There are various reasons for back pain half a year after pancreatic head cancer surgery, such as postoperative reaction, tumor recurrence or metastasis, and it is necessary to go to the hospital for rechecking to clarify the cause of pain and do targeted treatment. 1. Postoperative reaction: some patients may have back pain after surgery, because there are many nerves at the back of pancreas, and the surgery process may affect the nerves and cause back pain. You can go to the hospital to check the relevant indexes, blood routine, abdominal ct and so on. 2. Tumor recurrence or metastasis: pancreatic head cancer may have recurrence and metastasis after surgery, and it is necessary to further improve the tumor indexes and imaging examination to clarify whether the back pain is caused by tumor recurrence or local recurrence. Before the cause of pain is clear, it is not recommended to take painkillers by oneself, and it is necessary to take targeted treatment under the guidance of doctor after review.