David W Cescon

University Health Network, Toronto, Ontario, Canada

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Publications (24)328.48 Total impact

  • David W Cescon, Benjamin Haibe-Kains, Tak W Mak
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    ABSTRACT: Genomic sequencing studies of breast and other cancers have identified patterns of mutations that have been attributed to the endogenous mutator activity of APOBEC3B (A3B), a member of the AID/APOBEC family of cytidine deaminases. A3B gene expression is increased in many cancers, but its upstream drivers remain undefined. Furthermore, there exists a common germ-line deletion polymorphism (A3B(del)), which has been associated with a paradoxical increase in breast cancer risk. To examine causes and consequences of A3B expression and its constitutive absence in breast cancer, we analyzed two large clinically annotated genomic datasets [The Cancer Genome Atlas (TCGA) and the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC)]. We confirmed that A3B expression is associated with aggressive clinicopathologic characteristics and adverse outcomes and show that A3B expression is highly correlated with proliferative features (mitosis and cell cycle-related gene expression) in breast and 15 of 16 other solid tumor types. However, breast cancers arising in homozygous A3B(del) individuals with A3B absent did not differ in these features, indicating that A3B expression is a reflection rather than a direct cause of increased proliferation. Using gene set enrichment analysis (GSEA), we detected a pattern of immune activation in A3B(del) breast cancers, which seems to be related to hypermutation arising in A3B(del) carriers. Together, these results provide an explanation for A3B overexpression and its prognostic effect, giving context to additional study of this mutator as a cancer biomarker or putative drug target. In addition, although immune features of A3B(del) require additional study, these findings nominate the A3B(del) polymorphism as a potential predictor for cancer immunotherapy.
    Proceedings of the National Academy of Sciences 02/2015; DOI:10.1073/pnas.1424869112 · 9.81 Impact Factor
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    ABSTRACT: Controversy over the role of antioxidants in cancer has persisted for decades. Here, we demonstrate that synthesis of the antioxidant glutathione (GSH), driven by GCLM, is required for cancer initiation. Genetic loss of Gclm prevents a tumor's ability to drive malignant transformation. Intriguingly, these findings can be replicated using an inhibitor of GSH synthesis, but only if delivered prior to cancer onset, suggesting that at later stages of tumor progression GSH becomes dispensable potentially due to compensation from alternative antioxidant pathways. Remarkably, combined inhibition of GSH and thioredoxin antioxidant pathways leads to a synergistic cancer cell death in vitro and in vivo, demonstrating the importance of these two antioxidants to tumor progression and as potential targets for therapeutic intervention. Copyright © 2015 Elsevier Inc. All rights reserved.
    Cancer Cell 01/2015; 27(2). DOI:10.1016/j.ccell.2015.01.009 · 23.89 Impact Factor
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    ABSTRACT: Controversy over the role of antioxidants in cancer has persisted for decades. Here, we demonstrate that synthesis of the antioxidant glutathione (GSH), driven by GCLM, is required for cancer initiation. Genetic loss of Gclm prevents a tumor's ability to drive malignant transformation. Intriguingly, these findings can be replicated using an inhibitor of GSH synthesis, but only if delivered prior to cancer onset, suggesting that at later stages of tumor progression GSH becomes dispensable potentially due to compensation from alternative antioxidant pathways. Remarkably, combined inhibition of GSH and thioredoxin antioxidant pathways leads to a synergistic cancer cell death in vitro and in vivo, demonstrating the importance of these two antioxidants to tumor progression and as potential targets for therapeutic intervention.
    Cancer cell 01/2015; · 25.29 Impact Factor
  • David W Cescon, Chiara Gorrini, Tak W Mak
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    ABSTRACT: In this issue of Cancer Cell, Schwartz and colleagues and Costa and colleagues demonstrate that inhibition of PI3Kα or PI3Kβ in cancer cells with hyperactivated PI3Kα or PI3Kβ, respectively, activates the other isoform, leading to a "rebound" of the PI3K activity through different compensation mechanisms. Copyright © 2015 Elsevier Inc. All rights reserved.
