Gastrointestinal stromal tumors: management of metastatic disease and emerging therapies

Metastatic SDH-Deficient GIST Diagnosed during Pregnancy: Approach to a Complex Case

Gastrointestinal stromal tumors (GISTs) account for 1% of GI neoplasms in adults, and epidemiological data suggest an even lower occurrence in pregnant women. The majority of GISTs are caused by KIT and PDGFRA mutations. This is not the case in women of childbearing age. Some GISTs do not have a KIT/PDGFRA mutation and are classified as wild-type (WT) GISTs. WT-GIST includes many molecular subtypes including SDH deficiencies. In this paper, we present the first case report of a metastatic SDH-deficient GIST in a 23-year-old pregnant patient and the challenges encountered given her concurrent pregnancy. Our patient underwent a surgical tumor resection of her gastric GIST as well as a lymphadenectomy a week after induction of labor at 37 + 1 weeks. She received imatinib, sunitinib as well as regorafenib afterward. These drugs were discontinued because of disease progression despite treatment or after side effects were reported. Hence, she is currently under treatment with ripretinib. Her last FDG-PET showed a stable disease. This case highlights the complexity of GI malignancy care during pregnancy, and the presentation and management particularities of metastatic WT-GISTs. This case also emphasizes the need for a multidisciplinary approach and better clinical guidelines for offering optimal management to women in this specific context.

Immunotherapy Strategies for Gastrointestinal Stromal Tumor

Gastrointestinal stromal tumors (GIST) are the most common mesenchymal soft tissue sarcoma of the gastrointestinal tract. The management of locally advanced or metastatic unresectable GIST involves detecting KIT, PDGFR, or other molecular alterations targeted by imatinib and other tyrosine kinase inhibitors. The role of immunotherapy in soft tissue sarcomas is growing fast due to multiple clinical and pre-clinical studies with no current standard of care. The potential therapies include cytokine-based therapy, immune checkpoint inhibitors, anti-KIT monoclonal antibodies, bi-specific monoclonal antibodies, and cell-based therapies. Here we provide a comprehensive review of the immunotherapeutic strategies for GIST.

Low Distribution of TIM-3+ Cytotoxic Tumor-Infiltrating Lymphocytes Predicts Poor Outcomes in Gastrointestinal Stromal Tumors

There are multiple tumor-infiltrating lymphocytes (TILs) and relevant immune checkpoints existing in gastrointestinal stromal tumor (GIST), which provides opportunities and rationales for developing effective immunotherapies. Recent studies have suggested that checkpoint TIM-3/Gal-9 plays a pivotal role on immune response in multiple tumors, similar to the PD-1/PD-L1, emerging as a potential therapeutic target. However, their functions in GIST are unrevealed. Hence, the expression of immune checkpoints TIM-3 and Gal-9, as well as the infiltration of CD8⁺ T cells and NK cells, is described in 299 cases of GIST specimens. The results showed that TIM-3 and Gal-9 are mainly expressed in TILs, rarely in tumor cells. Expression levels of TIM-3 and Gal-9 significantly differ in varying risks of GIST and exert opposite distribution trends. Indicated by prognosis analysis, high TIM-3 expression of TILs was associated with improved outcome, while low expression levels of TIM-3 in combination with low amounts of CD8⁺ and CD56⁺ TILs predict extremely poor survival. The integrated analysis of TIM-3⁺, CD8⁺, and CD56⁺ TILs as one biomarker is a reliable independent predictor of prognosis. In conclusion, low densities of TIM-3⁺ TILs are associated with poor survival, and integrated immune biomarkers lead to superior predictors of GIST prognosis.

Neoadjuvant tyrosine kinase inhibitors in rectal gastrointestinal stromal tumours: a provision for enhanced oncological and functional outcomes

Background

The role of tyrosine kinase inhibitors (TKI) in the neoadjuvant setting and the optimal duration of therapy remains poorly defined. As such, we aim to evaluate the impact of neoadjuvant TKI on oncological and functional outcomes in our cohort of patients with rectal GISTs.

