RECIST vs. WHO: prospective comparison of response criteria in an EORTC phase II clinical trial investigating ET-743 in advanced soft tissue sarcoma

Evaluation of circulating cell-free DNA as a molecular monitoring tool in patients with metastatic cancer

The clinical decisions made when treating patients with metastatic cancer require knowledge of the current tumor extent and response to therapy. For the majority of solid tumors, a response assessment, which is based on imaging, is used to guide these decisions. However, measuring serum protein biomarkers (i.e. tumor markers) may be of additional use. Furthermore, tumor markers exhibit variable specificity and sensitivity and cannot therefore be solely relied upon when making decisions regarding cancer treatment. Therefore, there is a clinical requirement for the identification of specific, sensitive and quantitative biomarkers. In recent years, circulating cell-free DNA (cfDNA) and mutation-specific circulating cell-free tumor DNA (cftDNA) have been identified as novel potential biomarkers. In the current study, cfDNA and cftDNA were compared using imaging-based staging and current tumor markers in 15 patients with metastatic colorectal, pancreatic or breast cancer. These patients were treated at the Third Medical Department of Paracelsus Medical University Salzburg (Austria). The results of the current study demonstrated a statistically significant correlation between the concentration changes of cfDNA and cftDNA and response to treatment, which was assessed by imaging. A correlation was not indicated with current clinically used tumor markers, including carcinoembryonic antigen, carcinoma antigen 15-3 and carcinoma antigen 19-9. The present study also indicated a correlation between cfDNA and cftDNA and the tumor volume of metastatic lesions, which was not observed with the current clinically used tumor markers. In conclusion, cfDNA and cftDNA exhibit the potential to become novel biomarkers for the response assessment following cancer treatment, and may serve as a tool for the estimation of tumor volume. The current study further supports the increasingly important role of cfDNA and cftDNA as new monitoring tools for use during cancer therapy.

Development of an algorithm for evaluating the impact of measurement variability on response categorization in oncology trials

BACKGROUND

Radiologic assessments of baseline and post-treatment tumor burden are subject to measurement variability, but the impact of this variability on the objective response rate (ORR) and progression rate in specific trials has been unpredictable on a practical level. In this study, we aimed to develop an algorithm for evaluating the quantitative impact of measurement variability on the ORR and progression rate.

METHODS

First, we devised a hierarchical model for estimating the distribution of measurement variability using a clinical trial dataset of computed tomography scans. Next, a simulation method was used to calculate the probability representing the effect of measurement errors on categorical diagnoses in various scenarios using the estimated distribution. Based on the probabilities derived from the simulation, we developed an algorithm to evaluate the reliability of an ORR (or progression rate) (i.e., the variation in the assessed rate) by generating a 95% central range of ORR (or progression rate) results if a reassessment was performed. Finally, we performed validation using an external dataset. In the validation of the estimated distribution of measurement variability, the coverage level was calculated as the proportion of the 95% central ranges of hypothetical second readings that covered the actual burden sizes. In the validation of the evaluation algorithm, for 100 resampled datasets, the coverage level was calculated as the proportion of the 95% central ranges of ORR results that covered the ORR from a real second assessment.

RESULTS

We built a web tool for implementing the algorithm (publicly available at http://studyanalysis2017.pythonanywhere.com/ ). In the validation of the estimated distribution and the algorithm, the coverage levels were 93 and 100%, respectively.

CONCLUSIONS

The validation exercise using an external dataset demonstrated the adequacy of the statistical model and the utility of the developed algorithm. Quantification of variation in the ORR and progression rate due to potential measurement variability is essential and will help inform decisions made on the basis of trial data.

Prospective comparison of various radiological response criteria and pathological response to preoperative chemotherapy and survival in operable high-grade soft tissue sarcomas in the Japan Clinical Oncology Group study JCOG0304

BACKGROUND

Soft tissue sarcomas (STS) are rare malignant tumors. The efficacy of preoperative chemotherapy for STS is evaluated using various tumor size-based radiological response criteria. However, it is still unclear which set of criteria would show the best association with pathological response and survival of the patients with STS.

METHODS

We compared radiological responses to preoperative chemotherapy for operable STS by the Response Evaluation Criteria in Solid Tumors (RECIST), modified RECIST, World Health Organization criteria, Japanese Orthopaedic Association criteria, and modified Choi criteria and analyzed the association with pathological response and survival using the data from the Japan Clinical Oncology Group (JCOG) study JCOG0304, a phase II clinical trial evaluating the efficacy of perioperative chemotherapy for STS in the extremities.

RESULTS

Seventy eligible patients in JCOG0304 were analyzed. The results demonstrated that none of the size-based radiological response criteria showed significant association with pathological response to preoperative chemotherapy for STS. The difference between overall survival of the patients assessed as partial response and stable disease/progressive disease by RECIST was not significant (hazard ratio 1.37, p = 0.63), and calculated C-index was 0.50. All other response criteria also could not exhibit significant association between radiological responses and survival.

CONCLUSION

In the present study, none of the radiological response criteria analyzed demonstrated association of response to preoperative chemotherapy with pathological response or survival of the patients with operable STS. Further prospective investigation is required to develop criteria to evaluate not only tumor shrinkage but biological effects of preoperative chemotherapy for the patients with localized STS.

TRIAL REGISTRATION

UMIN Clinical Trials Registry C000000096. Registered 30 August, 2005 (retrospectively registered).

A noninterventional, multicenter, prospective phase IV study of trabectedin in patients with advanced soft tissue sarcoma

This prospective, noninterventional study is the first phase IV trial designed to evaluate trabectedin in patients with advanced soft tissue sarcoma in real-life clinical practice across Europe. To be included in the study, patients must have received more than or equal to one cycle of trabectedin and be currently on treatment. The primary endpoint was progression-free survival as defined by investigators. The secondary endpoints included objective response rate, disease control rate, time to progression and the growth modulation index (GMI), overall survival, and an assessment of the cancer-related symptoms and safety. A total of 218 patients from 41 European centers were evaluated. Patients received a median of six cycles per patient, mostly on an outpatient basis (n=132; 60.6%). The median progression-free survival was 5.9 months, with 70 and 49% of patients free from progression at 3 and 6 months after treatment, respectively. Three (1.4%) patients achieved a complete response and 55 (25.2%) patients achieved a partial response for an objective response rate of 26.6%. A total of 85 (39.0%) patients had disease stabilization for a disease control rate of 65.6%. The median GMI was 0.8, with 5.1 and 38.8% of patients with a GMI of greater than 1.1 to less than 1.33 and greater than or equal to 1.33, respectively. The median overall survival was 21.3 months. Febrile neutropenia (2.3% of patients), neutropenia, nausea, and pneumonia (1.4% each) were the most common trabectedin-related grade 3/4 serious adverse drug reactions. Trabectedin confers clinically meaningful long-term benefits to patients with multiple soft tissue sarcoma histotypes, being either comparable or better than those observed previously in clinical trials, and with a manageable safety profile.

