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Biomedical subjects

A T Chan

Publications and source records attributed to A T Chan.

At least 37 records · Page 2Linked to original sources
PubMed2000

WWW + smart card: towards a mobile health care management system.

This paper highlights the benefits of combining the World Wide Web and smart card technologies to support a highly mobile health management framework. In particular, we describe an approach using the SmartCard-Web Gateway Interface (SGI) as a common interface to communicate and access the medical records residing in a smart card. Importantly, by employing HTTP as the baseline protocol to access information on the smart card, SGI promotes the use of de facto standard web browsers as the common client user interface. The initial implementation of the framework has demonstrated the feasibility of the concept in facilitating a truly mobile access of patient's medical records based on SGI.

Computer Security↗
PubMed2000

Novel intertypic recombinants of epstein-barr virus in the chinese population.

Among 34 Epstein-Barr virus isolates from nonimmunocompromised Chinese donors, we identified three intertypic recombinants with type 1 sequences at the EBNA2 locus and type 2 sequences at some or all of the EBNA3A, -3B, and -3C loci. These appear to have arisen from independent, evolutionarily recent recombination events; such events may be commoner in nonimmunocompromised populations than hitherto imagined.

Base Sequence↗
PubMed2000

Molecular analysis of circulating tumor cells in peripheral blood from patients with germ cell tumor: a quantitative approach.

Germ cell tumor (GCT) is one of the few malignancies in which recurrent patients would have a good chance of cure by chemotherapy. Using semiquantitative reverse transcription polymerase chain reaction for alpha-fetoprotein (alphafp) mRNA, we measured the circulating tumor load in 54 peripheral blood samples from 7 GCT patients at diagnosis and 47 healthy controls. Clinicopathological information of GCT patients was obtained during a 12-month follow-up. As compared to the upper limit among healthy controls, alphafp mRNA levels increased 23-3.4x103-fold pre-treatment in all 7 patients, and 2.8x103-1.4x104-fold post-treatment in 2 patients studied. All 7 patients with substantially elevated alphafp mRNA levels developed recurrence or metastasis within 12 months of diagnosis. We present evidence that alphafp-expressing tumor cells disseminating in GCT patients before treatment may possibly be the source of recurrence or metastasis. Sequential quantification of alphafp mRNA during the clinical course may provide crucial information for identifying GCT patients at high risk for metastasis.

Adult↗
PubMed2000

Failure patterns and factors affecting prognosis of salivary gland carcinoma: retrospective study.

OBJECTIVES: To investigate the failure patterns and the prognostic factors following postoperative radiotherapy for salivary gland carcinoma. DESIGN: Retrospective study. SETTING: University teaching hospital, Hong Kong. PATIENTS: Fifty patients who had non-disseminated salivary gland carcinoma and who received primary treatment from 1984 through 1993. MAIN OUTCOME MEASURES: Demographic data, cancer T- and N-stages, histological type, site of origin, completeness of surgery, whether postoperative radiotherapy was given, and the clinical outcome. RESULTS: Two (4%) patients had been treated with radiotherapy alone, six (12%) had undergone radical resection alone, and 42 (84%) had been radically treated by using both modalities. The 5-year overall survival and relapse-free survival rates were 78.4% and 63.1%, respectively. The free from local failure and free from distant metastasis rates at 5 years were 77.2% and 72.8%, respectively. The N-stage was a significant prognostic factor. The site of the primary tumour, T-stage, completeness of surgery, and use of postoperative radiotherapy were not significant independent prognosticators; however, among the T-stage tumours, the b-substage carcinomas had significantly fewer local failures (P=0.040) and better survival rates (P=0.038) than the a-substage carcinomas. There were seven (14%) locoregional failures without distant metastasis, seven (14%) cases of distant metastasis without locoregional failures, and four (8%) locoregional failures preceding distant metastasis; isolated regional relapse was rare (1/50; 2%). All regional failures (5/50; 10%) occurred ipsilateral to the primary lesion. There were no deaths due to lymphoepithelioma-like carcinoma or acinic cell carcinoma. CONCLUSIONS: The N-stage is the main prognostic factor of overall survival, relapse- and metastasis-free recovery, and success of treatment for salivary gland carcinoma. Optimal locoregional treatment can help reduce distant metastasis, and the maximal use of postoperative radiotherapy may contribute to improved locoregional control. Elective ipsilateral neck radiotherapy is indicated for lymphoepithelioma-like carcinoma.

