A case of a gastrointestinal stromal tumor of the rectum effectively treated with continuously-administered regorafenib after failure of imatinib and sunitinib

Regorafenib is recommended as a third-line treatment for unresectable gastrointestinal stromal tumors (GIST). It is usually administered in a repeating cycle of three-weeks on and one-week off. We describe a patient with an unresectable GIST in the pelvic cavity who complained of pelvic pain while taking the one-week break from regorafenib administration. Subsequently, we reduced the dosage to one level and regorafenib was continuously administered. As a result, the adverse events were improved and the antitumor effect against the GIST was retained. The continuous administration of reduced-dose regorafenib could be considered a viable dosage adjustment in specific situations.