Outcome of patients with advanced gastro-intestinal stromal tumours crossing over to a daily imatinib dose of 800 mg after progression on 400 mg

[Systemic therapy of soft tissue sarcomas]

The gold standard for the treatment of primary, resectable, high-grade soft tissue sarcomas is complete surgical removal followed by radiotherapy. In cases where preservation of function is not possible, preoperative treatment options should be considered. Systemic therapy is the treatment of choice for metastatic soft tissue sarcomas. The most active single agents include the anthracyclines doxorubicin and epirubicin, as well as ifosfamide. While combination chemotherapy yields higher response rates, this is at the cost of increased toxicity with no evidence of prolonged overall survival. Current treatment strategies focus on the development of specific treatments for well defined soft tissue sarcoma subtypes. The first and highly successful targeted therapy was seen with the introduction of imatinib in the treatment of gastrointestinal stromal tumors.

Clinical practice guideline for accurate diagnosis and effective treatment of gastrointestinal stromal tumor in Korea

Despite the rarity in incidence and prevalence, gastrointestinal stromal tumor (GIST) has emerged as a distinct pathogenetic entity. And the clinical management of GIST has been evolving very rapidly due to the recent recognition of its oncogenic signal transduction pathway and the introduction of new molecular-targeted therapy. Successful management of GIST requires a multidisciplinary approach firmly based on accurate histopathologic diagnosis. However, there was no standardized guideline for the management of Korean GIST patients. In 2007, the Korean GIST study group (KGSG) published the first guideline for optimal diagnosis and treatment of GIST in Korea. As the second version of the guideline, we herein have updated recent clinical recommendations and reflected changes in diagnosis, surgical and medical treatments for more optimal clinical practice for GIST in Korea. We hope the guideline can be of help in enhancing the quality of diagnosis by members of the Korean associate of physicians involving in GIST patients's care and subsequently in achieving optimal efficacy of treatment.

The GIST paradigm: lessons for other kinase-driven cancers

Gastrointestinal stromal tumour (GIST) is the most common sarcoma of the intestinal tract, known to be notoriously refractory to conventional chemotherapy or radiation. It is an ideal solid tumour model to apply our understanding from aberrant signal transduction to drug development, since nearly all tumours have a mutation in the KIT or, less often, the PDGFRA or BRAF genes. The constitutively activated KIT and PDGFRA oncoproteins serve as crucial diagnostic and therapeutic targets. The discovery of oncogenic KIT activation as a central mechanism of GIST pathogenesis suggested that inhibiting or blocking KIT signalling might be the milestone in the targeted therapy of GISTs. Indeed, imatinib mesylate inhibits KIT kinase activity and represents the front-line drug for the treatment of unresectable and advanced GISTs, achieving a partial response or stable disease in about 80% of patients with metastatic GIST. KIT mutation status has a significant impact on treatment response, emerging in recent years as a leading paradigm for genotype-driven targeted therapy. In this review, parallels with other models in oncology that share their addiction to a particular mutationally activated kinase are contrasted. A better understanding of oncogene addiction as a common theme across tumours of diverse histologies underlies the clinical success of targeting such kinases with several selective kinase inhibitors. Also remarkable is the similarity displayed in the mechanisms of drug failure after a successful but temporary clinical response to kinase inhibition. Reactivation of the same oncogenic kinase, often by acquisition of second site mutations, is another emerging paradigm of secondary resistance in these tumour models. The complexity of polyclonal resistance in imatinib-resistant patients argues that single next-generation kinase inhibitors will not be beneficial in all mutant clones. Other broad therapeutic strategies could include combination of kinase inhibitors with targeting KIT downstream targets, such as PI3-K or MAPK/MEK inhibitors.

Gastrointestinal stromal tumors: current management

Herein, we review the current management of localized and advanced gastrointestinal stromal tumors (GISTs). Although surgery remains the standard of care for patients with localized GIST, adjuvant imatinib can delay recurrence in some of these patients. In patients with advanced or metastatic disease, the standard of care is imatinib and surgery of residual masses is an option. Preoperative imatinib is an emerging treatment option for patients who require cytoreductive therapy. Sunitinib is a standard second-line therapy.

Gastrointestinal stromal tumor (GIST) recurrence following surgery: review of the clinical utility of imatinib treatment

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor of the gastrointestinal tract. Surgery with complete removal of the tumor is the primary treatment for resectable GIST and the only chance of cure. However, recurrence after surgery is common. The 2 main prognostic factors are the mitotic activity and the size of the tumor. Tumor rupture is also a risk factor for postoperative recurrence, and extra care should be taken while manipulating this soft and friable tumor. Imatinib mesylate (IM, Gleevec(®), Novartis, Basel, Switzerland) is a tyrosine kinase inhibitor and was first studied in the palliative setting for metastatic GIST patients in the year 2000. It is now the cornerstone of metastatic GIST treatment. IM also plays an important role as an adjuvant treatment for resectable GIST and has been shown to increase the recurrence-free survival in phase III studies. However, some points remain to be clarified. Notably, the ideal duration of adjuvant IM after surgery is still unclear. It is also difficult to determine the exact place of surgery in metastatic or recurrent GIST patients in the IM era. A multidisciplinary approach is, therefore, mandatory to offer GIST patients the best treatment available.

Resection combined with imatinib therapy for liver metastases of gastrointestinal stromal tumors

PURPOSE

To evaluate the effectiveness of resecting liver metastases of gastrointestinal stromal tumors (GISTs), when performed in conjunction with imatinib treatment.

METHODS

Forty-one patients with pathologically diagnosed GIST and liver metastases were randomly assigned to an operation group (neoadjuvant therapy + resection + adjuvant therapy with imatinib) or a nonoperation group (imatinib alone). Patients were monitored for up to 36 months, and survival was analyzed.

