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Haesun Choi

Publications and source records attributed to Haesun Choi.

18 recordsLinked to original sources
PubMed2006

Correlation of immunophenotype with progression-free survival in patients with gastrointestinal stromal tumors treated with imatinib mesylate.

BACKGROUND: The therapy for gastrointestinal stromal tumor (GIST) has been revolutionized by imatinib mesylate (IM). It is unknown whether the levels of KIT expression or the presence of CD34, smooth muscle actin (SMA), desmin, or S-100 protein predicts patient outcome from IM therapy. In the current study, the prognostic effects for KIT and other proteins (CD34, SMA, desmin, S-100) were analyzed in a series of GISTs in which protein expression was evaluated by immunohistochemical analysis (IHC). METHODS: The cases of 106 patients with GIST who were uniformly treated with IM at the study institution between December 15, 2000, and January 13, 2002 were evaluated retrospectively. The association between KIT intensity, CD34, desmin, SMA, S-100 protein, and progression-free survival (PFS) was studied. Kaplan-Meier analysis and the Cox proportional hazards regression model were used for statistical analysis. RESULTS: The majority of tumors arose from the stomach (37%), small intestine (35%), and colorectum (14%). KIT expression as determined by IHC was categorized as weak (10%), intermediate (32%), or strong (58%). Patient tumors expressed CD34 (75%), SMA (56%), desmin (1%), and S-100 protein (32%). Patients whose GIST had weak, intermediate, or strong KIT expression were found to have an 18-month PFS rate of 80%, 84%, and 69%, respectively (P = .30). The presence or absence of CD34, SMA, desmin, or S-100 protein did not appear to correlate with PFS after IM. CONCLUSIONS: Patients with the appropriate clinical presentation and KIT-positive GIST tumors appear to benefit from IM independent of the level of KIT or the expression of CD34, SMA, desmin, or S-100 protein by IHC.

Adult↗
PubMed2006

Expression of Bcl-2 in gastrointestinal stromal tumors: correlation with progression-free survival in 81 patients treated with imatinib mesylate.

BACKGROUND: The natural history of gastrointestinal stromal tumor (GIST) has been revolutionized by imatinib mesylate (imatinib) therapy. Before imatinib, Bcl-2 expression in GIST was associated with a worse prognosis or added no additional prognostic value. To the authors' knowledge, the current study is the first to evaluate Bcl-2 expression in pre-imatinib GIST tissue samples as a prognostic marker of progression-free survival (PFS) time in patients treated with imatinib. METHODS: The cases of 81 patients with GIST who were evaluated between December 15, 2000 and September 1, 2001 were retrospectively reviewed. Clinicopathologic variables were reviewed. GIST cell morphology and patterns of Bcl-2 expression were described. The methods of Kaplan-Meier and the Cox proportional hazards regression model were used for statistical analysis. RESULTS: Sixty-one (75%) patients had tumors that expressed Bcl-2, and 20 (25%) patients had tumors that were negative for Bcl-2. All epithelioid tumors (n = 12) expressed Bcl-2 and tumors with mixed morphology exhibited Bcl-2 expression in the epithelioid component. A trend toward longer PFS for patients whose tumors expressed Bcl-2 at a greater immunohistochemical intensity was observed (20.6 mos for no Bcl-2 expression; 28.3 mos for 1++Bcl-2 expression; 31.9 mos for 1.5++Bcl-2 expression; 40.8 mos for 2++Bcl-2 expresssion; and 35.9 mos for 3++Bcl-2 expression). CONCLUSIONS: In contrast to studies performed in the preimatinib era, in which Bcl-2 was found to be a negative prognostic indicator, the current study suggests a trend toward better PFS with increasing Bcl-2 expression level in GISTs from patients subsequently treated with imatinib. Larger studies may help elucidate the influence of Bcl-2 expression on PFS after therapy with imatinib.

Adult↗
PubMed2006

Fat-suppressed three-dimensional dual echo Dixon technique for contrast agent enhanced MRI.

