Geriatric Oncology as an Unmet Workforce Training Need in the United Kingdom-A Narrative Review by the British Oncology Network for Undergraduate Societies (BONUS) and the International Society of Geriatric Oncology (SIOG) UK Country Group.

Cancer is a disease associated with ageing. Managing cancer in older adults may prove challenging owing to pre-existing frailty, comorbidity, and wider holistic needs, as well as the unclear benefits and harms of standard treatment options. With the ongoing advances in oncology and the increasing complexity of treating older adults with cancer, the geriatric oncology field must be a priority for healthcare systems in education, research, and clinical practice. However, geriatric oncology is currently not formally taught in undergraduate education or postgraduate training programmes in the United Kingdom (UK). In this commentary, we outline the landscape of geriatric oncology undergraduate education and postgraduate training for UK doctors. We highlight current challenges and opportunities and provide practical recommendations for better preparing the medical workforce to meet the needs of the growing population of older adults with cancer. This includes key outcomes to be considered for inclusion within undergraduate and postgraduate curricula.

Geriatric assessment prior to cancer treatment: A health economic evaluation.

INTRODUCTION: To address uncertainty regarding the cost-effectiveness of implementing geriatric assessment (GA) in oncology practice, we undertook a synthetic, model-based economic evaluation. MATERIALS AND METHODS: A decision-analytic model with embedded Markov chains was developed to simulate a cost-effectiveness analysis of implementing GA within standard oncological care compared to current practice. This was for patients aged 77 years (the mean age in included trials) receiving chemotherapy or surgery as first-line treatment. Assumptions were made about model parameters, based on available literature, to calculate the incremental net health benefit (INHB) of GA, using a data synthesis. RESULTS: GA has additional costs over standard care alone of between £390 and £576, depending upon implementation configuration. When major assumptions about the effectiveness of GA were modelled, INHB was marginally positive (0.09-0.12) at all cost-effectiveness thresholds (CETs). If no reduction in postoperative complications was assumed, the intervention was shown not to be cost-effective (INHB negative at all CETs). When used before chemotherapy, with minimal healthcare staffing inputs and technological assistance, GA is cost-effective (INHB positive between 0.06 and 0.07 at all CETs). DISCUSSION: Considering emerging evidence that GA improves outcomes in oncology, GA may not be a cost-effective intervention when used for all older adults with cancer. However, with judicious selection of implementation models, GA has the potential to be cost-effective. Due to significant heterogeneity and centre dependent success in implementation and effectiveness, GA is difficult to study in oncology settings. Stakeholders could take a pragmatic approach towards GA introduction with local evaluation favoured over generalisable research. Because GA tends towards utilitarianism and has no safety issues, it is a suitable intervention for more widespread implementation.

Implementation of geriatric assessment in oncology settings: A systematic realist review.

Older adults with cancer are more likely to have worse clinical outcomes than their younger counterparts, and shared decision-making can be difficult, due to both complexity from adverse ageing and under-representation in clinical trials. Geriatric assessment (GA) has been increasingly recognised as a predictive and prehabilitative tool for older adults with cancer. However, GA has been notoriously difficult to implement in oncological settings due to workforce, economic, logistical, and practical barriers. We aimed to review the heterogenous literature on implementation of GA in oncology settings to understand the different implementation context configurations of GA and the mechanisms they trigger to enable successful implementation. A systematic realist review was undertaken in two stages: i) systematic searches with structured data extraction combined with iterative key stakeholder consultations to develop programme theories for implementing GA in oncology settings; ii) synthesis to refine programme theories. Medline, Embase, PsycInfo, Cochrane Library, CINAHL, Web of Science, Scopus, ASSIA, Epistemonikos, JBI Database of Systematic Reviews and Implementation Reports, DARE and Health Technology Assessment were searched. Four programme theories were developed from 53 included articles and 20 key stakeholder consultations addressing the major barriers of GA implementation in oncology practice: time (leveraging non-specialists), funding (creating favourable health economics), practicalities (establishing the use of GA in cancer care), and managing limited resources. We demonstrate that a whole system approach is required to improve the implementation of GA in cancer settings. This review will help inform policy decisions regarding implementation of GA and provide a basis for further implementation research.

The Investigation of Lipoxygenases as Therapeutic Targets in Malignant Pleural Mesothelioma.

