Fragmentomic analysis of circulating tumor DNA-targeted cancer panels.

BACKGROUND: The isolation of cell-free DNA (cfDNA) from the bloodstream can be used to detect and analyze somatic alterations in circulating tumor DNA (ctDNA), and multiple cfDNA-targeted sequencing panels are now commercially available for Food and Drug Administration (FDA)-approved biomarker indications to guide treatment. More recently, cfDNA fragmentation patterns have emerged as a tool to infer epigenomic and transcriptomic information. However, most of these analyses used whole-genome sequencing, which is insufficient to identify FDA-approved biomarker indications in a cost-effective manner. PATIENTS AND METHODS: We used machine learning models of fragmentation patterns at the first coding exon in standard targeted cancer gene cfDNA sequencing panels to distinguish between cancer and non-cancer patients, as well as the specific tumor type and subtype. We assessed this approach in two independent cohorts: a published cohort from GRAIL (breast, lung, and prostate cancers, non-cancer, n = 198) and an institutional cohort from the University of Wisconsin (UW; breast, lung, prostate, bladder cancers, n = 320). Each cohort was split 70%/30% into training and validation sets. RESULTS: In the UW cohort, training cross-validated accuracy was 82.1%, and accuracy in the independent validation cohort was 86.6% despite a median ctDNA fraction of only 0.06. In the GRAIL cohort, to assess how this approach performs in very low ctDNA fractions, training and independent validation were split based on ctDNA fraction. Training cross-validated accuracy was 80.6%, and accuracy in the independent validation cohort was 76.3%. In the validation cohort where the ctDNA fractions were all <0.05 and as low as 0.0003, the cancer versus non-cancer area under the curve was 0.99. CONCLUSIONS: To our knowledge, this is the first study to demonstrate that sequencing from targeted cfDNA panels can be utilized to analyze fragmentation patterns to classify cancer types, dramatically expanding the potential capabilities of existing clinically used panels at minimal additional cost.

Targeting AKT/PKB to improve treatment outcomes for solid tumors.

The serine/threonine kinase AKT, also known as protein kinase B (PKB), is the major substrate to phosphoinositide 3-kinase (PI3K) and consists of three paralogs: AKT1 (PKBα), AKT2 (PKBß) and AKT3 (PKBγ). The PI3K/AKT pathway is normally activated by binding of ligands to membrane-bound receptor tyrosine kinases (RTKs) as well as downstream to G-protein coupled receptors and integrin-linked kinase. Through multiple downstream substrates, activated AKT controls a wide variety of cellular functions including cell proliferation, survival, metabolism, and angiogenesis in both normal and malignant cells. In human cancers, the PI3K/AKT pathway is most frequently hyperactivated due to mutations and/or overexpression of upstream components. Aberrant expression of RTKs, gain of function mutations in PIK3CA, RAS, PDPK1, and AKT itself, as well as loss of function mutation in AKT phosphatases are genetic lesions that confer hyperactivation of AKT. Activated AKT stimulates DNA repair, e.g. double strand break repair after radiotherapy. Likewise, AKT attenuates chemotherapy-induced apoptosis. These observations suggest that a crucial link exists between AKT and DNA damage. Thus, AKT could be a major predictive marker of conventional cancer therapy, molecularly targeted therapy, and immunotherapy for solid tumors. In this review, we summarize the current understanding by which activated AKT mediates resistance to cancer treatment modalities, i.e. radiotherapy, chemotherapy, and RTK targeted therapy. Next, the effect of AKT on response of tumor cells to RTK targeted strategies will be discussed. Finally, we will provide a brief summary on the clinical trials of AKT inhibitors in combination with radiochemotherapy, RTK targeted therapy, and immunotherapy.

Improved survival with dose-escalated radiotherapy in stage III non-small-cell lung cancer: analysis of the National Cancer Database.

