Sorafenib in patients with metastatic gastrointestinal stromal tumors who failed two or more prior tyrosine kinase inhibitors: a phase II study of Korean gastrointestinal stromal tumors study group

PURPOSE

To evaluated the efficacy and safety of sorafenib in patients with advanced gastrointestinal stromal tumors (GIST) who failed to previous standard treatments.

EXPERIMENTAL DESIGN

Thirty-one patients with measurable metastatic GIST who failed both imatinib and sunitinib were accrued. Sorafenib was administered orally at 400 mg twice daily until disease progression or development of intolerance. The primary endpoint was disease control rate (response + stable disease, DCR) at 24 weeks.

RESULTS

Sorafenib was well tolerated, with hand-foot skin reaction, fatigue, hypertension, and abdominal pain being the most frequent adverse events. The relative dose intensity of sorafenib during the first 6 months was >80%. Four patients achieved partial response (response rate 13%, 95% CI 1-25%), and 16 (52%) had stable disease. DCR at 24 weeks was measured as 36% (95% CI 19-52%). Median progression-free and overall survivals were 4.9 and 9.7 months, respectively. Progression-free survival of patients with prior use of nilotinib (P = .0085) and with primary genotypes other than KIT exon 11 mutation (P = .0341) was significantly shorter than that of patients without.

CONCLUSIONS

Sorafenib showed antitumor activity in this population of imatinib and sunitinib pretreated GIST. With sorafenib, about one third of patients can maintain disease control for more than 24 weeks.

Synchronous gastrointestinal stromal tumor and primary lung adenocarcinoma

Although rare, gastrointestinal stromal tumors (GIST) are the most common mesenchymal tumors of the gastrointestinal tract. The asynchronous occurrence of other malignancies in patients with GIST during the clinical course is relatively common. However, the synchronous coexistence of GIST and lung cancer has only rarely been reported. We experienced a case of coincidental primary lung adenocarcinoma and intestinal GIST. The present case is not only of interest due to the rare coincidence of GIST and lung cancer, but also because there was an epidermal growth factor receptor gene mutation in the lung cancer and a c-kit mutation in the GIST.

GIST in Saudi Arabia: multicentric histopathological genetic study of 75 surgically excised cases

The availability of CD117 (Ckit) immunohistochemical testing in most hospital laboratories has facilitated the diagnosis of GIST in cKit positive cases. The aim of this study was to describe the histopathological variations of GIST in Saudi Arabia. The study involved analysis of paraffin blocks of 75 surgically excised GIST and GIST-like stromal tumors obtained from four major referral hospitals in Saudi Arabia (Riyadh Military Hospital, King Abdulaziz Medical City, King Faisal Specialist Hospital & Research Center and Aramco's hospital) between 1998 and 2009. Patient sex and age were noted in addition to the following tumor variables: size, site, histological grade and type, immunohistochemical profile and genetic analysis of the cKit mutation. The stomach was the commonest site for tumors and spindle cell type was the most frequently seen variant. Further sub classification of the histopathological type was made in order to recognize the morphological pattern of the tumor. The most common tumor grades seen were of low-risk and high-risk groups. There was one case of familial GISTparaganglioma syndrome and the youngest subject was an 8-year-old girl with high-risk spindle cell gastric GIST. Genetic study in 34 cases revealed exon 11 mutations in all of the cKit genes.

Gastrointestinal stromal tumors

INTRODUCTION

The gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor of the intestinal tract, known to be refractory to conventional chemotherapy or radiation. Its pathogenesis is defined by mutations within the KIT and PDGFRA gene, which constitutively activate KIT and PDGFRA oncoproteins, and serve as crucial diagnostic and therapeutic targets.

DISCUSSION

Besides surgery, therapy with imatinib mesylate, which inhibits KIT kinase activity, represents the other cornerstone for the treatment of GIST. Still, the only curative option for GIST is given after complete surgical removal even in a metastatic setting, but recurrence is common, and the risk can be defined by surgical factors like incomplete resection, intraperitoneal rupture, or bleeding and tumor associated factors like tumor size, mitotic index, or localization.

CONCLUSION

Consequently, adjuvant therapy with imatinib mesylate or other tyrosine kinase inhibitors is recommended for high-risk patients after complete resection. For unresectable and advanced GIST, a partial response or stable disease can be achieved in about 80% of patients with imatinib mesylate.

