Fourteen-year follow-up results of imatinib therapy in patients with unresectable and metastatic gastrointestinal stromal tumors.

Background: Imatinib therapy is the gold standard for the treatment of unresectable and metastatic gastrointestinal stromal tumors (GISTs). However, few studies have reported the long-term outcomes of the treatment.

Methods: Seventy patients who underwent imatinib therapy for unresectable and metastatic GISTs were enrolled between 2001 and 2009, and follow-up data were collected until October 2023. One hundred and sixty-eight months had passed since the final enrollment. The outcome measures were patient survival and the status of GIST and imatinib therapy. The cumulative incidence of disease progression (PD) and the chronological changes in PD hazard rate (HR) were also analyzed.

Results: The 5-, 10-, 15-, and 20-year overall survival rates were 64.3%, 30.0%, 16.8%, and 12.2%, respectively. Sixty of the 70 enrolled patients died before the data cutoff date: 47 (78.3%) patients died of GIST progression while the remaining 13 (21.7%) died of diseases other than GISTs. The cumulative incidence of PD logarithmically increased, and PD continued even after 10 years of treatment. PD HR decreased over time to reach the lowest value at 9.6 years after the initiation of treatment (HR 0.00027; 95% CI 0.00007-0.00174) and after that formed a small peak at 13 years (HR 0.00144; 95% CI 0.00043-0.00436).

Conclusions: Imatinib therapy showed high clinical efficacy in terms of long-term survival in GIST patients. However, patients undergoing imatinib therapy were at continuous risk of PD even after the 10-year treatment. Long-term treatment and follow-up beyond 10 years are necessary for unresectable and metastatic GIST patients.