One of the most exciting breakthroughs in the medical world announced in 2023 was the massive research going on to use vaccines to treat cancer. Dr. Vinod Balachandran from Sloan Kettering in New York reported on a Phase I study using an mRNA vaccine and an immunotherapy drug, Atezolizumab, in 16 patients with pancreatic cancer who had surgery and the usual chemotherapy. Those 16 patients’ white blood cells were removed, altered to target the cancer cells, then were reintroduced into their bodies. Eight patients were still alive after three years with no recurrence, and they continued to show T cells that were responsive to the tumour cells. In comparison, the five-year survival rates traditionally are eight to 10 per cent.

Let’s back up a bit and look at the history and challenges in developing vaccines. In 1988, the first vaccine was approved for use in prostate cancer. It was combined with an adjuvant to be used in resistant cases who had failed traditional treatment. In 1990, they started using BCG, a vaccine for tuberculosis, for bladder cancer which was administered into the bladder. In February 2023, Merck, Sharp and Dohme were approved to use a mRNA vaccine combined with Pembrilizumab for treatment for melanoma. There were challenges. The first difficulty was identifying antigens on the cancer cells that are specific to that cancer. The more specific it is, the more accurate the immune system will be in identifying and destroying the wayward cells. Because cancer develops from normal cells and the immune system is designed not to attack host cells, the T cells fail to recognize them. Drugs to unmask this protective covering can help the T cells identify and destroy the cancer cells. Larger tumours need more than just vaccines, and appropriate matching immune modulators that unmask the cancer need to be found. Lastly, older and sicker people who have weakened immune systems may be unable to respond with a vigorous immune defence.

What cancers are being studied? The focus is on cancers that have a devastating prognosis with a high rate of recurrence, such as:

1. Hepatocellular cancer, that arises in people who have hepatitis B or C, cirrhosis, non-alcoholic fatty liver

2. Pancreatic cancer

3. Malignant melanoma

4. Bladder cancer

5. Brain cancer

6. Colorectal cancer

7. Kidney cancer

8. Leukemia

9. Lung cancer

10. Prostate cancer

11. Multiple Myeloma, including Smouldering Melanoma, or in near remission

TYPES OF VACCINES

• Dendritic cells: Antigens are identified, dendritic cells from the patient are genetically engineered to display the antigens. This turns on the T cells that allows them to identify the tumour cells.

• Viral vector based: a virus is used to get the antigens into the system to trigger a response against the tumour.

• mRNA: the technique used in the Covid vaccine in which host cells are instructed to produce specific antigens to trigger response to cancer cells.

• Bacteria vector: weakened bacteria BCG is injected to activate immune system, similar to older vaccines.

• In-situ vaccines: immune activity drugs are injected directly into larger tumours, which unmask the cancer so the immune system can identify them.

• Oncoltyic viral therapy: a herpes simplex virus is injected into the tumour where it infects and breaks down cancer cells. Their cell death causes an immune response and identifies other cells that may have metastasized throughout the body and destroys them. This is used in malignant melanoma. Unlike many of the other methods, this is associated with many side effects.

As you can see, this is complicated medicine, but very exciting! So many centres are actively working to solve this problem. In 2022, it represented $6.8 billion, and is expected to rise to $20.2 billion by 2032 in the U.S. alone. I feel confident that with so many great minds working on this puzzle, we will have many more options to treat cancer within our lifetime!

Dr. Vicki Holmes is a Saskatoon retired family physician who has a special interest in Palliative Care and Women’s Health. She is passionate about sharing medical information with the public! (Vicki’s Photo: Memories by Mandy)

-Dr Vicki Holmes