Characteristics of long term survivors of multiple myeloma after autologous stem cell transplantation: a retrospective analysis from a tertiary care centre in India.

Background: Outcome of newly diagnosed, transplant eligible, multiple myeloma (MM) patients have improved significantly during the past two decades. A small proportion of patients are long term survivors beyond 10 years. We evaluated clinical and laboratory characteristics of these long term survivors. Methods: Four hundred and thirty eight consecutive MM patients underwent autologous stem cell transplantation (ASCT) between 1995 and 2019. Patients median age was 52 years, (range, 20-73) and 291 (66.4%) were males. 35.3% had ISS stage III disease. 96 (21.9%) patients were long term survivors (LTS), defined as those alive 120 months or more. Findings: Compared to others, LTS patients more frequently had ISS stage I (42% vs 28.5%, p < 0.001), serum albumin ≥3.5 g/dl (72% vs 57%, p < 0.005), platelet count ≥150,000/μL (88% vs 71%, p < 0.001), eGFR ≥40 ml/min (85.4% vs 75%, p < 0.01), and bone marrow plasma cells ≤40% (60% vs 49%, p < 0.03). Transplant within 12 months of diagnosis (73% vs 51.5%, p < 0.001) and in first remission (89.6% vs 71.3%, p < 0.001) were more common in LTS. Post-ASCT response was superior: CR (80% vs 65.5%, p < 0.004), CR + VGPR (94.8% vs 82.5%, p < 0.001). At median follow-up of 115 months, median overall survival was 264 months and progression-free survival 158 months. Interpretation: This study identifies a distinct subgroup of MM patients with long-term survival, characterized by favourable baseline features, early and effective treatment, and deep post-transplant responses, with a median progression-free survival exceeding 13 years. Funding: No funding was received for present study.