Carcinoma, Adenoid Cystic↗
PubMed2000

Quantitative analysis of circulating tumor cells in peripheral blood of osteosarcoma patients using osteoblast-specific messenger RNA markers: a pilot study.

Metastasis is a major cause of mortality and morbidity in osteosarcoma (OS) patients. To monitor tumor dissemination, we assessed the circulating tumor burden in OS patients by semiquantitative reverse transcription-PCR using osteocalcin, osteonectin, osteopontin, and type I collagen (COLL) mRNAs as molecular markers. We distinguished levels of the mRNAs in peripheral blood between OS patients and healthy subjects using an OS-derived cell line (Saos-2) as a reference standard. We prospectively analyzed 40 peripheral blood samples from 11 OS patients at diagnosis and 29 healthy subjects. In all 29 (100%) healthy subjects, we detected osteocalcin, osteonectin, and osteopontin mRNAs that were most likely attributed to illegitimate transcription in normal hematopoietic cells. In contrast, we found low COLL mRNA levels in only 35% (10 of 29) of healthy subjects, but significantly higher COLL mRNA levels in 91% (10 of 11) of OS patients (P < 0.0001). The reverse transcription-PCR assay for COLL mRNA was sensitive down to the detection of 10 Saos-2 cells among 10(6) normal peripheral blood nucleated cells. The upper limit of COLL mRNA determined among the healthy subjects was found exceeded by six OS patients. The substantially elevated COLL mRNA levels in peripheral blood seemed to originate from circulating malignant cells in these six OS patients, all of whom subsequently developed clinical metastases within 12 months of diagnosis (P = 0.002). Conversely, no metastases were detected in the remaining OS patients with normal COLL mRNA levels. Quantification of COLL mRNA may prove valuable for diagnosing OS micrometastasis and assessing prognosis.

Adolescent↗
PubMed1999

Quantitative and temporal correlation between circulating cell-free Epstein-Barr virus DNA and tumor recurrence in nasopharyngeal carcinoma.

Recently, cell-free EBV DNA has been detected in the plasma and serum of patients with nasopharyngeal carcinoma (NPC). We studied the relationship between plasma/serum EBV DNA and tumor recurrence. Using real-time quantitative PCR, the median plasma EBV DNA concentration in 10 patients with tumor recurrence was determined to be 32,350 copies/ml, whereas that in 15 patients in continuous remission for a mean period of 2 years was 0 copy/ml. Longitudinal follow-up of 17 NPC patients revealed 6 individuals with tumor recurrence and 11 patients who remained in remission. Significant elevations in serum EBV DNA, sometimes up to 6 months before detectable clinical deterioration, were observed in the patients who subsequently developed tumor recurrence. Continuously low or undetectable levels of serum EBV DNA were observed in the patients who remained in remission. These results suggest that plasma/serum cell-free EBV DNA may be a valuable tool for the monitoring of NPC patients for the early detection of tumor recurrence.

Bone Neoplasms↗
PubMed1999

Quantitative analysis of cell-free Epstein-Barr virus DNA in plasma of patients with nasopharyngeal carcinoma.

