Immunotherapy

The cancer treatment known as immunotherapy works by boosting the body’s natural defenses in order to fight cancer. This therapy works through the use of substances made either within the body or by a laboratory to boost the immune functions of a patient.

Immunotherapy can work by:

• Slowing the growth of cancerous cells
• Stopping the spread of cancer
• Boosting the immune system to better fight cancerous cells
  
  
  

Immunotherapy works by attacking cancer cells and stopping the spread to healthy parts of the body. Occasionally, immunotherapy results in the immune system attacking healthy cells, thus leading to side effects. The side effects of immunotherapy can range from mild to severe.

Side effects may include:

• Skin redness, blistering or dryness
• Flu-like symptoms
• Muscle aches
• Shortness of breath
• Leg swelling
• Sinus congestion
• Headaches
• Weight gain
• Diarrhea
• Hormone changes

Most side effects can be treated though palliative care. Palliative care should be a part of your overall cancer treatment plan, so discuss this with your oncology team for further information.

There are many different types of immunotherapy treatments.

Oncolytic Virus Therapy

Oncolytic virus therapy, first approved in 2015, makes use of genetically modified viruses in order to kill cancerous cells. The virus is injected into the tumour, causing the cancer cells to burst and die. As these cancer cells die, they release a substance known as antigens which the body’s immune system targets and kills.

Side effects of oncolytic virus therapy may include:

• Fatigue
• Fever
• Chills
• Nausea
• Flu-like symptoms
• Pain at the injection site
  
  
  

Monoclonal Antibodies and Tumour-Agnostic Therapies

When the body detects a harmful substance within the body, it produces antibodies to get rid of any impending infection. Scientists have used this concept in the creation of laboratory-made monoclonal antibodies. These are often used to target any abnormal proteins within the body that allow cancer to spread. Immunotherapy is also used alongside of monoclonal antibodies in order to highlight specific cells for the immune system to locate and destroy.

Monoclonal antibody clinical trials are currently ongoing. The use of checkpoint inhibitors known as tumour-agnostic treatments are used to treat tumours throughout the body by focusing on specific gene changes. One current FDA approved monoclonal antibody is the ‘pembrolizumab’, which is used to treat metastatic tumours. This treatment can only be used with tumours with the specific genetic change known as microsatellite instability-high (MSI-H), or DNA mismatch repair deficiency (dMMR). Tumours with these conditions for not allow for DNA to repair, and thus making it easy for immune cells to attack the tumour.

Non-specific Immunotherapies

Similar to monoclonal antibodies, non-specific immunotherapies also work to aid the immune system in the destruction of cancer cells. Typically, non-specific immunotherapies are administered at the same time as other cancer treatments. In some instances, non-specific immunotherapies are administered as the only cancer treatment.

There are two common non-specific immunotherapies:

• Interferons work to slow the growth of cancerous cells whilst aiding the immune system in fighting cancer. The most common interferon is the laboratory-made ‘interferon alpha’.
• Interleukins work to help the immune system produce cells that are able to destroy cancer cells. The most common interleukin is the laboratory-made ‘interleukin-2’, which can be used to treat kidney cancer or certain types of skin cancer.

T-Cell Therapy

T-cells are the immune cells within a body that fight off infection. When undergoing T-cell therapy, these cells are removed from the patient’s blood and transformed in a laboratory to have receptors (proteins) placed within them and then are returned to the patient’s body. This process allows the body to recognize cancer cells and destroy them. This is known as chimeric antigen receptor (CAR) T-cell therapy. This method has been particularly successful in treating certain blood cancers.

Cancer vaccines

Doctors and researchers are beginning to create cancer prevention vaccines to stop healthy people developing certain cancers. Cancer vaccines have been developed to expose the body’s immune system to a particular antigen – a substance that is not normally a part of the body. This exposure will prompt the immune system to recognize this particular antigen and proceed to destroy any related materials that it recognizes. The immune system is left with what is known as a “memory” and will respond the same way when this antigen is detected in the future.

In some instances, cancer vaccines are made specifically for a patient from their tumour sample. In order to do this, surgery is first needed to gather a large enough tumour sample to create the vaccine. For those who are given more generic cancer vaccines, these are used to target specific antigens that have been located within the tumour.

Generally speaking, most cancer treatment vaccines are only available through clinical trials, however an FDA approved treatment for metastatic prostate cancer was created in 2010, known as sipuleucel-T (Provenge). Sipuleucel-T is created for individual patients through the following steps:

1. White blood cells are collected from the patient’s blood
2. These white cells are modified to target prostate cancer cells
3. These modified cells are injected into the patient, similar to a blood transfusion.
4. The modified cells pass this “memory” on to the rest of the immune system in order to locate and destroy prostate cancer cells.

There are currently only two FDA approved cancer prevention vaccines available:

• The Human papillomavirus (HPV) vaccine has been used to prevent cervical, vaginal and vulvar cancer, anal cancer and genital warts. The HPV vaccine may also work to prevent oral cancer, although this is yet to be FDA approved.
  
  
• The Hepatitis B vaccine has been used to prevent hepatitis b (HBV) infection, which can lead to liver cancer if it is within the body for an extended length of time.
  
  
  

Current Limitations

Developing cancer vaccines is a difficult process because:

• Cancer cells work by suppressing the immune system, which enables it to grow and spread.
• Cancer cells develop from the healthy cells of a person’s body. As they are “natural” the immune system may not recognize them as harmful and does not attack them.
• Advanced tumours are more difficult to remove.
• Patients with weaker immune systems cannot produce a strong immune response following a vaccination. This severely limits the strength of a vaccine making it difficult to aid in the cancer treatment.

It is for these reasons that small or early-stage cancers are better suited to cancer treatment vaccines.

Questions to Consider

• Do you recommend immunotherapy and which type do you recommend?
• What are the long term goals of this treatment?
• Will this be my only treatment path?
• What is the treatment schedule?
• What are the side effects, both long and short term?
• How will this affect my daily life?
• Are there any available clinical trials?
• Do you have further information?