Oral Oncology xxx (2015) xxx–xxx

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Oral Oncology journal homepage: www.elsevier.com/locate/oraloncology

Targeting angiogenesis in head and neck cancer Maria Vassilakopoulou a, Amanda Psyrri b, Athanassios Argiris c,d,⇑ a

Royal Marsden Hospital, London, UK Attikon Hospital and Medical School of Athens, Athens, Greece c Hygeia Hospital, Athens, Greece d University of Texas Health Science Center at San Antonio, TX, USA b

a r t i c l e

i n f o

Article history: Received 4 September 2014 Received in revised form 6 January 2015 Accepted 8 January 2015 Available online xxxx Keywords: Head and neck cancer Angiogenesis Vascular endothelial growth factor Vascular endothelial growth factor receptor Targeted therapy Tyrosine kinase inhibitors Monoclonal antibodies Bevacizumab

s u m m a r y Angiogenesis is a crucial step in tumor growth and metastasis. Head and neck squamous cell carcinomas (HNSCC) highly express angiogenesis factors, such as vascular endothelial growth factor (VEGF), which are associated with patient prognosis. Antiangiogenesis agents can potentially modulate tumor microenvironment and induce radiosensitivity and chemosensitivity. In this review, we discuss the molecular mechanisms underlying angiogenesis involved in HNSCC, preclinical data with antiangiogenesis agents as well as potential predictive biomarkers. We also review novel therapies under investigation and summarize the results of clinical trials using antiangiogenesis agents alone or in combination with conventional therapies in HNSCC. Ó 2015 Elsevier Ltd. All rights reserved.

Introduction Growth and expansion of the vascular network through a process known as angiogenesis is a crucial event during the natural history of cancer since the proliferation and migration of cancer cells depend on sufficient oxygen and nutrient supply. The role of angiogenesis, a hallmark of tumorigenesis, has been investigated in many types of cancers, including squamous cell carcinoma of the head and neck (HNSCC) [1,2]. Angiogenesis constitutes an important target of anticancer treatment and antiangiogenesis agents are currently available and beneficial in the treatment of several solid tumors (Table 1). In HNSCC, angiogenesis targeting remains experimental as definitive clinical trials are still ongoing and, therefore, these agents should not be used in routine clinical practice. An understanding of the biology of HNSCC is essential for the development of these new therapies. This review focuses on the role of angiogenesis in HNSCC and elaborates on the current status and challenges in the development of antiangiogenesis therapies for HNSCC. Angiogenesis in cancer: VEGF pathway The downstream signaling of the angiogenesis pathway is mainly mediated by the production of vascular endothelial growth ⇑ Corresponding author at: Erythrou Stavrou 5, Athens 15123, Greece. E-mail address: [email protected] (A. Argiris).

factors (VEGF), a member of the platelet-derived growth factor (PDGF) superfamily, which also includes VEGF-A, VEGF-B, VEGFC, VEGF-D, VEGF-E, and placental growth factor [3] (Fig. 1). These alternative splicing-derived variants have different functions and specificity to VEGF receptors [4]. Among these factors, VEGF-A is the most common and usually referred to as VEGF. This is a vascular permeability factor produced in response to upstream activators, including growth factors, cytokines, environmental stimuli and oncogenes. Hypoxia is a major factor inducing VEGF expression through the expression of hypoxia-inducible factor-a (HIF-1a) [5] and a key regulator of tumor angiogenesis. Numerous other factors are involved in cancer neovascularization such as prostaglandins, COX-2, IL-6, PDGF and epidermal growth factor (EGF) [6]. A group of specific receptors on the surface of endothelial as well as tumor cells interact with VEGF triggering downstream angiogenesis-related signals. This group of VEGF receptors include the receptor tyrosine kinases (RTKs) VEGFR1, VEGFR2 and VEGFR3. VEGFR2 is the major VEGF tyrosine kinase receptor mediating the angiogenesis signalling pathway in endothelial cells [7]. It was originally believed that VEGF receptors are expressed on endothelial cells only but it was later demonstrated that they can be expressed on tumor cells as well [8]. The binding of VEGF ligands to their specific cell surface RTKs, such as, VEGFR-1, VEGFR-2, and VEGFR-3 results in activation of downstream signaling [9] (Fig. 1). Despite the existence of multiple variants of both VEGF

http://dx.doi.org/10.1016/j.oraloncology.2015.01.006 1368-8375/Ó 2015 Elsevier Ltd. All rights reserved.