    Cancer Cell 01/2015; 27(1):5-7. DOI:10.1016/j.ccell.2014.12.003 · 23.89 Impact Factor
  • David W Cescon, Philippe L Bedard
    Journal of Clinical Oncology 01/2015; DOI:10.1200/JCO.2014.59.3160 · 17.88 Impact Factor
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    ABSTRACT: PLK4 was identified as a promising therapeutic target through a systematic approach that combined RNAi screening with gene expression analysis in human breast cancers and cell lines. A drug discovery program culminated in CFI-400945, a potent and selective PLK4 inhibitor. Cancer cells treated with CFI-400945 exhibit effects consistent with PLK4 kinase inhibition, including dysregulated centriole duplication, mitotic defects, and cell death. Oral administration of CFI-400945 to mice bearing human cancer xenografts results in the significant inhibition of tumor growth at doses that are well tolerated. Increased antitumor activity in vivo was observed in PTEN-deficient compared to PTEN wild-type cancer xenografts. Our findings provide a rationale for the clinical evaluation of CFI-400945 in patients with solid tumors, in particular those deficient in PTEN.
    Cancer Cell 07/2014; 26(2). DOI:10.1016/j.ccr.2014.05.006 · 23.89 Impact Factor
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    ABSTRACT: Mutations in the tumor suppressor BRCA1 predispose women to breast and ovarian cancers. The mechanism underlying the tissue-specific nature of BRCA1's tumor suppression is obscure. We previously showed that the antioxidant pathway regulated by the transcription factor NRF2 is defective in BRCA1-deficient cells. Reactivation of NRF2 through silencing of its negative regulator KEAP1 permitted the survival of BRCA1-null cells. Here we show that estrogen (E2) increases the expression of NRF2-dependent antioxidant genes in various E2-responsive cell types. Like NRF2 accumulation triggered by oxidative stress, E2-induced NRF2 accumulation depends on phosphatidylinositol 3-kinase-AKT activation. Pretreatment of mammary epithelial cells (MECs) with the phosphatidylinositol 3-kinase inhibitor BKM120 abolishes the capacity of E2 to increase NRF2 protein and transcriptional activity. In vivo the survival defect of BRCA1-deficient MECs is rescued by the rise in E2 levels associated with pregnancy. Furthermore, exogenous E2 administration stimulates the growth of BRCA1-deficient mammary tumors in the fat pads of male mice. Our work elucidates the basis of the tissue specificity of BRCA1-related tumor predisposition, and explains why oophorectomy significantly reduces breast cancer risk and recurrence in women carrying BRCA1 mutations.
    Proceedings of the National Academy of Sciences 02/2014; 111(12). DOI:10.1073/pnas.1324136111 · 9.81 Impact Factor
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    ABSTRACT: Hormone receptor positive breast cancer is characterized by the potential for disease recurrence many years after initial diagnosis. Endocrine therapy has been shown to reduce the risk of such recurrence, but the optimal duration of endocrine therapy remains unclear. We conducted a systematic review and meta-analysis to quantify the benefits and harms of extended adjuvant tamoxifen (>5 years of therapy) compared with adjuvant tamoxifen (5 years of therapy). Odds ratios (ORs) and 95% confidence intervals (CIs) were computed for disease recurrence, death and adverse events. Subgroup analyses by timing of recurrence and baseline lymph node and menopause status were carried. Five trials comprising 21,554 patients were included. Extended adjuvant tamoxifen was not associated with a significant reduction in the risk of recurrence (OR:0.89, 95% CI 0.76-1.05, p = 0.17). There was no association between extended adjuvant tamoxifen and all-cause death (OR:0.99, 95% CI 0.84-1.16, p = 0.88). There was an apparent reduction in risk of recurrence occurring after completion of extended adjuvant tamoxifen with little evidence of effect during therapy, however, this difference was not significant (p for difference 0.10). Subgroup analysis suggested that a greater effect size among lymph node positive patients compared with those who are lymph node negative (NNT: 25 vs. 49). There was no apparent difference in the effect between pre- and post-menopausal patients. Endometrial carcinoma was substantially more frequent with extended adjuvant tamoxifen (OR:2.06, 95% CI 1.65-2.58, p<0.001, number needed to harm:89). In unselected patients, extended adjuvant tamoxifen is not associated with a significant reduction in recurrence, or a reduction in all-cause death. Patients with lymph node positive breast cancer may derive some benefit. Reduction in the risk of recurrence appears to occur only after completion of extended adjuvant therapy.