BACKGROUND: Concurrent chemoradiation is the standard of care in non-operable stage III non-small-cell lung cancer (NSCLC). Data have suggested a benefit of dose escalation; however, results from the randomized dose-escalation trial RTOG 0617 revealed a lower survival rate with high-dose radiation. To evaluate the impact of dose escalation on overall survival (OS) in stage III NSCLC treated with chemoradiotherapy outside the controlled setting of a randomized trial, we carried out an observational, population-based investigation of the National Cancer Database (NCDB). PATIENTS AND METHODS: A total of 33 566 patients with stage III NSCLC treated with chemoradiation from 2004 to 2012 and radiation doses between 59.4 and 85 Gy were included. The primary end point was OS, with median survival calculated via Kaplan-Meier. Univariate, multivariable and propensity-score matching analyses were carried out. RESULTS: Patients were stratified by dose with median OS of: 18.8, 19.8 and 21.6 months for cohorts receiving 59.4-60, 61-69 and ≥70 Gy, respectively (P < 0.001). Granular dose analyses were carried out demonstrating increased OS with increasing radiation dose: median survival of 18.8, 21.1, 22.0 and 21.0 months for 59.4-60, 66, 70 and ≥71 Gy, respectively. While 66, 70 and ≥71 Gy resulted in increased OS in comparison with 59.4-60 Gy, no significant difference in OS was observed when comparing 66 with ≥71 Gy (P = 0.38). CONCLUSIONS: Dose escalation above 60 Gy was associated with improved OS in this cohort of stage III NSCLC patients treated with chemoradiotherapy. A plateau of benefit was observed, with no additional improvement in OS with increased dose (≥71 Gy) compared with 66-70 Gy. With evidence suggesting worse OS and quality of life with increased dose, these data support investigation of the role of intermediate-dose radiation, and in the absence of randomized evidence, may be leveraged to justify utilization of intermediate-dose radiation.

Cetuximab and bevacizumab: preclinical data and phase II trial in recurrent or metastatic squamous cell carcinoma of the head and neck.

BACKGROUND: We evaluated combined targeting with cetuximab, an anti-epidermal growth factor receptor (EGFR) monoclonal antibody, and bevacizumab, an anti-vascular endothelial growth factor (VEGF) monoclonal antibody, in squamous cell carcinoma of the head and neck (SCCHN). PATIENTS AND METHODS: The combination was studied in human endothelial cells and head and neck and lung cancer xenograft model systems. Patients with recurrent or metastatic SCCHN were treated with weekly cetuximab and bevacizumab, 15 mg/kg on day 1 given intravenously every 21 days, until disease progression. Analysis of tumor biomarkers and related serum cytokines was performed. RESULTS: Cetuximab plus bevacizumab enhanced growth inhibition both in vitro and in vivo, and resulted in potent reduction in tumor vascularization. In the clinical trial, 46 eligible patients were enrolled. The objective response rate was 16% and the disease control rate 73%. The median progression-free survival and overall survival were 2.8 and 7.5 months, respectively. Grade 3-4 adverse events were expected and occurred in less than 10% of patients. transforming growth factor alpha, placenta-derived growth factor, EGFR, VEGFR2 increased and VEGF decreased after treatment but did not correlate with treatment efficacy. CONCLUSIONS: Cetuximab and bevacizumab are supported by preclinical observations and are well tolerated and active in previously treated patients with SCCHN.

Wound healing following combined radiation and cetuximab therapy in head and neck cancer patients.

OBJECTIVE: This study set out to determine if cetuximab treatment increases the risk of wound healing complications when combined with radiation therapy. METHOD: We performed a retrospective chart review of head and neck cancer patients who received salvage neck dissections between 1999 and 2007, at two academic tertiary care centres. Complications from wound healing were compared between radiation and combined therapy groups. RESULTS: A total of 35 patients received radiation (n=20) or combined radiation and cetuximab therapy (n=15) prior to neck dissection. The treatment groups were similar in regard to demographic and primary tumour-related characteristics. The time between treatment and salvage neck dissection did not differ between the radiation (3.9 months) and combination treatment (3.0 months) groups (p=0.15). Wound healing complications occurred in 13% (2/15) of the patients treated with radiation and cetuximab and there were no complications in patients who received radiation alone (p=0.20). CONCLUSION: Cetuximab did not significantly increase the risk of post-surgical wound complications, although a higher absolute number of wound complications was observed in the group treated with cetuximab and radiation therapy, compared with the group treated with radiation alone. CONFLICT OF INTEREST: This work was supported by a grant from the National Institute of Health (2T32 CA091078-06). One of the authors, JAB, is an occasional consultant and honoraria for ImClone and Bristol-Meyers Squibb.

Mechanisms of acquired resistance to cetuximab: role of HER (ErbB) family members.

