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Biomedical subjects

L C Chan

Publications and source records attributed to L C Chan.

At least 109 records · Page 6Linked to original sources
PubMed1997

Hematological features and treatment outcome in acute myeloid leukemia with t(8;21).

We analyzed the hematological features and treatment outcome in 18 patients with t(8;21) acute myeloid leukemia (AML) diagnosed in Queen Mary Hospital, Hong Kong. They comprised 15 cases of M2, two cases of M4 and one case of M1 according to FAB criteria. Auer rods (17 cases) and dysgranulopoietic features (15 cases) were very frequently observed. Two cases showed marrow eosinophilia while blast cells in one patient demonstrated erythrophagocytic activity. Chromosome changes in addition to t(8;21) were seen in 14 patients, the most common of which was loss of a sex chromosome (10 cases). Of the 14 patients treated with intensive chemotherapy, 13 (93 per cent) entered complete remission with a median event-free survival (EFS) and overall survival (OS) of 11 and 24 months respectively. The probability of EFS and OS at 3 years were 33 +/- 14.3 per cent and 55.1 +/- 15.6 per cent respectively with a median duration of follow-up of 22 months. When compared with AML having no t(8;21) treated similarly in the same period, we could not demonstrate a better clinical outcome for t(8;21) AML.

Adolescent↗
PubMed1997

Clinical presentation, hematologic features and treatment outcome of childhood acute lymphoblastic leukemia: a review of 73 cases in Hong Kong.

Seventy-three consecutive cases of childhood acute lymphoblastic leukemia (ALL) diagnosed and managed in Queen Mary Hospital over a 10-year period from 1985 to 1994 were retrospectively analysed for their presenting features and treatment outcome. The 48 boys and 25 girls ranged in age from 0.4 to 14.2 years (median: 4.3 years). Bone and joint pain was a relatively common presenting feature besides fever, hepatosplenomegaly and lymphadenopathy. Immunophenotyping of blast cells showed: 51 B-cell precursor ALL, one B-ALL, 10 T-ALL and three myeloid-antigen positive ALL. Eight cases were unclassified since immunophenotyping had not been performed. Out of the 73 patients, treatment outcome was analysed in 20 cases treated with UKALL-VIII regimen and 28 cases treated with either the UKALL-XI regimen or the Hong Kong Children Cancer Study Group (HKCCSG) protocol which was modelled upon UKALL-XI. Although complete remission rates were similar between the two groups, patients treated with the former regimen that was less intensified suffered more relapses than the latter (56 per cent versus 21 per cent, P = 0.04). There were, however, no significant differences both in event-free survival (38.2 +/- 11.2 per cent versus 71.3 +/- 9.3 per cent, P = 0.12) and overall survival (70.0 +/- 10.2 per cent versus 79.6 +/- 8.3 per cent, P = 0.41) between the two groups at 3 years by long-rank test. With the use of risk-directed therapy and improved supportive care, two-thirds of our patients are able to enjoy long-term event-free survival.

Adolescent↗
PubMed1997

Cytogenetic abnormalities in pediatric myelodysplastic syndrome: a report of three cases.

Three consecutive cases of pediatric myelodysplastic syndrome (MDS) diagnosed over a three-year period in Queen Mary Hospital, Hong Kong, were described. Depending on the classification system used, they comprised two cases of chronic myelomonocytic leukemia (CMMoL) of which one can be reclassified as juvenile chronic myeloid leukemia (JCML) and one cases of refractory anemia with excess of blasts (RAEB) or an alternative diagnosis of atypical CML. Cytogenetic abnormalities were detected in all of them on examination of bone marrow cells. Of the two CMMoL, one had monosomy 21, whereas the other had hypodiploidy. The patient with RAEB had a complex karyotype of 46,X,del(X)(q24),t(1;7) (p22;q32),add(15)(q26)(8). The balanced translocation (1;7) seen in this patient was exceedingly rare and, to the best of our knowledge, was reported only twice in the literature. The karyotypic abnormalities that we saw in our patients were not well recognized in pediatric MDS. This report emphasizes the importance of cytogenetic study in children suspected of suffering from MDS, which remains a rare disorder of childhood, and a need to rationalize current classification schemes.

Child↗
PubMed1997

t(High) frequency of telomeric associations in human ovarian surface epithelial cells transformed by human papilloma viral oncogenes.

Viral oncogenes are commonly used to transform and extend the in vitro life span of human epithelial cells. We have established 7 cell lines of human ovarian surface epithelial cells using human papilloma viral oncogenes (HPV-E6E7 ORFs). Cytogenetic analysis of the cell lines revealed a high frequency of telomeric associations ranging from 30% to 100% of the metaphases examined. The short arms of chromosomes 16, 19, 21, and 22 showed a higher rate of telomeric association. Telomeric association with other chromosomal ends appears to be random. Fusion of 2 chromosomes ends may contribute to the genomic instability of transformed cells and lead to further genetic alterations involved in malignant transformation such as gene amplication and loss of heterozygosity. This is the first report describing a high frequency of telomeric associations in human ovarian epithelial cells transformed by HPV oncogenes.

