The MAPK cascade plays a crucial role in tumor cell proliferation and survival. Accumulating evidence suggests that mutations in the BRAF oncogene are not only associated with poor prognosis but also ...linked with less benefit when treated with anti-epidermal growth factor receptor antibodies in metastatic colorectal cancer (mCRC). Targeting this molecular aberration has thus become a matter of particular interest in mCRC drug development. In contrast to other malignances such as BRAF mutant melanoma, efficacy observed with BRAF inhibitors in monotherapy in mCRC is poor. Several mechanisms of resistance have been identified leading to the development of different treatment strategies that have shown promising activity in early clinical trials. Hence, rational combination of targeted therapies is expected to further increase the efficacy of selective BRAF inhibitors. Herein, we discuss the main clinical and molecular characteristics of BRAF mutant colorectal cancer and its translation into the clinic, with a focus on developmental therapeutics and combination strategies. In addition, we contextualize the available data with potential future approaches that include the extended access to next-generation sequencing platforms and gene expression strategies for molecular subtyping. These approaches will facilitate the identification of certain patient profiles providing more therapeutic possibilities.
Transforming growth factor beta (TGFβ) is a pleiotropic cytokine that plays a key role in both physiologic and pathologic conditions, including cancer. Importantly, TGFβ can exhibit both ...tumor-suppressive and oncogenic functions. In normal epithelial cells TGFβ acts as an antiproliferative and differentiating factor, whereas in advanced tumors TGFβ can act as an oncogenic factor by creating an immune-suppressive tumor microenvironment, and inducing cancer cell proliferation, angiogenesis, invasion, tumor progression, and metastatic spread. A wealth of preclinical findings have demonstrated that targeting TGFβ is a promising means of exerting antitumor activity. Based on this rationale, several classes of TGFβ inhibitors have been developed and tested in clinical trials, namely, monoclonal, neutralizing, and bifunctional antibodies; antisense oligonucleotides; TGFβ-related vaccines; and receptor kinase inhibitors. It is now >15 years since the first clinical trial testing an anti-TGFβ agent was engaged. Despite the promising preclinical studies, translation of the basic understanding of the TGFβ oncogenic response into the clinical setting has been slow and challenging. Here, we review the conclusions and status of all the completed and ongoing clinical trials that test compounds that inhibit the TGFβ pathway, and discuss the challenges that have arisen during their clinical development. With none of the TGFβ inhibitors evaluated in clinical trials approved for cancer therapy, clinical development for TGFβ blockade therapy is primarily oriented toward TGFβ inhibitor combinations. Immune checkpoint inhibitors are considered candidates, albeit with efficacy anticipated to be restricted to specific populations. In this context, we describe current efforts in the search for biomarkers for selecting the appropriate cancer patients who are likely to benefit from anti-TGFβ therapies. The knowledge accumulated during the last 15 years of clinical research in the context of the TGFβ pathway is crucial to design better, innovative, and more successful trials.
•TGFβ is a complex cytokine with both antitumor and oncogenic functions.•TGFβ blockade has demonstrated promising antitumor activity in various preclinical models.•The TGFβ pleiotropic role challenges its evaluation as a therapeutic target in clinical trials.•Different anti-TGFβ agents have been developed and tested in clinical trials with diverse and sometimes limited efficacies.•Novel biomarkers are under development to better select patients who may benefit from TGFβ blockade.
Colorectal cancers with
BRAF
mutations have an aggressive natural history and are often resistant to therapy. A treatment regimen that combined BRAF inhibition, MET inhibition, and blocking of EGFR ...signaling resulted in a response rate of 26% and a median overall survival of 9 months.
Accumulating evidence has identified Fusobacterium as an important pathogenic gut bacterium associated with colorectal cancer. Nevertheless, only limited data exist about the role of this bacterium ...in locally advanced rectal cancer (LARC). In this study, we quantified Fusobacterium nucleatum in untreated and post-neoadjuvant chemoradiotherapy (nCRT) samples from LARC patients and investigated its association with therapy response and survival.
A total of 254 samples from 143 patients with rectal adenocarcinomas were analyzed for the presence and abundance of F. nucleatum using RNA in situ hybridization and digital image analysis. Assay accuracy was determined using infected cell lines and tumor samples with available quantitative PCR data. We studied the impact of F. nucleatum load on pathologic complete response and relapse-free survival. Treatment-induced changes were evaluated in paired pre- and post-nCRT samples (n = 71). Finally, tumor microenvironment changes during nCRT were assessed in paired samples (n = 45) by immune contexture analysis.
