My mentor has a new treatment, but the series is single-arm and small. How can I write it up?

Hearing only the first half, I thought it would not work. After hearing the second half, I think it has a good chance. Here is why.

Most of the time, when a mentor hands us a series of patients treated one way and says, "Go run some statistics," the result is not good. The usual problems are that the treatment has not kept up with the field, the protocol has problems, and the number of patients is not clearly large. A quick PubMed search usually shows this.

A single-arm study is the weakest kind of clinical study, because it can never fully answer the reviewer's suspicion that you are simply praising your own product. Maybe your few patients happened to respond well. Who knows whether the treatment would work as well in my hospital?

But you say the treatment is very new and many people are interested. Then you have a good chance. In the early days of a field, people want to hear any information.

You could write it as a clinical feasibility study, emphasizing feasibility and reporting that there were no serious adverse effects. As for outcomes, compare them with other published studies in the Discussion.

Or you could call it a preliminary study or early experience. If the medical community is truly interested, that also works.

A control group is important and powerful. But science has always had another line, without control groups. The discovery of the structure of DNA and Darwin's theory of evolution, for example, did not rely on controlled studies, and the world still accepted them.