[A Case of Rectal GIST under Long-Term Follow-Up with Oral Imatinib].

The patient was a 79-year-old man with complaints of defecation difficulties and constipation. CT scan showed a 7.5 cm diameter mass in the lower rectum, and biopsy revealed GIST. MRI findings suggested prostate invasion, and the patient was started treatment with imatinib. Six months later, the tumor shrank to 4.5 cm in diameter. However, the patient refused surgery and continued taking Imatinib. The tumor continued to shrink gradually. Currently, 7 years later at the age of 86, it is only 2 cm in diameter and its inside has almost completely been replaced with calcifications.