Clinical outcome in gastrointestinal stromal tumor patients who interrupted imatinib after achieving stable disease or better response.

Background: Imatinib has been found to be effective in the treatment of patients with gastrointestinal stromal tumors (GIST). We sought to evaluate the clinical outcome of imatinib interruption in GIST patients who had achieved stable disease (SD) or showed better response to imatinib therapy.

Methods: From July 2001 to December 2004, we prospectively collected clinical data from 62 consecutive patients with advanced GIST, of whom 58 (93.5%) achieved SD or better response to imatinib therapy and were included in this study. Imatinib therapy was interrupted in 14 of the 58 patients (interruption group, INT), after a median time of 11.9 months. Progression-free survival (PFS) after imatinib interruption was calculated and imatinib-refractory PFS and overall survival (OS) were compared between the INT group and the 44 patients who continued imatinib treatment (continuation group, CONT).

Results: After a median follow-up of 17.9 months following imatinib interruption, nine patients (64%) had progressive disease (PD) with a median PFS from the date of imatinib interruption of 10.0 months. Median PFS dated from the time of imatinib initiation in the INT group was 21.8 months (95% CI, 17.3-26.3 months), but was not reached in the CONT group (P=0.029). Following imatinib reintroduction in the INT group, 88% of patients achieved disease control. There were no statistically significant differences in imatinib-refractory PFS (P=0.405) and OS (P=0.498) between the groups.

Conclusion: In GIST patients controlled with imatinib, treatment might be interrupted, at least temporarily, when clinically warranted.