Imatinib mesylate (STI-571 Glivec, Gleevec) is an active agent for gastrointestinal stromal tumours, but does not yield responses in other soft-tissue sarcomas that are unselected for a molecular target. Results from an EORTC Soft Tissue and Bone Sarcoma Group phase II study

Colorectal gastrointestinal stromal tumor

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal neoplasm arising in the digestive tract, with an estimated prevalence of 15-20 per 1,000,000. GISTs are related to the interstitial cells of Cajal and are characterized by constitutive over-expression of the transmembrane tyrosine kinase receptor KIT. This is produced by a patognomonic mutation of the proto-oncogene c-kit that occurs in up to 90% of cases. Exon 11 is affected most frequently; exons 9 and 13 are less commonly involved. One-third of GISTs lacking KIT mutations exhibits alternative activating mutations in the PDGFRα gene. Colorectal GISTs represent about 5-10% of the cases, mainly located in the rectum that is the third common site. Benign GISTs are more common, but many tumors are of uncertain malignant potential; tumor size and rate of mitosis are still the most reliable criteria for assessing the risk of an aggressive behavior. Surgery is the first-line treatment for resectable non-metastatic colorectal GIST. Standard oncologic resection is inappropriate because skip metastases and lymphatic spread are rarely reported. Segmental colectomy with negative margins is recommended, and local excision is oncologically adequate in highly selected rectal tumors. Radical surgery alone is not always curative especially in high-risk GISTs, and half of patients develops local recurrences or distant metastases after R0 operation. Medical therapeutic strategies have rapidly evolved after the introduction of targeted molecular therapy. Efficacy and safety of imatinib mesylate was first demonstrated in patients with metastatic and unresectable disease. Adjuvant and neoadjuvant use of imatinib are promising therapeutic options to improve the outcome of surgery to downstage unresectable lesions and to allow less extensive resections.

A USA registry of gastrointestinal stromal tumor patients: changes in practice over time and differences between community and academic practices

BACKGROUND

The objective of the study was to describe patterns of care of patients with gastrointestinal stromal tumors (GISTs) in the United States in the tyrosine kinase inhibitor (TKI) era.

PATIENTS AND METHODS

From November 2004 through March 2009, data were collected regarding demographics, diagnostic history, treatment, relapse, and survival of 882 patients with GIST from 122 community and academic medical practices.

RESULTS

The most common first-line treatment for the 719 patients presenting with localized GIST was surgery (87%). Use of adjuvant imatinib increased after June 2007; 47% of patients enrolled in the registry considered by the investigator to be at high risk for recurrence received adjuvant imatinib after June 2007 versus 18% before. Overall, 56% of patients received imatinib and 11% received sunitinib. The utilization of targeted therapy increased over time (45% and 0.4% of patients received imatinib and sunitinib, respectively, in 2006 versus 56% and 11%, respectively, in 2009).

CONCLUSIONS

These are the first GIST registry data from the TKI era. The use of targeted therapy for GIST has increased in accordance with updated treatment guidelines. Diagnosis of GIST has evolved with increased use of KIT testing. The duration of targeted therapy in the adjuvant therapy setting is similar in community and academic practices.

Breast sarcomas: current and future perspectives

Breast sarcomas are rare neoplasms of the breast that need to be clearly distinguished from the very common breast carcinomas and treated in a multidisciplinary manner modelled after treatment paradigms in other sarcoma locations. An increasing need to differentiate sarcoma sub-types based on molecular characteristics that will also be depicted in differential treatment sensitivities and development of specifically targeted therapies are equally valid in sarcomas in general and in breast sarcomas in particular. Of special interest in breast are sarcomas developing after breast irradiation for a previous breast carcinoma, a scenario that is increasingly common, given the increasing trends of breast conservation in the surgical treatment of breast carcinoma that necessitates the adjuvant use of radiotherapy.

Imatinib mesylate for the treatment of gastrointestinal stromal tumor

Gastrointestinal stromal tumors (GISTs) are rare neoplasms of mesenchymal origin arising in the GI tract. These tumors are characterized by activating mutations of either receptor tyrosine kinase KIT or PDGFRA, which are found in 85% of cases. The introduction of imatinib mesylate (IM), which targets the kinases presenting with these molecular alterations, has dramatically changed the management of these rare tumors, which were resistant to conventional cytotoxic chemotherapy, both in advanced and localized phases. IM is orally available, has a favorable safety profile and induces partial responses and disease stabilization in up to 80% of patients with advanced GIST. Recently, IM was approved for the postoperative treatment of patients with completely resected localized GIST.

