Machine Learning for Prostate Histopathology Assessment

Pathology reporting on radical prostatectomy (RP) specimens is essential to post-surgery patient care. However, current pathology interpretation of RP sections is typically qualitative and subject to intra- and inter-observer variability, which challenges quantitative and repeatable reporting of lesion grade, size, location, and spread. Therefore, we developed and validated a software platform that can automatically detect and grade cancerous regions on whole slide images (WSIs) of whole-mount RP sections to support quantitative and visual reporting. Our study used hæmatoxylin- and eosin-stained WSIs from 299 whole-mount RP sections from 71 patients, comprising 1.2 million 480μm×480μm regions-of-interest (ROIs) covering benign and cancerous tissues which contain all clinically relevant grade groups. Each cancerous region was annotated and graded by an expert genitourinary pathologist. We used a machine learning approach with 7 different classifiers (3 non-deep learning and 4 deep learning) to classify: 1) each ROI as cancerous vs. non-cancerous, and 2) each cancerous ROI as high- vs. low-grade. Since recent studies found some subtypes beyond Gleason grade to have independent prognostic value, we also used one deep learning method to classify each cancerous ROI from 87 RP sections of 25 patients as each of eight subtypes to support further clinical pathology research on this topic. We cross-validated each system against the expert annotations. To compensate for the staining variability across different WSIs from different patients, we computed the tissue component map (TCM) using our proposed adaptive thresholding algorithm to label nucleus pixels, global thresholding to label lumen pixels, and assigning the rest as stroma/other. Fine-tuning AlexNet with ROIs of the TCM yielded the best results for prostate cancer (PCa) detection and grading, with areas under the receiver operating characteristic curve (AUCs) of 0.98 and 0.93, respectively, followed by fine-tuned AlexNet with ROIs of the raw image. For subtype grading, fine-tuning AlexNet with ROIs of the raw image yielded AUCs ≥ 0.7 for seven of eight subtypes. To conclude, deep learning approaches outperformed non-deep learning approaches for PCa detection and grading. The TCMs provided the primary cues for PCa detection and grading. Machine learning can be used for subtype grading beyond the Gleason grading system

Exploration of a xenograft model of human prostate cancer to predict patient treatment response

For several years, docetaxel was the only treatment to improve survival of patients with metastatic prostate cancer. There are now many novel agents available but the optimal sequence of treatments remains undefined. The emergence of prostate cancer stem cells has brought a new way to elucidate the molecular mechanisms behind treatment failure and recurrence. Traditionally cell lines have been used in preclinical studies but recently ‘near patient’ derived xenografts (PDX), have been suggested to be a better way to investigate new therapies and investigate pathways in metastatic spread. First we used a subcutaneous and an orthotopic PDX model to determine which is most feasible in looking at the differences in the expression of basal and luminal cell markers. We then looked at the effect of docetaxel on hormone naïve and castrate resistant PDXs specifically measuring changes in the numbers of basal and luminal cells determining docetaxel resistance. Finally we tried labelling and fluorescent cell sorting PDX cells to track metastatic spread and monitor chemotherapy effects.The mouse prostate microenvironment did not drastically change cellular phenotypes, allowing us to use the simpler subcutaneous method to assess chemotherapy effects on PDX. In fact the subcutaneous xenografts retained basal and luminal cells maintaining the clinical heterogeneity present in prostate cancers. In the docetaxel studies, alteration in AR expression and high levels of basal-like cells from the outset appeared to confer resistance. Although docetaxel had an overall detrimental effect, there was a typical decrease in the number of basal cells in both hormone naïve and resistant tumours. No trends were seen in the luminal populations. Side effects affecting continuation of treatment wereevident. Lentiviral transduction was successful in PC3 cells where they maintained high levels of fluorescent (RFP) reporter expression. Transduction of PDX cells proved more challenging and requires further optimisation.In the evolving area of new prostate cancer treatments, docetaxel chemotherapy continues to play an important role and could be given in hormone naïve cancers. This can also increase the chances of benefitting from the whole variety of new drugs. However, not all tumours are sensitive and resistance mechanisms remain unclear

