Abstract discussant Dr. Charles D. Blanke, chief of medical oncology at the University of British Columbia, Vancouver, said, "If you have a patient who has a high-risk GIST – at least as defined by the study – giving him or her 3 years of imatinib represents the new gold standard. For now, the overall survival benefit demonstrated with immediate postoperative imatinib means it is no longer acceptable to withhold treatment in the adjuvant setting hoping to ‘catch up’ when a patient has recurrent metastatic disease."
That said, the optimal duration of therapy remains unknown. "There are plenty of reasons to think giving imatinib for a longer period would be better, but that theory remains unproven," he said. "For now, if I were a patient with resected GIST and I had a compliant oncologist, I would request more. As a compliant oncologist, I personally will offer patients treatment to eternity, meaning indefinitely."
However, Dr. Blanke added, "I reserve the right to change my mind pending the longer-term overall survival results of SSGXVIII and the findings in PERSIST-5," a trial assessing 5 years of adjuvant imatinib. "But I don’t think GISTs are curable, even in the adjuvant setting, and I bet I won’t [change my mind]."
Oncologists must also decide for themselves which patients to treat, as the high-risk category used in the SSGXVIII trial included patients with possible recurrence risks ranging from 34% up to nearly 100%.
"But given the possibility that we need to treat for a very long time, coupled with the difficulty patients have taking long-duration drugs, I probably will recommend therapy for those with a 50% chance or greater of recurrence following surgery alone," he said. "I suspect many of you will choose a lower number."
Dr. Joensuu reported being a consultant to and receiving honoraria from Novartis. Novartis provided the drug and partly funded the trial. Dr. Kris reported being a consultant to GlaxoSmithKline, Merck, and Sanofi-Aventis. Dr. Blanke reported being a consultant to Novartis.