RESULTS

We monitored 39 patients throughout the 36-month follow-up period, recording 1- and 3-year survival rates of 100% and 89.5% in the operation group and 85% and 60% in the nonoperation group, respectively. There was a significant difference in overall survival between the operation and nonoperation groups (P = 0.03). Furthermore, resection improved the survival of patients who responded poorly to 6 months of preoperative imatinib treatment, compared with that of their counterparts in the nonoperation group (P = 0.04).

CONCLUSION

These findings suggest that surgical intervention in combination with imatinib treatment is more effective than imatinib alone against GIST liver metastases, with minimal complications and side effects.

Imatinib induced severe skin reactions and neutropenia in a patient with gastrointestinal stromal tumor

BACKGROUND

Imatinib mesylate has been used for the treatment of unresectable or metastatic gastrointestinal stromal tumors (GIST). The current recommended dose of imatinib is 400 mg/day that is increased to 800 mg/day in cases with disease progression. However, imatinib can be associated with diverse adverse events, which has limited its use. We report a case of severe adverse skin reactions with neutropenic fever during imatinib treatment in a patient with GIST.

CASE PRESENTATION

A 71-year-old man was admitted with a one month history of epigastric pain and a palpable mass in the right upper quadrant. An abdominal CT scan revealed a 20 x 19 cm intraabdominal mass with tumor invasion into the peritoneum. Needle biopsy was performed and the results showed spindle shaped tumor cells that were positive for c-KIT. The patient was diagnosed with unresectable GIST. Imatinib 400 mg/day was started. The patient tolerated the first eight weeks of treatment. However, about three months later, the patient developed a grade 4 febrile neutropenia and a grade 3 exfoliative skin rash. The patient recovered from this serious adverse events after discontinuation of imatinib with supportive care. However, the skin lesions recurred whenever the patient received imatinib over 100 mg/day. Therefore, imatinib 100 mg/day was maintained. Despite the low dose imatinib, follow up CT showed a marked partial response without grade 3 or 4 toxicities.

CONCLUSION

The recommended dose of imatinib for the treatment of GIST is 400 mg/day but patients at risk for adverse drug reaction may benefit from lower doses. Individualized treatment is needed for such patients, and we may also try sunitinib as a alternative drug.

NCCN Task Force report: update on the management of patients with gastrointestinal stromal tumors

The standard of care for managing patients with gastrointestinal stromal tumors (GISTs) rapidly changed after the introduction of effective molecularly targeted therapies involving tyrosine kinase inhibitors (TKIs), such as imatinib mesylate and sunitinib malate. A better understanding of the molecular characteristics of GISTs have improved the diagnostic accuracy and led to the discovery of novel immunomarkers and new mechanisms of resistance to TKI therapy, which in turn have resulted in the development of novel treatment strategies. To address these issues, the NCCN organized a task force consisting of a multidisciplinary panel of experts in the fields of medical oncology, surgical oncology, molecular diagnostics, and pathology to discuss the recent advances, identify areas of future research, and recommend an optimal approach to care for patients with GIST at all stages of disease. The task force met for the first time in October 2003 and again in December 2006 and October 2009. This supplement describes the recent developments in the field of GIST as discussed at the October 2009 meeting.

Imatinib as the first and only treatment in Europe for adult patients at significant risk of relapse following gastrointestinal stromal tumor removal

Mutations of the KIT gene are the molecular hallmark of most gastrointestinal stromal tumors (GISTs). GIST has become a model for targeted treatment of solid tumors, imatinib becoming the standard first-line treatment of these tumors in the advanced/metastatic phase. Because of the efficacy of imatinib treatment in the advanced setting, its role following resection of a primary non-metastatic GIST was investigated. The recently published phase III, double-blind, placebo-controlled, multicenter ACOSOG Z9001 study showed that adjuvant therapy is safe, and significantly improves recurrence-free survival compared to placebo when given after resection. To what extent imatinib will improve overall survival has yet to be answered. What is clear is that high-risk GIST patients definitely need adjuvant therapy, and that 1 year of imatinib is not enough for the patients who do need it. The questions of optimal duration of imatinib treatment in the adjuvant setting, adequate selection of risk patients and effect of imatinib on overall survival are currently being studied.

The role of high-dose imatinib in the management of patients with gastrointestinal stromal tumor

After an era of few treatment options for patients with locally advanced or metastatic gastrointestinal stromal tumor (GIST), imatinib has emerged as the standard of care and first-line treatment for these patients. Although imatinib was initially approved at the doses of 400 and 600 mg daily, results from clinical studies established 400 mg daily as the standard initial dose for the majority of advanced GIST patients. Nevertheless, the use of high-dose imatinib (800 mg daily) has been shown to benefit patients with advanced or metastatic GIST that progresses on the standard-dose, and has been recommended in this setting by the major management guidelines in Europe and the United States. Results from the Meta-GIST meta-analysis showed that patients whose GIST harbors a KIT exon 9 mutation garner a longer progression-free survival time when treated initially with high-dose imatinib (800 mg daily) compared with those patients with KIT exon 11 or no mutations. Thus, the use of high-dose imatinib is recommended by the clinical practice guidelines in these 2 specific clinical situations. In addition, clinicians should weigh the clinical benefit of administering high-dose imatinib against the associated toxicities, as well as the proper management of dose-related side effects.

Targeted therapy for gastrointestinal stromal tumors: current status and future perspectives

Gastrointestinal stromal tumors (GISTs) present 80% of gastrointestinal tract mesenchymal tumors, with systemic chemotherapy and radiotherapy being unable to improve survival of patients with advanced disease. The identification of activating mutations in either KIT cell surface growth factor receptor or platelet-derived growth factor receptor alpha, which lead to ligand-independent signal transduction, paved the way for the development of novel agents that selectively inhibit key molecular events in disease pathogenesis. The development of imatinib mesylate in the treatment of metastatic GIST represents a therapeutic breakthrough in molecularly targeted strategies, which crucially improved patients' prognosis while its usefulness in adjuvant and neoadjuvant setting is under study. Sunitinib malate is available in the second-line setting, with ongoing studies evaluating its role in an earlier disease stage, while other targets are under intense investigation in order to enrich the therapeutical armamentarium for this disease. GIST phenotype seems to be an essential indicator of treatment response; thus, obtaining genotype information of each patient may be critical in order to tailor individualized treatment strategies and achieve maximal therapeutic results.