Long-Term Survival According to Histology and Radiologic Response to Preoperative Chemotherapy in 126 Patients Undergoing Resection of Non-GIST Sarcoma Liver Metastases

BACKGROUND

Non-gastrointestinal stromal tumor sarcomas (NGSs) have heterogeneous histology, and this heterogeneity may lead to uncertainty regarding the prognosis of patients with liver metastases from NGS (NGSLM) and decision regarding their surgical management. Furthermore, the role of preoperative chemotherapy in treatment of NGSLM remains poorly defined. We investigated long-term survival and its correlation to response to preoperative chemotherapy in patients with NGSLM.

PATIENTS AND METHOD

Patients who underwent liver resection for NGSLM during 1998-2015 were identified. Clinical, histopathologic, and survival data were analyzed. Multivariate analysis was performed using a Cox proportional hazards model.

RESULTS

126 patients [62 (49%) with leiomyosarcoma] were included. Five-year overall survival (OS) and recurrence-free survival (RFS) rates were 49.3 and 14.9%, respectively. Survival did not differ by histologic subtype, primary tumor location, or use of preoperative or postoperative chemotherapy. NGSLM ≥ 10 cm and extrahepatic metastases at NGSLM diagnosis were the only independent risk factors for OS. In the 83 (66%) patients with metachronous NSGLM, disease-free interval > 6 months was associated with improved OS and RFS. Among the 65 patients (52%) who received preoperative chemotherapy, radiologic response according to Choi criteria specifically was associated with improved OS (p = 0.04), but radiologic response according to RECIST 1.1 criteria was not.

CONCLUSIONS

Resection of NGSLM led to a 5-year OS rate of 49%, independent of histologic subtype and primary tumor location. Choi criteria (which take into account tumor density) are superior to RECIST 1.1 in assessing radiologic response and should be used to assess response to preoperative chemotherapy.

Disseminated and late metastatic disease from nasal pit leiomyosarcoma after radical surgical resection. Case report of a singular presentation of a rare disease

Background

Leiomyosarcoma of the head and neck is a rare cancer with high local aggressiveness. Radical surgery and adjuvant treatment offer the best chance for cure, nonetheless 5-years recurrence rate remains high. Despite international guidelines are available for soft tissue sarcomas, no recommendations are specifically endorsed for leiomyosarcoma of the head and neck, due to the rarity of its presentation and consequently scarcity of data on long-term outcome.

Case presentation

A 50-year old woman, operated 10 years before for leiomyosarcoma of the nasal pit and with negative 5-years follow-up, was admitted to our ward for impairment of the hepatic function. Total-body CT scan detected multiple localizations at lungs, kidneys, pancreas, bones, muscles, lymph nodes and thyroid. The pathologic report after lung biopsy confirmed the diagnosis of metastasis from leiomyosarcoma and the patients was scheduled for first line chemo-radiotherapy.

Conclusions

Despite adequate primary treatment, distant and disseminated metastatic disease may be not excluded in leiomyosarcoma of the head and neck.

Magnetic resonance imaging evaluation of residual tumors in breast cancer after neoadjuvant chemotherapy: surgical implications

BACKGROUND

Magnetic resonance imaging (MRI) can be used to guide breast cancer surgery with breast conservation for large tumors with a substantially reduced size after neoadjuvant chemotherapy (NAC).

PURPOSE

To evaluate the value of dynamic contrast-enhanced MRI (DCE-MRI) for measuring residual tumor size and enhancement patterns following preoperative NAC.

MATERIAL AND METHODS

Eighty-nine patients with breast cancer underwent breast DCE-MRI; 38 patients (39 lesions) were treated with NAC and examined for residual disease following therapy. Two patients were excluded because surgery had been performed >2 weeks after the final MR examination. Thus, we correlated the DCE-MRI results of 36 patients (37 lesions) with postoperative histopathological findings. Residual disease was confirmed by more enhancement compared to normal glandular tissue at the initial tumor site. Residual tumor size on DCE-MRI was compared with postoperative pathology findings. Tumor enhancement patterns on DCE-MRI were analyzed and correlated with pathological classification.

RESULTS

MRI revealed 34 cases of residual tumors, with two false positives and one false negative. Pathological and MR measurements were correlated (r = 0.793). The correlation of mass enhancement size (r = 0.87, n = 14) with pathology and DCE-MRI was higher than for non-mass-like enhancement (NME) (r = 0.735, n = 23). The distribution of pathologic classification was significantly different between different MRI enhancement patterns (P = 0.006). Mass enhancement had higher cellularity than NME.

CONCLUSION

MRI is useful for evaluating residual carcinoma following NAC. Mass enhancement with higher cellularity after NAC can be evaluated more accurately, which is suitable for evaluating lumpectomy. However, other approaches are required for NME, which has lower cellularity.

Efficacy of octreotide long-acting repeatable in neuroendocrine tumors: RADIANT-2 placebo arm post hoc analysis

Somatostatin analogues (SSA) have demonstrated antiproliferative activity in addition to efficacy for carcinoid symptom control in functional neuroendocrine tumors (NET). A post hoc analysis of the placebo arm of the RAD001 In Advanced Neuroendocrine Tumors-2 (RADIANT-2) study was conducted to assess the efficacy of octreotide long-acting repeatable (LAR) on progression-free survival (PFS) and overall survival (OS) estimated using the Kaplan-Meier method. Out of 213 patients randomized to placebo plus octreotide LAR in RADIANT-2, 196 patients with foregut, midgut, or hindgut NET were considered for present analysis. Of these, 41 patients were SSA-treatment naïve and 155 had received SSA therapy before study entry. For SSA-naïve patients, median PFS by adjudicated central review was 13.6 (95% CI 8.2-22.7) months. For SSA-naïve patients with midgut NET (n=24), median PFS was 22.2 (95% CI 8.3-29.5) months. For patients who had received SSA previously, the median PFS was 11.1 (95% CI 8.4-14.3) months. Among the SSA-pretreated patients who had midgut NET (n=119), the median PFS was 12.0 (95% CI 8.4-19.3) months. Median OS was 35.8 (95% CI 32.5-48.9) months for patients in the placebo plus octreotide LAR arm; 50.6 (36.4 - not reached) months for SSA-naïve patients and 33.5 (95% CI 27.5-44.7) months for those who had received prior SSA. This post hoc analysis of the placebo arm of the large phase 3 RADIANT-2 study provides data on PFS and OS among patients with progressive NET treated with octreotide therapy.