Methods

A retrospective analysis of 36 consecutive patients who underwent treatment for rectal GIST at the National Cancer Centre Singapore from February 1996 to October 2017 was analysed. Surgical, recurrence and survival outcomes between the groups who underwent neoadjuvant therapy and those who underwent upfront surgery were compared.

Results

Patients who received neoadjuvant treatment had significantly larger tumours (median size 7.1 vs. 6.0 cm, p = 0.04) and lower mitotic count (> 10 per 50 HPF, 14 vs. 70%, p = 0.03) when compared with the non-neoadjuvant group. With TKI pre-treatment (median duration 8.8 months), majority of patients (82%) achieved at least partial response to the therapy coupled with a significant downsizing effect of up to 39% (median size of 7.1–3.6 cm), resulting in similar rates of sphincter-sparing surgery (75 vs. 76%, p = 0.94) when compared with the non-neoadjuvant group. In general, neoadjuvant group had lower rates of local recurrence (0 vs. 69%, p = 0.04) and higher overall survival (7.4 vs. 5.7 years, p = 0.03) as compared to the non-neoadjuvant group.

Conclusions

Neoadjuvant TKI has the benefit of downsizing unresectable rectal GIST to benefit from sphincter-sparing procedure and also confers protection against local recurrence and improves overall survival.

Surgical Management of Sarcoma Metastatic to Liver

Sarcomas are rare mesenchymal tumors with a propensity for hematogenous metastasis. Gastrointestinal stromal tumor (GIST) is the most common histologic subtype and the most common source of hepatic metastases. In the case of metastatic GIST, neoadjuvant imatinib can be used as a selection tool for the judicious application of surgery, where treatment-responsive patients who undergo resection to prevent the development of treatment-resistant clones have associated 10-year actuarial survival of 40%. Further advances for many of the non-GIST sarcoma subtypes will depend on the development of improved systemic therapies and evaluation of their activity in subtype or molecularly defined trials.

Gastrointestinal Stromal Tumors of the Small Intestine: Progress in Diagnosis and Treatment Research

In recent years, the diagnosis and treatment of gastrointestinal stromal tumors (GISTs) of the small intestine have been a hot topic due to their rarity and non-specific clinical manifestations. With the development of gene and imaging technology, surgery, and molecular targeted drugs, the diagnosis and treatment of GISTs have achieved great success. For a long time, radical resection was prioritized to treat GISTs of the small intestine. At present, preoperative tumor staging is a novel treatment for unresectable malignant tumors. In addition, karyokinesis exponent is the sole independent predictor of progression-free survival of GISTs. The DNA, miRNA, and protein of exosomes have also been found to be biomarkers with prognostic implications. The research on the treatment of GISTs has become a focus in the era of precision medicine, ushering in the use of standardized, normalized, and individualized treatment.

Succinate Dehydrogenase–Deficient Gastrointestinal Stromal Tumors

Succinate dehydrogenase (SDH)–deficient gastrointestinal stromal tumor (GIST) is a subset of wild-type GIST that constitutes approximately 10% of gastric GISTs. SDH-mutated GISTs lack mutations in the proto-oncogene receptor tyrosine kinase (also known as KIT, c-KIT, or CD117) or platelet-derived growth factor receptor α (PDGFR-α). These tumors have female predilection, affect children and young adults, and have a spectrum of behavior from indolent to progressive. These tumors have characteristic morphologic features including multinodular architecture, multiple tumors, lymphovascular involvement, and occasional lymph node metastasis. They can be seen in patients with Carney triad or Carney-Stratakis syndrome. Although a mutation in any one of the SDH subunits can be pathogenic, deficiency of a single subunit leads to loss of detectable SDH subunit B by immunohistochemistry, enabling a convenient, tissue-based screening method. The prognosis and the clinical course of these tumors is different from that of KIT- or PDGFR-α–mutated GISTs. Surgical management is considered the main line of treatment. SDH-mutated GISTs do not respond well to the common targeted therapy, with no objective tumor response to imatinib. The role of the pathologist in diagnosing these cases is imperative in management and subsequent follow-up.

