Im not a medical expert but here is my understanding about the whole subject:
Chemotherapy is more like a general term use to denote treatments that involves the use of chemical agents to directly affect cancer cell growth. Depending on the chemical agent, there are many ways in which a chemo therapy can do the tasks.
For example, some agents can reactivate apoptosis via "mimicking" natural signals that facilitates autocell death, some agents inhibits ETS and/or phosphorylation process affecting energy utilization, Most agents affects amino acid/DNA/RNA synthesis which in turn affects cell divisions and cell repair.
I dont understand the exact process but some chemo agents are more like catalysts/enzymes/inhibitors that remain unchanged and active until the body dilutes it and flushes it out of the system. Others may probably reacts immediately to some of the chemicals in the body and thus immediately losses its potency once it accomplish its tasks. others create by-products that also affect cancer cells in the negative way.
So it depends on the chemical agents. If its an inhibitor/enzymatic type and/or creates toxic by-products then it could kill/affect the parent cells as well as its progenies for a relatively long while.
Now with regards to cancer cell developing "immunity" to chemotherapy, there are many theories like evolution or natural selection. Research said that a malignant mass are usually a population of different cell mutations each having a different modes of operation and that they are still dynamically mutating and changing during their entire development.
This means that some cancer cells in a malignant tumor could be very vulnerable to a certain chemo agents while others may be more resilient. So during chemotherapy the chemical agents may kill the susceptibles cancer cells while leaving the more resilient one unharmed (with less competition in their neighborhood). This was said to be the reason why some tumor growth coming back becoming more aggressive and immune to a certain a chemo protocol.
Current proposals includes treating cancer as a chronic disease with emphasize on keeping the growth of the different populations of cancer cells in check relative to each other and ensuring that the more aggressive and immune cancer cells wont dominate the more controllable ones.
It doesn't really, they develop resistance to chemo which is why many chemo regimes consist of two or more types of chemo. My own was three different chemos, each of which attacked the cancer cells in different ways making it less likely that one mutation in the cancer could make it immune.
thankyou so much guys.
and great post, JoyfulofJourney
I guess I still wonder, if chemo attacks all splitting cells, it doesn't finish it's course with EVERY cancer cell dead (metasized or not). and why 'residual' disease is usually left with advanced cancer.
When a cell divides the chromosomes in the nucleus of the cell (the cells instruction manual) need to be replicated.
There are various stages to this process and different chemo agents act on different parts of the process. This is why a combination of drugs are often given.
For the chemo to work, cells need to be actively dividing when the treatment is given (this is why a course of treatment is given rather than just one dose).
While a cell is in the process of dividing both the original cell and the "daughter" cell being formed are potentially vulnerable to the effects of the treatment so both could be killed. There is a useful explanation including a diagram on our website here
It isn’t possible to say for an individual patient why a treatment wasn’t completely successful and why all the cancer cells might not have been killed. But it is possible that the explanation above might contribute to this. Also, it might be that parts of the cancer did not have a good enough blood supply and so the chemo couldn’t reach all the cancerous cells, or that some of the cancer cells developed resistance to the chemotherapy drugs being used.
But as I have said it isn’t always clear why in some cases treatment isn’t completely successful.
Usually, if the cancer is treated, before it has spread widely and when it is still relatively small there is a much greater chance of chemotherapy being effective.
As this is quite complex, and some of your questions might not be answerable, I wonder if it would help to talk to us about it on our phone line. You can call us on 0808 800 4040 between 9am and 5pm Monday to Friday.