Gastrointestinal stromal tumors: diagnosis and treatment

BACKGROUND

Gastrointestinal stromal tumors (GIST) are the most common mesenchymal neoplasms of the digestive tract. They originate from the interstitial cells of Cajal and are characterized by the overexpression of KIT protein (tyrosine kinase). Their prognosis has improved significantly with the discovery of imatinib mesylate for advanced GIST treatment.

METHODS

We carried out a retrospective, descriptive study of GISTs diagnosed in our center during the past 5 years. We excluded patients with incidental diagnoses in the context of other pathologies because GIST did not affect outcome or prognosis. The variables studied were clinical characteristics, location, size, imaging techniques, resectability, neoadjuvant imatinib, surgical technique, histology, immunohistochemistry, prognostic classification of Fletcher, morbidity, monitoring, and disease-free and overall survival.

RESULTS

Nineteen patients were diagnosed (14 males/5 females) with a mean age of 63 years (range: 30-84 years). Diagnosis was incidental in eight patients (42%). Tumor location of the remaining 11 patients (58%) was six tumors of the small intestine (55%), four gastric (36%) and one rectal (9%). Predominant gastrointestinal bleeding and anemia were diagnosed mainly by abdominal computed tomography (CT). At diagnosis, nine patients were considered resectable with radical intent (82%) and the other two patients (18%) received neoadjuvant treatment with a favorable response after 6 months. Three patients were treated with imatinib after surgery (33%). Median survival was 34 months (range: 5-58 months).

CONCLUSIONS

Diagnosis of GIST is often incidental. The predominant clinical symptom is usually gastrointestinal bleeding and anemia and the most widely used imaging test is CT. Treatment is surgical unless advanced GIST is diagnosed, which will be treated with imatinib mesylate neoadjuvant therapy. A multidisciplinary approach to this pathology is essential, a fact that affects prognosis and patient survival.

Mitotic checkpoints and chromosome instability are strong predictors of clinical outcome in gastrointestinal stromal tumors

PURPOSE

The importance of KIT and PDGFRA mutations in the oncogenesis of gastrointestinal stromal tumors (GIST) is well established, but the genetic basis of GIST metastasis is poorly understood. We recently published a 67 gene expression prognostic signature related to genome complexity (CINSARC for Complexity INdex in SARComas) and asked whether it could predict outcome in GISTs.

EXPERIMENTAL DESIGN

We carried out genome and expression profiling on 67 primary untreated GISTs.

RESULTS

We show and validate here that it can predict metastasis in a new data set of 67 primary untreated GISTs. The gene whose expression was most strongly associated with metastasis was AURKA, but the AURKA locus was not amplified. Instead, we identified deletion of the p16 (CDKN2A) and retinoblastoma (RB1) genes as likely causal events leading to increased AURKA and CINSARC gene expression, to chromosome rearrangement, and ultimately to metastasis. On the basis of these findings, we established a Genomic Index that integrates the number and type of DNA copy number alterations. This index is a strong prognostic factor in GISTs. We show that CINSARC class, AURKA expression, and Genomic Index all outperform the Armed Forces Institute of Pathology (AFIP) grading system in determining the prognosis of patients with GISTs. Interestingly, these signatures can identify poor prognosis patients in the group classified as intermediate-risk by the AFIP classification.

CONCLUSIONS

We propose that a high Genomic Index determined by comparative genomic hybridization from formalin-fixed, paraffin-embedded samples could be used to identify AFIP intermediate-risk patients who would benefit from imatinib therapy.

Gastrointestinal stromal tumours: origin and molecular oncology

Gastrointestinal stromal tumours (GISTs) are a paradigm for the development of personalized treatment for cancer patients. The nearly simultaneous discovery of a biomarker that is reflective of their origin and the presence of gain-of-function kinase mutations in these tumours set the stage for more accurate diagnosis and the development of kinase inhibitor therapy. Subsequent studies of genotype and phenotype have led to a molecular classification of GIST and to treatment optimization on the basis of molecular subtype. The study of drug-resistant tumours has advanced our understanding of kinase biology, enabling the development of novel kinase inhibitors. Further improvements in GIST treatment may require targeting GIST stem cell populations and/or additional genomic events.