The epidermal growth factor receptor (EGFR) is a central regulator of proliferation and progression in human cancers. Five EGFR inhibitors, two monoclonal antibodies and three TKIs, have recently gained FDA approval in oncology (cetuximab, panitumumab, erlotinib, gefitinib and lapatinib). These strategies of EGFR inhibition demonstrate major tumor regressions in approximately 10-20% of advanced cancer patients. However, many tumors eventually manifest acquired resistance to treatment. In this study we established and characterized a model to study molecular mechanisms of acquired resistance to the EGFR monoclonal antibody cetuximab. Using high-throughput screening we examined the activity of 42 receptor tyrosine kinases in resistant tumor cells following chronic exposure to cetuximab. Cells developing acquired resistance to cetuximab exhibited increased steady-state EGFR expression secondary to alterations in trafficking and degradation. In addition, cetuximab-resistant cells manifested strong activation of HER2, HER3 and cMET. EGFR upregulation promoted increased dimerization with HER2 and HER3 leading to their transactivation. Blockade of EGFR and HER2 led to loss of HER3 and PI(3)K/Akt activity. These data suggest that acquired resistance to cetuximab is accompanied by dysregulation of EGFR internalization/degradation and subsequent EGFR-dependent activation of HER3. Taken together these findings suggest a rationale for the clinical evaluation of combinatorial anti-HER targeting approaches in tumors manifesting acquired resistance to cetuximab.

Promising new advances in head and neck radiotherapy.

Efforts to improve the efficacy of treatment for SCCHN have led to the use of multimodality approaches with combinations of surgery, radiotherapy and chemotherapy. Conventional head and neck radiotherapy, a standard approach for locoregionally advanced disease, is associated with a variety of well-known acute and long-term toxicities. These chronic toxicities (i.e. xerostomia, dysphagia, fibrosis) can impact negatively on patient quality of life. Altered radiation fractionation regimens that incorporate acceleration and/or hyperfractionation can improve locoregional control but also increase acute toxicities for head and neck cancer patients. Intensity modulated radiation therapy (IMRT) has emerged as a promising method for delivering effective radiation dose to head and neck tumour targets while reducing exposure of surrounding healthy tissue. Another method for improving head and neck cancer outcome with conventional radiotherapy is with the concurrent addition of chemotherapy. Indeed, chemoradiotherapy is now a standard treatment approach for locoregionally advanced disease. Molecular targeted agents, such as the epidermal growth factor receptor (EGFR) antagonist, cetuximab (Erbitux), have recently been shown to enhance the effects of radiotherapy, and reports to date suggest that this potentiation occurs without an increase in the characteristic toxicities associated with head and neck radiation.

Intensity-modulated radiation therapy: emerging cancer treatment technology.

The use of intensity-modulated radiation therapy (IMRT) is rapidly advancing in the field of radiation oncology. Intensity-modulated radiation therapy allows for improved dose conformality, thereby affording the potential to decrease the spectrum of normal tissue toxicities associated with IMRT. Preliminary results with IMRT are quite promising; however, the clinical data is relatively immature and overall patient numbers remain small. High-quality IMRT requires intensive physics support and detailed knowledge of three-dimensional anatomy and patterns of tumour spread. This review focuses on basic principles, and highlights the clinical implementation of IMRT in head and neck and prostate cancer.

Epidermal growth factor receptor inhibition strategies in oncology.