Prognosis assessment in metastatic gastrointestinal stromal tumors treated with tyrosine kinase inhibitors based on CT-texture analysis

PURPOSE

Identification of prognostic CT-textural features in patients with gastrointestinal stromal tumors undergoing tyrosine kinase inhibitor (TKI) therapy.

METHODS AND MATERIALS

We identified 25 GIST patients (mean age, 70.58 ± 9.7 years; range, 41.25-84.08 years; 20 males, 5 females) with a total of 123 scans, each examined with a standardized CT protocol between 1/2014-7/2018. 92 texture features, based on pyradiomics library, were extracted and correlated to response categories; evaluated with help of modified Choi criteria. All patients underwent therapy with imatinib in the first line and different tyrosine kinase inhibitors after disease progression. KIT and PDGFR-mutations were registered in all patients as well as the number of previous treatment regimens, patient's age as well as gender and the presence of contrast enhancement (vitality) in tumor. The lesion with the largest diameter was chosen and contoured using the spherical VOI tool. Inter-rater testing was performed by a second experienced radiologist. Regression and AUC analysis was performed.

RESULTS

Ten variables could be confirmed to be significantly associated with disease progression. Of them, four textural parameters were significantly positively associated with disease progression and negatively with progression free survival (Glcm Id [grey-level co-occurrence matrix inverse difference], p = 0.012, HR 3.83; 95% CI 1.697-8.611, Glcm Idn [grey-level co-occurrence matrix inverse difference normalized], p = 0.045, HR 2.06, 95% CI 1.015-4.185, Glrlm [grey-level run length matrix] normalized, p = 0.005, HR 3.181; 95% CI 1.418-7.138 and Ngtdm [neighboring grey-tone difference matrix] coarseness, p < 0.001, HR 3.156, 95% CI 1.554-6.411). Single variables were shown to be significantly inferior to the combination of all variables. After 6 months, 90% of patients with 0-1 risk factors (group 1), 64.4% with 2-3 risk variables and 38.1% of patients presenting > 3 structural risk variables showed stable disease. Gclm Id, Gclm Idn and Glrlm non-uniformity were associated with the number of previous treatments, Glrlm non-uniformity also with tumor vitality (enhancement), whereas Gclm Idn and Ngtdm coarseness were associated with the number of tumor mutations.

CONCLUSION

Some of the CT-textural features correlate with disease progression and the progressive free survival as well as with the number of gene mutations and the number of treatment regimens the patients were exposed to as well as with the tumor enhancement. All these features reflect tumor homogeneity.

Preferential MGMT methylation could predispose a subset of KIT/PDGFRA-WT GISTs, including SDH-deficient ones, to respond to alkylating agents

BACKGROUND

Succinate dehydrogenase (SDH)-deficient gastrointestinal stromal tumors (GISTs) constitute a small KIT/PDGFRA-WT GIST subgroup featuring DNA methylation which, although pervasive, appears nevertheless not randomly distributed. Although often indolent, these tumors are mostly chemorefractory in aggressive cases. Promoter methylation-induced O⁶-methylguanine DNA methyltransferase (MGMT) inactivation improves the efficacy of alkylating agents in gliomas, colorectal cancer and diffuse large B cell lymphoma. MGMT methylation has been found in some GISTs, without determining SDH status. Thirty-six GISTs were enrolled in past sarcoma trials testing alkylating agents, with negative results. Nevertheless, a possible effect on MGMT-methylated GISTs could have escaped detection, since tested GISTs were neither selected by genotype nor investigated for SDH; MGMT was studied in two cases only, revealing baseline activity; these trials were performed prior to the adoption of Choi criteria, the most sensitive for detecting GIST responses to therapy. Under these circumstances, we investigated whether MGMT methylation is preferentially found in SDH-deficient cases (identified by SDHB immunohistochemistry) by analyzing 48 pathogenetically heterogeneous GISTs by methylation-specific PCR, as a premise for possible investigations on the use of alkylating drugs in these tumors.

RESULTS

Nine GISTs of our series were SDH-deficient, revealing significantly enriched in MGMT-methylated cases (6/9-67%-, vs. 6/39-15%- of SDH-proficient GISTs; p = 0.004). The pathogenetically heterogeneous KIT/PDGFRA-WT GISTs were also significantly MGMT-methylated (11/24-46%-, vs. 1/24-4%- of KIT/PDGFRA-mutant cases, p = 0.002).

