A phase II study of tumor microenvironment profiling at single cell level in patients with locally advanced cervical cancer (LACC) treated with immunotherapy combined with concurrent chemoradiotherapy (CICRT).

5518 Background: Concurrent chemoradiotherapy (CCRT) followed by intrauterine brachytherapy is the standard treatment for LACC, while the therapeutic efficacy can be limited by an immunosuppressive tumor microenvironment (TME). PD-1 inhibition has displayed efficacy and a clinically manageable safety profile in patients with cervical cancer. Single-cell RNA sequencing (scRNA-seq) of paired pre-treatment and on treatment samples offers a dynamic and detailed examination of the transcriptomic changes in the TME under different treatment conditions. Here, we present the results of patients with LACC treated with either CCRT or CICRT, along with the paired analysis of various cellular components in the TME from pre-treatment and on-treatment samples through scRNA-seq. Methods: Patients with untreated, high-risk stage III–IVA and stage IVB cervical cancer (limited to groin lymph nodes metastasis) according to FIGO 2018, with measurable disease per RECIST 1.1 and ECOG performance status ≤1, were included and randomly assigned (2:1) to receive either tislelizumab combined with chemoradiotherapy, followed by tislelizumab (200mg, Q3W for 6 cycles), or chemoradiotherapy alone (cisplatin 40 mg/m 2 , Q1W for 3-5 cycles; pelvic external beam radiation therapy 50.4 Gy in 28 fractions; brachytherapy 28 Gy in 4 fractions). Single-cell transcriptomic profiles were obtained from paired biopsies at two time points: pre-treatment and on-treatment. Results: A total of 18 patients were included, with 12 single-cell analysis samples collected (6 CCRT and 6 CICRT). At the end of pelvic radiotherapy, the CICRT group exhibited a trend toward a greater reduction in tumor volume compared to the CCRT group (7.4% vs. 3.0%; p = 0.08), albeit not reaching statistical significance. Cancer cells in CICRT group exhibited with an increased expression of MHCII genes and chemotaxis-related genes on treatment. CICRT reduced the proportion of immunosuppressive regulatory CD4+ T cells and exhausted CD8+ T cells compared to CCRT. In myeloid cells, TNF-α signaling via NF-κB and inflammatory response pathways were enriched following CICRT, and tumor-associated macrophages were reprogrammed to a relatively pro-tumorigenic phenotype. The cancer-associated fibroblast (CAF) subset CAF_FTH1, characterized by a pro-inflammatory gene signature, was increased during CICRT. Moreover, CICRT induced higher expression of MHC-II-related molecules and chemotaxis-associated genes in CAFs compared to CCRT. Conclusions: The CICRT treatment group demonstrated a trend toward improved local control during the early phase of treatment compared to the CCRT group. Single-cell profiling revealed the differences in the potential to reshape the TME between CCRT and CICRT, with CICRT showing a greater ability to reduce immune suppression. Clinical trial information: ChiCTR2200067166 .