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Table 1 Currently FDA approved antiangiogenesis agents in solid tumors (none in HNSCC). Antiangiogenesis agent

Mechanism of action

FDA approval

Bevacizumab

Humanized monoclonal antibody against VEGF

Ramucirumab Sunitinib

Fully human monoclonal antibody against VEGFR2 Multitargeted TKI, including VEGFR-1,VEGFR-2, VEGFR-3, PDGFR, RET and c-kit

Sorafenib

Multitargeted inhibitor of the serine/threonine protein kinases B-Raf, C-Raf and a TKI of VEGFR-2, -3, PDGFR, Flt-3, and c-kit Multitargeted TKI targeting EGFR, VEGFR-2 and RET VEGFR TKI of receptors 1, 2, and 3 Multitargeted TKI with activity against VEGFR, FDGFR, PDGFR, and c-kit Multitargeted TKI, including VEGFR

Colorectal cancer, NSCLC, renal cell cancer, ovarian cancer, glioblastoma, cervical cancer Gastric cancer, NSCLC GIST, pancreatic neuroendocrine tumors and metastatic renal cell cancer Advanced renal cell carcinoma, unresectable hepatocellular carcinoma and thyroid cancer Unresectable medullary thyroid cancer Advanced renal cell carcinoma Renal cell carcinoma, soft tissue sarcomas Colorectal cancer, GIST

Vandetanib Axitinib Pazopanib Regorafenib

Abbreviations: VEGF, vascular-endothelial growth factor; NSCLC, non-small cell lung cancer; TKI, tyrosine kinase inhibitor; GIST, gastrointestinal stromal tumors; VEGFR, vascular-endothelial growth factor receptor; PDGFR, platelet-derived growth factor receptor; and FDGFR, fibroblast-derived growth factor receptor.

receptors and ligands, the main angiogenesis downsteam signal is mediated by VEGF-A and VEGFR-2 [10]. VEGF signalling may affect several significant tumor functions independent of vascular permeability and neovascularization. Autocrine VEGF signalling can promote tumor cell proliferation, migration as well as cancer invasion [11,12] by activating predominant pathways in tumorigenesis, such as the MAPK and PI3K–AKT. Moreover, VEGF can affect the host immune response by interacting with the function of immune cells within the tumor microenvironment [13]. VEGF signalling may have an autocrine and paracrine effect on the function of cancer stem cells [8]. VEGF has also been implicated in chemotherapy resistance as it may induce autophagy that counteracts chemotherapy-induced stress [14]. Angiogenesis markers as prognostic factors in HNSCC High levels of VEGF expression are commonly observed in HNSCC and have been associated with disease aggressiveness and worse patient outcome [1,15,16]. In addition to VEGF, other promoters of angiogenesis, such as interleukin-8 (IL-8) and EGFR, are found in high levels in HNSCC. VEGF as well as EGFR plasma levels have been reported as potentially prognostic and predictive factors in HNSCC [1]. IL-8, a key mediator of hypoxia, along with other hypoxia-regulated cytokines and angiogenic factors (VEGF, IL-4 osteopontin, growth-related oncogene a, eotaxin, granulocyte-colony stimulating factor, and stromal cell derived factor 1a) were reported to comprise a high risk signature predictive for progression following induction chemotherapy with carboplatin, paclitaxel and cetuximab in HNSCC [17]. Another study of serum samples from patients treated with cetuximab-containing therapy showed that baseline VEGF and IL-6 are of potential prognostic significance [18]. Furthermore, Le et al. reported that plasma IL-8 is an independent prognostic factor irrespective of treatment in an analysis of large randomized trial of chemoradiotherapy with or without tirapazamine [19]. Several other proangiogenesis factors related to inflammation, hypoxia or apoptosis, such as COX2, Bax, BcL-xL, BcL-2, VEGFR/KDR, pKDR/KDR and survivin, have been related to adverse clinical outcomes [1]. Additionally, hypoxia is a key feature of locally advanced tumors and major driving force of neovascularization in a wide variety of cancers including HNSCC [5]. Hypoxia-associated transcription factor, HIF-1 a and its target proteins CA-9 and GLUT-1 are often overexpressed in HNSCC contributing to angiogenesis and worse clinical outcome [1]. Lactate is another hypoxia-related factor and its accumulation has been associated with more aggressive phenotype in many tumors, including HNSCC [1]. A gene profiling study in HNSCC tumors of 323 patients who were enrolled in a randomized study testing the hypoxic modifier

