How long does it take for breast cancer to metastasize? There is no absolute scientific data on this issue. Based on data from theoretical animal experiments, metastasis can occur within a few hours, tens of hours, several days, or even years. It should be understood in this way. I believe your question primarily concerns how long after breast cancer surgery metastasis might typically occur. Generally speaking, after comprehensive treatments such as surgery, chemotherapy, and endocrine therapy, the earliest metastases appear within a year. The peak incidence for most people is between two to three years after treatment, making this period critical for frequent check-ups. During the first two years, stringent, thorough examinations every three months are essential. After two years, check-ups every six months continue from the third to the fifth year. After five years, annual physical examinations are recommended. A second peak period for recurrence occurs around eight to nine years post-surgery, which is why the frequency of examinations increases again during this time.