The stage of breast cancer when cancer cells do not remain in the original cancer site and spread out to other parts of the body is called metastatic breast cancer. This is the stage when the cancer is fully advanced. Even if you have been successfully treated for breast cancer, there is a chance that some cancer cells do not die, and later spread out through blood and lymphatic vessels to other body organs. This process is known as metastasis of breast cancer.
Metastasis can occur due to three reasons. The first reason has already been stated, that is, when some cancer cells escape from treatments and make cancer recur. The second is when, during a treatment, the cancer goes on advancing, and starts developing tumors in other organs, and sometimes, when cancer is diagnosed so late due to carelessness of the patient or inefficiency of medical professionals, that it has already metastasized to other parts of the body.
When breast cancer recurs, the breasts, bones, lungs, chest wall, liver and/or brain start developing it, and show changes. Breast cancer has the highest risk of spreading. If another kind of cancer develops after breast cancer has been treated, it is probably breast cancer recurring. This is good news, because breast cancer is more treatable than any other kind of cancer. Also, if the cancer comes back in the breast that was not diseased earlier, it is probably a new cancer, and not a recurrence.
It is very important to know about metastatic breast cancer because around 30% of women with breast cancer are later diagnosed with metastatic cancer. Metastatic breast cancer is best treatable when no organ, specifically the lungs and brain, develop cancer, or when the cancer cells show traces of estrogen or progesterone hormone receptors, or, when tumors still respond to therapies, or when there have not been many treatments the patient has already availed.
For treatment of metastatic breast cancer, chemotherapy, immune therapy, hormone treatment, radiation therapy, regular mammograms, bone scans, ultrasounds, PET scans, MRIs, CT scans, etc. are adopted. The treatment is extensive, and involves a lot of specialists. The treatments also vary according to their purpose. There are systemic treatments (like anti-estrogen and chemotherapy) that concentrate on curing every part of the body, local treatments (like surgeries on the lines of mastectomy and lumpectomy and radiation therapy) which focus on curing and killing the cancer in specific areas where the cancer has spread to, and treatments which are focused on just relieving the pain of the victim.
A lot of research is going into slowing down and completely stopping further advancement of metastatic breast cancer. Even though this is the worst phase of your cancer, it is important that you know that many women with the metastatic disease have lived happily and normally while taking their treatment. You will have to decide when to end your treatment, for the higher the number of treatments you take, the higher the side-effects. This decision is the hardest to take, but you will know you have tried everything, prolonged your life as much as you could have. Spend the rest of your life being happy, and taking regular medication. Happiness is known for prolonging life, too.