Imatinib: as adjuvant therapy for gastrointestinal stromal tumour

Imatinib is a protein-tyrosine kinase inhibitor with antitumour effects in patients with gastrointestinal stromal tumour (GIST) that is indicated for the treatment of unresectable and/or metastatic GIST and as adjuvant therapy in patients with KIT-positive GIST. Imatinib binds to and inhibits KIT and platelet-derived growth factor receptor (PDGFR)-α tyrosine kinases, interfering with their downstream tumourogenic processes. Cell lines with KIT mutations that are common in patients with GIST were sensitive to imatinib at low in vitro concentrations. Patients with exon 11 KIT mutations were significantly more likely to have partial tumour responses and longer overall survival (OS) and were significantly less likely to have progression of disease than patients with exon 9 KIT mutations or no detectable KIT or PDGFR mutations. In a large (n > 700) randomized, double-blind, placebo-controlled, multinational trial (ACOSOG [American College of Surgeons Oncology Group] Z9001), patients who received 1 year of adjuvant treatment with oral imatinib 400 mg/day after surgical resection of GIST had significantly longer recurrence-free survival than placebo recipients, with an overall hazard ratio of 0.35 (95% CI 0.22, 0.53) [primary endpoint]. At the time of reporting, there was no significant between-group difference in OS. In patients with GIST who received adjuvant imatinib in this trial, adverse events were mostly of mild or moderate severity; the imatinib treatment group had an almost 2-fold higher rate of US National Cancer Institute Common Toxicity Criteria grade 3 or 4 adverse events than the placebo group.

Imatinib mesylate does not increase bone volume in vivo

Imatinib mesylate is a tyrosine kinase inhibitor used in the management of disorders in which activation of c-Abl, PDGFR, or c-Kit signaling plays a critical role. In vitro, imatinib stimulates osteoblast differentiation, inhibits osteoblast proliferation and survival, and decreases osteoclast development. Patients treated with imatinib exhibit altered bone and mineral metabolism, with stable or increased bone mass. However, recovery from the underlying disease and/or weight gain might contribute to these effects. We therefore investigated the skeletal effects of imatinib in healthy rats. We evaluated the effects of imatinib on bone volume, markers of bone turnover, and bone histomorphometry in mature female rats treated for 5 weeks with either vehicle, imatinib 40 mg/kg daily, or imatinib 70 mg/kg daily. Compared to vehicle, imatinib reduced trabecular bone volume/tissue volume (mean [SD]: vehicle 26.4% [5.4%], low-dose imatinib 24.8% [4.9%] [P = 0.5], high-dose imatinib 21.1% [5.7%] [P = 0.05]), reduced osteoblast surface (mean [SD]: vehicle 12.8% [5.8%], low-dose 6.8% [1.9%] [P < 0.01], high-dose 7.8 [3.1%] [P < 0.05]), and reduced serum osteocalcin (mean change from baseline [95% CI]: vehicle -8.2 [-26.6 to 10.2] ng/ml, low dose -79.7 [-97.5 to -61.9] ng/ml [P < 0.01 vs. vehicle], high-dose -66.0 [-82.0 to -50.0] ng/ml [P < 0.05 vs. vehicle]). Imatinib did not affect biochemical or histomorphometric indices of bone resorption. These results suggest that, in healthy animals, treatment with imatinib does not increase bone mass and that the improvements in bone density reported in patients receiving imatinib may not be a direct effect of the drug.

A decade of tyrosine kinase inhibitor therapy: Historical and current perspectives on targeted therapy for GIST

The introduction of molecularly targeted therapies has ushered in a considerable transformation in the management of gastrointestinal stromal tumors (GIST) that currently defines the paradigm of targeted therapy for solid tumors. Indeed, in the past decade the management of GIST has evolved from a disease only effectively treatable by surgery to the archetype of a tumor treatable with a molecularly targeted therapy. Better understanding of the molecular and genetic characteristics that underlie the aberrant behavior of GIST has increased the accuracy of its diagnosis and allowed for the identification of distinct genetic hallmarks, prognostic groups, and treatment strategies. Collectively, this has resulted in the development of the targeted tyrosine kinase inhibitors (TKIs) imatinib and sunitinib, and continues to prompt studies of novel agents in this disease. Since approval in 2002, imatinib has been shown to provide a high level of clinical efficacy in patients with advanced GIST, including a median progression-free survival (PFS) of 2 years and median overall survival approaching 5 years, with some patients progression-free after 10 years of treatment. Imatinib is now also approved in adult patients following resection of KIT-positive GIST. In 2006, sunitinib was approved for the treatment of advanced GIST after failure of imatinib. Sunitinib provides significant benefit in this setting, with a median PFS close to 6 months after imatinib failure. Following progression on these agents, patients have limited treatment options. This critical unmet need is being addressed by the development of new TKIs and the use of novel regimens with approved agents.

