When we talk of treating cancer, we have either surgery, Radiation or chemo (drug therapy) and at times hormones too. We generally combine the above four in differing combinations depending on the cancer type and its stage.
Now we have an entirely new way to attack and cure even the most dangerous amongst these Cancers and that too even in the terminal stages of the illness called metastasis by unleashing one’s own immune system to kill these cells, a real breakthrough that has given us an entirely new option by a set of drugs and interventions. This new tool is known as CANCER IMMUNOTHERAPY. This branch of cancer treatment appears to have immense scope and the credit to establish this branch goes to these two brilliant scientists who were awarded NOBEL PRIZE in PHYSIOLOGY or MEDICINE only two years back in the year 2018. They are James P Allison (USA) and Tasuko Honjo (JAPAN).
Respect for this newest branch of cancer treatment went very high when 39th president of USA, Jimmy Carter at the age of 92 in the year 2015, was successfully treated with immunotherapy drug PEMBROLIZIMAB for malignant melanoma ,the dreaded cancer form he was suffering from had metastasised into his Brain . This drug could entirely clear the metastasis from his brain which astonished the entire world. Very soon he could resume his routine teaching schedule of school students which he has been doing ever since he laid down his office responsibilities.
These sets of immunotherapy drugs are popularly known as CHECKPOINT INHIBITORS. They are now in clinical use in failed cancers of lung, kidney, bladder, head and neck tumours besides malignant melanoma where it’s currently the first line of therapy.
WHAT ARE CHECKPOINT INHIBITORS?
Our blood carries certain lymphocytes known as T lymphocytes that fight infections or cancer cells which are new to us . These cells carry molecules on their surface known as CHECKPOINT MOLECULES that our body uses to shut them down when it needs to stop them. Cancer cells can lock into those checkpoint molecules crippling the T cells and therefore doesn’t allow them to attack and thwart the cancer cells.
Professor Allison could locate a checkpoint molecule called CTLA 4 and Dr Honjo discovered yet another molecule known as PD1 separately. They could develop monoclonal antibodies which could block those checkpoint molecules thus opening the T cells to act against these unwelcome cells .These discoveries made it possible to locate many such checkpoint molecules and subsequently developed respective blocking antibodies too . They alone or in combination could stop the checkpoints to function so that our own T cells shall be free to fight the cancerous and even infecting cells by taking the breaking paddles away from immune system defence.
Excitement surrounding this new field of cancer immunotherapy is so overwhelming that no cancer treatment is final until these drugs are given a try and in some of the cancers it is even the first modality of treatment as in the case of just mentioned malignant melanoma.
However ,the flip side is that it can at times turn against one’s own immune cells and cause uncontrollable damage. Therefore ,it has to be cautiously used to get the desired maximum benefit . As professor Alison said, use it as accelerer and put the break as and when required to regulate the immune system through these molecules and not just let it go.
The fact remains that as human beings are living longer, the incidence of cancer is increasing many fold . As high as one in three of us in our own lifetime are likely to suffer from different types of cancer and therefore such breakthroughs are of great value for the health of the entire mankind.
(Author is Professor and Head of Department of Medicine, RIMS, Ranchi)