Microvascular Density as a Predictive Biomarker for Bevacizumab Survival Benefit in Ovarian Cancer: Back to First Principles?
JNCI J Natl Cancer Inst (
Microvascular Density as a Predictive Biomarker for Bevacizumab Survival Benefit in Ovarian Cancer: Back to First Principles?
Napoleone Ferrara 0 1
0 The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions , please
1 Affiliation of author: University of California San Diego Moores Cancer Center , La Jolla CA , USA
Vascular endothelial growth factor–A (VEGF-A) is a key regulator
of physiological and pathological angiogenesis (
promising preclinical data showing growth inhibition in
multiple tumor xenograft models, a murine anti-VEGF-A monoclonal
antibody was humanized to enable clinical trials in cancer
). This humanized antibody, known as bevacizumab,
was first approved by the US Food and Drug Administration
(FDA) for previously untreated metastatic colorectal cancer in
2004, after a phase III trial that showed that bevacizumab plus
chemotherapy increased both progression-free survival (PFS)
and overall survival (OS) relative to chemotherapy alone (
These benefits were seen despite the lack of a biomarker to
select patients most likely responsive to the treatment (
put this in perspective, a very effective therapeutic like
trastuzumab would have required a much larger trial to demonstrate
benefits in the absence of selection of breast cancer patients for
human epidermal growth factor receptor 2 (HER2)
). Bevacizumab has been tested in numerous tumor types
and today is FDA approved in multiple indications (
metastatic cervical cancer (
), platinum-resistant ovarian cancer
), and, most recently, platinum-sensitive, recurrent ovarian
(http://www.roche.com/media/store/releases/med-cor2016-12-07.htm). However, not all studies have demonstrated an
OS benefit. While this may be attributed, at least in part, to
patient crossover from the control group to bevacizumab or other
treatment groups, it is clear that the response to bevacizumab
and other anti-VEGF agents has been heterogeneous (
Although a number of predictive biomarkers for bevacizumab
and other VEGF pathway inhibitors have been suggested on the
basis of small patient series, including hypertension, tumor
imaging, soluble VEGF receptors, circulating proinflammatory cytokines,
or gene signatures, none has been prospectively validated yet
[reviewed in (
)]. This difficulty might also reflect the complexity
of the angiogenesis process, which is influenced by multiple
players within the microenvironment, as compared with
tumorintrinsic changes such as oncogene mutations or amplifications (5).
An additional level of complexity—and potentially a
confounder—is represented by the use of cytotoxic agents in
conjunction with anti-VEGF therapy. In fact, several cytotoxic
agents (including paclitaxel) have been shown to have
antivascular effects (
), and rebound angiogenesis, mediated by
mobilization of myeloid cells, has been reported to be a mechanism of
tumor resistance to certain cytotoxics (
It has been speculated that most of the benefits of anti-VEGF
therapy derive from facilitating tumor delivery of cytotoxic agents
through “normalization” of the vasculature (
preclinical studies have clearly shown single-agent activity of VEGF
inhibitors in a variety of tumor models (
), including ovarian
cancer models. An early study reported that monotherapy with
an anti-VEGF antibody resulted in suppression of angiogenesis
and growth of human ovarian cancer cells implanted in
immunodeficient mice (
). This study also emphasized the importance of
long-term VEGF inhibition because interruption of the antibody
treatment resulted in resumption of tumor growth as well as
ascites formation (
). A more recent study by Mabuchi et al.
went further, showing that while combination of bevacizumab
with chemotherapy improved survival of mice implanted with
ovarian cancer cells relative to chemotherapy alone, the greatest
benefit was observed in the group that received long-term
“maintenance” with single-agent bevacizumb after the
administration of bevacizumab plus chemotherapy (
The Gynecological Oncology Group (GOG)-218 study, by
virtue of its innovative design, is an important study in
antiangiogenesis. Over 1200 patients with newly diagnosed stage III
and IV ovarian cancer were randomly assigned to three groups
). All three groups included paclitaxel and carboplatin for
cycles 1 through 6. The control treatment was chemotherapy
with placebo added in cycles 2 through 22. Bevacizumab initiation
treatment was chemotherapy with bevacizumab (15 mg/kg every
three weeks) added in cycles 2 through 6 and placebo added in
cycles 7 through 22. Bevacizumab throughout treatment was
chemotherapy with bevacizumab added in cycles 2 through 22.
