Declining Rates of Adverse Events and Dose Modifications with Lenalidomide in Combination with Dexamethasone
Authors: Ishak Jack , Dimopoulos Meletios A , Weber Donna , Knight Robert D. , Shearer Arran , Caro J. Jaime 
Published: October 2019

Abstract
INTRODUCTION: Significantly improved response, time to progression and overall survival with lenalidomide plus high dose dexamethasone (Len+Dex) vs Dex alone was demonstrated in two pivotal trials (MM-009/010) (Weber et. al., NEJM2007, 357:21 and Dimopoulos et. al., NEJM2007, 357:21). Grade 3 or 4 adverse events (AEs) were reported in 83% of patients receiving Len+Dex and 70% with Dex alone. The risk of AEs was not constant over the course of treatment, however. AE rates in the two groups over time are reported here, along with the percentage of dose modifications (interruptions or reductions) of lenalidomide in response to AEs.
METHODS: Data on patients from the MM-009/010 trials were pooled for these analyses. Monthly hazard rates of grade 3 or 4 neutropenia, thrombocytopenia (TCP) and deep-vein thrombosis (DVT) were calculated as the ratio of events observed to person-time accrued each month. Patients alive at the start of a month were included in that month’s calculation. Patients alive and followed through the month contributed a full month to the denominator; patients whose follow-up ends during the month only contributed the fraction of time followed. Rates were calculated at three-month intervals. Similarly, treatment interruptions and dose modifications were quantified in each cycle (28 days) by counting person-days without medication (i.e., interrupted) on each dose of Len.
RESULTS: Of the 353 patients randomized to Len+Dex, 35% experienced neutropenia, 13% TCP and 8% DVT. With Dex alone (N=351), the corresponding percentages were 5%, 7%, and 4%. The hazard rates were highest during the first three months of treatment, and declined thereafter. For example, with Len+Dex, the rate of grade 3 neutropenia was 38 per 1000 person-months, but dropped to 21 per 1000 person-months during months 10–12. The corresponding rates with Dex alone were 4 and 0 per 1000 person-months. The reduction in rates was more pronounced for grade 3 TCP and DVT: from 25 per person-months during months 1–3 to 3 per 1000 person-months during months 10–12 for TCP with Len+Dex, and from 15 to 0 per 1000 person-months for Dex alone. Grade 4 AEs occurred much less frequently but followed a similar pattern. Treatment interruptions were highest during the in first 4 cycles, with patients off treatment between 5 and 8% of follow-up days in this period, compared to 2 to 5% in the subsequent period. Similarly, dose reductions occurred more frequently during the initial cycles and decreased subsequently.
CONCLUSIONS: Exploring AE rates over time revealed that these events were most likely to occur in the initial cycles of treatment. Hazard rates declined thereafter, possibly due, in part, to observed dose modifications. Similarly, patients more susceptible to AEs may have discontinued from the study earlier. Further analyses linking AEs to dose modifications are underway.
Figure Figure Month AE Group 1–3 4–6 7–9 10–12 13–15 16–18 19–21 Neutropenia Len-Dex (Grade 3) 0.038 0.035 0.035 0.021 0.025 0.009 0.011 Dex (Grade 3) 0.004 0.002 0.003 0.000 0.002 0.000 0.000 Len-Dex (Grade 4) 0.008 0.006 0.001 0.000 0.002 0.000 0.000 Dex (Grade 4) 0.001 0.000 0.000 0.000 0.000 0.000 0.000 Thrombocytopenia Len-Dex (Grade 3) 0.025 0.007 0.003 0.006 0.002 0.000 0.000 Dex (Grade 3) 0.015 0.002 0.000 0.000 0.000 0.000 0.000 Len-Dex (Grade 4) 0.001 0.002 0.000 0.000 0.000 0.000 0.005 Dex (Grade 4) 0.002 0.000 0.000 0.000 0.000 0.000 0.000 DVT Len-Dex (Grade 3) 0.013 0.011 0.001 0.004 0.000 0.003 0.000 Dex (Grade 3) 0.005 0.006 0.001 0.000 0.000 0.000 0.000 Len-Dex (Grade 4) 0.001 0.000 0.000 0.000 0.000 0.000 0.000 Dex (Grade 4) 0.001 0.000 0.000 0.000 0.000 0.000 0.000