Surgery (St Vincent's) - Theses
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ItemProfiling desmoid tumours and exploring new strategies to prevent and treat desmoid tumours in familial adenomatous polyposis using a novel mouse model( 2018)Desmoid tumour is a benign growth that causes morbidity and mortality from local enlargement. Desmoids are thought to result from dysfunction in WNT signalling. Trauma, including that from surgical intervention, is implicated in the pathogenesis of desmoid tumour, with desmoids often occurring at surgical sites. Patients with familial adenomatous polyposis (FAP) possess a germline mutation in the APC gene on chromosome 5, resulting in numerous colorectal adenomas that inevitably develop into colorectal carcinoma. Patients with FAP undergo prophylactic colectomy to manage risk of future carcinoma. The germline mutation in APC, combined with surgical trauma from prophylactic colectomy, place patients with FAP at a significant risk of future desmoid tumour development. Desmoid tumour is the largest cause of mortality for patients with FAP following prophylactic colectomy. There is controversy regarding the utility of laparoscopic prophylactic colectomy in FAP, with some series suggesting that laparoscopic surgery results in a higher risk of future desmoid tumour. Desmoid tumours in FAP patients occur in the mesentery and abdominal wall. Management options are limited due to the precarious location, often in close relationship to the mesenteric vasculature. Desmoid tumours in this cohort pose significant clinical management challenges, with high recurrence rates after surgical excision, and no consensus on best medical management. Since desmoid tumours are rare tumours, a pre-clinical model would facilitate research in this area. This research thesis describes the development of a novel murine model for abdominal desmoid tumour that occurs in FAP. The Apcmin/+:p53-/- mouse develops numerous abdominal wall desmoid tumours. This model has been validated with histopathology and immunohistochemistry, and has facilitated the development of desmoid tumour cell lines, and xenograft studies in this area. The impact of surgical approach on future desmoid risk was investigated using the Apcmin/+:p53-/- mouse. Mice were subjected to laparotomy or laparoscopy and were then observed until they reached ethical endpoints, at which time an assessment of desmoid tumour burden was made. In the Apcmin/+:p53-/- mouse model, surgical approach had no impact on survival or the number of macroscopically identifiable desmoid tumours. Furthermore, the use of humidification/warming device for open and laparoscopic surgery was trialed and found to have no impact on survival or desmoid tumour burden. This research has also investigated the genomic landscape of human abdominal and abdominal wall desmoid tumours through RNA sequencing and immunohistochemistry. This study has identified that abdominal desmoid tumours share genomic similarity to wild-type gastrointestinal stromal tumours (negative for CD117 and PDGFRα). Sequencing identified a number of pathways (Such as VEGF, EGF and mTOR) involved in desmoid tumour formation that could be targets for therapy.
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ItemPrediction and prognosis in anal cancer: developing models to improve patient outcome( 2017)Anal squamous cell carcinoma is a human papilloma virus–related disease for which definitive treatment comprises chemoradiotherapy that has not changed substantially for forty years. Few advances in treatment have been made since then, especially for those patients who develop disease relapse and for whom no surgical options exist. Predicting responses in patients for whom conventional treatment will fail remains elusive and is a significant clinical problem. As anal cancer is reasonably described as a rare cancer, innovative approaches are required to address this pressing clinical issue as large clinical trials are exceptionally challenging and are unlikely to be undertaken. This thesis describes a range of research strategies to identify potential avenues to predict and improve patient responses to existing and novel therapies. It comprises a combination of clinical and translational research. Using our institutional database I have assessed the utility of post-treatment imaging with FDG-PET as it may serve as a means of early detection of poor response to treatment. I found that a complete metabolic response on post-treatment PET scan was predictive of overall survival and disease-free survival. The database, which spans a thirty year period, was also interrogated to explore patterns of treatment failure, subsequent salvage treatment and outcomes. I found that multiple treatment modalities have been utilised to treat patients with persistent or