How does Immunotherapy work?
Normally, the immune cells in our body (Tumor Infiltrating Lymphocytes) keep the cancer cells under check and prevent their growth and proliferation. But sometimes, cancer cells can develop some mechanisms to escape form these immune cells from attacking them.
Immunotherapy works by preventing the cancer cells to escape from our immune cells, thereby, increasing the efficiency of immune cells to kill cancer cells. In short, it restores the body’s immune system to fight effectively against cancer cells.
What are the various types of Immunotherapy?
There are several types of immunotherapy available that are discussed below-
Immune Checkpoint Inhibitors
Most important immune cells in our body out T cells or T lymphocytes. These express PD-1 on their surface that usually binds to PDL-1 on the surface of normal cells. This interaction prevents the normal cells of our body to be killed by cancer cells.
But cancer cells take advantage of this and start to express PDL-1 on their surface, which makes them resistant to immune cells. In this way, they escape from being killed by the T lymphocytes.
Immune checkpoint inhibitors work by blocking these pathways that cancer cells develop and thereby increasing the efficiency of our immune system to kill cancer cells.
These are the proteins that bind to specific targets on cancer cells so that they are efficiently destroyed by the immune system. Normally, antibodies in our body identify and kill the viruses, fungi, bacteria that cause disease. These monoclonal antibodies are designed in a laboratory to act on specific targets on cancer cells.
For example, rituximab is an anti-CD20 monoclonal antibody that binds to CD20 receptors on the B cell surface which are then destroyed by the immune cells. In this way, it is useful in treating B cell lymphomas.
T Cell Therapy
This is also called as Adoptive T cell therapy. In this technique, T cells that are effective against cancer cells, are removed from the body. These are then selected and changed in laboratory and then grown in large batches and then reintroduced into the body of the patient. In this way, they are better equipped to fight against the cancer cells more efficiently.
Vaccines are substances that are prepared in laboratory to identify and kill certain antigens. Tumor cells are known to express antigens on their surface. Cancer vaccines are prepared against these antigens and then introduced in the body to recognize and kill the cancer cells that express such antigens.
There are some non-specific types of immunotherapy treatment available that kill cancer cells with a multi-pronged approach by activating various components of immune system. Interferons and Interlukins are examples of non-specific immunotherapy available for cancer treatment.
What are the cancers that are treated with Immunotherapy?
Immunotherapy may be used for treatment of multiple cancer types. With newer therapies coming up, the use of immunotherapy is increasing and the cancer types in which it mat be used are also increasing.
It may be used as initial treatment in some cancers, and after failure of previous treatment in others. In some cancers, its use requires some preliminary tests to be positive, whereas in others, it may be used irrespective of any testing.
So the decision to use immunotherapy for cancer is taken by the oncologist depending on multiple factors after complete assessment of the patient.
How do I know if I am a candidate for Immunotherapy?
As discussed above, it is decided based on multiple factors. But in some cases, certain preliminary investigations may be required assess the feasibility of immunotherapy .
Following is a list of some diagnostic tests that are usually performed to estimate the efficacy of immunotherapy for different cancer types:
Microsatellite Instability (MSI) or Mismatch Repair (MMR) Testing
MMR proteins are helpful in repairing the faults in the DNA. A mutation or modifications in the MMR genes (changes in the length of predetermined repetitive DNA elements, or microsatellite) may lead to MMR protein deficiency (dMMR) or MSI.
Depending on the extent of instability in the markers tested, tumors with the presence of MSI are classified as either MSI-H or MSI-low (MSI-L). Tumors without MSI are classified as microsatellite-stable (MSS). Patients with MSI-H status are almost always determined to have defective MMR (dMMR). MSI or MMR testing can be done using a validated next-generation sequencing (NGS) panel or immunohistochemical analysis.
MMR or MSI testing is recommended to be performed in patients who are candidates for the treatment with PD-1/L1 inhibitors. The MSI/MMR testing is also helpful in the diagnosis of Lynch syndrome, a common hereditary syndrome that is considered an important risk factor for the development of many cancer types.
Programmed Death-Ligand 1 (PD-L1) Testing
PD-L1 is a protein (ligand) commonly found on the surface of healthy human cells. PD-L1 (and other similar ligands) binds with the programmed cell death protein 1 (PD-1) receptor present on activated T- cells to prevent the attack of T-cells on the healthy tissue. Cancer cells take advantage of this mechanism and express PD-L1 on their surface to evade immune attack. PD-L1 testing can be done using a qualitative immunohistochemical analysis.
PD-L1 specific stains are used to detect the PD-L1 positive cells. For accurate PD-L1 evaluation, at least 100 tumor cells must be present in the PD-L1–stained tumor specimen. Then, the total number of viable tumor cells and PD-L1 staining cells (tumor cells, lymphocytes, macrophages) is computed to determine the Combined Positive Score (CPS). The CPS is defined as the number of PD-L1 staining cells divided by the total number of viable tumor cells, multiplied by 100. A tumor specimen is designated as PD-L1 expression positive if the CPS >/=1. PD-L1 testing is recommended in patients who are candidates for the treatment with PD-1/L1 inhibitors.
Tumor Mutational Burden
As per available pieces of evidence, tumor mutation burden has been proposed to be a predictive biomarker for the efficacy of immunotherapy, especially immune checkpoint inhibitors. It has been reported that patients with diverse tumor types and high tumors mutation burden (>/=16 mutations per megabase) are most likely to derive benefit from the immunotherapy.
Where can I get Immunotherapy in Delhi?
Dr Sunny Garg is a renowned Medical Oncologist in New Delhi with years of experience of treating cancer patients with Immunotherapy. He has been trained at premier institutes of country and has practiced in leading cancer hospitals in Delhi, and currently practicing at Manipal Hospital, Dwarka. He works in close collaboration with surgical and radiation oncologists, oncopathologists, nuclear medicine, and genetic counselors for comprehensive cancer care for the patients.
What is the Cost of Immunotherapy in Delhi?
Immunotherapy is usually costlier than other modalities of treatment like surgery, chemotherapy and radiation therapy. The cost usually depends on the type of immunotherapy and for how long it is being given.