Tumor mitotic rate, size, and location independently predict recurrence after resection of primary gastrointestinal stromal tumor (GIST)

Effectiveness of adjuvant imatinib in patients with gastrointestinal stromal tumor: results of a population-based, matched-cohort study

OBJECTIVE

Data are limited on the use of adjuvant imatinib in patients with gastrointestinal stromal tumor (GIST) outside of clinical trials. This retrospective, population-based, matched-cohort study evaluated adjuvant imatinib treatment patterns, assessed impact on clinical outcomes, and estimated effectiveness based on number needed to treat (NNT).

RESEARCH DESIGN AND METHODS

GIST-related claims from the PharMetrics claims database were included (2000-2010). A stepwise identification algorithm identified appropriate patients based on GIST-related ICD-9-CM codes, who were classified as 'imatinib (IM) patients' receiving imatinib within 84 days post-surgery and 'non-imatinib (non-IM) patients' undergoing surgery but not receiving imatinib during the study period. The primary composite outcome was based on incidence of a second GIST-related surgery and long-term follow-up in the matched cohorts. IM patients were matched with up to eight non-IM patients on age, gender, ICD-9-CM code, and first surgery date.

RESULTS

A total of 118 IM and 4088 non-IM patients with possible GIST ICD-9s and surgery were included. The median duration between first and second surgeries was significantly longer in IM than non-IM patients (488 vs. 290 days; p = 0.0005). IM patients also had longer median follow-up from initial surgery to composite outcome (433 vs. 320 days; p = 0.002). Adherence to IM, measured by medication possession ratio, was 0.83 and 0.73 during the first and second years of treatment, respectively. IM patients were less likely to have the composite outcome compared with non-IM patients (hazard ratio = 0.501; p = 0.0005). The NNT to prevent one outcome was 4.

CONCLUSIONS

Patients receiving adjuvant imatinib treatment were less likely to have second surgery or be lost to follow-up, and had a longer interval to second surgery. Although treatment with adjuvant imatinib in patients with primary GIST is effective, adherence to imatinib and treatment duration are less than recommended by current treatment guidelines.

Adjuvant treatment of GIST: patient selection and treatment strategies

Tyrosine kinase inhibitors that target the key molecular drivers of gastrointestinal stromal tumour (GIST) are effective treatments of advanced-stage GIST. Yet, most of these patients succumb to the disease. Approximately 60% of patients with GIST are cured by surgery, and these individuals can be identified by risk stratification schemes based on tumour size, mitosis count and site, and assessment of rupture. Two large randomized trials have evaluated imatinib as adjuvant treatment for operable, KIT-positive GIST; adjuvant imatinib substantially improved time to recurrence. One of these trials reported that 3 years of adjuvant imatinib improves overall survival of patients who have a high estimated risk for recurrence of GIST compared with 1 year of imatinib. The optimal adjuvant strategy remains unknown and some patients might benefit from longer than 3 years of imatinib treatment. However, a strategy that involves GIST risk assessment following surgery using a validated scheme, administration of adjuvant imatinib for 3 years, patient monitoring during and after completion of imatinib to detect recurrence early, and reinstitution of imatinib if GIST recurs is a reasonable choice for care of patients with high-risk GIST.

Updates on the management of gastrointestinal stromal tumors

Despite being the most common sarcoma of the gastrointestinal tract, gastrointestinal stromal tumor (GIST) has been widely recognized as a unique entity for just over a decade. The advent of tyrosine kinase inhibitors has revolutionized the diagnosis and treatment of GIST. Although surgery remains the only chance for cure, multimodal treatment that includes molecular therapy continues to develop. Optimal management of GIST requires careful radiographic, pathologic, medical, and surgical care, emphasizing the need for a multidisciplinary approach. This review highlights recent developments in the management of GIST.

Five-year follow up of patients with gastrointestinal stromal tumor: recurrence-free survival by risk group

AIM

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor of the gastrointestinal tract. There is limited published data on GIST from the Indian subcontinent. This 5-year retrospective analysis of 49 patients treated for GIST reports clinical and pathological features and survival outcome by risk stratification.

METHODS

We reviewed 49 cases of GIST from January 2004 to December 2008. Imatinib was administered after surgery in patients with either high-risk, residual or metastatic disease and at onset of recurrence or metastatic disease in patients with intermediate risk.

RESULTS

The mean age was 50 years (range, 17-80 years). Patients with localized tumor were classified as low (n = 2), intermediate (n = 4) and high risk (n = 32), based on the primary tumor and mitotic index. At a median follow up of 21 months, 2-year and 3-year recurrence or progression-free survival rates were 61 and 39%, respectively, for all patients. The median recurrence-free survival rate in the intermediate-risk and high-risk groups were 7 and 49 months, respectively. The median progression-free survival in the residual (n = 4) and metastatic disease group (n = 7) was 10 and 29 months, respectively.

CONCLUSION

This study demonstrates the role of imatinib in adjuvant and therapeutic settings. Responses have been durable and most patients tolerate the drug well at clinically effective doses. In view of high recurrence rates in the intermediate-risk group in our study, it would be better to keep these patients on strict follow up to detect recurrence at the earliest opportunity.

Clinical and pathological features of gastrointestinal stromal tumors: an analysis of 138 cases

AIM: To explore the clinical, pathologic and immunohistochemical characteristics of gastrointestinal stromal tumors (GISTs).

