P-311: Survival of patients with relapsed/refractory multiple myeloma receiving palliative therapy with cyclophosphamide/ prednisone: Results in 346 patients from a single institution over the last 50 years

Introduction: The overall survival (OS) of patients with multiple myeloma (MM) has significantly improved in recent years thanks to the introduction of new drugs. However, MM remains an incurable disease and patients continue to die from refractory myeloma. When the patient has exhausted all available therapeutic options, palliative treatment with cyclophosphamide and prednisone (CP) is common in some centers but there is no real life data on the survival of this population.

Methods: From july 1972 to december 2021, 346 patients (48% men, median age 71 years) received palliative treatment with CP (cyclophosphamide 650 mg/m2 i.v. every 3 or 4 weeks and alternate day prednisone at a dose of 30 mg po) as the last line of treatment. The time point when patients started CP therapy was considered the time zero (T0). From T0, three time periods were defined (1972-1999: N= 108; 2000-2010: N= 95; 2011-2021: N=143) based on the incorpotarion of novel classes of antimyeloma agents.

Results: The median number of prior lines before T0 was 2 (1-4), 2 (1-8) and 3 (1-12) for periods 1, 2 and 3, respectively. In period 1, 81% of patients started CP after 1 or 2 prior lines compared with 54% and 47% of patients in periods 2 and 3, respectively. Thus, in period 1 only 3 patients (2,7%) received 4 prior lines, while in period 2 and 3, 23% and 38% of patients received ≥4 prior lines of therapy. The median time from diagnosis to T0 were significantly longer in period 3 (22, 33 and 43 months, p< 0.0001 for period 1, 2 and 3, respectively). The median OS from T0 in the overall series was 7 months and there was no difference among the three periods of time (7 vs 9 vs 7 months, p=0.722). Patients who received ≤3 prior lines of therapy had a significantly longer OS from T0 than patients who had received more than 3 lines (median 9 vs. 5 months, p=0.005). On the contrary, there was no difference in OS between patients treated only with conventional chemotherapy or those exposed to novel drugs (median 7 vs 7 months, p=NS).

Conclusions: The median OS of patients who start palliative treatment with CP is 7 months. This survival has remained similar over the last 50 years and is not influenced by the period of time or previous exposure to novel drugs. However, the number of prior lines of therapy has a significant impact on OS, being shorter for those patients who start palliative treatment after more than 3 prior lines