nimorazole with radiation against placebo plus radiation, uncovered a hypoxia-related gene classifier including 15 hypoxiaresponsive genes predictive of the outcome of radiotherapy with nimorazole [20]. According to this study, tumors with upregulated hypoxia-related genes showed a worse clinical outcome but a better response to treatment with the hypoxic modifier. Hence, this gene classifier might be helpful to identify patients likely to derive benefit from radiotherapy combination with hypoxia-modifying radiosensitizers [20]. A biomarker adaptation study is being conducted by DAHANCA and EORTC in p16 negative HNSCC and aims to answer the question of whether hypoxic gene classifier positive HNSCC derive benefit from the addition of nimorazole to chemoradiotherapy (NCT01880359). Another important aspect of HNSCC biology is the role of immune response in tumor microenvironment which may be stimulated by antiangiogenesis-induced vascular normalization and can subsequently enhance immunotherapy response against cancer cells [21]. Hence, the level of tumor-cytotoxic CD8+ has been described as a potential biomarker for vascular normalization and response to antiangiogenesis treatment [22]. VEGF and angiogenesis as therapeutic targets The functional significance of VEGFs and their receptors has provided opportunities for the development of new therapeutic agents and strategies. These approaches can potentially promote tumor regression, reduce the probability of recurrence and enhance the response to standard chemotherapy and radiotherapy [8]. So far, these therapeutic approaches have been based on either antibody-mediated inhibition of VEGF or VEGFR, or inhibition of VEGF RTK activity using tyrosine kinases inhibitors (Fig. 1). In a study in head and neck cancer cell lines and xenograft models, bevacizumab in combination with radiation showed significantly decreased angiogenesis, inhibition of tumor growth and increased tumor cell apoptosis compared to radiation alone [23]. A study evaluating bevacizumab in combination with the EGFR-TKI erlotinib and radiation in a head and neck cancer orthotopic model demonstrated that radiation alone induced increased angiogenesis, whereas combination therapy led to increased tumor inhibition [24]. These observations suggest that activation of EGFR upregulates VEGF inducing resistance to EGFR inhibitors and support the rationale for several studies that evaluated the combination of anti-EGFR and anti-VEGF therapy in HNSCC [25,26]. Interactions with chemotherapy and radiation Anti-VEGF therapies can normalize tumor vessels presumably leading to increased delivery of chemotherapy. This is an

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mAb VEGF

(bevacizumab)

VEGFR

mAb (ramucirumab)

Cell Membrane

VEGFR TKIs

RAS

PI3K

STAT3

RAF

AKT

cycD1

MAPK

mTOR

Bcl-xL

cell survival

cell proliferation

(vandetanib, sunitinib, sorafenib, axitinib, pazopanib, regorafenib)

apoptosis Endothelial Cell

vascular permeability

cell migration

angiogenesis

Fig. 1. Inhibition of the VEGF signaling pathway. Modified from Hsu et al. [1], mAb, monoclonal antibody TKIs, tyrosine kinase inhibitors.