Using real-time quantitative PCR, cell-free EBV DNA was detectable in the plasma of 96% (55 of 57) of nasopharyngeal carcinoma (NPC) patients (median concentration, 21058 copies/ml) and 7% (3 of 43) of controls (median concentration, 0 copies/ml). Advanced-stage NPC patients had higher plasma EBV DNA levels than those with early-stage disease. At 1 month after completion of radiotherapy, plasma EBV DNA was undetectable in 7 of 15 subjects (47%) but remained high in the remaining 8 subjects (53%). Clinical examination revealed that all of the former seven subjects had complete tumor regression, whereas six of the eight latter subjects exhibited evidence of disease persistence or had developed distant metastases. These results suggest that quantitative analysis of plasma EBV DNA may be a useful clinical and research tool in the screening and monitoring of NPC patients.

DNA, Viral↗
PubMed1999

Adjuvant intra-arterial iodine-131-labelled lipiodol for resectable hepatocellular carcinoma: a prospective randomised trial.

BACKGROUND: Resection of hepatocellular carcinoma is potentially curative, but local recurrence is common. In this prospective randomised trial, we aimed to find out if one dose of postoperative adjuvant intra-arterial iodine-131-labelled lipiodol could reduce the rate of local recurrence and increase disease-free and overall survival. METHODS: Patients who underwent curative resection for hepatocellular carcinoma and recovered within 6 weeks were randomly assigned one 1850 MBq dose of 131I-lipiodol or no further treatment (controls). We compared rates of recurrence and disease-free and overall survival (the primary endpoints) between the two groups by intention to treat. We planned an interim analysis when 30 patients (both groups together) had been followed up for a median of 2 years, with the intention of stopping early if the between-group difference in disease-free survival was significant (p=0.029). FINDINGS: Between April, 1992, and August, 1997, we recruited 43 patients: 21 received intra-arterial 131I-lipiodol and 22 received no adjuvant treatment. During a median follow-up of 34.6 (range 14.1-69.7) months, there were six (28.5%) recurrences among the 21 patients in the adjuvant treatment, compared with 13 (59%) in the controls (p=0.04). Median disease-free survival in the treatment and control groups was 57.2 (0.4-69.7) and 13.6 (2.1-68.3) months, respectively (p=0.037). 3-year overall survival in the treatment and control groups was 86.4% and 46.3%, respectively (p=0.039). The interim analysis showed a significant increase in disease-free survival in the treatment group compared with the controls (p=0.01), so we closed the trial early. 131I-lipiodol had no significant toxic effects. INTERPRETATION: In patients with hepatocellular carcinoma, one 1850 MBq dose of intra-arterial 131I-lipiodol given after curative resection significantly decreases the rate of recurrence and increases disease-free and overall survival.

Adolescent↗
PubMed1999

Enhancement of local control in locally advanced node-positive nasopharyngeal carcinoma by adjunctive chemotherapy.