Assessment of treatment response using PET

This article reviews the major treatment response evaluation guidelines in the domain of cancer imaging and how the potential of PET imaging, particularly with fluorodeoxyglucose, is increasingly explored in this important aspect of cancer management. Certain disease-specific response criteria (such as in lymphoma) are also reviewed with emphasis on the changes made over time and the main areas of concern in PET interpretation. The major present clinical applications are illustrated and potential new areas are discussed with regard to clinical applications in the future. Finally, the evolving role of newer and novel PET metrics, which hold promise in treatment response evaluation, is illustrated with examples.

A radiologist's guide to treatment response criteria in oncologic imaging: anatomic imaging biomarkers

OBJECTIVE

The purpose of this article is to describe the imaging biomarkers of treatment response and provide an overview of anatomic imaging biomarkers.

CONCLUSION

Imaging biomarkers of treatment response have evolved into the primary endpoint of response in most phase 2 studies. Anatomic imaging biomarkers are applied to depict change in tumor size in response to treatment and are currently the most commonly applied method of treatment response evaluation.

Phase III, multicenter, randomized trial of maintenance chemotherapy versus observation in patients with metastatic breast cancer after achieving disease control with six cycles of gemcitabine plus paclitaxel as first-line chemotherapy: KCSG-BR07-02

PURPOSE

The primary purpose of our study was to evaluate whether maintenance chemotherapy with paclitaxel/gemcitabine (PG) was superior to observation in improving progression-free survival (PFS) in patients with metastatic breast cancer (MBC) who achieved disease control with an initial six cycles of PG as their first-line treatment.

PATIENTS AND METHODS

The study was a prospective, randomized, multicenter, phase III trial. Patients MBC with who achieved disease control after six cycles of PG chemotherapy were randomly assigned to maintenance chemotherapy or observation until progression.

RESULTS

Of 324 patients from 10 centers enrolled, 231 patients with MBC exhibited disease control (complete response + partial response + stable disease) with first-line PG and were randomly assigned to maintenance chemotherapy (n = 116) or observation (n = 115). The median age was 48 years (range, 28 to 76 years), median follow-up was 33 months, and median number of chemotherapy cycles in the maintenance group after random assignment was six. The median PFS time after random assignment was longer in the maintenance group than in the observation group (7.5 v 3.8 months, respectively; P = .026). The median overall survival (OS) time was longer in the maintenance group than in the observation group (32.3 v 23.5 months, respectively; P = .047). The rate of grade 3 or higher neutropenia after random assignment was higher in the maintenance group than in the observation group (61% v 0.9%, respectively; P < .001).

CONCLUSION

In patients with MBC who achieved disease control with an initial six cycles of PG chemotherapy, maintenance PG chemotherapy resulted in better PFS and OS compared with observation.

The role of magnetic resonance imaging in assessing residual disease and pathologic complete response in breast cancer patients receiving neoadjuvant chemotherapy: a systematic review

OBJECTIVES

This systematic review aimed to assess the role of magnetic resonance imaging (MRI) in evaluating residual disease extent and the ability to detect pathologic complete response (pCR) after neoadjuvant chemotherapy for invasive breast cancer.

METHODS

PubMed, the Cochrane Library, MEDLINE, and Embase databases were searched for relevant studies published until 1 July 2012. After primary selection, two reviewers independently assessed the content of each eligible study using a standardised extraction form and pre-defined inclusion and exclusion criteria.

RESULTS

A total of 35 eligible studies were selected. Correlation coefficients of residual tumour size assessed by MRI and pathology were good, with a median value of 0.698. Reported sensitivity, specificity, positive predictive value and negative predictive value for predicting pCR with MRI ranged from 25 to 100 %, 50-97 %, 47-73 % and 71-100 %, respectively. Both overestimation and underestimation were observed. MRI proved more accurate in determining residual disease than physical examination, mammography and ultrasound. Diagnostic accuracy of MRI after neoadjuvant chemotherapy could be influenced by treatment regimen and breast cancer subtype.

CONCLUSIONS

Breast MRI accuracy for assessing residual disease after neoadjuvant chemotherapy is good and surpasses other diagnostic means. However, both overestimation and underestimation of residual disease extent could be observed.

MAIN MESSAGES

• Breast MRI accuracy for assessing residual disease is good and surpasses other diagnostic means. • Correlation coefficients of residual tumour size assessed by MRI and pathology were considered good. • However, both overestimation and underestimation of residual disease were observed. • Diagnostic accuracy of MRI seems to be affected by treatment regimen and breast cancer subtype.

Outcomes of phase II clinical trials with single-agent therapies in advanced/metastatic non-small cell lung cancer published between 2000 and 2009

PURPOSE

We analyzed the outcomes of single-agent phase II clinical trials in non-small cell lung cancer (NSCLC) to determine trial parameters that predicted clinical activity.

EXPERIMENTAL DESIGN

Data on response rate (RR), progression-free survival (PFS), and overall survival (OS) from all English language, single-agent phase II trials in advanced/metastatic NSCLC indexed by PubMed (January 2000 through December 2009) were abstracted.

RESULTS

A total of 143 single-agent phase II trials (7,701 patients) were identified. The median RR was 10%, PFS 2.8 months, and OS 7.6 months. RR and PFS correlated with OS (r = 0.46, P < 0.001, r = 0.52, P < 0.001, respectively) and RR correlated with PFS (r = 0.61, P < 0.001). Treatment arms enriched for patients with molecular targets had a higher median RR (48.8% vs. 9.7%, P = 0.005), longer median PFS (6 vs. 2.8 months, P = 0.005), and OS (11.3 vs. 7.5 months, P = 0.05) as compared with those of unselected patients. In multivariate analysis, only studies enriched for patients with molecular targets or including drugs that eventually gained FDA/EMA approval were associated with a higher RR, and longer PFS/OS.

CONCLUSIONS

In phase II trials in NSCLC, RR and PFS correlated with OS. Studies enriched for patients with putative molecular drug targets were associated with higher therapeutic benefit as compared with those of unselected populations.