important concept that potentially explains the effectiveness of concurrent administration of anti-VEGF therapies and other agents and was first introduced by Jain [27,28]. Studies in the laboratory [29] as well as in patients with rectal cancer undergoing treatment with bevacizumab [30,31] demonstrated that blocking VEGF could normalize tumor vessels and lower interstitial fluid pressure. Similar findings were seen in patients with glioblastoma treated with cediranib, an oral VEGFR inhibitor [32]. Interactions of antiangiogenesis agents with radiation have been tested in various tumor models. Anti-VEGF therapy may potentially enhance the effect of radiotherapy on tumor vasculature. It has been reported that antiangiogenesis treatment can prevent revascularization after radiation treatment decreasing the interstitial fluid pressure and improving blood perfusion and chemotherapy distribution within the tumor [33]. Furthermore, these agents improve oxygenation, increase active oxygen species and free radicals leading to more effective tumor cell damage and apoptosis [4]. The upregulation of angiogenesis factors, such as EGF and VEGF, was described as an epithelial tumor response to radiation that is associated with increased tumor cell proliferation after radiotherapy [34,35]. It has also been shown that these growth factors mediate radiation resistance [36,37]. As a result, high VEGF levels in HNSCC can play radioprotective role which makes radiation less effective and contributes to radioresistance [38]. It appears that combining antiangiogenesis drugs with radiotherapy may have additive or synergistic effects in HNSCC [34,39] through several mechanisms, including inhibition of tumor neovascularization and improvement of oxygenation leading to increase of oxygeninduced free radicals and higher response to radiation [1].

Clinical data: recurrent or metastatic HNSCC Bevacizumab A number of clinical trials have examined the addition of bevacizumab to other targeted agents or chemotherapy for the treatment of recurrent or metastatic HNSCC (Table 2). An appealing strategy is the dual inhibition of VEGFR and EGFR pathways. VEGF-mediated angiogenesis represents a potential mechanism of resistance to anti-EGFR therapy, thus, dual

inhibition may overcome resistance. Two clinical studies have examined the combination of bevacizumab with an EGFR inhibitor (erlotinib or cetuximab) in patients with recurrent or metastatic HNSCC [25,26]. Cohen et al. explored dual EGFR/VEGFR inhibition with synchronous bevacizumab and erlotinib in a phase I/II study in patients with recurrent or metastatic HNSCC [26]. In the phase II study that enrolled 48 patients and employed erlotinib 150 mg daily and bevacizumab 15 mg/kg every 3 weeks, the objective response rate was 15%, the median progression-free survival 4.1 months, and the median overall survival 7.1 months. Three patients experienced grade 3 or worse bleeding (one fatal). Biomarker analysis suggested that the clinical benefit may be greater with higher ratios of tumour-cell phosphorylated VEGF receptor-2 (pVEGFR2) over total VEGFR2 and endothelial-cell pEGFR over total EGFR in pretreatment biopsies. Argiris et al. assessed cetuximab and bevacizumab in human endothelial cells as well as head and neck and lung cancer xenograft model systems, and conducted a phase II study of this combination in 48 patients with recurrent or metastatic HNSCC [25]. Dual EGFR/VEGFR inhibition enhanced growth inhibition both in vitro and in vivo, and resulted in potent reduction in tumor vascularization In the clinical study, the objective response rate was 16% and the disease control rate 73%, with a median progressionfree survival and overall survival of 2.8 and 7.5 months, respectively. Grade 3–4 adverse events were expected and occurred in less than 10% of patients. The same group of investigators evaluated the combination of pemetrexed and bevacizumab in 40 previously untreated patients with recurrent or metastatic HNSCC [40]. The study showed promising results in terms of overall survival (median of 11.3 months), progression-free survival (median of 5 months) and objective response rate (30%) but also reported a significant rate of serious bleeding events (grade 3–5 events, 15%; 2 fatal). In contrast with cetuximab and bevacizumab only 4% of patients had grade 3 bleeding, without grade 4–5 events [25]. Bevacizumab studies in advanced non-small cell lung cancer have shown unacceptable rates of fatal bleeding in patients with squamous cell histology that prompted the exclusion of these patients from the pivotal phase III trial (E4599) which led to regulatory approval of bevacizumab in non-squamous non-small cell lung cancer. Given this concern and due to the fact that tumorrelated bleeding is not uncommon in the natural history of HNSCC, controlled randomized clinical trials will be necessary to evaluate

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Table 2 Selected completed phase II trials with angiogenesis targeting agents in head and neck cancer. Antiangiogenesis agent

