Determinants of Eligibility and Timing of Autologous Transplantation in Multiple Myeloma: The Role of R-MCI and Diagnostic Plasma Cell Burden

Background: Autologous stem cell transplantation (ASCT) remains a cornerstone in the management of multiple myeloma (MM). However, the optimal timing of ASCT and the factors determining whether patients ultimately undergo transplantation remain unclear in real-world practice. The Revised Myeloma Comorbidity Index (R-MCI) was developed to quantify patient fitness but its influence on transplant eligibility and timing has not been fully characterized. Methods: We conducted a retrospective single-center study including 137 patients with newly diagnosed MM between 2015 and 2025. Clinical parameters recorded at diagnosis included age, sex, performance status, renal and pulmonary function, cytogenetic risk, International Staging System (ISS) stage, and bone marrow plasma cell infiltration. The R-MCI was calculated for all patients [1]. Transplant timing was categorized as early (≤12 months) or delayed (>12 months) after diagnosis. Logistic regression analyses were performed to identify predictors of ASCT eligibility and timing. Results: ASCT was performed in 61 patients (44.5%). Transplanted patients were significantly younger (<65 years: 82.0% vs. 25.0%, p<0.001) and had lower R-MCI scores (median 0 vs. 1, p<0.001) compared with nontransplanted patients, while plasma cell infiltration and ISS stage did not differ. Among transplanted patients, 42.6% underwent early ASCT. In multivariate analysis, R-MCI was the only variable showing a trend toward predicting early transplantation (OR 0.27, 95% CI 0.07–1.06, p=0.06). Conclusions: In real-world MM management, patients quantified by R-MCI appear to play a more prominent role than disease burden in determining both eligibility for and timing of ASCT. Incorporating comorbidity indices alongside ISS may enhance individualized transplant decisionmaking and optimize treatment outcomes.