    PLoS ONE 02/2014; 9(2):e88238. DOI:10.1371/journal.pone.0088238 · 3.53 Impact Factor
  • Cancer Research 08/2013; 73(8 Supplement):4647-4647. DOI:10.1158/1538-7445.AM2013-4647 · 9.28 Impact Factor
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    ABSTRACT: Oxidative stress plays an important role in cancer development and treatment. Recent data implicate the tumor suppressor BRCA1 in regulating oxidative stress, but the molecular mechanism and the impact in BRCA1-associated tumorigenesis remain unclear. Here, we show that BRCA1 regulates Nrf2-dependent antioxidant signaling by physically interacting with Nrf2 and promoting its stability and activation. BRCA1-deficient mouse primary mammary epithelial cells show low expression of Nrf2-regulated antioxidant enzymes and accumulate reactive oxygen species (ROS) that impair survival in vivo. Increased Nrf2 activation rescues survival and ROS levels in BRCA1-null cells. Interestingly, 53BP1 inactivation, which has been shown to alleviate several defects associated with BRCA1 loss, rescues survival of BRCA1-null cells without restoring ROS levels. We demonstrate that estrogen treatment partially restores Nrf2 levels in the absence of BRCA1. Our data suggest that Nrf2-regulated antioxidant response plays a crucial role in controlling survival downstream of BRCA1 loss. The ability of estrogen to induce Nrf2 posits an involvement of an estrogen-Nrf2 connection in BRCA1 tumor suppression. Lastly, BRCA1-mutated tumors retain a defective antioxidant response that increases the sensitivity to oxidative stress. In conclusion, the role of BRCA1 in regulating Nrf2 activity suggests important implications for both the etiology and treatment of BRCA1-related cancers.
    Journal of Experimental Medicine 07/2013; DOI:10.1084/jem.20121337 · 13.91 Impact Factor
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    ABSTRACT: BACKGROUND AND AIMS: Although gastroesophageal reflux disease (GERD) is a risk factor for esophageal adenocarcinoma (EAC), some patients develop EAC in the absence of GERD. A putative mechanism of reflux-induced tumorigenesis involves disruptions in the p53 pathway. We assessed the interaction of GERD and p53 pathway polymorphisms on EAC prognosis. METHODS: In a prospective cohort of 358 EAC patients, clinical data (including GERD history and survival) were collected. Germline DNA was genotyped for MDM2 T309G and p53 Arg72Pro. Cox proportional hazards models were used to determine adjusted hazard ratios (AHR) for associations between genotype, GERD, and genotype-GERD interactions with survival. RESULTS: Compared with other genotypes, MDM2 G/G (median overall survival 21 versus 30 months; p<0.001) and p53 Pro/Pro (12 versus 30 months; p=0.004) were associated with shorter survival. When analyzed by GERD, MDM2 G/G was associated with shorter survival in patients without GERD (AHR 3.4, 95% C.I. 2.0-6.0), but not in patients with GERD (AHR 1.1 (0.7-1.8)); the MDM2-GERD interaction was significant (p=0.003). A similar trend was seen for p53 Pro/Pro (AHRs 2.5 without GERD versus 1.4 with GERD). Combined analysis of at-risk variants (MDM2 G or p53 Pro), revealed each additional at-risk variant was associated with shorter survival in patients without GERD (AHR 1.6), but not with GERD (AHR 1.0). CONCLUSIONS: MDM2 G/G and the combination of MDM2 G and p53 Pro were negative prognostic factors for EAC patients without GERD, but not for those with GERD. There may be biological differences between GERD positive and GERD negative EAC.