Succinate dehydrogenase-deficient GISTs: a clinicopathologic, immunohistochemical, and molecular genetic study of 66 gastric GISTs with predilection to young age

Most gastrointestinal stromal tumors (GISTs) are driven by KIT or PDGFRA-activating mutations, but a small subset is associated with loss of function of the succinate dehydrogenase (SDH) complex of mitochondrial inner membrane proteins. This occurs by germline mutations of the SDH subunit genes and hitherto unknown mechanisms. SDH-deficient GISTs especially include pediatric GISTs and those associated with Carney triad (CT) or Carney-Stratakis syndromes (CSSs); the latter 2 also include paraganglioma as a component. SDH-deficient GISTs were identified in this study on the basis of immunohistochemical loss of succinate dehydrogenase subunit B (SDHB), which signals functional loss of the SDH complex. We found 66 SDH-deficient GISTs among 756 gastric GISTs, with an estimated frequency of 7.5% of unselected cases. Nearly, all gastric GISTs in patients <20 years, and a substantial percentage of those in patients <40 years, but only rare GISTs in older adults were SDH deficient. There was a female predominance of over 2:1. Two patients each had either pulmonary chondroma or paraganglioma (CT), but none of the examined cases had SDH germline mutations (CSS) or somatic KIT/PDGFRA or BRAF mutations. SDH-deficient GISTs were often multiple and typically showed plexiform muscularis propria involvement and epithelioid hypercellular morphology. They were consistently KIT-positive and DOG1/Ano 1-positive and almost always smooth muscle actin negative. Tumor size and mitotic activity varied, and the tumors were somewhat unpredictable with low mitotic rates developing metastases. Gastric recurrences occurred in 11 patients, and peritoneal and liver metastases occurred in 8 and 10 patients, respectively. Lymph node metastases were detected in 5 patients, but lymphovascular invasion was present in >50% of cases studied; these 2 were not related to adverse outcome. Seven patients died of disease, but many had long survivals, even with peritoneal or liver metastases. All 378 nongastric GISTs and 34 gastric non-GIST mesenchymal tumors were SDHB positive. SDH-deficient GISTs constitute a small subgroup of gastric GISTs; they usually occur in children and young adults, often have a chronic course similar to that of pediatric and CT GISTs, and have potential association with paraganglioma, necessitating long-term follow-up.

[A case report of huge abdominal recurrent tumor of small intestinal GIST after 15 years from the operation with primary lesion]

A man in his 60s was given an emergency operation 15 years ago for abdominal bleeding. His tumor of small intestine was resected and diagnosed as small intestinal leiomyosarcoma. He came to our hospital because of his abdominal masses 15 years after the initial operation. CT scan showed a 15 cm-sized solid and cystic tumor in the pelvic cavity. The tumor was diagnosed as GIST by PET-CT and MRI. The tumor was resected, and pathological findings led to the diagnosis of GIST with this tumor. Previous tumor cells were slightly-positive for kit immunohistological examination, but did not resemble this tumor cells morphologically. So genetic tests were performed and revealed two tumors had same mutations of c- kit. Finally, we could diagnose the tumor was recurrent metastases of small intestinal GIST 15 years after the initial surgery. kit mutation analysis was useful for a diagnosis of recurrences and predictions of the clinical response to imatinib in GISTs.

Cathepsin L is highly expressed in gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract that are diagnosed by c-kit staining in most cases. A lysosomal cysteine proteinase termed cathepsin L has been commonly associated with malignancy in several cancer types, but this finding has not been reported for GISTs. We analyzed the cathepsin L mRNA and protein expression in GISTs. Real-time reverse transcription polymerase chain reaction (RT-PCR) analysis revealed that cathepsin L levels were higher in GISTs than those in gastric or colorectal tumors; this finding was supported by results of the Western blot analysis. Immunohistochemistry revealed that cathepsin L was localized to the cytoplasm of GIST cells as an intense granular signal, which was not observed in the cells of leiomyoma, a mesenchymal tumor that was analyzed as a control specimen. Double immunofluorescence microscopy revealed that a portion of the granular signal colocalized with lysosome-associated membrane protein-1 (LAMP-1), which is a lysosomal marker. Moreover, immunohistochemical analysis of 43 tumor specimens revealed that 86.0% (n=37) were cathepsin-L positive, and this positivity was significantly correlated with c-kit positivity but not with other clinicopathological factors, including gender, age, region, size, mitosis and risk of recurrence. From these results, we conclude that cathepsin L is highly expressed in GISTs compared to its expression in other cancerous lesions; this identifies cathepsin-L as a new diagnostic marker for GISTs.

