The patient presented with a huge abdominal mass extending from the pelvis to the diaphragm (Figure 1). GIST diagnosis was confirmed by CD117 (KIT) immunohistochemistry. He began TKI treatment, requiring coadministration of an IV antiemetic with his first dose because of near-complete obstruction at the gastric outlet.

After 2 days of treatment

After 2 days of treatment, a rapid response to TKI therapy was observed and subsequently eliminated the need for the antiemetic agent.

The patient continued to experience rapid tumor shrinkage and symptomatic relief. At this point, it appeared that fluid began to enlarge the tumor, causing an increased tumor volume and abdominal swelling.

After 8 weeks

After 24 weeks

The patient underwent surgery after 39 weeks of treatment. The surgical team evacuated 7 liters of intratumoral fluid, facilitating removal of a residual compressed tumor mass measuring 30 x 30 x 15 cm. Pathology examination revealed that approximately 50% of the cells in the resected specimen were viable.

Following surgery, the patient was instructed to resume his TKI therapy immediately, but because of a misunderstanding, he inadvertently failed to do so. He returned to the clinic 2 months later with evidence of rapidly progressive disease in the liver and the appearance of a possible peritoneal implant.

Treatment with a TKI was reinstituted. One month later, there was definite regression of the liver metastases and disappearance of the possible peritoneal implant on CT. The patient underwent further surgery and remains free of disease on continued TKI therapy.

The presence of multiple risk factors in this case—most notably massive tumor size, tumor rupture, and postoperative evidence of residual viable disease—suggests that consideration of adjuvant treatment with a TKI may be warranted for patients after surgery for GIST whose disease has characteristics associated with a high risk for recurrence or spread. The rationale for adjuvant therapy may be particularly compelling in cases such as this one, in which the GIST exhibits responsiveness or stabilization during preoperative TKI administration.

The development of rapidly progressive disease soon after surgery in the absence of TKI therapy, and the prompt restoration of response after the TKI administration was resumed, underscore the importance of uninterrupted treatment with a TKI for this patient.