Plasmatic BRAF-V600E allele fraction as a prognostic factor in metastatic colorectal cancer treated with BRAF combinatorial treatments.

BACKGROUND: Combination of a BRAF inhibitor (BRAFi) and an anti-epidermal growth factor receptor (EGFR), with or without a MEK inhibitor (MEKi), improves survival in BRAF-V600E-mutant metastatic colorectal cancer (mCRC) over standard chemotherapy. However, responses are heterogeneous and there are no available biomarkers to assess patient prognosis or guide doublet- or triplet-based regimens. In order to better characterize the clinical heterogeneity observed, we assessed the prognostic and predictive role of the plasmatic BRAF allele fraction (AF) for these combinations. PATIENTS AND METHODS: A prospective discovery cohort including 47 BRAF-V600E-mutant patients treated with BRAFi-anti-EGFR ± MEKi in clinical trials and real-world practice was evaluated. Results were validated in an independent multicenter cohort (n= 29). Plasmatic BRAF-V600E AF cut-off at baseline was defined in the discovery cohort with droplet digital PCR (ddPCR). All patients had tissue-confirmed BRAF-V600E mutations. RESULTS: Patients with high AF have major frequency of liver metastases and more metastatic sites. In the discovery cohort, median progression-free survival (PFS) and overall survival (OS) were 4.4 and 10.1 months, respectively. Patients with high BRAF AF (≥2%, n = 23) showed worse PFS [hazard ratio (HR) 2.97, 95% confidence interval (CI) 1.55-5.69; P = 0.001] and worse OS (HR 3.28, 95% CI 1.58-6.81; P = 0.001) than low-BRAF AF patients (<2%, n = 24). In the multivariable analysis, BRAF AF levels maintained independent significance. In the validation cohort, high BRAF AF was associated with worse PFS (HR 3.83, 95% CI 1.60-9.17; P = 0.002) and a trend toward worse OS was observed (HR 1.86, 95% CI 0.80-4.34; P = 0.15). An exploratory analysis of predictive value showed that high-BRAF AF patients (n = 35) benefited more from triplet therapy than low-BRAF AF patients (n = 41; PFS and OS interaction tests, P < 0.01). CONCLUSIONS: Plasmatic BRAF AF determined by ddPCR is a reliable surrogate of tumor burden and aggressiveness in BRAF-V600E-mutant mCRC treated with a BRAFi plus an anti-EGFR with or without a MEKi and identifies patients who may benefit from treatment intensification. Our results warrant further validation of plasmatic BRAF AF to refine clinical stratification and guide treatment strategies.

Encorafenib plus cetuximab with or without binimetinib in patients with BRAF V600E-mutated metastatic colorectal cancer: real-life data from an Italian multicenter experience.

BACKGROUND: Encorafenib plus cetuximab with or without binimetinib showed increased objective response rate (ORR), progression-free survival (PFS), and overall survival (OS) compared with chemotherapy plus anti-EGFR in previously treated patients with BRAF V600E-mutated (mut) metastatic colorectal cancer (mCRC). Although no formal comparison was planned, addition of binimetinib to encorafenib plus cetuximab did not provide significant efficacy advantage. PATIENTS AND METHODS: This real-life study was aimed at evaluating safety, activity, and efficacy of encorafenib plus cetuximab with or without binimetinib in patients with BRAF V600E-mut mCRC treated at 21 Italian centers within a nominal use program launched in May 2019. RESULTS: Out of 133 patients included, 97 (73%) received encorafenib plus cetuximab (targeted doublet) and 36 (27%) the same therapy plus binimetinib (targeted triplet). Most patients had Eastern Cooperative Group Performance Status (ECOG-PS) of 0 or 1 (86%), right-sided primary tumor (69%), and synchronous disease (66%). Twenty (15%) tumors were DNA mismatch repair deficiency (dMMR)/microsatellite instability (MSI)-high. As many as 44 (34%) patients had received two or more prior lines of therapy, 122 (92%) were previously exposed to oxaliplatin, and 109 (82%) to anti-vascular endothelial growth factor (anti-VEGF). Most frequent adverse events were asthenia (62%) and anti-EGFR-related skin rash (52%). Any grade nausea (P = 0.03), vomiting (P = 0.04), and diarrhea (P = 0.07) were more frequent with the triplet therapy, while melanocytic nevi were less common (P = 0.06). Overall, ORR and disease control rate (DCR) were 23% and 69%, respectively, with numerically higher rates in the triplet group (ORR 31% versus 17%, P = 0.12; DCR 78% versus 65%, P = 0.23). Median PFS and OS were 4.5 and 7.2 months, respectively. Worse ECOG-PS, peritoneal metastases, and more than one prior treatment were independent poor prognostic factors for PFS and OS. Clonality of BRAF mutation measured as adjusted mutant allele fraction in tumor tissue was not associated with clinical outcome. CONCLUSIONS: Our real-life data are consistent with those from the BEACON trial in terms of safety, activity, and efficacy. Patients in good general condition and not heavily pretreated are those more likely to derive benefit from the targeted treatment.

Temozolomide and irinotecan (TEMIRI regimen) as salvage treatment of irinotecan-sensitive advanced colorectal cancer patients bearing MGMT methylation.

Background: Non-randomized studies showed that temozolomide (TMZ) achieves an average 10% response rate in heavily pretreated metastatic colorectal cancer (mCRC) patients with promoter methylation of the DNA repair gene O6-methylguanine-DNA methyltransferase (MGMT). In this phase II trial, irinotecan and temozolomide (TEMIRI) combination regimen was assessed in irinotecan-sensitive, MGMT methylated/microsatellite stable (MSS) pretreated mCRC patients. Patients and methods: Key inclusion criteria were centrally confirmed MGMT methylation by methylation-specific PCR, MSS mCRC, progression after at least two prior chemotherapy regimens for advanced disease and irinotecan-free interval >3 months. TEMIRI (TMZ 150 mg/m2 on days 1-5 plus irinotecan 100 mg/m2 on days 1, 15 q28 days) was administered for six cycles, followed by maintenance with TMZ. The primary end point was overall response rate (ORR). Exploratory translational analyses included MGMT immunohistochemistry (IHC) and methyl-BEAMing (MB). Results: Between December 2014 and June 2017, 25 patients were enrolled. The primary end point was met, since six patients achieved a partial response [ORR 24%, 95% confidence interval (CI) 11% to 43%]. At a median follow-up of 15.6 months, median progression-free survival (mPFS) and overall survival (mOS) were 4.4 and 13.8 months, respectively. Only four (16%) patients had ≥ grade 3 (CTCAE 4.0) adverse events. All patients whose cancer was MGMT-positive IHC were non-responders. Consistently, patients with MGMT-negative/low tumors had a significantly longer mPFS than others (6.9 versus 2.0 months; hazard ratio = 0.29, 95% CI 0.02-0.41; P = 0.003) and a non-significant trend for longer mOS. MB testing showed similar accuracy. Conclusions: TEMIRI regimen is a safe and active option in pre-treated, irinotecan-sensitive mCRC patients with MGMT methylation.