Advanced malignant pleural mesothelioma (MPM) has an extremely poor prognosis with limited chemotherapy options, therefore the identification of new therapeutic targets would aid in disease management. Arachidonic acid is metabolised by cyclooxygenase and lipoxygenase enzymes. The lipoxygenase isoenzymes 5-LOX and 12-LOX have been implicated in carcinogenesis. We aimed to examine 5-LOX and 12-LOX protein expression in a large retrospective series of mesothelioma samples. Further to this, the in vitro cytotoxic effects of lipoxygenase pathway inhibitors were investigated in mesothelioma cells. Archival samples from 83 patients with MPM were examined by immunohistochemistry for expression of the 5-LOX and 12-LOX proteins. The MTS assay was used to assess cell viability following 72 h treatment with the lipoxygenase pathway inhibitors baicalein, licofelone, MK-886 and zileuton in the MPM cell lines NCI-H2052, NCI-H2452 and MSTO-211H. Positive 12-LOX protein expression was recorded in 69/83 (83%) and positive 5-LOX expression was observed in 56/77 (73%) of MPM tissue samples. Co-expression of 5-LOX with 12-LOX was seen in 46/78 (58%) of MPM samples. Positive expression of 5-LOX, 12-LOX and COX-2 proteins was identified in the NCI-H2052, NCI-H2452 and MSTO-211H MPM cell lines. Baicalein (12-LOX and 15-LOX inhibitor) was effective in 3/3 MPM cell lines at low concentrations with an IC50 range of 9.6 µM to 20.7 µM. We have demonstrated that the 5-LOX and 12-LOX proteins are expressed in a significant proportion of MPM samples (73% and 83% respectively) and may represent novel therapeutic targets in this disease. We have demonstrated that the inhibition of the LOX pathway using baicalein may be effective as a novel treatment for MPM, however further human pharmacokinetic studies are required in order to establish whether the concentration used in vitro is clinically achievable.

Variation in geographical treatment intensity affects survival of non-small cell lung cancer patients in England.

OBJECTIVES: We aimed to determine the geographical variation in the proportion of non-small cell lung cancer (NSCLC) patients undergoing curative treatment and assess the relationship between treatment access rates and survival outcomes. METHODS: We extracted cancer registration data on 144,357 lung cancer (excluding small cell tumours) patients diagnosed between 2009 and 2013. Surgical and radiotherapy treatment intensity quintiles were based on patients' Clinical Commissioning Group (CCG) of residence. We used logistic regression to assess the effect of travel time and case-mix on treatment use and Cox regression to analyse survival in relation to treatment intensity. RESULTS: There was wide variation in the use of curative treatment across CCGs, with the proportion undergoing surgery ranging from 8.9% to 20.2%, and 0.4% to 16.4% for radical radiotherapy. The odds of undergoing surgery decreased with socioeconomic deprivation (OR 0.91, 95% CI 0.85-0.97), whereas the opposite was observed for radiotherapy (OR 1.16, 95% CI 1.08-1.25). There was an overall effect of travel time to thoracic surgery centre on the odds of undergoing surgery (OR 0.81, 95% CI 0.76-0.87 for travel time >55 min vs ≤15 min) which was amplified by the effect of deprivation. No clear association was observed for radiotherapy. Higher mortality rates were observed for the lower resection and radiotherapy quintiles (HR 1.08, 95% CI 1.04-1.12 and HR 1.06, 95% CI 1.02-1.10 for lowest vs. highest resection and radiotherapy quintile). CONCLUSION: There was wide geographical variation in the use of curative treatment and a higher frequency of treatment was associated with better survival.

MicroRNA-31 Regulates Chemosensitivity in Malignant Pleural Mesothelioma.

Malignant pleural mesothelioma (MPM) is associated with an extremely poor prognosis, and most patients initially are or rapidly become unresponsive to platinum-based chemotherapy. MicroRNA-31 (miR-31) is encoded on a genomic fragile site, 9p21.3, which is reportedly lost in many MPM tumors. Based on previous findings in a variety of other cancers, we hypothesized that miR-31 alters chemosensitivity and that miR-31 reconstitution may influence sensitivity to chemotherapeutics in MPM. Reintroduction of miR-31 into miR-31 null NCI-H2452 cells significantly enhanced clonogenic resistance to cisplatin and carboplatin. Although miR-31 re-expression increased chemoresistance, paradoxically, a higher relative intracellular accumulation of platinum was detected. This was coupled to a significantly decreased intranuclear concentration of platinum. Linked with a downregulation of OCT1, a bipotential transcriptional regulator with multiple miR-31 target binding sites, we subsequently identified an indirect miR-31-mediated upregulation of ABCB9, a transporter associated with drug accumulation in lysosomes, and increased uptake of platinum to lysosomes. However, when overexpressed directly, ABCB9 promoted cellular chemosensitivity, suggesting that miR-31 promotes chemoresistance largely via an ABCB9-independent mechanism. Overall, our data suggest that miR-31 loss from MPM tumors promotes chemosensitivity and may be prognostically beneficial in the context of therapeutic sensitivity.