Cell Transformation, Neoplastic↗
PubMed1997

Acute myeloid leukemia following psoralen with ultraviolet A therapy: a fluorescence in situ hybridization study.

A woman with mycosis fungoides treated by psoralen with ultraviolet A (PUVA) and electron beam therapy developed acute myeloid leukemia (AML) three years later. Karyotypic analysis of the leukemia cells revealed monosomy 7. Fluorescence in situ hybridization showed that the monosomy 7 clone had accounted for about a third of the marrow cells after PUVA treatment, but replaced the entire marrow at leukemic transformation. These findings were consistent with a secondary AML evolving from an underlying myelodysplasia, supporting that PUVA therapy might have a mutagenic effect on hematopoietic cells. This might be related to its effect on circulating hematopoietic stem cells.

Chromosomes, Human, Pair 7↗
PubMed1997

Clustering of childhood leukaemia in Hong Kong: association with the childhood peak and common acute lymphoblastic leukaemia and with population mixing.

Incidence data of childhood leukaemia (CL) in Hong Kong (1984-90) have been analysed for evidence of variation between small areas. All cases (n=261) were classified by morphological cell type, with the majority (n=205) being acute lymphoblastic leukaemia (ALL), and haematological review has permitted immunophenotypic classification for 73% of these. The data have been examined for evidence of spatial clustering within small census areas (TPUs) and for association with population mixing, with attention focused on those subgroups (especially the childhood peak of ALL--taken here to be diagnoses in children from 24 months up to the seventh birthday--and common ALL) which, it has been hypothesized, may be caused by unusual patterns of exposure and response to common infections. For the whole of Hong Kong, there was evidence of spatial clustering of ALL at ages 0-4 years (P = 0.09) and in the childhood peak (P<0.05). When these analyses were restricted to TPUs where extreme population mixing may have occurred, overall incidence was elevated and significant evidence of clustering was found for ALL (P<0.007) at these ages and for the common ALL in the childhood peak (P = 0.032). Replication of the analyses for subsets of leukaemia that were not dominated by the childhood peak of ALL found no evidence of clustering. This is the first investigation of an association between population mixing and childhood leukaemia in Asia and the first to include clustering and to consider particular subsets. The results are supportive of the 'infectious' aetiology hypothesis for subsets of childhood leukaemia, specifically common ALL in the childhood peak.

Adolescent↗
PubMed1997

The spectrum of chronic lymphoproliferative disorders in Hong Kong. A prospective study.

We report the incidence of the chronic lymphoproliferative disorders evolving with leukaemia in Hong Kong. Our findings demonstrate that B cell malignancies are significantly more frequent than mature T cell neoplasms, a picture similar to that seen in Western countries but different from other Eastern countries, eg Japan, where T cell malignancies are more frequent. In contrast to the West, where chronic lymphocytic leukaemia (CLL) is the most common disorder, in Hong Kong there is a clear predominance of B cell lymphomas in leukaemic phase accounting for two-thirds of the cases and particularly those displaying lymphoplasmacytic features or with villous lymphocytes. CLL in Hong Kong has similar clinical and laboratory features to the disease in patients from the West. Distinct disease categories, rare in the West such as the variant form of hairy cell leukaemia and T cell prolymphocytic leukaemia, are also documented. It is unclear whether the differences in prevalence of disease subtypes between Hong Kong and the West relate to different genetic background or environmental factors determinant of the development or progression of the leukaemia. Further studies investigating the genetic/molecular lesions may help to clarify whether the aetiopathogenesis of the lymphoid disorders in Hong Kong is similar to that of Western countries.

Adult↗
PubMed1997

Robertsonian translocation as an acquired karyotypic abnormality in leukaemia.

Robertsonian translocations, although relatively common as a constitutional genetic aberration, are rarely encountered in leukaemia. We report a case of acute myeloid leukaemia which showed an acquired Robertsonian translocation in the form of der(14;21) by cytogenetic analysis of leukaemic cells. This was confirmed by the PHA-stimulated culture of peripheral blood lymphocytes. A review of the literature identifies only eight reported cases of acquired Robertsonian translocations in leukaemia. In the majority of cases the Robertsonian translocation occurs as a secondary change in a complex abnormal clone, whereas in two out of nine patients reported, including ours, it is found as a sole karyotypic abnormality.

Acute Disease↗
PubMed1997

Glucan-induced disease resistance in tiger shrimp (Penaeus monodon).

Non-specific disease resistance induced by yeast cell wall extract, beta-1,3-1,6-glucan, was demonstrated in the tiger shrimp. In this study beta-1,3-1,6-glucan was administered to shrimps by immersion before culturing and orally during the culturing period. Challenge of the treated shrimps with the virulent pathogens, Vibrio vulnificus and viral agents extracted from the white spot syndrome victims, yielded promising results. The tolerance of glucan-treated shrimps was slightly enhanced to stresses including catching, transport and ammonia. The growth and survival rates of treated and untreated shrimps were not significantly different. Therefore, we suggest that beta-1,3-1,6-glucan can be used as an immuno-stimulant of cultured shrimps and may benefit shrimp farmers.