Other modalities and agents in the regimen

Disease setting/Number of patients

Efficacy results

Author/year

Bevacizumab

RT/5-FU/hydroxyurea/bevacizumab vs RT/5-FU/ hydroxyurea

RT/docetaxel/bevacizumab

Locally advanced 30

Two-year OS 68% (58% with bevacizumab; 89% without bevacizumab) 2-year PFS rate 75.9%/2-year OS rate 88% 3-year PFS 62%/3-year OS 68%

Salama et al. 2011 [49]

RT/cisplatin/bevacizumab

Locally advanced; randomized 26 (19 with bevacizumab; 7 without bevacizumab) Locally advanced 42

Induction chemotherapy (paclitaxel, carboplatin, 5-FU and bevacizumab) followed by RT, paclitaxel, bevacizumab, and erlotinib RT/cisplatin/erlotinib/bevacizumab

Locally advanced 60

3-year PFS rate 71%/OS rate 82%,

Locally advanced 29

Pemetrexed/bevacizumab

Rec/Met 40

Erlotinib/bevacizumab

Rec/Met 48

Cetuximab/bevacizumab

Rec/Met 48

3-year OS 86%/3-year locoregional control 85% Median TTP 5 months/median OS 11.3 months Median PFS 4.1 months/median OS 7.1 months Median PFS 2.8/median OS 7.5 months

Sorafenib

Rec/Met; up to 2 lines of prior therapy 27 Rec/Met; 1st line 41

Median time to progression 1.8 months/median OS 4.2 months Median PFS 4 months/median OS 9 months

Elser et al. 2007 [41] Williamson et al. 2010 [42]

Sunitinib

Rec/Met, up to 2 lines of prior therapy; PS 0–1: 15 patients; PS 2: 7 patients Rec/Met; 1st line 17

For PS 0–1 and PS 2 median time to progression 8.4 and 10.5 weeks/ median OS 21 and 19 weeks Median PFS 2.3 mo

Choong et al. 2010 [44] Fountzilas et al. 2010 [45]

Sunitinib

Rec/Met; 2nd line 38

Median OS 4 mo Median PFS 2 mo

Sorafenib

Sorafenib

Sunitinib

Sunitinib

Fury et al. 2012 [52] Yao et al. 2014 [53] Hainsworth et al. 2011 [50] Yoo et al. 2012 [51] Argiris et al. 2011 [40] Cohen et al. 2009 [26] Argiris et al. 2013 [25]

Machiels et al. 2010 [46]

Median OS 3.4 mo Abbreviations: RT, radiotherapy; 5-FU, 5-fluorouracil; Rec/Met, recurrent or metastatic; PFS, progression-free survival; OS, overall survival; and PS, performance status.

any increased risk for bleeding and other complications from the addition of bevacizumab to chemotherapy in the setting of recurrent or metastatic HNSCC. An ongoing phase III randomized trial by the ECOG is comparing platinum doublets (cisplatin or carboplatin plus either 5-FU or docetaxel) with or without bevacizumab (Supplementary figure). The primary endpoint is overall survival and the accrual goal is 400 patients (NCT00588770). The study is closely monitored for the incidence of serious adverse events in both arms and is expected to complete accrual in early 2015. Tyrosine kinase inhibitors Sorafenib has been studied as monotherapy in phase II clinical trials in HNSCC [41,42] (Table 2). In a phase II trial by Elser et al. the use of single-agent sorafenib in patients with recurrent or metastatic HNSSC or nasopharyngeal carcinoma having received up to two progression of 1.8 months and median overall survival of 4.2 months [41]. Another phase II trial evaluating sorafenib as a single agent in chemonaïve patients with recurrent or metastatic HNSCC showed results comparable with other agents in this setting with a median progression-free survival of 4 months and a median overall survival of 9 months [42]. Moreover, a recent study showed encouraging results when sorafenib was used in combination with carboplatin and paclitaxel in recurrent or metastatic HNSCC [43]. It is possible that sorafenib combinations are worthwhile of further exploration in HNSCC (Table 3). Sunitinib has been tested in phase II clinical trials in recurrent or metastatic HNSCC tumors [44–46] showing low efficacy as monotherapy (Table 2). Also, some of these studies showed

