Molecular imaging with radiolabeled bevacizumab in metastatic colon carcinoma; a feasibility study in patients who do not show response on bevacizumab therapy.

1.1 Treatment of metastatic colon rectal carcinoma (CRC)

For a long time, 5-flourouracil (5-FU) has been the only proven treatment for
colorectal cancer. 5-FU treatment was generally combined with leucovorin. Novel
cytotoxic agents have expanded the treatment options. New compounds like
irinotecan, oxaliplatin and capecitabine have been implicated.
Co-administration of first irinotecan and secondly oxiplatin to 5-FU/leucovorin
(FOLFOX-regime) lead to increased patients survival. These data have caused
that the FOLFOX regime was approved as first-line chemotherapy for metastatic
CRC.
Although these new drugs lead to increased survival, the poor prognosis of
metastatic CRC has encouraged the development of new drugs, preferably with
minimal toxicity. Recently, new drugs have been developed, targeting different
pathways which are known to drive tumor progression. Some of these drugs, like
trastuzumab have shown clinical benefit in for example breast cancer.
Another example is bevacizumab (Avastin®) which is a humanized monoclonal
antibody designed to inhibit vascular endothelial growth factor (VEGF), the key
mediator in angiogenesis. In the first phase III trial, bevacizumab was
combined with first line chemotherapy IFL (irinotecan, 5-FU and leucovorin) in
the treatment of CRC. Bevacizumab was i.v. administered once every two weeks in
a dose of 5 mg/kg. The primary endpoints were significantly increased. The
overall survival improved from 15.5 to 20.3 months (p<0.001). Patient disease
free survival increased from 6.2 to 10.6 months (p<0.001). The overall response
rate increased from 34.8% to 44.8% (p=0.004) in the arm treated with
bevacizumab compared to the IFL/placebo arm. This benefit was seen in all
patient groups, independently from age, sex, performance status and location of
the primary tumor.
In a subgroup analysis of patients, who were given first line IFL/bevacizumab
followed by oxaliplatin-based progression therapy a median overall survival of
25.1 months was showed, compared to 19.6 months for patients receiving no
oxaliplatin therapy. Preliminary data of second line treatment with FOLFOX and
bevacizumab showed increased response from 21.8% versus 9.2% in the
FOLFOX/placebo group (p=0.0001).
These data suggest that a subset of patients may still benefit from
anti-angiogenic treatment in second line therapy, but most patients will have
only side-effects.

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. 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 7, 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.

1.3 Bevacizumab
The monoclonal antibody bevacizumab 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.
Bevacizumab is registered for clinical use in metastatic colon carcinoma. It
proved to be also promising (in combination with conventional chemotherapy) in
patients with NSCLC and breast cancer.

To recognize the distribution pattern of 111In-bevacizumab in patients who do
not show response on treatment with bevacizumab. The ultimate goal is to
identify and select patients who can be successfully treated.

Observational study evaluating the feasibility of 111In-bevacizumab in
non-responding patients.

Study procedure
Distribution kinetics of 111In-bevacizumab will be evaluated in non-responding
patients (see patients and methods) receiving second line/ third chemotherapy.
The following procedure will be followed:
• At day 14 of the first chemotherapy cycle (following inclusion in the study
protocol) patients will be injected with 111In-bevacizumab.
• Gammacamera imaging will initially be performed at day 0, 2, 4 and 7 days
after a single intravenous administration of 150 MBq 111In-bevacizumab (±10 mg
protein). (The optimal time to scan the patients will be determined after two
or three patients. Hereafter patients will only be scanned once or twice after
tracer injection, most likely on day 0 and 4 after tracer injection.)

Planar whole body imaging will be performed, using a two-headed gammacamera,
equipped with parallel-hole medium-energy collimators, at a scan speed of 10
cm/min (day 0 and 2 after injection) or 5 cm/min (day 4 and 7 after injection)
and stored digitally in a 256 x 1024 matrix. An aliquot of dose will be scanned
simultaneously. Optionally, single photon emission computed tomography (SPECT)
will be performed of regions. Per imaging session, the total amount of scan
time will not exceed 90 minutes.

50 ml of blood will be drawn before administration of 111In-bevacizumab and
before every scan to determine biological parameters in the circulation and
levels of 111In-bevacizumab in the circulation. (see paragraph 6.3).

In this study 111In-bevacizumab is administered in tracer-dose, therefore the
risk of pharmacological side-effects is minimized. Although the additional risk
of the bevacizumab tracer dose (± 10 mg) administration besides treatment with
chemotherapy including bevacizumab therapy (250-400 mg/every 2 weeks) is most
likely negligible, it can not be completely excluded.

The most common side-effects reported after first line chemotherapy with
bevacizumab therapy are leukopenia, 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 tracer dose of 111In-bevacizumab can
induce any adverse effect is unknown. Although no toxicity is expected from the
tracer-dose, if present, toxicity will be scored according to the Common
Toxicity Criteria version 3.0.

Administration of 111In-bevacizumab entails radiation load for the
participating patients. It has been calculated that a dose of 150 MBq will lead
to a radiation load of 27 mSv (see appendix 13.3). For comparison purposes, a
CT-abdomen will lead to a radiation dose of 10-15 mSv. The poor prognosis of
this patient group (5 year survival < 8%) and the potential new information
given by this study makes this radiation load acceptable.