Adjuvants, Immunologic↗
PubMed1996

Malignant peripheral neuroectodermal tumor in an infant with neurofibromatosis type 1.

A case of multifocal malignant peripheral neuroectodermal tumor (PNET) arising from a plexiform neurofibroma in a 4-month-old Chinese boy with neurofibromatosis type 1 (NF-1) is described. Cytogenetic culture demonstrated hypotriploid karyotype with an abnormal clone characterized by 59-60, XY, +2, +3, +6, +8, +8, +12, +i(13)(q10), +der(14)t(1;14)(q21;q32), +16, +19, +20, +mar[cp3] with no apparent abnormality of chromosome 17. The child was treated with combination chemotherapy comprising ifosphamide, vincristine and doxorubicin. Despite initial partial response the child finally died of tumor progression and pulmonary metastases 8 months after diagnosis. We believe this is the first reported case of PNET in a child with NF-1 and may support an association between these two disorders of neural crest origin.

Fatal Outcome↗
PubMed1996

All-trans retinoic acid (ATRA) in the treatment of acute promyelocytic leukemia (APL).

Acute promyelocytic leukemia is characterized by the reciprocal translocation of chromosomes 15 and 17. All-trans retinoic acid (ATRA) efficiently induces differentiation of the abnormal promyelocytes. In this study, we had used ATRA as the primary induction therapy for 17 newly diagnosed patients, and as the salvage therapy for 11 patients who relapsed from or were resistant to chemotherapy. All patients received subsequent consolidation chemotherapy. Complete remission (CR) rate, early death rate (within 28 days of diagnosis) were then compared to an historical control of 50 APL patients treated with combination chemotherapy; and event-free survival of the 17 newly diagnosed patients was compared to the historical control. In the ATRA group, 26 of the 28 patients (93 per cent) attained complete remission. Two of 28 (7 per cent) died within 28 days of ATRA therapy. There was no case of primary resistance to ATRA. Combination chemotherapy was added to ATRA in five patients due to rapidly increasing leucocyte count. There was one case of retinoic acid syndrome which resolved with steroid. When compared to the 50 cases of historical control, there is significant improvement in the overall CR rate (92 per cent versus 59 per cent, p = 0.001) and a significant reduction in the early mortality rate (7 per cent versus 41 per cent, p = 0.001). Moreover, when the survival result of the 17 newly diagnosed patients were compared with the control, there is a significant improvement in the projected EFS at 3 years (64 per cent versus 25 per cent, p = 0.007). In conclusion, ATRA was shown to improve the CR rate, reduce induction mortality and significantly prolong the event-free survival.

Adolescent↗
PubMed1996

Pure red cell aplasia: clinical features and treatment results in 16 cases.

Pure red cell aplasia (PRCA) is a rare hematological disease characterized by selective marrow erythroid aplasia. We report the clinical features and treatment results of 16 Chinese patients with PRCA. Nine (56%) cases were not associated with any underlying disorders and were considered idiopathic, while seven patients (44%) had associated diseases, three involving the thymus, two with T large granular lymphocyte leukemia (T-LGLL), and one each with Stevens-Johnson syndrome and acute hepatitis A. Conventional-dose corticosteroid therapy resulted in complete remission in three of 13 patients. Cyclosporin A was used in six patients. There were three complete and one partial remissions. High-dose methylprednisolone was ineffective in four patients who failed conventional-dose corticosteroids but achieved complete remission in one patient with thymoma who did not respond to thymectomy. Antithymocyte globulin was used in four patients, resulting in partial remission in only one patient with concomitant T-LGLL. Intravenous gamma globulin and danazol were ineffective in three patients. Thymectomy was performed in two patients, with one patient remitting. This is the largest series of PRCA reported in an oriental population. Our results indicate that treatment of PRCA may still be problematic and better therapeutic strategy will have to be defined.

Adrenal Cortex Hormones↗
PubMed1996

Comparison of the HbH inclusion test and a PCR test in routine screening for alpha thalassaemia in Hong Kong.

AIM: To compare the haemoglobin (Hb) H inclusion test with a polymerase chain reaction (PCR) test in routine screening for alpha thalassaemia. METHODS: Ninety nine peripheral blood samples from Chinese patients with mean corpuscular volume below 80 fl were screened for alpha thalassaemia using the HbH inclusion test and by PCR utilising primers bridging the common deletion breakpoint of the South East Asian (--SEA/) deletion. RESULTS: The HbH inclusion test was positive in 78 (79%) patients, 73 (93.7%) of whom carried the (--SEA/) deletion on analysis of their DNA by PCR, as did one patient with a negative HbH inclusion test. CONCLUSIONS: These results suggest that in areas with a high prevalence of the (--SEA/) deletion, such as Hong Kong, the HbH inclusion test can be replaced by PCR as the investigation of choice in screening for alpha thalassaemia.

Base Sequence↗