Why Haven't We Cured Cancer?

A question I have considered many a time over the last few months. But, as I began to learn more about this disease, I realised the scale of the challenge to be overcome. Here are a few reasons why.

1. Cancer is not a single disease, it is an umbrella term for a range of diseases.
Just like Dementia is an umbrella term for symptoms caused by a range of diseases like Alzheimer's, Cancer is a word that refers to a large array of different diseases that have one main thing in common - the cells ability to multiply and divide (potentially) infinitely. It is also why different types of Cancer's require different treatments.

2. Not every treatment works for everyone.
Even if two different people have the same type, subtype, stage and grade of Cancer, they can still respond differently to the same treatment. I was told at the start of my treatment that statistically 2/3 of people do not need radiotherapy after chemotherapy, but 1/3 do. This highlights the difference.

3. Research into targeted therapies is complicated.
The use of targeted therapies involves analysis of the tumour which can be used to predict what treatment is likely to work best for that patient, and they hold significant potential for improving the prognosis of patients. For example, in breast cancer, tests are carried out to determine whether or not oestrogen receptors are expressed in the tumour. If they are, the drug Tamoxifen is more likely to work in that patient, compared to one where oestrogen receptors are not expressed. However, even this is not a guarantee that the drug will work, as again this depends on stage and grade.

4. Some types of Cancer are harder to identify and then treat.
Pancreatic Cancer has one of the poorest prognosis of all the types of Cancer. This is because by the time the patient experiences symptoms and it is diagnosed, it is often late stage, and therefore not much can be done. Surgery is only an option for 50% of patients, and the 5 year survival rate is 5%.

5. Each Cancer can be caused by a different set of genetic mutations.
This answers why patients with the same Cancer and treatment can have different clinical responses. Knudson's multi hit hypothesis suggests that 5 or 6 'hits' or genetic mutations would have to occur in the DNA to call a cell truly cancerous, and also explains why Cancer is more common in old age - as more time has passed to allow these 5 or 6 hits. However, these 5 or 6 hits are not the same for each Cancer, so there is a potentially endless amount of genetic mutations that can lead to Cancer, that all need researching.