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

Gastrointestinal stromal tumour

Gastrointestinal stromal tumours (GISTs) are mesenchymal neoplasms that arise in the gastrointestinal tract, usually in the stomach or the small intestine and rarely elsewhere in the abdomen. They can occur at any age, the median age being 60-65 years, and typically cause bleeding, anaemia, and pain. GISTs have variable malignant potential, ranging from small lesions with a benign behaviour to fatal sarcomas. Most tumours stain positively for the mast/stem cell growth factor receptor KIT and anoctamin 1 and harbour a kinase-activating mutation in either KIT or PDGFRA. Tumours without such mutations could have alterations in genes of the succinate dehydrogenase complex or in BRAF, or rarely RAS family genes. About 60% of patients are cured by surgery. Adjuvant treatment with imatinib is recommended for patients with a substantial risk of recurrence, if the tumour has an imatinib-sensitive mutation. Tyrosine kinase inhibitors substantially improve survival in advanced disease, but secondary drug resistance is common.

Cost-effectiveness of 3-year vs 1-year adjuvant therapy with imatinib in patients with high risk of gastrointestinal stromal tumour recurrence in the Netherlands; a modelling study alongside the SSGXVIII/AIO trial

BACKGROUND

Surgical resection of gastrointestinal stromal tumour (GIST) is rarely curative in patients at high risk of tumour recurrence and therefore 1 year of post-surgery adjuvant imatinib therapy has been recommended in this sub-group. Recently, adjuvant imatinib therapy administered for 3 years has been demonstrated to further increase recurrence-free survival and overall survival. The goal of this study was to assess the economic value of extending the duration of adjuvant imatinib therapy in high-risk patients in the Netherlands.

METHODS

A multistate Markov model was developed to simulate how patients' clinical status after GIST excision evolves over time until death. The model structure encompassed four primary health states: free of recurrence, first GIST recurrence, second GIST recurrence, and death. Transition probabilities between the health states, data on medical care costs, and quality-of-life were obtained from published sources and from expert opinion.

RESULTS

The expected number of life years (or quality-adjusted life years, QALYs) was higher in the 3-year group than in the 1-year group, 8.91 (6.55) and 7.04 (5.18) years, respectively. In the 3-year and 1-year group, the expected total costs amounted to €120,195 and €79,361, of which, €74,631 (62%) and €27,619 (35%) were adjuvant therapy drug costs, respectively. The difference in health benefits, that is 1.87 life years or 1.37 QALYs, and costs, €40,835, resulted in incremental cost-effectiveness ratios (ICER) of €21,865 per life year gained, and €29,872 per QALY gained.

LIMITATIONS

A limitation of the study was inherently related to the uncertainty around the predictions of RFS. Scenario analyses were conducted to test the sensitivity of different RFS predictions on the results.

CONCLUSIONS

Delayed recurrence due to treatment with longer-term adjuvant imatinib therapy represents a cost-effective treatment option with an ICER below the generally accepted threshold in the Netherlands.

New fronts in the adjuvant treatment of GIST

PURPOSE

To review the prognostic factors and stratification systems used to determine the need for adjuvant therapy in the treatment of gastrointestinal stromal tumors (GIST), and to review recent clinical advances in investigation of the efficacy and safety of adjuvant imatinib mesylate treatment.

METHODS

Recent data from clinical trials of various durations of adjuvant imatinib in GIST are reviewed, with emphasis on key results from the Phase III American College of Surgeons Oncology Group (ACOSOG) Z9001 trial and the Scandinavian Sarcoma Group XVIII/Arbeitsgemeinschaft Internistische Onkologie (SSGXVIII/AIO) trial.

RESULTS

Complete surgical resection remains the standard of treatment for localized GISTs; however, disease recurrence occurs in up to 50 % of patients who undergo complete resection. The ACOSOG Z9001 trial established that 1 year of adjuvant imatinib reduces the risk of recurrence in patients with resected GIST. The SSGXVIII/AIO trial further demonstrated that 3-year adjuvant imatinib improves both recurrence-free survival and overall survival compared with 1-year therapy in patients at high risk of recurrence after surgery. Considering risk factors associated with tumor recurrence is essential for identifying the patients who are most likely to benefit from adjuvant imatinib.

