The goal of this work was to provide an overview of common patterns in the sequential treatment of RA starting with the first b/tsDMARD. Most patients began with a TNFi therapy, although we observed a recent shift towards JAKi therapies over the decade-long study period (2012–2021). While the choice of first-line therapy was near-deterministic as a TNFi, there was substantial variation in subsequent treatment selections, leading to many distinct treatment patterns. We identified the most common sequences of up to four therapy changes and found that therapy cycling (restarting a therapy from a previously used therapy class) was a frequent pattern. We also found that the average duration of the first three therapies decreased over the study period. We did not provide information on disease activity or adverse events for the observed patterns, and the most common patterns are not necessarily the recommended best practices. Nevertheless, identifying frequent patterns in current treatment of RA is an important step toward developing and evaluating new treatment strategies.
Real-world observational data provides a unique view of patients’ response to treatments and could be used to identify the effectiveness of different sequences of therapies. However, conducting such a study requires a quantitative understanding of current practice. For example, which patterns do we see often enough to evaluate retrospectively? First, in the current set of analyses, we found that sequences that do not start with an initial TNFi therapy were rare. Evaluating such patterns retrospectively would require very large data sets of patients to arrive at statistically sound results. Second, we found large practice variation in longer therapy sequences which may be exploited to identify successful strategies that deviate from current guidelines. By providing an overview of current practice, this study takes a first step in advancing RA treatment. The next steps include identifying strategies for sequential treatment with sufficient support in observed data, estimating the historical propensity for following these strategies, and adjusting for selection bias to compare their value over current guidelines.
Patients with difficult-to-treat RA (22) often undergo multiple therapies in search of a working medication. Acquiring a better knowledge of successful therapy sequences would be particularly beneficial for this group of patients. Recent work has indicated that many non-responders eventually benefit from a fourth line therapy (13), but there is little evidence of which of these “extended” sequences may work better than others. We suspect that these patients account for many of the observed patterns in this work. However, most of these patterns are not shown in our sequence visualizations in Fig. 3 because they are too rare. To draw conclusions about patients with difficult-to-treat RA and evaluate different treatment strategies for these patients, one would need to make additional assumptions and group similar sequences together. For example, patients who have tried the same set of therapies, with similar responses, may be comparable even if the order in which they tried the therapies differ.
A finding of our work is that the use of JAKi as first-line therapy increased in recent years. This trend can partially be explained by the increasing availability of these drugs. Another finding is that the duration of the three initial therapies decreased in the last decade. A possible explanation for this result is that the number of available treatment options greatly increased during this time period. An alternative explanation could be that within-class cycling, i.e., switching between drugs with the same mechanism of action, was more common in the past. However, when studying the number of within-class switches for patients who started with a TNFi combination therapy, we found no clear support for that theory. Finally, the number of outliers, e.g., patients who stayed on their first therapy for several years before they suddenly changed therapy, is naturally higher in the first interval and skews those distributions.
The trend of decreasing therapy duration was observed also in recent work by Mease et al. (23), although they used data of patients enrolled in the CorEvitas RA registry between 2004 and 2015 and studied a smaller set of therapies. There exist some studies that have tried to describe sequential therapies using Sankey diagrams (12, 13). Our sequence visualizations contain more information in the sense that they show entire therapy trajectories and not only transitions between consecutive therapies. Still, it is worth noting that Zhao et al. (13) identified the transition between TNFi and rituximab as the second most common transition between the first two lines of treatment. In contrast, there are no sequences starting in this way in Fig. 3. This may reflect differences in typical care by country (UK versus US).
The primary strengths of this study are the focus on sequential therapies and the use of a large real-world dataset from the CorEvitas RA registry. There are also limitations, for example that we did not place any restrictions on the regularity of the registry visits. As well, the median duration of follow-up in the CorEvitas RA registry is 3.4 years, which limits the amount of data for patients treated with many sequential therapies. We expect the variation in patterns to be even greater with increased duration of follow-up. Further, biologic data was not included in the current analyses, limiting the ability to understand the pathobiology of difficult-to-treat RA. The fact that we did not distinguish between individual csDMARDs may also be considered a limitation. We chose this approach to reduce the number of therapy permutations and reinforce patterns of b/tsDMARD treatment strategies—the focus of our work. For the same reason, we did not consider switching between drugs from the same class as a change of therapy, preventing such transitions from appearing in our patterns. Finally, we included only subsequences starting with the first b/tsDMARD prescription in our analysis. Most patients were treated with an initial csDMARD therapy before starting their first b/tsDMARD and not distinguishing patients based on this information may be considered a limitation. Understanding the effects of early exploration on the therapy decisions that follow is an important challenge for future work.