Results from a new pilot study provide encouraging results on the use of a personalized cancer vaccine against melanoma. (A pilot study is an experiment conducted in a small group of patients to test the viability of a potential new treatment before it is tested in a larger group.) While the study group was small, all six of the patients with melanoma had a favorable response: their cancer did not return after they received treatment.1,2
Creating a cancer vaccine
Cancer vaccines aren’t like other vaccines you may receive, like those for measles, the flu, or shingles. A cancer vaccine is personalized to the individual and will only work for that person. To create a cancer vaccine, scientists take some of the individual’s cancer cells and look at its DNA. They compare the cancer cell DNA to the patient’s normal DNA to find where mutations have occurred. Some of the DNA causes the production of certain antigens, substances that are found on the surface of the cell. While some of the antigens found on cancer cells are the same as antigens on healthy cells, cancer cells also have unique antigens that can be used as a targeting tool, called neoantigens. After identifying several of the neoantigens (for this study, they used 13-20 different cancer-specific antigens), scientists create a vaccine which includes pieces of the antigens. Once introduced back into the patient’s body, the patient’s immune system kicks in, and T cells (a type of white blood cell) identify and destroy any cell that has those neoantigens.2
How the melanoma vaccine worked
In the pilot study, each patient received five shots of their personalized vaccine in the first month and booster shots at the 12- and 20-week mark. The vaccines appeared to work, as the T cells didn’t attack healthy tissue but focused on the cancer cells. Side effects from the vaccine included flu-like symptoms, redness at the site of the injection, rash, and fatigue.1,2
At the start of the trial, four of the participants had melanoma which had spread to the lymph nodes. Each of these participants remained cancer-free after their vaccination for the two years of follow-up from the study. Two additional trial participants had melanoma that had spread to the lungs and did have tumors return. However, after additional treatment with Keytruda® (pembrolizumab), the cancer was undetectable in their bodies. (Keytruda is a type of immunotherapy that is a monoclonal antibody, which helps the body’s T cells identify cancer cells for destruction.)1-3
The trial followed the patients for two years after the vaccines were administered, and the patients’ blood continued to show anti-melanoma T cells. This provides hope that the benefits of the vaccine remain in the body for a long time.1,2
Limitations of this trial
While this research is exciting, the trial does have limitations. It was a very small group of patients, and it is difficult to make any sweeping pronouncements about a treatment with such a small sample size. However, the results are promising enough to justify a larger trial.2
In addition, not every cancer is a good candidate for vaccination therapy. In fact, two potential participants were excluded from this study because their cancers didn’t have enough mutations to create a vaccine.2
Another criticism of this study was that there was no comparison arm, such as a placebo group or a group that received traditional treatment only. Without the comparison group, it is unclear if the vaccine was the true cause of the cancer’s disappearance.2
Participating in cancer research
While the research is still in its early stages and there are several more hurdles to overcome, targeted therapies like this one continue to be an exciting area of cancer research. If you are interested in participating in a clinical trial, talk to your doctor or and search for trials for your type of cancer below.4
Ott P, Hu Z, Keshin DB, et al. An immunogenic personal neoantigen vaccine for patients with melanoma. Nature. 2017 Jul;547(7662):217-221. doi:10.1038/nature22991.
Stat. Accessed online on 9/8/17 at https://www.statnews.com/2017/07/05/cancer-vaccine-melanoma/.
Keytruda product website, Merck & Co, Inc. Accessed online on 9/8/17 at https://www.keytruda.com/.
National Cancer Institute. Accessed online on 9/8/17 at https://www.cancer.gov/about-cancer/treatment/clinical-trials/search.