Molecular response of gastrointestinal stromal tumour after treatment with tyrosine kinase inhibitor imatinib mesylate

The benefit of using CT-perfusion imaging for reliable response monitoring in patients with gastrointestinal stromal tumor (GIST) undergoing treatment with novel targeted agents

Solely size-based response criteria may be unreliable in patients with gastrointestinal stromal tumors (GIST) treated with tyrosine kinase inhibitors, because they typically underestimate responses to treatment. As GISTs are generally hypervascularized and novel targeted drugs knowingly affect angiogenic signaling pathways, perfusion measurements are expected to deliver important information about their efficacy. This pictorial essay illustrates the benefit of using complementary CT-perfusion-based measurements for more accurate evaluation of response to therapy in GIST.

Contrast-enhanced dual-energy CT of gastrointestinal stromal tumors: is iodine-related attenuation a potential indicator of tumor response?

OBJECTIVES

To assess the correlation of true nonenhanced (TNE) and virtually nonenhanced (VNE) images of abdominal dual-energy computed tomography (DECT) in patients with metastatic gastrointestinal stromal tumors (GIST), and further to investigate the correlation of iodine-related attenuation (IRA) of DECT with the Choi criteria.

MATERIAL AND METHODS

Twenty-four consecutive patients (5 women aged 61 ± 10 years) with metastatic GIST underwent DECT of the abdomen (80 kV, 140 kV) using first-generation dual-source computed tomography (CT). All patients had at least one or more liver lesions (median, 4; maximum, 9). Image data were processed with a dedicated DECT software algorithm designed for evaluation of iodine distribution in soft tissue lesions, and VNE CT images were generated. The tumor density (according to Choi criteria) and the maximum transverse diameter of the lesions (according to Response Evaluation Criteria in Solid Tumors [RECIST]) were determined. TNE and VNE lesion attenuation and Choi criteria and IRA were correlated with each other.

RESULTS

A total of 291 liver lesions were evaluated, of which 220 were cystic and 71 were solid. The mean lesion size was 4.5 ± 3.2 cm (1.1-18.7 cm). The mean attenuation of all lesions was significantly higher in the TNE images than in the VNE images (P=0.0001). Pearson statistics revealed an excellent correlation of r=0.843 (P=0.0001) between IRA and Choi criteria for all lesions. DECT showed significantly higher IRA in progressive (23.3 ± 9.5 HU) lesions compared with stable or regressive (17.8 ± 9.1 HU) lesions (P=0.0185). Similarly, the Choi criteria differed significantly between progressive (39.9 ± 12.8 HU) and stable/regressive (31.1 ± 10.3 HU) lesions (P=0.0003).

CONCLUSIONS

DECT is a promising imaging method for the assessment of treatment response in GIST, as IRA might be a more robust response parameter than the Choi criteria. VNE CT data calculated from DECT may eliminate the need for acquisition of a separate unenhanced data set.

Emergency surgery in the era of molecular treatment of solid tumours

In the advancing era of molecular therapy of solid tumours, emergency treatment of complications, such as bowel perforation, haemorrhage, and tumour rupture, is likely to evolve into one of the main challenges of surgical oncology. These complications might be caused by disease progression from resistance to therapy, side-effects of therapy on normal vasculature, and therapeutic induction of excessively responding tumours. This Review outlines the probability and management of emergency operations during molecularly targeted therapy of solid tumours. Special attention is given to advanced gastrointestinal stromal tumours and colorectal cancer, and therapy with imatinib, sunitinib, and bevacizumab.

Assessment of gastrointestinal stromal tumors with computed tomography following treatment with imatinib mesylate

AIM: To evaluate and characterize the patterns of disease progression of metastatic or unresectable gastrointestinal stromal tumor (GIST) treated with imatinib mesylate, and to determine the prognostic significance associated with disease progression.

METHODS: Clinical data and computed tomography (CT) images were retrospectively reviewed in 17 GIST patients who were treated with imatinib mesylate from October 2002 to October 2006. Apart from using size measurement for evaluation of tumor response [Response Evaluation Criteria in Solid Tumors (RECIST) criteria], patterns of CT changes during treatment were evaluated and correlated with clinical data.

RESULTS: There were eight non-responders and nine responders. Five patterns of CT change during treatment were found: focal progression (FP), generalized progression (GP), generalized cystic change (GC), new cystic lesion (NC) and new solid lesion (NS). At the end of study, all non-responders showed GP, whereas responders showed cystic change (GC and NC) and response according to RECIST criteria. Overall survival was significantly better in patients with cystic change or response within the RECIST criteria compared with GP patients (P = 0.0271).