Intra- and inter-observer variability in measurement of target lesions: implication on response evaluation according to RECIST 1.1

Background

The assessment of cancer treatment in oncological clinical trials is usually based on serial measurements of tumours’ size according to the Response Evaluation Criteria in Solid Tumours (RECIST) guidelines. The aim of our study was to evaluate the variability of measurements of target lesions by readers as well as the impact on response evaluation, workflow and reporting.

Patients and methods

Twenty oncologic patients were included to the study with CT examinations from thorax to pelvis performed at a 64 slices CT scanner. Four readers defined and measured the size of target lesions independently at baseline and follow-up with PACS (Picture Archiving and Communication System) and LMS (Lesion Management Solutions, Median technologies, Valbonne Sophia Antipolis, France), according to the RECIST 1.1 criteria. Variability in measurements using PACS or LMS software was established with the Bland and Altman approach. The inter- and intra-observer variabilities were calculated for identical lesions and the overall response per case was determined. In addition, time required for evaluation and reporting in each case was recorded.

Results

For single lesions, the median intra-observer variability ranged from 4.9–9.6% (mean 5.9%) and the median inter-observer variability from 4.3–11.4% (mean 7.1%), respecting different evaluation time points, image systems and observers. Nevertheless, the variability in change of Δ sum longest diameter (LD), mandatory for classification of the overall response, was 24%. The overall response evaluation assessed by a single respectively different observer was discrepant in 6.3% respectively 12% of the cases compared with the mean results of multiple observers. The mean case evaluation time was 286s vs. 228s at baseline and 267s vs. 196s at follow-up for PACS and LMS, respectively.

Conclusions

Uni-dimensional measurements of target lesions show low intra- and inter-observer variabilities, but the high variability in change of Δ sum LD shows the potential for misclassification of the overall response according to the RECIST 1.1 guidelines. Nevertheless, the reproducibility of RECIST reporting can be improved for the case assessment by a single observer and by mean results of multiple observers. Case-based evaluation time was shortened up to 27% using custom software.

Response to radiation therapy in adrenocortical carcinoma

INTRODUCTION

Adrenocortical carcinoma (ACC) is a rare disease which is considered resistant to many treatments. The role of radiotherapy in ACC remains unclear. In general radiotherapy is thought to be ineffective for the treatment of ACC, and therefore not often used. However, recent reports suggest the opposite. The aim of this study was to perform a retrospective analysis to evaluate the application of radiotherapy in Dutch ACC patients, and to determine the occurrence of response.

MATERIALS AND METHODS

The Dutch ACC Registry (no.=159) was screened for patients who had received radiotherapy between 1990 and 2008. Tumor response evaluation was performed according to the Response Evaluation Criteria In Solid Tumors (RECIST).

RESULTS

Only 13 patients (8% of registered patients) had received radiation therapy of whom 6 were irradiated for the palliation of painful bone metastases. In all patients this radiation resulted in pain relief. Three patients received adjuvant tumor bed radiation after resection. Four patients were radiated on irresectable tumor recurrence or tumor metastases. Two patients died soon after radiation therapy and therefore follow-up information regarding tumor response after radiation therapy of 2 patients was available. Interestingly, partial tumor response according to RECIST criteria, was observed in both patients.

CONCLUSION

ACC can be sensitive to radiotherapy and should be considered in the treatment of advanced ACC, particularly in worrisome lesions. The role of radiotherapy in advanced ACC is to complement a systemic treatment such as mitotane or classic cytotoxic agents.

Tolerability, efficacy, and safety of pegylated liposomal Doxorubicin in combination with Carboplatin versus gemcitabine-Carboplatin for the treatment of platinum-sensitive recurrent ovarian cancer: a systematic review

OBJECTIVE

To compare the tolerability, efficacy, and safety profiles of pegylated liposomal doxorubicin in combination with carboplatin (PLD-Carbo) with those of gemcitabine-carboplatin (Gem-Carbo) for the treatment of patients with platinum-sensitive recurrent ovarian cancer (PSROC) by reviewing the published literature.

METHODS

Using the PubMed database, a systematic review of peer-reviewed literature published between January 2000 and September 2009 was undertaken to identify studies related to the treatment of patients with PSROC with PLD-Carbo or Gem-Carbo. Studies reporting either response rate, progression-free survival (PFS), and/or overall survival (OS) were included. Treatment regimens, efficacy endpoints, and safety profiles were compared between the two combination therapies.

RESULTS

Ten studies evaluating 608 patients (PLD-Carbo: 5 studies, 278 patients; Gem-Carbo: 5 studies, 330 patients) were identified. The mean planned doses were: PLD, 34.8 mg/m(2) and Gem, 993 mg/m(2). The dose intensity reported in Gem trials was lower (75% of the planned dose) than the dose intensity reported in PLD trials (93.7% of the planned dose), suggesting better tolerability for the PLD-Carbo regimen. Among patients receiving PLD-Carbo, 60.2% achieved a response (complete, 27.0%; partial, 33.2%), versus 51.4% of patients treated with Gem-Carbo (complete, 19.2%; partial, 32.2%). The median PFS times were 10.6 months and 8.9 months in the PLD-Carbo and the Gem-Carbo populations, respectively. The median OS was longer for the PLD-Carbo regimen (27.1 months) than for the Gem-Carbo regimen (19.7 months). The hematological safety profiles were comparable in the two groups, although grade III or IV anemia (PLD-Carbo, 13.6%; Gem-Carbo, 24.5%) and neutropenia (PLD-Carbo, 45.5%; Gem-Carbo, 62.9%) were more common in patients receiving Gem-Carbo.

CONCLUSION

Results from this systematic analysis of peer-reviewed literature suggest that PLD-Carbo therapy is a rational alternative to Gem-Carbo for the treatment of patients with PSROC.

Oncolytic adenovirus coding for granulocyte macrophage colony-stimulating factor induces antitumoral immunity in cancer patients

Granulocyte macrophage colony-stimulating factor (GMCSF) can mediate antitumor effects by recruiting natural killer cells and by induction of tumor-specific cytotoxic T-cells through antigen-presenting cells. Oncolytic tumor cell-killing can produce a potent costimulatory danger signal and release of tumor epitopes for antigen-presenting cell sampling. Therefore, an oncolytic adenovirus coding for GMCSF was engineered and shown to induce tumor-specific immunity in an immunocompetent syngeneic hamster model. Subsequently, 20 patients with advanced solid tumors refractory to standard therapies were treated with Ad5-D24-GMCSF. Of the 16 radiologically evaluable patients, 2 had complete responses, 1 had a minor response, and 5 had disease stabilization. Responses were frequently seen in injected and noninjected tumors. Treatment was well tolerated and resulted in the induction of both tumor-specific and virus-specific immunity as measured by ELISPOT and pentamer analysis. This is the first time that oncolytic virus-mediated antitumor immunity has been shown in humans. Ad5-D24-GMCSF is promising for further clinical testing.

