Reference materials for RCT study design where only placebo patients switch to treatment after 10 weeks

Question

I am looking at a study design where the study randomly assigns patients to two groups, 1) Treatment arm or 2) Placebo.

After 10 weeks, patients in the Placebo group switch to receiving treatment however patients in the treatment arm remain in the treatment arm even after 10 weeks. Study stops after 20 weeks.

Please provide me some reference materials for studies that have used this type of design in the past. Thanks. This looks like a half-crossover design where Placebo patients switch to treatment but treatment patients remain in treatment.

Answer 1

I think what you are asking for is the terminology. There are hundreds of references ranging from primary publications from studies that did this, to logistical or statistical considerations for those types of studies.

The correct name for this design depends on a few other factors. In general, you can call it a crossover design (even though only one treatment arm crosses over). You can also call this a non-controlled extension if the primary endpoint is assessed at 10 weeks but there are other safety or secondary efficacy outcomes that you will collect. Another term is open label extension if patients actually know the arm they're on. This is for designs where the desire to receive the experimental drug is so overwhelming, the only way to mitigate participant bias is to promise they will eventually receive the active drug.