A drug used against a common
virus may lengthen the lives of people with a deadly form of brain
cancer, a preliminary study suggests.
Writing in the 5 September
issue of the New England Journal of Medicine, researchers reported on 50
patients who were given the antiviral drug valganciclovir (Valcyte) to help
The cancer is the most common form of brain tumour in adults, and it carries a
dismal prognosis – with a typical survival of just over a year.
These 50 patients, however,
fared far better, researchers found.
After two years, 62% were
still alive. Of the 25 who took the antiviral continuously, 90% were still
alive. That compared with just 18% of patients who received most of the same
treatments – including surgery and chemotherapy – but did not take Valcyte.
"These data are by far
the best ever seen for these patients," said lead researcher Dr Cecilia
Soderberg-Naucler, of the Karolinska Institute in Stockholm, Sweden.
A brain cancer expert not
involved in the research also voiced enthusiasm. "These are very exciting
data," said Dr David Reardon, director of neuro-oncology at the
Dana-Farber Cancer Institute in Boston.
But he also urged caution
because there are many unknowns, and the findings need to be verified in a
controlled clinical trial – in which patients would be randomly assigned to
take Valcyte or not, and then followed over time.
What is cytomegalovirus?
Valcyte is a pill used to
treat cytomegalovirus (CMV) eye infections in people with AIDS. CMV is a very
common virus – up to 80% of adults contract it by age 40 – and it usually
causes no harm in someone with a healthy immune system.
Researchers have found,
however, that CMV dwells in the tumour cells of most people with glioblastoma,
which suggests that the virus contributes to the cancer in some way.
One recent lab study found
that when certain cancer-promoting gene mutations are present, CMV might speed
the growth of glioblastoma.
"It appears that the
virus alone is not sufficient to cause any human tumours," said Chang-Hyuk
Kwon, one of the researchers on that study.
Instead, it seems that CMV
"cooperates with human cancer gene alterations to accelerate development
and growth of the cancer," said Kwon, of the Ohio State University
Comprehensive Cancer Centre in Columbus.
As Reardon put it,
"For some reason, these [glioblastoma] cells are a place where CMV likes
That has been known for
several years, he said. The news here is that an anti-CMV drug might extend
Still, there are questions,
he said. The study, which was funded partly by Valcyte maker Hoffman-La Roche,
included 50 patients from a single hospital. Many were given the antiviral drug
as part of a "compassionate use" programme at the hospital.
The researchers then
compared them with 137 patients who were treated for glioblastoma at the same
hospital around the same time, but were not given Valcyte. All patients in both
groups received standard treatment, which typically meant surgery, chemotherapy
and, in many cases, radiation.
Reardon said the problem
with that type of study is that there's a risk of bias. Patients who were
chosen to receive Valcyte may have been younger, in better overall health and
more likely to respond to treatment.
On the other hand, he said,
the survival figures for the Valcyte patients were "so far above average,
it's hard to imagine they're just the result of cherry-picking the
Reardon said more work is
needed to see what drug dose is optimal, and whether patients have to take it
Another question, Kwon
said, is whether the drug treatment actually reduced CMV levels in the
patients' tumours, or if the virus was still lurking.
Plus, there's a risk of
side effects with Valcyte, Kwon said, including diarrhoea, vomiting and upset
stomach. It can also harm kidney or liver function.
Despite all that, Kwon
said, given the poor prognosis with glioblastoma, "anti-CMV treatment
should be seriously considered."
Doctors could prescribe
Valcyte for glioblastoma patients, Reardon said. But since it's not
specifically approved for the cancer, insurers may not pay – a big obstacle,
since the drug costs a couple thousand dollars a month.
Glioblastoma is diagnosed
in two or three people per 100 000 in the United States and Europe, according
to the National Brain Tumour Society. No one is sure what causes the cancer,
but it is more common in men and in people older than 50.
The National Brain Tumor
Society has more on glioblastoma.