CONCLUSIONS

Although the optimal duration of adjuvant therapy remains to be determined, results from these pivotal trials provide firm evidence that adjuvant imatinib improves recurrence-free survival and improved overall survival of patients in the SSGXVIII/AIO trial. Ongoing studies may shed further light on the benefits and harms of adjuvant therapy, as well as the most appropriate patient candidates for adjuvant imatinib treatment.

Extended adjuvant therapy with imatinib in patients with gastrointestinal stromal tumors : recommendations for patient selection, risk assessment, and molecular response monitoring

On the basis of the recently published results of a clinical trial comparing 12 and 36 months of imatinib in adjuvant therapy for gastrointestinal stromal tumors (GISTs), which demonstrated clinical benefit of longer imatinib treatment in terms of delaying recurrences and improving overall survival, both the US Food and Drug Administration and the European Medicines Agency have updated their recommendations and approved 36 months of imatinib treatment in patients with v-kit Hardy-Zuckerman 4 feline sarcoma viral oncogene homolog (KIT)-positive GISTs (also known as CD117-positive GISTs) at high risk of recurrence after surgical resection of a primary tumor. This article discusses patient selection criteria for extended adjuvant therapy with imatinib, different classifications of risk of recurrence, and assessment of the response to therapy.

Adherence to imatinib therapy in patients with gastrointestinal stromal tumors

Imatinib mesylate, an oral tyrosine kinase inhibitor, is indicated for first-line treatment of patients with unresectable and/or metastatic gastrointestinal stromal tumors (GIST). Imatinib also is approved as adjuvant therapy for patients following resection of primary GIST. Despite the efficacy of imatinib for the treatment of patients with GIST, adherence to treatment can prove difficult. Clinical studies have identified a number of factors that have a significant association with non-adherence to therapy, including age >51years, female sex, a high number of concomitant medications, and complications with patients' therapy or the disease itself. Moreover, treatment-related adverse events and increased healthcare costs have been shown to have an impact on patients' adherence to therapy. A study of perceptions of adherence to therapy found discrepancies between actual and perceived adherence rates; both patients and physicians overestimate adherence to treatment. Non-adherence to treatment is not exclusive to oncology, and occurs in other disease areas, particularly with chronic conditions. Evidence from other disease areas suggests that routine assessment of adherence and the implementation of adherence programs can lead to improvements in health status and reduced healthcare costs. Improving patient adherence to imatinib treatment for patients with unresectable/metastatic GIST is particularly important, because non-adherence has a significant impact on clinical outcomes and healthcare costs. Therefore, the effective management of treatment-related adverse events along with patient education may be important in keeping patients compliant with continuous therapy.

Gastrointestinal stromal tumors: risk assessment and adjuvant therapy

Adjuvant imatinib prolongs recurrence-free survival and probably overall survival of patients who have undergone surgery for gastrointestinal stromal tumor (GIST). Estimation of the risk of recurrence with a prognostication tool and tumor mutation analysis is essential before imatinib initiation, because approximately 60% of patients with GIST with operable tumor are cured by surgery alone and some mutated tyrosine kinases are insensitive to imatinib. Adjuvant imatinib is usually administered for 3 years at the dose of 400 mg once daily. Early detection of tumors that recur despite adjuvant therapy with longitudinal imaging of the abdomen is likely beneficial.

A multidisciplinary approach to the diagnosis and treatment of gastrointestinal stromal tumor