DNA repair and personalized breast cancer therapy

Personalized cancer therapy is likely to be one of the next big advances in our search for a cure for cancer. To be able to treat people in an individualized manner, researchers need to know a great deal about their genetic constitution and the DNA repair status of their tumors. Specific knowledge is required regarding the polymorphisms individuals carry and how these polymorphisms influence responses to therapy. Researchers are actively engaged in biomarker discovery and validation for this purpose. In addition, the design of clinical trials must be reassessed to include new information on biomarkers and drug responses. In this review, we focus on personalized breast cancer therapy. The hypothesis we focus upon in this review is that there is connection between the DNA repair profile of individuals, their breast tumor subtypes, and their responses to cancer therapy. We first briefly review cellular DNA repair pathways that are likely to be impacted by breast cancer therapies. Next, we review the phenotypes of breast tumor subtypes with an emphasis on how a DNA repair deficiency might result in tumorigenesis itself and lead to the chemotherapeutic responses that are observed. Specific examples of breast tumor subtypes and their responses to cancer therapy are given, and we discuss possible DNA repair mechanisms that underlie the responses of tumors to various chemotherapeutic agents. Much is known about breast cancer subtypes and the way each of these subtypes responds to chemotherapy. In addition, we discuss novel design of clinical trials that incorporates rapidly emerging information on biomarkers.

Pediatric and wild-type gastrointestinal stromal tumor: new therapeutic approaches

PURPOSE OF REVIEW

Pediatric gastrointestinal stromal tumor is an uncommon tumor, the rarity of which has made both laboratory research studies and clinical management very difficult. As we learn more about this disorder, what is emerging is that this rare cancer is markedly different in children and adults. One of the main biological differences is that pediatric patients lack activating mutations in the oncogenes that drive tumor formation in adults. The natural history of this disease also appears to be more indolent in children than in adults. In this review, we will discuss the differences between children and adults with gastrointestinal stromal tumor and some new potential therapeutic agents.

RECENT FINDINGS

This review discusses recent advances and the rationale for several recently identified molecular targets. In addition, we discuss the formation of a clinic at the National Institutes of Health that is dedicated to the study of this rare disorder.

SUMMARY

Collaborative efforts are underway to better define the natural history and clinical course of pediatric patients with gastrointestinal stromal tumor. When combined with innovative genomic and molecular studies, these dual approaches will allow for notable advances in this field.

Gene expression profiling of human gastrointestinal stromal tumors according to its malignant potential

PURPOSE

Surgical removal or treatment with Imatinib mesylate (STI-571/Gleevec) is shown to be highly effective in gastrointestinal stromal tumors (GISTs). However, it is unclear the understanding of the molecular basis in GISTs according to its malignant potential. The aim of this study was therefore to determine the gene expression profiles according to GISTs risk progresses.

RESULTS

In this study, we performed a cDNA microarray with 30 human GIST tissues using the Mac Array-Express 10K chip (10,800 genes), and compared their gene expression profiles among low (n=10), intermediate (n=8), and high-risk groups (n=12) according to NIH consensus criteria. A total of 181 genes were identified to be expressed differentially according to GISTs risk category. After clustering by self-organizing maps, the expression profiles of 32 genes sequentially increased as the tumor risk increased, and those of 37 genes sequentially decreased as the tumor risk increased. Identified targets have been cross referenced against their involvements in different cellular pathways, according to GenMAPP, KEGG, and BioCarta. In pathway-enrichment analysis, eight up-regulated pathways and ten down-regulated pathways were significantly enriched.

CONCLUSIONS

Our results showed a remarkably distinct and uniform expression pattern in GISTs progression. Moreover, the expression profiling of GISTs may be used as a basic reference to better understand the molecular basis of GISTs tumorigenesis and to identify a novel target molecule for replacing KIT and PDGFRA for a complementary diagnosis and effective curative treatments.

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.

Prognostic and predictive factors for outcome to first-line ifosfamide-containing chemotherapy for adult patients with advanced soft tissue sarcomas: an exploratory, retrospective analysis on large series from the European Organization for Research and Treatment of Cancer-Soft Tissue and Bone Sarcoma Group (EORTC-STBSG)

BACKGROUND

Adult patients with advanced soft tissue sarcomas (STS) are generally treated similarly, regardless of great differences between STS subtypes, disease presentation and patients' characteristics. As ifosfamide is frequently applied in first line systemic therapy, we aimed to establish prognostic and predictive factors for outcome to ifosfamide-based therapy.

METHODS

A retrospective, exploratory analysis was performed on data from 1337 advanced STS patients who received first-line ifosfamide-containing chemotherapy. For predictive factor analysis, 660 patients treated with doxorubicin monotherapy served as comparators.