METHODS: The clinical, surgical, immunohistochemical and pathologic data for 138 patients with GISTs were retrospectively analyzed. The expression of CD117, CD34, SMA, Desmin and S-100 was detected using the Envision immunohistochemical method.

RESULTS: The lesion was located in the stomach in 90 cases (65.22%), in the small intestine in 36 cases (26.09%), in the colorectum in 9 cases (6.52%), and in the retroperitoneum in 3 cases (2.17%). Of 138 cases, 114 were detected as spindle type, 6 as epithelioid type, 18 as mixture type; 99 had mitotic figures ≤5/50 HPF, 24 had mitotic figures 5-10/50 HPF, 15 had mitotic figures >10/50 HPF; 97.38% were positive for CD117, 73.91% for CD34, 6.52% for SMA, 2.17% for Desmin, 2.17% for S100 (2.17%); 24 (17.39%) were benign, 39 (28.26%) had low tendency of malignancy, 33 (23.91%) had moderate tendency of malignancy, 21 (15.225%) had high tendency of malignancy, 21 (15.22%) were malignant.

CONCLUSION: GISTs have unique clinical and pathologic characteristics. CD117 detection has high specificity and sensitivity in diagnosing GISTs. Detecting CD34, SMA, Desmin, and S100 together can help diagnose GISTs. The malignancy of GISTs depends on the size, location and mitotic count of the lesion.

Predictors of recurrence after resection of small gastric gastrointestinal stromal tumors of 5 cm or less

GOALS

To evaluate the recurrence predicting factors of small gastric gastrointestinal stromal tumors (GISTs) through the long-term follow-up after surgical/endoscopic resection.

BACKGROUND

Although small gastric GISTs are known to have a low risk of recurrence after complete resection, the prognostic factors are not well known.

STUDY

The study retrospectively analyzed the records of 136 patients with primary gastric GISTs of 5 cm or less without metastasis who underwent surgical/endoscopic resection between March 1997 and December 2008 at the Asan Medical Center, and who were followed-up for at least 3 months after resection. Specimens were assessed for tumor size, mitotic index, and microscopic resection margin. Specimen sections were immunohistochemically stained to determine the levels of expression of the cell cycle proteins p53, p16(INK4), pRb, cyclin D1, and Ki-67. DNA was extracted from high-risk tumors to analyze for KIT mutations.

RESULTS

Among 136 patients, 5 (3.7%) patients with tumors with a high mitotic index showed recurrence at a median 23 months post resection. None of 14 patients with microscopic positive resection margins showed recurrence during a median follow-up time of 32 months. A high mitotic index was a predictor of recurrence (P<0.001), but that tumor size, method of resection, or margin status were not. In addition, abnormal p53 expression was found to be associated with recurrence (P=0.004). All assessable high-risk tumors had a KIT exon 11 mutation.

CONCLUSIONS

Predictors of recurrence of gastric GISTs of 5 cm or less were a high mitotic index and abnormal p53 expression. A positive microscopic resection margin was not associated with recurrence.

Practical management of imatinib in gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) have an incidence of 7-15 occurrences per million people. Tyrosine kinase inhibitors (TKIs) have significantly improved clinical outcomes as part of multidisciplinary disease management. The authors will review developments in the management of GISTs, including diagnosis, risk stratification, prognosis, and treatment with imatinib. Imatinib is recommended for postsurgical adjuvant therapy and, where appropriate, neoadjuvant therapy. Clinical practice guidelines recommend first-line imatinib for metastatic and unresectable GISTs based on trials showing efficacy at the standard dose (400 mg per day) and at higher doses of 600-800 mg per day. Oncology nurses play a key role in patient management through (a) patient education about GISTs and their treatment including the use of imatinib, (b) timely scheduling of radiologic follow-up to assess treatment response, (c) monitoring treatment adherence, (d) helping to sustain imatinib dose intensity by monitoring toxicities and drug interactions and by counseling patients to prevent treatment interruptions, and (e) collaborating with the multidisciplinary medical team to pursue imatinib dose escalation or other treatment options if patients have primary or acquired mutation-based resistance to imatinib.

Recurrence Risk after Resection of Gastrointestinal Stromal Tumors: Size is Not All that Matters… the Consequences of Tumor Rupture

Gastrointestinal stromal tumors (GISTs) are mesenchymal tumors that most commonly have activating mutations in KIT. Recurrence after complete resection remains a significant problem, and the ability to identify patients at high risk for recurrence would allow for selective use of adjuvant therapies such as imatinib in patients who may garner the most benefit. Initial staging systems stratified recurrence risk by tumor size and mitotic index, whereas subsequent staging systems also included tumor location. However, other clinical factors may influence prognosis and the risk for tumor recurrence after surgery. The purpose of this article is to highlight tumor rupture as an additional risk factor that should be considered when assessing for recurrence risk. Tumor rupture is associated with decreased survival and increased recurrence rates, but it is not universally included in current staging systems. Patients with ruptured GISTs may not meet the risk criteria elaborated in some current staging systems, yet these patients are at high risk for tumor recurrence and may benefit from adjuvant imatinib therapy. A fundamental understanding of all the risk factors for tumor recurrence, including tumor rupture, and appropriate consideration for adjuvant therapy through a multidisciplinary approach are requisite for the maximal prevention of disease recurrence.