CONCLUSIONS

A subset of KIT/PDGFRA-WT GISTs, including their largest pathogenetically characterized subgroup (i.e., SDH-deficient ones), is preferentially MGMT-methylated. This finding could foster a reappraisal of alkylating agents for treating malignant cases occurring among these overall chemorefractory tumors.

Current treatment strategies in pediatric gastrointestinal stromal cell tumor

Gastrointestinal stromal tumors (GIST) are exceedingly rare tumors in the pediatric population. As a result, many clinicians either may never see this diagnosis or will encounter it only a few times throughout their careers. Additionally, the more we discover about this disease, it becomes evident that it represents a distinct clinical entity from adult GIST. Many of the treatments and strategies used to combat the adult tumor are either ineffective or may be harmful to the pediatric population with this disease. The unique tumor biology found in pediatric GIST necessitates unique approaches and treatment strategies in order to achieve the best clinical outcome. This review aims to discuss the most recent data available on the different therapeutic modalities utilized in cases of Pediatric GIST.

Management of hemorrhage in gastrointestinal stromal tumors: a review

Gastrointestinal stromal tumors (GISTs) are relatively common mesenchymal tumors. They originate from the wall of hollow viscera and may be found in any part of the digestive tract. The prognosis of patients with stromal tumors depends on various risk factors, including size, location, presence of mitotic figures, and tumor rupture. Emergency surgery is often required for stromal tumors with hemorrhage. The current literature suggests that stromal tumor hemorrhage indicates poor prognosis. Although the optimal treatment options for hemorrhagic GISTs are based on surgical experience, there remains controversy with regard to optimum postoperative management as well as the classification of malignant potential. This article reviews the biological characteristics, diagnostic features, prognostic factors, treatment, and postoperative management of GISTs with hemorrhage.

Evaluation for therapeutic measures to small gastric stromal tumor: A retrospective study of 90 cases

Surgery and regular follow-up are two main measures for small gastric stromal tumors (sGST) less than 2cm in diameter, while there is no sound evidence to prove which treatment is more beneficial to sGST patients. In this study, we reviewed the clinical and pathological features of patients with sGST receiving surgery and discussed the value of surgical intervention. In all, 90 patients who were diagnosed as sGST(less than 2cm) and accepted surgical treatment were enrolled, correspondently, another 104 patients with GSTs between 2-5cm and 74 patients with GSTs >5cm were collected as Control groups 1 and 2, respectively, and all of them received surgical treatment. Results showed that there were no significant difference among 3 groups in terms of gender, age, clinical features, tumor locations, and mutations of the exon 9 or 11 in C-kit gene, and immunohistochemical results of CD117, CD34, and DOG-1 proteins (P > 0.05). However, we observed growing percentage of medium-/high-risk GSTs and nucleus mitotic counts >5/50 HPF in Control groups (P < 0.05). Patients with sGST were more suitable for minimally invasive procedures than the other 2 groups, with shorter hospital stay (P < 0.05). During the follow-up period (medium 45.4 months), the recurrence rate was also associated with tumor size, which surged from 1.11% in sGST group to 7.69% and 17.56% in Control groups 1 and 2, respectively. In all, we concluded that patients with sGST experienced low proportions of medium-/high-risk tumors; however, they still suffered from potential risk of tumor progression. Due to satisfied surgical outcome, surgical treatment could be suggested for sGST.

Percutaneous microwave ablation liver partition and portal vein embolization for planned hepatectomy due to large gastrointestinal stromal tumor metastases: A case report

RATIONALE

The liver is the most frequent site of relapse of gastrointestinal stromal tumors (GISTs). Surgery is always considered to be unsuitable because of the multiple metastases.

PATIENT CONCERNS

In this report, we describe a case of large, multiple GIST liver metastases that were treated with percutaneous microwave ablation liver partition and portal vein embolization for planned hepatectomy (PALPP). A 44-year-old woman had undergone pancreaticoduodenectomy 4 years previously because of the diagnosis of a large duodenal GIST. Large, multiple liver metastases were observed 2 years later.

