chaemotherapy and radiotherapy

[tommy666]

chaemotherapy and radiotherapy, both treatments to cure cancer, but whats the difference? and in what situations (and why) is one used over the other? what are the side effects? how do you do it/them? what happens when you do it/them?

[tommy666]

ok thanks. why doesnt radiotherapy also kill your own cells? how do the 2 treatments only attack the cancerous cells and not the normal ones?

[Chris4854]

Unfortunately they do affect the non cancerous cells as well which is why people on the treatments tend to feel very ill. Radiography can be more contained as it can be directed at the tumour.

[MrPahoehoe]

Unfortunately they do attack your own cells, which is why a decision is needed as to which treatment to use: otherwise the cancerous cells would be blasted by everything.

Not sure if this is exactly how radiotherapy works nowadays, but i remember it being explained a while ago. A focused beam of radiation is used: sort of like a laser of radiation that will pass right through your body, affecting all the cells it encounters. However enough exposure to kill the cancerous cells would also kill healthy cells, so the source of radiation is rotated around the body. The source is specifically aimed and rotated so that the point of the body that the radiation is always passing through, is the collection of cancerous cells. It will still affect healthy cells however, but no areas receive a dose as high as the unhealthy cells.

[tommy666]

ty

[rassling]

chemotherapy affects cells that multiply rapidly, which is what cancer cells do. that is why it also causes hair loss - hair cells are fast growing too.

[tommy666]

thanks for all the answers, it helped a lot. 1 more thing though, HOW does the chaemotherapy mostly/only target fast growing cells? how does it detect which cells are growing the fastest? how do both methods actually kill the cells? if cancer cells are sometimes created by radiation, why can radiation also kill them? shouldnt they just mutate again when exposed to radiation?

[LazyGun]

The level of radiation used in radiotherapy will kill cells. Radiation only increases the rate of mutation and therefore possible new cancer cells if it is at a lowish background rate over a period of time.

As far as the mechanism for Chemo is concerned, it doesnt actively target the cancer cells. It will indirectly target those fast dividing cells, which will principally be the cancerous cells. Chemo doesnt discriminate however; It is a poison, hence the side effects.

There is a form of Chemo that will actively target certain tumours or cancers.... this is the so called "magic bullet" treatment, where the chemotherapy molecule is linked to a monoclonal antibody which will recognise an antigen that is specific for a particular type of cancer. The problem with designing such a specific therapy is that you first have to isolate an antigen specific to that tumour, then ensure and demonstrate that it is not expressed on any other type of cell. Then you have to design an antibody to it, develop the monoclonal antibody then link it to a chemotherapy agent etcetc.

[kazza12345]

each cell has a "lifespan" or cell cycle. Different chemos interrupy the cells growth and development at different parts of the cells cycle, by (in some cases) depriving the cell of what it needs to continue growing/developing, causing deterioration and death to the cell. Different chemos are used in "regimes" specifically worked out by clinical trials and therefore target the cells in the different parts of the cycle. It dosent just detect fast growing cells, its just because their cell cycles are over so quickly that side effects become apparent more quickly and are more severe

For eample: if the chemo interrupted the cell cycle 3/4 of the way through its development, a cell that developed within a day would be affected 3/4 of the way through that day, but a cell that developed over a month would be affected after 3 weeks

when you have chemo, they make you drink lots of water in order for the chemo to go in, do it's job on the cancer cells, and go out quickly, thus not having time to effect the slower growing cells

[kazza12345]

as to the question of why use one over the other ... some tumours are known to be unresponsive to radiotherapy, some are known to be unresponsive to chemothareapy. Other factors will be taken into account eg, is the tumour attached to a vital organ (if so, probably no radiotherapy) is the person frail in health (if so, probably no chemo, as the side effects could be fatal)

mostly, there is researched evidence through clinical trial as to which combination works best, depending on the extrnal factors that the oncologist will refer to

[kazza12345]

sorry to go on

radiotherapy is given by a big machine, similar to an xray machine. The person has radiotherapy planning where the radiologist will work out where the beams are to be directed, how the person will lay etc. The "patient" is marked with an indelible "tattoo" to mark the place (sometimes, if for example you were having radiotherapy for a brain tumour, they will make a clear plastic mask so that it can be clamped to the bed so there is no possibility of the patient moving their head during the radiotherapy, limiting the damage to other cells)

After the planning, the patient will come back to the department (usually on another day )to start treatment. They will lie on a table while the radiotherapy machine is lined up, and the radiotherapy machine will circuit them (as explained above). It takes litereally a few minutes. In the uk radiotherapy depts usually have a tight schedule, and you might get an odd appoint ment time of, for example 11:17 am,(and they will stick to it!) depending on the regime, you will come back various times for this to happen (most usually between 5 and 15 days worth for curative treatment, 1-2 times for palliative treatment) Some cancers mean you have to come everyday for 6 weeks. Anyway, its all over in a few mins, and most people are free to leave straightaway. (Some people have 1/2 day off work and just go back afterwards)

chemotherapy is just a term for drugs, and can therefore be given in all the ways drugs can ie injection, infusion, tablets, intrathecal

[surreygirl]

Radiotherapy involves using a beam of high energy radiation to kill cancer cells but spare healthy cells. Treatment is carried out using a LINAC or linear accelerator, which accelerates a beam of electrons through a metre or so before they collide with a target, producing a beam of very high energy x-rays.

Any exposure to radiation increases our risk of developing cancer. Low doses such as having an x-ray can damage parts of our DNA which could then mutate and go on to develop cancer, however the risk of developing cancer from an x-ray is far far far low than the natural risk of developing cancer. Higher doses of radiation, such as those used in radiotherapy actually kill off the cell completely.

Radiotherpy aims to kill the cancer cells and spare the healthy cells, although since the tumour invariably lies within the body, in it inevitable some healthy cells are going to be damaged in reaching the tumour. Damage to healthy cells is minimised in two ways - firstly by having multiple points of entry of the beam (by rotating the head around the patient) with the beams all focussing on the tumour and thus the tumour receiving the highest dose, and also by dose fractionation - giving the treatment over a period of several weeks rather than all in one go to give healthy cells a chance to recover.

Radiotherpy can induce some symptons of radiation sickness - specifically fatigue and nausea. This is due to cells which rapidly divide are more susceptable to radiation damage and thus more likely to be killed. Such cells include the lining of the gut (resulting in nausea) and mitrochondria (which generate energy for the cells of the body), thus when killed fatigue sets in.