The effect of emergency presentation on surgery and survival in lung cancer patients in England, 2006-2008.

BACKGROUND: A large proportion of lung cancer patients in England are diagnosed through an emergency route, which is associated with poorer outcomes. Here, we investigated the association between emergency presentation and the odds of undergoing surgical resection and subsequent survival among lung cancer patients undergoing surgical resection as well as those who did not. METHODS: Details of 93,783 lung cancers were extracted from the National Cancer Data Repository. For non-small cell lung cancer (NSCLC) patients we calculated odds ratios for undergoing surgical resection. Survival was assessed for resected NSCLC and for all other lung cancer patients in three different time intervals: short-term, intermediate and long-term. RESULTS: Compared with those who did not, NSCLC patients presenting through an emergency route were less likely to undergo surgical resection (adjusted OR=0.22, 95% CI: 0.20-0.24). Patients who underwent surgical resection after an emergency presentation had lower survival in the intermediate period (adjusted HR=1.27, 95% CI: 1.06-1.54) and long term (adjusted HR=1.20, 95% CI: 0.99-1.45). Among all other lung cancer patients, those diagnosed through an emergency route had lower survival, particularly in the short-term (adjusted HR=3.54, 95% CI: 3.42-3.67), but the association remained in the intermediate (adjusted HR=1.66, 95% CI: 1.63-1.69) and long term (adjusted HR=1.10, 95% CI: 1.05-1.15). CONCLUSION: The reduced access to surgical resection and lower survival among lung cancer patients who present through an emergency admission, highlights the importance of ensuring symptoms are recognised early so that presentation as an emergency can be reduced.

Merkel cell carcinoma in East Yorkshire: A case series and literature review of current management.

INTRODUCTION: Merkel cell carcinoma (MCC) is a rare, aggressive neuroendocrine tumour of the skin. The incidence is rising and it is associated with sun exposure and immunosuppression. Our aim was to perform a 10-year retrospective review of MCC treated in East Yorkshire and to examine disease progression, surgical and adjuvant management, and outcomes. METHODS: A 10-year retrospective review was undertaken of patients identified through the histopathology database. Case notes and digital patient records were examined for patient demographics, disease characteristics, management and outcome. Disease stage was calculated using the 2010 AJCC TNM classification. RESULTS: Thirty-seven patients with complete records were included. Twenty-one patients were male and 16 female, with mean age 76.7 years at presentation. Pre-malignant or malignant skin changes were documented in 15 patients, and immunosuppression in 15 patients. Mean duration of lesion was 17.5 weeks. Following diagnosis 22/37 patients underwent further surgery with 11 patients undergoing sentinel lymph node (LN) biopsy. LN disease was palpable at presentation in 8 patients. Three year survival is 40%. CONCLUSIONS: There is no standardised management of MCC and randomised trials are challenging due to relatively small numbers. There has been little progress made in terms of improving survival. Development of a national database for patients with this condition would allow prospective data collection and more accurate assessment of current treatment protocols and their efficacy. LEVEL OF EVIDENCE: IV.

Clinical response to primary letrozole therapy in elderly patients with early breast cancer: possible role for p53 as a biomarker.