DIAGNOSES

GIST liver metastasis was diagnosed using percutaneous ultrasound-guided biopsy.

INTERVENTIONS

After 6 months of treatment with imatinib, the liver metastasis was stable. PALPP was performed because of insufficient future liver remnant (FLR) and right trisegmentectomy was successfully completed 10 days later.

OUTCOMES

The patient has had no signs of local or systemic disease during 17 months of postsurgical follow-up.

LESSONS

PALPP provides a new methodology for treatment of GIST liver metastasis in patients with insufficient FLR, and may have benefit in prolonging a durable remission.

Management of Gastrointestinal Stromal Tumors

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasm of the gastrointestinal tract. The stomach is the most common site of origin. Management of GISTs changed after the introduction of molecularly targeted therapies. Although the only potentially curative treatment of resectable primary GISTs is surgery, recurrence is common. Patients with primary GISTs at intermediate or high risk of recurrence should receive imatinib postoperatively. Imatinib is also first-line therapy for advanced disease. Cytoreductive surgery might be considered in advanced GIST for patients with stable/responding disease or limited focal progression on tyrosine kinase inhibitor therapy. GIST requires multidisciplinary management.

Comparison of Gene Expression Profile Between Tumor Tissue and Adjacent Non-tumor Tissue in Patients with Gastric Gastrointestinal Stromal Tumor (GIST)

Gastrointestinal stromal tumors (GISTs) are defined as spindle cell and/or epithelioid tumors originated from interstitial Cajal cells or precursors in the digestive tract. This study was conducted to identify genes differing in expression between the gastric tumors and the adjacent non-cancerous mucosas in patients with primary gastric GIST. The gene expression profile was determined by using oligonucleotide-based DNA microarrays and further validated by quantitative real-time PCR. The Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis was performed to predict signaling pathways involved in gastric GIST. Our data showed that the expression levels of 957 genes (RAB39B, member RAS oncogene family; VCAN, versican; etc.) were higher and that of 526 genes (CXCL14, chemokine C-X-C motif ligand 14; MTUS1, microtubule-associated tumor suppressor 1; etc.) were lower in the gastric tumor tissues as compared with normal gastric tissues. Results from KEGG pathway analysis revealed that the differentially expressed genes were enriched into 16 signaling transduction pathways, including Hedeghog and Wnt signaling pathways. Our study may provide basis for identification of novel biomarkers associated with primary gastric GIST pathogenesis and for exploration of underlying mechanisms involved in this gastric sarcoma.

The Role of Surgery in Metastatic Gastrointestinal Stromal Tumors

OPINION STATEMENT

Gastrointestinal stromal tumors (GISTs) are the most common sarcomas and mesenchymal neoplasms of the gastrointestinal tract. Macroscopically complete (R0/R1) resection is the standard treatment for localized resectable GIST with adjuvant imatinib therapy recommended for patients with intermediate or high-risk disease. In patients with advanced unresectable or metastatic GIST, imatinib has significantly improved outcomes. However, while most patients achieve partial response (PR) or stable disease (SD) on imatinib (with maximal response typically seen by 6 months on treatment), approximately half will develop secondary resistance by 2 years. Available data suggest that cytoreductive surgery may be considered in patients with metastatic GIST who respond to imatinib, particularly if a R0/R1 resection is achieved. The benefit of surgery in patients with focal tumor progression on imatinib is unclear, but may be considered. Patients with multifocal progression undergoing surgery generally have poor outcomes. Thus, surgery should be considered in patients with metastatic GIST whose disease responds to imatinib with a goal of performing R0/R1 resection. Optimal timing of surgery is unclear but should be considered between 6 months and 2 years after starting imatinib. Although surgery in patients with metastatic GIST treated with sunitinib is feasible, incomplete resections are common, complication rates are high, and survival benefit is unclear. Therefore, a careful multidisciplinary consultation is required to determine optimal treatment options on a case-by-case basis. Finally, patients with metastatic GIST should resume tyrosine kinase inhibitor treatment postoperatively.