RESULTS

Independent favourable prognostic factors for overall survival (OS) were good performance status, female gender, low histological grade, extremity primary tumour site and locally advanced disease; for progression-free survival (PFS), the combination of doxorubicin and ifosfamide, locally advanced disease, and tumour entity with a lower risk to progress for synovial sarcoma patients compared to leiomyosarcoma. For response, independent favourable prognostic factors were doxorubicin combined with ifosfamide, higher histological grade, and histology with synovial sarcoma patients having the highest chance to respond. Predictive factor analysis showed that compared to doxorubicin monotherapy, patients who benefited less from ifosfamide-based therapies were leiomyosarcoma patients in terms of OS, and patients with liposarcoma for response. No predictive factors were found for PFS.

CONCLUSION

In this study, we established an independent set of prognostic and predictive factors for outcome to ifosfamide-based chemotherapy in advanced STS patients. This study provides important information for the interpretation and design of clinical trials for specific STS entities and may contribute to further treatment individualisation of advanced STS patients.

Everolimus alters imatinib blood partition in favour of the erythrocyte

The signal transduction inhibitor imatinib is one of the latest breakthroughs in cancer pharmacotherapy. It is administered orally over prolonged periods of time for the treatment of gastrointestinal stromal tumours. Routine therapeutic drug monitoring of blood plasma versus red blood cells over several years by liquid chromatography coupled tandem mass spectrometry has highlighted a very intriguing phenomenon. Imatinib plasma availability decreases dramatically owing to a significant shift in the partition ratio of red blood cells versus plasma. The shift is enforced by combination with everolimus, another signal transduction inhibitor. These data warrant routine erythrocyte versus plasma monitoring to prevent unexpected alterations in drug efficacy during long-term treatment.

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.

Outcomes of first-line chemotherapy in patients with advanced or metastatic leiomyosarcoma of uterine and non-uterine origin

Although leiomyosarcomas (LMSs) form the largest subgroup of soft tissue sarcomas (STSs), the efficacy of chemotherapy in this group is largely unclear, partly because older studies are contaminated with gastrointestinal stromal tumors (GISTs). In this retrospective study we investigated the outcome of first line chemotherapy in 65 patients with unresectable or metastatic LMS. The overall response rate (ORR) was 18%; and the median progression-free (PFS) and overall survival (OS) were 3.8 and 9.7 months respectively. No statistically significant differences in outcomes for uterine and non-uterine LMS were found. In non-uterine LMS, however, the PFS and OS seemed to be longer for females than for males, potentially negatively affecting outcomes in this group. If our observations are confirmed in other series, they would suggest that studies performed in STS patients should not only stratify for histological subtype but also for uterine versus non-uterine LMS and for gender.

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.

Phase II multicenter trial of imatinib in 10 histologic subtypes of sarcoma using a bayesian hierarchical statistical model

PURPOSE The purpose of this trial was to assess the efficacy of imatinib in patients with one of 10 different subtypes of advanced sarcoma. PATIENTS AND METHODS Eligible patients were treated daily with imatinib dosed at 300 mg twice a day (for body-surface area > or = 1.5 m(2)). The primary end point was response (clinical benefit response [CBR]), defined as complete (CR) or partial response (PR) at 2 months, or stable disease, CR, or PR at 4 months. Rules for early termination within each disease type were based on a Bayesian hierarchical probability model (BHM) accounting for correlation of the responses of the 10 subtypes. Available tissue samples were analyzed for molecules within the KIT/platelet-derived growth factor receptor (PDGFR) signal transduction pathway. Results One hundred eighty-five assessable patients with one of 10 subtypes of sarcoma were treated. One CR and three PRs were achieved. A CBR was achieved in 28 patients treated overall and by subtype: two angiosarcomas (n = 16), 0 Ewing (n = 13), one fibrosarcoma (n = 12), six leiomyosarcomas (n = 29), seven liposarcomas (n = 31), three malignant fibrous histiocytomas (n = 30), five osteosarcomas (n = 27), one malignant peripheral-nerve sheath tumor (n = 7), 0 rhabdomyosarcoma (n = 2), and three synovial sarcomas (n = 22). Variable expression and mutations within the KIT/PDGFR pathway were observed. CONCLUSION This is the first phase II study of a new agent in sarcoma to include sufficient patients with each of the common histologic subtypes to permit generalizable conclusions. The BHM is an effective method for studying rare diseases and their subtypes, when it is reasonable to assume that their response rates are exchangeable. Although rare dramatic responses were seen, imatinib is not an active agent in advanced sarcoma in these subtypes.

