Real-World Outcomes of Patients Treated With Neoadjuvant Imatinib for Locally Advanced, Recurrent and Limited Metastatic Gastrointestinal Stromal Tumour in an Australian Cancer Training Network.

Abstract

Background: Imatinib for palliative and adjuvant treatment of gastrointestinal stromal tumours (GISTs) with common KIT mutations has been revolutionary. For patients with locally advanced, limited metastatic or recurrent disease, neoadjuvant imatinib may downstage the tumour, enabling surgery with curative intent; however, the optimal duration of neoadjuvant imatinib is unknown.

Methods: We conducted a retrospective review of patients with locally advanced, limited metastatic and recurrent GIST treated with neoadjuvant imatinib prior to consideration of surgical resection in the period 2012-2024 at three cancer centres in NSW, Australia. Baseline and outcome data were collected. The primary endpoint was the progression-free survival (PFS).

Results: A total of 30 patients were identified with 38 instances of primary locally advanced, recurrent or limited metastatic disease. The median per-patient duration of neoadjuvant imatinib was 7.8 months (range 2.9-14.9 months), and the median per-episode duration of neoadjuvant imatinib was 9.1 months (range 3.0-27.4 months). Maximum radiological response was achieved at 3.8 months for primary tumours and 6.7 months for recurrent tumours. Partial response occurred in 77% and progression in 0%. Of the 25 patients with available data, 96% were symptomatic, and 89% reported early symptomatic benefit from imatinib within 1 month. Complete surgical resection occurred in 58% of all episodes of neoadjuvant treatment. The estimated PFS rates at 2 and 5 years were 84% and 55% respectively. Overall survival rates were 84% at both 2 and 5 years.

Conclusions: Neoadjuvant imatinib provided effective symptomatic and radiological responses in patients with locally advanced, limited metastatic or recurrent GIST. A duration of 3-6 months treatment for primary tumours and 6-12 months for recurrent disease appears sufficient for most patients. Mutational profile analysis is of particular value for patients who do not have early symptomatic benefit, have poor radiological response or have recurrent disease.