Management of patients with gastrointestinal stromal tumor (GIST) typically involves a combination of surgical, pathologic, and pharmacologic interventions. Gastroenterologists are often the first specialists to encounter patients presenting with GIST and are therefore responsible for facilitating early intervention strategies. Although patients with gastric or small-bowel GISTs typically present with symptoms, a diagnosis of GIST should be considered whenever a submucosal lesion is seen endoscopically. Visualization by standard endoscopy often can determine tumor location and size, although endoscopic ultrasound (EUS) is the most accurate imaging technique for submucosal lesions. Biopsy techniques that yield sufficient tumor samples for diagnostic studies, such as EUS-guided fine needle aspiration, are essential, although other approaches such as EUS-guided core needle biopsy may increase diagnostic yield for subepithelial lesions. Pathology assessment should include immunohistochemical staining for KIT and possibly DOG1 expression, and mutational analysis can have prognostic and predictive value for certain patients. R0 resection is the goal for patients with localized or potentially resectable tumors, which often can be accomplished by laparoscopic resection, even for larger tumors. Medical oncologists play a key role in assessing risk of recurrence after resection and optimizing tyrosine kinase inhibitor therapy in the adjuvant or metastatic setting. Cytoreductive surgery may have value for patients with recurrent or metastatic GIST who exhibit stable disease or respond to tyrosine kinase inhibitor therapy. A coordinated multidisciplinary approach over the course of the disease will serve to enhance communication among GIST team members, reduce risk of progression, and optimize outcomes.

Giant extra gastrointestinal stromal tumor of lesser omentum obscuring the diagnosis of a choloperitoneum

INTRODUCTION

Herein we present an extremely rare case of a giant extra gastrointestinal stromal tumor (EGIST) of the lesser omentum obscuring the diagnosis of a choloperitoneum.

PRESENTATION OF CASE

A 79 years old female was admitted to our hospital with symptoms of vomiting and epigastric pain. Abdominal computer tomography revealed a sizable formation that was diagnosed as a tumor of the pancreas. In laparotomy, a choloperitoneum was diagnosed as the cause of patient's symptoms. A tumor adherent firmly to the lesser curvature of stomach was also discovered. Cholecystectomy and subtotal gastrectomy were performed. Histologically, the tumor was diagnosed as a EGIST of the lesser omentum. The patient did not receive any adjuvant therapy and after two years of follow up she is without any recurrence.

DISCUSSION

Omental EGISTs may remain clinically silent despite the large tumor's size. It is difficult to differentiate a EGIST in the lesser omentum from a GIST of the lesser curvature of the stomach, despite the use of advanced radiological imaging techniques. Our case of a giant EGIST of lesser omentum obscuring the diagnosis of acute choloperitoneum is the only one reported in literature.

CONCLUSION

EGISTs that arise from the omentum are very rare and complete surgical resection is the only effective treatment approach. Adjuvant therapy following resection of localized disease has become standard of care in high risk cases.

Efficacy and economic value of adjuvant imatinib for gastrointestinal stromal tumors

OBJECTIVE

This article presents the clinical effectiveness and cost-effectiveness of the use of adjuvant imatinib mesylate for treating patients with localized primary gastrointestinal stromal tumors (GISTs) and discusses the impact of prolonged treatment with adjuvant imatinib on health care costs.

METHODS

A systematic review of the medical literature was conducted to explore recently reported clinical trials demonstrating the clinical benefit of adjuvant imatinib in GISTs, along with analyses discussing the economic impact of adjuvant imatinib.

RESULTS

Two phase III trials have demonstrated a significant clinical benefit of adjuvant imatinib treatment in GIST patients at risk of recurrence after tumor resection. Guidelines now suggest adjuvant treatment for at least 3 years in patients at high risk of recurrence. Despite this clinical effectiveness, prolonged use of adjuvant imatinib can lead to an increase in the risk for adverse events and to increased costs for both patients and health care systems. However, the increased cost is partially offset by cost reductions associated with delayed or avoided GIST recurrences. Three years of adjuvant treatment in high-risk patients was concluded to be cost-effective. Therefore, the careful selection of patients who are most likely to benefit from treatment can lead to improved clinical outcomes and significant cost savings.

CONCLUSION

Although introducing adjuvant imatinib has an economic impact on health plans, this effect seems to be limited. Several analyses have demonstrated that adjuvant imatinib is more cost-effective for treating localized primary GISTs than surgery alone. In addition, 3 years of adjuvant imatinib is more cost-effective than 1 year of adjuvant therapy.

Tumor rupture during surgery for gastrointestinal stromal tumors: Pay attention!

