I had my markings done yesterday for my left Breast wall after having treatable Breast cancer twice in 10 months! I was told the radiotherapy comes through at an angle to protect your heart and lungs which is why they mark the left and right side, not sure how accurate this is but I believed them
Radiotherapy is very precise, so you need to be in the same position on the table each time you have it.
Markers are both sides so you can be properly aligned each time. You'll notice that before you start they adjust your position by millimetres to get you set exactly right.
