How are gamma rays used to treat cancer if they cause cancer?


I searched it up but it’s not very specific about how this works.

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Gamma rays can cause cancer because they damage cells, and *sometimes* when you damage a cell you mess up it’s DNA just right and bonk the wrong gene it turns the cell cancerous.

A “gamma knife” is a radiotherapy tool, it uses beams of radiation to murder cells in the target area. It uses more energy so it doesn’t just “damage” cells, it kills them.

By carefully targeting multiple beams from multiple directions they overlap on exactly the spot they want to remove. some cells in the path of the beam are still receiving a dangerous amount of gamma rays but that’s one of the tradeoffs for microwaving a tumour without cutting open the patient

Low doses of gamma rays cause cancer, large doses kill cells. You basically shoot the cancer with a laser beam until it’s dead. Any healthy cell you hit also die, so they won’t develop cancer either. They’re dead.

To put it simple: Gamma rays, like other forms of ionizing radiation, increase the risk of developing a cancer later. Thus, one is more likely to develop a (second) cancer due to the radioation used to treat the (first) cancer. As long as the probability for developing a second cancer is well below 100%*, it makes sense to treat the cancer you already have even if it makes you more likely to have a new cancer later. Better fix the accute problem first…

There is a lot more nuance to this, and quite a bit of math and computational modelling is used to minimise the side effects of such treatment. A lot of work has been done, and is still being done, to reduce the side effects.

*) Actual numbers vary a lot per type and size of the cancer to be treated. Quickly looking up some example numbers, a typical radiation dose of such treatment has maybe around 10% chance to cause a new cancer based on the “rule of thumb” numbers I recall from my training years ago. This means that the patient is more likely to have a second cancer for reasons not related to the treatment.

Basically how most cancer treatment work is by taking advantage that cancer cells more vulnerable than healthy cells. So you give just enough poison so the cancer dies and the healthy cells lives.

Gamma rays do the same, but yes gamma rays can also cause cancer which is a risk with the treatment. A great thing about radiation treatment is that it tuned quite precisely to hit an area that needs treatment, so with a small areal getting hit by the rays its relatively low risk of getting additional cancer from the treatment.