ABSTRACT
Immune checkpoint inhibitors and immune-related biomarkers are increasingly investigated in rectal cancer (RC). We retrospectively analysed PD-L1 expression in diagnostic biopsy and resection samples from RC patients treated at our centre between 2000 and 2020. PD-L1 immunostaining (22C3 clone) was evaluated according to tumour proportion (TPS), immune cell (ICS), and the combined positive score (CPS). Eighty-three patients were included. At diagnosis, PD-L1 expression ≥1%/≥5% was observed in 15.4%/0%, 80.7%/37.4%, and 69.2%/25.6% of patients based on TPS, ICS, and CPS, respectively. At surgery, the respective figures were 4.6%/1.5%, 60.2%/32.5%, and 50.7%/26.2%. Using the 1% cut-off and regardless of the scoring system, PD-L1 was less expressed in surgery than biopsy samples (p ≤ 0.04). In paired specimens, PD-L1-ICS reduction was especially observed following neoadjuvant long-course (chemo)radiotherapy (p = 0.03). PD-L1-ICS of ≥5% in surgical samples (HR: 0.17; p = 0.02), and a biopsy-to-surgery increase in PD-L1-ICS (HR: 0.19; p = 0.04) was predictive for longer disease-free survival, while the PD-L1-ICS of either ≥1% (HR 0.28; p = 0.04) or ≥5% (HR 0.19; p = 0.03) in surgical samples and the biopsy-to-surgery increase in PD-L1-ICS (HR: 0.20; p = 0.04) were associated with better overall survival. Our study suggests that PD-L1 expression in RC is largely reflective of immune cell infiltration, and its presence/increase in surgical samples predicts better outcomes.
ABSTRACT
BACKGROUND: Encorafenib plus cetuximab is efficient in anti-EGFR-naïve patients with BRAFV600E mutated (BRAFm) metastatic colorectal cancer (mCRC). No data are available concerning the efficacy of BRAF inhibitors associated with anti-EGFRs (B + E) in patients previously treated with an anti-EGFR agent. METHODS: We retrospectively collected a series of patients with BRAFm mCRC treated with B + E after previous anti-EGFR treatment, in 14 centers. Progression-free survival (PFS) and overall survival (OS) were calculated from the start of treatment, and we reported objective response and disease control rates (ORR, DCR; RECIST V1.1). RESULTS: Twenty-five BRAFm mCRC patients were enrolled. Prior to B + E treatment, 4/10/11 patients were treated with 1/2/> 2 previous treatment lines. Ten patients received previous panitumumab, 14 cetuximab, 1 both. Immediate progression with previous anti-EGFR was reported for 7 patients. Anti-BRAF was encorafenib for 21 patients, dabrafenib for 4 patients, with cetuximab for 24 patients and panitumumab for 1 patient. ORR was 40% (10 patients) and DCR was 80% (20 patients). Median PFS and OS were 4.8 months (95% CI, 4.01-7.95) and 10.1 months (95% CI, 7.75-NR). DCR amongst patients with previous primary resistance to anti-EGFR (N = 7) was 100%. Two patients discontinued B + E due to drug-related adverse event. CONCLUSIONS: Though in a limited retrospective series of patients, these results show the efficacy of the combination of anti-BRAF and anti-EGFRs in BRAFm mCRC patients previously treated with an anti-EGFR. The use of this combination should thus not be ruled out in this population with limited therapeutic options.
