A gold standard for cancer care — why is chemotherapy so effective in the treatment of cancer?
The meaning of the word chemotherapy is the “treatment of disease by the use of chemical substances” and if I were to ask you to think of diseases where chemotherapy might be prescribed as a treatment, the first thought in your mind would probably be cancer. However, whilst chemotherapy is primarily thought of as a treatment for cancer, it is also considered an effective treatment for autoimmune and rheumatic conditions, where the side effect of a weakened immune system is advantageous.
But how does chemotherapy work? Why does it exhibit such specific side effects? And why is it so effective in the treatment of cancer?
Cancer is caused by genetic (DNA) mutations that affects the growth instructions in cells. As a result, cancer cells multiply quickly, forming clusters of abnormal cells known as tumours. Chemotherapy drugs acts on cells that are in the process of multiplying, or splitting into two, and so targets cancer cells very effectively. Each drug is different: some kill the cells when they are splitting, other drugs kill the cells when they are making copies of their genes before they split.
Chemotherapy can be given in many ways. A few of the most common ways include:
Chemotherapy drugs travel in the bloodstream which means it can kill cells almost anywhere in your body — this is known as systemic treatment. As mentioned, chemotherapy targets cells that are dividing; once humans are fully developed, cells don’t tend to divide as much and only do so to repair damage or when there is a bigger problem at play, such as cancer. There are parts of our body where cells do multiply quickly, for example the cells that line the inside of your mouth, those that line your intestines and those that are responsible for hair and nail growth. It is these fast-growing cells that are targeted by chemotherapy and where we associate some of the most common side effects, such as nausea, constipation, hair loss, and a weakened immune system.
The origins of chemotherapy are not as you might expect, in fact it was borne from war-time experimentation. Fritz Haber, a German chemist, played a great part in the development of chemical weapons for WWI and more specifically, the development of mustard gas: a bright cloud, a peppery smell in the air, and then 24 hours later itching, blisters, sores, and coughing up blood. Chemical experts later found that victims of mustard gas exposure had a reduced number of lymph and bone marrow cells. During this time, one of the very few commonly accepted principles of cancer was that it caused affected cells to multiply at a much higher rate. Scientists hypothesised that if mustard gas could kill ordinary cells, such as healthy lymph and bone marrow cells, it could probably kill cancerous ones too. And so, in August 1943, a cancer patient was given the first chemotherapy injection to treat the disease. With each treatment, his symptoms improved and the size of the tumour reduced; thus the beginnings of what we now know as chemotherapy emerged.
Today, there are more than 100 different types of chemotherapy drugs available, with new ones being developed all the time. Chemotherapy may be prescribed on its own, to try to cure the cancer completely (curative chemotherapy). Alternatively, it may be administered alongside other treatments to make them more effective, such as radiotherapy (chemoradiation); before surgery (neo-adjuvant chemotherapy); or after radiation/surgery to stop the cancer returning (adjuvant chemotherapy).
Chemotherapy, although often effective, is by no means a perfect treatment. With it being such a vital component in the way we treat cancer, work is now taking place to minimise the side-effects and ensure that each patient is on the right chemotherapy drug for them. Work into alternative therapies, such as immunotherapies, is ongoing and so it’ll be interesting to see what the future of cancer treatment brings.