PURPOSE: To develop a fast T1-weighted, fat-suppressed three-dimensional dual echo Dixon technique and to demonstrate its use in contrast agent enhanced MRI. MATERIALS AND METHODS: A product fast three-dimensional gradient echo pulse sequence was modified to acquire dual echoes after each RF excitation with water and fat signals in-phase (IP) and opposed-phase (OP), respectively. An on-line reconstruction algorithm was implemented to automatically generate separate water and fat images. The signal to noise ratio (SNR) of the new technique was compared to that of the product technique in phantom. In vivo abdomen and breast images of cancer patients were acquired at 1.5 Tesla using both techniques before and after intravenous administration of gadolinium contrast agent. RESULTS: In phantom, the new technique yields a close to the theoretically predicted 41% increase in SNR in comparison to the product technique without fat suppression (FS). In vivo images of the new technique show noticeably improved FS and image quality in comparison to the images acquired of the same patients using the product technique with FS. CONCLUSION: The three-dimensional dual echo Dixon technique provides excellent image quality and can be used for T1-weighted, fat-suppressed imaging with contrast agent injection.

Algorithms↗
PubMed2005

A fast spin echo two-point Dixon technique and its combination with sensitivity encoding for efficient T2-weighted imaging.

A fast spin echo two-point Dixon (fast 2PD) technique was developed for efficient T2-weighted imaging with uniform water and fat separation. The technique acquires two interleaved fast spin echo images with water and fat in-phase and 180 degrees out-of-phase, respectively, and generates automatically separate water and fat images for each slice. The image reconstruction algorithm uses an improved and robust region-growing scheme for phase correction and achieves consistency in water and fat identification between different slices by exploiting the intrinsic correlation between the complex images from two neighboring slices. To further lower the acquisition time to that of a regular fast spin echo acquisition with a single signal average, we combined the fast 2PD technique with sensitivity encoding (SENSE). Phantom experiments show that the fast 2PD and SENSE are complementary in scan efficiency and signal-to-noise ratio (SNR). In vivo data from scanning of clinical patients demonstrate that T2-weighted imaging with uniform and consistent fat separation, including breath-hold abdominal examinations, can be readily performed with the fast 2PD technique or its combination with SENSE.

Abdomen↗
PubMed2005

Imatinib resistance in gastrointestinal stromal tumors.

Conventional chemotherapeutic drugs are ineffective in treatment of gastrointestinal stromal tumors (GISTs). Imatinib (STI571, Gleevec, Glivec; Novartis Pharmaceuticals, East Hanover, NJ), a selective inhibitor of KIT, ABL, BCR-ABL, PDGFRA, and PDGFRB, represents a new paradigm of targeted cancer therapy and has revolutionized the treatment of patients with chronic myelogenous leukemia and GISTs. Unfortunately, imatinib resistance has emerged. The reported mechanism of imatinib resistance in GISTs involves missense mutation in the kinase domain of KIT, including Thr670Ile, Tyr823Asp, and Val654Ala. The established mechanisms and potential mechanisms of imatinib resistance in GISTs, the imaging studies indicative of early development of imatinib resistance, and the management of imatinib-resistant GISTs are discussed.

Antineoplastic Agents↗
PubMed2005

Critical issues in response evaluation on computed tomography: lessons from the gastrointestinal stromal tumor model.

Imaging technology plays a major role in treatment response assessment in solid tumors and in surveillance for recurrence or progression. Currently available response evaluation criteria, Response Evaluation Criteria in Solid Tumors (RECIST), are based on unidimensional tumor size. Recently, however, these strictly size-based criteria for evaluating responses have been criticized because they do not reflect the biologic changes of solid tumors induced by targeted therapies and thus may be misleading. This problem is evident in response evaluation in advanced gastrointestinal stromal tumor (GIST) treated with a new molecularly targeted agent, imatinib. GISTs can increase in size despite good response to imatinib, and focal progression within a responding GIST can be overlooked with current size-based imaging criteria. Modified objective criteria using a combination of tumor size and density on CT are promising in early response evaluation and in predicting long-term prognosis in patients with advanced GIST treated with imatinib. These criteria may have broad applicability as additional targeted therapies become available to treat solid tumors.