In a recently published letter to the editor, we debated the proposal by Coccolini et al to treat gastrointestinal stromal tumors (GISTs) of the esophagogastric junction with enucleation and, if indicated, adjuvant therapy. We highlighted that, because the prognostic impact of a T1 high-mitotic rate esophageal GIST is worse than that of a T1 high-mitotic rate gastric GIST, enucleation may not be adequate surgery for esophagogastric GISTs with a high mitotic rate. In rebuttal, Coccolini et al pointed out the possible bias in assessment of the mitotic rates due to the lack of standardized methods and underlined that the site and features of the tumor need to be carefully considered in evaluation of the risk-benefit balance. Here we confirm that, apart from the problematic issue of mitotic counting, enucleation should not be indicated for GISTs at any site to reduce the risk of tumor rupture, which has been recently considered to be an unfavorable prognostic factor, and to avoid microscopic residual tumor.

Use of potassium channel tetramerization domain-containing 12 as a biomarker for diagnosis and prognosis of gastrointestinal stromal tumor

Previously, we showed that the expression of potassium channel tetramerization domain-containing 12 (KCTD12), which was discovered by a proteomics approach, is associated with high-risk behavior of gastrointestinal stromal tumors (GISTs). Here, we examined the distribution and expression of this protein by immunostaining with a commercially available polyclonal KCTD12 antibody in GISTs (n = 64) and other types of malignancy (n = 168) to clarify its diagnostic and clinical significance. Diffuse KCTD12 immunoreactivity was found in most GISTs (52 cases; 81%). KCTD12 expression was observed primarily in vascular endothelial cells, Purkinje cells of the cerebellum, and some neurons scattered throughout the cerebral cortex. KCTD12 was absent from not only the interstitial cells of Cajal but also interstitial cells of Cajal hyperplasia that was encountered incidentally in colon diverticulitis. KCTD12 immunostaining was also seen in malignant peripheral nerve sheath tumors (2/10 cases; 20%), synovial sarcomas (2/10; 20%), solitary fibrous tumor (1/8; 13%), angiosarcoma (1/7; 14%), and colon adenocarcinoma (1/24; 4%). In survival analyses, the 5-year recurrence-free survival rate of patients without KCTD12 expression was only 16.7% compared with 95.6% in those with KCTD12 expression (P < .0001). Ki-67 and KCTD12 were significant predictors of recurrence-free survival, and KCTD12 expression provided additional information about recurrence-free survival after accounting for Ki-67 status. Overall, KCTD12 expression was specific for GISTs from neoplastic and nonneoplastic adult tissues other than brain and served as a predictor of GIST recurrence. These findings suggest that KCTD12 is a useful and reliable biomarker for both the diagnosis and prognosis of GIST.

Adjuvant therapy of gastrointestinal stromal tumors (GIST)

Imatinib was proven to be effective for the adjuvant treatment of localized, surgically excised, gastrointestinal stromal tumors (GIST). Currently, there is proof that it is able to delay relapse and prolong survival. An effect on cure rate of localized GIST is still to be proven, given the shape of relapse-free survival curves, which apparently tend to overlap after 2-3 years from completion of the adjuvant period. Although observation for a longer follow-up is needed, attempts to prolong adjuvant therapy beyond the currently standard 3 years have been made and the results are awaited. However, the impact of more prolonged adjuvant intervals on secondary resistance is unknown, so that standard practice is still 3 years in most institutions. The adjuvant choice should be based on a rather precise identification of the relapse risk of the single patient, reserving treatment to the high-risk subgroups. The choice also should be personalized on the basis of genotype: generally, PDGFRA D842V mutated and wild-type GIST are excluded. Additional results from completed trials on a longer follow-up are awaited to further refine such "precision" decision-making. There are several instances in which part of the "adjuvant" treatment may be administered preoperatively, even on the face of a surgically resectable GIST, to make surgery more limited and/or safer.