[Morphological characteristics and prognostic criteria for gastrointestinal stromal tumors]

Gastrointestinal stromal tumors (GIST) are the most common mesenchymal neoplasms of the gastrointestinal tract. Analysis of GIST morphology is necessary for selection of primary patients with the high risk of tumor progression for adjuvant treatment with gleevek following complete gross resection of KIT (CD 117)-positive GIST. In this study we've analyzed morphological parameters and survival of 120 GIST patients before target therapy. According to risk stratification of primary GIST by tumor location, size and mitotic index (mitoses per 50 visual fields) 44% of gastric GISTs, 87,5% of small bowel GISTs and 100% of rectum GISTs have been classified as high risk group. There was no significant difference between survival of patients with different type of GIST, Ki-67 proliferative index and presence of necrosis.

Exon 11 mutations, Ki67, and p16(INK4A) as predictors of prognosis in patients with GIST

Prognostic biomarkers for GIST are under investigation. The aim of this study was to assess whether exon 11 mutations, Ki67, and p16(INK4A) are predictors of prognosis in GIST. Consecutive GIST cases (n=84) had their specimens evaluated for exon 11 mutations and expression of Ki67 and p16(INK4A). Surgical cases were categorized according to NIH and Miettinen's classification, and survival was analyzed from hospital database. GISTs were predominately gastric (45%) and with spindle cell morphology (74%). The risk category was very low or low in 28%, intermediate in 23%, and high in 49%. Exon 11 mutation was identified in 29 (48%) out of 60 cases studied. There were 12 point mutations, 10 deletions, 4 duplications, and 3 double mutations. A third of GISTs had either high Ki67 index (>3%) or negativity for p16(INK4A). In multivariate analysis, independent predictors of mortality were Ki67>3% (HR=7.3; P=0.036) and high mitotic index (HR=10.4; P=0.043). There was no association between exon 11 mutations and survival. This study suggests that Ki67>3% is an independent predictor of poor prognosis in patients with GIST. Exon 11 mutations and negativity for p16(INK4A) need further studies to address the prognostic value.

[Gastrointestinal stromal tumor molecular diagnostics in relation to the prediction of a therapeutic response to targeted biological therapy]

Targeted therapy based on the inhibition of the receptor tyrosine kinases has improved the outcome of patients with metastatic, recurrent and/or unresectable gastrointestinal stromal tumors (GIST). Activating mutations of KITand PDGFRA genes, which code for receptor tyrosine kinases, play an important role in the malignant transformation of stromal cells in the gastrointestinal tract. The response to targeted therapy is associated with the presence and type of mutations. Molecular identification of the primary mutational status became an important tool in predicting the response to therapy (sensibility/resistance). The identification of secondary mutations occurring in patients treated with targeted therapy may explain the cause of acquired, secondary resistance of GIST. In these cases, mutational analysis represents a tool to explain failure of the therapy and provides a rationale for alternative therapeutic strategies.

VEGF expression is related to good response and long progression-free survival in gastrointestinal stromal tumor patients treated with Sunitinib

We intended to find predictive markers in advanced gastrointestinal stromal tumor patients treated with sunitinib. Korean patients who received sunitinib after imatinib failure for advanced gastrointestinal stromal tumor were studied. Genotyping for KIT and PDGFRA were performed. An immunohistochemical stain for PDGFR-α, PDGFR-β, and vascular endothelial growth factor (VEGF) was performed. A total of 22 patients were analyzed. Their median age was 55.1 years, and the male to female ratio was 12:10. The response rate of sunitinib was 30.4% and the median progression-free survival (PFS) was 10.1 months. In the sunitinib treatment, VEGF expression was related to a favorable response (P=0.002) and long PFS (P=0.020) in univariate analysis. CD34 (P=0.023) and PDGFR (P=0.022) expressions were also related to long sunitinib PFS in univariate analysis. However, the genotype did not affect either response rate or the PFS of sunitinib. In conclusion, expressions of VEGF, PDGFR, and CD34 may have predictive value in sunitinib treatments.

Evaluation of prognostic factors and their capacity to predict biological behavior in gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are c-KIT-signaling-driven mesenchymal tumors of the human digestive tract, many of which have c-KIT or PDGFRα activating mutations. The authors studied the immunohistochemical markers, c-KIT and PDGFRα mutations, in GISTs and their association with the clinicopathological and clinical follow-up in 145 GISTs. Tumors were located mainly in the stomach, the median tumor size being 7.5 cm. The mitotic index was ≤5 mitoses per 50 high-power fields in 61% of cases, 96% expressed CD117, and c-KIT or PDGFRα mutations were detected in 68% of cases. The median follow-up of the series was 52 months (range = 1 to 244.9 months). Tumor size, cell morphology, mitotic index, incomplete resection, Fletcher's risk classification, Ki-67 overexpression, and c-KIT mutations were associated with progression-free survival. Incomplete resection and mitotic activity also provide information about overall survival. In conclusion, complete clinicopathological, immunohistochemical, and genetic descriptions are necessary to characterize this disease and optimize its clinical management.