Kinase mutations and efficacy of imatinib in Korean patients with advanced gastrointestinal stromal tumors

PURPOSE

This study analyzed the relationship between treatment outcome and kinase mutational status in Korean patients with advanced gastrointestinal stromal tumors (GISTs).

EXPERIMENTAL DESIGN

Clinical data were collected from 113 consecutive patients with metastatic or unresectable GISTs treated with imatinib from June 2001 through June 2005 at five institutions in Korea. KIT exons 9, 11, 13, and 17 and PDGFRA exons 12 and 18 were examined.

RESULTS

The median patient age was 57 years (range, 31-82 years). The overall response rate was 67.2%. KIT mutations were found in exon 11 (n = 92, 81.4%) and exon 9 (n = 10, 8.8%). One patient had a PDGFRA exon 18 mutation. The overall mutation rate was 91.2%. Response rates were 68.4%, 50.0%, and 80.0% in patients with KIT exon 11 mutations, KIT exon 9 mutations, and no kinase mutations, respectively. With a median follow-up of 49.0 months, the median progression-free survival (PFS) time was 42.0 months and median overall survival (OS) time was not reached. PFS and OS times did not differ significantly according to KIT genotype.

CONCLUSION

This study was unable to find an association between KIT mutational status and clinical outcome of imatinib in Korean patients with advanced GISTs. There was a trend toward better outcomes for patients with wild-type KIT or exon 11 mutations compared with exon 9 mutations, although this was not statistically significant. Compared with previous studies in western populations, these results suggest that ethnic differences may influence the relationship between KIT genotype and clinical outcome to imatinib.

Hepatic resection for gastrointestinal stromal tumor liver metastases

Liver resection is the preferred treatment for gastrointestinal stromal tumor liver metastases (GIST LMs) when complete resection can be achieved. Major and extended hepatic resections can be safely performed, and using modern techniques, an increasing proportion of patients with GIST LMs are candidates for potentially curative therapy. The combination of tyrosine kinase inhibitor therapy (eg, imatinib) with surgery seems to improve outcome, and although prospective data are lacking, a short neoadjuvant course (6 months) of imatinib therapy followed by resection may improve patient selection for surgery and outcome from treatment. Postoperative therapy with imatinib is generally advised, although the duration of such therapy is not yet clearly defined. These questions may formulate the basis for future prospective studies of imatinib with complete resection of GIST LMs.

Decreased bone turnover despite persistent secondary hyperparathyroidism during prolonged treatment with imatinib

CONTEXT

The tyrosine kinase inhibitor imatinib mesylate has an established role in the management of a number of malignant and proliferative conditions. Cross-sectional and short-term prospective studies have demonstrated secondary hyperparathyroidism during imatinib therapy, and variable changes in markers of bone turnover.

OBJECTIVE

Our objective was to determine the biochemical and skeletal effects of imatinib during long-term therapy.

DESIGN

This was a 2-yr prospective study.

SETTING

The study was performed at an academic clinical research center.

PATIENTS OR OTHER PARTICIPANTS

Nine patients with bcr-abl positive chronic myeloid leukemia were included in the study.

INTERVENTIONS

Patients received Imatinib mesylate 400 mg/d.

MAIN OUTCOME MEASURES

Serum and urine biochemistry, markers of bone turnover, and bone mineral density were measured.

RESULTS

Participants developed mild secondary hyperparathyroidism, with significant decreases in serum calcium and phosphate (P < 0.05 and P < 0.0001 vs. baseline, respectively) and an increase in PTH (P < 0.0001 vs. baseline). Biochemical markers of bone turnover demonstrated a biphasic response, with an initial increase in markers of bone formation being followed by a decrease in markers of both formation and resorption. Bone density at the lumbar spine increased [mean (95% confidence interval) change from baseline 3.6% (1.6, 5.5); P = 0.003] as did that at the total body [1.4% (0.2, 2.5); P = 0.065], whereas that at the proximal femur did not change [-0.12% (-3.0, 2.7); P = 0.93]. Body weight and fat mass increased significantly (P < 0.0001 vs. baseline).

CONCLUSIONS

Long-term treatment with imatinib leads to persistent mild secondary hyperparathyroidism. Despite this, bone turnover is decreased, and bone density is stable or increased. Evaluation of the skeletal actions and safety of imatinib during longer-term therapy is warranted.