Response rates: a valuable signal of promising activity?

A main criterion to identify activity in phase II studies is the response rates achieved in a well-defined subset of patients. The response could be defined as a measure of tumor shrinkage. For 30 years, metric methods have been used to assess this response. The World Health Organization was the first organization to propose a unified definition for response status. Over time, the latter evolved and 10 years ago an international consensus panel proposed the Response Evaluation Criteria in Solid Tumors criteria. Although these guidelines for response assessment have limitations and biases, they have nevertheless been proven useful and advantageous. This article reviews those criteria and describes their use.

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

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

Absence of progression as assessed by response evaluation criteria in solid tumors predicts survival in advanced GI stromal tumors treated with imatinib mesylate: the intergroup EORTC-ISG-AGITG phase III trial

PURPOSE

From February 2001 to February 2002, 946 patients with advanced GI stromal tumors (GISTs) treated with imatinib were included in a controlled EORTC/ISG/AGITG (European Organisation for Research and Treatment of Cancer/Italian Sarcoma Group/Australasian Gastro-Intestinal Trials Group) trial. This analysis investigates whether the response classification assessed by RECIST (Response Evaluation Criteria in Solid Tumors), predicts for time to progression (TTP) and overall survival (OS).

PATIENTS AND METHODS

Per protocol, the first three disease assessments were done at 2, 4, and 6 months. For the purpose of the analysis (landmark method), disease response was subclassified in six categories: partial response (PR; > 30% size reduction), minor response (MR; 10% to 30% reduction), no change (NC) as either NC- (0% to 10% reduction) or NC+ (0% to 20% size increase), progressive disease (PD; > 20% increase/new lesions), and subjective PD (clinical progression).

RESULTS

A total of 906 patients had measurable disease at entry. At all measurement time points, complete response (CR), PR, and MR resulted in similar TTP and OS; this was also true for NC- and NC+, and for PD and subjective PD. Patients were subsequently classified as responders (CR/PR/MR), NC (NC+/NC-), or PD. This three-class response categorization was found to be highly predictive of further progression or survival for the first two measurement points. After 6 months of imatinib, responders (CR/PR/MR) had the same survival prognosis as patients classified as NC.

CONCLUSION

RECIST perfectly enables early discrimination between patients who benefited long term from imatinib and those who did not. After 6 months of imatinib, if the patient is not experiencing PD, the pattern of radiologic response by tumor size criteria has no prognostic value for further outcome. Imatinib needs to be continued as long as there is no progression according to RECIST.

Intra-tumoural extra-cellular pH: a useful parameter of response to chemotherapy in syngeneic tumour lines

Reliable surrogate markers of response to anticancer therapy remain a desirable tool for preclinical modelling and clinical practice in oncology. Clinical evaluation is relatively unreliable when attempting to assess rapidly and prospectively the outcome of treatment. Fluxes in released or circulating tumour marker levels are a useful but inconsistent marker of cytotoxic response. Serial measurement of circulating tumour cells appears to have some utility as a surrogate marker, but assay systems are expensive, and many cancers are not associated with the presence of circulating tumour cells. Because tissue breakdown is associated with release of nucleic acids and other cellular products, we reasoned that serial measurement of intra-tumoural pH may correlate with the extent of tumour lysis, and thus with outcomes of cytotoxic chemotherapy. Doxorubicin-sensitive and doxorubicin-resistant sublines of P388 murine monocytic leukaemia in C57BL/6 mice were treated with increasing concentrations of doxorubicin. Tumours were serially measured by conventional bi-dimensional methods and pH was sampled using a bevelled tip electrode. Mean and median pH changes were statistically different in responsive and resistant tumours, and amplitude of change correlated with long-term responses to doxorubicin. Serial sampling of pH in tumour masses may provide a useful surrogate of long-term response to chemotherapy.

Evaluation of tumor response after locoregional therapies in hepatocellular carcinoma: are response evaluation criteria in solid tumors reliable?

BACKGROUND

Evaluation of response to treatment is a key aspect in cancer therapy. Response Evaluation Criteria in Solid Tumors (RECIST) are used in most oncology trials, but those criteria evaluate only unidimensional tumor measurements and disregard the extent of necrosis, which is the target of all effective locoregional therapies. Therefore, the European Association for the Study of the Liver (EASL) guidelines recommended that assessment of tumor response should incorporate the reduction in viable tumor burden. The current report provides an assessment of the agreement/concordance between both RECIST and the EASL guidelines for the evaluation of response to therapy.

METHODS

The authors evaluated a cohort of 55 patients within prospective studies, including 24 patients with hepatocellular carcinoma who underwent transarterial chemoembolization (TACE) with drug eluting beads (DEB-TACE) and 31 patients who underwent percutaneous ablation (percutaneous ethanol injection [PEI]/radiofrequency [RF]). Triphasic helical computed tomography scans were performed at baseline, at 1 month, and at 3 months after procedure, and 2 independent radiologists evaluated tumor response.

RESULTS

Evaluating response according to RECIST criteria, no patients achieved a complete response (CR), 21.8% of patients achieved a partial response (PR) (none in the PEI/RF group), 47.3% of patients had stable disease (SD), and 30.9% of patients had progressive disease (PD). When response was evaluated according to the EASL guidelines, 54.5% of patients achieved a CR, 27.3% of patients achieved a PR, 3.6% of patients had SD, and 14.5% had PD. The kappa coefficient was 0.193 (95% confidence interval, 0.0893-0.2967; P < .0001).

CONCLUSIONS

RECIST missed all CRs and underestimated the extent of partial tumor response because of tissue necrosis, wrongly assessing the therapeutic efficacy of locoregional therapies. This evaluation should incorporate the reduction in viable tumor burden as recognized by nonenhanced areas on dynamic imaging studies.