F. nucleatum tissue levels by RNA in situ hybridization strongly correlated with quantitative PCR (r = 0.804, P < 0.001). F. nucleatum abundance was higher in untreated median, 7.4; 95% confidence interval (3.7–16.2) compared with treated median, 1.6; 95% confidence interval (1.3–2.4) tumors (P <0.001) with 58% (73/126) and 26% (22/85) positive tumors, respectively (P < 0.001). Baseline F. nucleatum levels were not associated with pathologic complete response. F. nucleatum positivity after nCRT, but not baseline status, significantly increased risk of relapse hazard ratio = 7.5, 95% confidence interval (3.0–19.0); P < 0.001. Tumors that turned F. nucleatum-negative after nCRT had a strong increase in CD8+ T cells post-nCRT (P < 0.001), while those that persisted F. nucleatum-positive after nCRT lacked CD8+ T cells induction in post-nCRT samples compared with baseline (P = 0.69).
F. nucleatum persistence post-nCRT is associated with high relapse rates in LARC, potentially linked to suppression of immune cytotoxicity.
•Biomarkers to predict response or relapse after neoadjuvant chemoradiotherapy (nCRT) remain an unmet clinical need in LARC.•F. nucleatum is significantly enriched in colorectal tumor tissue but its role in rectal cancer is poorly studied.•nCRT significantly reduced F. nucleatum tissue abundance in post-treatment surgical samples.•F. nucleatum persistence after nCRT significantly increased the risk of relapse.•F. nucleatum positivity in post-nCRT associated with lack of immune cytotoxicity activation.
Circulating tumor DNA (ctDNA) is a potential source for tumor genome analysis. We explored the concordance between the mutational status of RAS in tumor tissue and ctDNA in metastatic colorectal ...cancer (mCRC) patients to establish eligibility for anti-epidermal growth factor receptor (EGFR) therapy.
A prospective-retrospective cohort study was carried out. Tumor tissue from 146 mCRC patients was tested for RAS status with standard of care (SoC) PCR techniques, and Digital PCR (BEAMing) was used both in plasma and tumor tissue.
ctDNA BEAMing RAS testing showed 89.7% agreement with SoC (Kappa index 0.80; 95% CI 0.71 − 0.90) and BEAMing in tissue showed 90.9% agreement with SoC (Kappa index 0.83; 95% CI 0.74 − 0.92). Fifteen cases (10.3%) showed discordant tissue-plasma results. ctDNA analysis identified nine cases of low frequency RAS mutations that were not detected in tissue, possibly due to technical sensitivity or heterogeneity. In six cases,RAS mutations were not detected in plasma, potentially explained by low tumor burden or ctDNA shedding. Prediction of treatment benefit in patients receiving anti-EGFR plus irinotecan in second- or third-line was equivalent if tested with SoC PCR and ctDNA. Forty-eight percent of the patients showed mutant allele fractions in plasma below 1%.
Plasma RAS determination showed high overall agreement and captured a mCRC population responsive to anti-EGFR therapy with the same predictive level as SoC tissue testing. The feasibility and practicality of ctDNA analysis may translate into an alternative tool for anti-EGFR treatment selection.
This is the first study that seeks to establish the prognostic value of circulating tumor cell (CTC) (determined by CellSearch system) in patients with stage III CRC.
Our results suggest that given ...the low number of CTC in patients with localized CRC and the particular pattern of metastatic dissemination in patients with CRC, it is likely that CTC does not have a prognostic role in this setting.
The prognostic role of circulating tumor cells (CTC) in early colorectal cancer (CRC) has not been determined yet. We evaluated the potential prognostic value of CTC in stage III CRC patients.
Prospective multicenter study of 519 patients with stage III CRC recruited between January 2009 and June 2010. CTC were enumerated with the CellSearch System after primary tumor resection and before the start of adjuvant therapy. A total of 472 patients were included in the analysis.
CTC ≥1, ≥2, ≥3 and ≥5 were detected in 166 (35%), 93 (20%), 57 (12%) and 34 (7%) patients, respectively. Median follow-up was 40 months. In the overall population, CTC ≥1 (disease-free survival (DFS): HR 0.97,P = 0.85; overall survival (OS): HR 1.03,P = 0.89), ≥2 (DFS: HR 1.07,P = 0.76; OS: HR 1.02,P = 0.95), ≥3 (DFS: HR 0.96,P = 0.87; OS: HR 0.74,P = 0.41) and ≥5 (DFS: HR 0.72,P = 0.39; OS: HR 0.48,P = 0.21) were not associated with worse DFS and OS. No clinicopathological characteristics were significantly associated with the presence of CTC. In patients with disease relapse, the proportion with CTC ≥1 was not significantly different between those with single versus multiple metastatic locations (37.9% versus 31.4%,P = 0.761). In the multivariate analysis, CTC ≥1 was not an independent prognostic factor for DFS (HR 0.97,P = 0.87) and OS (HR 0.96,P = 0.89).
CTC detection was not associated with worse DFS and OS in patients with stage III CRC. Given the scarcity of CTC in these patients, it is likely that CTC determined by CellSearch system does not have a prognostic role in this setting. However, a longer follow-up is needed.
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.
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.
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).
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.