increased vascular and skin toxicities in patients with recurrent or metastatic HNSCC treated with sunitinib. Choong et al. evaluated sunitinib monotherapy in patients with recurrent or metastatic HNSCC with no more than two previous lines of treatment. The study showed poor antitumor activity and significant incidence of bleeding events (6 grade 3–5 in 38 patients, 4 of which were fatal) [44]. Another phase II trial assessing the use of single-agent sunitinib by Fountzilas et al. in patients with recurrent or metastatic HNSCC did not meet efficacy endpoints and was terminated prematurely [45]. Finally, a third study of sunitinib monotherapy in 38 patients with platinum-refractory disease or unfit for platinum with recurrent or metastatic HNSCC by Machiels et al. reported a response rate of 3% and a median overall survival of only 3.4 months. In this study 15 patients had worsening skin ulceration or fistula [46]. Vandetanib, a multikinase inhibitor that targets both EGFR and VEGFR, has also been investigated in HNSCC. A phase II trial of docetaxel with or without vandetanib in patients with recurrent or metastatic HNSCC showed low activity of the combination with vandetanib and did not proceed to the second stage of accrual [47]. The clinical results with VEGFR TKIs so far indicate that these agents are generally not effective as monotherapy. Moreover, their toxicity profile suggests that careful patient selection is needed for safe clinical use. Ongoing trials with other VEFR TKIs, namely pazopanib and axitinib, are in progress (Table 3). Clinical data: locally advanced HNSCC Bevacizumab is the antiangiogenesis agent that has been studied the most in the treatment of potentially curable HNSCC.

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M. Vassilakopoulou et al. / Oral Oncology xxx (2015) xxx–xxx Table 3 Ongoing trials with angiogenesis targeting agents in head and neck cancer. Antiangiogenesis agent

Regimen

Disease setting/phase

Sample size/primary endpoint

NCT#

Bevacizumab

Recurrent or metastatic HNSCC/Phase III

400/Overall survival

NCT00588770

Sorafenib

Chemotherapy (cisplatin/docetaxel, carboplatin/ docetaxel, cisplatin/5-FU, carboplatin/5FU) ± bevacizumab Cisplatin/docetaxel/sorafenib

Recurrent or metastatic HNSCC/Phase I–II

NCT02035527

Axitinib

Axitinib (single agent)

Pazopanib

Pazopanib (single agent)

Pazopanib

Pazopanib/cetuximab

Unresectable, recurrent or metastatic HNSCC/ Phase II Recurrent or metastatic HNSCC refractory to platinum-based chemotherapy/Phase II Recurrent or metastatic HNSCC/Phase I

41/Progression-free survival (Phase II) 40/Progression-free survival 45/Objective response rate Safety/maximum tolerated dose

NCT01469546 NCT01377298 NCT01716416

Abbreviations: HNSCC, head and neck squamous cell carcinoma.