Aberrant activation of androgen receptor in a new neuropeptide-autocrine model of androgen-insensitive prostate cancer

Treatment of advanced prostate cancer with androgen deprivation therapy inevitably renders the tumors castration-resistant and incurable. Under these conditions, neuroendocrine differentiation of prostate cancer (CaP) cells is often detected and neuropeptides released by these cells may facilitate the development of androgen independence. Exemplified by gastrin-releasing peptide (GRP), these neuropeptides transmit their signals through G protein-coupled receptors, which are often overexpressed in prostate cancer, and aberrantly activate androgen receptor (AR) in the absence of androgen. We developed an autocrine neuropeptide model by overexpressing GRP in LNCaP cells and the resultant cell line, LNCaP-GRP, exhibited androgen-independent growth with enhanced motility in vitro. When orthotopically implanted in castrated nude mice, LNCaP-GRP produced aggressive tumors, which express GRP, prostate-specific antigen, and nuclear-localized AR. Chromatin immunoprecipitation studies of LNCaP-GRP clones suggest that GRP activates and recruits AR to the cognate promoter in the absence of androgen. A Src family kinase (SFK) inhibitor, AZD0530, inhibits androgen-independent growth and migration of the GRP-expressing cell lines, and blocks the nuclear translocation of AR, indicating the involvement of SFK in the aberrant activation of AR and demonstrating the potential use of SFK inhibitor in the treatment of castration-resistant CaP. In vivo studies have shown that AZD0530 profoundly inhibits tumor metastasis in severe combined immunodeficient mice implanted with GRP-autocrine LNCaP cells. This xenograft model shows autocrine, neuropeptide- and Src kinase-mediated progression of androgen-independent CaP postcastration, and is potentially useful for testing novel therapeutic agents.

[Not Available]

S. Taïeb, L. Ceugnart, F. Bonodeau, L. Vanseymortier, A. Adenis The management and the prognosis of gastrointestinal stromal tumors (GIST) have evolved rapidly with new targeted treatments. The aim of this paper is to assess the role of imaging not only for diagnosis but to quantify treatment response. RECIST criteria, which are the standard in assessment of post chemotherapy response in adult's solid tumors, can not be used in targeted therapy: the changes in lesion structures even if case of increasing volume are more specific to assess tumor response.

Phase II study of imatinib in patients with recurrent gliomas of various histologies: a European Organisation for Research and Treatment of Cancer Brain Tumor Group Study

PURPOSE

To evaluate the safety and the efficacy of imatinib in recurrent malignant gliomas.

PATIENTS AND METHODS

This was a single-arm, phase II study. Eligible patients had recurrent glioma after prior radiotherapy with an enhancing lesion on magnetic resonance imaging. Three different histologic groups were studied: glioblastomas (GBM), pure/mixed (anaplastic) oligodendrogliomas (OD), and low-grade or anaplastic astrocytomas (A). Imatinib was started at a dose of 600 mg/d with dose escalation to 800 mg in case of no toxicity; during the trial this dose was increased to 800 mg/d with escalation to 1,000 mg/d. Trial design was one-stage Fleming; both an objective response and 6 months of progression-free survival (PFS) were considered a successful outcome to treatment.

RESULTS

A total of 112 patients (51 patients with GBM, 25 patients with A, and 36 patients with OD) were enrolled. Imatinib was in general well tolerated. The median number of cycles was 2.0 (range, 1 to 43 cycles). Five patients had an objective partial response, including three patients with GBM; all had 6 months of PFS. The 6-month PFS rate was 16% (95% CI, 8.0% to 34.0%) in GBM, 4.0% (95% CI, 0.3% to 15.0%) in OD, and 9% (95% CI, 2.0% to 25.0%) in A. The exposure to imatinib was significantly lower in patients using enzyme-inducing antiepileptic drugs. The presence of ABCG2 point mutations were not correlated with pharmacokinetic findings. No somatic activating mutations of KIT or platelet-derived growth factor receptor-A or -B were found.

CONCLUSION

In the dose range of 600 to 1,000 mg/d, single-agent imatinib is well tolerated but has limited antitumor activity in patients with recurrent gliomas.

Expression of c-kit in fibroepithelial lesions of the breast is a mast cell phenomenon

The expression of c-kit, a protooncogene tyrosine kinase receptor (CD117), in phyllodes tumors of the breast has been the subject of recent investigations. We examined stromal c-kit expression by immunohistochemistry in 68 cases comprising fibroadenomas, fibroadenomas with cellular stroma, and benign, borderline, and malignant phyllodes tumors. Membrane staining was identified in the epithelium of 82% of cases, representing all diagnostic categories in the study. Membrane and cytoplasmic staining was detected in scant cells in the stroma in 74% of the cases in the study, again, across all diagnostic entities. However, when toluidine blue and tryptase staining was performed, the staining pattern matched that of c-kit in the number of cells and their distribution, thereby confirming the presence of mast cells and excluding any appreciable level of true stromal c-kit staining. One borderline and one malignant phyllodes tumor showed a diffuse weak stromal signal, which could not be accounted for by toluidine blue and tryptase. These cases were further tested for the presence of known activating mutations of c-kit and PDGFR-alpha, and yielded negative results. Our findings indicate that c-kit is an unlikely player in the pathogenesis of fibroepithelial lesions of the breast. The positive stromal staining suggested previously by other authors may be attributed to mast cells. C-kit, therefore, has neither a diagnostic nor a prognostic role in phyllodes tumors, and there is no rationale for the treatment of recurrent of malignant phyllodes tumor patients with tyrosine kinase inhibitors.

