(P 119) SURGICAL MANAGEMENT OF GASTROINTESTINAL STROMAL TUMOURS SARCOMATOSIS (GISTOSIS). A RETROSPECTIVE MULTI-INSTITUTIONAL STUDY

Objective: To describe characteristics and results of the surgical treatment of GIST sarcomatosis (GISTOSIS).

Methods: This an observational, retrospective, multi-institutional study of patients with GISTosis. We present preliminary results based in data collected from 10 specialised centres in Spain.

Results: The series comprises 48 patients of which 58,33% were woman. Median age was 57 years. Alt diagnosis, most of cases were symptomatic (75%) with an ECOG 0 in 65%, being the most frequent symptom / sign, anemia (23%). In 58,4% GISTosis was metachronic with a mean interval time between primary tumor and sarcomatosis of 34 months. Primary tumour was located in small bowel in 64% followed by stomach in 27%. The mean tumoral size was 15cm with a mean mitotic index of 14 mit/50HPF and a Ki67 mean of 17%. 76% of the cases were spindle cell, being c-KIT E-11 the most frequent mutation (71%).
Surgical treatment was associated with HIPEC in 19% of the cases. CC0 was achieved in 85% of the cases and It was followed by TKI in 47% of the cases. The most used TKI was imatinib (73%) followed by sunitinib (11%). The mean number of drugs used was 1,3 (range:1-5).
After a mean follow-up of 88 months, recurrence was observed in 33 cases (70%) for a mean disease-free survival of 48 months. 43,47% of the patients are alive without disease and 32% alive with disease, with a disease-related mortality of 24%. 5-year survival was 80%.

Conclusion: CC0 resection followed by mutation-tailored TKI in well selected patients can allow to obtain good long-term results.