recurrent disease, with satisfactory survival benefit in carefully selected patients. I also evaluated the literature that investigated the molecular biology of anal cancer finding that no clinically valuable biomarkers have emerged. Some suggestions have been reported that regulators of apoptosis, including survivin, and agents targeting the PI3K/AKT pathway, might offer opportunities for targeted therapy. Additionally, antibody therapy targeting epidermal growth factor receptor may prove efficacious although the safety profile in combination with standard chemoradiotherapy has proven to be suboptimal. In the laboratory, next generation RNA sequencing was utilised in eleven anal SCC patient samples. Through stratification of the tumours into clinically relevant groups and Bioinformatic analysis, eight genes with differential expression were chosen for further validation. One of these genes was identified as a novel target which could ultimately lead to expanding therapeutic options in anal cancer management. Due to a lack of pre-clinical models, including cell lines and mouse models for testing new therapies, I developed a new anal cancer model based upon patient-derived tumour xenografts. I used this model in a pilot experiment to assess the novel drug target identified by RNA-seq. The outcomes were promising with stand-alone efficacy of the novel drug observed with statistical significance, while also validating the feasibility of using xenografts for anal SCC. This thesis builds upon the clinical experience of decades of management of patients with anal cancer identifying both clinical and laboratory approaches to advance assessment and identify novel treatment possibilities for this group of patients.
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ItemSelection and management of men for active surveillance in low risk prostate cancer( 2016)Aims: To investigate: 1. Selection of men for active surveillance of prostate cancer a. Validation of risk calculators b. Suitability for inclusion of Gleason 3+4 disease. 2. Performance of prostate biopsy during AS a. Differences in quality of diagnostic biopsy between academic and referral centres. b. Optimization of biopsy templates c. Examination of prognostic indicators for disease progression Methods: Data were obtained from several difference sources: • Men suitable for AS on prostate biopsy but undergoing upfront radical prostatectomy were pooled from 3 international academic institutions in Cambridge (UK), Toronto (Canada) and Melbourne (Australia). • Prospectively maintained AS prostate cancer database at Princess Margaret Cancer Centre (PMCC) (1997-2012). Analyses performed: • Four risk calculators were assessed for their ability to predict different definitions of insignificant prostate cancer by area under the curve (AUC) of receiver operating characteristic curves and Brier scores for discrimination, calibration curves and decision curve analysis. • Men with biopsy Gleason 3+4 disease, suitable according to modified Royal Marsden, Sunnybrook Toronto and PRIAS selection criteria, were assessed for presence of adverse pathology at upfront radical prostatectomy. • Patients on AS at a tertiary referral centre (PMCC) were dichotomized depending on where their diagnostic biopsy was performed (interval versus external). Multivariate logistic regression was performed to examine for predictors of re-classification at the second, or confirmatory, biopsy. • Mapping of all patients with pathological progression at PMCC for location of disease progression enabled comparison of hypothetical biopsy templates (sextant and standard extended) to the institutional template used. • Men on AS at PMCC were evaluated for presence of disease progression at serial biopsy in the prostate transition zone (TZ). Multivariate Cox proportional hazards regression evaluated predictors of TZ progression. • At PMCC, men were dichotomized based on presence of cancer at their confirmatory biopsy. Pathological progression was investigated using a Cox proportional hazards regression model. Results: • All 4 models predicting presence of insignificant prostate cancer had weak discrimination at best (AUC 0.618-0.664). • Presence of Gleason 3+4 at biopsy, compared to 3+3 disease, increases risk of adverse pathology at radical prostatectomy if modified Sunnybrook Toronto criteria are used (19% versus 33%, p≤0.001). Using a stricter protocol such as PRIAS, there was no statistical difference between the groups. • External biopsy predicted both grade related re-classification (OR 4.14, C.I. 2.01-8.54, p<0.001) and volume related re-classification (OR 3.43, C.I. 1.87-6.25, p<0.001). • Sextant and standard extended biopsy templates were inferior to the institutional biopsy template in detecting presence of cancer (84% and 99% versus 100%), and