In our latest publication, we used Swedish register data to investigate how the timing of disease progression affects survival in patients with mantle cell lymphoma (MCL). MCL is an aggressive form of lymphoma characterized by frequent relapses, making it crucial to understand the long-term impact of disease progression on patient outcomes. The current study includes data on 1,186 adult MCL patients diagnosed between 2006 and 2018, providing valuable insights into real-world survival patterns across different treatment regimens.

Three Questions to Sara

What was the most interesting part of this project for you?

What I found particularly important in this project was the opportunity to look at progression timing in a more nuanced way than the traditional 24-month cut-off allows. By using an illness–death model, we were able to analyse progression as part of a continuous disease trajectory rather than forcing it into a single threshold. This approach meant that no data were discarded, and all patients could be compared on the same underlying time scale, regardless of when progression occurred. It provided a clearer picture of how progression timing relates to long-term outcomes and allowed us to revisit an established clinical concept, POD24, with a more informative analytical framework.

You used an illness-death model in this study. Can you explain why this approach was particularly valuable?

The illness–death model was valuable because it represents the disease course using three transitions: from diagnosis to progression, from diagnosis to death without prior progression, and from progression to death. This structure mirrors the clinical pathways in MCL and allows us to analyse all of them simultaneously. By incorporating time to progression directly, we could estimate how the timing of progression influences subsequent survival without relying on a fixed cut-off. Traditional methods like landmark analysis require choosing an arbitrary time point and include only patients who survive to that point, which can introduce bias. The multistate approach keeps all patients in the analysis and provides a clearer picture of how progression timing shapes long-term outcomes.

What is the key takeaway from this publication?

The key takeaway is that progression timing has a continuous and clinically meaningful effect on survival in MCL also beyond the commonly used 24-month cut-off. By modelling the disease using an illness–death framework, we could quantify how progression timing translates into poorer long-term outcomes, independent of arbitrary thresholds or survival conditioning. These findings suggest that a more nuanced view of progression timing may improve both prognostication and study design, and highlight the importance of considering the entire disease trajectory rather than relying solely on fixed cut-off points.

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