Hi, Thanks for writing in. Arm swelling is seen in many patients after breast surgery for cancer. There is increased amount of lymphatic fluid in the arm and this does not drain adequately after mastectomy. With time there is deposition of the fluid under the skin and the patient has swelling and edema. There is no specific treatment and wearing compression garment in the hand might reduce the swelling. Weakness during chemotherapy is due to the strong medicines which are given. The medicines kill the cancer cells and destroy them. After destruction there is release of toxins from the cancer cells which might circulate in the blood. This causes breathless and weakness. Please do not worry.