When a sarcoma returns after a period of time during which it cannot be detected after therapy has been completed, this is redefined as recurrent disease. Recurrent disease can be either a local recurrence (occurring at site of the original tumor) or metastatic disease (AKA distant recurrence which involves a spread of the tumor to distant site, like to the lungs). The risk of recurrence for cancer survivors is different for each person. It depends on many factors, including the type of cancer, the treatment received, and the length of time after treatment. It is not possible to guarantee that a person who has completed cancer treatment will never have their cancer come back. Even if after your treatment, it looks like your disease is completely gone - the fact remains that there is always a chance that there are some cancer cells left in your body that survived, even though they cannot be detected. These leftover cells can begin to grow and in due course cause recurrence.
A recurrent cancer starts with cancer cells that the first treatment didn’t fully remove or destroy. Some may have been too small to be detected in follow up tests, scans, or blood work. It is possible that sarcoma cells spread from the original tumor prior to surgery but were microscopic and not able to be detected. If chemotherapy was given before or after surgery and disease recurs, it is likely those cells were not affected by the chemotherapy. It means that a small number of cancer cells survived the treatment you received. If radiation was given and the tumor grows back within the area irradiated, these cells were not affected and can be considered resistant (sometimes referred to as refractory) disease. Over time, these cells grew into tumors or cancer that your doctor could finally detect as a recurrence.
After the new disease is found, tests will be done to determine if the recurrent cancer is the same as what you had before. Even when cancer has spread to a new location, it is still named after the part of the body where it started. For example, if breast cancer spreads to the bones, it is still called breast cancer (only with bone metastases).
Cancer is unpredictable. In some cases it will never come back, but in some cases it will. That’s why doctors cannot guarantee cancer will stay absent forever. Options for treatment will be determined by the type of recurrence, local or distant metastasis. The most common site of bone and soft tissue sarcoma metastasis is to the lungs, although tumors arising in the abdominal cavity more commonly spread to the liver and peritoneum. Many people want to quickly do anything possible to treat cancer that has recurred. There will likely be many treatment options that your doctor will discuss with you. You may also decide to seek a second opinion or get your health care in a national comprehensive cancer center that has more experience with your type of cancer. Clinical trials are also offered at this point, if they have not been considered previously.