Optimal use of targeted agents for advanced gastrointestinal stromal tumours

Imatinib is the recommended 1st-line treatment for a KIT-positive unresectable and/or metastatic gastrointestinal stromal tumour (GIST). However, some patients experience intolerance to imatinib and most patients will eventually experience disease progression while on imatinib treatment. Sunitinib is approved for treatment of a GIST after disease progression on, or intolerance to, imatinib therapy. Progression may occur early or later on, in treatment and is determined by factors including initial GIST genotype and mutational status. GISTs with KIT exon 11 mutations appear to be sensitive to standard dose imatinib, and patients with GISTs exhibiting KIT exon 9 mutations whose disease has progressed on imatinib 400 mg/day have been shown to respond to imatinib 800 mg/day, albeit with a higher incidence of adverse events. Sunitinib has shown clinical benefit in all major GIST mutational subtypes, particularly in patients with wild-type or KIT exon 9 genotype and against GISTs with secondary KIT exon 13 or 14 mutations. The choice between higher-dose imatinib and sunitinib after progression on standard dose imatinib is unclear, and apart from the GIST primary resistance genotype and mutational status, individual patient factors such as tumour characteristics, drug pharmacokinetics, and other clinical factors may affect response to treatment. Individualisation of therapy may help to maximise clinical benefit of therapy in these patients.

Extraluminal laparoscopic wedge-resection of submucosal tumors on the posterior wall of the gastric fundus close to the esophagocardiac junction

PURPOSE

Laparoscopic resection of submucosal tumors in the gastric fundus, especially in the posterior wall near the esophagocardiac junction (ECJ), is difficult and time consuming and is and likely to cause esophageal stenosis and splenic injury. In this article, we report an extraluminal laparoscopic wedge-resection (ELWR) that minimizes these problems.

METHODS

Thirty-seven patients with submucosal tumors in the posterior wall of the gastric fundus received ELWR. The operation consisted of four steps: 1) localization of the tumor, 2) dissection of the omentum, 3) mobilization of the gastric fundus/upper pole of the spleen and exposure of the ECJ, and 4) resection of the gastric fundus with a linear endoscopic gastrointestinal anastomosis stapler.

RESULTS

None of the cases needed conversion to open surgery. Mean postoperative hospital stay was 5.5 +/- 1.0 days. The distance between the tumor and the incision margin ranged from 0.7 to 2.5 cm toward the ECJ. Pathologic examination revealed 7 cases of leiomyomas, 29 cases of stromal tumors (4 were low-grade malignant tumors), and 1 case of neurofibroma. There was no recurrence, metastasis, esophageal stenosis, or any other severe adverse event during the follow-up period (52 +/- 3.1 months).

CONCLUSIONS

ELWR is a safe, effective treatment for submucosal tumors in the posterior wall of the gastric fundus.

NCCN Task Force report: update on the management of patients with gastrointestinal stromal tumors

The standard of care for managing patients with gastrointestinal stromal tumors (GISTs) rapidly changed after the introduction of effective molecularly targeted therapies involving tyrosine kinase inhibitors (TKIs), such as imatinib mesylate and sunitinib malate. A better understanding of the molecular characteristics of GISTs have improved the diagnostic accuracy and led to the discovery of novel immunomarkers and new mechanisms of resistance to TKI therapy, which in turn have resulted in the development of novel treatment strategies. To address these issues, the NCCN organized a task force consisting of a multidisciplinary panel of experts in the fields of medical oncology, surgical oncology, molecular diagnostics, and pathology to discuss the recent advances, identify areas of future research, and recommend an optimal approach to care for patients with GIST at all stages of disease. The task force met for the first time in October 2003 and again in December 2006 and October 2009. This supplement describes the recent developments in the field of GIST as discussed at the October 2009 meeting.

Phase II study of oral masitinib mesilate in imatinib-naïve patients with locally advanced or metastatic gastro-intestinal stromal tumour (GIST)

BACKGROUND

Masitinib is a tyrosine kinase inhibitor with greater in vitro activity and selectivity for the wild-type c-Kit receptor and its juxtamembrane mutation than imatinib, without inhibiting kinases of known toxicities. This phase II study evaluated masitinib as a first-line treatment of advanced GIST.

PATIENTS AND METHODS

Imatinib-naïve patients with advanced GIST received oral masitinib at 7.5mg/kg/d. Efficacy end-points included response rate (RR) at 2 months, best response according to RECIST, metabolic response rate, disease control rate (DCR), progression-free survival (PFS) and overall survival rate (OS).

RESULTS

Thirty patients were enrolled with a median follow-up of 34 months. The most frequent grade 3-4 toxicities were rash (10%) and neutropaenia (7%). Two patients withdrew due to treatment-related adverse events. At 2 months, RR was 20% according to response evaluation criteria in solid tumours (RECIST) and 86% according to FDG-PET response criteria. Best responses were a complete response in 1/30 patient (3.3%), partial response in 15/30 patients (50%), stable disease in 13/30 patients (43.3%) and progressive disease in 1/30 patient (3.3%); (DCR: 96.7%). Median time-to-response was 5.6 months (0.8-23.8 months). Estimated median PFS was 41.3 months with PFS rate of 59.7% [37.9; 76.0] and 55.4 [33.9; 72.5] at 2 and 3 years, respectively. The OS at 2 and 3 years was stable at 89.9% [71.8; 96.6].

CONCLUSIONS

Masitinib appears to be effective as a first-line treatment of advanced GIST with comparable results to imatinib in terms of safety and response. PFS and in particular OS data show promise that masitinib may provide sustainable benefits. There is sufficient compelling evidence to warrant a phase III clinical trial.

