Extended treatment with adjuvant imatinib (IM) for patients (pts) with high-risk primary gastrointestinal stromal tumor (GIST): The PERSIST-5 study.

Abstract

11009 Background: Adjuvant IM reduces risk of recurrence and improves survival in pts with high-risk primary GIST. Joensuu et al 2016 demonstrated higher 5-yr overall survival (OS) rates of 91.9% vs 85.3% in pts treated with adjuvant IM for 3 vs 1 yr, respectively. It is unknown if further extension of treatment duration can improve outcome. Methods: PERSIST-5 is a single-arm, phase II trial that enrolled pts ≥18 yrs of age, who underwent macroscopically complete resection of primary KIT (+) GIST with high risk of recurrence within 12 wks prior to IM treatment. High risk was defined as primary GIST (any site) ≥2 cm with a mitotic count ≥ 5/50 HPF or non-gastric primary GIST ≥5 cm. Pts were treated with IM 400 mg/d for 5 yrs or until progression, relapse, or intolerance. Primary endpoint was recurrence-free survival (RFS, defined as time of treatment start to first recurrence or death). Results: IM was administered to 91 pts with a median age of 60 yrs (range 30-90). Median tumor size was 6.5 cm (range 2.3-30 cm; 55% gastric origin). Median treatment duration was 55.7 mos (range, 0.5-75). Forty-six (50.5%) pts completed study treatment. The 5- and 8-yr estimated RFS rates were 90% (95% CI, 80-95) and 81% (95% CI, 62-91), respectively. The 5- and 8 year OS rate was 95% (95% CI, 86-99). There were 7 recurrences; 1 pt recurred and died while on IM ( PDGFRA D842V mutation) and 6 pts recurred after IM discontinuation. Two pts died after IM discontinuation, unrelated to study treatment and without recurrence. Forty-five pts discontinued study treatment; common reasons included patient choice (20%), adverse events (AEs, 17%), protocol deviation (4%), and loss of follow-up (4%). The most common AEs of all grades (regardless of relationship to IM) were nausea (71%), diarrhea (63%), fatigue (50%), muscle spasm (41%), vomiting (39%), and periorbital edema (34%). Conclusions: Five yrs of IM treatment was effective in preventing recurrence in pts with sensitive mutations who underwent resection of primary GIST. Nearly half of the patients discontinued treatment early, and most recurrences occurred after IM discontinuation. Clinical trial information: NCT00867113.