    Journal of Gastroenterology and Hepatology 06/2013; DOI:10.1111/jgh.12286 · 3.33 Impact Factor
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    ABSTRACT: Tumorigenesis results from dysregulation of oncogenes and tumor suppressors that influence cellular proliferation, differentiation, apoptosis, and/or senescence. Many gene products involved in these processes are substrates of the E3 ubiquitin ligase Mule/Huwe1/Arf-BP1 (Mule), but whether Mule acts as an oncogene or tumor suppressor in vivo remains controversial. We generated K14Cre;Mule(flox/flox(y)) (Mule kKO) mice and subjected them to DMBA/PMA-induced skin carcinogenesis, which depends on oncogenic Ras signaling. Mule deficiency resulted in increased penetrance, number, and severity of skin tumors, which could be reversed by concomitant genetic knockout of c-Myc but not by knockout of p53 or p19Arf. Notably, in the absence of Mule, c-Myc/Miz1 transcriptional complexes accumulated, and levels of p21CDKN1A (p21) and p15INK4B (p15) were down-regulated. In vitro, Mule-deficient primary keratinocytes exhibited increased proliferation that could be reversed by Miz1 knockdown. Transfer of Mule-deficient transformed cells to nude mice resulted in enhanced tumor growth that again could be abrogated by Miz1 knockdown. Our data demonstrate in vivo that Mule suppresses Ras-mediated tumorigenesis by preventing an accumulation of c-Myc/Miz1 complexes that mediates p21 and p15 down-regulation.
    Genes & development 05/2013; 27(10):1101-1114. DOI:10.1101/gad.214577.113 · 12.64 Impact Factor
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    ABSTRACT: Lung cancer is the leading global cause of cancer-related mortality. Interindividual variability in treatment response and cancer outcomes has focused attention on genetic polymorphisms as prognostic markers. We evaluated the overall contribution of candidate polymorphism association studies to our current understanding of the genetic predictors of lung cancer outcomes. We examined the results of 90 studies that evaluated associations between genetic polymorphisms and lung cancer outcomes published between January 1990 and May 2009. A total of 170 genetic variations in 90 studies were identified. Overall survival was a primary outcome in 81% of the studies and toxicity in 19%. Candidate polymorphisms in the DNA repair/synthesis pathway were the most frequently studied. Strong evidence in large-scale confirmatory studies of any single polymorphism was lacking. Polymorphisms of EGFR, XRCC1, and ERCC1 were associated with pharmacogenetic outcomes, whereas polymorphisms of MDM2, p53, and GSTM1 were associated with prognostic outcomes. All remaining polymorphisms had results lacking or failing replication testing. Heterogeneity in study populations, incomplete reporting of important population or study characteristics, inadequate power, and inconsistencies in methodology were common. Although the quality of existing studies involving the candidate polymorphism approach is highly variable, a small set of candidate polymorphisms was identified as potential biomarkers of clinical or pharmacogenetic outcome and would benefit from further replication testing. Newer approaches including haplotype tagging, pathway, genome-wide association, and combination methods with validative approaches may facilitate a more accurate prediction of lung cancer outcomes by genetic variation.
    Journal of thoracic oncology: official publication of the International Association for the Study of Lung Cancer 02/2011; 6(2):296-304. DOI:10.1097/JTO.0b013e3181ffe909 · 4.55 Impact Factor
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    ABSTRACT: Phase III randomized clinical trials (RCTs) have become larger and are powered to detect small absolute benefits. Temporal changes in absolute benefits of experimental medical therapies reported in RCTs are unknown. We identified all RCTs with sample size > or =200 evaluating experimental medical therapies for breast and colorectal cancer published from 1975 to 2007. We assessed changes over three decades in absolute differences in time-to-event end points between experimental and control arms by (i) the usual method (i.e. at one point) and (ii) as the area between time-to-event curves up to a predefined time. We identified 236 eligible RCTs of which 57% (N = 135) evaluated adjuvant treatments. Experimental treatments became more often compared with active treatments (48% versus 59% versus 81%; P < 0.0001). Median absolute benefits of experimental adjuvant treatments decreased but outcomes in control arms improved with time. For RCTs evaluating metastatic disease, there were no changes in absolute benefit over time but incremental monthly costs of new approved treatments increased with time by 100-fold (P < 0.0001). In RCTs of breast and colorectal cancer, new effective adjuvant treatments show decreasing absolute benefit, while new treatments of metastatic disease show unchanging levels of benefit at rapidly escalating costs.