Comparison of two doses of imatinib for the treatment of unresectable or metastatic gastrointestinal stromal tumors: a meta-analysis of 1,640 patients

PURPOSE

The Gastrointestinal Stromal Tumor Meta-Analysis Group (MetaGIST) project aims to additionally explore the data of the two large, randomized, cooperative-group studies comparing two doses of imatinib (400 mg daily v twice daily) in 1,640 patients with advanced GIST.

METHODS

End points were progression-free survival (PFS) and overall survival (OS). Investigated cofactors included age, sex, performance status (PS), primary tumor site, time from diagnosis, prior therapies, baseline biology, and KIT/PDGFRalpha mutations for a subset of 772 patients. Univariate and multivariate models were used for the analysis.

RESULTS

At a median follow-up of 45 months, a small but significant PFS advantage was documented for the high-dose arm. OS was identical in the two arms. The multivariate prognostic models included the following adverse factors: male sex, poor PS, and high baseline neutrophils counts (PFS and OS); low hemoglobin and GIST from small bowel origin (PFS); and advanced age, large tumor size, low albumin level, and prior chemotherapy (OS). In patients analyzed for mutations, patients with wild type, patients with KIT exon 9 mutations, and patients with other mutations had worse prognoses than patients with KIT exon 11 mutations for both end points. The mutation status was the only predictive factor for the PFS benefit attributed to high-dose treatment that resulted in significantly longer PFS (and higher objective response rate) for patients with KIT exon 9 mutations.

CONCLUSION

This analysis confirms a small PFS advantage of high-dose imatinib, essentially among patients with KIT exon 9 mutations, but no OS advantage.

Update on the treatment of gastrointestinal stromal tumors (GISTs): role of imatinib

In the last decade a tremendous amount has been learned about the biology and treatment of gastrointestinal stromal tumor (GIST). Imatinib mesylate has revolutionized the treatment of metastatic GIST. In addition, the role of imatinib in localized GIST has gained much interest and may improve patient outcomes. Additionally, research efforts aimed at understanding the biology and the molecular heterogeneity of GIST both at initial presentation and at the time of resistance to imatinib, has helped guide rational approaches to treatment as well as future efforts aimed at treating imatinib-resistant GIST.

Randomized clinical trials in gastrointestinal stromal tumors

Gastrointestinal (GI) stromal tumor (GIST) is the most common mesenchymal tumor of the GI tract, constituting 80% of all GI mesenchymal tumors and approximately 20% of all small bowel malignancies, excluding lymphomas. This article provides a summary of recent randomized clinical trials of these tumors.

Target therapy in gastrointestinal tract sarcoma: What is new?

Soft tissue sarcoma are rare tumors arising mostly from embryonic mesoderm, that can affect almost any part of the human body, including the gastrointestinal tract. The prognosis associated with soft tissue sarcoma is still poor, mainly because of the low efficacy of traditional approaches based on surgery and chemotherapy. As a result of genetic and molecular analysis, several new target therapies have been developed, leading to a significant improvement in the survival of patients affected by advanced disease. In this review we aim to explore the therapeutic potential and benefit of target therapy in the management of gastrointestinal soft tissue sarcoma and the possible complications or pitfalls of such an approach.

Gastrointestinal stromal tumors: Recommendations on diagnosis, therapy and follow-up care in Austria

Adequate treatment of gastrointestinal stromal tumors (GISTs) is linked to an interdisciplinary treatment approach. Austrian representatives of medical oncology, surgery, pathology, radiology and gastroenterology have issued this consensus manuscript within the context of currently available and published literature. The paper contains guidelines and recommendations for diagnosis, therapy and follow-up of GIST patients in Austria.

Evaluation of imatinib mesylate in the treatment of pulmonary arterial hypertension

Imatinib mesylate is a small molecule inhibitor that selectively inhibits the PDGF receptor kinase as well the cKIT and Abl kinases, among other targets. Various studies have implicated the PDGF pathway in the pathogenesis of pulmonary arterial hypertension (PAH). Inhibition with imatinib mesylate has shown efficacy in human case reports and experimental models of PAH. Results from a Phase II trial of imatinib mesylate in PAH did not meet the primary end point but showed improvement in several secondary end points and in a subgroup analysis. As suggested by this study as well as a few case reports, imatinib may be effective in a subset of patients with more severe disease. However, this remains to be further validated through a Phase III study, which is already underway. In conclusion, it appears that imatinib mesylate may hold promise as an adjunct drug in PAH therapy, especially since it is directed at a pathway not previously targeted.

Cost effectiveness of tyrosine kinase inhibitor therapy in metastatic gastrointestinal stromal tumors

BACKGROUND

Tyrosine kinase inhibitors (TKIs) such as imatinib mesylate have revolutionized the treatment of primary unresectable and/or metastatic gastrointestinal stromal tumors (GISTs), providing durable disease control and extended survival. Although most patients eventually progress on therapy, dose escalation has been shown to benefit some patients. Sunitinib, a multitargeted kinase inhibitor is effective against imatinib-resistant or intolerant GIST patients. Although the cost of TKI therapy in GIST is high, no other effective systemic treatment options exist.

OBJECTIVE

Review pharmacoeconomic studies to determine the cost effectiveness (CE) of 1st- and 2nd-line TKI therapies in GIST.

METHODS

A literature review using Medline and PubMed databases was conducted to identify published economic analyses of TKI therapy in GIST. Key results from these studies were analyzed.

RESULTS

Six pharmacoeconomic studies were identified, including three analyses of 1st-line imatinib and three analyses of 2nd-line sunitinib. These studies employed various time horizons and discount rates and modeled CE from a number of different perspectives. Most of the pharmacoeconomic studies reviewed used survival as their efficacy endpoint, projecting outcomes beyond available data to model CE. Analyses of 2nd-line sunitinib using survival additionally faced the challenge of adjusting for the effect of placebo crossover to active treatment in the pivotal phase III study. Most studies used Markov techniques with a range of transition probabilities.