Primary tamoxifen therapy has been widely used to treat elderly women with ER-positive breast cancer in the past. Aromatase inhibitors may be more beneficial than tamoxifen when used as primary endocrine therapy in elderly patients. We aimed to retrospectively evaluate a series of elderly women with ER-positive breast cancer treated with primary letrozole therapy as sole therapy with a minimum of 5 years follow up. To identify possible predictive biomarkers a pilot immunohistochemical analysis was performed to assess the expression of PR, HER2, EGFR, BCL2 and p53. A total of 45 women, aged more than 70 years with a diagnosis of ER-positive breast cancer that was treated with primary letrozole therapy were identified. A case note review was undertaken to obtain clinical information. Formalin fixed paraffin embedded tumour tissue from diagnostic core biopsies was available for all patients. Immunohistochemical analysis was performed to establish the protein expression status of p53, PR, HER2, EGFR and BCL2. The mean age of the 45 patients was 87 years (range 70-101). Clinical benefit was seen in 60% of the patients. Median progression free survival was 53 months (95% CI - 34-72) and the median time to progression was 43 months (95% CI - 22-64). BCL2 was expressed in 45/45 (100%); PR in 38/45 (84%); EGFR in 13/45 (28%); HER2 in 9/45 (20%) and p53 in 5/45 (11%) of tissue samples. Positive expression of p53 was associated with poor progression free survival (p = 0.03) in this pilot study. This study demonstrates that letrozole as sole treatment appears to be a suitable treatment option for elderly patients with ER-positive breast cancer who are not fit for, or decline, surgery. The analysis of p53 in a larger study is warranted in order to assess its role as a biomarker in this patient group.

High procedure volume is strongly associated with improved survival after lung cancer surgery.

PURPOSE: Studies have reported an association between hospital volume and survival for non-small-cell lung cancer (NSCLC). We explored this association in England, accounting for case mix and propensity to resect. METHODS: We analyzed data on 134,293 patients with NSCLC diagnosed in England between 2004 and 2008, of whom 12,862 (9.6%) underwent surgical resection. Hospital volume was defined according to number of patients with resected lung cancer in each hospital in each year of diagnosis. We calculated hazard ratios (HRs) for death in three predefined periods according to hospital volume, sex, age, socioeconomic deprivation, comorbidity, and propensity to resect. RESULTS: There was increased survival in hospitals performing > 150 surgical resections compared with those carrying out < 70 (HR, 0.78; 95% CI, 0.67 to 0.90; Ptrend < .01). The association between hospital volume and survival was present in all three periods of follow-up, but the magnitude of association was greatest in the early postoperative period. CONCLUSION: High-volume hospitals have higher resection rates and perform surgery among patients who are older, have lower socioeconomic status, and have more comorbidities; despite this, they achieve better survival, most notably in the early postoperative period.

Proteomic (antibody microarray) exploration of the molecular mechanism of action of the specific COX-2 inhibitor DuP 697.

We have previously shown that specific COX-2 inhibitors, including DuP 697, have anti-proliferative effects on mesothelioma cells and potentiate the cytotoxicity of pemetrexed. Here, we used a novel proteomic approach to explore the mechanism of action of this agent. COX-2-positive cell lines MSTO-211H (mesothelioma) and A549 (lung cancer) were exposed to DuP 697 for 72 h. Drug carrier only was added to control cells. Extracted proteins from treated and control cells were analysed using a comparative proteomic platform. Differentially expressed proteins, identified by the Panorama Xpress Profiler725 antibody microarray were submitted to Ingenuity Pathway Analysis. A total of 32 unique differentially expressed proteins were identified with a significant (>1.8-fold) difference in expression between treated and untreated cells in at least one cell line. Five molecules, BCL2L1 (Bcl-xL), BID, CHUK (IKK), FASLG and RAF1, were mapped to the Apoptosis Signaling pathway following Ingenuity Pathway Analysis. BCL2L1 (Bcl-xL) and BID were analysed using immuno-blotting and differential expression was confirmed. Proteomic (antibody microarray) analysis suggests that the mechanism of action of DuP 697 may be exerted via the induction of apoptosis. The antibody microarray platform can be utilised to explore the molecular mechanism of action of novel anticancer agents.

PTEN protein expression in malignant pleural mesothelioma.

