Identification of biological effects of bevacizumab in surgically resectable melanoma tumors.

1.1 Melanoma
Malignant melanoma is an important cause of morbidity and mortality. The 5 year
survival in patients with a local recurrent malignant melanoma is less than
50%. The tumor is relatively chemotherapy resistant. Dacarbazine (DTIC) is
accepted generally as therapy in metastatic disease with a response rate of
approximately 20%, though without significant impact on survival.
Biochemotherapy, combining chemotherapeutic drugs with interleukin or
interferon has not been proven to be superior to single agent DTIC. Apart from
chemotherapy, molecular targeted therapy has emerged in the treatment of
tumors. One of these monoclonal antibodies, bevacizumab (Avastin®), has been
approved by the FDA for clinical use in metastatic colorectal disease.
Currently, several studies have been started in which the use of bevacizumab is
evaluated, with or without the use of single or combined chemotherapy in
patients with melanoma tumors.
Overexpression of VEGF and the VEGF receptor occurs in > 80 % of the malignant
melanoma. At this time, it is unknown whether patients with malignant melanoma
will respond to bevacizumab therapy.

1.2 Angiogenesis
There are several factors involved in the development and growth of tumors.
Angiogenesis, the forming of new blood vessels is one of these factors. New
vasculature allows tumor cells to execute their critical growth by supplying
the tumor with nutrients and oxygen, disposal of metabolic waste products and
provides route for metastatic spreading. An important factor involved in
angiogenesis is VEGF 5. VEGF is released by tumor cells and induces tumor
neovascularization. VEGF consists of at least 4 splice variants, containing
121, 165, 189 and 206 amino acids 5, involved in endothelial proliferation,
tubular formation, endothelial survival, endothelial migration, vascular
permeability and gene expression. These actions are thought to be transmitted
by the VEGF-receptors VEGFR-1, VEGFR-2 (KDR/Flk-1) and VEGFR-3 (Flt-4). The
VEGF-receptors are tyrosine kinase mediated transmembrane receptors. The VEGF
production is thought to be regulated by hypoxemia, cytokines and cell
differentiation.
Over-expression of VEGF occurs in many human tumor types. The local VEGF
production leads to paracrine effects in the tumor, resulting in angiogenesis
and growth exploration. This has lead to interest in blocking the signaling of
VEGF in human tumors. Chemical molecules which can block the tyrosine kinase
function of VEGF-receptors and antibodies binding to the ligand and the
receptor have been developed.
An example is the monoclonal antibody bevacizumab which is derived from the
murine VEGF monoclonal antibody A4.6.1. It blocks VEGF induced endothelial cell
proliferation, permeability and survival, and it inhibits human tumor cell line
growth in nude mice. The likely mechanism of its anti-angiogenic activity is
that soluble VEGF is prevented from binding to its receptors, thereby blocking
the biological pathways of VEGF.

To identify biological effects of bevacizumab therapy and to visualize
distribution kinetics of 111In-bevacizumab with gamma-camera imaging.

Observational study evaluating the anti-angiogenic and apoptotic response of
bevacizumab in patients with surgically resectable melanoma.
Patients with surgically resectable melanoma, who are planned for surgery will
be treated neo-adjuvant with bevacizumab therapy. The anti-angiogenic and
apoptotic response will be evaluated by measuring hematological and
histological parameters. The distribution kinetics of 111In-bevacizumab will be
visualized by gamma-camera imaging. The patients will receive two injections of
111In-bevacizumab and four gamma-camera scans. The first 2 scans will serve as
a baseline. After the second scans it will be possible to compare imaging data
before and after treatment and hereby evaluate tumor response.

In this study bevacizumab is administered in both therapeutic dose and in
tracer-dose, therefore the risk of side-effects is present. The risk of any
additional side effects by the administration of a tracer dose (10 mg) of
radiolabeled bevacizumab will be very low, compared to therapeutic
administration of bevacizumab (375-600 mg).
The most common side-effects reported after first line bevacizumab therapy are
diarrhea, hypertension, thrombotic events, deep thromboplebitis, pulmonary
embolus, bleeding, proteinuria and gastro-intestinal bleeding. These events are
for the most part mild to moderate in severity and clinically manageable
(hypertension, proteinuria, minor bleeding) or occur uncommonly (wound healing
complications, GI perforations and arterial thrombosis). Whether or not a
single dose of bevacizumab can induce any adverse effect is uncertain. Any
toxicity will be scored according to the Common Toxicity Criteria version 3.0.
Patients will be informed about possible side-effects and have physical
examination routinely.

Administration of 111In-bevacizumab entails radiation load from the
participating patients. It has been calculated that a dose of 100 Mbq will lead
to a radiation load of 18mSv (see appendix 13.3). In this study protocol this
will lead to 36 mSv. For comparison, a CT-abdomen will lead to a radiation dose
of 10-15 mSv. The poor prognosis of this patient group (5 year survival < 50%)
and the potential new information given by this study makes this radiation load
acceptable.