Role of imatinib in the management of early, operable, and advanced GI stromal tumors (GISTs)

Patient-derived xenograft models of gastrointestinal stromal tumors provide a ready-to-use platform for translational research

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal malignancy of the gastrointestinal tract. Most GISTs harbor mutations in oncogenes, such as KIT, and are treated with tyrosine kinase inhibitors (TKIs), such as imatinib. Most tumors develop secondary mutations, inducing drug resistance against the available TKIs, requiring novel therapies. We established a GIST patient-derived xenograft (PDX) platform of GIST that can be used for preclinical drug testing. Tumor tissue from consenting GIST patients was transplanted subcutaneously to NMRI nu/nu mice. Once tumor growth was observed, the tumor was re-transplanted to a next generation of mice. Tumors were characterized histopathologically and molecularly at every re-transplantation and compared with the original patient tumor. We transplanted 112 tumor samples from 99 GIST patients, resulting in 12 established and well-characterized GIST models with different mutations and TKI sensitivity. Three models harbor secondary KIT mutations. One model is characterized by a primary, imatinib-resistant PDGFRA exon 18 p.D842V mutation. Our established platform of well-characterized GIST PDX models, covering the most relevant driver mutations, serves as an excellent tool for preclinical drug testing and tumor biology studies.

Current treatment strategies and future perspectives for gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are mesenchymal tumors that originate from the gastrointestinal tract, mostly from the stomach. GISTs are derived from the myenteric interstitial cells of Cajal and are caused by several mutations in the c-kit and platelet-derived growth factor receptor genes. Clinically, GISTs are detected by endoscopic and imaging findings and are diagnosed by immunostaining. Surgery is the first line of treatment, and if the tumor is relatively small, minimally invasive surgery such as laparoscopy is performed. In recent years, neoadjuvant therapy has been administered to patients with GISTs that are suspected of having a large size or infiltration to other organs. Postoperative adjuvant imatinib is the standard therapy for high-risk GISTs. It is important to assess the risk of recurrence after GIST resection. However, the effect of tyrosine kinase inhibitor use will vary by the mutation of c-kit genes and the site of mutation. Furthermore, information regarding gene mutation is indispensable when considering the treatment policy for recurrent GISTs. This article reviews the clinicopathological characteristics of GISTs along with the minimally invasive and multidisciplinary treatment options available for these tumors. The future perspectives for diagnostic and treatment approaches for these tumors have also been discussed.

Surgical treatment of GIST--an institutional experience of a high-volume center

BACKGROUND

Discovery of the molecular pathogenesis of Gastrointestinal stromal tumors led to the development of targeted therapies, revolutionizing their treatment. However, surgery is still the mainstay of GIST therapy and the only chance for cure.

AIM

Here we present a single institutional consecutive case series of 159 GIST-patients.

METHODS AND PATIENTS

A total of 159 GIST-patients who underwent resection between 1994 and 2011 were reviewed for clinicopathohistological data, informations on surgical and medical therapy and further follow-up, outcome and survival data.

RESULTS

Laparoscopic (25.2%) and open (71.1%) GIST surgery achieved complete resection rates of 97.5% and 85.2%, whereas 44.4% of incomplete and 6.6% of complete resected patients died from GIST. Compared to open surgery laparoscopy significantly reduced duration of operation (183.4 vs. 130.6 min), length of hospitalization (16.1 vs. 8.3 d) and morbidity (23% vs. 7.5%). Mean survival time was 3.7 ± 2.7 years (R0: 5.1 a and R1: 2.6 a) and the mean overall survival was 4.5 ± 3.8 years.

CONCLUSION

Complete surgical resection is the primary goal and laparoscopy can be performed safely in a subset of GIST-patients with potential perioperative advantages. Although not proven by the present study the authors assume that multimodal GIST-treatment, as performed in reference-centers, is required for advanced or high risk disease. Our data suggest the potential for minimally invasive GIST resection to achieving comparable oncological outcomes as after open surgery while providing low morbidity rates.

Gastrointestinal stromal tumors: a review of case reports, diagnosis, treatment, and future directions

Gastrointestinal stromal tumor (GIST) is a nonepithelial, mesenchymal tumor first described by Mazur and Clark in 1983. Since then, its molecular biology has been studied in great detail. Special interest in the role of tyrosine kinase in its regulation has been the target by different drug research. Mutation in c-kit exons 9, 11, 13, 17 and PDGFRA mutation in exons 12, 14, 18 are responsible for activation of gene signaling system resulting in uncontrolled phosphorylation and tissue growth. However, 5 to 15% of GISTs does not harbor these mutations, which raises additional questions in another alternate signaling pathway mutation yet to be discovered. Diagnosis of GISTs relies heavily on KIT/CD117 immunohistochemical staining, which can detect most GISTs except for a few 3% to 5% that harbors PDGFRA mutation. Newer staining against PKC theta and DOG-1 genes showed promising results but are not readily available. Clinical manifestation of GISTs is broad and highly dependent on tumor size. Surgery still remains the first-line treatment for GISTs. The advancement of molecular biology has revolutionized the availability of newer drugs, Imatinib and Sunitinib. Together with its advancement is the occurrence of Imatinib/Sunitinib drug resistance. With this, newer monoclonal antibody drugs are being developed and are undergoing clinical trials to hopefully improve survival in patients with GISTs.