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D W Chan

Publications and source records attributed to D W Chan.

At least 73 records · Page 4Linked to original sources
PubMed1998

Nonpalpable stage T1c prostate cancer: prediction of insignificant disease using free/total prostate specific antigen levels and needle biopsy findings.

PURPOSE: Approximately 25% of radical prostatectomies performed for stage T1c disease show potentially insignificant prostate cancer. We previously reported the use of serum prostate specific antigen (PSA) density and needle biopsy findings to predict potentially insignificant cancer. We now evaluate whether using free/total serum PSA levels along with needle biopsy findings can better predict tumor significance. MATERIALS AND METHODS: We studied 163 radical prostatectomy specimens of stage T1c prostate cancer in which free/total serum PSA levels were determined. Free/total serum PSA levels were measured with Tandem-MP PSA assays. Insignificant prostate cancers were organ confined with tumor volumes less than 0.5 cc and Gleason score less than 7. Advanced tumors were either Gleason score 7 or greater, established extraprostatic extension with positive margins, or positive seminal vesicles or lymph nodes. Other cases were considered as moderate tumor. Moderate and advanced tumors were considered significant. RESULTS: Of the tumors 30.7% were insignificant, 49.7% moderate and 19.6% advanced. The best model to predict preoperatively insignificant tumor was a free/total PSA of 0.15 or greater and favorable needle biopsy findings (less than 3 cores involved, none of the cores with greater than 50% tumor involvement and Gleason score less than 7). Using this model of the 18 tumors predicted to be insignificant 17 were insignificant for a positive predictive value of 94.4%. Of the 145 cases that were predicted to be significant 112 were correctly predicted for a negative predictive value of 77.2%. There was only 1 tumor predicted to be insignificant which was classified as moderate. No tumor predicted to be insignificant was advanced. CONCLUSIONS: In conjunction with needle biopsy findings, free/total PSA levels accurately predict insignificant tumor in stage T1c disease.

Biopsy, Needle↗
PubMed1998

Analytical and clinical evaluation of an electrochemiluminescence immunoassay for the determination of CA 125.

The CA 125 II assay on the Elecsys(R) 2010 analyzer was evaluated in an international multicenter trial. Imprecision studies yielded within-run CVs of 0.8-3.3% and between-day CVs of 2.4-10.9%; CVs for total imprecision in the manufacturer's laboratory were 2.4-7.8%. The linear range of the assay extended to at least 4500 kilounits/L (three decades). Interference from triglycerides (10.3 mmol/L), bilirubin (850 micromol/L), hemoglobin (1.1 mmol/L), anticoagulants (plasma), and several widely used drugs was undetectable. Method comparisons with five other CA 125 II assays showed good correlation but differences in standardization. A 95th percentile cutoff value of 35 kilounits/L was calculated from values measured in 593 apparently healthy (pre- and postmenopausal) women. In 95% of patients with benign gynecological diseases CA 125 was </=190 kilounits/L; 63% of patients with newly diagnosed ovarian carcinoma had values >190 kilounits/L. A comparison of CA 125 values obtained with the Elecsys test and with other common CA 125 tests in monitored patients being treated for ovarian cancer showed identical patterns. In conclusion, the Elecsys CA 125 II assay is linear over a broad range, yields precise and accurate results, is free from interferences, and compares well with other assays.

Adult↗
PubMed1997

Recommended prostate-specific antigen testing intervals for the detection of curable prostate cancer.