Distinct gene expression-defined classes of gastrointestinal stromal tumor

PURPOSE

The majority of gastrointestinal stromal tumors (GIST) can be cured by surgery alone, but relapse occurs in 20% to 40% of cases. GISTs are considered to invariably arise through gain of function KIT or PDGFA mutation of the interstitial cells of Cajal (ICC). However, the genetic basis of the malignant progression of GISTs are poorly understood.

PATIENTS AND METHODS

The expression levels of 54,613 probe sets in 32 surgical samples of untreated GISTs of the stomach and small intestine were analyzed with oligonucleotide microarrays. The representative GeneChip data were validated by real-time reverse transcriptase polymerase chain reaction and immunohistochemistry.

RESULTS

Unbiased hierarchical clustering consistently separated the 32 cases of GIST into two major classes according to tumor site. The two major classes were further separated into novel subclasses, which were significantly correlated with various pathological prognostic parameters, the frequency of metastasis (P < .05), and clinical outcome. Immunohistochemical analysis of 152 independent patients with gastric GISTs revealed that the expression of dipeptidyl peptidase IV (T-cell activation antigen CD26) protein was significantly associated with poorer overall and disease-free survival (P < .00001).

CONCLUSION

CD26 appears to be a reliable biomarker of malignant GISTs of the stomach. The postoperative recurrence rate of CD26-negative cases was as low as 2.0% (two of 102). Therefore, postoperative follow-up of such patients might be made less intensive. CD26 may play an important role in the malignant progression of gastric GISTs and serve as a therapeutic target.

Phase II, open-label study evaluating the activity of imatinib in treating life-threatening malignancies known to be associated with imatinib-sensitive tyrosine kinases

PURPOSE

To evaluate the activity of imatinib in treating advanced, life-threatening malignancies expressing one or more imatinib-sensitive tyrosine kinases.

EXPERIMENTAL DESIGN

This was a phase II, open-label, single arm study. Patients > or = 15 years old with malignancies showing histologic or molecular evidence of expression/activation of imatinib-sensitive tyrosine kinases were enrolled. Patients were treated with 400 or 800 mg/d imatinib for hematologic malignancy and solid tumors, respectively. Treatment was continued until disease progression or unacceptable toxicity. The primary objective was to identify evidence of imatinib activity with tumor response as the primary end point.

RESULTS

One hundred eighty-six patients with 40 different malignancies were enrolled (78.5% solid tumors, 21.5% hematologic malignancies). Confirmed response occurred in 8.9% of solid tumor patients (4 complete, 9 partial) and 27.5% of hematologic malignancy patients (8 complete, 3 partial). Notable activity of imatinib was observed in only five tumor types (aggressive fibromatosis, dermatofibrosarcoma protuberans, hypereosinophilic syndrome, myeloproliferative disorders, and systemic mastocytosis). A total of 106 tumors were screened for activating mutations: five KIT mutations and no platelet-derived growth factor receptor mutations were found. One patient with systemic mastocytosis and a partial response to therapy had a novel imatinib-sensitive KIT mutation (D816T). There was no clear relationship between expression or activation of wild-type imatinib-sensitive tyrosine kinases and clinical response.

CONCLUSION

Clinical benefit was largely confined to diseases with known genomic mechanisms of activation of imatinib target kinases. Our results indicate an important role for molecular characterization of tumors to identify patients likely to benefit from imatinib treatment.

Slug (SNAI2) down-regulation by RNA interference facilitates apoptosis and inhibits invasive growth in neuroblastoma preclinical models

PURPOSE

We assessed the relevance of Slug (SNAI2) for apoptosis resistance and invasion potential of neuroblastoma cells in vitro and in vivo.

EXPERIMENTAL DESIGN

We evaluated the effect of imatinib mesylate on invasion and analyzed the genes modulated by imatinib mesylate treatment in neuroblastoma cells. Slug expression, inhibited by imatinib mesylate treatment, was knocked down in neuroblastoma cells by RNA interference, and the effects on invasion and apoptosis were evaluated in vitro. A pseudometastatic model of neuroblastoma in severe combined immunodeficient mice was used to assess the effects of Slug silencing alone or in combination with imatinib mesylate treatment on metastasis development.

