"As clinicians, we really need to ask who should receive adjuvant [imatinib], and we have several ways to risk-stratify patients, including tumor characteristics (size, location, mitotic index), mutational analyses, and a recently published nomogram for patient-specific survival,” said William D. Tap, MD, Section Chief of Sarcoma Oncology at Memorial Sloan-Kettering Cancer Center in New York.¹

Then, “the question really becomes, what defines risk?… I already see that some physicians are beginning to say if [patients] have a 20%, 30%, 40% increase in [risk of] recurrence or death during a certain time period, they would start [imatinib].” But all of the above factors should be considered.

Cytostatic vs Cytotoxic

“The other question is, once you start it, how long should you treat?” Dr. Tap continued. In the trial, whether imatinib was taken for 1 year or 3 years, there was a similar uptick in recurrences after drug discontinuation.

“What this suggests is that we are not curing patients with longer use of [imatinib]; rather, we are just prolonging recurrence-free survival,” he commented. “So the question with a cytostatic drug becomes, once you start [it], are you able to stop it?”

A phase II trial, PERSIST-5, is looking at 5 years of adjuvant imatinib, but results are not out until 2018. “So this is a question that we are going to be faced with for some time,” he said.

“Based on all this data, in my patient population when we start [imatinib], we are going to continue it for the near future, and that often means we talk to the patients about doing it for life,” Dr. Tap concluded. “Until there is other data to suggest that they could come off it, or we find combinations that can turn this from a cytostatic drug into a cytotoxic drug, they will remain on [imatinib].” ■

Reference

1. Gold JS, Gönen M, Gutiérrez A, et al: Development and validation of a prognostic nomogram for recurrence-free survival after complete surgical resection of localised primary gastrointestinal stromal tumour: A retrospective analysis. Lancet Oncol 10:1045-1052, 2009.