Rhabdomyosarcomatous differentiation in gastrointestinal stromal tumors after tyrosine kinase inhibitor therapy: a novel form of tumor progression

Approximately 80% of advanced metastatic gastrointestinal stromal tumors (GISTs) respond to treatment with the tyrosine kinase inhibitor (TKI) imatinib mesylate. However, the majority of patients suffer disease progression at a median of 2 years due to drug resistance. In general, progressing GISTs retain their typical morphology. Herein, we report 5 cases of progressing metastatic GIST with heterologous rhabdomyoblastic differentiation after TKI treatment. Histologic, immunohistochemical, and mutational analyses were performed on histologically classic GISTs and components with rhabdomyoblastic differentiation. There were 3 men and 2 women (ranging from 35 to 66 y of age). Three tumors were localized at presentation (2 stomach and 1 small bowel) and 2 presented with metastases. All localized primary tumors were high risk. Two tumors showed spindle cell morphology and 3 were epithelioid, including 1 with marked pleomorphism. After resection of the 3 localized primary tumors, intra-abdominal (2 patients) and liver (1 patient) metastases developed. All patients were treated with imatinib and showed partial clinical responses (4 patient) or stable disease (1 patient). Four patients subsequently progressed; 2 patients were treated with sunitinib after progression with minor responses. Four patients underwent surgical debulking. At last follow-up (range: 20 to 87 mo), 2 patients died of disease, 2 were alive with metastatic disease resistant to TKIs, and 1 was alive without evidence of disease. In all cases, rhabdomyoblastic differentiation was identified adjacent to areas with classic GIST morphology in at least 1 metastatic site; in 1 case, the primary tumor (after treatment with TKIs) showed heterologous differentiation. The rhabdomyoblastic components showed strong and diffuse positivity for desmin and expressed myogenin, whereas KIT was negative in the rhabdomyoblastic component in all cases. Primary KIT mutations were detected in both the conventional GIST and rhabdomyoblastic components from all patients: KIT exon 11 mutations in 4 cases and a platelet-derived growth factor receptor alpha gene exon 18 deletion in 1 case. No secondary mutations of the type associated with TKI resistance were identified in the rhabdomyoblastic areas. This is the first report of rhabdomyoblastic differentiation occurring in GISTs that progressed on TKI therapy. It is associated with loss of KIT expression, but retention of the receptor tyrosine kinase mutation of the precursor GIST. The rhabdomyoblastic differentiation can represent a diagnostic pitfall. The molecular mechanisms for this form of TKI-resistant clonal evolution remain to be determined.

Phase II trial of single-agent bevacizumab followed by bevacizumab plus irinotecan at tumor progression in recurrent glioblastoma

PURPOSE

To evaluate single-agent activity of bevacizumab in patients with recurrent glioblastoma.

PATIENTS AND METHODS

Patients with recurrent glioblastoma were treated with bevacizumab 10 mg/kg every 2 weeks. After tumor progression, patients were immediately treated with bevacizumab in combination with irinotecan 340 mg/m(2) or 125 mg/m(2) every 2 weeks, depending on use of enzyme-inducing antiepileptic drugs. Complete patient evaluations were repeated every 4 weeks.

RESULTS

Forty-eight heavily pretreated patients were accrued to this study. Thromboembolic events (12.5%), hypertension (12.5%), hypophosphatemia (6%), and thrombocytopenia (6%) were the most common drug-associated adverse events. Six patients (12.5%) were removed from study for drug-associated toxicity (five thromboembolic events, one bowel perforation). Thirty-four patients (71%) and 17 patients (35%) achieved radiographic response based on Levin and Macdonald criteria, respectively. Median progression-free survival (PFS) was 16 weeks (95% CI, 12 to 26 weeks). The 6-month PFS was 29% (95% CI, 18% to 48%). The 6-month overall survival was 57% (95% CI, 44% to 75%). Median overall survival was 31 weeks (95% CI, 21 to 54 weeks). Early magnetic resonance imaging response (first 96 hours and 4 weeks) was predictive of long-term PFS, with the Levin criteria being more predictive than Macdonald criteria. Of 19 patients treated with bevacizumab plus irinotecan at progression, there were no objective radiographic responses. Eighteen patients (95%) experienced disease progression by the second cycle, and the median PFS was 30 days.

CONCLUSION

We conclude that single-agent bevacizumab has significant biologic and antiglioma activity in patients with recurrent glioblastoma.

Decrease of CD117 expression as possible prognostic marker for recurrence in the resected specimen after imatinib treatment in patients with initially unresectable gastrointestinal stromal tumors: a clinicopathological analysis

Gastrointestinal stromal tumors (GIST) are the most common malignant mesenchymal tumors of the gastrointestinal tract. The principal treatment modality for primary GIST is surgery whereas for metastatic GIST, imatinib has an established role. In patients with locally advanced and metastatic GIST, the role of surgery in the imatinib era is still unclear. Fifteen patients with locally advanced (n=9) and/or metastatic GIST (n=6) were treated with imatinib followed by resection. Detailed histopathological examination was performed before and after treatment with imatinib, which was given for a median of 11 months before surgery. Ten patients showed a radiographic partial response, four patients had stable disease, and one patient progressed. At the time of surgery, the median tumor diameter was 6.5 cm. In all the nine patients with locally advanced GIST, a R0 resection could be performed. Histopathological examination showed imatinib effects in all tumors, including the case with progressive disease. All patients with locally advanced disease (n=9) were alive after a median follow-up of 40 months (range: 18-59), of which seven patients were free of disease. Four of the six patients treated for metastatic GIST died of disease after 30, 45, 50, and 74 months of follow-up. Remarkably, in five of six patients in whom CD117 expression was diminished or lost in the resection specimen, disease recurrence was observed. In patients with retained CD117 expression, one of the nine patients had recurrent disease. In conclusion, preoperative imatinib treatment in patients with locally advanced GIST resulted in a decrease of tumor load in most patients, enabling complete surgical resection. For patients with metastatic GIST, the role of surgery remains less clear. Loss or decrease of CD117 expression in the resected specimen after imatinib treatment may be associated with disease recurrence.