Abnormal elevated PTEN expression in the mouse antrum of a model of GIST Kit(K641E/K641E)

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. Approximately 85% of GISTs harbor activating mutations of the KIT or PDGFRA receptor tyrosine kinases. PTEN and SHIP2 are major phosphatases that dephosphorylate PI(3,4,5)P(3), one of the intracellular signal pathways downstream of KIT. PTEN is an important tumor suppressor, whereas the involvement of SHIP2 in cancer has been proposed based essentially on cell line studies. We have used a mouse model of GIST, i.e. Kit(K641E) knock-in mice, resulting in the substitution of a Lys by Glu at position 641 of Kit. In homozygous Kit(K641E) mice, PTEN-immunoreactivity (ir) in antrum was found in the hyperplastic Kit-ir layer. The same localization was found for SHIP2. Western blot analysis in antrum showed a large increase in PTEN expression in Kit(K641E) homozygous mice as compared to wild type. In contrast, SHIP2 expression was not affected between the two genotypes. Erk1, but not PKB, phosphorylation appears to be upregulated in Kit(K641E) homozygous mice. In the human GIST882 imatinib sensitive cell line, both PTEN and SHIP2 were expressed and showed, in part, a nuclear localization. The upregulation of PTEN in antrum in Kit(K641E) mice might serve as a feedback mechanism to limit PI 3-kinase activation downstream of Kit in a context of oncogenic mutation.

The GIST paradigm: how to establish diagnostic and prognostic criteria

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract. The present review evaluates the most important parameters in GIST: epidemiology, principal clinical presentations, histopathological patterns of GIST with differential diagnosis and Fletcher's and Miettinen's risk classification, immunohistochemistry, prognostic factors, c-KIT and PDGFRalpha mutations and treatment of this tumor. The most frequent site for GISTs is the stomach, followed by the duodenum and small intestine; spindle cell morphology is described in 70% with CD17 positivity in around 95% of the cases; exon 11 of c-KIT is the most mutated, with Gleevec being the principal treatment. In GISTs, high mitotic rate, large tumor size, incomplete resection, extragastrointestinal site, duplication 502-503 in exon 9 of c-KIT, and secondary mutations are negative prognostic factors.

Effective salvage therapy of imatinib-resistant gastrointestinal stromal tumor with combination of imatinib and pegylated liposomal doxorubicin

Here we presented a 60-year-old Taiwanese man with advanced gastrointestinal stromal tumor. Disease progression was noted during imatinib treatment. Surgical resection was done and mutation analysis of KIT gene in all the resected tumors revealed deletion mutations of codons 558-565 in exon 11, whereas a missense mutation was also identified at codon 822 in exon 17 in one resected tumor. Patient's disease was refractory to escalating dose of imatinib and dasatinb. Surprisingly, combination of imatinib with pegylated liposomal doxorubicin produced a substantial response and resulted in a 5-month progression free period for this imatinib-resistant gastrointestinal stromal tumor.

Prognostic determinants in epithelioid sarcoma

BACKGROUND

Epithelioid sarcoma (ES) is a rare soft tissue neoplasm that usually arises in the distal extremities of young adults, presents a high rate of recurrences and metastases and frequently poses diagnostic dilemmas. In order to identify markers useful for patient stratification purposes, we investigated the prognostic impact of clinical and molecular patient characteristics, including the status of SMARCB1 tumour suppressor gene, in a consecutive series of ES cases.

METHODS

Kaplan-Meier survival curves were compared by the log-rank test. Immunophenotyping and SMARCB1 protein expression were analysed by immunohistochemistry or western blotting in 40 ES patients for which tumour material was available. Cases lacking SMARCB1 protein expression were investigated for the presence of gene mutations and gene deletions by exon sequencing, fluorescent in situ hybridization and quantitative PCR.