•Plasmatic BRAF AF has a prognostic role for survival in mCRC treated with BRAF inhibitors.•ddPCR, applied in a cohort including a real-world population, mirrored those of the BEACON clinical trial using next-generation sequencing (NGS).•ddPCR detects BRAF AF in circulating tumor DNA (ctDNA) with high reproducibility and sensitivity, offering a validated alternative to NGS.•Identifying prognostic factors in BRAF-mutant mCRC is crucial to stratify patients and guide treatment strategies.
This single-arm phase II study investigated the EGFR monoclonal antibody necitumumab plus modified FOLFOX6 (mFOLFOX6) in first-line treatment of locally advanced or metastatic colorectal cancer ...(mCRC).
Patients received 800-mg intravenous necitumumab (day 1; 2-week cycles), followed by oxaliplatin 85 mg m(-2), folinic acid 400 mg m(-2), and 5-fluorouracil (400 mg m(-2) bolus then 2400 mg m(-2) over 46 h). Radiographic evaluation was performed every 8 weeks until progression. Primary endpoint was objective response rate.
Forty-four patients were enrolled and treated. Objective response rate was 63.6% (95% confidence interval 47.8-77.6); complete response was observed in four patients; median duration of response was 10.0 months (7.0-16.0). Median overall survival (OS) and progression-free survival (PFS) were 22.5 (11.0-30.0) and 10.0 months (7.0-12.0), respectively. Clinical outcome was better in patients with KRAS exon 2 wild type (median OS 30.0 months (23.0-NA); median PFS 12.0 (8.0-20.0)), compared with KRAS exon 2 mutant tumours (median OS 7.0 months (5.0-37.0); median PFS 7.0 (4.0-18.0)). The most common grade ⩾3 adverse events were neutropenia (29.5%), asthenia (27.3%), and rash (20.5%).
First-line necitumumab+mFOLFOX6 was active with manageable toxicity in locally advanced or mCRC; additional evaluation of the impact of tumour RAS mutation status is warranted.
POLE and POLD1 proofreading deficiency (POLE/D1pd) define a rare subtype of ultramutated metastatic colorectal cancer (mCRC; over 100 mut/Mb). Disease-specific data about the activity and efficacy of ...immune checkpoint inhibitors (ICIs) in POLE/D1pd mCRC are lacking and it is unknown whether outcomes may be different from mismatch repair-deficient (dMMR)/microsatellite instability-high (MSI-H) mCRCs treated with ICIs.
In this global study, we collected 27 patients with mCRC harboring POLE/D1 mutations leading to proofreading deficiency and treated with anti-programmed cell death-ligand 1 alone +/− anti-cytotoxic T-lymphocyte antigen-4 agents. We collected clinicopathological and genomic characteristics, response, and survival outcomes after ICIs of POLE/D1pd mCRC and compared them with a cohort of 610 dMMR/MSI-H mCRC patients treated with ICIs. Further genomic analyses were carried out in an independent cohort of 7241 CRCs to define POLE and POLD1pd molecular profiles and mutational signatures.
POLE/D1pd was associated with younger age, male sex, fewer RAS/BRAF driver mutations, and predominance of right-sided colon cancers. Patients with POLE/D1pd mCRC showed a significantly higher overall response rate (ORR) compared to dMMR/MSI-H mCRC (89% versus 54%; P = 0.01). After a median follow-up of 24.9 months (interquartile range: 11.3-43.0 months), patients with POLE/D1pd showed a significantly superior progression-free survival (PFS) compared to dMMR/MSI-H mCRC hazard ratio (HR) = 0.24, 95% confidence interval (CI) 0.08-0.74, P = 0.01 and superior overall survival (OS) (HR = 0.38, 95% CI 0.12-1.18, P = 0.09). In multivariable analyses including the type of DNA repair defect, POLE/D1pd was associated with significantly improved PFS (HR = 0.17, 95% CI 0.04-0.69, P = 0.013) and OS (HR = 0.24, 95% CI 0.06-0.98, P = 0.047). Molecular profiling showed that POLE/D1pd tumors have higher tumor mutational burden (TMB). Responses were observed in both subtypes and were associated with the intensity of POLE/D1pd signature.
Patients with POLE/D1pd mCRC showed more favorable outcomes compared to dMMR/MSI-H mCRC to treatment with ICIs in terms of tumor response and survival.
•POLE/D1pd is associated with male sex, younger age, right-sided primary tumor, and uncommon KRAS mutations in mCRC.•A significantly higher ORR is observed for POLE/D1pd compared to dMMR/MSI-H mCRC treated with ICIs.•POLE/D1pd mCRC exposed to ICIs have a higher PFS and OS than dMMR/MSI-H.•POLE/D1pd mCRCs are enriched in single nucleotide variant while dMMR/MSI-H are enriched in frameshift mutations.•Non-responder POLEpd mCRCs have lower TMB than responders and lower intensity of the POLE signature.
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