Low pectoralis muscle index is associated with inferior survival in standard-risk newly diagnosed multiple myeloma

초록

Background: The severity and prognostic significance of sarcopenia in hematologic malignancies, particularly newly diagnosed multiple myeloma (NDMM), remain insufficiently characterized. Objectives: We aimed to compare the pectoralis muscle index (PMI) distribution in NDMM with that in an unmatched diffuse large B-cell lymphoma (DLBCL) reference cohort and to assess the prognostic value of PMI in NDMM. Design: A retrospective cohort study with an independent reference cohort. Methods: The study included 179 patients with NDMM. PMI was measured at the T4 level using the non-contrast CT component of baseline PET-CT. PMI values were compared with those from an independent cohort of 305 patients with DLBCL. Within the NDMM cohort, patients were stratified into low and high PMI groups using study-derived sex-specific cutoffs. Associations between PMI and clinical outcomes, including overall survival (OS) and time to next treatment (TTNT), were analyzed with subgroup analyses according to Revised International Staging System (R-ISS). Results: Median PMI was significantly lower in the NDMM cohort than in the DLBCL reference cohort for both males (4.19 vs. 5.58 cm2/m2, p < 0.001) and females (3.25 vs. 4.14 cm2/m2, p < 0.001). In multivariable analysis adjusting for age, sex, body mass index, and inflammatory and nutritional markers, NDMM remained independently associated with lower PMI (β = −0.88). Within the NDMM cohort, low PMI was independently associated with inferior OS (adjusted HR, 2.79; 95% CI, 1.42-5.47; p = 0.003; 3-year OS, 48% vs. 78%). Patients with low PMI also had shorter TTNT (3-year TTNT, 14% vs. 45%). These associations appeared more evident among patients with R-ISS stage I-II disease, whereas no significant differences were observed in those with R-ISS stage III disease. Conclusion: PMI may serve as a practical imaging-based measure of sarcopenia with potential prognostic relevance in NDMM, particularly among patients with R-ISS stage I-II disease. © The Author(s) 2026. This article is distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 License (https://creativecommons.org/licenses/by-nc/4.0/) which permits non-commercial use, reproduction and distribution of the work without further permission provided the original work is attributed as specified on the SAGE and Open Access pages (https://us.sagepub.com/en-us/nam/open-access-at-sage).

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