Unresectable Metastatic Gastrointestinal Stromal Tumor: Case 1 - Episode 2
Jonathan Strosberg, MD:The patient had stable disease on imatinib for roughly 2 years, but in 2016, she had progressive abdominal pain. CT scan showed growth in the primary tumor as well as a new liver metastasis. Imatinib was stopped and she was started on sunitinib 37.5 mg daily.
So, sunitinib targets the KIT receptor, among other receptors, and it was shown to substantially improve progression-free survival in the placebo-controlled study in patients who either progressed or were intolerant to first-line imatinib. Progression in GISTs can sometimes be a little misleading. We know that there are rare cases where patients initiate first-line therapy and their tumors, particularly liver metastases, can sometimes enlarge but also become more cystic. And in these cases, it’s important not to be misled. The increase in size does not necessarily imply disease progression, and the clue to that is more necrotic appearance to the tumor. Eventually, those tumors often start shrinking subsequently. But after 2 years of treatment, that’s when progression is almost expected in a high-grade GIST. And if the tumors are enlarging without this decrease in tumor enhancement, it probably represents a real progression.
Sometimes, we see specific sites of progression. For example, within a tumor that has become cystic, sometimes you’ll see growth of an enhancing tumor within the cystic tumor, and this really represents a site of resistance that implies localized progression. This patient probably has developed secondary resistance to imatinib. The patient was initially sensitive, and we know that further mutations in the KIT receptor lead to resistance to imatinib.
In the metastatic setting, generally we obtain either CT scans or MRIs of the abdomen and pelvis. In patients with high-grade tumors, we tend to do these scans fairly frequently. In patients with pretty stableespecially lower-grade—tumors, probably every 6 months would be appropriate. In the surveillance setting after curative resection, we tend to adjust our scan frequency to the risk and grade of the tumor. After the first couple of years, patients with relatively low-risk tumors can often be monitored annually and sometimes even less frequently.
Transcript edited for clarity.