known as “longitudinal,” meaning they follow people over time. This study did not do that. It’s still a valid design, just limited in what it tells us.