Carcinoembryonic antigen 5.61ng/ml after breast cancer treatment may be caused by pneumonia and breast cancer recurrence, which need to take anti-inflammatory and anti-cancer treatment according to the cause. 1. Pneumonia: the body of breast cancer patients is weak after treatment, which can easily cause pneumonia and other problems, thus carcinoembryonic antigen 5.61ng/ml occurs. Most of the patients can get back to normal after taking antibiotics and antiviral medicines, such as azithromycin, oseltamivir and ganciclovir, and so on. 2. Adenocarcinoma recurrence: if carcinoembryonic antigen 5.61ng/ml occurs again after recovery from breast cancer treatment, it may be caused by tumor recurrence and metastasis, which needs to be diagnosed by CT, MRI and other examinations, and treated with surgery, local radiotherapy, chemotherapy and other means. If carcinoembryonic antigen is elevated in breast cancer patients, it is necessary to do a good job of testing and examination to clarify the cause of the disease and take timely treatment to avoid aggravation of the disease.