Supplementary Material for: Effectiveness of Long-Term Treatment of Multiple Myeloma in Regular Care: Comparison of a Longitudinal and a Cross-Sectional Analysis Approach

<b><i>Introduction:</i></b> New drugs for multiple myeloma have considerably increased the options for consecutive treatment lines in regular care. Official treatment guidelines still discuss several regimens per line, and therefore, current practice is of topical interest. Large cross-sectional studies revealed a greater than linear loss of patients reaching consecutive treatment lines of ever decreasing effectiveness. <b><i>Methods:</i></b> In a longitudinal approach, we analyzed data of all 145 multiple myeloma patients treated in our outpatient clinic in Germany between January 1, 2012, and December 31, 2019, using a time-to-event analysis with death as competitive risk. <b><i>Results:</i></b> The estimated incidences of reaching the 2nd, 3rd, 4th, and 5th lines of therapy were 88, 66, 44, and 30%, respectively. Median times to subsequent treatment lines were 34, 18, 14, 13, and 15 months, respectively. <b><i>Discussion:</i></b> Percentages of patients reaching later therapy lines were considerably greater than predicted by cross-sectional studies and median times after the 1st line did not suggest a further decrease in effectiveness, while use of new drug regimens was similar to that reported in cross-sectional studies. <b><i>Conclusion:</i></b> Effectiveness of later therapy lines appears to be underestimated by cross-sectional analyses, and the conveyed focus on 1st-line treatment for multiple myeloma needs to be scrutinized.