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Gastrointestinal stromal tumours: Real-world data from a Portuguese oncological center
Background
Gastrointestinal Stromal Tumours (GIST) are rare tumours that account for less than 3% of all gastrointestinal tumours. Originating from the myenteric interstitial cells of Cajal, GISTs are caused by mutations in the c-KIT and platelet-derived growth factor (PDGFR) receptor genes. c-KIT mutations of the exon 11 occur in 67% and of exon 9 in 10%. The most prominent diagnostic marker is the near universal overexpression of the receptor tyrosine kinase KIT (CD117). Most common anatomical sites are stomach (60%), small intestine (30%), colon and rectum. Extragastrointestinal Stromal Tumours (EGISTS) account for 10% of all GISTs and comprise stromal tumours arising outside the gut (retroperitoneum, mesentery, or omentum). Majority are asymptomatic and diagnosed by endoscopic, imaging and immunostaining methods. First-line treatment is surgery followed by postoperative adjuvant imatinib for high-risk tumours. In the last years, neoadjuvant therapy for large tumours is under investigation.
Methods
Retrospective descriptive study of patients diagnosed with GIST and EGIST from 2016 to 2021 in a tertiary oncological center. Clinicopathological, genetic, management and survival data were reviewed. Statistical analysis was performed using SPPSS statistical software (V.25).
Results
A total of 44 GISTs were diagnosed, 61%(n=27) arising from the stomach, 31%(n=15) from small intestine and 5% (n=2) as EGIST. 52% of patients were female (n=23) and 48%(n=21) male with a median age of 70 years (IQR:47-90) and median ECOG performance status of 1 (IQR: 0-3) at diagnosis. 66% (n=29) presented with stage I disease, 11% (n=5) stage II, 7% (n=3) stage III and 16% (n=7) with stage IV. Relapse risk was graded by Miettinen and Lasota score, 14% (n=6) with very low risk, 34% (n=15) with low risk, 9% (n=4) with moderate and 11% (n=5) with high risk of relapse. Analysis of classical prognostic factors revealed 95% (n=42) over 50 years-old, 6 %(n=3) with more than 5 mitosis/HPF; 16% (n=7) with tumour rupture and median lesion size of 40mm (±40). 2% (n=1) had KIT exon 9 mutation, 23% (n=10) exon 11, 2% (n=1) exon 13 and 2% (n=1) exon 17. Most common mutation was c.1656_1676del in 7% (n=3) patients. Regarding treatment 84% (n=34) underwent surgery and 52% (n=23) treated with tyrosine kinase inhibitor - 16% (n=7) in the neoadjuvant, 23% (n=10) adjuvant and 11% (n=5) palliative setting. Median overall survival of 43 (3-228) months.
Conclusions
The retrospective analysis illustrates the low incidence of gastrointestinal stromal tumours with 44 new diagnoses over a 5-years period. Majority of patients diagnosed with low grade early-stage disease with surgical approach as first-line treatment. Regarding systemic treatment, analysis of c-KIT and PDGFRA mutations helped adjusting TKI dosage. The real-world data gathered emphasizes the benefit of better understanding the molecular pathways involved in GIST pathogenesis and its clinical implication as new therapeutic targets.
Legal entity responsible for the study
The author.
Funding
Has not received any funding.
Disclosures
All authors have declared no conflicts of interest.
