Predictors of complete response following disease recurrence in gastrointestinal stromal tumor (GIST) patient: A retrospective patient chart review analysis.

Abstract

10545 Background: Adjuvant imatinib (IM) treatment reduces the risk of GIST recurrence and improves survival particularly when IM is used for a longer duration among moderate to high risk patients. However, among patients who recur, little is known about the factors impacting the probability of achieving complete treatment response (CR). This study identifies factors associated with the probability of achieving CR among patients who had a recurrence following cessation of initial adjuvant IM treatment for a KIT + GIST. Methods: An online tool was used to retrieve clinical data on 410 patients who were treated with adjuvant IM for ≥6 months for primary resectable KIT+GIST, discontinued, had a recurrence after discontinuation, and then restarted IM or initiated sunitinib. Tumor and treatment characteristics were collected at primary diagnosis and disease recurrence. Patient response status was assessed by physicians based on different measures (e.g., RECIST, Choi, other subjective measures). Predictors of CR were identified using logistic regression models. Results: Among the 410 (IM = 314, sunitinib = 96) patients treated for GIST recurrence, 22.4% achieved CR (25.2% of pts on IM and 13.5% of patients on sunitinib). On average, CR was achieved after 11 weeks of treatment and only 2% of patients had a subsequent disease progression/recurrence. RECIST criteria were most widely used for CR evaluation in 68% of patients followed by subjective measures (29%) and Choi criteria (17%), respectively. Patients with a unifocal tumor (Odds Ratio[OR]=2.61; p<.001 ), small tumor size (≤2cm) (OR=2.16; p=.023), lower mitotic rate ≤5/50 HPF (OR=1.87; p=.017) at recurrence, or tumor recurrence inside gastrointestinal system (OR=2.27; p=.036) were more likely to achieve CR. Conclusions: Among study patients, 22.4% achieved CR following disease recurrence. The main predictors of CR were tumor focality, size, location, and the mitotic rate at recurrence. This suggests that detecting recurrence at an early stage and managing disease with re-initiation of KIT inhibitor therapy may improve the probability of achieving CR following recurrence.