Molecular targeting strategies for cancer therapy are distinct from conventional chemotherapy and radiotherapy in their potential to provide increased tumor specificity. One particular molecular target of high promise in oncology is the epidermal growth factor receptor (EGFR). The EGFR is overexpressed, dysregulated or mutated in many epithelial malignancies, and EGFR activation appears important in tumor growth and progression. Advances in signal transduction biology continue to sharpen our understanding regarding specific contributions of EGFR signaling networks to cancer behavior. Two predominant classes of EGFR inhibitors have been developed including monoclonal antibodies (mAbs) that target the extracellular domain of EGFR, such as cetuximab (Erbitux), and small molecule tyrosine kinase inhibitors (TKIs) that target the receptor catalytic domain of EGFR, such as gefitinib (Iressa) and erlotinib (Tarceva). Mechanisms of action for EGFR inhibitors have been investigated in preclinical model systems. Safety, activity, pharmacokinetics and pharmacodynamics have been assessed in clinical trials. The anti-EGFR mAbs and TKIs have partially overlapping toxicity profiles, but distinct routes of administration, serum half-lives and therefore dosing schedules. Both classes of agents show clear antitumor activity, and cetuximab and gefitinib have been recently FDA approved for colorectal and lung cancer indications respectively. However, the absence of survival benefit for EGFR TKIs in combination with chemotherapy in large-scale phase III lung cancer trials in 2003 underscores a major challenge in anti-EGFR oncology therapeutics; namely to identify those tumors and patients that will respond predictably to EGFR inhibitor approaches. Newly identified mutations in the EGFR catalytic domain that appear to confer sensitivity to EGFR TKIs promise to open new doors of investigation regarding response prediction. Advances will also require enhanced molecular understanding of the overall EGFR signaling network, and improved methods to gauge the dependence of individual tumors on EGFR signaling pathways for growth advantage. Results from newly reported phase III trials in 2004 now confirm a survival advantage for the use of EGFR inhibitors in combination with high-dose radiation in head and neck cancer, and in refractory lung cancer respectively. It appears likely that EGFR inhibitors (and other rationally designed molecular growth inhibitors) will play a meaningful role in cancer therapy in the years to come.

IMC-C225, an anti-epidermal growth factor receptor monoclonal antibody, for treatment of head and neck cancer.

Squamous cell carcinoma (SCC) of the head and neck (H&N) remains a clinical challenge due to its high rate of locoregional disease recurrence. The importance of the epidermal growth factor receptor (EGFR) in the development and progression of many solid tumours (including SCC of the H&N) is well understood; increased expression is associated with enhanced tumour invasion, resistance to chemotherapy and decreased patient survival. Several approaches have been developed to achieve EGFR blockade as an anticancer treatment strategy, including an anti-EGFR monoclonal antibody (mAb), IMC-C225, which competitively binds to the extracellular receptor site to prevent binding by natural EGFR ligands (EGF and TGF-alpha). Preclinical studies evaluating this chimeric mAb in human cancer cell lines in vitro and human tumour xenografts in vivo have demonstrated its potent antitumour activity. The clinical efficacy of IMC-C225 appears to involve multiple anticancer mechanisms, including inhibition of cell cycle progression, induction of apoptosis, anti-angiogenesis, inhibition of metastasis and its ability to enhance the response to chemotherapy and radiation therapy. Phase I studies of IMC-C225 combined with chemotherapy or radiation for SCC of the H&N demonstrate excellent response rates in patients with recurrent or refractory disease. Phase II and III trials examining the efficacy and safety of these combinations are currently underway. To date, IMC-C225 has been well-tolerated, with skin rashes and allergic reactions being the most clinically important adverse events reported. IMC-C225 displays dose-dependent elimination characteristics and a half-life of approximately 7 days. Current recommendations for dosing include a 400 mg/m2 loading dose, followed by weekly infusions of 250 mg/m2.

Radiation response modification following molecular inhibition of epidermal growth factor receptor signaling.

The epidermal growth factor receptor (EGFR) has emerged as a central molecular target for modulation in cancer therapeutics. The correlation between overexpression of EGFR and clinically aggressive malignant disease renders EGFR a promising therapy target for many epithelial tumors, which represent approximately two thirds of all human cancers. Although the initial impetus for examining EGFR signal interruption as an anticancer strategy involved proliferative growth inhibition, more recent studies now confirm the capacity of EGFR down-regulation to modify apoptosis, invasion capacity, angiogenesis, DNA damage repair, and cellular response to radiation and selected chemotherapy agents. The favorable interaction profile for EGFR blocking agents combined with radiation and/or chemotherapy has stimulated clinical trials in diverse anatomic sites including head and neck, colorectal, pancreas, and lung. Among the most well studied and promising current agents for EGFR signal modulation are C225 and ZD1839. C225 is a chimeric monoclonal antibody to the EGFR (extracellular domain), whereas ZD1839 is a selective inhibitor of the EGFR-tyrosine kinase (cytoplasmic domain). The spectrum of cellular and biological effects that follow molecular blockade of the EGFR is enlarging and reflect the central role of this receptor in regulating epithelial cell behavior. Molecular inhibition of EGFR signaling in combination with radiation represents a highly promising investigational arena. A preview of current translational research efforts and early clinical trials focused primarily on radiation interaction is provided herein.

Multiple daily fractionation radiotherapy schedules in lung cancer.