PURPOSE: To determine the efficacy of chemotherapy adjunctive to radical radiotherapy (neoadjuvant +/- adjuvant) in patients with node-positive nasopharyngeal carcinoma (NPC). METHODS AND MATERIALS: All the node-positive patients given adjunctive chemotherapy between 1984-1989 (n = 209, CHEMO) were compared with all the node-positive patients treated by radical radiotherapy alone during the same period (n = 409, NCHEMO). The CHEMO group had significantly more bulky nodes, lower cervical/supraclavicular nodes, and more advanced overall stages than the NCHEMO group because nodal size (> or =24 cm) was used as a selection criterion for chemotherapy (1984-1988 departmental protocol and 1988-1989 prospective randomized trial). The chemotherapy consisted of two courses of neoadjuvant cisplatin (100 mg/m2 D1) and 5-fluorouracil (5-FU) (1 gm/m2 D1-D3) in 191 patients. In addition to the two courses of neoadjuvant, four courses of adjuvant chemotherapy, of the same combination, were given after radical radiotherapy in a further 18 patients. Radical radiotherapy delivered a nasopharyngeal dose of 60-62.5 Gy. In addition, parapharyngeal booster external radiotherapy (20 Gy) was given in the presence of parapharyngeal involvement, and intracavitary brachytherapy (24 Gy) was used to treat any local residual tumor diagnosed at 4-6 weeks after external radiotherapy. Both crude and actuarial rates were compared (survival, distant metastases, and local failures) between CHEMO and NCHEMO for all patients, for individual Ho's overall stage, for patients with nodes of different sizes (< or =3 cm, >3-< or =6 cm, >6 cm), for individual T-stage and individual N-stage, and for patients belonging to different gender and different age groups (<40 years, > or =40 years). Multivariate analyses using the Cox Regression Model were performed to identify significant prognostic factors. RESULTS: With a median follow-up of 5.5 years (range 0.7 to 10 years), CHEMO had significantly less local failures overall than NCHEMO; this was especially true for patients with advanced stages (III + IV). Additionally, in all nodal-size subgroups, in all node-positive T3, and in node-positive T3-Stage IV, there was a significant reduction in local failures after chemotherapy. There was a trend toward fewer local failures in favor of chemotherapy in Stage III, Stage IV, and T3-Stage III (0.05<p< or =0.1). There was no difference in local failures between CHEMO and NCHEMO in Stage II or in T1 and T2. The multivariate analyses identified the administration of adjunctive chemotherapy to be of independent significance in determining the local failure rate for all patients, the T3 (node-positive), and the advanced overall stages (III and IV combined). There was no difference in overall survival, relapse-free survival, and distant metastasis rates between CHEMO and NCHEMO among patients belonging to Stages III and IV despite the presence of more advanced nodal diseases in CHEMO. There were very few late local relapses in patients given adjunctive chemotherapy, in contradistinction to the well-known predisposition of NPC to late local relapses after radical radiotherapy. CONCLUSION: Adjunctive chemotherapy enhanced local control in node-positive NPC in general, and node positive-T3 and -T3-Stage IV in particular with reduction of late local relapses. The enhancement in local control of the locally advanced NPC could be explained by the significant shrinkage of the primary tumor by the neoadjuvant chemotherapy, leading to an increased safety margin between the tumor volume and the radiation volume. We recommend that adjunctive chemotherapy (neoadjuvant +/- adjuvant) should become an integral part of the multimodality curative treatment for patients with node-positive T3 NPC.

Adolescent↗
PubMed1999

Phase II studies with DaunoXome in patients with nonresectable hepatocellular carcinoma: clinical and pharmacokinetic outcomes.

A total of 14 Chinese patients with inoperable hepatocellular carcinoma received a liposomal formulation of daunorubicin (DaunoXome) at a dose equivalent to 100 mg/m2 of the free drug every 3 weeks. Altogether, 12 patients were assessable for response; 2 patients had stable disease for 8 weeks, but all eventually developed progressive disease and there was no responder. The drug was well tolerated, with no evidence of cardiac toxicity being observed. Deterioration of liver-function tests was attributed to progressive tumors in the terminal stage of the disease. Pharmacokinetics studies revealed a biexponential decay for daunorubicin in association with mean initial and terminal half-lives of 1.8 and 7.4 h, respectively, and a mean total clearance of 15.0+/-5.5 ml/min. The AUC ratio between the metabolite daunorubicinol and daunorubicin was 0.07. These data differ markedly from the pharmacokinetics of the free drug.

Adult↗
PubMed1999

A multi-centre randomized phase II study of nolatrexed versus doxorubicin in treatment of Chinese patients with advanced hepatocellular carcinoma.

PURPOSE: A multi-centre randomized phase II study of single agent nolatrexed dihydrochloride versus doxorubicin was undertaken in Chinese patients with advanced hepatocellular carcinoma (HCC) to study and compare the clinical efficacy of the two drugs. METHODS: Fifty-four patients with clinical or histological diagnosis of HCC were randomized in a 2:1 ratio to receive nolatrexed or doxorubicin. Nolatrexed 725 mg/m(2)/day was given by continuous infusion via a central venous device for 5 days and doxorubicin 60 mg/m(2) was given as a rapid intravenous infusion every 3 weeks. RESULTS: No objective responses were observed in either treatment arm. Two patients in the nolatrexed arm and none in the doxorubicin arm had >50% decline in serum alpha-fetoprotein. The median survival for the patients in the nolatrexed and doxorubicin arms was 139 days and 104 days, respectively. Moderate toxicities including leukopenia, thrombocytopenia, mucositis and skin rash were observed in both treatment arms. CONCLUSION: Nolatrexed and doxorubicin are minimally active in the treatment of advanced HCC. Given the small sample size, no difference is observed between the two drugs.