Interestingly, bevacizumab throughout was the only treatment
group that had a statistically and biologically significant
improvement in PFS, the primary end point of the trial. The increase was
four or six months, depending on how PFS was evaluated (
parallel randomized phase III study, ICON7, also tested a
“maintenance” arm, but the dose of bevacizumab was lower
(7.5 mg/kg every three weeks) and the improvement in PFS was of
lesser magnitude compared with GOG-218, suggesting a dose
). However, in spite of the improvement in PFS,
no statistically significant OS improvement was seen in
GOG218, although crossover from the chemotherapy-alone arm to
bevacizumab-containing therapy (or other treatment lines)
might have potentially masked an effect on OS.
Bais et al. (
) sought to evaluate potential tumor biomarkers
from patients in the GOG-218 study. Nine hundred and eighty
patients (78.5% of the patients that were enrolled in the trial)
were evaluable. Candidate biomarkers were assessed by
immunohistochemistry (IHC) after completion of the clinical trial using
sections taken from the pretreatment tumor samples. The
authors found that while no prognostic or predictive associations
were observed for cMet, Neuropilin-1, and VEGFR-2, tumor-VEGF
was associated with OS, although not with PFS. Intriguingly, the
marker that showed the strongest association with clinical
benefit was microvascular density (MVD). The effects of bevacizumab
treatment on both PFS and OS were greater in patients with
higher MVD in tumor sections. Although the analysis by Bais
et al. is retrospective, it was prespecified (
The study by Bais et al. is important and, if confirmed, is likely
to have a major impact in the design of future trials. It represents
possibly the largest biomarker study in anti-angiogenesis to show
a statistically significant association with benefit, including OS.
However, previous studies did not identify MVD as a predictive
marker of bevacizumb benefit. For example, Jubb et al. (
retrospectively evaluated several potential predictive biomarkers,
including MVD, from a randomized colorectal cancer study (
did not find any correlation with treatment outcomes. However,
the samples analyzed accounted for only a fraction of the
patients enrolled in the trial (
). Also, in the samples from
the GOG-218 trial, MVD was assessed by CD31 IHC (
), while in
the study by Jubb et al. it was assessed by CD34 IHC (
it is unknown whether this difference may have affected the
outcome. It is also possible that the design of GOG-218 may have
enabled assessment of markers of bevacizumab outcomes with
greater fidelity than other studies because the group that showed
benefit received single-agent bevacizumab for the majority of the
trial, thus reducing the aforementioned potential confounding
effects of chemotherapy. Alternatively, one cannot rule out the
possibility that biomarkers predictive of bevacizumab outcomes
may be tumor type specific, as suggested for glioblastoma
The actions of VEGF are complex, and recent studies have
emphasized, for example, effects on the immune system that
could have not been adequately evaluated in studies conducted
in immunodeficient mice (
). Nevertheless, it is refreshing that
endothelial cells, the main target of VEGF, are back at the center
stage. Previous studies showed a correlation between MVD and
malignant behavior in human tumors (
), and preclinical
studies directly showed a correlation between inhibition of tumor
growth by an anti-VEGF antibody treatment and suppression of
). Intuitively, patients with tumors having the
highest MVD and/or VEGF content are expected to derive the
greatest benefit from anti-VEGF therapy.
The author has no conflicts of interest to disclose.
1. Ferrara N , Gerber HP , LeCouter J . The biology of VEGF and its receptors . Nature Med . 2003 ; 9 ( 6 ): 669 - 676 .
2. Ferrara N. Commentary on “humanization of an anti-vegf monoclonal antibody for the therapy of solid tumors and other disorders . ” Cancer Res . 2016 ; 76 ( 17 ): 4913 - 4915 .
3. Hurwitz H , Fehrenbacher L , Novotny W , et al. Bevacizumab plus irinotecan, fluorouracil, and leucovorin for metastatic colorectal cancer . N Engl J Med . 2004 ; 350 ( 23 ): 2335 - 2342 .
4. Slamon DJ , Leyland-Jones B , Shak S , et al. Use of chemotherapy plus a monoclonal antibody against HER2 for metastatic breast cancer that overexpresses HER2 . N Engl J Med . 2001 ; 344 ( 11 ): 783 - 792 .
5. Ferrara N , Adamis AP . Ten years of anti-vascular endothelial growth factor therapy . Nat Rev Drug Discov . 2016 ; 15 ( 6 ): 385 - 403 .