Lung cancer is the number one worldwide cancer killer, and in spite of therapeutic advances, the overall impact on survival has remained very modest. For both small and non-small-cell lung cancer, treatment trends have shifted toward combined-modality approaches, chemotherapy for the control of systemic micrometastases, and radiotherapy for intrathoracic control. However, on both counts, rates of failure remain unacceptably high, and several novel strategies are currently being explored. The use of altered fractionation, including multiple daily fractions, reflects one approach for modifying radiotherapy. The two most common approaches are hyperfractionation and acceleration, the former designed to reduce late normal tissue toxicities and the latter to counteract accelerated tumor repopulation. Recent randomized trials suggest that such approaches may result not only in lowered rates of intrathoracic failure but also in improved survival.

Head and neck cancer as a clinical model for molecular targeting of therapy: combining EGFR blockade with radiation.

PURPOSE/OBJECTIVE: The primary purpose of this presentation is to develop the concept that molecular blockade of specific growth factor receptors and signal transduction pathways in combination with radiation will prove a valuable cancer therapeutic strategy. More specifically, the rationale for molecular blockade of the epidermal growth factor receptor (EGFR) system in combination with ionizing radiation for epithelial tumors, such as squamous cell carcinomas (SCCs) of the head and neck (H&N), is described. METHODS AND MATERIALS: Preclinical experimentation with in vitro and in vivo model systems regarding the capacity of EGFR blockade, using the monoclonal antibody C225, to modulate SCC tumor growth behavior and response to radiation is presented. The rationale for new clinical trials that are currently exploring this concept are presented. RESULTS: Blockade of the EGFR system in SCC cell lines with C225 induces G1 cell cycle arrest with an associated decrease in the S-phase fraction. Inhibition of tumor cell proliferation is readily measured following C225 exposure and the corresponding alterations in expression of key regulators of the G1-S cell cycle phase transition are identified. Exposure of SCCs to C225 in culture enhances radiosensitivity following single-dose radiation exposure. Profound augmentation of the in vivo radiation response of SCC tumor xenografts in athymic mice is similarly demonstrated following systemic administration of C225. Preliminary studies are presented regarding potential underlying mechanisms of action for this enhanced tumor response to the combination of C225 and radiation including: (a) proliferative growth inhibition, (b) enhancement of radiation-induced apoptosis, (c) inhibition of damage repair, and (d) downregulation of tumor angiogenic response. Preliminary observations from the Phase III multicenter clinical trial examining C225 plus radiation therapy for advanced H&N cancer patients are provided. CONCLUSION: Molecular inhibition of the EGFR signal transduction system in combination with radiation represents a promising investigational area in cancer therapeutics. Epithelial tumors that are rich in their expression of EGFR (e.g., SCC of the H&N) hold special promise for receptor blockade approaches. More broadly, the ultimate therapeutic effect of selected molecular agents which block specific growth factor receptors and signaling pathways may be enhanced when delivered in combination with radiation.

Modulation of radiation response after epidermal growth factor receptor blockade in squamous cell carcinomas: inhibition of damage repair, cell cycle kinetics, and tumor angiogenesis.

We have recently demonstrated that molecular blockade of the epidermal growth factor receptor with the anti-epidermal growth factor receptor (EGFR) monoclonal antibody C225 enhances the in vitro radiosensitivity of human squamous cell carcinomas (SCCs) derived from the head and neck. In the present study, we further investigated the capacity of C225 to modulate the in vitro and in vivo radiation response of human SCC tumor cells and xenografts, and we examined several potential mechanisms that may contribute to the enhanced radiation response induced by C225. Tumor xenograft studies demonstrated complete regression of both newly established (20 mm3) and well-established (100 mm3) SCC tumors over a 55-100 day follow-up period in athymic mice treated with the combination of C225 (i.p. injection) and radiation. Cell cycle analysis via flow cytometry confirmed that combined treatment with C225 and radiation induced an accumulation of cells in the more radiosensitive cell cycle phases (G1, G2-M) with concurrent reduction in the proportion of cells in the more radioresistant S phase. Results from sublethal damage repair and potentially lethal damage repair analyses in cultured SCC cells demonstrated a strong inhibitory effect of C225 on postradiation damage repair. Further, exposure of SCC cells to C225 induced a redistribution of DNA-dependent protein kinase from the nucleus to the cytosol, suggesting one potential mechanism whereby C225 may influence the cellular response to radiation. Immunohistochemical analysis of SCC tumor xenografts after systemic administration of C225 demonstrated inhibition of the in vivo expression of tumor angiogenesis markers, including vascular endothelial growth factor and Factor VIII. Taken together, the collective data suggest that the profound in vivo antitumor activity identified in the xenograft setting when C225 is combined with radiation derives from more than simply the antiproliferative and cell cycle effects of EGFR system inhibition. In addition to antiproliferative growth inhibition, EGFR blockade with C225 appears to influence the capacity of human SCCs to effect DNA repair after exposure to radiation, and to express classic markers of tumor angiogenesis.