Heterogeneity of kinase inhibitor resistance mechanisms in GIST

Most GIST patients develop clinical resistance to KIT/PDGFRA tyrosine kinase inhibitors (TKI). However, it is unclear whether clinical resistance results from single or multiple molecular mechanisms in each patient. KIT and PDGFRA mutations were evaluated in 53 GIST metastases obtained from 14 patients who underwent surgical debulking after progression on imatinib or sunitinib. To interrogate possible resistance mechanisms across a broad biological spectrum of GISTs, inter- and intra-lesional heterogeneity of molecular drug-resistance mechanisms were evaluated in the following: conventional KIT (CD117)-positive GISTs with KIT mutations in exon 9, 11 or 13; KIT-negative GISTs; GISTs with unusual morphology; and KIT/PDGFRA wild-type GISTs. Genomic KIT and PDGFRA mutations were characterized systematically, using complementary techniques including D-HPLC for KIT exons 9, 11-18 and PDGFRA exons 12, 14, 18, and mutation-specific PCR (V654A, D820G, N822K, Y823D). Primary KIT oncogenic mutations were found in 11/14 patients (79%). Of these, 9/11 (83%), had secondary drug-resistant KIT mutations, including six (67%) with two to five different secondary mutations in separate metastases, and three (34%) with two secondary KIT mutations in the same metastasis. The secondary mutations clustered in the KIT ATP binding pocket and kinase catalytic regions. FISH analyses revealed KIT amplicons in 2/10 metastases lacking secondary KIT mutations. This study demonstrates extensive intra- and inter-lesional heterogeneity of resistance mutations and gene amplification in patients with clinically progressing GIST. KIT kinase resistance mutations were not found in KIT/PDGFRA wild-type GISTs or in KIT-mutant GISTs showing unusual morphology and/or loss of KIT expression by IHC, indicating that resistance mechanisms are fundamentally different in these tumours. Our observations underscore the heterogeneity of clinical TKI resistance, and highlight the therapeutic challenges involved in salvaging patients after clinical progression on TKI monotherapies.

Heterogeneity of kinase inhibitor resistance mechanisms in GIST

Most GIST patients develop clinical resistance to KIT/PDGFRA tyrosine kinase inhibitors (TKI). However, it is unclear whether clinical resistance results from single or multiple molecular mechanisms in each patient. KIT and PDGFRA mutations were evaluated in 53 GIST metastases obtained from 14 patients who underwent surgical debulking after progression on imatinib or sunitinib. To interrogate possible resistance mechanisms across a broad biological spectrum of GISTs, inter- and intra-lesional heterogeneity of molecular drug-resistance mechanisms were evaluated in the following: conventional KIT (CD117)-positive GISTs with KIT mutations in exon 9, 11 or 13; KIT-negative GISTs; GISTs with unusual morphology; and KIT/PDGFRA wild-type GISTs. Genomic KIT and PDGFRA mutations were characterized systematically, using complementary techniques including D-HPLC for KIT exons 9, 11-18 and PDGFRA exons 12, 14, 18, and mutation-specific PCR (V654A, D820G, N822K, Y823D). Primary KIT oncogenic mutations were found in 11/14 patients (79%). Of these, 9/11 (83%), had secondary drug-resistant KIT mutations, including six (67%) with two to five different secondary mutations in separate metastases, and three (34%) with two secondary KIT mutations in the same metastasis. The secondary mutations clustered in the KIT ATP binding pocket and kinase catalytic regions. FISH analyses revealed KIT amplicons in 2/10 metastases lacking secondary KIT mutations. This study demonstrates extensive intra- and inter-lesional heterogeneity of resistance mutations and gene amplification in patients with clinically progressing GIST. KIT kinase resistance mutations were not found in KIT/PDGFRA wild-type GISTs or in KIT-mutant GISTs showing unusual morphology and/or loss of KIT expression by IHC, indicating that resistance mechanisms are fundamentally different in these tumours. Our observations underscore the heterogeneity of clinical TKI resistance, and highlight the therapeutic challenges involved in salvaging patients after clinical progression on TKI monotherapies.

Promises and challenges of positron emission tomography for assessment of sarcoma in daily clinical practice

A correct histological diagnosis, careful staging and detection of tumour response to treatment are all crucial in the management of sarcomas. Imaging is important in all of these stages. Sarcomas have distinct biological and treatment-related features posing challenges for imaging. For example, size measurements may not adequately reflect response rates. Techniques which can measure tissue function rather than generate merely anatomical data such as positron emission tomography (PET) are rapidly gaining interest. We discuss the importance of imaging in different stages of patient management, emphasising the unique characteristics of sarcoma. Furthermore, we discuss the potential of PET for the various indications, focussing on therapy evaluation.

Imaging techniques to evaluate the response to treatment in oncology: current standards and perspectives

Response evaluation in solid tumours currently uses radiological imaging techniques to measure changes under treatment. Imaging requires a well-defined anatomical lesion to be viewed and relies on the measurement of a reduction in tumour size during treatment as the basis for presumed clinical benefit. However, with the development of anti-angiogenesis agents, anatomical imaging has became inappropriate as certain tumours would not reduce in size. Functional studies are therefore necessary and dynamic contrast enhanced magnetic resonance imaging (DCE-MRI), DCE-computed tomography (CT) and DCE-ultrasonography (US) are currently being evaluated for monitoring treatments. Diffusion-weighted MR imaging (DW-MRI) and magnetic resonance spectroscopy (MRS) are also capable of detecting changes in cell density and metabolite content within tumours. In this article, we review anatomical and functional criteria currently used for monitoring therapy. We review the published data on DCE-MRI, DCE-CT, DCE-US, DW-MRI and MRS. This literature review covers the following area: basic principles of the technique, clinical studies, reproducibility and repeatability, limits and perspectives in monitoring therapy. Anatomical criteria such as response evaluation criteria in solid tumours (RECIST) will require adaptation to employ not only new tools but also different complementary techniques such as functional imaging in order to monitor therapeutic effects of conventional and new anti-cancer agents.

Phase 2 trial of talactoferrin in previously treated patients with metastatic renal cell carcinoma

BACKGROUND

Talactoferrin (TLF), a recombinant form of human lactoferrin (hLF), is an immunomodulatory iron-binding glycoprotein first identified in breast milk. Its immunomodulatory functions include activation of natural killer (NK) and lymphokine-activated killer cells and enhancement of polymorphonuclear cells and macrophage cytotoxicity. Studies in animal models have shown promising anticancer activity, and clinical antitumor activity has been observed in nonsmall cell lung cancer and other tumor types. The purpose of the current study was to evaluate the activity and safety of TLF in patients with refractory metastatic renal cell carcinoma (RCC).

METHODS

Forty-four adult patients with progressive advanced or metastatic RCC who had failed prior systemic therapy received oral talactoferrin at a dose of 1.5 g twice daily on a 12-week-on 2-week-off schedule. Patients were evaluated for progression-free survival at 14 weeks, overall response rate, and progression-free and overall survival.

