In the study of cancer, researchers have used different types of cells, different environmental conditions, and different experimental designs. but, all researchers have arrived at the same conclusion. which conclusion is that?

I would say that they came to: our estimate is that about three-quarters of the current annual incidence of breast-cancer in the United States is being caused by earlier ionizing radiation, primarily from medical sources. We will show that the recently growing incidence is not mysterious, and that if we wish to understand why the incidence has been growing, we must look to radiation events in the life of women 15-25-35-45 and more years before breast-cancer diagnosis. Moreover, there is recent evidence about induction of early-onset breast-cancer by radiation.
there, i hope that this helps you. 
have a great day. =)