pathological progression (47.9% and 81.9% versus 100%). • At each subsequent biopsy during AS, 2.7-6.7% of men had disease progression only in the TZ which would not have been detected if TZ biopsy was not performed. Predictors of TZ progression were maximum % single core (HR 1.99, C.I. 1.30-3.04, p=0.002), and MRI reporting cancer (HR 3.19, C.I. 1.23-8.27, p=0.02). • Men with no cancer at confirmatory biopsy were less likely to have pathological progression (HR 0.47, CI 0.29-0.77, p=0.003). Sub-analysis showed this was predictive of volume-related progression (HR=0.36, CI 0.20-0.62, p=0.0006) and not grade-related progression. Conclusions: • Utilization of models predicting suitability for AS should be used with caution as external validation in our cohort was weak. • If considering biopsy Gleason 3+4 disease for AS, a stricter protocol such as PRIAS must be utilized. • At PMCC, patients who had their initial diagnostic prostate biopsy for AS done externally, were more likely to have worse pathological features and re-classify on the second biopsy. • For men on AS, sextant and standard extended biopsy are less likely to detect prostate cancer or disease progression than the template used at PMCC. • TZ biopsy should be considered for all men having serial biopsy on AS, in particular those with high % core involvement or positive MRI findings. • Absence of cancer on B2 is associated with a significantly decreased risk of volume-related but not grade-related progression.
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ItemThromboembolism and neoadjuvant chemoradiation for rectal cancer( 2015)Thromboembolism (TE) is one of the leading causes of morbidity and mortality in cancer, is an independent predictor of reduced survival, and the overall rate of TE in cancer patients is increasing. Assessing the TE risk of an individual patient at a given time point and the benefit of thromboprophylaxis (TP) can be complex, involving widely variable TE rates according to tumour related factors (such as cancer subtype and disease stage), as well as patient and treatment related factors. Some, such as surgery and hospitalisation are well recognised and appropriately targeted with mechanical and pharmacological thromboprophylaxis (TP) strategies backed by Level I evidence. There is evidence that TP after hospital discharge following surgery (extended TP) is also beneficial. Recently, subgroups such as those with metastases receiving palliative chemotherapy have been shown to be at equally high risk, and also benefit from primary TP. Both chemotherapy and central venous access devices (CVAD) have been shown to be independently associated with development of TE. In addition, early studies examining neoadjuvant radiotherapy (nRT) in rectal cancer reported higher rates of TE however this finding was not repeated in subsequent studies using modern radiotherapy techniques. Extrapolating these findings raises the question of TE risk and the potential benefit of TP during neoadjuvant radiotherapy (nRT) or chemoradiotherapy (nCRT) for rectal cancer. This thesis explores the current evidence and contemporary guidelines concerning TE risk during nCRT, demonstrating considerable uncertainty and a lack of robust data. Randomised trials examining nCRT in rectal cancer are systematically reviewed to determine rates of TE, demonstrating a failure to capture TE events due to inadequate complication reporting frameworks. Existing attitudes and prescribing practices of specialist rectal cancer surgeons are surveyed, as well as barriers to TP prescribing. Issues of equipoise, ownership and logistical problems with outpatient TP prescribing were identified. The historical TE rate and epidemiology over a prolonged follow-up period in rectal cancer patients, as well as the relationship to nCRT is examined at both Peter MacCallum Cancer Centre in Australia and the Cleveland Clinic in the United States. These studies demonstrated that most TE events occurred in patients with metastatic disease receiving ambulatory palliative chemotherapy, and that the overall rate of TE in patients treated with nCRT was not elevated over those patients who had surgery alone. Finally, a prospective study of thrombogenic biomarkers in patients with rectal cancer was undertaken demonstrating significant coagulation abnormalities in colorectal cancer patients at baseline, but no major alteration during neoadjuvant chemoradiation. Marked and prolonged procoagluant abnormalities were demonstrated in the post-operative phase. Thus the current literature, attitudes of treating clinicians, historical rates, as well as candidate biomarkers for prospective TE risk were examined in nCRT for rectal cancer for the first time, identifying future potential research questions aimed at reducing this common complication of cancer care.