(P 385) PROGNOSTIC IMPACT OF PERIPHERAL BLOOD CELL RATIO VALUES IN PATIENTS WITH ADVANCED LEIOMYOSARCOMA: A REFERENCE CENTER EXPERIENCE.

Objective: Peripheral blood cell ratio (PBCR) values, such as the neutrophil-to-lymphocyte ratio (NLR), the monocyte-to-lymphocyte ratio (MLR), and the platelet-to-lymphocyte ratio (PLR), have been associated with prognosis in many solid malignancies. However, their role in metastatic leiomyosarcoma (LMS) has not yet been established.

The aim of this study is to evaluate the association between NLR, MLR, and PLR and prognosis in patients with metastatic LMS.

Methods: Retrospective study of a consecutive cohort of patients with metastatic LMS treated at a reference sarcoma center in Spain between 2009 and 2024.

Clinical, treatment, and laboratory data were collected to calculate PBCR prior to first-, second, and third-line systemic therapies (NLR1/MLR1/PLR1 before first-line; NLR2/MLR2/PLR2 before second-line; and NLR3/MLR3/PLR3 before third-line).

We evaluated the relationship between PBCR and survival outcomes (overall survival -OS-; progression free survival -PFS-) using Spearman’s correlation. ROC curves identified optimal cut-off values, and its prognostic significance was analyzed through Kaplan–Meier curves and Cox regression models.

Results: A weak negative correlation was observed between NLR and survival, particularly between OS and NLR1 (ρ = -0.293; p = 0.003). For OS, the optimal cut-offs were 2.249 for NLR1 and 0.33 for MLR1 and for PFS were 2.249 for NLR1, 2.439 for NLR2, and 1.91 for NLR3.

Using these cut-offs, a higher NLR1 was associated with worse OS (median: 14.4 vs. 46 months -m-; HR: 2.7; p < 0.001) and PFS1 (median: 5.6 vs. 11.9m; HR: 1.99; p = 0.004). Similarly, a higher NLR2 was associated with shorter PFS to second-line treatment (median: 4.9 vs. 11.3m; HR: 1.79; p = 0.05), while a higher NLR3 showed a trend toward worse PFS to third-line treatment (median: 7.4 vs. 14.5m; HR: 2.66; p = 0.055).

MLR1 >0.33 showed a non-significant trend toward worse OS (median: 18.8 vs. 37.3m; p = 0.10).

No association was found between PLR values and survival outcomes.

Conclusion: Elevated NLR (NLR1 > 2.249, NLR2 > 2.439, NLR3 > 1.91) was associated with worse prognosis in advanced LMS, suggesting its potential as a prognostic biomarker. Prospective studies are needed to confirm these findings.