OBJECTIVE: To evaluate prostate-specific antigen (PSA) testing intervals that maintain the detection of curable cancer and reduce unnecessary testing. DESIGN AND PATIENTS: Historical prospective study of serial PSA measurements at 2- and 4-year intervals from frozen serum samples of 40 men who eventually developed prostate cancer and 272 men without prostate cancer who were participants in a prospective aging study (Gerontology Research Center of the National Institute on Aging, the Baltimore Longitudinal Study of Aging) and the case series of 389 consecutive men treated surgically for nonpalpable prostate cancer. MAIN OUTCOME MEASURES: Probability of a PSA conversion to 4.1 to 5.0 ng/mL and to greater than 5.0 ng/mL at 2 and 4 years and probability of detecting curable prostate cancer by age and PSA level. RESULTS: When the pretreatment PSA level was less than or equal to 4.0 ng/mL, nonpalpable prostate cancers were highly likely (34/36, 94%) to be curable (organ-confined or capsular penetration with Gleason score < 7 and negative margins), and the majority (25/36, 69%) were small cancers (confined tumor < or = 0.5 cm3 with no Gleason pattern 4 or 5). When the pretreatment PSA level was greater than 4.0 ng/mL and less than or equal to 5.0 ng/mL, cancers were highly likely to be curable (32/36, 89%), and a minority were small cancers (12/36, 33%). When the pretreatment PSA level was greater than 5.0 ng/mL, 96 (30%) of 317 cancers were noncurable. The PSA conversion (for cancer cases) to a level at which cure is less likely (> 5.0 ng/mL) is rare (0%) after 2 or 4 years when the initial PSA is less than 2.0 ng/mL. PSA conversion to a range at which cancers are likely to be curable and less likely to be small (4.1-5.0 ng/mL) is rare after 2 years (0%-4%) when the baseline PSA level is less than 2.0 ng/mL but common when the baseline PSA level is between 2.1 and 3.0 ng/mL (27%) or 3.1 and 4.0 ng/mL (36%). CONCLUSIONS: These data suggest that for men with no cancer suspected on digital rectal examination, a PSA level of 4.0 to 5.0 ng/mL is an acceptable range for maintaining the detection of curable prostate cancer and a 2-year PSA testing interval is not likely to miss a curable prostate cancer when the initial PSA level is less than 2.0 ng/mL. Recognizing that 70% of a screened population between the ages of 50 years and 70 years have PSA levels less than 2.0 ng/mL, elimination of annual PSA testing for these men would result in large health care cost savings.

Aged↗
PubMed1997

Defensive styles and psychological symptoms among Chinese adolescents in Hong Kong.

Specific defenses were assessed in a cohort of 490 Chinese adolescent boys and girls in Hong Kong using the Chinese version of the short form of the Defense Style Questionnaire (DSQ). Commonly employed defenses included anticipation, sublimation, and reaction formation, indicating that adolescents tended to deal with stressors and emotional conflicts with relatively mature or adaptive defenses. Factor analysis revealed that a mature or adaptive defensive style could generally be distinguished from an immature or maladaptive defensive style, but a neurotic defensive style was not differentiable for this group of adolescents. Results also indicated that general and specific psychological symptoms were associated with the use of immature defenses characterized by somatization and externalizing emotional conflicts through acting out and misattribution. The use of the DSQ for assessing defenses among Chinese adolescents and cross-cultural comparisons are discussed.

Adolescent↗
PubMed1997

Radical prostatectomy as treatment for prostate-specific antigen-detected stage T1c prostate cancer.

The use of serum prostate-specific antigen (PSA) measurement as a method for early detection of prostate cancer has increased the detection of clinically and pathologically localized prostate cancer. Clinical stage T1c was introduced to describe cancers discovered on prostate biopsy as a result of an abnormal serum PSA level without a palpable prostatic abnormality on digital rectal examination. The majority of men with stage T1c tumors have significant disease warranting treatment. We report the results of anatomic radical retropubic prostatectomy as therapy for PSA-detected stage T1c prostate cancer in 340 men treated at a single institution. In all, 17 men (5%) have had a recurrence with 2.3 +/- 1.2 years of follow-up, 15 of whom have experienced an isolated biochemical PSA recurrence only. The overall actuarial biochemical PSA recurrence-free rate at 6 years is 87%, with pathologic stage being the best single indicator of the likelihood of progression. Although a longer period of follow-up is needed, this interim report suggests that these men can be cured by surgery at rates equal to or better than those of previously reported radical prostatectomy series.

Actuarial Analysis↗
PubMed1997

Bone to total alkaline phosphatase ratios improve sensitivity and specificity of bone alkaline phosphatase immunoassays.

OBJECTIVES: Evaluate the ability of two bone alkaline phosphatase (ALPB) immunoassays (Ostase, Hybritech Inc and Alkphase-B, Metra Biosystems) to clinically differentiate between osseous and non-osseous ALP sources. DESIGN AND METHODS: Specimens from patients with either liver or bone disease (Paget's disease or metastatic cancer) were analyzed by both methods. RESULTS: There was a good correlation between these two assays. Values for ALPB, whether determined as a concentration by the Ostase assay or as an activity by the Alkphase-B assay, were similar for subjects with liver disease or bone disease. However, total ALP (ALPT) activity was higher in liver disease compared to bone. When ALPB was expressed in relation to ALPT, ratios were significantly greater in subjects with bone disease than in those with liver disease. ALPB/ALPT ratios improved the specificity of the Ostase assay from 52% to 86% and the Alkphase-B assay from 58% to 74%. CONCLUSIONS: These two ALPB assays have good analytical performance and their clinical utility can be enhanced by expressing ALPB values in relation to ALPT activity.

