Can someone with a pacemaker, receive radiation therapy near the pacemaker?

Atleast 5 cm away: It is not safe to be in direct field of radiation. 5 cm away usually offers acceptable drop of dose to make it safe for most pacemakers. At times we may ask to have the pacemaker moved out of the radiation field.

It depends: Radiation therapy near the pacemaker generator (the battery pack) can damage the device. If the beam is expected to touch the generator, often the pacemaker generator would have to be moved to prevent damage.

We Usually Move It: It depends on the specific treatment plan but ionizing radiation, the goal of cancer therapy, can cause unexpected malfunctions in electronic circuits, so we usually take the existing pacemaker out and install a new system on the other side in these rare cases. Only certain pacemaker docs have the ability to fully remove a system, and a reasonable amount of skill is required for safety.