Related Experiment Video
Updated: Jul 14, 2026
Robotic Duodenal Sleeve Resection for Gastrointestinal Stromal Tumor with Rare Exon 8 KIT Mutation Following Neoadjuvant Imatinib
Published on: April 3, 2026
Radiographic Versus Pathology-Integrated Response for Assessing Optimal Surgical Timing After Neoadjuvant Imatinib in
Tannaz Ranjbarian1,2, Michela Del Simone3, Dong-Jin Eastern Kang Sim1,2
1Department of Surgery, Division of Surgical Oncology, University of California San Diego, San Diego, CA.
Objective:
To compare radiographic and pathology-integrated metrics for defining near-maximal treatment effect after neoadjuvant imatinib in KIT exon 11-mutant gastrointestinal stromal tumor (GIST).
Summary Of Background Data:
Operative timing after neoadjuvant imatinib is usually guided by radiographic shrinkage, although dimensional response may incompletely reflect biological treatment effect.
Methods:
We retrospectively analyzed 131 patients with locally advanced KIT exon 11-mutant GIST treated with neoadjuvant imatinib followed by curative-intent resection at 2 tertiary sarcoma centers in the United States and Italy. Radiographic response was assessed across 2-month intervals using RECIST and percent tumor shrinkage. The primary timing analysis identified the earliest interval reaching 90% of peak median response within 3 to 22 months. The same framework was applied to a pathology-integrated response score (PIRS) derived from tumor shrinkage, viable tumor percentage, and necrosis.
Results:
Median age was 62 years, and 60.3% of patients were male. By RECIST, 45.8% achieved partial response and 48.9% had stable disease. Radiographic response reached a near-maximal interval at >4 to 6 months, whereas PIRS reached a near-maximal interval at >10 to 12 months. PIRS discriminated across duration groups better than RECIST ( P =0.027 vs. P =0.13). Forty patients (30.5%) with stable disease had major or near-complete PIRS. Overall survival differed across PIRS categories, whereas recurrence-free survival did not differ across PIRS or RECIST categories.
Conclusions:
Radiographic and pathology-integrated response identified different windows of near-maximal treatment effect, suggesting that size reduction alone may underestimate biological response. The later pathology-integrated response window was not accompanied by differences in recurrence-free survival.
Insights
Radiographic and pathology-integrated response metrics in gastrointestinal stromal tumor (GIST) treatment show different optimal timing. Pathology-integrated response may better reflect biologic effects than size reduction alone.
Area of Science:
- Oncology
- Medical Imaging
- Pathology
Background:
- Neoadjuvant imatinib is used for gastrointestinal stromal tumor (GIST) treatment.
- Operative timing is typically based on radiographic tumor shrinkage.
- Radiographic response may not fully represent the biologic treatment effect.
Purpose of the Study:
- To compare radiographic and pathology-integrated metrics for defining maximal treatment effect.
- To assess neoadjuvant imatinib efficacy in KIT exon 11-mutant GIST.
- To determine optimal timing for surgical intervention.
Main Methods:
- Retrospective analysis of 131 patients with locally advanced KIT exon 11-mutant GIST.
- Radiographic response assessed by RECIST and tumor shrinkage.
- Pathology-integrated response score (PIRS) derived from shrinkage, viable tumor, and necrosis.
Main Results:
- Radiographic response peaked earlier (4-6 months) than PIRS (10-12 months).
- PIRS better discriminated response duration than RECIST.
- 30.5% of patients with stable disease by RECIST showed major or near-complete PIRS.
Conclusions:
- Radiographic and pathology-integrated metrics identify different windows of maximal treatment effect.
- Tumor size reduction may underestimate biologic response in GIST.
- Later PIRS window did not correlate with recurrence-free survival differences.
