Publications by authors named "Chee-Keong Toh"

Purpose: Androgen receptor splice variant 7 (ARV-7) is a resistance mechanism to hormonal therapy in metastatic castrate-resistant prostate cancer (mCRPC). It has been associated with poor outcomes. On progression to castrate resistance, ARV-7 positivity has been identified in global populations at an incidence of 17.

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Article Synopsis
  • - The study investigates genetic predispositions to dual primary cancers of the breast and lung in 55 never-smoking Singapore patients, focusing on inherited variants beyond traditional cancer syndromes.
  • - Exome sequencing revealed 19 pathogenic or likely pathogenic variants across 16 genes in 31% of the patients, including both well-known cancer genes like BRCA2 and lesser-known ones like EXT2.
  • - Findings highlight the importance of impaired DNA repair mechanisms in developing multiple cancers, suggesting that these genetic variants should be explored in further research among diverse populations.
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Introduction: Although immune checkpoint inhibitors (ICIs) have dramatically improved outcomes for nononcogene-addicted NSCLC, monotherapy with programmed cell death protein-1 (PD1) inhibition has been associated with low efficacy in the EGFR-mutant setting. Given the potential for synergism with combination checkpoint blockade, we designed a trial to test the activity of combination nivolumab (N)-ipilimumab (NI) in EGFR-mutant NSCLC.

Methods: This is a randomized phase 2 study (NCT03091491) of N versus NI combination in EGFR tyrosine kinase inhibitor (TKI)-resistant NSCLC, with crossover permitted on disease progression.

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Purpose: Chemokines are essential for immune cell trafficking and are considered to have a major impact on the composition of the tumor microenvironment. CX-chemokine receptor 4 (CXCR4) is associated with poor differentiation, metastasis, and prognosis in pancreatic ductal adenocarcinoma (PDAC). This study provides a comprehensive molecular portrait of PDAC according to CXCR4 mRNA expression levels.

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Importance: The recently published ADAURA study has posed a significant dilemma for clinicians in selecting patients for adjuvant osimertinib. Risk factors for recurrence in early-stage epidermal growth factor receptor (EGFR)-positive non-small cell lung cancer (NSCLC) also remain undefined.

Objective: To determine clinicopathologic characteristics and recurrence patterns of resected early-stage EGFR-positive NSCLC, using wildtype EGFR as a comparator cohort, and identify features associated with recurrence.

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Introduction: Circulating tumor cells (CTCs) and cell-free tumor DNA (ctDNA) are tumor components present in circulation. Due to the limited access to both CTC enrichment platforms and ctDNA sequencing in most laboratories, they are rarely analyzed together.

Methods: Concurrent isolation of ctDNA and single CTCs were isolated from lung cancer and breast cancer patients using the combination of size-based and CD45-negative selection method DropCell platform.

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Purpose: Despite the established role of EGFR tyrosine kinase inhibitors (TKIs) in -mutated NSCLC, drug resistance inevitably ensues, with a paucity of treatment options especially in -negative resistance.

Experimental Design: We performed whole-exome and transcriptome analysis of 59 patients with first- and second-generation EGFR TKI-resistant metastatic -mutated NSCLC to characterize and compare molecular alterations mediating resistance in T790M-positive (T790M) and -negative (T790M) disease.

Results: Transcriptomic analysis revealed ubiquitous loss of adenocarcinoma lineage gene expression in T790M tumors, orthogonally validated using multiplex IHC.

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Purpose: Precision oncology has transformed the management of advanced cancers through implementation of advanced molecular profiling technologies to identify increasingly defined subsets of patients and match them to appropriate therapy. We report outcomes of a prospective molecular profiling study in a high-volume Asian tertiary cancer center.

Patients And Methods: Patients with advanced cancer were enrolled onto a prospective protocol for genomic profiling, the Individualized Molecular Profiling for Allocation to Clinical Trials Singapore study, at the National Cancer Center Singapore.

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Background: The efficacy of a combination of nimotuzumab, a humanized monoclonal antibody to the epidermal growth factor receptor, with chemoradiation in locally advanced head and neck squamous cell carcinoma (HNSCC) was evaluated in a phase II study.

Methods: Patients with stage III/IV HNSCC received 3-weekly cisplatin 100 mg/m for three cycles and weekly nimotuzumab 200 mg for 8 weeks concurrently with radiotherapy. Primary endpoint was best overall response (BOR) and secondary endpoint was progression-free survival (PFS).

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Immune checkpoint inhibitors (ICI) have improved survival across tumor types however they cause immune-related toxicities through removal of the inhibition of auto-reactive T cells. In this case review, we present 4 patients with metastatic cancer who developed de-novo neuromuscular side effects of myositis with overlapping seropositive myasthenia gravis after ICI treatment. Declaration: This study was performed in accordance to the ethical standards set by the SingHealth Institutional Review Board, with consent taken from living patients and waiver of consent from deceased patients (CIRB Ref 2019/2485).

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Objective: Non-small cell lung cancer (NSCLC) accounts for 80-90% of all lung cancer cases and is usually associated with a poor prognosis. However, targeted therapy with first and second generation tyrosine kinase inhibitors (TKIs) has so far improved progression-free survival of epidermal growth factor receptor (EGFR) mutant NSCLC patients. Osimertinib, a third generation EGFR TKI has recently shown improved overall survival of 6.

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Purpose: Improved antitumor responses have been observed in patients after combination radiation therapy (RT) and immune checkpoint blockade (ICB). Whether these clinical responses are linked to the host systemic immune system has not been elucidated.