Antineoplastic Agents↗
PubMed2005

Comparison of treatment volumes and techniques in prostate cancer radiation therapy.

OBJECTIVE: To compare dose-volume histograms (DVHs) for 3 target volumes (group 1, prostate + seminal vesicles + pelvic lymph nodes; group 2, prostate + seminal vesicles; group 3, prostate only) to determine the difference in dose to normal structures (rectum, bladder, and femoral heads) while controlling for target dose using 3-dimensional conformal radiation therapy (3DCRT) versus intensity modulated radiation therapy (IMRT). METHODS: Ten patients with localized prostate cancer were randomly selected. 3DCRT and IMRT planning were done to deliver 75.6 Gy to the prostate, 50.4 Gy to the pelvic nodes, and 55.8 Gy to the seminal vesicles at a standard fractionation of 1.8 Gy. An additional plan delivering 75.6 Gy to the seminal vesicles using IMRT was run. DVHs were compared for 3DCRT and IMRT. RESULTS: In all 3 groups, the percent rectum receiving > or =70 Gy, > or =60 Gy, and > or =40 Gy was significantly less for IMRT than for 3DCRT. Increasing target volumes, as necessary for pelvic nodal irradiation, overall did not result in higher rectal doses for IMRT. With 3DCRT, however, larger target volumes did increase the amount of rectum irradiated. Similar results were obtained for the femoral heads whereas results for the bladder were mixed. CONCLUSION: When compared with 3DCRT, IMRT delivered equivalent or higher doses to the target volume with greater sparing of critical organs. Because dose-volume parameters have been shown to relate to toxicity, IMRT would appear to be the favored technique for prostate cancer radiation, particularly with regard to nodal treatment.

Dose Fractionation, Radiation↗
PubMed2004

A missense mutation in KIT kinase domain 1 correlates with imatinib resistance in gastrointestinal stromal tumors.

KIT gain of function mutations play an important role in the pathogenesis of gastrointestinal stromal tumors (GISTs). Imatinib is a selective tyrosine kinase inhibitor of ABL, platelet-derived growth factor receptor (PDGFR), and KIT and represents a new paradigm of targeted therapy against GISTs. Here we report for the first time that, after imatinib treatment, an additional specific and novel KIT mutation occurs in GISTs as they develop resistance to the drug. We studied 12 GIST patients with initial near-complete response to imatinib. Seven harbored mutations in KIT exon 11, and 5 harbored mutations in exon 9. Within 31 months, six imatinib-resistant rapidly progressive peritoneal implants (metastatic foci) developed in five patients. Quiescent residual GISTs persisted in seven patients. All six rapidly progressive imatinib-resistant implants from five patients show an identical novel KIT missense mutation, 1982T-->C, that resulted in Val654Ala in KIT tyrosine kinase domain 1. This novel mutation has never been reported before, is not present in pre-imatinib or post-imatinib residual quiescent GISTs, and is strongly correlated with imatinib resistance. Allelic-specific sequencing data show that this new mutation occurs in the allele that harbors original activation mutation of KIT.

Alleles↗
PubMed2004

Silicone-specific imaging using an inversion-recovery-prepared fast three-point Dixon technique.

PURPOSE: To demonstrate a new hybrid magnetic resonance imaging (MRI) technique capable of simultaneously generating water-specific and silicone-specific images in a single acquisition. MATERIALS AND METHODS: This technique combines short TI inversion-recovery (STIR) technique for robust fat suppression with an efficient fast spin-echo-based three-point Dixon technique for robust separation of remaining water and silicone in the presence of field inhomogeneities. Images demonstrating the feasibility of the technique were acquired with a 1.5-Tesla scanner in a phantom and in a volunteer with both saline and silicone implants in vivo. RESULTS: The new technique provided water-specific and silicone-specific images of diagnostic quality. Separation of the water and silicone chemical species was complete and satisfactory. Compared with a chemical shift-selective technique, the new technique does not rely heavily on field homogeneity and requires the same or even less scan time to acquire images with similar scan parameters, resolution, and signal-to-noise ratio (SNR). CONCLUSION: The feasibility and potential application of the new technique were demonstrated via imaging a phantom and a silicone breast prosthesis in vivo, and it may be used for more consistent imaging of the silicone implants without compromising the image quality or overall scan time.