Adult↗
PubMed1999

Increased incidence of tongue cancer after primary radiotherapy for nasopharyngeal carcinoma--the possibility of radiation carcinogenesis.

The aim of this study was to define the risk of tongue and other aerodigestive tract cancers developing after primary radiation therapy for nasopharyngeal carcinoma (NPC). A cohort of 903 patients with non-disseminated NPC given radical radiotherapy between 1984 and 1989 was studied for the incidence of tongue cancer and other malignancies during follow-up. A contemporary cohort of 87 patients with tongue cancer, without a history of NPC, was studied for demographic data, cigarette smoking and alcohol consumption habits. These were then compared with all the NPC patients and with the NPC patients who later developed tongue cancers. There was a significantly increased number of tongue cancers following radiotherapy for NPC. The risk of developing tongue cancer after radiotherapy for NPC was 0.13% per patient per year. There was no increase in the number of other malignancies. The association between NPC and tongue cancer was that of a non-random temporal sequence with tongue cancers following NPC but not in the reverse order. The demographic data and smoking and alcohol consumption history of the 7 NPC patients who subsequently developed tongue cancer were significantly different from the de novo tongue cancer patient population. The absence of common aetiological factors between NPC and tongue cancer and the non-random sequence of tongue cancers occurring after NPC suggests that these seven tongue cancers could be radiation induced. The estimated radiation dose received by the part of the tongue developing cancer was substantial and significantly higher than the dose to the cancer-free tongue. An increase of tongue cancers after radiotherapy for NPC is reported and arguments are made in support of the hypothesis that these were radiation-induced malignancies. We suggest a decrease in the volume of tongue included within the planning target volume of NPC in the absence of oropharyngeal and/or parapharyngeal infiltration. Awareness of the association should make early diagnosis of this likely radiation-induced cancer possible.

Adolescent↗
PubMed1999

Venous thromboembolism occurs frequently in patients undergoing brain tumor surgery despite prophylaxis.

Most Neurosurgical Service patients at our hospital receive venous thromboembolism prophylaxis. In 1995-96, the rate of clinically overt venous thromboembolism was 3.7% among patients undergoing neurosurgery. However, rates were much higher when craniotomy was undertaken for brain tumor. Of 497 who underwent craniotomy for primary (429) or metastatic (68) brain tumor, 47 (9.5%) developed clinically overt venous thromboembolism: 7.5% after primary brain tumor resection and 19% after craniotomy for metastatic cancer. The high rate of venous thromboembolism in craniotomy patients with brain tumor warrants study of alternative measures for preventing thrombus, such as prophylaxis with low molecular weight heparin.

Brain Neoplasms↗
PubMed1999

Netilmicin pharmacokinetics in Hong Kong Chinese cancer patients.