Adult↗
PubMed1997

Prostate-specific antigen in men born with bladder exstrophy.

OBJECTIVES: To determine serum levels of prostate-specific antigen (PSA) in men born with bladder exstrophy and to investigate the clinical utility of this test in the bladder exstrophy population. METHODS: Ten men aged 19 to 45 years with a history of bladder exstrophy underwent digital rectal examination and free and total serum PSA determinations. Immunohistochemistry for PSA and prostate-specific acid phosphatase (PSAP) was performed on archival prostate tissue from 1 man with bladder exstrophy. RESULTS: Free and total serum PSA levels for all patients were measurable and below the upper limit for established age-specific reference ranges for normal men. Both PSA and PSAP were detectable by immunohistochemistry in prostate epithelial cells of a man with bladder exstrophy. CONCLUSIONS: Men born with bladder exstrophy have detectable serum PSA levels. However, because prostate cancer in men with bladder exstrophy has not been reported, whether PSA will have a clinical role as a serum tumor marker for prostate cancer in this population remains to be determined. If so, the PSA reference range for men with the exstrophy condition will need to be defined. Because prostate histology in men with exstrophy resembles that of normal men, careful clinical monitoring for benign and malignant tumors should not be overlooked in this particular population.

Adult↗
PubMed1997

Percentage of free prostate-specific antigen in sera predicts aggressiveness of prostate cancer a decade before diagnosis.

OBJECTIVES: To evaluate serial measurements of free and total prostate-specific antigen (PSA) as a predictor of prostate cancer aggressiveness. METHODS: Twenty men diagnosed with adenocarcinoma of the prostate in the pre-PSA era had serum PSA measurements made on multiple stored frozen sera samples available for up to 18 years prior to diagnosis. Subjects were categorized as having aggressive cancer (n = 12) based on the presence of clinical Stage T3, or nodal or bone metastases (N+, M+), or pathologic positive-margin disease, or a Gleason score of 7 or greater; nonaggressive cancer (n = 8) was identified by the absence of these criteria. RESULTS: There was no statistically significant difference in free PSA levels among men with aggressive and nonaggressive prostate cancers from 0 to 15 years before diagnosis. Total PSA levels were significantly different between the groups by 5 years before diagnosis (P = 0.04). At a time when total PSA levels were not different between groups (10 years before diagnosis), there was a statistically significant difference in the percentage of free PSA between aggressive and nonaggressive cancers (P = 0.008). Among 14 men who had sera available for analysis at 10 years before diagnosis, all 8 men with aggressive cancers had a percent free PSA of 0.14 or less; this compares with only 2 of 6 men (33%) with nonaggressive cancer. CONCLUSIONS: These data suggest that the percentage of free PSA in sera is predictive of tumor behavior at a time when total PSA levels provide no information on tumor aggressiveness. Evaluation of the percentage of free serum PSA may be helpful in making the decision between expectant management and treatment for those men who are diagnosed with early prostate cancers by PSA testing.

Adenocarcinoma↗
PubMed1997

Molecular forms of prostate-specific antigen and human kallikrein 2 (hK2) in urine are not clinically useful for early detection and staging of prostate cancer.

OBJECTIVES: Prostate-specific antigen (PSA), a member of the human kallikrein (hK) family, is the most important tumor marker for early detection, staging, and monitoring of men with prostate cancer today. However, the sensitivity of serum PSA is not sufficient to be used alone for prostate cancer screening. Recently, it was reported that the serum-to-urinary total PSA ratio improves the detection of men with prostate cancer, especially in men with a serum total PSA level between 4.0 and 10.0 ng/mL. We tested this hypothesis by evaluating the clinical usefulness of this PSA ratio as well as the use of the different molecular forms of PSA and human kallikrein 2 (hK2) in urine for detection and staging of prostate cancer. METHODS: One hundred ten fresh, midstream urine specimens (prostate cancer 62, benign prostatic hyperplasia [BPH] 38, healthy male control 5, women 5) were collected. Serum total PSA, urine total PSA, urinary free PSA, urinary alpha 1-antichymotrypsin-bound PSA, and urinary hK2 levels were determined by monoclonal antibody assays (Hybritech Inc.). The serum-to-urinary total PSA ratio was calculated. RESULTS: The serum-to-urinary total PSA ratio did not accurately distinguish between men with BPH and men with prostate cancer. There was no significant difference between the urinary levels of any of the molecular forms of PSA or hK2 between men with prostate cancer and men with BPH. Among men with prostate cancer, neither urinary hK2 nor urinary levels of any of the molecular forms of PSA correlated with age, pathologic stage, or Gleason grade. CONCLUSIONS: In our study, the serum-to-urinary total PSA ratio did not improve the detection of men with prostate cancer. Furthermore, measurement of the molecular forms of PSA and hK2 in urine did not improve the detection or staging of prostate cancer over serum PSA alone.

