Dasatinib might have activity in some subsets of patients with imatinib-resistant gastrointestinal stromal tumors (GISTs), investigators have reported.
The tyrosine kinase inhibitor had a 29% rate of 6-month progression-free survival (PFS) in a nonrandomized, 50-patient study.
That PFS rate was well above the 10% threshold that would have constituted evidence of inactive treatment, but it “fell just short of our goal” of 30% that would have been considered evidence of drug activity, wrote Scott M. Schuetze, MD, PhD, of the department of internal medicine, University of Michigan, Ann Arbor, and his coauthors. The report was published in JAMA Oncology.
It was also higher than the 16% 6-month PFS rate reported in a randomized trial of sunitinib, which was approved for imatinib-resistant GIST treatment in 2006. However, it was lower than the 38% 6-month PFS rate reported for regorafenib, which was approved in 2013 for that indication, the researchers noted.
Exploratory analyses did identify a few biomarker-driven subsets that might particularly benefit from dasatinib therapy. Notably, the 6-month PFS rate was 50% for patients with tumors expressing phosphorylated SRC.
While intriguing, the results of the exploratory analyses are hampered by the small number of patients enrolled in the trial; only 14 patients in the study had phosphorylated SRC.
“Further studies should explore whether activated SRC is a prognostic biomarker of more indolent disease, or is a predictive biomarker of response to tyrosine kinase therapy,” the researchers wrote.