Tumor markers for breast cancer are likely to be normal, especially for most breast cancer patients who have undergone surgical resection, and most of them are within the normal range on review. The main tumor markers for breast cancer recurrence monitoring are CA15-3 and carcinoembryonic antigen. If these two tumor markers are significantly elevated compared to the previous ones during regular review, breast cancer recurrence and metastasis should be highly suspected. However, not all breast cancer patients will have elevated tumor markers in case of recurrence or metastasis, some patients will have normal tumor markers from the beginning to the end. If the tumor markers are significantly higher than normal in patients with advanced breast cancer, a significant decrease in tumor markers after aggressive anti-tumor therapy will also indicate that the current treatment is effective in controlling breast cancer.