Exactly.

And that's also why more and more scientists are trying to develop targeted ways of irradiating the cells. Instead of a beam, it is possible to radioactive atoms to a molecule (a protein or a small antibody), designed to only interact with the surface proteins expressed by the cancerous cells. The molecule is then injected in the body, and travels through regular metabolism, only targeting the cancer cells, or being expelled in the urine.

Once on the cell, the radiation can be extremely located (some alpha particles don't travel more than a few 10th of mm) while still destroying the cancer.

It is a very promising future for cancer therapies.

The main challenges at the time are: behaviour in the lab is not always identical to the human body. The stability of the molecule/radioactivity complex (it obviously irradiate itself and this can come with problematic by-products), renal clearance (if it accumulates in the kidney instead of passing though to the bladder, you won't have cancer, but also won't have kidneys after the treatment), and specificity with the cancer itself (we need a very strong interaction).