An introduction to risk of recurrence in GIST.
Some tumors can be removed by surgery and pose little risk of coming back. This type of tumor is called a benign tumor. However, other tumors may have a higher risk of coming back. These tumors are called malignant tumors. If a tumor returns after surgery, it is called a recurrence. Many GIST experts consider all GISTs to have some malignant potential. Others consider most very small GISTs (less than 2cm in size) with a low mitotic rate to be benign.
Most cancers arise from a single tumor. This tumor is called a primary tumor. After surgery, a tumor can return at the same site (a local recurrence) or a new tumor can occur at a different site. A new tumor at a different site is called a metastasis. Metastases can be present at the time of diagnosis or they can appear sometime after surgery (a recurrence).
Metastases (commonly called “mets”) form when tumor cells detach from the primary tumor and travel through the circulation (blood, lymph) and attach in distant locations. These tumor cells then act as seeds for new tumors.
There is a perception that all GISTs have a high chance of a recurrence after surgery. This is not the case. In fact, in a large phase III trial for preventative Gleevec, about 45% of the patients entering the trial had a low risk of recurrence. The chart below, from a different series of patients, shows a similar pattern, with 45% of these patients either low or very low risk of recurrence.
The chart at right was adapted from a study of GIST patients in western Sweden. It gives a rough idea of how many GIST patients fit into each risk category. Other series of patients might have somewhat different ratios.
There are several different methods used to classify the risk of recurrence in GIST. Some have advantages over others for specific cases (for example, if the primary tumor site is unknown, one method has advantages over others).
Knowing your risk of recurrence is especially important if you are considering preventative Gleevec. Patients with a low risk or very low risk tumor may not need to take adjuvant Gleevec. At least three years of preventative Gleevec is recommended for GIST patients with a high risk of recurrence. In the United States preventative Gleevec is also recommended for patients with intermediate risk, although the duration of treatment is not specified(1). Mutational analysis plays a role as well and European Guidelines do not recommend preventative Gleevec for the D842V mutation that occurs in about 5% of GIST patients, as this mutation is not responsive to Gleevec.
1. NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines)
Soft Tissue Sarcoma, Version 2.2012