The rare entity of gastrointestinal leiomyosarcomas: An Italian multicenter retrospective study in high‐volume referral centers.

Background: After a huge efficacy of imatinib in treating patients with gastrointestinal stromal tumors (GISTs) was proven, a maximum effort was made to make a differential diagnosis between GISTs and gastrointestinal leiomyosarcomas (GI‐LMS), showing the latter to be an extremely rare tumor entity. Limited data on GI‐LMS biology, clinical behavior and drug‐sensibility are available, and the clinical decision‐making in this subgroup of patients is usually challenging. Methods: We conducted a multicenter, retrospective observational study on patients with diagnosed GI‐LMS from 2004 to 2020 within six high‐volume referral centers in Italy. Results: Thirty‐three patients had diagnosis of KIT‐negative GI‐LMS confirmed by sarcoma‐expert pathologist. The most common site of origin was the intestine. Twenty‐two patients had localized disease and underwent surgery: with a median follow‐up of 72 months, median disease‐free survival was 42 months. Overall survival (OS)‐rate at 5 years was 73% and median OS was 193 months. Five out of 10 patients with local relapse received a salvage surgery, and 2/5 remained with no evidence of disease. Thirteen patients received neoadjuvant (6) or adjuvant (7) chemotherapy, and 2/13 patients remained free from relapse. The median OS for patients with metastatic LMS was 16.4 months. Conclusion: GI‐LMS is very rare and extremely aggressive subgroup of sarcomas with a high tendency to systemic spread. Localized GI‐LMS at diagnosis may be cured if treated with adequate surgery with or without (neo) adjuvant chemotherapy, while de‐novo metastatic disease appeared to have a poor prognosis. Clinical effort to understand GI‐LMS biology and clinical behavior and to develop active treatment strategy, especially for metastatic‐disease, is warranted. [ABSTRACT FROM AUTHOR]