Adipose Tissue↗
PubMed2004

Early and late complications after radiofrequency ablation of malignant liver tumors in 608 patients.

BACKGROUND: Radiofrequency ablation (RFA) has become a common treatment of patients with unresectable primary and secondary hepatic malignancies. We performed this prospective analysis to determine early (within 30 days) and late (more than 30 days after) complication rates associated with hepatic tumor RFA. METHODS: All patients treated between January 1, 1996 and June 30, 2002 with RFA for hepatic malignancies were entered into a prospective database. Patients were evaluated during RFA treatment, throughout the immediate post RFA course, and then every 3 months after RFA to assess for the development of treatment-related complications. RESULTS: A total of 608 patients, 345 men (56.7%) and 263 women (43.3%), with a median age of 58 years (range 18-85 years) underwent RFA of 1225 malignant liver tumors. Open intraoperative RFA was performed in 382 patients (62.8%), while percutaneous RFA was performed in 226 (37.2%). The treatment-related mortality rate was 0.5%. Early complications developed in 43 patients (7.1%). Early complications were more likely to occur in patients treated with open RFA (33 [8.6%] of 382 patients) compared with percutaneous RFA (10 [4.4%] 226 patients, P < 0.01), and in patients with cirrhosis (25 [12.9%] complications in 194 patients) compared with noncirrhotic patients (31 [7.5%] complications in 414 patients, P < 0.05). Late complications arose in 15 patients (2.4%) with no difference in incidence between open and percutaneous RFA treatment. The combined overall early and late complication rate was 9.5%. CONCLUSIONS: Hepatic tumor RFA can be performed with low mortality and morbidity rates. Though relatively rare, late complications can develop and physicians performing hepatic RFA must be cognizant of these delayed treatment-related problems.

Adolescent↗
PubMed2004

Detection of small pancreatic tumors with multiphasic helical CT.

OBJECTIVE: The purpose of this study was to evaluate the sensitivity and specificity of helical CT in the detection of adenocarcinomas of the pancreas measuring 2 cm or smaller at pathologic examination. MATERIALS AND METHODS: Thin-section triple phase (20, 40, and 70 sec after the start of injection) contrast-enhanced helical CT scans of the abdomen in 18 patients with a pancreatic carcinoma that was 2 cm or smaller and 18 patients with a normal pancreas were retrospectively reviewed by two senior radiologists who specialized in oncologic abdominal imaging. Discrepancies were resolved by consensus. The observers were unaware of the clinical information. CT scans were evaluated for the presence of a pancreatic mass, bile, and pancreatic duct stricture. The location and size of tumors as determined on CT were compared with pathologic findings. The CT results were also compared with the prospective CT interpretations derived from the radiology reports and with the endoscopic sonographic reports when available. RESULTS: The sensitivity of thin-section triple-phase helical CT in the detection of small pancreatic masses was 77%, and the specificity was 100% for the two experienced observers. The sensitivity and specificity were 72% and 100%, respectively, for the prospective interpretations done by 10 observers. There was no correlation between the tumor size at pathology and the CT measurements. CONCLUSION: Thin-section contrast-enhanced helical CT is sensitive and highly specific for the detection of pancreatic tumors measuring 2 cm or smaller. Improvement in the detection rate of this technique compared with previous techniques lies in the optimization of parenchymal enhancement during the pancreatic phase and the decrease in slice thickness.

Adenocarcinoma↗
PubMed2004

CT evaluation of the response of gastrointestinal stromal tumors after imatinib mesylate treatment: a quantitative analysis correlated with FDG PET findings.

