Optimal duration of adjuvant therapy for patients with resected gastrointestinal stromal tumors

Comparison of the long-term risk of recurrence and other clinical outcomes in GIST patients receiving imatinib as adjuvant therapy--a retrospective chart extract-based approach

PURPOSE

To compare characteristics of patients, the risk of recurrence, and mortality among adult patients with primary resectable gastrointestinal stromal tumor (GIST) receiving short-term (6-12 months) versus long-term (≥ 24 months) imatinib therapy.

METHODS

Detailed information on primary resectable KIT-positive GIST patients initiated on imatinib adjuvant therapy was retrospectively collected for short- and long-term imatinib patients from 318 US oncologists using an online data collection form. Patient characteristics were compared using Wilcoxon and Chi-square tests. Disease recurrence and mortality rates were compared using multivariate Cox proportional hazard models.

RESULTS

Among the 406 short-term and 406 long-term imatinib patients, the median follow-up was 916 and 970 days, respectively. While patients generally had similar demographic characteristics, the short-term group had a higher prevalence of cardiovascular and ischemic heart diseases and patients in the long-term group had a higher pre-surgery risk profile. This finding was consistent with the main reason reported by oncologists for prescribing adjuvant imatinib over longer duration, i.e., patient risk profile. Disease recurrence [5.9 versus 1.2 %, (p < .001)] and mortality rates [7.1 % versus 2.0 %, (p < .001)] were higher in short- versus long-term patients. The adjusted risk of recurrence was 5.30 times (p < .001) higher, and mortality risk was 4.02 times (p < .001) higher in short- versus long-term patients.

CONCLUSIONS

Patient risk profile is an important factor in oncologists' decisions to prescribe adjuvant imatinib. Despite the higher risk profile observed in long-term patients, the long-term use of imatinib was associated with a reduction in long-term risk of disease recurrence and mortality.

Length of adjuvant imatinib therapy in GIST: weighing benefits, side effects and costs

A recent large randomized clinical trial showed a survival advantage with 36 vs 12 months of adjuvant imatinib in patients with resected gastrointestinal stromal tumors (GISTs). However, there was a higher therapy discontinuation rate with the longer duration of treatment. Preferences of individual GIST patients and the imatinib risk/benefit ratio should always be sought before employing this agent in adjuvant setting for longer than 12 months. A shorter duration of therapy may be preferred in patients with a limited life expectancy, serious cardiovascular co-morbidities, diminished compliance or poor adherence to oral therapy. Further study of underlying economic, psychosocial, and physical barriers of longer vs shorter duration of adjuvant therapy in this patient population is probably warranted.

Approval summary: imatinib mesylate for one or three years in the adjuvant treatment of gastrointestinal stromal tumors

On January 31, 2012, the U.S. Food and Drug Administration granted regular approval of imatinib mesylate tablets (Gleevec®; Novartis Pharmaceuticals Corporation, East Hanover, NJ) for the adjuvant treatment of adult patients following complete gross resection of Kit(+) (CD117(+)) gastrointestinal stromal tumors (GISTs). The recommended dose of imatinib is 400 mg/day administered daily for 3 years. Three hundred ninety-seven patients were enrolled in a randomized adjuvant, multicenter, open label, phase III trial comparing 12 months with 36 months of imatinib treatment. Eligible patients had one of the following: tumor diameter >5 cm and mitotic count >5 per 50 high power fields (HPFs); tumor diameter >10 cm and any mitotic count; tumor of any size with mitotic count >10/50 HPFs; or tumor ruptured into the peritoneal cavity. The primary endpoint was the recurrence-free survival (RFS) interval. The median follow-up for patients without an RFS event was 42 months. There were 84 (42%) RFS events in the 12-month treatment arm and 50 (25%) RFS events in the 36-month treatment arm. Thirty-six months of imatinib treatment led to a significantly longer RFS interval than with 12 months of treatment. The median follow-up for overall survival (OS) evaluation in patients still living was 48 months. Thirty-six months of imatinib treatment led to a significantly longer OS time than with 12 months of imatinib treatment. The most common adverse reactions, as noted in previous imatinib studies, were diarrhea, fatigue, nausea, edema, decreased hemoglobin, rash, vomiting, and abdominal pain.