Syndromic gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of gastrointestinal tract. They feature heterogeneous triggering mechanisms, implying relevant clinical differences. The vast majority of GISTs are sporadic tumors. Rarely, however, GIST-prone syndromes occur, mostly depending on heritable GIST predisposing molecular defects involving the entire organism. These conditions need to be properly identified in order to plan appropriate diagnostic, prognostic and therapeutic procedures. Clinically, GIST-prone syndromes must be thought of whenever GISTs are multiple and/or associated with accompanying signs peculiar to the background tumorigenic trigger, either in single individuals or in kindreds. Moreover, syndromic GISTs, individually considered, tend to show distinctive features depending on the underlying condition. When applicable, genotyping is usually confirmatory. In GIST-prone conditions, the prognostic features of each GIST, defined according to the criteria routinely applied to sporadic GISTs, combine with the characters proper to the background syndromes, defining peculiar clinical settings which challenge physicians to undertake complex decisions. The latter concern preventive therapy and single tumor therapy, implying possible surgical and molecularly targeted options. In the absence of specific comprehensive guidelines, this review will highlight the traits characteristic of GIST-predisposing syndromes, with particular emphasis on diagnostic, prognostic and therapeutic implications, which can help the clinical management of these rare diseases.

Regorafenib: A Review of Its Use in Patients with Advanced Gastrointestinal Stromal Tumours

Regorafenib (Stivarga(®)) is an orally administered small molecule inhibitor of multiple protein kinases, including kinases involved in oncogenesis and tumour angiogenesis. It was initially approved for use in patients with previously treated metastatic colorectal cancer. Based on the findings of the phase III GRID clinical trial, approval for regorafenib has been expanded to include the treatment of advanced gastrointestinal stromal tumours (GISTs) following the failure of imatinib and sunitinib. In the GRID trial, regorafenib significantly improved progression-free survival and was associated with a significantly higher disease control rate than placebo. No significant between-group difference was observed in overall survival (OS) in the trial; however, the high proportion of patients who crossed over from placebo to regorafenib likely impacted the OS analysis. Regorafenib has an acceptable tolerability profile, with most adverse events being manageable with dose modification and/or supportive measures. The most commonly reported drug-related adverse events among patients receiving regorafenib in the GRID trial were hand-foot skin reaction, hypertension, diarrhoea and fatigue. In conclusion, regorafenib presents a valuable new tool in the treatment of patients with advanced GISTs following the failure of imatinib and sunitinib.

The immune system and gastrointestinal stromal tumor: a wealth of opportunities

PURPOSE OF REVIEW

This article reviews the current literature on tumor-infiltrating immune cells in gastrointestinal stromal tumor (GIST), and the current status and prospects of effective immunotherapeutic strategies.

RECENT FINDINGS

Tumor-infiltrating immune cells populate the microenvironment of GISTs; the most numerous are tumor-associated macrophages (TAMs) and CD3 T cells. TAMs have not been shown to have a relationship with the biological behavior of GISTs; however, the number of CD3 T cells correlates with better outcomes. The prognostic significance of tumor-infiltrating neutrophils, natural killer cells, CD4 T cells, CD8 T cells, and Treg cells remains unknown.Imatinib mesylate achieves a clinical response in 80% of patients with GIST. Its antitumor mechanism is partially immune mediated. The combination of imatinib and interferon-α has been shown to be effective against GIST - it eradicates tumor cells including those that are drug resistant. Preclinical trials including cytotoxic T lymphocyte-associated antigen 4 blockade, anti-KIT antibody, and the generation of designer T cells have shown promising therapeutic effect in animal models of GIST.

SUMMARY

GIST contains many tumor-infiltrating immune cells and should be susceptible to immunotherapy; early clinical and preclinical trials have shown promising results that should lead to new investigations and effective forms of direct and synergistic therapies.

Metastatic Gastrointestinal Stromal Tumor to the Skull

BACKGROUND

Gastrointestinal stromal tumors (GISTs) arising from the interstitial cells of Cajal along the gastrointestinal tract rarely metastasize to the central nervous system (CNS) but require aggressive multimodal therapies when they do. We present a case of recurrent GIST metastasis to the skull and review the literature on management, including the role of molecular profiling in determining adjuvant treatment.

