Retreatment of Multiple Myeloma with Previously Refractory Drugs

• Retreatment with previously refractory drugs is a viable option for late line relapsed/refractory multiple myeloma.

• Patients with a longer gap between initial line of therapy with index drug and retreatment had superior outcomes with retreatment.

As patients with relapsed/refractory multiple myeloma (RRMM) continue to live longer, they might get exposed to most available drugs and drug classes during the disease course. For such late line RRMM or among patients without access to novel therapies, retreatment with a drug that the disease had previously been refractory to might be one option. In this retrospective study, we describe 315 patients with RRMM at our institution that were retreated with a drug that the disease had been previously refractory to. We found an overall response rate of 56.2%, and a median progression free survival (PFS) of 11 months with retreatment. Patients with a longer time on initial therapy with the index drug (>28.4 months) had a superior PFS with retreatment (median PFS 16.9 months vs 8.1 months, p<0.001). Similarly, patients with a longer time gap between the initial line of therapy with index drug and retreatment with index drug (>46.1 months) had a better PFS with retreatment (28.2 vs 8.9 months, p=0.016). In conclusion, retreatment with a previously refractory drug is a viable therapeutic option for RRMM, with the most significant benefit derived in disease demonstrating sensitivity to initial drug exposure, and among those with a longer gap between initial drug exposure and retreatment.