CONCLUSION: Various patterns of CT change in patients with GIST who responded to imatinib mesylate were demonstrated, and might determine the prognosis of the disease. A combination of RECIST criteria and pattern of CT change are proposed for response evaluation in GIST.

Therapeutic procedures for submucosal tumors in the gastrointestinal tract

This review is part three of three and will present an update on the therapeutic options and procedures concerning gastrointestinal (GI) submucosal tumors (SMTs). The aim of this paper is to investigate the treatments of GI SMTs and to present a case of a gastrointestinal stromal tumor (GIST). Literature searches were performed to find information on therapy for GI SMTs. Based on these searches, the optimal therapeutic procedures could be outlined. The choice of treatment of localized tumors is endoscopic resection if possible or, alternatively, laparoscopic resection or surgical resection by an open procedure. However, benign SMTs should only be excised if symptoms are present, and GISTs should be treated with particular precautions. Irresectable or recurrent GISTs may be successfully treated with the tyrosine kinase inhibitor, imatinib.

Gastrointestinal stromal tumors treated with imatinib: monitoring response with contrast-enhanced sonography

OBJECTIVE

The purpose of this study was to evaluate contrast-enhanced Doppler sonography with perfusion software as a predictor of early tumor response to imatinib (Glivec) in c-kit-positive gastrointestinal stromal tumors (GISTs).

SUBJECTS AND METHODS

Thirty patients (59 tumors) with metastases or a recurrence from a GIST were prospectively included in a single-center imaging trial. Contrast-enhanced Doppler sonography was performed with an Aplio scanner the day before (day-1) starting oral treatment (400 mg) and at days 1, 7, 14, 60, 90, and 6 months, 9 months, and 1 year. The percentage of contrast uptake (Levovist or Sonovue) before treatment and at the different stages of follow-up was evaluated by two radiologists. Digitized quantification was performed using Photoshop software. To define the benchmark standard, all patients were rated as responders or nonresponders at 2 and 6 months by a board consisting of oncologists and radiologists who had all clinical and imaging data at their disposal. Changes in the percentage of contrast uptake at each sonographic examination were compared statistically.

RESULTS

A total of 185 examinations were performed. Forty-four lesions in 24 patients were completely evaluated at 2 months, and 29 lesions in 15 patients were completely evaluated at 6 months. Initial contrast uptake at day 1 was predictive of the future response. A strong correlation was found between the decline in tumor contrast uptake at days 7 and 14 and tumor response (p < 10(-4)).

CONCLUSION

Contrast-enhanced Doppler sonography is a noninvasive imaging technique that allows the early prediction of tumor response in c-kit-positive GIST treated with Glivec.

[Surgical considerations for gastrointestinal stroma tumor]

Gastrointestinal stroma tumors (GIST), an abdominal stroma entity, are characterized by a gain-in-function mutation in the c-kit proto-oncogen (CD117). Initial treatment should aim at complete removal of the primary tumor (R0 resection), which almost never develops lymphatic metastases. Distant metastatic spread mainly involves the peritoneal cavity and the liver. In patients with metastatic disease, treatment with the tyrosine kinase inhibitor imatinib mesylate is indicated and very effective. Systemic chemotherapy and external beam radiation must be considered ineffective. Patients requiring multivisceral resection for primary tumor removal quickly develop tumor recurrence and could benefit from preoperative treatment with imatinib. To assess the response to treatment, 18F-FDG positron emission tomography or gadolinium-enhanced magnetic resonance imaging have proven helpful, as the conventional criteria of tumor shrinkage according to WHO standards are rarely met. Primary tumors are classified into four risk categories according to size and mitotic activity. The possible advantages of adjuvant treatment are currently under investigation through international randomized trials. Patients who develop extensive remission of metastatic disease should be evaluated individually for resection of the tumor remnants. Even the resection of single progressive lesions (newly developed mutations) should be considered in carefully selected patients if the remaining tumor can be controlled by continued imatinib treatment.

Response evaluation in gastrointestinal stromal tumours treated with imatinib: misdiagnosis of disease progression on CT due to cystic change in liver metastases

Imatinib is a highly effective treatment for patients with metastatic gastrointestinal stromal tumours (GIST). In most instances, response to imatinib treatment is assessed with CT. We present two cases where CT demonstrated the appearance of new low density liver lesions after 8-12 weeks of imatinib treatment. While this finding is consistent with progressive disease due to new lesions appearing at a previously uninvolved site, we hypothesise that the appearance of new liver lesions is in fact due to cystic change within previously occult, solid metastases. These untreated solid metastases were not visible on conventional portal phase CT due to their small size and vascular nature. Our hypothesis is supported by the observation that extrahepatic sites of disease had reduced in size over the same period of imatinib treatment and by the subsequent disease outcomes of these two cases. One patient, who continued imatinib because of significant symptomatic improvement despite the CT findings, remained stable on the same dose of imatinib for 18 months. The other patient, whose disease progressed when imatinib was withdrawn, had a dramatic response to treatment when imatinib was restarted at the same dose 2 years later. It is important that radiologists and oncologists who are involved in the management of GIST recognize that the appearance of new, low-density liver lesions on CT may represent a response to treatment. This finding must be correlated with symptomatic response and with tumour sites outside the liver before erroneously withdrawing effective imatinib treatment.