Risk stratification models and mutational analysis: keys to optimising adjuvant therapy in patients with gastrointestinal stromal tumour

Imatinib is a standard of care in the adjuvant treatment of patients with resected gastrointestinal stromal tumour (GIST). Two important trials have shown a reduction in GIST recurrence rates for patients treated with imatinib 400 mg daily for 1 year; one of these trials also demonstrated a significant improvement in overall survival for patients with GIST at high risk of recurrence who were treated for 3 years. However, not all patients will benefit from adjuvant treatment. Considering the patient types in both trials, treatment decisions must take into account a number of factors including risk of recurrence and mutational status. Tumour characteristics including tumour size, location and mitotic index are the main prognostic factors of recurrence-free survival (RFS) after surgical resection of GISTs. Research, much of it in the advanced/metastatic setting, shows that mutational analysis is definitely predictive of treatment efficacy and probably prognostic of RFS. Patients on imatinib whose tumours harbour mutations in exon 11 of the KIT gene tend to have superior RFS compared with patients with exon 9 mutations. In contrast, patients with wild-type GIST often have disease that follows an indolent course and has limited sensitivity to imatinib in most cases. As such, increased use of existing risk-stratification schemes and mutational analysis will be essential for optimising tailored treatment approaches. In this review, the development and prognostic/predictive utility of key risk stratification tools and mutational analysis of GIST are discussed herein with the goal of facilitating adjuvant treatment decisions for patients with GIST.

SEOM guidelines for gastrointestinal stromal sarcomas (GIST)

Gastrointestinal stromal sarcomas (GISTs) are the most common mesenchymal tumours originating in the digestive tract. These tumours have become a model of multidisciplinary work in oncology: the participation of several specialities (oncologists, pathologists, surgeons, molecular biologists, radiologists and others) has allowed advances in the understanding of this tumour and the consolidation of a targeted therapy, imatinib, as the first molecular treatment that is efficacious in solid tumours. Following the introduction of this drug, median survival of patients with advanced stage GIST has gone from 18 to more than 60 months. Therapy planning of GIST must be considered within a multidisciplinary context, and it is advisable that it takes place in reference centres for the care of sarcomas and GIST participating in clinical trials.

Adjuvant therapy in primary GIST: state-of-the-art

BACKGROUND

The management of primary gastrointestinal stromal tumours (GISTs) has evolved with the introduction of adjuvant therapy. Recently reported results of the SSG XVIII/AIO trial by the Scandinavian Sarcoma Group (SSG) and the German Working Group on Medical Oncology (AIO) represent a significant change in the evidence for adjuvant therapy duration. The objectives of this European Expert Panel meeting were to describe the optimal management and best practice for the systemic adjuvant treatment of patients with primary GISTs.

MATERIALS AND METHODS

A panel of medical oncology experts from European sarcoma research groups were invited to a 1-day workshop. Several questions and discussion points were selected by the organising committee prior to the conference. The experts reviewed the current literature of all clinical trials available on adjuvant therapy for primary GISTs, considered the quality evidence and formulated recommendations for each discussion point.

RESULTS

Clinical issues were identified and provisional clinical opinions were formulated for adjuvant treatment patient selection, imatinib dose, duration and patient recall, mutational analysis and follow-up of primary GIST patients. Adjuvant imatinib 400 mg/day for 3 years duration is a standard treatment in all patients with significant risk of recurrence following resection of primary GISTs. Patient selection for adjuvant therapy should be based on any of the three commonly used patient risk stratification schemes. R1 surgery (versus R0) alone is not an indication for adjuvant imatinib in low-risk GIST. Recall and imatinib restart could be proposed in patients who discontinued 1-year adjuvant imatinib within the previous 3 months and may be considered on a case-by-case basis in patients who discontinued within the previous year. Mutational analysis is recommended in all cases of GISTs using centralised laboratories with good quality control. Treatment is not recommended in an imatinib-insensitive D842V-mutated GIST. During adjuvant treatment, patients are recommended to be clinically assessed at 1- to 3-month intervals. Upon discontinuation, computed tomography scan (CT) scans are recommended every 3 to 4 months for 2 years when the risk of relapse is highest, followed by every 6 months until year 5 and annually until year 10 after treatment discontinuation.

CONCLUSIONS

Key points in systemic adjuvant treatment and clinical management of primary GISTs as well as open questions were identified during this European Expert Panel meeting on GIST management.

