Pain in muscles post breast cancer treatment.

In 2014, my mother was detected with breast cancer in her right breast. She was operated an given chemotherapy and radiotherapy. After the treatment was over she was declared fit and often called for check ups every two months. In Dec 2016 she again detected with some lipoma kind of thing inside the treated area for which she was again operated and reports showed that it was not cancerous. Recently, she started feeling pain in her muscles specially arms and below the thighs. She is also experiencing night sweats. Treatments are not helping at all. The pain is worsening and now extended to the back. Kindly tell me if any body felt the same and what treatment helped.