RECIST revisited: a review of validation studies on tumour assessment

The response evaluation criteria in solid tumours (RECIST) was developed in the late 1990s to replace the WHO criteria for response evaluation. The new criteria included important changes such as unidimensional tumour measurement, selection of target lesions with a minimum size, details concerning imaging modalities and a new threshold for assignment of objective progression. RECIST was published in February 2000 and very quickly came into operation first in clinical trials performed under the auspices of EORTC, US NCI or NCI Canada Clinical Trials Group but was adopted quickly thereafter by the entire cancer clinical research community. As several key features of RECIST were based on analysis of retrospective clinical data, it was felt important to carefully monitor the implementation of the guidelines and stimulate prospective validation studies. This paper reviews the literature that has been published on RECIST from 2000 up to November 2005. In total 60 papers and ASCO, abstracts directly refer to research studies or reviews related to RECIST and its implementation. Amongst the 60 references identified for this review, 11 papers refer to validation studies (seven prospective and four retrospective), six papers refer to the comparison of unidimensional measurements versus bi or tri-dimensional measurements, 12 papers address issues raised with the implementation of RECIST in Mesothelioma and Gastro-Intestinal Stromal Tumours and four papers report on an adaptation of RECIST for specific tumour types. In general, RECIST has been well received by the scientific community and most validation studies fully support the implementation of the new criteria. As expected, however, some issues have been identified. In keeping with the mathematical differences in definition of progression, RECIST delays the identification of progression as compared to WHO criteria in some instances. RECIST criteria are not easily applicable in some types of trials such as those in paediatric tumours and in mesothelioma. Furthermore, anatomical changes in the tumour as described by RECIST may be detected later than functional changes in some circumstances, as for example in Gastro-Intestinal Stromal Tumours treated with Imatinib. However, there is no other universal method of tumour assessment as yet and functional imaging methods have not been validated and will not be widely available for some time. The findings of this review, together with experience acquired thus far and the results of some ongoing research projects, have paved the way for RECIST 2.0 to be hopefully announced later this year.

Pathological complete response in advanced gastrointestinal stromal tumor after imatinib therapy

Gastrointestinal stromal tumor (GIST) is a rare neoplasm exhibiting, in most cases, mutations of c-kit. Recently it has been demonstrated that a majority of GIST patients with c-kit mutations respond to therapy with imatinib, a c-kit tyrosine kinase inhibitor. Although the response rate in patients treated with imatinib in prospective clinical studies is above 50%, complete response is rare, and the data on the use of imatinib as neoaduvant therapy facilitating radical surgery is still scanty. Here, we report on a patient with metastatic gastric GIST who underwent surgery after 6 months of imatinib therapy. No tumor cells were detected on pathological examination of resection specimen. This case report indicates that a pathological complete response could be achieved with imatinib therapy in patients with GIST, but a wider experience and longer follow-up is necessary to appreciate the prognostic significance of pathological complete response in GIST.

Follow-up of gastro-intestinal stromal tumours (GIST) during treatment with imatinib mesylate by abdominal MRI

Typical MRI findings for gastro-intestinal stromal tumours (GIST) under treatment with imatinib were evaluated. MRI was performed in 45 patients (25 responders, 20 non-responders) with metastatic or locally advanced, unresectable GIST. Target lesions were selected and re-evaluated after 2, 4, and 6 months of therapy with imatinib. The target tumour response (TTR) was classified according to RECIST criteria. TTR, signal intensity in the centre and border of the lesion and the presence and the extension of a hypervascular rim were analysed. The mean diameter of the marker lesions decreased significantly (P<0.001) from 7.1+/-2.6 cm to 5.9+/-2.3 cm after 6 months. Accuracy of RECIST criteria was 51%, 69% and 73% on MRI 2, 4 and 6 months for response assessment. In addition, responders had higher signal-to-noise ratios on T2-w images after 2 months (P<0.05) and a decrease of vascularised areas in the lesion 4 and 6 months after treatment (each P<0.01), when compared with non-responders. Beyond the size measurement for response assessment, MRI provides additional information of tumour response using SI of T2-w images and quantification of vascularised areas of GIST manifestations.