Malignant pleural mesothelioma is associated with poor prognosis and despite recent advances in chemotherapy, the median survival is still approximately 12 months. Loss of phosphatase and tensin homolog (PTEN) protein expression may lead to constitutive activation of AKT resulting in cell survival and proliferation. Small studies reported that PTEN protein expression is rarely lost in mesothelioma whilst a larger study demonstrated prognostic significance of PTEN protein expression status with absence in 62 % of cases. We aimed to analyse PTEN protein expression in mesothelioma. Immunohistochemical analysis was performed in 86 archival mesothelioma samples to determine the PTEN protein expression status and statistical analysis was performed to identify any prognostic significance. Mesothelial cells in normal pleura demonstrated positive staining for PTEN protein and served as a positive reference. For mesothelioma samples, the expression of PTEN protein was scored as 0 (negative), 1 (intensity less than that of positive normal pleura reference slide) and 2 (intensity equal to or greater than positive normal pleura reference slide). A total of 23/86 (26.7 %) scored 0, 23/86 (26.7 %) scored 1 and 40/86 (46.5 %) scored 2 for PTEN expression. Univariate analysis demonstrated that lack of PTEN expression was not associated with survival. PTEN protein expression was undetectable in 26.7 % of mesothelioma samples; however, no prognostic significance was identified. Absence of PTEN protein may result in activation of the PI3K/AKT/MTOR pathway. Targeting this pathway with inhibitors further downstream of PTEN may provide a potential therapeutic target in selected patients.

Pilot and feasibility study: comparative proteomic analysis by 2-DE MALDI TOF/TOF MS reveals 14-3-3 proteins as putative biomarkers of response to neoadjuvant chemotherapy in ER-positive breast cancer.

Neoadjuvant chemotherapy is used to treat oestrogen receptor-positive breast cancer however chemo-resistance is a major obstacle in this molecular subtype. The ability to predict tumour response would allow chemotherapy administration to be directed towards patients who would most benefit, thus maximising treatment efficacy. We aimed to identify protein biomarkers associated with response to neoadjuvant chemotherapy, in a pilot study using comparative 2-DE MALDI TOF/TOF MS proteomic analysis of breast tumour samples. A total of 3 comparative proteomic experiments were performed, comparing protein expression between chemotherapy-sensitive and chemotherapy-resistant oestrogen receptor-positive invasive ductal carcinoma tissue samples. This identified a list of 132 unique proteins that were significantly differentially expressed (≥ 2 fold) in chemotherapy resistant samples, 57 of which were identified in at least two experiments. Ingenuity® Pathway Analysis was used to map the 57 DEPs onto canonical signalling pathways. We implicate several isoforms of 14-3-3 family proteins (theta/tau, gamma, epsilon, beta/alpha and zeta/delta), which have previously been associated with chemotherapy resistance in breast cancer. Extensive clinical validation is now required to fully assess the role of these proteins as putative markers of chemotherapy response in luminal breast cancer subtypes.

Proteomic identification of predictive biomarkers of resistance to neoadjuvant chemotherapy in luminal breast cancer: a possible role for 14-3-3 theta/tau and tBID?

INTRODUCTION: Chemotherapy resistance is a major obstacle in effective neoadjuvant treatment for estrogen receptor-positive breast cancer. The ability to predict tumour response would allow chemotherapy administration to be directed towards only those patients who would benefit, thus maximising treatment efficiency. We aimed to identify putative protein biomarkers associated with chemotherapy resistance, using fresh tumour samples with antibody microarray analysis and then to perform pilot clinical validation experiments. MATERIALS AND METHODS: Chemotherapy resistant and chemotherapy sensitive tumour samples were collected from breast cancer patients who had received anthracycline based neoadjuvant therapy consisting of epirubicin with cyclophosphamide followed by docetaxel. A total of 5 comparative proteomics experiments were performed using invasive ductal carcinomas which demonstrated estrogen receptor positivity (luminal subtype). Protein expression was compared between chemotherapy resistant and chemotherapy sensitive tumour samples using the Panorama XPRESS Profiler725 antibody microarray containing 725 antibodies from a wide variety of cell signalling and apoptosis pathways. A pilot series of archival samples was used for clinical validation of putative predictive biomarkers. RESULTS: AbMA analysis revealed 38 differentially expressed proteins which demonstrated at least 1.8 fold difference in expression in chemotherapy resistant tumours and 7 of these proteins (Zyxin, 14-3-3 theta/tau, tBID, Pinin, Bcl-xL, RIP and MyD88) were found in at least 2 experiments. Clinical validation in a pilot series of archival samples revealed 14-3-3 theta/tau and tBID to be significantly associated with chemotherapy resistance. CONCLUSIONS: For the first time, antibody microarrays have been used to identify proteins associated with chemotherapy resistance using fresh breast cancer tissue. We propose a potential role for 14-3-3 theta/tau and tBID as predictive biomarkers of neoadjuvant chemotherapy resistance in breast cancer. Further validation in a larger sample series is now required.

Differential proteomics in the search for biomarkers of radiotherapy resistance.