Localized gastrointestinal stromal tumor of the rectum: An uncommon primary site with prominent disease and treatment-related morbidities

Well-established clinicopathological variables used in the risk stratification of gastrointestinal stromal tumor (GIST) may not completely predict rectal GIST, an uncommon and poorly studied GIST subset. The aim of the present study was to determine the patterns of relapse and morbidities associated with recurrence in rectal GIST. A single-institution retrospective study between 2002 and 2011 was conducted, identifying 9 patients (8%) with localized rectal GIST, while comparing small intestinal (n=37) and gastric (n=63) GIST (median age, 60 years). Rectal GIST tumors were smaller compared to small intestinal/gastric GIST (P=0.044). The number of mitoses per 50 high-power field (HPF) did not differ by primary site. In general, 73% of patients were high-risk, as defined by the National Institutes of Health (NIH) consensus criteria, however, only 25% received adjuvant imatinib. Fewer rectal GIST patients achieved negative surgical margins compared to small intestinal/gastric GIST (67 vs. 92%; P=0.054). Of the 9 patients with localized rectal GIST 6 had peri-operative tumor rupture, anastomotic breakdown or required anal sphincter-compromising surgery. At the time of the first relapse, 83% of the recurrences were local failures for rectal GIST, compared to 21% for small intestinal/gastric GIST (P=0.005). The median relapse-free survival was 51 months for the entire cohort, and 54, 36 and 56 months for rectal, small intestinal and gastric GIST, respectively (P=0.468). Rectal GIST was found to be associated with high rates of local relapse and significant morbidity, despite being significantly smaller compared to GIST of other sites. A multimodality peri-operative therapeutic approach may be required to improve outcomes.

Pathology of gastrointestinal stromal tumors

Gastrointestinal stromal tumor (GIST) is a well recognized and relatively well understood soft tissue tumor. Early events in GIST development are activating mutations in KIT or PDGFRA, which occur in most GISTs and encode for mutated tyrosine receptor kinases that are therapeutic targets for tyrosine kinase inhibitors, including imatinib and sunitinib. A small minority of GISTs possessing neither KIT nor PDGFRA mutations may have germline mutations in SDH, suggesting a potential role of SDH in the pathogenesis. Immunohistochemical detection of KIT, and more recently DOG1, has proven to be reliable and useful in the diagnosis of GISTs. Because current and future therapies depend on pathologists, it is important that they recognize KIT-negative GISTs, GISTs in specific clinical contexts, GISTs with unusual morphology, and GISTs after treatment. This review focuses on recent developments in the understanding of the biology, immunohistochemical diagnosis, the role of molecular analysis, and risk assessment of GISTs.

Approval summary: imatinib mesylate for one or three years in the adjuvant treatment of gastrointestinal stromal tumors

On January 31, 2012, the U.S. Food and Drug Administration granted regular approval of imatinib mesylate tablets (Gleevec®; Novartis Pharmaceuticals Corporation, East Hanover, NJ) for the adjuvant treatment of adult patients following complete gross resection of Kit(+) (CD117(+)) gastrointestinal stromal tumors (GISTs). The recommended dose of imatinib is 400 mg/day administered daily for 3 years. Three hundred ninety-seven patients were enrolled in a randomized adjuvant, multicenter, open label, phase III trial comparing 12 months with 36 months of imatinib treatment. Eligible patients had one of the following: tumor diameter >5 cm and mitotic count >5 per 50 high power fields (HPFs); tumor diameter >10 cm and any mitotic count; tumor of any size with mitotic count >10/50 HPFs; or tumor ruptured into the peritoneal cavity. The primary endpoint was the recurrence-free survival (RFS) interval. The median follow-up for patients without an RFS event was 42 months. There were 84 (42%) RFS events in the 12-month treatment arm and 50 (25%) RFS events in the 36-month treatment arm. Thirty-six months of imatinib treatment led to a significantly longer RFS interval than with 12 months of treatment. The median follow-up for overall survival (OS) evaluation in patients still living was 48 months. Thirty-six months of imatinib treatment led to a significantly longer OS time than with 12 months of imatinib treatment. The most common adverse reactions, as noted in previous imatinib studies, were diarrhea, fatigue, nausea, edema, decreased hemoglobin, rash, vomiting, and abdominal pain.

