Charles D. Blanke, MD, Chief of Medical Oncology at the University of British Columbia in Vancouver, critiqued the SSGXVIII study, noting its “goals were reasonable and the methodologies for primary and secondary objectives were sound. The conclusion regarding recurrence-free survival is valid, as is the conclusion regarding overall survival, with some limitations.”

He said that oncologists who typically initiate imatinib upon relapse, based on the lack of survival advantage otherwise, will need to rethink this strategy, he said.

Based on the positive findings, Dr. Blanke advised, “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.”

He acknowledged, however, that compliance over 3 years may be unrealistic. In the study, 32% of the 36-month arm discontinued treatment early, compared with 15% of the 12-month arm. 

Grade 3/4 toxicities were similar in frequency, but twice as many dropped out on the 36-month arm for an adverse event or “other reasons,” he noted. “Were low-grade side effects challenging to tolerate long term? Is it too difficult to take a pill for years with no disease evident? Such difficulties on the 3-year arm of SSGXVIII may bode poorly for therapy lasting even longer.”

The optimal duration of treatment remains unknown, though there are reasons to believe that giving imatinib even longer might be better, as disease tends to progress when patients go off drug, he said. “For now, if I were a patient with a 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.” ■

Financial Disclosure: Dr. Blanke served as a compensated advisor for Novartis.