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BACKGROUND: Recent data suggest that BRAFV600E-mutated metastatic colorectal cancer (mCRC) patients with right-sided tumours and ECOG-PS = 0 may achieve benefit from the triplet regimen differently than those with left-sided tumours and ECOG-PS > 0. METHODS: The predictive impact of primary sidedness and ECOG-PS was evaluated in a large real-life dataset of 296 BRAFV600E-mutated mCRC patients treated with upfront triplet or doublet ± bevacizumab. Biological differences between right- and left-sided BRAFV600E-mutated CRCs were further investigated in an independent cohort of 1162 samples. RESULTS: A significant interaction effect between primary sidedness and treatment intensity was reported in terms of both PFS (p = 0.010) and OS (p = 0.003), with a beneficial effect of the triplet in the right-sided group and a possible detrimental effect in the left-sided. No interaction effect was observed between ECOG-PS and chemo-backbone. In the MSS/pMMR population, a consistent trend for a side-related subgroup effect was observed when FOLFOXIRI ± bevacizumab was compared to oxaliplatin-based doublets±bevacizumab (p = 0.097 and 0.16 for PFS and OS, respectively). Among MSS/pMMR tumours, the BM1 subtype was more prevalent in the right-sided group (p = 0.0019, q = 0.0139). No significant differences were observed according to sidedness in the MSI-H/dMMR population. CONCLUSIONS: Real-life data support the use of FOLFOXIRI ± bevacizumab only in BRAFV600E-mutated mCRC patients with right-sided tumours.

BACKGROUND: In mCRC, CEA is used to monitor response to systemic therapy together with imaging. After the end of induction, no major improvement in tumour shrinkage is expected, and the availability of a marker able to predict progressive disease (PD) versus no-PD might allow avoiding CT scans. METHODS: We pooled data from patients with baseline CEA ≥ 10 ng/mL included in TRIBE and TRIBE2 studies with the aim of identifying a threshold for percent increase of CEA from nadir able to predict PD after the end of the induction therapy. RESULTS: In total, 1178 paired CEA and radiological assessments from 434 patients were included. According to the optimal cut-off determined by ROC, a CEA increase of at least 120% from nadir differentiated between PD and no-PD with a sensitivity of 74% and a specificity of 78%, excluding PD in the 92% of radiological assessments and allowing to avoid the 67% of CT scans. However, CEA cut-off of 120% was not able to detect radiological PD in 26% of cases. In order to mitigate this issue, a different clinically relevant threshold was evaluated based on the best sensitivity cut-off. Therefore, using any CEA increase from nadir as a threshold, the sensitivity grew to 93% and only in the 7% of cases the radiological PD was not detected. CONCLUSIONS: In mCRC with baseline CEA ≥ 10 ng/mL, CEA values can accurately predict PD versus no-PD after the end of the first-line induction therapy.