The individualization of radiotherapy treatment would be beneficial for cancer patients; however, there are no predictive biomarkers of radiotherapy resistance in routine clinical use. This article describes the body of work in this field where comparative proteomics methods have been used for the discovery of putative biomarkers associated with radiotherapy resistance. A large number of differentially expressed proteins have been reported, mostly from the study of novel radiotherapy-resistant cell lines. Here, we have assessed these putative biomarkers through the discovery, confirmation and validation phases of the biomarker pipeline, and inform the reader on the current status of proteomics-based findings. Suggested avenues for future work are discussed.

A pilot study to investigate the role of the 26S proteasome in radiotherapy resistance and loco-regional recurrence following breast conserving therapy for early breast cancer.

Breast conserving therapy is a currently accepted method for managing patients with early stage breast cancer. However, approximately 7% of patients may develop loco-regional tumour recurrence within 5 years. We previously reported that expression of the 26S proteasome may be associated with radio-resistance. Here we aimed to analyse the 26S proteasome in a pilot series of early breast cancers and correlate the findings with loco-regional recurrence. Fourteen patients with early breast cancer who developed loco-regional recurrence within 4 years of completing breast conserving therapy were selected according to strict criteria and compared with those from 14 patients who were disease-free at 10 years. Decreased expression of the 26S proteasome was significantly associated with radio-resistance, manifested as the development of a loco-regional recurrence within 4 years of breast conserving therapy (p = 0.018). This small pilot study provides further suggestion that the 26S proteasome may be associated with response to radiotherapy.

Repeatedly identified differentially expressed proteins (RIDEPs) from antibody microarray proteomic analysis.

Antibody microarrays are powerful new tools in the field of comparative proteomics. The success of the biomarker discovery pipeline relies on the quality of data generated in the discovery phase and careful selection of proteins for the verification phase. Recent meta-analyses found a number of repeatedly identified differentially expressed proteins (RIDEPs) from mass spectrometry-based proteomics research in a range of species. We aimed to assess RIDEPs based on antibody microarray data-sets. A total of 13 independent experiments encompassing a range of oncology-related research on human tissue, cells or cell lines from 5 distinct sample groups were performed utilising a commercial 725 antibody microarray platform (Panorama XPRESS Profiler725; Sigma-Aldrich). Analysis of all microarray slides was carried out by the same individual to reduce inter-observer variability. Fold changes of ≥1.8 were considered significant. A total of 13 RIDEPs were seen, each appearing in at least 4/13 (30%) antibody microarray analyses from at least 2 out of 5 experimental sample groups. The phenomenon of RIDEPs may exist in antibody microarray proteomics and we report a preliminary list of 13 RIDEPs from the XPRESS Profiler725 platform. This information will be useful when interpreting experimental data and considering which DEPs should be prioritised for verification.

Targeted epidermal growth factor receptor therapy in malignant pleural mesothelioma: where do we stand?

The median survival for patients with malignant pleural mesothelioma remains extremely poor and there is a need for the development of more effective treatment modalities. The epidermal growth factor receptor is frequently over-expressed in malignant pleural mesothelioma samples and therefore may be a potential therapeutic target. Targeted EGFR therapy has been successful in non-small cell lung cancer using small molecule tyrosine kinase inhibitors and in colorectal cancer using monoclonal anti-EGFR antibodies. However, phase II clinical trials based on EGFR tyrosine kinase inhibitor therapy have so far not shown promise in mesothelioma. This review includes a background to targeted EGFR treatment strategies, explores putative therapy resistance mechanisms, including the role of predictive biomarkers, and describes the current status of targeted EGFR therapeutic strategies for mesothelioma patients.

Biomarkers of chemotherapy resistance in breast cancer identified by proteomics: current status.

This review describes and discusses the advantages and limitations of proteomic approaches in the identification of biomarkers associated with chemotherapy resistance. Both gel-based (two-dimensional polyacrylamide gel electrophoresis) and gel-free (shotgun and quantitative) mass spectrometry approaches are discussed. Non-mass spectrometry approaches including antibody microarray platforms are described as complementary proteomic strategies. Methods for technical confirmation and clinical validation of putative biomarkers are presented. Use of this proteomic toolbox in the quest for biomarkers of chemotherapy resistance in breast cancer is reviewed. Technical aspects of sample selection, acquisition, storage and analysis are discussed and putative biomarkers identified through proteomic approaches are presented.