Local object patterns for tissue image representation and cancer classification

Ankara : The Department of Computer Engineering and the Graduate School of Engineering and Science of Bilkent Univ., 2013.Thesis (Master's) -- Bilkent University, 2013.Includes bibliographical refences.Histopathological examination of a tissue is the routine practice for diagnosis and grading of cancer. However, this examination is subjective since it requires visual interpretation of a pathologist, which mainly depends on his/her experience and expertise. In order to minimize the subjectivity level, it has been proposed to use automated cancer diagnosis and grading systems that represent a tissue image with quantitative features and use these features for classifying and grading the tissue. In this thesis, we present a new approach for effective representation and classification of histopathological tissue images. In this approach, we propose to decompose a tissue image into its histological components and introduce a set of new texture descriptors, which we call local object patterns, on these components to model their composition within a tissue. We define these descriptors using the idea of local binary patterns. However, we define our local object pattern descriptors at the component-level to quantify a component, as opposed to pixel-level local binary patterns, which quantify a pixel by constructing a binary string based on relative intensities of its neighbors. To this end, we specify neighborhoods with different locality ranges and encode spatial arrangements of the components within the specified local neighborhoods by generating strings. We then extract our texture descriptors from these strings to characterize histological components and construct the bag-of-words representation of an image from the characterized components. In this thesis, we use two approaches for the selection of the components: The first approach uses all components to construct a bag-ofwords representation whereas the second one uses graph walking to select multiple subsets of the components and constructs multiple bag-of-words representations from these subsets. Working with microscopic images of histopathological colon tissues, our experiments show that the proposed component-level texture descriptors lead to higher classification accuracies than the previous textural approaches.Olgun, GüldenM.S

Domain Generalization in Computational Pathology: Survey and Guidelines

Deep learning models have exhibited exceptional effectiveness in Computational Pathology (CPath) by tackling intricate tasks across an array of histology image analysis applications. Nevertheless, the presence of out-of-distribution data (stemming from a multitude of sources such as disparate imaging devices and diverse tissue preparation methods) can cause \emph{domain shift} (DS). DS decreases the generalization of trained models to unseen datasets with slightly different data distributions, prompting the need for innovative \emph{domain generalization} (DG) solutions. Recognizing the potential of DG methods to significantly influence diagnostic and prognostic models in cancer studies and clinical practice, we present this survey along with guidelines on achieving DG in CPath. We rigorously define various DS types, systematically review and categorize existing DG approaches and resources in CPath, and provide insights into their advantages, limitations, and applicability. We also conduct thorough benchmarking experiments with 28 cutting-edge DG algorithms to address a complex DG problem. Our findings suggest that careful experiment design and CPath-specific Stain Augmentation technique can be very effective. However, there is no one-size-fits-all solution for DG in CPath. Therefore, we establish clear guidelines for detecting and managing DS depending on different scenarios. While most of the concepts, guidelines, and recommendations are given for applications in CPath, we believe that they are applicable to most medical image analysis tasks as well.Comment: Extended Versio

A Survey on Deep Learning in Medical Image Analysis

Deep learning algorithms, in particular convolutional networks, have rapidly become a methodology of choice for analyzing medical images. This paper reviews the major deep learning concepts pertinent to medical image analysis and summarizes over 300 contributions to the field, most of which appeared in the last year. We survey the use of deep learning for image classification, object detection, segmentation, registration, and other tasks and provide concise overviews of studies per application area. Open challenges and directions for future research are discussed.Comment: Revised survey includes expanded discussion section and reworked introductory section on common deep architectures. Added missed papers from before Feb 1st 201