Phase II trial of neoadjuvant/adjuvant imatinib mesylate for advanced primary and metastatic/recurrent operable gastrointestinal stromal tumors: long-term follow-up results of Radiation Therapy Oncology Group 0132

BACKGROUND

Imatinib inhibits the KIT and PDGFR tyrosine kinases, resulting in its notable antitumor activity in gastrointestinal stromal tumor (GIST). We previously reported the early results of a multi-institutional prospective trial (RTOG 0132) using neoadjuvant/adjuvant imatinib either in primary resectable GIST or as a planned preoperative cytoreduction agent for metastatic/recurrent GIST. METHODS.: Patients with primary GIST (≥5 cm, group A) or resectable metastatic/recurrent GIST (≥2 cm, group B) received neoadjuvant imatinib (600 mg/day) for approximately 2 months and maintenance postoperative imatinib for 2 years. We have now updated the clinical outcomes including progression-free survival, disease-specific survival, and overall survival at a median follow-up of 5.1 years, and we correlate these end points with duration of imatinib therapy.

RESULTS

Sixty-three patients were originally entered (53 analyzable: 31 in group A and 22 in group B). Estimated 5-year progression-free survival and overall survival were 57% in group A, 30% in group B; and 77% in group A, 68% in group B, respectively. Median time to progression has not been reached for group A and was 4.4 years for group B. In group A, in 7 of 11 patients, disease progressed >2 years from registration; 6 of 7 patients with progression had stopped imatinib before progression. In group B, disease progressed in 10 of 13 patients>2 years from registration; 6 of 10 patients with progressing disease had stopped imatinib before progression. There was no significant increase in toxicity compared with our previous short-term analysis.

CONCLUSIONS

This long-term analysis suggests a high percentage of patients experienced disease progression after discontinuation of 2-year maintenance imatinib therapy after surgery. Consideration should be given to studying longer treatment durations in intermediate- to high-risk GIST patients.

Adjuvant imatinib therapy for gastrointestinal stromal tumors

Surgery is the standard of care for primary resectable gastrointestinal stromal tumors (GISTs), but half of surgically treated patients relapse. Imatinib (IM) has been shown to prolong recurrence-free survival after complete surgery and is now approved as adjuvant therapy (400  mg/day) for high-risk GIST patients. IM is well tolerated, with mild to moderate side effects observed. Whether adjuvant IM prolongs overall survival is under evaluation in two ongoing clinical trials.

Surveillance strategies for gastrointestinal stromal tumors

Although only 10-30% of gastrointestinal stromal tumors (GISTs) are clinically malignant, all have some degree of malignant potential. The management of high risk patients should be evidence based. However, prospective data and a consensus for guidelines concerning the screening of asymptomatic high risk patients and surveillance following multidisciplinary treatment do not exist. This review provides an overview of GIST, with an emphasis on the available data regarding screening and surveillance of certain populations with GISTs.

Prognostic factors for survival post surgery for patients with gastrointestinal stromal tumors

BACKGROUND

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms located in the alimentary tract. Our aim was to assess the influence of prognostic factors on survival in patients surgically treated for GISTs.

STUDY

One hundred and five patients treated between January 1989 and December 2008 were available for study. A retrospective analysis of prognostic factors (age, gender, mitotic index, tumor location, tumor size, risk of malignant behavior, and coexisting other neoplasm) was performed. Univariate and multivariate survival analyses were undertaken.

RESULTS

Univariate analyses revealed the importance of patient gender (p = 0.007), disease location (p = 0.055), mitotic index (p = 0.054) and coexistence with other neoplasms (p = 0.004). However, multivariate analysis showed 3 independently statistically significant factors: coexistence with other neoplasm (RR = 3.53, p = 0.004), male gender (RR = 2.60, p = 0.011) and mitotic index ≥10/50 HPF, (RR = 2.60, p = 0.042).

CONCLUSIONS

Our study has shown that male gender, a high mitotic index ≥10/50 HPF, and coexistence with other malignant neoplasms were independent poor prognostic factors in patients with GIST. The presence of middle or lower gut disease location leads to an increased risk of mortality when compared with the upper gut.

Tumor estromal gastrointestinal: análise de 146 casos do centro de referência do Instituto Nacional do Câncer - INCA

OBJETIVO: Avaliar os resultados do tratamento de GIST no INCA. MÉTODOS: Análise retrospectiva de todos os casos de GIST tratados no INCA no período de 1997 a 2009. RESULTADOS: Analisamos 146 pacientes, com média de idade de 44,5 anos e predomínio do sexo feminino. O principal sintoma foi dor abdominal. Tivemos ocorrência de segundo primário em 22% dos casos e na imuno-histoquímica, 92% foram positivos para CD117. A localização mais frequente foi estômago e predominou o grupo de alto risco. A cirurgia foi R0 (extenso) em 70% e os principais sítios de metástases foram fígado e peritônio. A sobrevida global foi, respectivamente, em dois e cinco anos de 86% e 59%. Houve significante diferença entre a sobrevida global (p=0,29) do grupo de alto risco versus os demais. CONCLUSÃO: Os nossos pacientes apresentam-se principalmente sob forma de doença de alto risco com repercussão óbvia na sobrevida. O uso de Imatinib melhorou a sobrevida dos pacientes com doença metastática e recidivada. Devemos estudar seu uso no cenário de adjuvância e neoadjuvancia visando melhorar os índices do grupo de alto risco. A criação de centros referenciais é uma necessidade para o estudo de doenças pouco frequentes.