    Annals of Oncology 11/2009; 21(7):1411-8. DOI:10.1093/annonc/mdp552 · 6.58 Impact Factor
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    ABSTRACT: To assess the frequency, implications, and factors associated with reporting nonfinal analyses (NFAs) of randomized controlled trials (RCTs) as abstract publications. We identified 138 consecutive reports of RCTs testing systemic therapy for lymphoma, breast, colorectal, or non-small-cell lung cancer published in six major journals between 2000 and 2004. We then searched proceedings of seven major cancer meetings, 1990 to 2004, for abstracts related to these publications which presented efficacy results. Articles and abstracts were compared for discordance in sample size, median follow-up, results, and conclusions. Abstracts were evaluated for statements explicitly noting or implying that results were not final. Factors associated with discordance were assessed by uni- and multivariate analyses. We identified 303 related abstracts; 197 were eligible. In 86 abstracts (44%), results were stated or implied to be NFA; this was explicitly stated in 41 (21%). The NFAs included 12 where accrual was ongoing. Discordance with article was found in 124 abstracts (63%) and was more common with NFAs (67 of 86 [78%] v 57 of 111 [51%]; P = .0001). When compared with articles, authors' conclusions were substantively different in 17 abstracts (10%). Factors most associated with data discordance were lymphoma trial (odds ratio [OR], 3.8; 95% CI, 1.5 to 10.8), cooperative group trial (OR, 2.8; 95% CI, 1.4 to 5.6), and presentation of a NFA (OR, 2.9; 95% CI, 1.5 to 5.8). Meeting abstracts often include NFAs and are frequently discordant with subsequent article publication.
    Journal of Clinical Oncology 08/2009; 27(24):3938-44. DOI:10.1200/JCO.2008.18.8771 · 17.88 Impact Factor
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    ABSTRACT: This study aimed to evaluate the prognostic significance of two functional single nucleotide polymorphisms (SNP) in the p53 pathway (p53 Arg72Pro and MDM2 T309G) in patients with esophageal cancer, and to determine the importance of histologic subtype in the SNP-outcome relationships. A cohort of 371 patients with esophageal carcinoma enrolled in Boston, USA from 1999 to 2004 were genotyped for the p53 and MDM2 SNPs. Associations between genotypes and overall survival (OS; the primary outcome) and progression-free survival (PFS) were assessed using the Kaplan-Meier method. Cox proportional hazard models, adjusted for age, stage, performance status, and smoking were developed. Interaction analyses were done for histology (adenocarcinoma versus squamous cell carcinoma). At the median follow-up of 33 months, median survival (MS) and PFS were 29.1 and 15.7 months, respectively. p53 Pro/Pro was strongly associated with shorter survival in the entire cohort (MS of 11.8 versus 29.1 months, P < 0.0001; adjusted hazard ratio for death, 2.05; 95% confidence interval, 1.30-3.24; P = 0.002 for Pro/Pro versus Arg/Arg). MDM2 G/G was associated with markedly reduced survival in squamous cell carcinoma (MS of 10.3 versus 49.4 months; adjusted hazard ratio for death, 7.9; 95% confidence interval, 2.4-26.0; P = 0.0007 for G/G versus T/T) but not in adenocarcinoma (SNP-histology interaction P = 0.004). In a large prospective cohort, p53 Arg72Pro Pro/Pro was associated with a 2-fold increased risk of death in all esophageal cancers, whereas MDM2 T309G G/G was associated with a 7-fold increased risk of death in squamous cell carcinoma.