RESULTS

TLF was well tolerated. No significant hematologic, hepatic, or renal toxicities were reported. The study met its predefined target with a 14-week progression-free survival rate of 59%. The response rate was 4.5%. The mMedian progression-free survival was 6.4 months and the median overall survival was 21.1 months.

CONCLUSIONS

TLF is a well-tolerated new agent that has demonstrated preliminary signs of clinical activity. Given the lack of toxicity, the lack of rapid disease progression in this cohort, and the preclinical data on immune activation, a randomized study assessing its effects on disease progression in patients with metastatic RCC is rational.

Radiologic measurements of tumor response to treatment: practical approaches and limitations

Objective response assessment is important to describe the treatment effect of anticancer drugs. Standardization by using a "common language" is also important for comparison of results from different trials. In contrast to clinical results, which can be subjective, diagnostic imaging provides a greater opportunity for objectivity and standardization. It was generally accepted that a decrease in tumor size correlated with treatment effect; as a result, imaging was adopted for lesion measurement in the World Health Organization (WHO) criteria in 1979. However, because of some limitations of the WHO criteria, the Response Evaluation Criteria in Solid Tumors (RECIST) were introduced in 2000. In RECIST, imaging was recognized as indispensable for response evaluation of solid tumors. Nevertheless, the widespread use of multidetector computed tomography and other imaging innovations have made RECIST outdated, with a concomitant need for modifications. Meanwhile, newer anticancer agents with targeted mechanisms of action have demonstrated an inherent limitation and unsuitability of anatomic tumor evaluation that assesses only lesion size. In addition, the effect of these new drugs changes the paradigm according to which tumor response or response rate is measured. Complete and partial responses cannot be the end points in all clinical trials; in some cases, disease control or progression-free survival may be the more relevant end point.

A preclinical model for predicting drug response in soft-tissue sarcoma with targeted AAVP molecular imaging

Human sarcomas are rare but diverse malignant tumors derived from mesenchymal tissue. Clinical response to therapy is currently determined by the modified World Health Organization (WHO) criteria or the Response Evaluation Criteria in Solid Tumors (RECIST), but these standards correlate poorly with sarcoma patient outcome. We introduced ligand-directed particles with elements of AAV and phage (AAVP) to enable integration of tumor targeting to molecular imaging. We report drug-response monitoring and prediction in a nude rat model of human sarcoma by AAVP imaging. As a proof-of-concept, we imaged Herpes simplex thymidine kinase in a clinic-ready setting with PET to show that one can a priori predict tumor response to a systemic cytotoxic. Given the target expression in patient-derived sarcomas, this platform may be translated in clinical applications. Sarcoma-specific ligands and promoters may ultimately lead to an imaging transcriptome.

Lésions hépatiques en cancérologie générale

In order to improve management of oncologic patients, a standardized 5-step approach should be considered: detection, characterization, locoregional and systemic staging, and post treatment follow up. The use of imaging techniques will be adapted to the clinical question at hand during multi-disciplinary review of cases. The role of the radiologist is to review the indications for each imaging modality and incorporate the results in the clinical context.

A phase II study of irinotecan (CPT-11) and carboplatin in patients with limited disease small cell lung cancer (SCLC)

PURPOSE

The aim of this phase II trial was to evaluate the efficacy and safety of a combination chemotherapy containing irinotecan (CPT-11) and carboplatin as first-line treatment of patients with small cell lung cancer (SCLC).

PATIENTS AND METHODS

From December 2002 to May 2004 61 patients with limited disease (IASLC classification) were enrolled who were not suitable for concurrent chemo-radiotherapy. Eighteen of the 61 patients (29.5%) had malignant pleural or pericardial effusion and 4 patients (6.6%) had involved supra- or infraclavicular lymph nodes. Patients received irinotecan 50mg/m(2) on days 1, 8 and 15 and carboplatin AUC 5 on day 1, every 4 weeks.

RESULTS

A total of 233 chemotherapy cycles were administered. The median number of cycles per patient was 4. The overall response rate to chemotherapy on an intention-to-treat basis was 64%. The median overall survival was 13.8 months, the median disease-free survival 8.0 months, the 1-year survival rate 53.5%, and the 2-year survival rate 17.9%. Haematological and non-hematogical toxicities were low (CTC-grade 3 neutropenia 14.8%, grade 3 thrombocytopenia 5.2%, grade 3/4 anemia 5.1%, grade 3 nausea/vomiting 5.1%, grade 3 diarrhea 3.6%, grade 3 alopecia 3.6% of pts).

CONCLUSION

The results suggest that the combination of irinotecan (CPT-11) and carboplatin is active and well tolerable in patients with limited disease SCLC who were not suitable for concurrent chemotherapy.

Pathologic and molecular heterogeneity in imatinib-stable or imatinib-responsive gastrointestinal stromal tumors

PURPOSE

Gastrointestinal stromal tumor (GIST) is the most common sarcoma of the intestinal tract. Nearly all tumors express KIT protein, and most have an activating mutation in either KIT or PDGFRA. Therapy with selective tyrosine kinase inhibitors achieves a partial response or stable disease in approximately 80% of patients with advanced GIST. However, after an initial clinical response, some patients develop imatinib resistance. Our goal was to investigate the spectrum of pathologic response and molecular alterations in a group of GIST patients, clinically defined as having imatinib-stable/imatinib-responsive lesions, who underwent surgical resection.

EXPERIMENTAL DESIGN

Forty-three tumor nodules from 28 patients were available for pathologic and molecular analysis, which included genotyping for primary and secondary KIT/PDGFRA-mutations, cell cycle alterations, and biochemical activation status of KIT and downstream targets. The transcriptional changes of a subset of these tumors were compared with a group of imatinib-naive GISTs on a U133A Affymetrix expression platform.

RESULTS

The histologic response did not correlate with imatinib therapy duration or with proliferative activity. Second-site KIT mutation was identified in only one tumor nodule. Activation of KIT and downstream targets was consistent in all tumors analyzed. Ultrastructurally, a subset of tumors showed a smooth muscle phenotype, which correlated with overexpression of genes involved in muscle differentiation and function.

CONCLUSIONS

The histologic response to imatinib is heterogeneous and does not correlate well with clinical response. Second-site KIT mutations are rare in imatinib-responsive GISTs compared with imatinib-resistant tumors. The gene signature of imatinib-response in GISTs showed alterations of cell cycle control as well as up-regulation of genes involved in muscle differentiation and function.