Abstract / Summary
Background: Immunoglobulin isotype is recorded at diagnosis in every patient with intact-immunoglobulin multiple myeloma, but is not retained in the ISS, R-ISS, or R2-ISS. Methods: We analyzed 196 consecutive patients with IgA or IgG myeloma who underwent upfront autologous stem cell transplantation at a single center (2009–2023). The primary endpoint was progression-free survival (PFS); overall survival (OS) was the secondary endpoint. Cox models used information available at transplantation, including the induction regimen and transplant year, in the complete-case set (n = 131) and after multiple imputation (n = 196). Results: Median PFS was 14.8 versus 30.5 months and OS 43.2 versus 94.2 months in IgA versus IgG patients (both p < 0.001). IgA isotype was associated with inferior PFS (adjusted HR 1.85, 95% CI 1.13–3.02; imputed HR 1.83, 95% CI 1.22–2.73). For OS, the HR was 1.68 (0.98–2.88) in the complete-case analysis and 1.91 (1.24–2.94) after imputation, so its magnitude is uncertain. Models with maintenance gave 1.87 and 1.82. Progression documentation differed by maintenance status. Cytogenetic data were too incomplete to assess independence from genomic risk. Conclusions: In a bortezomib-era transplant cohort, IgA isotype was associated with inferior PFS; the association with OS was of uncertain magnitude. The finding is hypothesis-generating and requires validation in cohorts with complete cytogenetic characterization.