Several phase I and II trials have examined the tolerability and antitumor activity of bevacizumab combined with various chemoradiotherapy regimens. The University of Chicago group evaluated the addition of bevacizumab to 5-fluorouracil (5-FU), hydroxyurea and concomitant radiotherapy in a phase I trial of poor-prognosis HNSCC. This combination was considered feasible and promising as it showed antitumor activity in the reirradiation setting, although complications like fistula formation and tissue necrosis were potentially attributed to bevacizumab [48]. These results prompted a subsequent randomized phase II study by the same group investigating 5-FU, hydroxyurea and radiotherapy with or without bevacizumab in patients with intermediate-stage and selected T4 N0-1 HNSCC [49]. However, this study was terminated early after enrollment of the first 26 patients (17 treated with bevacizumab and 9 without bevacizumab) due to concerns for unacceptably high local relapse rate in patients with T4 tumors. The 2-year survival for all patients was 58% in the bevacizumab arm vs 89% in the non-bevacizumab arm. As a result the investigators suggested that combinations of bevacizumab with chemoradiotherapy should only be administered within the context of clinical studies. Hainsworth et al. evaluated the combination of bevacizumab and erlotinib with concurrent radiotherapy and paclitaxel after a 6-week induction regimen with carboplatin, paclitaxel, 5-FU, and bevacizumab in 60 previously untreated patients with locally advanced HNSCC [50]. This study reported a 3-year progressionfree survival rate of 71% and an overall survival rate of 82% after a median follow up of 32 months. Toxicities reported with this combined modality approach with the integration of bevacizumab and erlotinib were acceptable and comparable with other regimens used in HNSCC. In a prospective trial conducted by Yoo et al. in patients with newly diagnosed locally advanced HNSCC, bevacizumab was used with erlotinib and concurrent chemoradiotherapy with cisplatin after a 2-week lead-in of erlotinib and/or bevacizumab [51]. Twenty-nine patients were enrolled in this trial which showed that dual VEGF/EGFR inhibition can be safely combined with chemoradiotherapy, and results in outcomes comparable or favorable to historical controls in terms of survival rates (86% at 3 years) and locoregional control (85% at 3 years). However, a significant risk of osteoradionecrosis (n = 3) and soft tissue necrosis (n = 2) was noted. Of interest was that changes in baseline and follow-up dynamic contrast enhanced magnetic resonance imaging (DCEMRI) correlated with treatment efficacy. Fury et al. conducted a phase II trial in 42 patients with locally advanced HNSCC who were treated with intensity-modulated radiation therapy with concomitant cisplatin and bevacizumab. This study yielded encouraging results in terms of survival rates (at 2 years, progression-free survival of 76% and overall survival of 88%) with expected toxicities, including 2 treatment-related

deaths, showing that bevacizumab may be considered as radiosensitising agent along with cisplatin [52]. The combination of docetaxel and bevacizumab with radiotherapy has also been evaluated with promising results [53]. Finally, a phase II randomized trial by Argiris et al. incorporated bevacizumab into a non-platinum containing regimen with pemetrexed and cetuximab in combination with radiotherapy for the treatment of locally advanced HNSCC [54]. This approach was feasible with expected toxicities. Maintenance with bevacizumab was discontinued after a late death from pulmonary bleeding. Both treatment arms showed high progression-free survival rates at 2 years. Mature efficacy results are not yet available. Taken together, the combination of bevacizumab with chemoradiotherapy regimens has yielded conflicting results in small studies in terms of safety and activity. The combination of radiotherapy and bevacizumab with 5-FU and hydroxyurea was not recommended for further study, however, combinations of radiotherapy with cisplatin/bevacizumab or docetaxel/bevacizumab were feasible and promising. A final analysis of the combination with radiotherapy with pemetrexed, cetuximab with or without bevacizumab is pending. At this time there are no planned phase III trials with bevacizumab in the setting of locally advanced HNSCC.

Study of biomarkers and challenges An obstacle in the clinical development of angiogenesis inhibitors in cancer has been the lack of validated biomarkers that predict response or resistance to treatment. Many types of predictive biomarkers have been explored, including hypertension, circulating markers, germline single nucleotide polymorphisms (SNPs), in situ biomarkers in tumors and functional imaging [55]. Heterogeneity of tumor blood vessels, alternative proangiogenesis signaling pathways, infiltrating stromal cells, alternative mechanisms of tumor vascularization, interaction between VEGF receptors and other cell surface receptors have all been proposed as potential mechanisms of intrinsic or acquired resistance to antiangiogenesis treatment [56]. Recently, Gourley and colleagues presented a gene expression signature predictive of bevacizumab benefit in ovarian cancer which may warrant investigation in HNSCC as well [57]. Nevertheless, at this time, there are no biomarkers of clinical utility for individualizing therapy with antiangiogenesis agents. Preclinical studies in animal models have indicated that VEGF-targeted therapies suppress the growth of primary tumor but promote metastatic evolution [58,59]. This raises the concern that anti-VEGF therapy can increase tumor aggressiveness. However, there is currently no clinical data in HNSCC to support this hypothesis.

