The experimental vaccine targets a protein linked to more than half of all cases of non-small-cell lung cancer, the most common form of lung cancer.

The study is published in The Lancet Oncology.

The study was conducted in Europe and included 148 patients with advanced lung cancer. It was led by Elisabeth Quiox, MD, a professor of pneumonology at the Universite de Strasbourg, France.

The patients were divided into two groups. Both groups received standard chemotherapy while one group received the experimental vaccine known as TG4010. The vaccine stimulates the immune system to destroy cancer cells.

The researchers hoped to stop the progression of the disease in at least 40% of the patients enrolled in the six-month study. If they reached that goal, they would consider the trial a success. To determine that, each participant underwent a CT scan every six weeks to see if the disease had spread.

At the end of the study, 32 of the 74 patients (43.2%) who had received the vaccine showed no signs of disease progression. Meanwhile, 35% of the study participants who received standard chemotherapy showed similar results.

The researchers write that the trial was a success and that the results suggest that the combination of vaccine and chemotherapy "translates to a better long-term outcome compared with a response obtained with chemotherapy alone."

The vaccine appeared to have other benefits as well. More patients in the vaccine group responded to treatment than patients who received only chemotherapy -- 41.9% compared to 28.4%. Also, for those patients who did respond to treatment, those given injections of the TG4010 vaccine had an average overall survival of 23.3 months, nearly twice that of patients in the comparison group.

Determining Who Will Benefit the Most

The researchers also discovered a potential biomarker that may allow doctors to better determine which patients are most likely to benefit from the vaccine, if it reaches the market.

According to the study, patients with a normal number of a specific type of natural killer cells did much better with the vaccine than patients with an increased number of the cells. Natural killer cells are a form of white blood cell that helps the body fight off cancer cells and cells infected with viruses.

These observations "point to the importance of patients' biological status as a predictor for success of therapeutic vaccination, and suggest that analysis of biological parameters should be part of the clinical developments in cancer immunotherapy," the researchers write.

This is a very important point, says Harry Raftopoulos, MD, an oncologist at the Monter Cancer Center in Lake Success, N.Y., who reviewed the study for WebMD.

"The most promising part of the study is where they say that rather than treat everyone with this vaccine, can we find a way to select appropriate patients to receive it," Raftopoulos says. "Teasing that out moves the field forward."

Overall, though, Raftopoulos felt the study results are not yet conclusive, given the small number of patients involved and the small differences in treatment outcomes between the two groups.

"I've seen a lot of early-phase trials that look promising only to be followed by larger ones that show no differences," he says.

Alan Sandler, MD, a lung cancer specialist at Oregon Health and Science University, is intrigued by the possibility that the researchers may have identified a potential biomarker for treatment.

"They met their endpoint, but the outcome overall seems modest," says Sandler. "But it is exciting that they were able to define a subset of patients that did well, and it is appropriate that they are going on to phase 3 trials."

The study was funded by Transgene SA, a French company specializing in immunotherapies for cancer and other infectious diseases, which is developing the TG4010 vaccine in partnership with Swiss drug maker Novartis, and by ADNA/OSEO, a French government-funded program for personalized medicine.

The American Cancer society estimates that just over 220,000 new cases of lung cancer will be diagnosed in the U.S. this year. The disease is expected to kill nearly 160,000 people.

Lung cancer accounts for more than a quarter of all cancers. It is the leading cause of cancer deaths among men and women, more than colon, breast and prostate cancers combined.