Targeting the splice factor kinase CLK1 in prostate cancer cells

Prostate cancer is the most rampant diagnosed cancer and the second leading cause of cancer related death in men between middle age and old age. There is a need to identify the molecular genetic processes that underpin prostate cancer and to search for new treatments. Alternative splicing affects over 94% of human genes and aberrant splicing is implicated in prostate cancer. Splicing is regulated by splice factors and protein kinases (the latter including SRPK1 and CLK1). The CLK1 protein kinase specifically regulates alternative splicing by phosphorylation of SR proteins within the nucleus, particularly in nuclear speckles (splice factor storage sites). CLK1 is also found to be overexpressed during malignant prostate cell transformation-; therefore targeting the splice factor kinase CLK1 by its specific chemical inhibitor (TG003) could be therapeutically useful. We confirm that CLK1 expression is itself regulated through alternative splicing: skipping of exon 4 or retention of intron 4 results in truncated, inactive CLK1. The aims of this project are to study CLK1 alternative splicing and to explore the effects of targeting the splice factor kinase CLK1 in prostate cancer.Prostate cancer cell lines (androgen independent PC3 and DU145 cells) were treated independently for 24, 48 and 72hrs with varying concentrations (10nM -100μM) of thebenzothiazole compound (TG003) a specific inhibitor of CLK1. Results suggest that chemical inhibition of CLK1 with TG003 treatment suppressed growth and induced apoptosis in prostate cancer cell lines, as well as causing decreased cell migration and invasion. Similar effects were observed when CLK1 expression was reduced with an siRNA. There was also increased E-cadherin expression with TG003 treatment; incontrast, vimentin expression was reduced suggesting reversal of endothelialmesenchymal transition following TG003 treatment. RT-PCR analysis revealed that TG003 treatment altered CLK1’s own splicing by altering exon 4 skipping rates in a iv dose dependent manner, suggesting that a feedback loop mechanism contributes to the regulation of CLK1 expression. In vivo mouse work with PC3 cell line xenograftsshowed a highly significant reduction in tumour growth and volume following intraperitoneal TG003 administration (10 and 50μM). In conclusion, the findings presented in this thesis suggest that targeting CLK1 may bring considerable anticancer benefits

Dissecting the Role of microRNAs in the Radiation Response of Human Prostate Cancer

Radiotherapy is one of the gold standard treatments for non-metastatic prostate cancer (PCa), although development of radioresistance limits its effectiveness. Mounting evidence supports the ability of microRNAs to interfere with different radioresistance-associated pathways, suggesting their potential as radiosensitizers. To identify miRNAs likely to be involved in influencing PCa radiation response, we first performed miRNA profiling analysis of PCa cell lines exposed to photon irradiation. Based on their modulation upon radiation exposure, and their role in regulating pathways associated with radiation response we singled-out and characterized miR-23a-3p and miR-24-3p as potential radiosensitizer molecules in PCa, unrevealing a central role of miR- 23a-3p-IL-6 axis. In the framework of miRNAs downregulated in PCa and known to regulate genes relevant to radiation, miR-875-5p and miR-205 were identified. Reconstitution of miR-875-5p, the expression of which directly correlates with that of E-cadherin, was able to enhance radiation response in PCa cell lines and xenografts through EGFR direct targeting. Consistent with the established role of EGFR in sustaining epithelial-to-mesenchymal transition (EMT) and promoting DNA repair following radiation, we found that miR-875-5p reconstitution in PCa cells counteracted EMT and impaired DNA lesion clearance, mainly via impairment of EGFR-ZEB1 axis. Restoration of miR-205 was able to significantly enhance PCa sensitivity to radiation, in both cell and animal models. Specifically, we found that miR-205 radiosensitizing effect was imputable to the downregulation of PKC-ε. Consistent with PKC-ε well-established role in DNA damage repair, we found that pEGFR and, consequently, pDNA-PK levels were significantly reduced by miR-205 reconstitution, thus suggesting that miR-205 enhances PCa radiation response via disruption of PKC-ε−EGFR−DNA-PK axis. Overall, the results of this project support the clinical interest in developing novel therapeutic approaches based on miRNA reconstitution (miR-23a-3p, miR-875-5p and miR-205) to enhance PCa response to radiotherapy