Current management of gastrointestinal stromal tumors--a comprehensive review

BACKGROUND

Gastrointestinal stromal tumors (GISTs) comprise < 1% of all gastrointestinal (GI) tumors, but GISTs are the most common mesenchymal tumors of the GI tract. Dramatic changes in clinical practice have been observed in the last decade. This review highlights the overall management of GIST and its recent developments.

METHOD

We identified literature by searching Medline and PubMed from January 1995 to December 2011 using the keywords "gastrointestinal stromal tumors", "GIST", "imatinib" and "tyrosine kinase inhibitor". Additional papers were identified by a manual search of the references from the key articles. There were no exclusion criteria for published information to the topics.

RESULTS

For localized primary GISTs, surgical resection is the mainstay of therapy. The 5-year survival rate after complete resection of GISTs is approximately 50%-65%. Many factors including tumor size, mitotic rate, tumor location, kinase mutational status and occurrence of tumor rupture have been extensively studied and proposed to be predictors of survival outcomes. Adjuvant imatinib is proposed as an option for those patients with a substantial risk of relapse. Unresectable metastatic or recurrent GIST can be treated with a tyrosine kinase inhibitor, imatinib, with a remarkable response (50%-70%) and prolonged survival (median progression-free survival: 18-20 months; median overall survival: 51-57 months). The standard approach in the case of tumor progression on 400 mg once per day is to increase the imatinib dose to 400 mg twice per day as permitted by toxicity. Use of a second-line targeted agent, sunitinib, in patients with advanced GIST who fail (or are intolerant of) imatinib therapy is advised.

CONCLUSION

Treatment for GISTs has become increasingly complex because of the growing understanding of its biology. A multidisciplinary team that includes radiologists, medical oncologists, pathologists, and surgeons is paramount for the effective treatment of GIST.

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.

Risk of recurrence of gastrointestinal stromal tumour after surgery: an analysis of pooled population-based cohorts

BACKGROUND

The risk of recurrence of gastrointestinal stromal tumour (GIST) after surgery needs to be estimated when considering adjuvant systemic therapy. We assessed prognostic factors of patients with operable GIST, to compare widely used risk-stratification schemes and to develop a new method for risk estimation.

METHODS

Population-based cohorts of patients diagnosed with operable GIST, who were not given adjuvant therapy, were identified from the literature. Data from ten series and 2560 patients were pooled. Risk of tumour recurrence was stratified using the National Institute of Health (NIH) consensus criteria, the modified consensus criteria, and the Armed Forces Institute of Pathology (AFIP) criteria. Prognostic factors were examined using proportional hazards and non-linear models. The results were validated in an independent centre-based cohort consisting of 920 patients with GIST.

FINDINGS

Estimated 15-year recurrence-free survival (RFS) after surgery was 59·9% (95% CI 56·2-63·6); few recurrences occurred after the first 10 years of follow-up. Large tumour size, high mitosis count, non-gastric location, presence of rupture, and male sex were independent adverse prognostic factors. In receiver operating characteristics curve analysis of 10-year RFS, the NIH consensus criteria, modified consensus criteria, and AFIP criteria resulted in an area under the curve (AUC) of 0·79 (95% CI 0·76-0·81), 0·78 (0·75-0·80), and 0·82 (0·80-0·85), respectively. The modified consensus criteria identified a single high-risk group. Since tumour size and mitosis count had a non-linear association with the risk of GIST recurrence, novel prognostic contour maps were generated using non-linear modelling of tumour size and mitosis count, and taking into account tumour site and rupture. The non-linear model accurately predicted the risk of recurrence (AUC 0·88, 0·86-0·90).

INTERPRETATION

The risk-stratification schemes assessed identify patients who are likely to be cured by surgery alone. Although the modified NIH classification is the best criteria to identify a single high-risk group for consideration of adjuvant therapy, the prognostic contour maps resulting from non-linear modelling are appropriate for estimation of individualised outcomes.

FUNDING

Academy of Finland, Cancer Society of Finland, Sigrid Juselius Foundation and Helsinki University Research Funds.