CASE

A 64-year-old woman presented with an enlarging palpable mass over her right eye. Magnetic resonance imaging revealed an enhancing T1-hypointense, T2-hyperintense right frontal calvarial lesion with lytic features on computed tomography. Pathology confirmed metastatic GIST to the skull with dural involvement. Molecular profiling revealed a mutation in exon 11 of KIT in her primary tumor, while the skull metastasis harbored an additional mutation in exon 17 associated with acquired drug resistance.

CONCLUSION

We review the epidemiology of GIST metastases and discuss potential reasons for its rare presentation to the CNS. Additionally, we highlight the diagnostic and prognostic value of molecular profiling for metastatic GIST, as well as its influence in arbitrating targeted molecular inhibitor therapy. Evolving molecular signatures, associated with treatment resistance, may play a pivotal role in future integration with multimodality treatment strategies for CNS GIST.

Feasibility and Timing of Cytoreduction Surgery in Advanced (Metastatic or Recurrent) Gastrointestinal Stromal Tumors During the Era of Imatinib

The prognosis of advanced gastrointestinal stromal tumors (GISTs) was dramatically improved in the era of imatinib. Cytoreduction surgery was advocated as an additional treatment for advanced GISTs, especially when patients having poor response to imatinib or developing resistance to it. However, the efficacy and benefit of cytoreduction were still controversial. Likewise, the sequence between cytoreduction surgery and imatinib still need evaluation. In this study, we tried to assess the feasibility and efficiency of cytoreduction in advanced GISTs. Furthermore, we analyzed the impact of timing of the cytoreduction surgery on the prognosis of advanced GISTs. We conducted a prospective collecting retrospective review of patients with advanced GISTs (metastatic, unresectable, and recurrent GISTs) treated in Chang Gung memorial hospital (CGMH) since 2001 to 2013. We analyzed the impact of cytoreduction surgery to response to imatinib, progression-free survival (PFS), and overall survival (OS) in patients with advanced GISTs. Moreover, by the timing of cytoreduction to imatinib, we divided the surgical patients who had surgery before imatinib use into early group and those who had surgery after imatinib into late. We compared the clinical response to imatinib, PFS and OS between early and late cytoreduction surgical groups. Totally, 182 patients were enrolled into this study. Seventy-six patients underwent cytoreduction surgery. The demographic characteristics and tumor presentation were similar between surgical and non-surgical groups. The surgical group showed better complete response rate (P <  .001) and partial response rate (P = 0.008) than non-surgical group. The 1-year, 3-year, and 5-year PFS were significantly superior in surgical group (P = 0.003). The 1-year, 3-year, and 5-year OS were superior in surgical group, but without statistical significance (P = 0.088). Dividing by cytoreduction surgical timing, the demographic characteristics and tumor presentation were comparable in early and late groups. The late cytoreduction group presented higher R0 resection rate (59.1% vs 31.5%, P = 0.025). However, the PFS and OS were comparable in both groups.Combining imatinib with cytoreduction increased the response rate to imatinib and prolonged PFS in patients with advanced GISTs. Moreover, early and late cytoreduction surgery was comparable in prognosis, although late cytoreduction revealed higher complete resection rate.

Survivorship

Significant therapeutic advances for soft tissue sarcomas allow increasing numbers of patients--adult and pediatric--to achieve long term survival. However, the harsh cytotoxic therapies are responsible for adverse physical and psychosocial effects that require long-term follow-up care, specific to survivorship issues. In the adult and pediatric patient population, guidelines for care developed by experts in comprehensive survivorship clinics are evolving to assist the practitioner while on-line supports bring information directly to the survivors.