CONCLUSIONS

Published pharmacoeconomic studies of 1st- and 2nd-line TKI therapy for advanced GIST employ various time horizons, discount rates, and different CE models. Consequently, these differences make comparisons between studies difficult. Studies of 1st-line imatinib concluded that imatinib was cost effective in advanced, metastatic GIST. Likewise, based on data reviewed here, 2nd-line sunitinib appears to be cost effective in patients with advanced GIST who are intolerant/resistant to imatinib. Key limitations of this review included inconsistency among the studies evaluated with regard to methodologies, countries of origination (currency and healthcare systems), and patient demographics.

Gastrointestinal stromal tumors I: pathology, pathobiology, primary therapy, and surgical issues

Gastrointestinal stromal tumor (GISTs) are the most common connective tissue malignancies of the gastrointestinal (GI) tract, with an incidence on the order of 10-13 per million people per year. Primary therapy is usually surgical, but the recurrence rate of large, so-called high-risk tumors, with a high mitotic rate, or those arising from small bowel and colon/rectum is particularly high. The natural history, pathology, and molecular biology of GISTs are discussed in this review, as are features of increasing our analytical power of the genes altered in these tumors, surgical issues, and the translation of research findings into clinical practice. The biological features of GIST make it a model for the examination of kinase-targeted therapeutics in solid tumors.

Gastrointestinal stromal tumors II: medical oncology and tumor response assessment

The finding of mutations of KIT in gastrointestinal stromal tumors (GISTs) and subsequent development of kinase-directed therapy in metastatic GIST serve as a touchstone for the translation of laboratory research into clinical therapeutics. A variety of novel developments have followed the discovery of clinical activity of kinase-directed therapy against GIST. Radiological assessment of GIST challenges the standard of care for assessing tumor responses, ie, Response Evaluation Criteria in Solid Tumors (RECIST). Furthermore, the determination of the relationship of specific KIT mutations and sensitivity and resistance to kinase-directed agents and the assessment of inhibitor levels and the quality of response to those agents have implications beyond the treatment of sarcomas. These discoveries and the next chapters in this developing story are discussed in this review.

Advances in the treatment of gastrointestinal stromal tumor

GIST (gastrointestinal stromal tumor) is a rare soft tissue malignancy arising in the gut. It has become well known recently because of the effectiveness of anti-KIT tyrosine kinase inhibitors. From a disease that 10 years ago was only treatable with surgery, now multiple phase 2 and phase 3 trials have identified active first-line systemic therapy, appropriate dosing, an active second-line agent, and established the role of adjuvant therapy after surgery for patients with intermediate- and high-risk tumors. These are accomplishments that took decades to achieve for other more common diseases such as breast cancer or lung cancer. GIST has been the ideal disease system for studying targeted therapy in solid tumors. The progress in treating GIST has come directly from the advances that have been made in the laboratory, understanding the basic biology of tyrosine kinases, the oncogenic activity of c-KIT, and how that enzymatic activity can be inhibited. By studying model diseases such as GIST, we should be able to develop paradigms to treat more common cancers as well.

[Internal medical therapy of gastrointestinal stroma tumors]

Until recently no active treatment for advanced or metastatic gastrointestinal stroma tumors (GIST) was available. The tyrosine kinase inhibitor imatinib has revolutionized the treatment of this disease and the median overall survival now reaches 5 years. The standard dose of imatinib is 400 mg per day. Locally advanced GIST should be treated with systemic therapy prior to surgical resection. Imatinib was recently licensed for adjuvant therapy following complete surgical removal of GIST in patients with a significant risk of recurrence.

[Treatment of extensive disease]

In locally advanced inoperable patients and metastatic patients imatinib is a standard treatment. Standard dose of imatinib is 400 mg daily. Treatment should be continued indefinitely, since treatment interruption is generally followed by relatively rapid tumor progression in virtually all patients. Dose intensity should be maintained by adequate management of side effects and a correct policy of dose reductions and interruptions in the case of excessive toxicity. The standard approach in the case of tumor progression is to increase the imatinib dose to 800 mg daily with special attention to the occurrence of side effects. Patient non-compliance should be ruled out as a possible cause of tumor progression as well as drug interactions with concomitant medications. In case of progression or intolerance to imatinib standard second-line treatment is sunitinib. The drug was approved effective in terms of progression-free survival according to a 4 weeks on and 2 weeks off regimen. Preliminary data show that a continuous regimen with lower daily dose may be equally effective but possibly better tolerated. After failing on sunitinib, the patient should be considered for participation in a clinical trial of new therapeutic agents or combinations such as tyrosine-kinase inhibitors (e.g., nilotinib), sorafenib, or inhibitors of the mTOR (mammalian target of rapamycin)-pathway.

[Gastrointestinal stromal tumors: recommendations for diagnosis, treatment and aftercare in Austria]

Diagnosis and treatment of gastrointestinal stromal tumors (GIST) requires an interdisciplinary treatment approach. This strategy should be reflected by the content of this article. Austrian representatives of 'GIST relevant' specialties authored this publication on a consensual base. This manuscript should be regarded as a guideline for 'GIST involved' colleagues in Austria.

Pharmacological management of gastrointestinal stromal tumours: an update on the role of sunitinib

The efficacy and tolerability of the receptor tyrosine kinase inhibitor, sunitinib malate, have been demonstrated in phase I-III clinical trials of patients with imatinib-resistant or imatinib-intolerant gastrointestinal stromal tumours (GIST) as well as in a worldwide expanded-access study and in a continuous daily dosing (CDD) trial. Tumour genotype may have a significant influence on the activity of sunitinib in patients with imatinib-resistant GIST. Sunitinib activity was observed across different GIST genotypes and particularly in patients with wild-type and KIT exon 9 mutations (all relatively resistant to standard-dose imatinib) and in patients with secondary KIT exons 13 and 14 mutations. Adverse events with sunitinib were generally mild to moderate and easily managed by dose reduction, dose interruption or standard supportive measures. Treatment discontinuation can be avoided in most patients by close monitoring before and during treatment with appropriate adverse event management as necessary. The correlation between treatment exposure and clinical response is prompting the search for new approaches to treatment optimisation to ensure that patients derive maximum benefit from sunitinib therapy, including dose adjustments based on blood testing to ensure optimal drug exposure, and the use of the alternative CDD regimen to avoid treatment interruption.

