This relatively new approach to the treatment of cancer makes use of the body’s immune system to destroy cancer cells. There are four main mechanisms used for immunotherapy treatments:
- Boosting the immune system
- Making use of antibodies that attach to cancer cell surface proteins. Drugs are called monoclonal antibodies and commonly end in -mib or -mab
- Encouraging white blood cells to destroy cancer
- Adaptive cell transfer and vaccines.
Many of our own cells, such as neutrophils, macrophages and especially T-cells, have the potential to respond to cancer in the way they fight other pathogens as they recognise ‘foreign’ cells and help eliminate them.
Monoclonal antibodies are Y-shaped proteins that bind to cancer cells, making them more recognisable to the immune system and stimulate the naturally occurring ‘killer cell’ activity. Some stimulate cell death themselves whilst others can be bound to a cytotoxic drug. Their main indications include lung cancer, head and neck cancer, Hodgkin’s lymphoma and malignant melanoma where combined therapies are providing encouraging results for advanced or metastatic disease.
Vaccines can be developed by isolating immunogenic peptides from cancer cells but they are less effective than the method where patients’ own dendritic (messenger) cells are extracted, incubated with cancer cell fragments then re-injected. Genetically modified viruses with selectivity for cancer cells are also being used – injected directly into solid tumours. These burst cancer cells, which creates debris that is mopped up by dendritic cells. Research is focussed on gene therapy with a licensed treatment now available for metastatic melanoma.
Adoptive cell transfers
Another advance is seen in adoptive cell transfers which is specifically developed to each individual patient. T-cells are removed, genetically modified/engineered and administered back to the patient. Trials have shown cure in some patients, however, this involves dozens of stages and healthcare professionals and is almost prohibitively expensive at present.
What to look out for if caring for a patient receiving immunotherapy
Although these treatments are generally less directly toxic than chemotherapy, they do have their own adverse effects which are largely a result of the heightened immune system. These ‘auto-immune’ reactions most commonly affect the skin, GI tract, liver and endocrine systems and unless treated promptly with steroids/immunosuppression they may lead to life-threatening complications. Symptoms of concern would include rash, diarrhoea or colitis, endocrinopathy e.g. thyroid function changes, nephritis and renal dysfunction and pneumonitis. There may be considerable delay in onset of adverse events, so skin rashes may not be seen for around 10 months after treatment and unexplained diarrhoea 3 months after treatment may be an attributable side effect.
Clear adverse event guidelines are essential and will be available at the patient’s treatment centre.