Extended High-Risk GIST Follow-Up Confirms 3-Year Adjuvant Imatinib Benefit

Author: By Lynda Williams, Senior medwireNews Reporter 

medwireNews: Ten-year study findings confirm that adjuvant imatinib given for 3 years offers superior survival outcomes to a 1-year regimen for patients with a high-risk gastrointestinal stromal tumour (GIST). 

The third analysis of the SSGXVIII/AIO trial was reported at the virtual 2020 ASCO Annual Meeting by Peter Reichardt, from Helios Klinikum Berlin-Buch in Germany, and simultaneously published in JAMA Oncology. 

The findings are consistent with the earlier analyses performed after 54 and 90 months of follow-up in 397 patients; these demonstrated improved recurrence-free survival (RFS) and overall survival (OS) with adjuvant imatinib 400 mg/day given for 3 years versus 1 year. 

After a median 119 months of follow-up, the current 5- and 10-year rates of RFS for the intention-to-treat population were 71.4% and 52.5%, respectively, with 3 years of treatment versus 53.0% and 41.8% after 1 year of treatment, with a significant hazard ratio (HR) for recurrence or death of 0.66. 

And the 5- and 10-year OS rates for the 3-year treatment group were 92.0% and 79.0% versus 85.5% and 65.3% for the 1-year group, with a significant HR for death of 0.55. 

The 10-year rate of OS continued to be significantly better with the 3-year than 1-year regimen in an efficacy population that excluded patients who had intra-abdominal metastases resected or who did not have GIST in the central pathology review, at 81.6% versus 66.8% and a HR of 0.50. 

“Approximately 50% of deaths may be avoided during the first 10 years of follow-up after surgery with longer adjuvant imatinib treatment”, the investigators summarise.

The extended follow-up found “[n]o new safety signals”. A similar number of cardiac events occurred in the 3- and 1-year treatment arms (5.1 vs 6.2%). And a second non-GIST cancer diagnosis was reported for 17.2% of the 3-year group and 12.1% of the 1-year group, most commonly prostate cancer and melanoma.

“It is unknown whether longer than 3 years of adjuvant imatinib administration confers benefits compared with 3 years of imatinib treatment”, the investigators observe.

“Two randomized clinical trials that compare either 5 years or 6 years of adjuvant imatinib to 3 years of imatinib treatment (NCT02413736 and NCT02260505, respectively) are accruing patients”, they say. 

References 

Joensuu H, Eriksson M, Sundby Hall K, et al. Three versus one year of adjuvant imatinib for high-risk gastrointestinal stromal tumor (GIST): Survival analysis of a randomized trial after 10 years of follow-up. J Clin Oncol 38: 2020 (suppl; abstr 11503).  

Joensuu H, Eriksson M, Sundby Hall K, et al. Survival outcomes associated with 3 years vs 1 year of adjuvant imatinib for patients with high-risk gastrointestinal stromal tumors. An analysis of a randomized clinical trial after 10-year follow-up. JAMA Oncol; Advance online publication 29 May 2020. doi:10.1001/jamaoncol.2020.2091