Gastrointestinal stromal tumor: advances in diagnosis and management

CONTEXT

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract and should be differentiated from other mesenchymal tumors. They harbor specific activating mutations in the KIT or platelet-derived growth factor receptor α ( PDGFRA ) receptor tyrosine kinases, which makes them responsive to pharmacologic inhibitors, such as imatinib mesylate and sunitinib malate.

OBJECTIVES

To provide a comprehensive review of the pathogenesis of GIST and the underlying principles of targeted therapy, to review the salient histologic and immunohistochemical features that facilitate the distinction of GIST from other mesenchymal neoplasms of the gastrointestinal tract, and to present the prognostic parameters for risk stratification that guide clinical management.

DATA SOURCES

Review of the English literature through PubMed as well as personal experience. Photographs were taken from cases encountered at the Cleveland Clinic.

CONCLUSIONS

The discovery of the KIT -GIST connection has not only improved the diagnostic accuracy of GISTs but also provided us with a better understanding of the histogenesis and molecular pathogenesis of these neoplasms.

Gastrointestinal stromal tumor surgery and adjuvant therapy

Gastrointestinal stromal tumors (GIST) are a unique class of mesenchymal tumors identified within the past decade. Intense molecular and genetic study has been used to characterize these tumors and develop treatment strategies. Although the mainstay of treatment remains surgical resection, therapy targeted at inhibiting tyrosine kinases has had dramatic results. Because of the rapid accumulation of information about the diagnosis and treatment of these tumors, the National Comprehensive Cancer Network convened a GIST task force to provide updated recommendations in 2010. As understanding of these tumors advances, rapid changes in recommendations will continue and should warrant regular updates in tumor management.

Advances in the surgical management of gastrointestinal stromal tumor

Imatinib mesylate has revolutionized the treatment of GIST. Dramatic changes in clinical practice have been observed in the past decade. Nonetheless, time has also revealed the limitations of treating GIST with a single agent alone, as resistance to imatinib has become a significant clinical dilemma. Surgical resection still remains the only chance for a cure. However, it is clear that GIST is a complex disease and requires effective integration of surgery and targeted therapy to reduce recurrence after resection of primary GIST or to prolong survival in metastatic disease. Recent studies have begun to delineate the feasibility of multimodal treatment of this disease. Knowledge gained thus far, along with ongoing and future investigations of GIST, will be extremely relevant to the potential use of molecular targeted therapy for other solid neoplasms.

The management of gastrointestinal stromal tumors: a model for targeted and multidisciplinary therapy of malignancy

Gastrointestinal stromal tumor (GIST) has become a model for targeted therapy in cancer. The vast majority of GISTs contain an activating mutation in either the KIT or platelet-derived growth factor A (PDGFRA) gene. GIST is highly responsive to several selective tyrosine kinase inhibitors. In fact, this cancer has been converted to a chronic disease in some patients. Considerable progress has been made recently in our understanding of the natural history and molecular biology of GIST, risk stratification, and drug resistance. Despite the efficacy of targeted therapy, though, surgery remains the only curative primary treatment and cures >50% of GIST patients who present with localized disease. Adjuvant therapy with imatinib prolongs recurrence-free survival and may improve overall survival. Combined or sequential use of tyrosine kinase inhibitors with other agents following tumor molecular subtyping is an attractive next step in the management of GIST.

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.

Validation of the Joensuu risk criteria for primary resectable gastrointestinal stromal tumour - the impact of tumour rupture on patient outcomes

BACKGROUND

Approval of imatinib for adjuvant treatment of gastrointestinal stromal tumours (GIST) raised discussion about accuracy of prognostic factors in GIST and the clinical significance of the available risk stratification criteria.

METHODS

We studied the influence of a new modification of the NIH Consensus Criteria (the Joensuu risk criteria), NCCN-AFIP criteria, and several clinicopathological factors, including tumour rupture, on relapse-free survival (RFS) in a prospectively collected tumour registry series consisting of 640 consecutive patients with primary, resectable, CD117-immunopositive GIST. The median follow-up time after tumour resection was 39 months. None of the patients received adjuvant imatinib.

RESULTS

The median RFS time after surgery was 50 months. In univariable analyses, high Joensuu risk group, tumour mitotic count >5/50 HPF, size >5 cm, non-gastric location, tumour rupture (7% of cases; P = 0.0014) and male gender had adverse influence on RFS. In a multivariable analysis mitotic count >5/50HPF, tumour size >5 cm and non-gastric location were independent adverse prognostic factors. Forty, 151, 86 and 348 patients were assigned according to the Joensuu criteria to very low, low, intermediate and high risk groups and had 5-year RFS of 94%, 94%, 86% and 29%, respectively.

CONCLUSION

The Joensuu criteria, which include 4 prognostic factors (tumour size, site, mitotic count and rupture) and 3 categories for the mitotic count, were found to be a reliable tool for assessing prognosis of operable GIST. The Joensuu criteria identified particularly well high risk patients, who are likely the proper candidates for adjuvant therapy.