Gene expression signatures and response to imatinib mesylate in gastrointestinal stromal tumor

Despite initial efficacy of imatinib mesylate in most gastrointestinal stromal tumor (GIST) patients, many experience primary/secondary drug resistance. Therefore, clinical management of GIST may benefit from further molecular characterization of tumors before and after imatinib mesylate treatment. As part of a recent phase II trial of neoadjuvant/adjuvant imatinib mesylate treatment for advanced primary and recurrent operable GISTs (Radiation Therapy Oncology Group S0132), gene expression profiling using oligonucleotide microarrays was done on tumor samples obtained before and after imatinib mesylate therapy. Patients were classified according to changes in tumor size after treatment based on computed tomography scan measurements. Gene profiling data were evaluated with Statistical Analysis of Microarrays to identify differentially expressed genes (in pretreatment GIST samples). Based on Statistical Analysis of Microarrays [False Discovery Rate (FDR), 10%], 38 genes were expressed at significantly lower levels in the pretreatment biopsy samples from tumors that significantly responded to 8 to 12 weeks of imatinib mesylate, that is, >25% tumor reduction. Eighteen of these genes encoded Krüppel-associated box (KRAB) domain containing zinc finger (ZNF) transcriptional repressors. Importantly, 10 KRAB-ZNF genes mapped to a single locus on chromosome 19p, and a subset predicted likely response to imatinib mesylate-based therapy in a naïve panel of GIST. Furthermore, we found that modifying expression of genes within this predictive signature can enhance the sensitivity of GIST cells to imatinib mesylate. Using clinical pretreatment biopsy samples from a prospective neoadjuvant phase II trial, we have identified a gene signature that includes KRAB-ZNF 91 subfamily members that may be both predictive of and functionally associated with likely response to short-term imatinib mesylate treatment.

Gastrointestinal stromal tumor

BACKGROUND

GISTs are a subset of mesenchymal tumors and represent the most common mesenchymal neoplasms of GI tract. However, GIST is a recently recognized tumor entity and the literature on these stromal tumors has rapidly expanded.

METHODS

An extensive review of the literature was carried out in both online medical journals and through Athens University Medical library. An extensive literature search for papers published up to 2009 was performed, using as key words, GIST, Cajal's cells, treatment, Imatinib, KIT, review of each study were conducted, and data were abstracted.

RESULTS

GIST has recently been suggested that is originated from the multipotential mesenchymal stem cells. It is estimated that the incidence of GIST is approximately 10-20 per million people, per year.

CONCLUSION

The clinical presentation of GIST is variable but the most usual symptoms include the presence of a mass or bleeding. Surgical resection of the local disease is the mainstay therapy. However, therapeutic agents, such as Imatinib have now been approved for the treatment of advanced GISTs and others, such as everolimus, rapamycin, heat shock protein 90 and IGF are in trial stage demonstrate promising results for the management of GISTs.

Absence of progression as assessed by response evaluation criteria in solid tumors predicts survival in advanced GI stromal tumors treated with imatinib mesylate: the intergroup EORTC-ISG-AGITG phase III trial

PURPOSE

From February 2001 to February 2002, 946 patients with advanced GI stromal tumors (GISTs) treated with imatinib were included in a controlled EORTC/ISG/AGITG (European Organisation for Research and Treatment of Cancer/Italian Sarcoma Group/Australasian Gastro-Intestinal Trials Group) trial. This analysis investigates whether the response classification assessed by RECIST (Response Evaluation Criteria in Solid Tumors), predicts for time to progression (TTP) and overall survival (OS).

PATIENTS AND METHODS

Per protocol, the first three disease assessments were done at 2, 4, and 6 months. For the purpose of the analysis (landmark method), disease response was subclassified in six categories: partial response (PR; > 30% size reduction), minor response (MR; 10% to 30% reduction), no change (NC) as either NC- (0% to 10% reduction) or NC+ (0% to 20% size increase), progressive disease (PD; > 20% increase/new lesions), and subjective PD (clinical progression).

RESULTS

A total of 906 patients had measurable disease at entry. At all measurement time points, complete response (CR), PR, and MR resulted in similar TTP and OS; this was also true for NC- and NC+, and for PD and subjective PD. Patients were subsequently classified as responders (CR/PR/MR), NC (NC+/NC-), or PD. This three-class response categorization was found to be highly predictive of further progression or survival for the first two measurement points. After 6 months of imatinib, responders (CR/PR/MR) had the same survival prognosis as patients classified as NC.

CONCLUSION

RECIST perfectly enables early discrimination between patients who benefited long term from imatinib and those who did not. After 6 months of imatinib, if the patient is not experiencing PD, the pattern of radiologic response by tumor size criteria has no prognostic value for further outcome. Imatinib needs to be continued as long as there is no progression according to RECIST.

Does imatinib turn recurrent and/or metastasized gastrointestinal stromal tumors into a chronic disease? - single center experience

BACKGROUND

Gastrointestinal stromal tumors (GIST) are mesenchymal tumors of the gastrointestinal tract supposed to arise from the cells of Cajal because of gain-of-function mutations of the tyrosine receptor kinases c-kit or platelet-derived growth factor receptor A. Imatinib selectively inhibits the kinase activity of both receptors. Despite this breakthrough in the treatment of GIST, resistance against imatinib has been reported to be as high as 50% after the first 2 years of treatment.

AIM

Outcome of 13 consecutive patients with relapsed or metastasized GIST who were treated with imatinib was analyzed.

