Efficacy of PD-1 inhibitors combined with pegylated liposomal doxorubicin and dacarbazine compared with liposomal doxorubicin and dacarbazine in advanced leiomyosarcoma patients: a retrospective, single-institutional cohort study

BACKGROUND: PD-1 inhibitor monotherapy is ineffective for metastatic leiomyosarcoma (LMS), but it remains unclear whether PD-1 inhibitors demonstrate any efficacy when combined with chemotherapy. This study retrospectively evaluated pegylated liposomal doxorubicin (PLD) and dacarbazine (DTIC) with/without PD-1 inhibitors for advanced/metastatic LMS patients treated in our single institution. METHODS: The inclusion criteria were a confirmed histological diagnosis of LMS, treatment between January 2020 and March 2022, measurable disease (evaluated by CT or MRI), an Eastern Cooperative Oncology Group (ECOG) performance status ≤2, and age ≥18 years. The endpoints were progression-free survival (PFS), overall survival (OS), and overall response rate (ORR). RESULTS: A total of 41 patients were included in this study, among whom 21 received PLD and DTIC alone while 20 received PLD and DTIC with PD-1 inhibitors. There were no differences of clinical characteristics between the two groups. Although the chemo plus PD-1 group had a better ORR (30% vs. 4.8%, P=0.04), there were no benefits in terms of disease control rate (DCR) (80% vs. 66.7%, P=0.29), PFS (8.8 months, 95% CI: 4.57–13.0 vs. 6.1 months, 95% CI: 3.03–9.14, P=0.54), and OS (not reached in both groups, P=0.84) when compared to chemo alone. Multiple treatment lines and previous use of tyrosine kinase inhibitors (TKIs) seemed to be negative factors for PFS in the univariate analysis, but failed to be significant in the multivariate analysis. CONCLUSIONS: This retrospective, single-institutional study showed that PD-1 inhibitors combined with standard PLD and DTIC chemotherapy failed to exert benefits on survival for LMS patients. Considering the small sample size and retrospective clinical research design, further explorations are needed to verify the conclusion.