OBJECTIVE: We correlated changes in tumor density on CT with changes in glucose metabolism, or the maximum standardized uptake value (SUV(max)), on FDG PET and sought to develop CT imaging criteria that can be used to objectively evaluate tumor response in patients with metastatic gastrointestinal stromal tumors (GISTs) who undergo treatment with imatinib mesylate. MATERIALS AND METHODS: Using the criteria established by the Response Evaluation Criteria in Solid Tumors (RECIST) group, we selected 173 tumors (in 36 patients) for study. Tumor size and density were determined objectively, and overall tumor response (OTR) was evaluated subjectively on CT images. The changes in these parameters before and after treatment were correlated with changes in SUV(max). RESULTS: Significant decreases were seen in both tumor density (mean, 12.3 H [16.5%]; p < 0.0001) and SUV(max) (mean, 3.43 [64.9%]; p < 0.0001). OTR evaluated subjectively, correlated well with changes in SUV(max) (p < 0.0001). No statistically significant association was found between changes in tumor density and changes in SUV(max) (p = 0.3088), but 70% (14/20) of the patients with tumors that showed response on FDG PET exhibited at least a partial response by a change in tumor density. Tumor size was found to have decreased significantly 2 months after treatment (p = 0.0070). However, in 75% of the patients, the disease was stable according to the traditional tumor response criteria of RECIST. CONCLUSION: FDG PET is sensitive and specific for evaluating tumor response but cannot be used in patients whose baseline FDG PET results are negative for tumors. Although subjective evaluation was a better indicator of treatment response than was tumor density alone, the tumor density measurement is a good indicator and provides a reliable quantitative means of monitoring the tumor. RECIST, using only tumor size, was unreliable for monitoring GISTs during the early stage of imatinib mesylate treatment.

Adult↗
PubMedDate not supplied

MR imaging of common and uncommon large pelvic masses.

Magnetic resonance (MR) imaging is often used in the detection and staging of large pelvic masses. Many large masses in the female pelvis arise from the reproductive organs (eg, uterus, cervix, ovaries, fallopian tubes). In addition, these masses may arise from the gastrointestinal system, urinary system, adjacent soft tissues, peritoneum, or retroperitoneum or from metastases. The majority of large masses in the female pelvis represent such commonly encountered entities as uterine fibroid tumor, dermoid tumor, ovarian cyst, and ovarian cancer. However, uncommon pelvic masses such as mesothelioma, adenocarcinoma, carcinosarcoma, leiomyosarcoma, and desmoid tumor may also be seen. Thus, the differential diagnosis for female pelvic masses is extensive. However, the site of origin, MR imaging characteristics, and clinical history may all help narrow the differential diagnosis. Although with large tumors it may not always be possible to determine the site of origin or distinguish between various tumors at radiology, familiarity with the clinicopathologic and MR imaging features of common and uncommon pelvic masses is important for diagnosis and treatment.

Female↗
PubMedDate not supplied

Gastrointestinal stromal tumor: role of CT in diagnosis and in response evaluation and surveillance after treatment with imatinib.

Gastrointestinal stromal tumors (GISTs), which arise from the interstitial cells of Cajal, are the most common nonepithelial tumors of the gastrointestinal tract. It is now well known that imatinib, a new molecularly targeted tyrosine kinase receptor blocker, results in a dramatic response and markedly improved long-term survival in patients with GISTs. The increasing recognition of GISTs and the prolonged survival have made imaging increasingly important not only for diagnosis but also for monitoring the effects of treatment and detecting tumor progression. Computed tomography (CT) is the imaging modality of choice for these purposes. The imaging findings at initial presentation, during treatment, and at tumor progression were studied in 113 patients with primary and advanced GISTs before and up to 37 months after imatinib treatment. GISTs occur anywhere along the gastrointestinal tract, most commonly in the stomach and small bowel. At contrast material-enhanced CT, localized primary GISTs are typically exophytic, large, hypervascular masses. When the tumors respond to treatment, the changes in tumor size may initially vary; however, GISTs typically become homogeneous and hypoattenuating, with disappearance of enhancing tumor nodules and tumor vessels in the early posttreatment period. Development of a nodule within the treated tumor is unique to GISTs and indicates recurrence regardless of changes in tumor size.

Antineoplastic Agents↗