Efficacy of imatinib mesylate neoadjuvant treatment for a locally advanced rectal gastrointestinal stromal tumor

Surgery is the standard treatment for a primary gastrointestinal stromal tumor (GIST); however, surgical resection is often not curative, particularly for large GISTs. In the past decade, with imatinib mesylate (IM), management strategies for GISTs have evolved significantly, and now IM is the standard care for patients with locally advanced, recurrent or metastatic GISTs. Adjuvant therapy with imatinib was recently approved for use, and preoperative imatinib is an emerging treatment option for patients who require cytoreductive therapy. IM neoadjuvant therapy for primary GISTs has been reported, but there is no consensus on the dose of the drug, the duration of treatment and the optimal time of surgery. These are critical because drug resistance or tumor progression can develop with a prolonged treatment. This report describes two cases of large rectal malignant GISTs, for which a abdominoperineal resection was initially anticipated. The two patients received IM preoperative treatment; we followed-up with CT or magnetic resonance imaging to access the response. After 9 months of treatment, a multi-disciplinary consensus that maximal benefit from imatinib had been achieved was reached. We determined the best time for surgical intervention and successfully performed sphincter-preserving surgery before resistance to imatinib or tumor progression occurred. We believe that a multidisciplinary team approach, considerating the optimal duration of therapy and the timing of surgery, is required to optimize treatment outcome.

The role of mutational analysis of KIT and PDGFRA in gastrointestinal stromal tumors in a clinical setting

Gastrointestinal stromal tumors (GIST) are the most common mesenchymal tumors of the gastrointestinal tract. Most GIST harbor a mutation affecting either the KIT or PDGFRA genes, whereas a small subgroup of tumors is wild type for mutations.Mutation of tyrosine kinase receptors is a mechanism of drug resistance that can occur either at the beginning of treatment (primary resistance) or during the course of therapy (secondary resistance). In addition, mutational status can predict the response to treatment with tyrosine kinase inhibitors, but the role of mutational status as a prognostic factor remains controversial.Evidence of a potential role of mutational status as a prognostic factor has emerged over the past decade. The presence of KIT exon 11 insertion/deletion involving either one or both Trp557-Lys558 amino acids correlates with a poorer clinical outcome if compared to patients with tumors wild type for KIT exon 11 mutations. A malignant clinical behavior has also been documented for KIT exon 13 and KIT exon 9 mutant GIST. Patients with GIST harboring a PDGFRA mutation seem to have a better prognosis than the others.The aim of this paper is to review the clinical significance of tyrosine kinase mutational status.

Advances in clinicopathological classification and genotyping of gastrointestinal stromal tumors

In recent years, the discovery of new markers and advances in mutation detection technologies have made it easy to diagnose gastrointestinal stromal tumor (GIST). However, it is still difficult to predict the biological behavior of GIST. Currently, the most prevalent GIST classification systems, including the National Institutes of Health (NIH) consensus criteria for assigning risk to gastrointestinal stromal tumors (2008 Revision) and the International Union Against Cancer TNM classification of malignant tumors (2010 version), are based on tumor size, mitotic rate, tumor location, and presence of a tumor rupture or not. Molecular genetic studies have shown that genotype of GIST is closely related to tumor prognosis and response to imatinib mesylate.

Gastrointestinal stromal tumors: molecular mechanisms and targeted therapies

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract and are diverse not only in their clinical behavior but also in their histologic appearance. GISTs are insensitive to conventional sarcoma chemotherapy and radiation. However GISTs are sensitive to small-molecule tyrosine kinase inhibitors as 85–90% of GISTs have KIT or platelet-derived growth factor receptor alpha (PDGFRA) mutations, which drive tumorigenesis. This review will briefly touch on the clinicopathological features of GIST, while the majority of the review will focus on the clinical and treatment ramifications of KIT and PDGFRA mutations found in GIST.

Clinical utility of the new American Joint Committee on Cancer staging system for gastrointestinal stromal tumors: current overall survival after primary tumor resection

BACKGROUND

The objectives of the current study were to assess the reliability of the new revision of the American Joint Committee on Cancer (AJCC) staging system for gastrointestinal stromal tumors (GISTs) based on the National Comprehensive Cancer Network-Armed Forces Institute of Pathology risk classification and to analyze the factors that influence after resection for primary GISTs in 2 AJCC groups: patients with GISTs originating from the stomach and omentum (G-GISTs) and patients with other primary GISTs located mainly in the small bowel (nongastric GISTs [NG-GISTs]).

METHODS

The authors prospectively analyzed a group of 640 patients with primary, CD117-positive GISTs who underwent surgery with curative intention (R0/R1 resection), including 340 G-GISTs (55.5%) and 300 NG-GISTs (44.5%). Factors were explored that had an effect on disease-free survival time (DFS), which was calculated from the date of radical operation to the date of recurrence or last follow-up. The median follow-up was 39 months.

