Preferred study designs to support a comparative therapeutic strategy question in oncology: a vignette study

Some therapeutic strategy questions in oncology could be answered with studies using observational data. Target trial emulation is the application of design principles from randomized controlled trials (RCTs) to the analysis of observational data, to reduce design-induced biases. Our objective was to determine which type of study physicians would preferably plan to answer a comparative effectiveness question lacking evidence in oncology.

We launched an online survey among physicians specialized in oncology. We constructed a vignette-based inquiry where vignettes described study scenarios which could be conducted to answer the predefined question. We designed six vignettes described by study design (RCT or observational study with a trial emulation framework), main study characteristics, probability of the study succeeding and anticipated delay before results availability. Participants randomly assessed five pair-wise comparisons of the vignettes and were asked which study they would preferably plan by using a Likert scale ranging from -5 to 5. The main outcome was the evaluation of clinicians' preferences for each pairwise comparison. Mean and median preference scores were calculated.

Two hundred thirteen participants, specialized in many tumor types, assessed at least one comparison with 82% reporting France as their country of affiliation. The interquartile range was -4 to 4 across pairwise comparisons. The median preference score was in disfavor of the monocentric RCT for the five comparisons where it appeared. The median preference score was strongly in favor of the multicentric national emulated trial when compared to the monocentric emulated trial 4 [IQR 2.5-4]. The mean preference score was the highest for the large European observational study 1.14 (SD 3.33), while the mean preference score was the lowest for the monocentric RCT -1.86 (SD 2.93).

No study design was strongly preferred, but the monocentric RCT was the least favored study in pair-wise comparisons. The planification of the new research is a compromise between scientific soundness, feasibility, cost, and time before obtaining results. We need to have the right answers to the right questions at the right time.