OBJECTIVES: To study the pharmacokinetics of netilmicin in Chinese haematology-oncology patients and to determine the pharmacokinetic differences, if any, between this patient subpopulation of Chinese and Caucasians. METHODS: A prospective study was carried out in the adult oncology unit of a major hospital in Hong Kong. During a 6 week period in 1997, all patients commencing on netilmicin therapy were monitored; the patients' demographics, clinical status, netilmicin dose and regimen, and drug administration/blood sampling time were collected. Pharmacokinetic parameters were generated using the USC*PACK package based on specifics of the patients themselves and Caucasians matched for the same patients' parameters using the Bayesian alogrithms. RESULTS: A total of 22 patients were enrolled into the study. Twenty-nine sets of levels were drawn, but only 25 sets from 18 patients (86%) were interpretable. The predicted peak (7.47+/-1.46 microg ml-1 ) and trough levels (1.39+/-0.96 microg ml-1 ) generated by USC*PACK were found to be significantly higher than the levels observed (6.01+/-1.14 microg ml-1 and 0.93+/-0.71 microg ml-1, respectively). Netilmicin clearance, volume of distribution and rate of elimination were all significantly higher in this Chinese subpopulation than those predicted for matched Caucasians. Conclusion Alterations in the netilmicin pharmacokinetics observed in our study population might be related to the disease state and/or ethics of the study patient population. Direct application of Caucasian based population pharmacokinetic parameters to this subgroup of Chinese patients may not be appropriate and may result in underdose.

Adolescent↗
PubMed1999

Complete pathological remission is possible with systemic combination chemotherapy for inoperable hepatocellular carcinoma.

The purpose of this Phase II study was to determine the response rate, the toxicity, and the effect on survival of the combination of cisplatin, doxorubicin, 5-fluorouracil, and alpha-IFN (PIAF) in advanced unresectable hepatocellular carcinoma. Fifty patients with either unresectable or metastatic disease were treated with PIAF: cisplatin (20 mg/m2 i.v., days 1-4), doxorubicin (40 mg/m2 i.v., day 1), 5-fluorouracil (400 mg/m2 i.v., days 1-4), and alpha-IFN (5 MU/m2 s.c., days 1-4). Treatment was repeated every 3 weeks to a maximum of six cycles. All patients were evaluable for response, toxicity, and survival. As assessed by conventional imaging criteria, there were no complete responses, but 13 patients (26%) had a partial response. Among the 36 patients who had an initially high alpha-fetoprotein level (>500 ng/ml), 15 (42%) had a >50% fall after therapy. Nine patients underwent surgical resection after achieving partial response and, in 4 of these patients, histological examination of the resected specimens revealed no viable tumor cells. All these nine patients are alive, and eight patients remain in complete remission at between 7.6 and 25.8 months at the time of analysis. The overall median survival was 8.9 months. Toxicity was mainly myelosuppression and mucositis. There were two treatment-related deaths due to neutropenic sepsis. PIAF is active in hepatocellular carcinoma despite considerable hematological toxicity. Complete pathological remission is possible with this systemic combination. Apparently, persistent radiological lesions may still represent complete pathological resolution of active disease.

Adolescent↗
PubMed1998

Multimodality treatment of primary lymphoepithelioma-like carcinoma of the lung.

BACKGROUND: Lymphoepithelioma-like carcinoma (LELC) of the lung occurs at a higher frequency in Asian compared with Western patients. Its association with Epstein-Barr virus varies among different ethnic groups. METHODS: Nine patients with primary LELC of the lung treated at a single institution with a multimodality approach comprised of surgery, chemotherapy, and radiotherapy are reported. Chemotherapy was comprised of cisplatin, 100 mg/m2, on Day 1 and 5-fluorouracil, 1 g/m2, on Days 2, 3, and 4. RESULTS: Five male and 4 female patients were treated over a 3-year period. Eight patients were non-smokers. Three patients had operable disease. Two of these patients received adjuvant radiotherapy or chemotherapy and remained free of recurrence at 18 and 20 months, respectively; 1 patient received no adjuvant treatment, and palliative chemotherapy was given for subsequent recurrent disease. Six patients had inoperable disease and received palliative chemotherapy +/- radiotherapy. Five patients had distant metastatic disease at presentation. Of the 7 patients who were evaluable for response to chemotherapy, 71.4% had a partial response and 28.6% had progressive disease. One patient who was evaluable for response to radiotherapy achieved a partial response. CONCLUSIONS: Primary LELC of the lung has a high rate of systemic metastasis and is highly chemosensitive. A multimodality approach to the management of this disease is recommended.

Adult↗