RESULTS

Microarray analysis revealed that several genes, including Slug, were down-regulated by imatinib mesylate. Slug expression was detectable in 8 of 10 human neuroblastoma cell lines. Two Slug-expressing cell lines were infected with a vector encoding a microRNA to Slug mRNA. Infected cells with reduced levels of Slug were tested for the expression of apoptosis-related genes (p53, Bax, and Bcl-2) identified previously as Slug targets. Bcl-2 was down-regulated in Slug-interfered cells. Slug down-regulation increased sensitivity to apoptosis induced by imatinib mesylate, etoposide, or doxorubicin. Invasion of Slug-silenced cells was reduced in vitro. Animals injected with Slug-silenced cells had fewer tumors than controls and the inhibition of tumor growth was even higher in animals treated with imatinib mesylate.

CONCLUSIONS

Slug down-regulation facilitates apoptosis induced by proapoptotic drugs in neuroblastoma cells and decreases their invasion capability in vitro and in vivo. Slug inhibition, possibly combined with imatinib mesylate, may represent a novel strategy for treatment of metastatic neuroblastoma.

Surgical intervention following imatinib treatment in patients with advanced gastrointestinal stromal tumors (GISTs)

BACKGROUND

We investigated the role of surgical intervention for advanced GIST after imatinib.

METHODS

Among 256 patients treated with imatinib for advanced GIST, the medical records of the 34 patients who underwent surgery of residual tumors after imatinib treatment were reviewed.

RESULTS

Surgery was performed on 24 patients with responsive disease (RD) after imatinib, on 3 with focal progressive disease (FP), and on 7 with generalized progressive disease (GP). All gross tumors were completely resected in 19/24 (79%), 1/3 (33%), and 1/7 (14%) patients, respectively. Disease status at surgery was associated with prognosis after surgery; with a median follow-up of 25.7 months, the median progression-free survival of patients resected for RD, FP, and GP were 27.8 months (95% CI, 17.8-37.8 months), 5.1 months (95% CI, 4.7-5.6 months), and 3.3 months (95% CI, 2.7-3.9 months), respectively (P < 0.001). Median overall survival was not reached in patients resected for RD, and was 22.5 months (95% CI, 1.4-43.0 months) and 23.5 months (95% CI, 3.0-43.9) for patients resected for FP and GP, respectively (P < 0.001).

CONCLUSION

Surgical resection of tumors responsive to imatinib may be beneficial in patients with advanced GIST. Debulking surgery, however, is not recommended for patients who have already developed imatinib resistance.

Phase II trial of imatinib mesylate in patients with metastatic melanoma

Metastatic melanoma cells express a number of protein tyrosine kinases (PTKs) that are considered to be targets for imatinib. We conducted a phase II trial of imatinib in patients with metastatic melanoma expressing at least one of these PTKs. Twenty-one patients whose tumours expressed at least one PTK (c-kit, platelet-derived growth factor receptors, c-abl, or abl-related gene) were treated with 400 mg of imatinib twice daily. One patient with metastatic acral lentiginous melanoma, containing the highest c-kit expression among all patients, had dramatic improvement on positron emission tomographic scan at 6 weeks and had a partial response lasting 12.8 months. The responder had a substantial increase in tumour and endothelial cell apoptosis at 2 weeks of treatment. Imatinib was fairly well tolerated: no patient required treatment discontinuation because of toxicity. Fatigue and oedema were the only grade 3 or 4 toxicities that occurred in more than 10% of the patients. Imatinib at the studied dose had minimal clinical efficacy as a single-agent therapy for metastatic melanoma. However, based on the characteristics of the responding tumour in our study, clinical activity of imatinib, specifically in patients with melanoma with certain c-kit aberrations, should be examined.

Somatic pharmacogenomics in cancer

Many of the initial examples of the clinical utility of pharmacogenetics were elucidated in the field of oncology. Those examples were largely based on the existence of germline genetic variation that influences the metabolism of cytotoxic drugs. However, with the development of kinase inhibitors, drugs designed to preferentially target altered proteins driving oncogenesis, pharmacogenetics in cancer has shifted to understanding the somatic differences that determine response to these targeted agents. It is becoming increasingly clear that understanding the molecular genetics of cancer will lead to the further development of targeted therapeutics. Therefore, it is imperative that pharmacogenomics researchers understand the motivations and challenges of developing targeted therapies to treat cancer as a paradigm for personalized medicine. However, much of the discussion in the pharmacogenomics community in cancer is still largely focused on the germline variants as predictors of drug toxicity. In light of that fact, this review presents a detailed discussion of the development of commonly used targeted therapies for the treatment of hematological and solid tumors, the somatic mutations that determine response to those therapies, and the mechanisms of drug resistance.