Bone Scan

I have just finished radiotherapy treatment after a breast tumour removal which didn’t spread to my lymph nodes, the radiotherapist phone today for my phone check up and after going through everything she said that a bone scan had been requested.  Now worried why I need this.  I didn’t think at the time to ask her as I didn’t know the significance of it but when I looked it up in google it says it could be to check if the cancer has spread. Now I am very worried.  Has this happened to anyone else?