RESULTS

Compared with NG-GISTs, G-GISTs were characterized by a significantly lower median size (5.3 cm and 8.5 cm, respectively; P < .0001) and lower mitotic activity (median, 3 in 50 high-power fields [HPF] vs 5 in 50 HPF; P < .0001), and they were diagnosed in older patients (median age, 62 years vs 57 years; P = .002). The most commonly detected mutations in G-GIST were those located in KIT exon 11 (60.5%) and platelet-derived growth factor receptor alpha (PDGFRA) exon 18 (19%) versus KIT exons 11 and 9 in NG-GISTs (72% and 17.4%, respectively). The prognosis of patients who had G-GISTs was significantly better compared that of patients who had NG-GISTs, with 5-year DFS rates of 69% (median, 83 months) versus 43% (median, 33 months), respectively (P < .00001). The most significant prognostic factors that correlated with shorter DFS in both G-GISTs and NG-GISTs were primary tumor size >5 cm and >10 cm (P < .0001) and mitotic index >5 in 50 HPF and >10 in 50 HPF (P < .0001). The 5-year DFS rates in G-GISTs according to AJCC stage categories were as follows: 96% for stage IA tumors, 92% for stage IB tumors, 51% for II tumors, 22% for stage IIIA tumors, and 22% for stage IIIB tumors (P < .0001). The 5-year DFS rates in NG-GISTs according to AJCC categories were as follows: 92% for stage I tumors, 66% for stage II tumors, 28% for IIIA tumors, and 16% for IIIB tumors (P < .0001). The high prognostic significance of the AJCC classification also was confirmed for overall survival data, including the impact of therapy with tyrosine kinase inhibitors.

CONCLUSIONS

The reliability of AJCC risk classification after resection of primary GIST was confirmed for DFS and overall survival. Patients with primary G-GISTs had a better prognosis than patients with NG-GISTs. In both groups, primary tumor size and mitotic activity were the most important prognostic factors in terms of DFS.

Mutational status of KIT and PDGFRA and expression of PDGFRA are not associated with prognosis after curative resection of primary gastrointestinal stromal tumors (GISTs)

BACKGROUND

The aim of this study was to investigate if immunohistochemical expression and mutational status of KIT and PDGFRA in GISTs are associated with the clinical course and disease-free survival after curative resection of the primary tumor without adjuvant systemic therapy.

METHODS

Paraffin-embedded tumor sections of 95 GISTs were analyzed for KIT and PDGFRA expression by immunohistochemistry. PDGFRA expression was judged using a scoring system subdividing tumors in negative/weak and strong immunoreactivity groups. For mutation analysis, exons 9, 10, 11, 13, and 17 of KIT and exons 10, 12, 14, and 18 of PDGFRA were sequenced.

RESULTS

Of 95 R0-resected GISTs, 69% showed strong PDGFRA immunoreactivity. Gastric GISTs revealed a significantly higher rate of strong PDGFRA immunoreactivity (P = 0.01) and longer DFS (P = 0.015) than GISTs of the small intestine. KIT mutations were detected in 43 of 63 (68.3%) completely sequenced cases while PDGFRA mutations were identified in 6 cases (10%). In multivariate analysis, neither KIT/PDGFRA expression nor mutational status of KIT or PDGFRA were independent prognostic factors. Only mitotic rate predicted recurrence independently.

CONCLUSION

Our data do not support the notion that expression of PDGFRA or mutations in KIT or PDGFRA are independent prognostic factors after curative resection of primary GIST.

Surgical options for localized and advanced gastrointestinal stromal tumors

The development of imitinab has led to a revolution in the management of gastrointestinal stromal tumors (GIST), but surgical resection remains the cornerstone of treatment for patients with localized disease. The principles to surgical treatment of GIST include careful handling of tissues to prevent tumor rupture and resection to negative margins without the need for wide excision. Minimally invasive techniques have proven equally efficacious provided appropriate oncologic resections are performed.

Epidemiology, survival, and costs of localized gastrointestinal stromal tumors

Purpose:

The aim of this study is to examine the epidemiologic and economic burden in surgically resected localized gastrointestinal stromal tumor (GIST) patients versus age- and gender-matched controls.

Method:

Two data sources were used to conduct a series of complementary analyses. First, the Surveillance, Epidemiology, and End Results (SEER) cancer registry was used to identify diagnosed GIST patients from 1993 to 2002 and determine incidence, prevalence, and 3-year survival. Second, using the SEER–Medicare linked database, a matched case-control analysis was conducted to determine resource utilization, GIST recurrence, and costs. Because GIST recurrence is not explicitly defined in the database, patterns in resource use were used to identify probable recurrence. Kaplan–Meier Sample Average (KMSA) Estimator technique was used to estimate costs of GIST and recurrence.

Results:

SEER registry results show over the 10-year time horizon average annual GIST incidence was 0.32 per 100,000 persons in the United States, 15-year limited-duration prevalence was 1.62 per 100,000 persons, and 3-year survival was 73%. A total of 292 GIST patients were included in the SEER–Medicare analyses; 35 were identified with probable recurrence. GIST patients had increased risk of mortality (hazard ratio: 1.23; 95% confidence intervals: 0.94–1.61) compared to controls. Median recurrence-free and postrecurrence survival was 45 and 46 months, respectively. GIST patients incurred significantly higher medical care costs in the first year after initial resection, with $23,221 attributable to GIST. GIST recurrence costs totaled $101,700 over 5 years after initial resection.

Conclusions:

GIST is associated with substantial medical care costs, estimated recurrence costs more than $100,000; treatments that delay or reduce recurrence could substantially reduce the burden of GIST.

