Registro multi-institRegistro multi-institucional de pacientes con tumores del estroma gastrointestinal (GIST) con diseminación peritoneal o sarcomatosis (GISTosis)ucional de pacientes con tumores del estroma gastrointestinal (GIST) con diseminación peritoneal o sarcomatosis (GISTosis)

Abstract

INTRODUCTION: GISTosis, or peritoneal dissemination of gastrointestinal stromal tumors (GIST), is a clinically relevant entity with a significant lack of data on its incidence, evolution, and specific treatment. OBJECTIVES: The primary objective is to describe the characteristics of patients with GISTosis in Spain and the treatments received. Secondary objectives include evaluating outcomes in terms of recurrence-free survival (RFS) and overall survival of GIST and GISTosis (OS-1 and OS-2, respectively), and identifying prognostic factors. PATIENTS AND METHODOLOGY: This is an observational, retrospective, multicenter study that includes patients with peritoneal GISTosis from 10 hospitals across Spain. RESULTS: The series included 49 patients, with a median age of 57 years, predominantly male (57.1%) and ECOG 0 (65.30%). Of these, 24.5% were diagnosed incidentally, with abdominal pain being the most frequent symptom (34.7%). Regarding the primary tumor (T1), it was mainly located in the jejunum-ileum (65.25%), with a median size of 13 cm, a median mitotic index (MI) of 7 mitoses/50 HPF, and a median Ki-67 of 15%. Spindle cell type was found in 74.4%, with the most frequent mutation in exon 11 of C-KIT (66.7%). According to the NIH classification, the majority were high risk (94.1%) and stage I of Cananzi (40.81%). The most common treatment was surgical (85.72%), specifically surgery + tyrosine kinase inhibitors (TKI) (58.3%), achieving R0 in 81.6%. Regarding GISTosis, 42.9% were synchronous, with metachronous appearing after a median of 47.5 months. Typically spindle cell type (66.7%), with a median MI of 5 mitoses/50 HPF and mutations in exon 11 of C-KIT (66.67%). A surgical scheme was employed in up to 75.52%, specifically the sandwich type (TKI + surgery + TKI) in 36.73%. HIPEC was received by 24.32%. According to CHOI criteria, most were in partial response to TKI (82.35%). The median PCI was 13.65, with a median of 8 nodules and a median size of the largest nodule of 7.5 cm. Distant metastases were present in 17.8%. CC-0 was achieved in 86.1%. The surgery lasted a median of 255 minutes, with a need for transfusion in 26.1% and a median hospital stay of 9 days. Major morbidity was 9.7% (Clavien-Dindo III and IV complications) and mortality was 3.2%. The recurrence rate was 30.6% and the mortality rate was 27.1%. The RFS at 1, 3, and 5 years was 85.4%, 81.2%, and 72.9%, respectively. OS-1 and OS-2 at 1, 3, and 5 years were 92.9%, 85.7%, and 69%, and 93.7%, 76.3%, and 59.6%, respectively. After univariate analysis, prognostic factors were identified for both RFS (Cananzi stage, cell type, time interval in metachronous GISTosis, and use of HIPEC) and OS-1 (sex, age, ECOG, mutational analysis of T1, T1 treatment scheme, T1 neoadjuvant therapy, GISTosis MI, and GISTosis treatment scheme) and OS-2 (age, sex, T1 location, T1 Ki-67, and number of GISTosis nodules). CONCLUSIONS: Peritoneal sarcomatosis by GIST or GISTosis is a very infrequent entity that usually originates in the small intestine. In carefully selected patients both medically (low surgical risk patients) and surgically (R0/CC-0 surgeries) who have a mutational profile highly sensitive to TKI, optimal cytoreduction can achieve favorable results in terms of RFS and OS. Further in-depth research on the surgical treatment of GISTosis is needed in a prospective international clinical trial, or a national one in its absence