A Vaccine Against Cancer? Recent Trials Have Some Doctors Hopeful — But No Cure Is Yet In Sight

Vaccines — the science of fighting disease by triggering the body’s own defense mechanism — have been a staple of medicine for decades.

 

But could the body’s own immune system be used to fight the deadly scourge of cancer?

It’s a tantalizing possibility, say the authors of a new study recently published in the Journal of the National Cancer Institute. That report tracked the effectiveness of an experimental vaccine in a small-scale trial among lung cancer patients.

The researchers, at Baylor University Medical Center in Dallas, reported that the vaccine caused a complete disappearance of advanced, non-small-cell lung cancer in three of the 43 patients who were treated. In seven other patients, the disease did not progress for a period ranging from five months to 28 months, while yet another patient saw his lung tumor shrink by 30{06cf2b9696b159f874511d23dbc893eb1ac83014175ed30550cfff22781411e5}.

The vaccine, called GVAX, was created by altering each patient’s own tumor cells to induce an immune system attack on the cancer. The trial is significant in that it’s the first time immunotherapy, by itself, has been effective against this particular type of cancer.

But some doctors caution against too much excitement, noting that vaccines have been a part of the cancer-research dialogue for many years, without much evidence that immunotherapy will have far-reaching benefits for cancer sufferers.

“This is something that has been pursued for some time,” said Dr. Wilson Mertens, medical director of Cancer Services for Baystate Health System. “It really gets down to the origin of systemic cancer treatment.

“When the term ‘chemotherapy’ was invented,” he explained, “it really described the use of antibiotics and anti-infective agents against bacteria. That has led people to look at vaccines, but there has yet to be a vaccine that has been shown in randomized, clinical trials to be effective.”

Further Review

Still, researchers continue to examine the possibilities. The British medical journal Lancet recently published the results of a phase III trial of a vaccine against kidney cancer.
That trial also used patients’ own tumor cells to create the vaccine, which was given after surgical removal of the diseased kidney. Patients who received the vaccine generally did better than those who received no such treatment, and it took longer for their cancer to recur, in those cases when it did so. But reverse the disease, this particular vaccine did not.

Dr. John Nemunaitis, the Baylor study’s lead researcher, said it’s far too soon to call such developments a strong step toward a cure. Still, he noted, the results are promising in the fight against a disease that is often resistant to chemotherapy and prone to return even after the removal of a tumor.

Dr. Jeffrey Schlom, who heads the National Cancer Institute’s Laboratory of Tumor Immunology and Biology, went so far as to call the studies “suggestive of something that’s potentially very important. The field is progressing exponentially in terms of knowledge and the types of vaccines that are being used. This is a very exciting time.”

Mertens asserted that, realistically, trials of such vaccines need to be broader and measured against control groups. Results in three of 43 participants, as in the Baylor study, simply lack needed context, he said.

“Sometimes cancers do slow down their growth and even undergo episodes of spontaneous regression. They don’t always have uniform rates of growth,” he said. “So when I hear about these single-arm studies looking at a group of patients treated with a vaccine, I wonder what a comparison group, treated with standard care, would have looked like. That’s really the proof of the pudding.”

According to the American Cancer Society (ACS), modern cancer vaccine research focuses primarily on treating existing cancer, rather than preventing new cases. The science behind the studies involves kick-starting the immune system so it attacks tumor cells that it might not otherwise recognize as a threat.

In some trial vaccines, cells are modified by adding proteins or other substances that stimulate the immune system. In others, antigens — substances that cause a response by the immune system — are placed into viruses, which deliver the antigens into the body.

“Some of these vaccines are just entering into clinical trials, and some have been in trials for a few years, but it takes years to find out if they work,” Schlom said.

Dr. T.J. Koerner, scientific program director for the ACS, added that doctors must tread lightly when dealing with the delicate immune system.

“Your body in a normal lifespan has to deal with lots of biological insults — bacteria, viruses, yeast,” he said. “If you disrupted the normal immune system, you might increase susceptibility to other things.”

Schlom noted that the nature of clinical trials poses another obstacle. Specifically, new therapies are typically tested in patients who have failed all conventional treatments — many of which are toxic to both cancerous cells and normal cells, and have already damaged the patient’s immune system beyond its ability to respond to the vaccine.

Brighter Pastures

Mertens said that, while vaccines don’t top the list of promising therapies, the field of genetics has doctors considerably more excited, and this is where he believes the next wave of positive developments will originate.

“Just in the past three weeks, we’ve had a number of drugs approved by the FDA — small molecules designed to block growth factor production and growth factor receptors,” he said.
Down the road, he added, scientists will be in the business of prescribing specific treatments for specific cancer, based on those cancers’ genetic makeup.

“That’s different from how we treat cancer now,” Mertens explained. “Now, we try a best-case approach and offer patients the treatment that seems to work best in a large group of people. But it doesn’t hone in on what the specific cancer is sensitive to.”

To bring such a revolution in treatment about, researchers will have to establish new statistical methodologies, he said — but that level of sophistication is not far off.

For now, doctors who hold out hope for more traditional cancer vaccine research are putting a positive spin on the latest studies, even as they caution against excessive optimism.
“There’s always the hype and the hope associated with the vaccine being a potential cure-all, and that’s got to be tempered,” Koerner said. “But I really think that some subsets of cancer will probably be very beneficially treated.”