Vaccines: Looking Within for Cancer Treament
Researchers are testing treatment vaccines that spur the immune system to attack cancer.
By Stephen Ornes
It’s been 10 years since Tom Liebert received an experimental cancer vaccine to treat his multiple myeloma, and he still wonders: Did it work?
The question nags at him, but not always. After all, he’s still alive and singing with a barbershop quartet in Fairfield Glade, Tennessee. And while he knows multiple myeloma is currently incurable, it is treatable. “The definition of a cure for me is that I die from something other than myeloma,” says the retired electrical engineer and computer scientist, now 60.
In the fall of 2005, Liebert lived and worked in Boston and was teaching computer science to adult continuing education students at Northeastern University. He was 48 years old and seemed fit, but a combination of symptoms—sudden energy loss and bone pain—spurred him to get a physical that revealed proteins in his urine. A few months later, after moving to Maine, he suffered a compression fracture in one of his vertebrae and was diagnosed with osteoporosis. He began to think the proteins in his urine and the bone disease were related, and in September 2006, blood and urine tests, combined with a bone marrow biopsy of his hip, confirmed that he had stage III multiple myeloma.
Multiple myeloma is a cancer that usually starts in the plasma cells in bone marrow. Common symptoms include bone pain and weakness and fractured bones. The median age at diagnosis is 69; average survival after diagnosis with stage III multiple myeloma is about 29 months.
Liebert’s local oncologist prescribed Cytoxan (cyclophosphamide), an effective chemotherapy for multiple myeloma. He was also in contact with oncologist Paul Richardson at Dana-Farber Cancer Institute in Boston, who told him about a phase II clinical trial of an experimental vaccine.
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
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.
Most cancer treatment vaccines are customized for a patient and built from a patient’s own immune or tumor cells. That means they can’t be mass-produced and are expensive and arduous to make. (Clinical trials, like Liebert’s, typically cover the cost of a patient’s treatment.) Provenge, for example, costs $93,000 and extends a person’s life by roughly four months on average, according to a 2011 paper in Pharmacy and Therapeutics.
Still, clinical trials of vaccines appeal to people who have exhausted all other treatments, says neuro-oncologist Jason Fangusaro at the Ann and Robert H. Lurie Children’s Hospital of Chicago. Fangusaro runs a phase I clinical trial of a patient-derived vaccine for children diagnosed with certain types of brain and spinal cord tumors. “Many families are willing to try something new because their child is in a situation where there’s no curative option,” he says. “We can’t promise anything because this is uncharted territory, but the potential for benefit is something they’re willing to try.”