LAUSR

Dear Editor, Although the restricted mean survival time (RMST) is considered a new methodological tool for interpreting survival curves, its development dates back to more than 15 years ago. In comparison with the median, the RMST has a specific advantage because it examines the entire survival curve (as the hazard ratio) and expresses the survival outcomes using time as a unit of measurement (as medians). More importantly, the RMST captures the presence of a long-term survival plateau, which of course reflects a better prognosis. Most previous experience in the application of RMST is focused upon oncology [1], but other fields are being investigated as well [2]. An original method of calculation, drawn from the field of pharmacokinetics, has markedly simplified the otherwise complex estimation of RMST [3, 4]. In the present analysis, we assessed the RMST from the progression-free survival curve of the patients enrolled in the phase-2 one-arm JULIET trial [5]. Our objective was simply to compare the RMST with the median reported by the JULIET investigators and to determine the ratio between these two parameters The patient group treated with tisagenlecleucel consisted of 48 patients. Their inclusion criteria were diffuse large B-cell lymphoma, at least two previous lines of treatment, including rituximab and an anthracycline. Autologous stem cell transplantation had been performed in 49% of these patients. According to our analysis, the value of RMST in the progression-free survival curve (Fig. 1) was 7.74 months (“milestone” set at 18 months of follow-up). The