Lenalidomide Maintenance Does Not Negatively Impact Overall and Progression Free Survival Using Lenalidomide-Based Regimens for Multiple Myeloma in First Relapse

BACKGROUND

Outcomes in multiple myeloma have improved dramatically over the last decade however, optimal sequencing of therapy remains unknown. Specifically, in an era where post-transplant lenalidomide (L) maintenance is now as established standard of care, questions remain around the utility of full dose L-based regimens in second line therapy. In this series, we sought to evaluate the impact of different regimens used at first relapse in patients who received autologous stem cell transplant (ASCT) in the frontline setting treated with and without lenalidomide maintenance (LM). We focused on the impact of L-based therapies in patients relapsing on LM.

METHODS

Using our prospectively maintained institutional MM database we retrospectively analyzed patients treated at the Cross Cancer Institute from January, 2005 to January, 2016 to ensure 2 years of follow-up for surviving patients. 4 categories were identified based on 2 variables: receipt of LM following 1^st line therapy (yes or no) and receipt of L-based 2^nd line therapy (yes or no). The primary endpoint was 2nd PFS defined as time of initiation of second line therapy to relapse, death or last follow-up. OS was defined as time of initiation of first line induction therapy to death or last follow-up. Second OS was defined as time of initiation of second line therapy to death or last follow-up. Survival statistics were determined using the Kaplan-Meier method with SPSS software. A p - value of <0.05 was considered significant.

RESULTS

213 patients received standard bortezomib-based induction and ASCT of which 132 (62%) received LM. Median follow up for the LM patients was 48 months compared to 74.6 months in non-LM patients. 103 patients (48%) required treatment with second line therapy. Forty-four percent patients were treated with LM while 56% were not. Sixty-nine percent received L-based therapy at relapse, 21% received PI-based therapy and 8% were treated with a PI-IMID combination (table 1).

Focusing on the cohort of relapsed patients who received LM (n=44), the median 2^nd PFS was 9.3 months in those that received L-based second line therapy vs 4.1 months in those that did not (p = 0.28, figure 1b]. In patients who did not receive LM (n = 55) the median 2^nd PFS was 14.0 months in those who received L-based second line therapy vs 6.9 months in those who did not (p = 0.19, figure 1a. Examining all patients who received L-based therapy at relapse there was no difference in 2^nd PFS based on whether LM was given (p = 0.42).

The median 2^nd OS was not statistically significant between the groups (p = 0.39, figure 1b. Patients on LM had a median 2^nd OS of 34 months with L-based therapy at relapse compared to 39.2 months without. The median 2^nd OS in non-LM patients was 34.5 months in those receiving L-based therapy at first relapse and 23.4 months in those that did not (p=0.10).

There was no statistically significant differences in median OS between the 4 groups (p = 0.83). For patients who received LM the median OS was not reached in those receiving L-based therapies at relapse and was 78.1 months in patients who did not. In patients who did not receive LM the median OS was 78.0 months in those receiving L-based therapies at relapse and 69.3 months in those who did not.

CONCLUSION

Our data suggests that receiving LM does not negatively impact survival outcomes after receiving full dose L-based therapy at relapse. Both median 2^nd PFS and 2^nd OS were similar with L-based therapies regardless of prior LM. While the 2^nd PFS at relapse does fall short of recently published trials in relapsed MM there are some notable confounders here. Firstly, this real-world data includes frailer patients with potentially greater co-morbidities possibly influencing choice and duration of therapy as well as reflect more aggressive disease biology. Secondly, given the relatively short median follow-up of the relapsed LM patients to date, the cohort may be enriched with "early" relapsers (< 2-years) also potentially indicative of biologically more aggressive disease. As such, this may underestimate the true impact of L-based therapies in patients relapsing on LM. Larger series with longer follow-up are necessary to formally examine whether multi-agent L-based regimens confer additional benefit over L-Dexamethasone or non-L based regimens. Real world registries will be useful as prospective trials are unlikely to be done.

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