Prostate cancer biochemical recurrence prediction using bpMRI radiomics, clinical and histopathological data

Tese de mestrado integrado em Engenharia Biomédica e Biofísica (Sinais e Imagens Médicas), Universidade de Lisboa, Faculdade de Ciências, 2021O cancro da próstata é a segunda doença oncológica mais frequente nos homens, sendo frequentemente tratado com remoção cirúrgica total do órgão, denominada prostatectomia radical. Apesar dos avanços no diagnóstico e da evolução das terapias cirúrgicas, 20–35% dos candidatos a prostatectomia radical com intuito curativo sofrem de recidiva bioquímica, uma condição que representa o insucesso do tratamento inicial e também o primeiro sinal de progressão da doença. Em particular, dois terços dos casos de recidiva bioquímica ocorrem dentro de um período de dois anos. Ocorrendo cedo, este estado implica uma maior agressividade biológica da doença e um pior prognóstico, uma vez que pode dever-se `a presença de doença oculta, localmente avançada ou metastática. Apesar de o prognóstico devido ao desenvolvimento de recidiva bioquímica variar, em geral está associado a um risco acrescido de desenvolvimento de doença metastática e de mortalidade específica por cancro da próstata, representando assim uma importante preocupação clínica após terapia definitiva. Contudo, os modelos preditivos de recidiva bioquímica actuais não só falham na explicação da variabilidade dos resultados pós-cirúrgicos, como não têm habilidade para intervir cedo no processo de decisão de tratamento, uma vez que dependem de informação provinda da avaliação histopatológica da peça cirúrgica da prostatectomia ou da biópsia. Actualmente, o exame padrão para diagnóstico e para estadiamento do cancro da próstata é a ressonância magnética multiparamétrica, e as características provindas da avaliação dessas imagens têm mostrado potencial na caracterização do(s) tumor(es) e para predição de recidiva bioquímica. “Radiomics”, a recente metodologia aplicada à análise quantitativa de imagens médicas tem mostrado ter capacidade de quantificar objectivamente a heterogeneidade macroscópica de tecidos biológicos como tumores. Esta heterogeneidade detectada tem vindo a sugerir associação a heterogeneidade genómica que, por sua vez, tem demonstrado correlação com resistência a tratamento e propensão metastática. Porém, o potencial da análise radiómica das imagens de ressonância magnética (MRI) multiparamétrica da próstata para previsão de recidiva bioquímica pós-prostatectomia radical ainda não foi totalmente aprofundado. Esta dissertação propôs explorar o potencial da análise radiómica aplicada a imagens pré-cirúrgicas de ressonância magnética biparamétrica da próstata para previsão de recidiva bioquímica, no período de dois anos após prostatectomia radical. Este potencial foi avaliado através de modelos predictivos com base em dados radiómicos e parâmetros clínico-histopatológicos comummente adquiridos em três fases clínicas: pré-biópsia, pré- e pós-cirúrgica. 93 pacientes, de um total de 250, foram eleitos para este estudo retrospectivo, dos quais 20 verificaram recidiva bioquímica. 33 parâmetros clínico-histopatológicos foram recolhidos e 2715 variáveis radiómicas baseadas em intensidade, forma e textura, foram extraídas de todo o volume da próstata caracterizado em imagens originais e filtradas de ressonância magnética biparamétrica, nomeadamente, ponderadas em T2, ponderadas em Difusão, e mapas de coeficiente de difusão aparente (ADC). Embora os pacientes elegíveis tenham sido examinados na mesma instituição, as características do conjunto de imagens eram heterogéneas, sendo necessário aplicar vários passos de processamento para possibilitar uma comparação mais justa. Foi feita correção do campo tendencial (do inglês, “bias”) e segmentação manual das imagens T2, registo tanto para transposição das delineações do volume de interesse entre as várias modalidades imagiológicas como para correção de movimento, cálculo de mapas ADC, regularização do campo de visão, quantização personalizada em tons cinza e reamostragem. Tendo os dados recolhidos uma alta dimensionalidade (número de variáveis maior que o número de observações), foi escolhida a regressão logística com penalização