RESULTS

FNCLCC tumour grade 3 and proximal-type histology significantly correlated with shorter overall survival (log-rank p=0.0046 and p=0.0001, respectively). We identified loss of SMARCB1 protein expression in the majority of ES cases (25/40, 62.5%), including 24/34 (71%) adult cases but only 1/6 (17%) paediatric/adolescent cases (p=0.02, two-tailed Fisher's exact test). The absence of protein is strongly correlated with SMARCB1 gene deletion (p=0.003, two-tailed Fisher's exact test). We observed a trend towards the correlation between SMARCB1 inactivation and both higher tumour grading and a clinical course of the disease characterised by the occurrence of multiple relapses/metastasis.

CONCLUSION

These data show that both tumour grading and subtype are prognostic factors in ES. Loss of SMARCB1 protein expression in ES is a frequent occurrence mediated by gene deletion events, thus pointing to a crucial role of SMARCB1 in ES genesis. Analysis of SMARCB1 status in ES warrants prospective investigation as a prognostic marker and therapeutic target.

[Clinicopathologic features and immunophenotypes of CD117-negative gastrointestinal stromal tumor]

OBJECTIVE

To study the immunophenotype and c-kit or platelet derived growth factor receptor alpha (PDGFRA) gene mutations in CD117-negative gastrointestinal stromal tumors (GISTs).

METHODS

Ten cases of GISTs with typical histologic features but no CD117 expression were retrieved from the archival of Department of Pathology, Peking Union Medical College Hospital, China. The cases were further evaluated for the presence of c-kit exons 9, 11, 13 and 17 mutations and PDGFRA exons 12 and 18 mutations. DNA was extracted from the paraffin-embedded tumor tissue. The PCR products were sequenced directly for the mutations. An immunohistochemical study for CD117, CD34, smooth muscle actin, desmin, S-100 protein, WT-1 and DOG-1 was also performed.

RESULTS

Eight of the 10 cases had the mutation tests completed. C-kit mutation in exon 9 was detected in only one case. Amongst the 10 cases studied, CD34 was expressed in 9 cases. Smooth muscle actin was focally positive in 2 cases. None of them expressed desmin or S-100 protein. DOG-1 and WT-1 were diffusely positive in 5 and 4 cases, respectively. In addition, DOG1 was diffusely but weakly positive in 1 case and focally expressed in 2 cases. Three cases were focally positive for WT-1.

CONCLUSION

Pathologic diagnosis of CD117-negative GISTs can be facilitated with the application of a panel of immunohistochemical markers, including DOG-1 and WT-1.

[Clinicopathological and molecular features of the gastrointestinal stromal tumor]

Gastrointestinal stromal tumor (GIST)is a serious and predominantly sporadic tumor of the gastrointestinal tract (GIT). We attempted to review clinicopathological and molecular findings of GIST. GIST recently has been suggested to originate from the multipotential mesenchymal stem cells. Histologically, GIST is classified into spindle, epithelioid and mixed types. Tumor size, mitotic index, anatomic location and tumor rupture are the characteristics used to predict the clinical prognosis of patients. Expressions of c-kit/PDGFRA are essential for diagnosing GISTs. Activated mutant c-kit or platelet-derived growth factor receptor alpha (PDGFRA), which are potential therapeutic targets for imatinib, are constitutively expressed in most GIST. Imatinib selectively inhibits several protein tyrosine kinases and is an effective drug in malignant GISTs. More recently, sunitinib, a new KIT/PDGFRA kinase inhibitor, has been tested in patients with GIST resistant to imatinib with promising results.

[Standardization of evaluation for target molecule in cancer therapy]

The individualized-therapy for the gastrointestinal tract cancer is started by the emergence of molecular targeted-therapy. The patients' selection for treatment is now performed by evaluating the expression level of the targeted molecules and/or the gene mutation analysis using the pathological specimens. Pathologists should make diagnosis and select patients for the fittest molecular targeted therapy in colon cancer, stomach cancer and gastrointestinal stromal tumor(GIST). In the present paper, we focused and discussed the points of the evaluation of the targeted-molecule in pathological materials for selecting patients using the examples of HER2 test in gastric cancer and K-RAS muation in colon cancer.

[GIST refractory to imatinib treatment]

After the introduction of imatinib, the outcome for patients with advanced gastro-intestinal stromal tumor (GIST) was vastly improved. However, resistance to imatinib has become a new problem. The cause of resistance to imatinib is the low sensitivity of gene mutations in the KIT gene or PDGFRα, or an acquisition of additional mutations, and a low plasma level of imatinib. Sunitinib is the first drug that showed an effectiveness for treating GIST refractory to imatinib. New molecular target drugs for overcoming imatinib resistance are being developed now.