    Clinical Cancer Research 05/2009; 15(9):3103-9. DOI:10.1158/1078-0432.CCR-08-3120 · 8.19 Impact Factor
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    ABSTRACT: p53 Arg72Pro, MDM2 T309G, and CCND1 G870A are functional single-nucleotide polymorphisms (SNPs) in key genes that regulate apoptosis and cell cycle. Variant genotypes of these SNPs have been associated with increased risk and earlier age of onset in some cancers. We investigated the association of these SNPs with susceptibility to esophageal adenocarcinoma in a large, North American case-control study. Three hundred and twelve cases and 454 cancer-free controls recruited in Boston, USA were genotyped for each of the three SNPs, and demographic and clinical data were collected. Genotype frequencies for each of the three SNPs did not deviate from the Hardy-Weinberg equilibrium, and did not differ between cases and controls. Odds ratios (OR), adjusted for clinical risk factors, for the homozygous variant genotypes were 0.99 (95% confidence interval [CI] 0.57-1.72) for p53 Pro/Pro, 0.81 (95% CI 0.52-1.28) for MDM2 G/G, and 0.97 (95% CI 0.64-1.49) for CCND1 A/A. The analysis was adequately powered (80%) to detect ORs of 1.37, 1.35, and 1.34 for each SNP, respectively. In contrast to the results of smaller published studies, no association between p53 Arg72Pro, MDM2 T309G, and CCND1 G870A SNPs and susceptibility to esophageal adenocarcinoma, age of onset, or stage of disease at diagnosis was detected.
    Diseases of the Esophagus 04/2009; 23(1):36-9. DOI:10.1111/j.1442-2050.2009.00960.x · 2.06 Impact Factor
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    David W Cescon, David N Juurlink
    Canadian Medical Association Journal 02/2009; 180(2):251. DOI:10.1503/cmaj.080727 · 5.81 Impact Factor
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    ABSTRACT: The randomized controlled trial (RCT) is the gold standard for establishing new therapies in clinical oncology. Here we document changes with time in design, sponsorship, and outcomes of oncology RCTs. Reports of RCTs evaluating systemic therapy for breast, colorectal (CRC), and non-small-cell lung cancer (NSCLC) published 1975 to 2004 in six major journals were reviewed. Two authors abstracted data regarding trial design, results, and conclusions. Conclusions of authors were graded using a 7-point Likert scale. For each study the effect size for the primary end point was converted to a summary measure. A total of 321 eligible RCTs were included (48% breast, 24% CRC, 28% NSCLC). Over time, the number and size of RCTs increased considerably. For-profit/mixed sponsorship increased substantially during the study period (4% to 57%; P < .001). There was increasing use of time-to-event measures (39% to 78%) and decreasing use of response rate (54% to 14%) as primary end point (P < .001). Effect size remained stable over the study period. Authors have become more likely to strongly endorse the experimental arm (P = .017). A significant P value for the primary end point and industry sponsorship were each independently associated with endorsement of the experimental agent (odds ratio [OR] = 19.6, 95% CI, 8.9 to 43.1, and OR = 3.5, 95% CI, 1.6 to 7.5, respectively). RCTs in oncology have become larger and are more likely to be sponsored by industry. Authors of modern RCTs are more likely to strongly endorse novel therapies. For-profit sponsorship and statistically significant results are independently associated with endorsement of the experimental arm.
    Journal of Clinical Oncology 11/2008; 26(33):5458-64. DOI:10.1200/JCO.2008.16.5456 · 17.88 Impact Factor
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    ABSTRACT: A patient presented with a small-bowel obstruction associated with signs and symptoms of botulism. Fecal cultures were positive for viable Clostridium botulinum. This case emphasizes the importance of a broad differential diagnosis and doing a complete examination to account for all signs and symptoms.
    Canadian Medical Association Journal 11/2008; 179(9):927-9. DOI:10.1503/cmaj.080651 · 5.81 Impact Factor

Publication Stats

737 Citations
328.48 Total Impact Points

Institutions

  • 2013–2015
    • University Health Network
      • • Department of Medical Biophysics
      • • Campbell Family Institute for Breast Cancer Research
      Toronto, Ontario, Canada
  • 2008–2015
    • University of Toronto
      • Department of Medicine
      Toronto, Ontario, Canada
  • 2008–2013
    • The Princess Margaret Hospital
      Toronto, Ontario, Canada