[Gastrointestinal stromal tumors (GIST)]

Back to the start: Evaluation of prognostic markers in gastrointestinal stromal tumors

The aim of this study was to provide a standardized risk stratification model for gastrointestinal stromal tumors (GISTs) based on tumor localization, tumor size, involved lymph nodes and metastases, as well as mitotic activity and other morphological and molecular markers, in order to improve the risk evaluation scheme for recurrence, metastatic spread and survival for patients with GIST. A total of 201 cases of patients with GIST were investigated according to standardized morphological markers, including nuclear pleomorphism, tumor cell necrosis, mucosal infiltration, ulceration, skeinoid fibers and growth pattern. In addition, all cases were immunohistochemically analyzed using a tissue microarray platform for various markers of differentiation (CD34, CD44, CD117, desmin, discovered on GIST 1, platelet-derived growth factor receptor α, S-100 and smooth muscle actin) and proliferation (B-cell lymphoma 2, P16, P53, phosphohistone H3 and Ki-67). These findings were correlated by uni- and multivariable analyses with clinicopathological characteristics, including recurrence, metastasis and survival. The general clinicopathological parameters of this GIST specimen cohort were comparable to previous studies. While several parameters exhibited clear associations to each other and to the defined clinical endpoints, the multivariate analysis reduced the number of relevant prognostic variables to localization, margin status, growth pattern and hematoxylin and eosin-based mitosis/Ki-67-based proliferation of GISTs. With the exception of CD34, none of the applied markers of differentiation and proliferation were found to be independent prognostic markers in GIST and the classical risk factors of GIST remain important prognostic factors. Additionally, growth pattern may predict the risk of recurrence and metastasis in GIST patients. Additional independent molecular prognostic markers remain to be identified and validated.

[Gastrointestinal stromal tumors: diagnostics and therapy]

Gastrointestinal stromal tumors (GIST) are the most frequent mesenchymal tumors of the gastrointestinal tract. The standard therapy is complete surgical resection with safety margins of 1-2 cm. Intraoperative rupture of the tumor capsule must be avoided because this carries a very high risk of tumor spread. A lymph node dissection is not routinely indicated as lymph node metastases very rarely occur with GIST. Smaller GISTs can normally be removed laparoscopically according to the rules of tumor surgery. Depending on the size of the tumor, the mitosis index and the localization of the primary tumor, the risk of recurrence after potentially curative resection is considerable in many cases. Patients with intermediate and high risks according to Miettinen's classification should receive adjuvant treatment with the tyrosine kinase inhibitor imatinib. Exceptions are those patients whose tumors exhibit the mutation D842V in exon18 of the PDGFRA gene. According to current European Society for Medical Oncology (ESMO) guidelines this therapy should be continued for 3 years. This leads to a significant improvement in progression-free survival compared to a 1-year therapy, and more important to an improvement in overall survival.