6. Tewari KS , Sill MW , Long HJ 3rd, et al. Improved survival with bevacizumab in advanced cervical cancer . N Engl J Med . 2014 ; 370 ( 8 ): 734 - 743 .
7. Pujade-Lauraine E , Hilpert F , Weber B , et al. Bevacizumab combined with chemotherapy for platinum-resistant recurrent ovarian cancer: The AURELIA open-label randomized phase III trial . J Clin Oncol . 2014 ; 32 ( 13 ): 1302 - 1308 .
8. Jain RK , Duda DG , Willett CG , et al. Biomarkers of response and resistance to antiangiogenic therapy . Nat Rev Clin Oncol . 2009 ; 6 ( 6 ): 327 - 338 .
9. Kerbel RS , Kamen BA . The anti-angiogenic basis of metronomic chemotherapy . Nat Rev Cancer . 2004 ; 4 ( 6 ): 423 - 436 .
10. Hasnis E , Alishekevitz D , Gingis-Veltski S , et al. Anti-Bv8 antibody and metronomic gemcitabine improve pancreatic adenocarcinoma treatment outcome following weekly gemcitabine therapy . Neoplasia . 2014 ; 16 ( 6 ): 501 - 510 .
11. Jain RK . Normalizing tumor vasculature with anti-angiogenic therapy: A new paradigm for combination therapy . Nat Med . 2001 ; 7 ( 9 ): 987 - 989 .
12. Gerber HP , Ferrara N. Pharmacology and pharmacodynamics of bevacizumab as monotherapy or in combination with cytotoxic therapy in preclinical studies . Cancer Res . 2005 ; 65 ( 3 ): 671 - 680 .
13. Mesiano S , Ferrara N , Jaffe RB . Role of vascular endothelial growth factor in ovarian cancer: Inhibition of ascites formation by immunoneutralization . Am J Pathol . 1998 ; 153 ( 4 ): 1249 - 1256 .
14. Mabuchi S , Terai Y , Morishige K , et al. Maintenance treatment with bevacizumab prolongs survival in an in vivo ovarian cancer model . Clin Cancer Res . 2008 ; 14 ( 23 ): 7781 - 7789 .
15. Burger RA , Brady MF , Bookman MA , et al. Incorporation of bevacizumab in the primary treatment of ovarian cancer . N Engl J Med . 2011 ; 365 ( 26 ): 2473 - 2483 .
16. Perren TJ , Swart AM , Pfisterer J , et al. A phase 3 trial of bevacizumab in ovarian cancer . N Engl J Med . 2011 ; 365 ( 26 ): 2484 - 2496 .
17. Bais C , Mueller B , Brady MF , et al. Tumor vesssel density as a potential predictive marker for bevacizumab benefit: GOG-0218 biomarker analysis . J Natl Cancer Inst . 2017 ; 109 ( 11 ): djx066 .
18. Jubb AM , Hurwitz HI , Bai W , et al. Impact of vascular endothelial growth factor-A expression, thrombospondin-2 expression, and microvessel density on the treatment effect of bevacizumab in metastatic colorectal cancer . J Clin Oncol . 2006 ; 24 ( 2 ): 217 - 227 .
19. Sandmann T , Bourgon R , Garcia J , et al. Patients with proneural glioblastoma may derive overall survival benefit from the addition of bevacizumab to firstline radiotherapy and temozolomide: Retrospective analysis of the AVAglio Trial . J Clin Oncol . 2015 ; 33 ( 25 ): 2735 - 2744 .
20. Kandalaft LE , Motz GT , Busch J , Coukos G . Angiogenesis and the tumor vasculature as antitumor immune modulators: The role of vascular endothelial growth factor and endothelin . Curr Topics Microbiol Immunol . 2011 ; 344 : 129 - 148 .
21. Weidner N , Semple JP , Welch WR , Folkman J . Tumor angiogenesis and metastasis-correlation in invasive breast carcinoma . N Engl J Med . 1991 ; 324 ( 1 ): 1 - 8 .
22. Borgstrom P , Hillan KJ , Sriramarao P , Ferrara N. Complete inhibition of angiogenesis and growth of microtumors by anti-vascular endothelial growth factor neutralizing antibody: Novel concepts of angiostatic therapy from intravital videomicroscopy . Cancer Res . 1996 ; 56 ( 17 ): 4032 - 4039 .