Long-term adjuvant therapy for high-risk gastrointestinal stromal tumors in the real world

Purpose Three years of adjuvant imatinib is the standard therapy for gastrointestinal stromal tumors (GISTs) with high-risk features. The prognostic effects of long-term adjuvant therapy are unknown. Patients and methods The prospective registry study recruited 515 patients with high-risk GISTs between Dec. 2012 and Dec. 2015 were analyzed. The primary endpoint was recurrence-free survival (RFS), and secondary endpoints include overall survival (OS) and safety. The study was designed to compare RFS after 3.5 years of 3-year adjuvant therapy (3.0 ± 0.5 years: 3-year group) with that of more than 3.5 years (median 5.2 years: longer group). Results Five-year RFS and 5-year OS were 68.2% (95% confidence interval [CI] 63.8–72.1) and 92.3% (95% CI 89.5–94.4), respectively. The recurrence rate during adjuvant was estimated to be 2.9/100 person-years (95% CI 2.0–4.1) and those after the end of adjuvant, which appeared similar irrespective of the adjuvant duration or reason to stop adjuvant, were estimated 12.0/100 person-years (95% CI 10.2–14.0). The 5-year RFS rates of 3-year and longer groups were 78.7% (95% CI 70.8–84.7) and 92.7% (95% CI 85.2–96.4), respectively. RFS after 3.5 years of the longer group was significantly better than that of the 3-year group (adjusted hazard ratio [HR] 0.56; 95% CI 0.39–0.78; P < 0.001). Conclusion The recurrence risk of high-risk GISTs after adjuvant therapy is similar irrespective of the adjuvant duration and imatinib adjuvant may not cure but may delay recurrence. RFS after long-term adjuvant therapy appeared better than that after 3-year adjuvant.