# The Role of Cytoreductive Surgery with Hyperthermic Intraperitoneal Chemotherapy (HIPEC) in Peritoneal GIST-Induced Sarcomatosis (GISTosis)

## TL;DR

Cytoreductive surgery with HIPEC may improve survival in peritoneal GISTosis, particularly for patients with lower disease burden.

## Contribution

This study evaluates the outcomes of CRS plus HIPEC in peritoneal GISTosis, identifying survival benefits based on disease extent and cytoreduction quality.

## Key findings

- Patients with PCI scores ≤10 had significantly longer overall and progression-free survival.
- Complete cytoreduction (CC scores 0–1) was associated with better overall and progression-free survival.
- Imatinib administration did not significantly affect survival outcomes.

## Abstract

Background: The introduction of tyrosine kinase inhibitors has revolutionised the treatment of gastrointestinal stromal tumours (GISTs), yet the role of cytoreductive surgery (CRS) plus hyperthermic intraperitoneal chemotherapy (HIPEC) in peritoneal GISTosis remains controversial. Methods: A retrospective analysis was conducted on patients with peritoneal GISTosis who underwent CRS plus HIPEC in an 18-year period. We analysed the clinicopathological characteristics and evaluated the perioperative and long-term outcomes based on the extent of disease (peritoneal cancer index, PCI), the resection (completeness of cytoreduction score) and the IM-administration. The survival factors were also analysed and the Kaplan–Meier estimator to model and estimate overall (OS) and progression-free survival (PFS). The median follow-up period was 72 months (range, 12–146). Results: A total of 25 patients (M:F = 15:10) with a median age of 57 years (range, 32–69) underwent CRS with HIPEC for peritoneal GIST metastases, detected either synchronously (n = 11) or metachronously (n = 14). The media PCI score was 9 (range, 4–20) and complete cytoreduction was achieved in 80%. Grade III complications were observed in two patients, whereas there was no postoperative mortality. Neoadjuvant imatinib-mesylate (IM) therapy was administered in 60% of patients who detected with metachronous metastases (n = 8/14), whereas adjuvant IM therapy was administered in 19 of 25 patients. Median OS was 62 months (95% CI = 22.8–101.2). Median OS and DFS for patients with PCI scores ≤ 10 were significantly longer compared to those with PCI scores > 10 (p = 0.009 and p = 0.024, respectively). Patients with CC scores of 0–1 had a significantly longer OS compared to those with CC scores of 2 (p = 0.005) and 3 (p = 0.002) and longer PFS compared to those with CC scores of 3 (p = 0.005). The need for imatinib did not significantly impact OS (p = 0.240) or PFS (p = 0.243). Conclusions: CRS combined with HIPEC shows promising results in peritoneal GISTosis, especially in patients with lower PCI and CC scores. Until larger studies validate its safety and efficacy, it should be primarily performed in expert hands in specialised peritoneal surface oncology centres.