These are peer-reviewed supplementary materials for the article 'Adjusting for treatment crossover in the MAVORIC trial: survival in advanced mycosis fungoides and Sezary syndrome' published in the Journal of Comparative Effectiveness Research.

A. List of variables available for analysis

B. Methodology to fit survival curves

C. IPCW extra detail: Weights

Figure 1: Histogram of weights from the IPCW analysis
Figure 2: Plot of weights over time from the IPCW analysis

D. ITT population

RPSFTM
IPCW
TSE

Background: Relative overall survival (OS) estimates reported in the MAVORIC trial are potentially confounded by a high proportion of patients randomized to vorinostat switching to mogamulizumab; furthermore, vorinostat is not used in clinical practice in the UK. Methods: Three methods were considered for crossover adjustment. Survival post-crossover adjustment was compared with data from the Hospital Episode Statistics (HES) to contextualize estimates. Results: Following adjustment, the OS hazard ratio for mogamulizumab versus vorinostat was 0.42 (95% CI: 0.18, 0.98) using the method considered most appropriate based on an assessment of assumptions and comparison with HES. Conclusions: OS of mogamulizumab relative to vorinostat may be underestimated in MAVORIC due to the presence of crossover. The HES database was used to validate this adjustment.