Succinate dehydrogenase deficient gastrointestinal stromal tumors (GISTs) - a review

Loss of function of the succinate dehydrogenase complex characterizes a rare group of human tumors including some gastrointestinal stromal tumors, paragangliomas, renal carcinomas, and pituitary adenomas, and these can all be characterized as SDH-deficient tumors. Approximately 7.5% of gastric gastrointestinal stromal tumors are SDH-deficient and not driven by KIT/PDGFRA mutations, as are most other GISTs. The occurrence of SDH-deficient GISTs is restricted to stomach, and they typically occur in children and young adults representing a spectrum of clinical behavior from indolent to progressive. Slow progression is a common feature even after metastatic spread has taken place, and many patients live years with metastases. SDH-deficient GISTs have characteristic morphologic features including multinodular gastric wall involvement, often multiple separate tumors, common lymphovascular invasion, and occasional lymph node metastases. Diagnostic is the loss of succinate dehydrogenase subunit B (SDHB) from the tumor cells and this can be practically assessed by immunohistochemistry. SDHA is lost in cases associated with SDHA mutations. Approximately half of the patients have SDH subunit gene mutations, often germline and most commonly A (30%), and B, C or D (together 20%), with both alleles inactivated in the tumor cells according to the classic tumor suppressor gene model. Half of the cases are not associated with SDH-mutations and epigenetic silencing of the SDH complex is the possible pathogenesis. Extensive genomic methylation has been observed in these tumors, which is in contrast with other GISTs. SDH-loss causes succinate accumulation and activation of pseudohypoxia signaling via overexpression of HIF-proteins. Activation of insulin-like growth factor 1-signaling is also typical of these tumors. SDH-deficient GISTs are a unique group of GISTs with an energy metabolism defect as the key oncogenic mechanism. This article is part of a Directed Issue entitled: Rare Cancers.

Review article: the biology, diagnosis and management of gastrointestinal stromal tumours

BACKGROUND

Gastrointestinal stromal tumours (GIST) are the most common mesenchymal tumours of the gastrointestinal tract with an increasing incidence.

AIMS

To review the biology, diagnosis and treatment of gastrointestinal stromal tumours.

METHODS

A PubMed search using the phrases 'Gastrointestinal stromal tumor', 'imatinib', 'c-kit'.

RESULTS

The diagnosis of GIST is established by histology supplemented by the immunohistochemical marker CD117, which is positive in 95% of cases. The most common site of the tumour is the stomach. Most GIST are benign with 20-30% malignant. Five-year survival for malignant GIST ranges between 35% and 65% and depends primarily on tumour size, mitotic index and location. The malignant behaviour of GIST is best assessed by invasion of adjacent structures and distant metastases. The gold standard for treatment is surgical resection. Imatinib, a tyrosine kinase inhibitor, is the primary therapy for unresectable, recurrent or metastatic disease.

CONCLUSIONS

Gastrointestinal stromal tumours are rare tumours of the gastrointestinal tract and they vary in presentation. When surgical resection is not achievable, imatinib is the treatment of choice.

Evaluating new therapies in gastrointestinal stromal tumor using in vivo molecular optical imaging

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors in the US. The majority (~85%) of GISTs possess gain-of-function mutations in KIT or PDGFRA, causing constitutive activation of the kinase receptor. GIST management has been transformed by the identification of tumor driver mutations leading to unprecedented disease control of advanced GIST with the introduction of imatinib mesylate (IM). Despite IM's efficacy, most patients experience primary and/or secondary resistance within 2 y of treatment. Additional therapies and methods to optimize screening of novel approaches in preclinical studies are warranted. Clinically, treatment efficacy is typically assessed using Response Evaluation Criteria In Solid Tumors (RECIST) guidelines or Choi criteria. Both require a period of time on therapy before changes indicative of response can be observed. In addition, neither informs directly about cell death. We evaluated the use of molecular imaging technology in an animal model using near-infrared (NIR) imaging probes together with three-dimensional fluorescence molecular tomography (FMT) for assessing therapeutic response and ultimately optimizing our understanding of the biologic effects of these agents. We determined the potential of NIR probes (PSVue(TM) 794 and cell-penetrating KcapQ647) for detecting distinct markers of apoptosis and compare this to tumor size measured by MRI in response to IM treatment in GIST-T1 xenografts. Our studies revealed statistically significant increases in apoptosis due to IM treatment using both probes as early as 24 h post IM treatment which was confirmed by IHC. Molecular imaging will allow for faster and more effective screening of novel therapies in preclinical GIST models.