First there was surgery, then chemotherapy and radiation. Now,
doctors have overcome 30 years of false starts and found success
with a fourth way to fight cancer: using the body's natural
defender, the immune system.
The approach is called a cancer vaccine, although it treats the
disease rather than prevents it. At a recent cancer conference researchers said one such vaccine kept a common form of lymphoma from worsening for more than a year.
That's huge in this field, where progress is glacial and success
with a new treatment is often measured in weeks or even days.
Experimental vaccines against three other cancers - prostate,
the deadly skin disease melanoma and an often fatal childhood tumour
called neuroblastoma - also gave positive results in late-stage
testing in recent weeks, after decades of struggles in the lab.
"I don't know what we did differently to make the breakthrough,"
said Dr Len Lichtenfeld of the American Cancer Society.
Instead of a single "A-Ha!" moment, there have been many "ah,
so" discoveries about the immune system that now seem to be paying
off, said Dr John Niederhuber, director of the National Cancer
Still lots of questions without answers
It's way too soon to declare victory. No one knows how long the
benefits will last, whether people will need "boosters" to keep
their disease in check, or whether vaccines will ever be a cure.
Many vaccines must be custom-made for each patient. How practical
will that be, and what will it cost?
Those are all good questions - but there are no answers yet,
said Dr Richard Schilsky, a University of Chicago cancer
specialist who is president of the American Society of Clinical
Several vaccine studies were reported over the weekend at the
oncology group's annual meeting in Florida. A big problem has been getting the immune system to "see" cancer as a threat, said Dr Patrick Hwu, melanoma chief at the University of Texas M.D. Anderson Cancer Centre.
Viruses like the flu or polio are easily spotted by the immune system because they look different from human cells. "But cancer comes from our own cells. And so it's more like guerrilla warfare - the immune system has trouble distinguishing the normal cells from the cancer cells," he said.
To help it do that, many cancer vaccines take a substance from a
cancer cell's surface and attach it to something the immune system
already recognizes as foreign - in the lymphoma vaccine's case, a
How the study was done
"It's a mimic to what you're trying to kill, a training device
to train the immune system to kill something," Hwu explained.
To make the attack as strong as possible, doctors add a substance to put the immune system on high alert.
Dr Stephen Schuster of the University of Pennsylvania School of
Medicine led a study testing BiovaxID, an experimental vaccine
against follicular lymphoma developed by the National Cancer
Institute. Rights to it are now held by Biovest International Inc.
of Worcester, Massachusetts, and some of his co-researchers have
financial ties to the company.
To be in the study, patients had to have achieved a remission
for at least six months with standard chemotherapy. This often
occurs with this type of lymphoma, but the disease usually comes
Researchers gave 41 patients the shellfish protein and an immune
booster; 76 other patients were given those plus the vaccine. After
nearly five years of follow-up, the average time until the cancer
worsened was 44 months in the vaccine group and 30 months in the
What the findings revealed
Big gains also were seen with a neuroblastoma vaccine developed
by the cancer institute. In a study of 226 patients, 86% of
vaccine recipients were still alive after two years versus 75% of others not given the vaccine. Results were released by the oncology society two weeks ago.
The benefits from a melanoma vaccine developed by the cancer
institute were more modest. It extended the time until patients
relapsed - three months versus one and a half for those not given
Hilde Stapleton, 53, of suburban Houston, is one of the lucky
ones it helped. Still, she found what many other vaccine recipients
have learned: The vaccine had few side effects, but the immune
system boosters were "like the worst case of flu you've ever had,"
The prostate cancer vaccine, Provenge, is farthest along. Its
maker, Seattle-based Dendreon Corp., is seeking federal Food and
Drug Administration approval for it. A study last month found that
it extended survival by four months in men with very advanced
Doctors unconnected with these experiments are cautiously
optimistic. "We've raised so many false hopes in the past," said Lichtenfeld of the Cancer Society. "What's different this time is we have the science reports to back up improvements." – (Sapa, June 2009)
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