RESULTS

Mean duration of treatment was 53.5 months. Four patients developed progressive disease and died after a mean treatment time of 31 months in spite of increase of imatinib dosages to 800 mg daily. Two patients (23%) developed a progressive disease after 46 months or 52 months of treatment. Two patients had a stable disease and five had a partial response. The overall progression rate was 46%, the mean survival time since primary diagnosis was 85.8 months.

CONCLUSION

From our experience, frequency of resistance development to imatinib may be below that given in the literature (50% after 2 years). Individual treatment in specialized centers may improve compliance.

Current clinical strategy for imatinib-resistant gastrointestinal stromal tumors

Before the advent of imatinib, no effective agent was available for the treatment of unresectable or metastatic gastrointestinal stromal tumors (GISTs). However, the treatment strategy changed and the prognosis of patients with advanced or recurrent GIST improved remarkably after the development of imatinib. Despite the high rate of clinical benefit of imatinib in GIST patients, more than half of GIST patients eventually develop primary or secondary resistance to imatinib, resulting in the progression of the disease. It has also been reported that about 5% of patients are intolerant to imatinib. An effective treatment strategy for imatinib-resistant GIST is needed. The National Comprehensive Cancer Network guidelines recommend a multidisciplinary approach, but the therapeutic modalities are still limited, and none are able to achieve complete remission. In this review, we summarize the current understandings of the mechanism of imatinib resistance and the clinical strategies used against imatinib-resistant GIST, including surgical intervention, escalation of imatinib dose, and use of sunitinib or other agents. Understanding these issues may help in the development of a new treatment paradigm for GIST patients.

A phase I study of the P-glycoprotein antagonist tariquidar in combination with vinorelbine

PURPOSE

P-glycoprotein (Pgp) antagonists have had unpredictable pharmacokinetic interactions requiring reductions of chemotherapy. We report a phase I study using tariquidar (XR9576), a potent Pgp antagonist, in combination with vinorelbine.

EXPERIMENTAL DESIGN

Patients first received tariquidar alone to assess effects on the accumulation of (99m)Tc-sestamibi in tumor and normal organs and rhodamine efflux from CD56+ mononuclear cells. In the first cycle, vinorelbine pharmacokinetics was monitored after the day 1 and 8 doses without or with tariquidar. In subsequent cycles, vinorelbine was administered with tariquidar. Tariquidar pharmacokinetics was studied alone and with vinorelbine.

RESULTS

Twenty-six patients were enrolled. Vinorelbine 20 mg/m(2) on day 1 and 8 was identified as the maximum tolerated dose (neutropenia). Nonhematologic grade 3/4 toxicities in 77 cycles included the following: abdominal pain (4 cycles), anorexia (2), constipation (2), fatigue (3), myalgia (2), pain (4) and dehydration, depression, diarrhea, ileus, nausea, and vomiting, (all once). A 150-mg dose of tariquidar: (1) reduced liver (99m)Tc-sestamibi clearance consistent with inhibition of liver Pgp; (2) increased (99m)Tc-sestamibi retention in a majority of tumor masses visible by (99m)Tc-sestamibi; and (3) blocked Pgp-mediated rhodamine efflux from CD56+ cells over the 48 hours examined. Tariquidar had no effects on vinorelbine pharmacokinetics. Vinorelbine had no effect on tariquidar pharmacokinetics. One patient with breast cancer had a minor response, and one with renal carcinoma had a partial remission.

CONCLUSIONS

Tariquidar is a potent Pgp antagonist, without significant side effects and much less pharmacokinetic interaction than previous Pgp antagonists. Tariquidar offers the potential to increase drug exposure in drug-resistant cancers.

Adjuvant imatinib mesylate after resection of localised, primary gastrointestinal stromal tumour: a randomised, double-blind, placebo-controlled trial

BACKGROUND

Gastrointestinal stromal tumour is the most common sarcoma of the intestinal tract. Imatinib mesylate is a small molecule that inhibits activation of the KIT and platelet-derived growth factor receptor alpha proteins, and is effective in first-line treatment of metastatic gastrointestinal stromal tumour. We postulated that adjuvant treatment with imatinib would improve recurrence-free survival compared with placebo after resection of localised, primary gastrointestinal stromal tumour.

METHODS

We undertook a randomised phase III, double-blind, placebo-controlled, multicentre trial. Eligible patients had complete gross resection of a primary gastrointestinal stromal tumour at least 3 cm in size and positive for the KIT protein by immunohistochemistry. Patients were randomly assigned, by a stratified biased coin design, to imatinib 400 mg (n=359) or to placebo (n=354) daily for 1 year after surgical resection. Patients and investigators were blinded to the treatment group. Patients assigned to placebo were eligible to crossover to imatinib treatment in the event of tumour recurrence. The primary endpoint was recurrence-free survival, and analysis was by intention to treat. Accrual was stopped early because the trial results crossed the interim analysis efficacy boundary for recurrence-free survival. This study is registered with ClinicalTrials.gov, number NCT00041197.

FINDINGS

All randomised patients were included in the analysis. At median follow-up of 19.7 months (minimum-maximum 0-56.4), 30 (8%) patients in the imatinib group and 70 (20%) in the placebo group had had tumour recurrence or had died. Imatinib significantly improved recurrence-free survival compared with placebo (98% [95% CI 96-100] vs 83% [78-88] at 1 year; hazard ratio [HR] 0.35 [0.22-0.53]; one-sided p<0.0001). Adjuvant imatinib was well tolerated, with the most common serious events being dermatitis (11 [3%] vs 0), abdominal pain (12 [3%] vs six [1%]), and diarrhoea (ten [2%] vs five [1%]) in the imatinib group and hyperglycaemia (two [<1%] vs seven [2%]) in the placebo group.

INTERPRETATION

Adjuvant imatinib therapy is safe and seems to improve recurrence-free survival compared with placebo after the resection of primary gastrointestinal stromal tumour.

FUNDING

US National Institutes of Health and Novartis Pharmaceuticals.