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Conclusions Angiogenesis plays a critical role in HNSCC progression and mediates treatment resistance. Therefore, targeting angiogenesis, and in particular the VEGF pathway, represents an appealing therapeutic strategy in patients with HNSCC. However, monotherapy with antiangiogenesis agents has generally demonstrated low or modest activity. Combination regimens with the addition of antiangiogenesis agents to chemotherapy or other targeted agents are of major interest and some have shown promise. The incorporation of angiogenesis inhibitors to current therapeutic strategies poses many challenges. In the locally advanced setting, for example, the feasibility of incorporating bevacizumab into chemoradiotherapy has not been consistently demonstrated in early clinical trials. In the recurrent or metastatic disease setting, the results of a large phase III trial (E1305) that evaluates the addition of bevacizumab to chemotherapy are eagerly awaited. Finally, the identification and validation of predictive biomarkers for angiogenesis targeting, that remain elusive for this class of agents, may lead to appropriate individualization of treatment. Conflict of interest statement None declared. Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.oraloncology. 2015.01.006. References [1] Hsu HW, Wall NR, Hsueh CT, et al. Combination antiangiogenic therapy and radiation in head and neck cancers. Oral Oncol 2014;50:19–26. [2] Neufeld G, Kessler O. Pro-angiogenic cytokines and their role in tumor angiogenesis. Cancer Metastasis Rev 2006;25:373–85. [3] Senger DR, Galli SJ, Dvorak AM, et al. Tumor cells secrete a vascular permeability factor that promotes accumulation of ascites fluid. Science 1983;219:983–5. [4] Koch S, Claesson-Welsh L. Signal transduction by vascular endothelial growth factor receptors. Cold Spring Harb Perspect Med 2012;2:a006502. [5] Maxwell PH, Wiesener MS, Chang GW, et al. The tumour suppressor protein VHL targets hypoxia-inducible factors for oxygen-dependent proteolysis. Nature 1999;399:271–5. [6] Hicklin DJ, Ellis LM. Role of the vascular endothelial growth factor pathway in tumor growth and angiogenesis. J Clin Oncol 2005;23:1011–27. [7] Kowanetz M, Ferrara N. Vascular endothelial growth factor signaling pathways: therapeutic perspective. Clin Cancer Res 2006;12:5018–22. [8] Goel HL, Mercurio AM. VEGF targets the tumour cell. Nat Rev Cancer 2013;13:871–82. [9] Ferrara N, Gerber HP, LeCouter J. The biology of VEGF and its receptors. Nat Med 2003;9:669–76. [10] Christopoulos A, Ahn SM, Klein JD, Kim S. Biology of vascular endothelial growth factor and its receptors in head and neck cancer: beyond angiogenesis. Head Neck 2011;33:1220–9. [11] Bachelder RE, Crago A, Chung J, et al. Vascular endothelial growth factor is an autocrine survival factor for neuropilin-expressing breast carcinoma cells. Cancer Res 2001;61:5736–40. [12] Barr MP, Bouchier-Hayes DJ, Harmey JJ. Vascular endothelial growth factor is an autocrine survival factor for breast tumour cells under hypoxia. Int J Oncol 2008;32:41–8. [13] Hansen W, Hutzler M, Abel S, et al. Neuropilin 1 deficiency on CD4+ Foxp3+ regulatory T cells impairs mouse melanoma growth. J Exp Med 2012;209: 2001–16. [14] Stanton MJ, Dutta S, Zhang H, et al. Autophagy control by the VEGF-C/NRP-2 axis in cancer and its implication for treatment resistance. Cancer Res 2013;73:160–71. [15] Kyzas PA, Cunha IW, Ioannidis JP. Prognostic significance of vascular endothelial growth factor immunohistochemical expression in head and neck squamous cell carcinoma: a meta-analysis. Clin Cancer Res 2005;11: 1434–40. [16] Kyzas PA, Stefanou D, Batistatou A, Agnantis NJ. Potential autocrine function of vascular endothelial growth factor in head and neck cancer via vascular endothelial growth factor receptor-2. Mod Pathol 2005;18:485–94.

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Please cite this article in press as: Vassilakopoulou M et al. Targeting angiogenesis in head and neck cancer. Oral Oncol (2015), http://dx.doi.org/10.1016/ j.oraloncology.2015.01.006