Methods And Materials: In this single-institution prospective observational study, peripheral blood was longitudinally collected from 10 patients with metastatic disease who had responded to anti-PD-1/anti-PD-L1 ICB and received RT (8-50 Gy in 1-5 fractions) upon disease progression at the following timepoints: baseline (pre-RT), 1 to 2 weeks post-RT, and post-ICB (cycle 1) on reintroduction post-RT.

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To assess the cost-effectiveness of pembrolizumab monotherapy compared with standard chemotherapy for the treatment of advanced non-small cell lung cancer (NSCLC) in previously untreated adults who have a high programmed death ligand 1 (PD-L1) tumor proportion score of 50% or greater in Singapore. A partitioned-survival analysis model was developed from a healthcare system's perspective that extrapolated clinical and economic outcomes of first-line pembrolizumab (maximum treatment duration of 2 years) versus platinum doublet chemotherapy over a 10-year time horizon for patients with advanced NSCLC. The model consisted of three health states: alive with no progression, alive with progression, and dead.

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Background: The selective occurrence of hepatotoxicity observed with use of pazopanib may be attributed to its high level of plasma protein binding and low hepatic extraction ratio. The primary objective was to investigate changes in free drug concentration amongst patients with varying albumin concentrations.

Methods: A HPLC-MS/MS method using C18 column (4.

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Article Synopsis
  • - Lung cancer, particularly lung adenocarcinoma (LUAD), shows significant differences in genomic stability between individuals of East Asian ancestry (EAS) and those of European ancestry, with EAS cases exhibiting fewer mutations and copy number alterations.
  • - A new subgroup specific to EAS LUAD was identified, characterized by a simpler genomic profile and increased immune-related gene expression, which could enhance treatment options like immunotherapy.
  • - The research indicates that EAS LUADs may offer better prognostic outcomes and prediction accuracy compared to European LUADs, emphasizing the relevance of ancestry in understanding cancer's molecular landscape.
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Background/aims: The programmed cell death receptor 1 (PD-1) checkpoint inhibitor, nivolumab, has been approved for the treatment of metastatic renal cell carcinoma (RCC). However, the understanding of the expression and distribution of PD ligand 1 (PD-L1) in the tumour immune microenvironment and its prognostic role in an Asian cohort is limited. Our group investigated PD-L1 protein expression in a cohort of Asian patients with RCC of mixed ethnicity, using two commercially available antibody clones.

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Objectives: There is an expanding list of therapeutically relevant biomarkers for non-small cell lung cancer (NSCLC), and molecular profiling at diagnosis is paramount. Tissue attrition in scaling traditional single biomarker assays from small biopsies is an increasingly encountered problem. We sought to compare the performance of targeted next-generation sequencing (NGS) panels with traditional assays and correlate the mutational landscape with PD-L1 status in Singaporean patients.

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Introduction: Several small studies have reviewed the efficacy of abiraterone acetate plus prednisolone (AAP) in clinical practice outside a trial setting. We report the largest cohort study of clinical outcomes in metastatic castrate-resistant prostate cancer (mCRPC) patients treated with AAP in a multicenter multiracial clinical setting.

Methods: A retrospective analysis on mCRPC patients treated at four tertiary hospitals in Singapore from 2012 to 2017 was conducted.

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Objective: Prostate cancers (PCa) in Asian individuals are molecularly distinct from those found in their Caucasian counterparts. There is no risk stratification tool for Asian men with rapid biochemical recurrence (BCR) following radical prostatectomy (RadP). This study aims to assess the detection rate of Ga-prostate-specific membrane antigen-positron emission tomography/computed tomography (PSMA-PET/CT) for diagnosis of clinical recurrence and as a treatment decision making tool in Asian patients with BCR post-RadP.

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Purpose: Mesenchymal epithelial transition factor ( MET) activation has been implicated as an oncogenic driver in epidermal growth factor receptor ( EGFR)-mutant non-small-cell lung cancer (NSCLC) and can mediate primary and secondary resistance to EGFR tyrosine kinase inhibitors (TKI). High copy number thresholds have been suggested to enrich for response to MET inhibitors. We examined the clinical relevance of MET copy number gain (CNG) in the setting of treatment-naive metastatic EGFR-mutant-positive NSCLC.

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Background: Afatinib is an oral irreversible epidermal growth factor receptor (EGFR) tyrosine-kinase inhibitor (TKI) indicated in first-line treatment of advanced EGFR-mutant (EGFRm+) non-small cell lung cancer (NSCLC). Dose dependent side effects can limit drug exposure, which may impact on extracranial and central nervous system (CNS) disease control.

Methods: We performed a retrospective study of 125 patients diagnosed with advanced EGFRm+ NSCLC treated with first-line afatinib at a tertiary Asian cancer center, exploring clinicopathological factors that may influence survival outcomes.

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Various forms of immunotherapy, such as checkpoint blockade immunotherapy, are proving to be effective at restoring T cell-mediated immune responses that can lead to marked and sustained clinical responses, but only in some patients and cancer types. Patients and tumours may respond unpredictably to immunotherapy partly owing to heterogeneity of the immune composition and phenotypic profiles of tumour-infiltrating lymphocytes (TILs) within individual tumours and between patients. Although there is evidence that tumour-mutation-derived neoantigen-specific T cells play a role in tumour control, in most cases the antigen specificities of phenotypically diverse tumour-infiltrating T cells are largely unknown.

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Purpose: Since few studies have investigated whether the Distress Thermometer (DT) in Asian adolescent and young adult (AYA) cancer patients (between 15 and 39 years), we investigated the appropriateness of the DT as a screening tool for psychological symptom burden in these AYA patients and to evaluate AYA patients' distress across a trajectory of three time points longitudinally over a 6-month period.

Methods: This was a prospective, longitudinal study. Recruited Asian AYA patients were diagnosed with lymphomas, sarcomas, primary brain malignancies, or germ cell tumors.

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