Gastrointestinal stromal tumors (GISTs): a review

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms in the gastrointestinal tract, which, over the last 10 years, have emerged from a poorly understood neoplasm to a well-defined tumor entity exhibiting particular molecular abnormalities and for which promising novel treatment modalities have been developed. GISTs probably arise from the precursor cell of the interstitial cell of Cajal, express KIT tyrosine kinase in most of the cases and harbor mutations of importance for individualized treatment. The molecular targets for therapeutic interventions are not only of importance for the treatment of GIST patients but also useful for in the development of novel drug modalities and new strategies in basic cancer therapy.

New therapeutic approaches for advanced gastrointestinal stromal tumors

The management of advanced gastrointestinal stromal tumor is increasingly complex because of imatinib refractory disease. Primary resistance to imatinib is uncommon, and most patients progress after development of additional genetic changes. This article reviews management strategies including surgical approaches, local modalities for progressive liver metastases, as well as novel therapeutic agents.

Imatinib in the treatment of solid tumours

The extraordinary success of imatinib in gastrointestinal stromal tumors (GIST) represents a model for molecularly targeted therapy for other solid tumors. Research is currently going to identify the molecular basis of mechanisms of action and drug resistance. In this article, we review recent advances in the clinical management of patients with GISTs treated with imatinib, but also of patients with dermatofibrosarcoma protuberans, chordoma, aggressive fibromatosis, and some other common solid tumors treated with this drug. We reviewed the knowledge of the molecular mechanisms that are basic to imatinib effects in these tumors.

Early prediction of response to sunitinib after imatinib failure by 18F-fluorodeoxyglucose positron emission tomography in patients with gastrointestinal stromal tumor

PURPOSE

Positron emission tomography with (18)F-fluorodeoxyglucose (FDG-PET) was used to evaluate treatment response in patients with gastrointestinal stromal tumors (GIST) after administration of sunitinib, a multitargeted tyrosine kinase inhibitor, after imatinib failure.

PATIENTS AND METHODS

Tumor metabolism was assessed with FDG-PET before and after the first 4 weeks of sunitinib therapy in 23 patients who received one to 12 cycles of sunitinib therapy (4 weeks of 50 mg/d, 2 weeks off). Treatment response was expressed as the percent change in maximal standardized uptake values (SUV). The primary end point of time to tumor progression was compared with early PET results on the basis of traditional Response Evaluation Criteria in Solid Tumors (RECIST) criteria.

RESULTS

Progression-free survival (PFS) was correlated with early FDG-PET metabolic response (P < .0001). Using -25% and +25% thresholds for SUV variations from baseline, early FDG-PET response was stratified in metabolic partial response, metabolically stable disease, or metabolically progressive disease; median PFS rates were 29, 16, and 4 weeks, respectively. Similarly, when a single FDG-PET positive/negative was considered after 4 weeks of sunitinib, the median PFS was 29 weeks for SUVs less than 8 g/mL versus 4 weeks for SUVs of 8 g/mL or greater (P < .0001). None of the patients with metabolically progressive disease subsequently responded according to RECIST criteria. Multivariate analysis showed shorter PFS in patients who had higher residual SUVs (P < .0001), primary resistance to imatinib (P = .024), or nongastric GIST (P = .002), regardless of the mutational status of the KIT and PDGFRA genes.

CONCLUSION

Week 4 FDG-PET is useful for early assessment of treatment response and for the prediction of clinical outcome. Thus, it offers opportunities to individualize and optimize patient therapy.

Dose escalation of imatinib after failure of standard dose in Korean patients with metastatic or unresectable gastrointestinal stromal tumor

OBJECTIVE

We evaluated the results of imatinib dose escalation in patients with advanced gastrointestinal stromal tumors (GISTs) after disease progression on standard-dose imatinib.

METHODS

Clinical data from patients with metastatic or unresectable GISTs whose dose of imatinib was increased after disease progression on imatinib 400 mg/day were retrospectively reviewed.

RESULTS

The 24 patients studied had a median age of 52 years. Imatinib dosing was escalated to 600 mg/day in 12 patients, then to 800 mg/day in four patients. The other 12 patients had dose escalation directly to 800 mg/day. Two patients (8.3%) achieved a partial response, and seven (29.2%) had stable disease. Six-month progression-free and overall survival rates were 33.3 and 70.7%, respectively. Dose escalation to 600 or 800 mg/day was generally well tolerated.

CONCLUSION

Imatinib dose escalation is feasible and well tolerated in patients with advanced GIST who progress on standard-dose therapy, producing clinical benefit in approximately 37% of patients.

Consensus approaches to best practice management of gastrointestinal stromal tumors

Gastrointestinal stromal tumors are rare mesenchymal tumors of the gastrointestinal tract. Progress in diagnosis has led to increased recognition of this disease, and the availability of effective, molecularly targeted therapy has revolutionised its management. Treatment of metastatic gastrointestinal stromal tumors with imatinib has led to unprecedented improvements in progression free and overall survival and there are ongoing investigations into the optimal pre‐operative and adjuvant use of imatinib. Second‐line sunitinib is now available for patients who develop resistance to imatinib, and third‐ and fourth‐line therapies are being investigated in clinical trials. In this ever‐changing environment, evidence from controlled clinical trials and the authors' experience were used to comprehensively outline current best practice management of patients with gastrointestinal stromal tumors.

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S. Bonvalot Complete resection without tumor rupture remains the mainstay of the treatment in patients with localized, resectable GIST. Operative indications should take account of size and location of the tumor which impact the risk of recurrence. More micro-GIST are discovered with the development of investigations, rising the question of wait and see policy for some of them. In locally advanced inoperable patients and metastatic patients, Imatinib is the standard treatment. Secondary excision of residual disease has been shown to be related to a good prognosis in responding patients to imatinib, but it is still not demonstrated whether this is due to surgery itself or to a selection bias. A phase 3 EORTC study will start and will randomise this secondary surgery after 6 to 12 months of imatinib in responding patients.