Gastrointestinal Stromal Tumours of the Rectum – Evaluating the National Registry Data with Respect to its Use in Clinical Practice

BACKGROUND: Gastrointestinal stromal tumours (GIST) are rare malignant mesenchymal tumours with an incidence of 1 in 100,000. They represent only 5% of gastrointestinal tumours. The GISTs are mainly located in the stomach (60-70%) and in the rectum in < 5% of cases. In the case of localized, resectable tumours, the treatment is surgical resection. Depending on the size and localization of the tumour in the rectum, either a local excision, rectal resection with anastomosis, or abdominoperitoneal amputation with permanent stoma can be performed. In contrast to carcinomas, the metastasis of GISTs into lymph nodes is rare; therefore, from an oncological point of view, lymphadenectomy in the form of mesorectal excision is not required. Neoadjuvant treatment using tyrosine-kinase inhibitors (TKI) is recommended for tumours larger than 5 cm and in case of tumours infiltrating surrounding organs or sphincters in order to achieve complete resectability, less mutilating and continent procedure. In GISTs with a positive resection line, re-resection can be attempted. Adjuvant TKI therapy can be considered in cases of CD117 positivity and after resections of GISTs with medium and high-risk malignant behaviour. The TKI treatment is also indicated in cases of unresectable and metastatic GISTs. METHODS: Data obtained from the GIST registry by the 1st January 2017, when 10 centres in the Czech Republic were contributing to the registry, were analysed. RESULTS: We analysed 1,095 patients out of which 45 (4.1%) had GIST localized in the rectum. The average age of the patients was 60 years. There were significantly more males (68.9%; p = 0.0007) and symptomatic patients (62.2%; p = 0.034). In total, 82% of the patients underwent surgery. Local excision was performed in 37.8%, resection of the rectum with anastomosis in 29.7%, and Miles operation in 29.7%. In the cohort, most tumours were 2-5 cm in size and almost half of the tumours presented a high risk of malignant behaviour. Systemic treatment was reported in 73% of patients. A complete remission was achieved in 80% of patients with GIST of the rectum. The median survival rate was 11.3 years and the 5-year survival rate is 90.6%. CONCLUSION: Despite the success of TKI treatment, the only potentially curative method of rectal GISTs is a surgical R0 resection. Given the relatively rare frequency of these tumours, proper diagnosis and treatment is demanding. Therefore, these patients should be preferably treated in specialised centres. This work was supported by grant MH CZ - RVO (FNBr, 65269705).  The authors declare they have no potential conflicts of interest concerning drugs, products, or services used in the study. The Editorial Board declares that the manuscript met the ICMJE recommendation for biomedical papers. Submitted: 19. 12. 2018 Accepted: 2. 2. 2019.