Late recurrences of gastrointestinal stromal tumours (GISTs) after 5 years of follow-up

In practice, relapses of gastrointestinal stromal tumours after long time of surgical resection occur. However, few published data are available for duration, intensity and imaging sources of follow-up in radically excised patients with localized disease. Therefore, every single institution chooses the surveillance schedule according to its experience. The aim of this study was to describe the late recurrences of disease 5 years after the primary tumour's excision in a series of patients with recurrent GIST from our institution. We retrospectively reviewed 42 patients with "recurrent" GIST, collected since 2001. Ten patients were always followed at our institution, and 32 patients came to our attention at the time of recurrence. The analysed series were divided into two groups: patients who developed recurrence before 5 years and patients who developed recurrence 5 years after the primary tumour's excision. Among 42 patients, 36 patients developed the recurrence within 5 years of the primary tumour excision, whereas 6 patients developed the recurrence 5 years after primary tumour excision diagnosed during follow-up or casually for other reasons. All patients had distant recurrence, involving liver and peritoneum, whereas no local relapse was observed. These patients were heterogeneous in primary tumour site, risk classification and molecular analysis. Duration of the follow-up for radically excised patients with GIST remains still unsettled; however, the integration of every clinical, pathological and molecular parameter is essential to optimize the duration and intensity of the follow-up for each single patient.

Navigating risk stratification systems for the management of patients with GIST

BACKGROUND

The central drivers of the aberrant behavior of gastrointestinal stromal tumors (GIST) are constitutively activated forms of stem-cell receptor factor, and, to a lesser extent, platelet-derived growth factor receptor alpha. Standard treatment for primary, localized GIST is surgical resection. Risk stratification systems assist in determining the risk of disease recurrence in individual patients with GIST, so disease management can be personalized.

METHODS

In May 2010, a literature review of the PubMed database was conducted to identify articles pertaining to prognostic factors and risk stratification systems for GIST. Key results from these studies were analyzed.

RESULTS

The first widely accepted risk stratification system for GIST, the National Institutes of Health consensus classification system, stratified patients into risk groups on the basis of tumor size and mitotic index. Tumor location (i.e., stomach or intestine) was subsequently shown to have independent prognostic value and was incorporated into the Miettinen-Lasota/Armed Forces Institute of Pathology risk stratification system. Tumor size, location, and mitotic index remain the main variables used in risk stratification systems. Other variables such as tumor rupture and GIST genotype have recently been shown to have prognostic value. As an alternative to stratification into discrete groups, nomograms present risk of recurrence as percentages on a continuous scale. Improved use of existing prognostic variables and routine incorporation of additional variables (e.g., GIST genotype) will further refine risk stratification systems.

CONCLUSIONS

Refinement of risk stratification systems will increase the precision of these systems for predicting recurrence, which may facilitate improvements in individual disease management.

Diagnostic criteria, specific mutations, and genetic predisposition in gastrointestinal stromal tumors

In 1998, gastrointestinal stromal tumor (GIST) emerged as a distinct oncogenetic entity and subsequently became a paradigm of targeted therapies in solid tumors. Diagnosis of GIST relies on both histology and immunohistochemistry. Ninety-five percent of GISTs express either KIT or DOG-1. Approximately 80%-90% of GISTs harbor gain-of-function mutations of either KIT or platelet-derived growth factor receptor alpha polypeptide (PDGFRA) receptor tyrosine kinase (RTK). More than 100 different mutations have been described, some of which are associated with specific clinical and/or histological characteristics. Detection of KIT or PDGFRA mutations is recommended in advanced GISTs because they are highly predictive of tumor response to RTK inhibitors, as well as in KIT-negative cases to confirm diagnosis. In most cases, GISTs are sporadic, but in rare cases, they are related with genetic predisposition, such as neurofibromatosis type 1, Carney triad, Carney-Stratakis syndrome, and inherited KIT or PDGFRA germline mutations.

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 of the rectum with bone and liver metastasis: a case study

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor of the gastrointestinal tract and may arise from any part of the gastrointestinal system. However, it is most frequently observed in the stomach (60%) and small intestines (30%). GIST is observed at a rate of 4% in the rectum. Distant metastases of GIST are rare, and the liver is the most common site of metastasis. This case is presented because of the rare incidence of bone metastasis to the femur head.

Molecular and clinicopathologic characterization of gastrointestinal stromal tumors (GISTs) of small size

Although Gastrointestinal stromal tumors (GISTs) affect about 0.0014% of the population, GISTs smaller than 1 cm (microGISTs) are detectable in about 20% to 30% of elderly individuals. This suggests that microGISTs likely represent premalignant precursors that evolve only in a minute fraction of cases toward overt GISTs. We sought histopathologic and molecular explanations for the infrequent clinical progression in small GISTs. To investigate the mechanisms of GIST progression and identify subsets with differential malignant potential, we carried out a thorough characterization of 170 GISTs <2 cm and compared their KIT/PDGFRA status with overt GISTs. The proliferation was lower in microGISTs compared with GISTs from 1 to 2 cm (milliGISTs). In addition, microGISTs were more frequently incidental, gastric, spindle, showed an infiltrative growth pattern, a lower degree of cellularity, and abundant sclerosis. The progression was limited to 1 ileal and 1 rectal milliGISTs. KIT/PDGFRA mutations were detected in 74% of the cases. The overall frequency of KIT/PDGFRA mutation and, particularly, the frequency of KIT exon 11 mutations was significantly lower in small GISTs compared with overt GISTs. Five novel mutations, 3 in KIT (p.Phe506Leu, p.Ser692Leu, p.Glu695Lys) 2 in PDGFRA (p.Ser847X, p.Ser667Pro), plus 4 double mutations were identified. Small GISTs share with overt GIST KIT/PDGFRA mutation. Nevertheless, microGISTs display an overall lower frequency of mutations, particularly canonical KIT mutations, and also carry rare and novel mutations. These molecular features, together with the peculiar pathologic characteristics, suggest that the proliferation of these lesions is likely sustained by weakly pathogenic molecular events, supporting the epidemiologic evidence that microGISTs are self-limiting lesions.

