Catherine Poh


Relevant Degree Programs


Graduate Student Supervision

Master's Student Supervision (2010 - 2018)
Human papillomavirus and oropharyngeal cancer in British Columbia (2018)

Oropharyngeal squamous cell carcinoma (OpSCC) patients have improved survival when tested positive for high-risk human papillomavirus (HR-HPV). However, tissue assessment of HPV status is currently not standardized and additional factors may influence survival among HPV-positive patients. The main objectives were to evaluate HPV detection methods and to identify possible factors that impact survival of OpSCC patients in British Columbia.We retrospectively analyzed 972 primary OpSCC patients diagnosed between 2000-2008 and referred to the BC Cancer Agency for treatment with curative intents of radiotherapy with or without concurrent chemotherapy. Patient charts were reviewed and collected information for demographics, smoking history, clinical assessments, treatment received, and outcomes. We analyzed two cohorts of Study Cohort, 244 cases with enough formalin-fixed, paraffin-embedded (FFPE) tissues for experiment, and General Cohort, 728 cases without tissues available. Experimental procedures included in situ hybridization (ISH) to detect DNA and RNA HPV and immunohistochemistry (IHC) to detect p16, p53, the retinoblastoma protein (pRB), cyclin D1, and Ki67. We used polymerase chain reaction (PCR) to detect type-specific HPV from cases with enough FFPE tissues for DNA extraction (n=41). Cox proportional hazard (Cox-PH) and Kaplan-Meier (KM) survival analysis were conducted to identify potential clinical and biological factors impacting on 5-year overall survival (OS), disease-specific survival (DSS), and development of loco-regional recurrence (LRR). The incidence rates of males increased from 3.2 to 7.6 per 100,000 whereas females declined from 1.1 to 0.8 per 100,000. The Study Cohort was relatively representative of the General Cohort. The Study Cohort of patients classified as ever-smokers, had tumours staged at T3/4, and received radiotherapy only had poorer 5-year OS, DSS, and LRR (p
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Nodal Disease Burden of Oral Cancer in British Columbia and a Novel Approach for Risk Assessment (2016)

For patients of oral squamous cell carcinoma (OSCC), tumour spread to regional lymph nodes reduces survival by half. On the account of this widely demonstrated fact, prophylactic neck treatment has been advocated for clinically node negative (cN0) necks of which the risk of nodal disease is considerably high. However, there is a lack of sensitive and specific marker to determine such risk and benefits of prophylactic treatment await confirmation. The first part of this thesis presents a population-based retrospective review on OSCC in British Columbia. The incidence of regional failure (RF) in early-stage, cN0 patients was 28%, with median time of only 10 months after local excision. This group of patients needed to be identified and treated at earliest time possible. Tumour depth of invasion (DOI) was significantly associated with RF (P=0.01). However, it has low accuracy in predicting nodal disease with AUC of 63%. Moreover, assessment of performance for 4mm cut-off of DOI showed 55% sensitivity and 68% specificity. Furthermore, we demonstrated that using DOI as an indicator of neck treatment resulted in 25% under-treated occult metastasis and 55% over-treated necks. Thus, we concluded that, at least for BC population, conventional histological attributes of tumour cannot predict RF and we need a new marker for risk assessment. The second part presents a pilot study exploring a novel approach of risk assessment by utilizing Quantitative Tissue Pathology (QTP) on tumour nests. We were able to quantitate and evaluate 120 features describing nuclear phenotypes of tumour cell nuclei and tissue architectures of tumour nests. Compared to node-negative (N0) group, cell nuclei of the node positive (N+) group had higher fractions of heterochromatin regions. Also, the combination of two features, which describe chromatin condensation, from the outermost two layers of tumour nests had performance of AUC 94%, sensitivity of 100% and specificity of 75% in discriminating N0 and N+ group. QTP may be a potential proxy for predicting the metastatic risk of OSCC. Further investigation on potential biomarkers in risk assessment for nodal disease of early-stage OSCC patients is warranted to provide precision management to improve mortality and reduce morbidity.

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Characterizing the oral health of low-income adults in Vancouver's Downtown Eastside (2014)

Low-income residents from the Vancouver’s Downtown Eastside (DTES) are known to be medically underserved, but little is known about their oral health (OH) status. The objectives of this study are to: 1) determine OH characteristics (clinical and subjective) of low-income adults in this community; 2) identify explanatory factors for their OH status.Material and Methods: Screening clinics were set up in the DTES. Eligibility criteria were adults 19 years of age or over and residence in the DTES for the preceding 3 months. Data were collected through questionnaires and clinical examinations.Results: Among the 356 screened participants, most were males, middle-aged, less educated, and living with low-income (≤$20,000/year). Alcohol and tobacco consumption was common. About 80% had dental coverage, mostly publicly funded benefits (94%). Fifty (14%) participants were edentulous. Dentate participants (n=306), on average, had 3.8 decayed (Dt), 8.6 missing (Mt), 4.9 filled (Ft), 17.2 DMF teeth, and a care index (CI) of 41.5%. Many (86%) perceived a dental need. Although more participants with dental insurance had a dental visit within the past 12 months, there were no differences in OH indices between those with or without dental insurance. After adjusting gender and recruitment site, social (barriers to care & length of DTES residence), behavioural (brush/floss), and personal (HCV/methadone) factors were identifiable explanatory factors for the CI level. Conclusion: DTES low-income have poor oral health status and many perceive a need for dental care. We identified several factors that may affect their levels of dental care; however, this community may inherited more complicated social issues. Further investigations to truly understand their challenges and needs are required for a better oral health promotion in this community.

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