[89Zr]Zr-cetuximab PET/CT as biomarker for cetuximab monotherapy in patients with RAS wild-type advanced colorectal cancer.

PURPOSE: One-third of patients with RAS wild-type mCRC do not benefit from anti-EGFR monoclonal antibodies. This might be a result of variable pharmacokinetics and insufficient tumor targeting. We evaluated cetuximab tumor accumulation on [89Zr]Zr-cetuximab PET/CT as a potential predictive biomarker and determinant for an escalating dosing strategy. PATIENTS AND METHODS: PET/CT imaging of [89Zr]Zr-cetuximab (37 MBq/10 mg) after a therapeutic pre-dose (500 mg/m2 ≤ 2 h) cetuximab was performed at the start of treatment. Patients without visual tumor uptake underwent dose escalation and a subsequent [89Zr]Zr-cetuximab PET/CT. Treatment benefit was defined as stable disease or response on CT scan evaluation after 8 weeks. RESULTS: Visual tumor uptake on [89Zr]Zr-cetuximab PET/CT was observed in 66% of 35 patients. There was no relationship between PET positivity and treatment benefit (52% versus 80% for PET-negative, P = 0.16), progression-free survival (3.6 versus 5.7 months, P = 0.15), or overall survival (7.1 versus 9.4 months, P = 0.29). However, in 67% of PET-negative patients, cetuximab dose escalation (750-1250 mg/m2) was applied, potentially influencing outcome in this group. None of the second [89Zr]Zr-cetuximab PET/CT was positive. Eighty percent of patients without visual tumor uptake had treatment benefit, making [89Zr]Zr-cetuximab PET/CT unsuitable as a predictive biomarker. Tumor SUVpeak did not correlate to changes in tumor size on CT (P = 0.23), treatment benefit, nor progression-free survival. Cetuximab pharmacokinetics were not related to treatment benefit. BRAF mutations, right-sidedness, and low sEGFR were correlated with intrinsic resistance to cetuximab. CONCLUSION: Tumor uptake on [89Zr]Zr-cetuximab PET/CT failed to predict treatment benefit in patients with RAS wild-type mCRC receiving cetuximab monotherapy. BRAF mutations, right-sidedness, and low sEGFR correlated with intrinsic resistance to cetuximab.

Correction to: [89Zr]Zr-cetuximab PET/CT as biomarker for cetuximab monotherapy in patients with RAS wild-type advanced colorectal cancer.

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Optimal use of anti-EGFR monoclonal antibodies for patients with advanced colorectal cancer: a meta-analysis.

This meta-analysis was performed to determine the optimal use of anti-EGFR mAb in the treatment of metastasized colorectal cancer (mCRC). Seventeen randomized clinical trials were included, all evaluating the added value of anti-EGFR mAb to standard treatment line in patients with KRAS wild-type mCRC. Hazard and odds ratios were pooled using a random effect model, weighted according to cohort size. Pooled data of six first- and two second-line studies demonstrated a significantly improved ORR (OR 1.62, CI 1.27-2.04; OR 4.78, CI 3.39-6.75, respectively) and PFS (HR 0.79, CI 0.67-0.94; HR 0.80, CI 0.71-0.91, respectively) with the addition of anti-EGFR mAb to chemotherapy, while OS remained similar. Two third-line anti-EGFR mAb monotherapy studies revealed an improved PFS and OS (HR 0.44, CI 0.35-0.52; HR 0.55, CI 0.41-0.74). Addition of anti-EGFR versus anti-VEGF mAb to first-line chemotherapy was evaluated in three studies; ORR and PFS were comparable, while OS was improved (HR 0.8, CI 0.65-0.97). The influence of the chemotherapy backbone on anti-EGFR mAb efficacy, evaluated with meta-regression, indicated a higher ORR with irinotecan-based versus oxaliplatin-based regimens, but comparable PFS and OS. Reported toxicity (≥3 grade) increased ~20% in all treatment lines with the addition of anti-EGFR mAb. Anti-EGFR treatment significantly improves response and survival outcome of patients with (K)RAS wild-type mCRC, regardless of treatment line or chemotherapeutic backbone. Saving anti-EGFR mAb as third-line monotherapy is a valid and effective option to prevent high treatment burden caused by combination therapy. Combination treatment with anti-EGFR mAb to achieve radical resection of metastases needs further investigation.

Radiomics analysis of pre-treatment [18F]FDG PET/CT for patients with metastatic colorectal cancer undergoing palliative systemic treatment.

BACKGROUND: The aim of this study was to assess radiomics features on pre-treatment [18F]FDG positron emission tomography (PET) as potential biomarkers for response and survival in patients with metastatic colorectal cancer (mCRC). METHODS: Patients with mCRC underwent [18F]FDG PET/computed tomography (CT) prior to first- or third-line palliative systemic treatment. Tumour lesions were semiautomatically delineated and standard uptake value (SUV), metabolically active tumour volume (MATV), total lesion glycolysis (TLG), entropy, area under the curve of the cumulative SUV-volume histogram (AUC-CSH), compactness and sphericity were obtained. RESULTS: Lesions of 47 patients receiving third-line systemic treatment had higher SUVmax, SUVpeak, SUVmean, MATV and TLG, and lower AUC-CSH, compactness and sphericity compared to 52 patients receiving first-line systemic treatment. Therefore, first- and third-line groups were evaluated separately. In the first-line group, anatomical changes on CT correlated negatively with TLG (ρ = 0.31) and MATV (ρ = 0.36), and positively with compactness (ρ = -0.27) and sphericity (ρ = -0.27). Patients without benefit had higher mean entropy (p = 0.021). Progression-free survival (PFS) and overall survival (OS) were worse with a decreased mean AUC [hazard ratio (HR) 0.86, HR 0.77] and increase in mean MATV (HR 1.15, HR 1.22), sum MATV (HR 1.14, HR 1.19), mean TLG (HR 1.16, HR 1.22) and sum TLG (HT1.12, HR1.18). In the third-line group, AUC-CSH correlated negatively with anatomical change (ρ = 0.21). PFS and OS were worse with an increased mean MATV (HR 1.27, HR 1.68), sum MATV (HR 1.35, HR 2.04), mean TLG (HR 1.29, HR 1.52) and sum TLG (HT 1.27, HR 1.80). SUVmax and SUVpeak negatively correlated with OS (HR 1.19, HR 1.21). Cluster analysis of the 10 radiomics features demonstrated no complementary value in identifying aggressively growing lesions or patients with impaired survival. CONCLUSION: We demonstrated an association between improved clinical outcome and pre-treatment low tumour volume and heterogeneity as well as high sphericity on [18F]FDG PET. Future PET imaging research should include radiomics features that incorporate tumour volume and heterogeneity when correlating PET data with clinical outcome.