Discontinuation of imatinib in patients with advanced gastrointestinal stromal tumours after 3 years of treatment: an open-label multicentre randomised phase 3 trial

BACKGROUND

The effect of imatinib discontinuation on progression-free survival and overall survival in long-lasting responders with advanced gastrointestinal stromal tumours (GIST) is unknown. We assessed treatment interruption in patients with non-progressive disease according to the Response Evaluation Criteria In Solid Tumors criteria after 3 years of imatinib in a randomised trial.

METHODS

In this open-label national multicentre phase 3 study in France, patients with GIST free of progression after 3 years of imatinib 400 mg/day were randomly assigned to continue or interrupt imatinib. Randomisation was done centrally and independently from other study procedures with computer-generated permuted blocks of two and four patients stratified by participating centre and presence or absence of residual disease on CT scan. The primary endpoint was progression-free survival. An interim analysis was planned after the first 50 randomly assigned patients. Analysis was done according to the intention-to-treat principle-ie, all patients randomly assigned to a study group were included. This study is registered with ClinicalTrial.gov, number NCT00367861.

FINDINGS

434 patients were enrolled in this trial between May 27, 2002, and May 5, 2009. Between June 13, 2005, and May 30, 2007, 50 patients with non-progressive disease who had received 3 years of treatment with imatinib were randomly assigned to continue or interrupt their treatment, 25 patients in each group. By Dec 7, 2009, after a median follow-up of 35 months (95% CI 33-38) after random assignment, 2-year progression-free survival was 80% (95% CI 58-91) in the continuation group and 16% (5-33) in the interruption group (p < 0·0001). There was no difference in adverse events grade 3 or greater (oedema and asthenia) between the two groups.

INTERPRETATION

Imatinib interruption after 3 years in responders results in a high risk of rapid progression in patients with advanced GIST. Discontinuation of imatinib is not recommended outside clinical trials unless patients experience significant toxic effects.

FUNDING

Conticanet, the Ligue Contre Le Cancer du Rhone, and Novartis.

Pattern of recurrence in patients with ruptured primary gastrointestinal stromal tumour

BACKGROUND

This study assessed the outcomes of patients with a gastrointestinal stromal tumour (GIST) that ruptured before or during resection.

METHODS

The records of 23 patients (8 women, 15 men; median age 54 years) with ruptured primary non-metastatic GIST were retrieved from a database of 554 patients. The written surgical and pathology reports were analysed. Review pathology was performed in all 23 cases, and mutational analysis of KIT and platelet-derived growth factor α (PDGFRA) genes was performed in 21 patients. Median follow-up was 52 months.

RESULTS

Tumour rupture was spontaneous in 16 patients, following abdominal trauma in two and occurred during resection in five. Primary tumour location was the stomach in six patients, duodenum in one and small bowel in 16. Mean tumour size was 10·2 (range 4-28) cm. According to the Miettinen and Lasota risk classification, the distribution of very low-, low-, intermediate- and high-risk cases was one, two, five and 15 respectively. One patient remained disease-free at 83 months. Fifteen of 16 patients who did not receive adjuvant therapy developed tumour recurrence after a median of 19 months. Median recurrence-free survival in patients with KIT mutations involving codons 557-558 was 11 months.

CONCLUSION

Patients with a rupture of GIST into the abdominal cavity have a risk of recurrence of nearly 100 per cent. In patients with deletion mutations involving codons 557-558, recurrence-free survival was less than 1 year. All patient groups are clear candidates for adjuvant drug therapy.

Gastrointestinal Stromal Tumors with Unusual Localization: Report of Three Cases with a Brief Literature Review

The most common tumors derived from the mesenchyme of the gastrointestinal system are stromal tumors. These tumors are typically seen in the stomach and small intestine and less frequently in the colon, rectum and esophagus and are very rarely located outside the gastrointestinal system. Cure is provided with complete surgical resection with resection borders free of tumor. Tumor size, mitotic index, localization, CD117 and CD34 negativity in immunohistochemical studies, mucosal ulceration and presence of necrosis help to predict recurrence of the illness and patient survival. In high-risk gastrointestinal stromal tumors (GISTs) there is an increased rate of recurrence and shortened survival despite complete surgical resection. Thus patients with a high-risk GIST should be given adjuvant therapy with imatinib mesylate. Sunitinib maleate is another FDA-approved agent only for cases who cannot tolerate imatinib or who are resistant to it. Herein we present three cases with GISTs in different locations of the gastrointestinal system with a review of the relevant literature.

Rare anorectal neoplasms: gastrointestinal stromal tumor, carcinoid, and lymphoma

Several uncommon tumors occur in the anal canal such as gastrointestinal stromal tumors, carcinoids, and lymphoma. Increased clinical experience and advancements in molecular biology have improved the accuracy of pathologic diagnosis and guided treatment recommendations, which the author addresses in this article.