Modulation of tumor cell proliferation and apoptosis by polyamine depletion in cells of head and neck squamous cell carcinomas.

These studies were carried out to examine the capacity of alpha-difluoromethylornithine (DFMO) to modulate cell proliferation and apoptosis in cells of squamous cell carcinomas (SCCs) of the head and neck. Exposure of cells to DFMO (5 mM for 48 h) depleted intracellular putrescine and spermidine levels (greater than 5-fold) and inhibited proliferation of the cells without manifestation of cytotoxicity as measured by a clonogenic assay. Exposure of the cells to DFMO did not influence the survival response after exposure to single-dose radiation between 0 and 10 Gy. Treatment of polyamine-depleted cells with 200 nM staurosporine amplified apoptosis 65% (1.65-fold) over that in controls, as determined by flow cytometry. The increased apoptosis after DFMO treatment was effectively inhibited by the addition of 1 mM putrescine or spermidine. Cleavage of poly(ADP-ribose) polymerase (PARP) illustrated that the staurosporine treatment induced apoptosis in the cells within 6 h. Analysis of PARP cleavage indicated that treatment with DFMO accelerated the kinetics of progression of apoptosis but did not influence the sensitivity of cells to 10 nM-1 microM staurosporine. These data suggest an involvement of endogenous polyamines in modulation of proliferation kinetics and apoptosis in human SCCs and suggest opportunities to explore new therapeutic strategies in head and neck cancer patients to be treated with radiation therapy.

Epidermal growth factor receptor blockade with C225 modulates proliferation, apoptosis, and radiosensitivity in squamous cell carcinomas of the head and neck.

We examined effects of the anti-epidermal growth factor receptor monoclonal antibody C225 on proliferation, cell cycle phase distribution, apoptosis, and radiosensitivity in squamous cell carcinoma (SCC) cell lines derived from head and neck cancer patients. Exposure to C225 in culture inhibits SCC proliferation in a time-dependent manner, and the degree of growth inhibition, compared to controls, ranges from 20 to 75%. Flow cytometry analysis demonstrates that C225 treatment induces accumulation of cells in G1, which is accompanied by a 2-3-fold decrease in the percentage of cells in S phase. C225 exposure also induces apoptosis in SCC populations, as demonstrated by flow cytometry analysis using dual stainings of merocyanine 540 and Hoechst 33342. Western blot analysis indicates that C225 exposure induces accumulation of hypophosphorylated retinoblastoma protein and increases expression of p27KIP1. An increase in Bax expression and concurrent decrease in Bcl-2 expression are observed when SCC cells are exposed to C225. Examination of C225 effects on radiation response in SCCs demonstrates enhancement in radiosensitivity and amplification of radiation-induced apoptosis. These effects are observed in both single-dose and fractionated radiation experiments. C225 represents a promising growth-inhibitory agent that can influence cellular proliferation, apoptosis, and radiosensitivity in SCCs of the head and neck.

Epidermal growth factor receptor inhibition in cancer therapy: biology, rationale and preliminary clinical results.

The epidermal growth factor receptor (EGFR), a growth factor receptor involved in the regulation of cellular differentiation and proliferation, is highly expressed by many tumor cells. In light of a relationship between overexpression of EGFR and clinically aggressive malignant disease, EGFR has emerged as a promising target for cancer therapy. In recent years, several molecular strategies have been explored to modulate either the EGFR itself, or the downstream signal beyond the cell surface receptor. One of the most promising current strategies involves the use of anti-EGFR monoclonal antibodies (mAbs), either alone or in combination with conventional cytotoxic modalities such as chemotherapy or radiotherapy. This review focuses primarily on recent progress in the development of anti-EGFR mAbs, and examines their potential in the treatment of cancer.