What if we could develop a vaccine to treat cancer? Vaccines have been an effective method to help eradicate many diseases since their discovery, and serve a key role in keeping people healthy. The most common use for a vaccine is to prevent disease.
However, they can also be useful in treating individuals already diagnosed. This could occur through injecting the patient with their own living immune cells, also called antigen presenting cells, that stimulate the immune system to fight disease. The antigen presenting cells mark specific antigens, which are harmful invaders, to be destroyed by T cells.
T cells are an important part of the immune system that will attack and destroy a specific antigen (whether that is a toxin, a bacterium, a virus, etc.) to prevent it from causing harm to the body. Through vaccination, it should be possible to activate a patient’s T cells that are specific to their tumors, which would be beneficial in destroying cancer cells. However, there has been a lack of effective cancer vaccine studies in clinical environments because previous tumor vaccination studies were based on only one specific antigen.
In a recent clinical trial, a vaccine was developed using multiple types of tumor antigens and some of the individual’s own white blood cells. Also included in the vaccine was bevacizumab, which is an antibody that helps prevent new blood vessels from forming. This suppresses tumor growth and gives T cells access to tumors. In addition, a low dose of a drug called cyclophosphamide was added to reduce regulatory T cells, a type of T cell that slows down the immune response. This vaccine was considered personalized because it contained the individual patient’s specific white blood cells.
This personalized vaccine was tested in a clinical environment with ovarian cancer patients to evaluate the effects of the vaccine on the patients’ immune systems. The researchers expected that this approach of combining effective interventions into one vaccination would provide a better immune response and increase the survival of patients.
Researchers treated 25 patients suffering from ovarian cancer with their vaccine and were followed for 2 years to evaluate their immune response. A relatively small sample size was used because this study was conducted at only one hospital and the main purpose was to evaluate the overall safety and biological activity of the vaccination. They chose ovarian cancer due to its low survival rate, lack of effective treatments, and expression of a large quantity of tumour antigens.
The researchers found that of the patients participating in the study, 2 partially responded to the vaccine (tumor size decreased), 13 showed no response, and in the remaining 11 patients, the tumor shrunk below the limit of detection. All of those who responded to the vaccine were still living at the end of the 2-year study. However, only 25% of those that showed no response survived. These results are even more impressive considering the patients participating in this study have already tried other standard treatments with no beneficial outcomes.
After receiving the vaccine, T cells were able to recognize tumor cells and were more efficient at killing tumors compared to before the vaccine. The patients participating in this study have all been in previous chemotherapy treatments and experienced periods of remission, which is when the symptoms of a disease are less severe or disappear, but relapsed. In over 60% of the patients that responded to the vaccine, their remission was longer than their previous remission experiences.
Overall, the scientists concluded that a personalized vaccine is a possible, durable, and safe approach both alone and when combined with other cancer treatments in ovarian cancer patients. The results from this study are significant because there have been no other previous studies that developed vaccinations to treat cancer that were effective on their own in a clinical setting. The success of this study supports the use of vaccination in larger and more diverse clinical trials of cancer treatment. It also demonstrates the potential of vaccination as an effective way to treat cancers.
