Nuances of treatment of gastrointestinal stromal tumors with imatinib

Some more about things that struck my fancy at GI ASCO this past January. I heard Dr. Robert Maki, MD give a lecture entitled, "Gastrointestinal Stromal Tumor: Exploiting Molecular Mechanisms to Improve Patient Care." I have seen him lecture before, and continue to think that he is really an excellent speaker on the subject. (I am, of course, partial to Dr. Charles Blanke, MD, as well, since I trained at Oregon Health Sciences University, but that is neither here nor there.)

In any case, at the closing of his talk, Dr. Maki mentioned that he is beginning to come around to the thought that patients should be maintained on suppressive sunitinib or imatinib even at progression to prevent a disease flare. This is currently not my practice, though I have seen patients who progress through imatinib and sunitinib and when we place them on hospice, their disease really does "explode" off the tyrosine kinase inhibitor. We know now that adjuvant imatinib for one year is helpful for recurrence-free survival.

Also interesting from GI ASCO was an abstract by George Demitri, reporting the results of a sub-analysis of B2222, which analyzed imatinib trough level and response to therapy. The investigators found that plasma levels did correlate with outcome. But we do not currently check plasma levels on day 29, as they did in this study.

Furthermore, a study looking at 400 mg vs. 800 mg of imatinib was negative, and the authors conclude it is appropriate to escalate dose at the time of progression. In my practice, I will likely not start checking trough levels of imatinib, but I will be considering maintenance therapy at the time of progression. A clinical trial in this scenario would be nice, though I have not heard that one is ongoing or planned yet for this clinical question.