L1 (LASSO) para resolver o problema de classificação. O uso da penalização aliada à regressão logística, um método simples e commumente usado em estudos de classificação, permite impedir o sobreajuste provável neste cenário de alta dimensionalidade. Além do popular LASSO, recorremos também ao algoritmo Priority-LASSO, um método recente para lidar com dados “ómicos” e desenvolvido com base no LASSO. O Priority-LASSO tem como princípio a definição da hierarquia ou prioridade das variáveis de estudo, através do agrupamento dessas mesmas variáveis em blocos sequenciais. Neste trabalho explorámos duas maneiras de agrupar as variáveis (Clínico-histopatológicas vs. Radiómicas e Clínico-histopatológicas vs. T2 vs. Difusão vs. ADC). Além disso, quisemos perceber qual o impacto da ordem destes mesmos blocos no desempenho do modelo. Para tal, testámos todas as permutações de blocos possíveis (2 e 24, respectivamente) em cada um dos casos. Assim, uma estrutura de aprendizagem automática, composta por métodos de classificação, validação-cruzada k-fold estratificada e repetida, e análises estatísticas, foi desenvolvida para identificar os melhores classificadores, dentro um conjunto de configura¸c˜oes testado para cada um dos três cenários clínicos simulados. Os algoritmos de regressão logística penalizada com LASSO e o Priority-LASSO efectuaram conjuntamente a seleção de características e o ajuste de modelos. Os modelos foram desenvolvidos de forma a optimizar o n´umero de casos positivos de recidiva bioquímica através da maximização das métricas área sob a curva (AUC) e medida-F (Fmax), derivadas da análise de curva característica de operação do receptor (ROC). Além da comparação das implementações Priority-LASSO com o caso em que não houve agrupamento de variáveis (isto é, LASSO), foram também comparados dois métodos de normalização de imagens com base no desempenho dos modelos (avaliado por Fmax). Um dos métodos tinha em conta o sinal de intensidade proveniente da próstata e de tecidos imediatamente circundantes, e outro apenas da próstata. Paralelamente, também o efeito do método de amostragem SMOTE, que permite equilibrar o número de casos positivos e negativos durante o processo de aprendizagem do algoritmo, foi avaliado no desempenho dos modelos. Com este método, gerámos casos sintéticos para a classe positiva (classe minoritária) para recidiva bioquímica, a partir dos casos já existentes. O modelo de regressão logística com Priority-LASSO com a sequência de blocos de variáveis Clínico-histopatológicas, T2, Difusão, ADC e com restrição de esparsidade de cada bloco com o parâmetro pmax = (1,7,0,1), foi seleccionada como a melhor configuração em cada um dos cenários clínicos testados, superando os modelos de regressão logística LASSO. Durante o desenvolvimento dos modelos, e em todos os cenários clínicos, os modelos com melhor desempenho obtiveram bons valor médios de Fmax (mínimo–máximo: 0.702–0.754 e 0.910–0.925 para classe positiva e negativa de recidiva bioquímica, respectivamente). Contudo, na validação final com um conjunto de dados independentes, os modelos obtiveram valores Fmax muito baixos para a classe positiva (0.297–0.400), revelando um sobreajuste, apesar do uso de métodos de penalização. Também se verificou grande instabilidade nos atributos seleccionados. Contudo, os modelos obtiveram razoáveis valores de medida-F (0.779–0.833) e de Precisão (0.821–0.873) para a classe de recidiva bioquímica negativa durante as fases de treino e de validação, pelo que estes modelos poderão ter valor a ser explorado. Os modelos pré-biópsia tiveram desempenho inferior no treino, mas sofreram menos de sobreajuste. Os classificadores pré-operatórios foram excessivamente optimistas, e os modelos pós-operatórios foram os melhores a detectar correctamente casos negativos de recidiva bioquímica. Outros resultados observados incluem a superioridade no desempenho dos modelos baseados em imagens que usaram o método de normalização realizado apenas com o volume da próstata, e o inesperado resultado de que o uso método de amostragem SMOTE não ter trazido melhoria na classificação de casos positivos de recorrência bioquímica, nem nos casos negativos, durante a validação dos