Byeong Seok Sohn

Detection of KIT and PDGFRA mutations in the plasma of patients with gastrointestinal stromal tumor

In subsets of gastrointestinal stromal tumors (GISTs), mutations of the KIT and PDGFRA receptor tyrosine kinases correlate with tumor prognosis and response to tyrosine kinase inhibitors (TKIs). Determining genotypes in TKI-resistant GISTs is challenging due to the potential risks and limitations of repeated biopsies during the course of treatment. We prospectively collected plasma samples from three GIST patients harboring KIT mutations that were detected in tissue DNA. The plasma samples were then analyzed for mutations in KIT, PDGFRA, and BRAF via next-generation sequencing. We were able to identify primary KIT mutations in all plasma samples. Additional mutations, including KIT exon 17 S821F and PDGFRA exon 18 D842V, were detected in the patient-matched plasma samples during follow-up and appeared to result in decreased sensitivity to TKIs. Our results demonstrate an approach by which primary and secondary mutations are readily detected in blood-derived circulating tumor DNA from patients with GIST. These mutations can be used as biomarkers for prediction of treatment response. The identification of a resistance mutation in plasma DNA will allow early change to alternative TKIs or dose escalation of imatinib for optimal patient management.

Phase II trial of combination chemotherapy with gemcitabine, 5-fluorouracil and cisplatin for advanced cancers of the bile duct, gallbladder, and ampulla of Vater

AIMS AND BACKGROUND For advanced cancers of the bile duct, gallbladder and ampulla of Vater, there are only a few treatment options. We explored the efficacy of the combination of gemcitabine, 5-fluorouracil and cisplatin for advanced biliary cancers. METHODS From September 2003 to April 2010, 28 patients with recurrent or metastatic biliary tract cancer were enrolled. A treatment regimen consisting of gemcitabine (800 mg/m² at a fixed dose rate on days 1 and 8), 5-fluorouracil (1 g/m²/day continuous infusion for 4 days) and cisplatin (60 mg/m² on day 2) was repeated every 3 weeks. RESULTS One (3.6%) patient showed complete response, 8 (28.6%) partial response, 14 (50%) stable disease and 5 (17.9%) disease progression. Overall, the objective response rate was 32.1% (95% CI, 17.9-50.6%) and the disease control rate was 82.1% (95% CI, 64.4-92.1%). Median progression-free survival and overall survival were 7.6 months (95% CI, 5.5-9.7) and 11.2 months (95% CI, 6.8-15.5), respectively. G3/4 neutropenia was observed in 44 (24.3%) of 181 cycles and G3/4 thrombocytopenia in 48 (26.5%) of 181 cycles. There was no treatment-related mortality. CONCLUSIONS The combined regimen of gemcitabine, 5-fluorouracil and cisplatin has comparable activity for patients with advanced cancer of the bile duct, gallbladder and ampulla of Vater. Toxicity was tolerable but substantial.

ThinPrep Cytological Findings of Desmoplastic Small Round Cell Tumor with Extensive Glandular Differentiation: A Case Study

Desmoplastic small round cell tumor (DSRCT) is a rare and highly aggressive neoplasm. The cytological diagnosis of this tumor has only been reported in a few cases. In most of these cases, the diagnosis was made using fine-needle aspiration cytology. Most DSRCTs resemble disseminated carcinomatoses in their clinical manifestation as well as cytomorphologically, even in young-adult patients. These authors report a case of using peritoneal-washing and pleural-effusion ThinPrep cytology to diagnose DSRCT, with extensive glandular differentiation and mucin vacuoles. We found that fibrillary stromal fragment, clinical setting, and adjunctive immunocytochemical staining were most helpful for avoiding misdiagnosis.

Multiple Bone Metastases as the First Manifestation of Hepatocellular Carcinoma in Patient with Noncirrhotic Liver

Hepatocellular carcinoma (HCC) generally occurs on the background of chronic liver disease. Chronic hepatitides B and C and alcoholic liver disease are well-known risk factors for HCC, and it is uncommon in noncirrhotic liver. Extrahepatic metastasis seldom occurs in patients with early stage intrahepatic HCC and isolated bone metastases as a first documented extrahepatic metastasis is unusual presentation. In this report, we present a rare case of small solitary HCC (<3 cm) in noncirrhotic liver, presenting isolated bone metastases as a sole manifestation in patient with no well-known risk factors. This case suggests that HCC should be considered as one of differential diagnoses in patient presenting with multiple bone metastases, even in the absence of liver cirrhosis.

A phase II trial of 5-fluorouracil, leucovorin and mitomycin C in patients with advanced gastric cancer

AIMS AND BACKGROUND Low-dose leucovorin is a well known potentiator of 5-fluorouracil activity in colorectal cancer but not in gastric cancer. To assess their efficacy on response rate and survival, 5-fluorouracil and low-dose leucovorin were combined with mitomycin C. METHODS Fifty patients with gastric cancer and metastatic disease, unresectable or relapsed disease were treated with the following regimen every 28 days: mitomycin C, 7 mg/m2 IV bolus on day 1, and leucovorin, 20 mg/m2 IV, followed immediately by 5-fluorouracil, 375 mg/m2 on days 1-5. All had measurable disease and were assessable for toxicity. Prognostic factors were analyzed to examine any association with response rate or overall survival. RESULTS Nineteen of the 48 assessable patients (39.6%; 95% confidence interval [CI], 25.8-53.4) responded, including 4 complete responses (8.3%). The median progression-free survival was 108 days (range, 18+ - 146), and the median duration of survival was 338 days (11.3 months; range, 18+ - 903 days). Response rate and overall survival were not significantly associated with CEA level, performance status, age, or primary and metastatic tumor sites. Toxicity associated with the chemotherapy was tolerable, and all patients were treated at the outpatient clinic. Leukopenia and thrombocytopenia WHO grade ≥3 occurred in 5% and 1% of the patients, respectively. Nausea and vomiting were the most frequent adverse effects (29%), all grade 1 or 2. CONCLUSIONS Combination chemotherapy of 5-fluorouracil plus leucovorin with mitomycin C is effective for the treatment of advanced gastric cancer and is well tolerated.