<s>[INST] Hi, My Mom was diagnosed with Stage IV colon cancer in March 2013. She never had a symptom. The only issue she had was out of breath when climbing the stairs..Tapped lungs, etc. She started chemo in April -did 2nd ct scan in August, showed tumor grew from 3.5cm to 3.7cm.. Started her on different type of chemo, just had another scan a month ago showed the tumor stabilized and the other small nodules have shrunk, however, scan showed a blood clot in her artery, she is now giving herself 2 injections a day which the Dr. is hoping will dissolve the clot. She hasn t had any chemo treatments for about 3 weeks now and is actually eating great and feeling better. My concern is I just talked to her and she had a pounding headache, any advice would be helpful, thank you- worried Daughter [/INST] Hi and welcome to Chat Doctor, thank you for your query. In her case there are several possible causes of headache. Most serious is metastasis into brain, but this is not so often in colon cancer. I think this is probably due to chemotherapy and headache is common side effect of it. So she should take some stronger painkillers such as opiate analgesics and do ct brain scan to rule out metastases. Wish you good health. Regards. </s>