modelos. Tendo em contas às variáveis seleccionadas e a sequência de prioridade dos melhores modelos Priority-LASSO, concluímos que os atributos radiómicos provindos da análise de textura de imagens MRI ponderadas em T2 poderão ter potencial para distinguir pacientes que não irão sofrer recidiva bioquímica inicial, conjuntamente com níveis iniciais de antigénio específico da próstata, num cenário pré-biópsia. A inclusão de parâmetros pré- ou pós-operatórios não adicionou valor substancial para a classificação de casos positivos de recidiva bioquímica em conjunto com variáveis radiómicos de MRI biparamétrica. Estudos com alto poder estatístico serão necessários para elucidar acerca do papel de atributos de radiómica baseados em imagens de bpMRI como predictores de recidiva bioquímica.Primary prostate cancer is often treated with radical prostatectomy (RP). Yet, 20–35% of males undergoing RP with curative intent will experience biochemical recurrence (BCR). Of those, two-thirds happen within two years, implying a more aggressive disease and poorer prognosis. Current BCR risk stratification tools are bounded to biopsy- or to surgery-derived histopathological evaluation, having limited ability for early treatment decision-making. Magnetic resonance imaging (MRI) is acquired as part of the diagnostic procedure and imaging derived features have shown promise in tumour characterisation and BCR prediction. We investigated the value of imaging features extracted from preoperative biparametric MRI (bpMRI) combined with clinic-histopathological data to develop models to predict two-year post-prostatectomy BCR in three simulated clinical scenarios: pre-biopsy, pre- and postoperative. In a cohort of 20 BCR positive and 73 BCR negative RP-treated patients examined in the same institution, 33 clinico-histopathological variables were retrospectively collected, and 2715 radiomic features (based on intensity, shape and texture) were extracted from the whole-prostate volume imaged in original and filtered T2- and Diffusion-weighted MRI and ADC maps scans. A systematic machine-learning framework comprised of classification, stratified k-fold cross validation and statistical analyses was developed to identify the top performing BCR classifiers’ configurations within three clinical scenarios. LASSO and Priority-LASSO logistic regression algorithms were used for feature selection and model fitting, optimising the amount of correctly classified BCR positive cases through AUC and F-score maximisation (Fmax) derived from ROC curve analysis. We also investigated the impact of two image normalisation methods and SMOTE-based minority oversampling on model performance. Priority-LASSO logistic regression with four-block priority sequence Clinical, T2w, DWI, ADC, with block sparsity restriction pmax = (1,7,0,1) was selected as the best performing model configuration across all clinical scenarios, outperforming LASSO logistic regression models. During development and across the simulated clinical scenarios, top models achieved good median Fmax values (range: 0.702–0.754 and 0.910–0.925 for BCR positive and negative classes, respectively); yet, during validation with an independent set, the models obtained very low Fmax for the target BCR positive class (0.297–0.400), revealing model overfitting. We also observed instability in the selected features. However, models attained reasonably good F-score (0.779–0.833) and Precision (0.821–0.873) for BCR negative class during training and validation phases, making these models worth exploring. Pre-biopsy models had lower performances in training but suffered less from overfitting. Preoperative classifiers were overoptimistic, and postoperative models were the most successful in detecting BCR negative cases. T2w-MRI textured-based radiomic features may have potential to distinguish negative BCR patients together with baseline prostate-specific antigen (PSA) levels in a pre-biopsy scenario. The inclusion of pre- or postoperative variables did not substantially add value to BCR positive cases classification with bpMRI radiomic features. Highly powered studies with curated imaging data are needed to elucidate the role of bpMRI radiomic features as predictors of BCR