Liebert had a longstanding interest in microbiology.
In graduate school, he worked in a molecular biology
research lab and took biology and genetics classes.
“The idea of harnessing my own immune system to
identify, attack and destroy my own cancer cells had
an intuitive appeal to me,” he says.
Researchers have been chasing the idea of treating cancer with vaccines for decades, but the history
of the science shows more failures than successes.
In recent years, however, treatment vaccines have
attracted more interest thanks to advances in
immunotherapy, an approach that harnesses the
body’s immune system to attack cancer. Clinical
trials suggest that personal vaccines, tailored to treat
a particular tumor, could help extend survival in
patients with hard-to-treat disease.
“We’re excited, and we are hopeful, but [vaccines] are
going to require very carefully designed, well-thought-out studies that focus not only on efficacy but on safety,”
says neuro-oncologist Mark Gilbert at the National
Cancer Institute (NCI) in Bethesda, Maryland.
PREVENTING CANCER AND TREATING IT
To most people, vaccines mean disease prevention
and conjure up memories of receiving childhood
shots to prevent measles, mumps, rubella and other
infections. Those immunizations use weakened
bits of disease-causing microbes to train the body’s
immune system to defend itself. They are preventive
and proactive; they take care of a problem before it
becomes a problem.
The U.S. Food and Drug Administration (FDA)
has approved two types of vaccines that prevent
cancer by fighting off infections from cancer-causing viruses. One vaccine inoculates a person
against hepatitis B, which can lead to liver cancer.
The other inoculates people against strains of the
human papillomavirus (HPV), which causes the
majority of cervical cancers and has been implicated
in a number of cancers at other sites, including the
mouth and throat, rectum and vulva. (See “HPV
Vaccine: A Decade of Prevention” on pg. 35.)
Therapeutic vaccines like the one Liebert was
given are different. They treat people already
diagnosed with cancer and represent a newer, more
experimental area of research. Cancer treatment
vaccines are a type of immunotherapy. Clinical trials
have shown that some immunotherapy treatments
increase survival for certain patients, and these
findings have led to FDA approvals of new therapies
for metastatic melanoma, lung cancer and other
cancers. However, not all patients respond favorably
to immunotherapy, and those who do may develop
resistance. Cancer treatment vaccines may play a
role in extending the benefits of immunotherapy to
more patients and for longer periods of time.
Liebert received chemotherapy in Maine and
traveled to Beth Israel Deaconess Medical Center
in Boston for the vaccine trial, which was led by
hematologist-oncologists David Avigan and Jacalyn
Rosenblatt. The researchers have pioneered a
similar experimental vaccine for people with acute
myeloid leukemia (AML).
One opportunity to incorporate a vaccine into a
treatment regimen might be after a disease has been
reduced through chemotherapy or other treatments,
Rosenblatt says. “We want to eradicate residual disease
and prevent the disease from recurring,” she says.
In 2010, the FDA approved the first therapeutic
cancer vaccine, Provenge (sipuleucel-T), for men
whose metastatic prostate cancer has stopped
responding to hormone therapy. Clinical trials are
investigating dozens more. Recent and ongoing
trials are testing vaccines for melanoma and
breast, lung, prostate and other cancers.
TREATMENT VACCINES HAVE
ATTRACTED MORE INTEREST
THANKS TO ADVANCES IN
LOOKING WITHIN FOR CANCER TREATMENT