Aged↗
PubMed1997

Prostate-specific antigen. Its discovery and biochemical characteristics.

The search for a more sensitive and specific marker for prostate cancer as well as for use in forensic investigations led to the discovery of PSA. Utilization of the purified protein resulted in the development of many immunoassays that are now in widespread use and have been applied successfully to the detection and monitoring of prostate cancer. Subsequent investigation into the biochemical characteristics of PSA revealed free and complexed forms of PSA in serum whose measurement now may provide additional clinical benefit. Further research into the molecular and biochemical properties of PSA as well as improvements in measurement techniques no doubt will lead to new applications and enhanced clinical use for this important tumor marker.

Humans↗
PubMed1997

Circulating thrombomodulin levels and clinical correlates in pregnant diabetics.

The object of this study was to investigate the relationship of thrombomodulin (TM) and glycosylated hemoglobin (HbA1C) in pregnant diabetics and to determine clinical correlates. We performed a prospective cohort study of 53 patients: 25 women with insulin-dependent diabetes (group 1) and 28 with gestational diabetes (group 2). Group 1 underwent monthly determinations of HbA1C and TM. Group 2 underwent determination at 36 weeks of gestation. There was a significant difference in HbA1C between groups 1 and 2 (p=0.0005), but there was no difference in TM. There was no correlation between TM and HbA1C. TM levels correlated positively with serum creatinine (r=0.46, p=0.002), proteinuria (r=0.48, p=0.007), and duration of diabetes (r=0.41, p=0.042). TM was significantly higher in diabetics of advanced White Classification (p=0.008). With good control, TM does not appear to be elevated in a diabetic pregnancy. TM may be a marker of endothelial damage that correlates more with duration of diabetes and renal disease than with HbA1C, which reflects short-term control.

Adult↗
PubMed1997

Use of Truquant BR radioimmunoassay for early detection of breast cancer recurrence in patients with stage II and stage III disease.

PURPOSE: The Truquant BR radioimmunoassay (RIA) (Biomira Diagnostics Inc, Rexdale, Canada) uses the monoclonal antibody B27.29 to quantitate the MUC-1 gene product (CA 27.29 antigen) in serum. We evaluated CA 27.29 antigen in a controlled, prospective clinical trial for its ability to predict relapse in stage II and stage III breast cancer patients. PATIENTS AND METHODS: Over a 2-year period, 166 patients who had completed therapy for stage II (80.1%) or III (19.9%) breast cancer and were clinically free of disease were serially tested for CA 27.29 antigen levels. The study was double-masked and cancer recurrence was documented based on clinical findings. Patients with two consecutive CA 27.29 antigen test results above the upper limit of normal were considered positive. RESULTS: The Truquant BR RIA had a sensitivity of 57.7%, specificity of 97.9%, positive predictive value of 83.3%, and negative predictive value of 92.6%. The recurrence rate was 15.7%. A Cox regression analysis showed that the only variable to correlate with recurrent disease was the CA 27.29 antigen test result. Patients with a positive test result had increased odds of having a recurrence (odds ratio, 6.8; P < .00001). The test was effective in predicting recurrence in patients with both distant and locoregional disease. In a subgroup of patients with bone pain, CA 27.29 antigen level was found to identify reliably patients who would subsequently develop recurrent disease. CONCLUSION: These data demonstrate that the Truquant BR RIA can be used as an aid to predict recurrent breast cancer in patients with stage II and III disease.

Adult↗
PubMed1997

Prostate-specific antigen: update 1997.

Prostate-specific antigen (PSA) is the most important tumor marker for prostate cancer, although it is not a perfect marker as it is not cancer-specific. PSA, a member of the human kallikrein family, is present in two molecular forms in serum: free and complexed to protease inhibitors. PSA is now commonly measured on automated immunoassay systems employing monoclonal or polyclonal antibodies. Results from different assays can vary since some assays are not equimolar and react to the free and complexed forms differently. Utilization of the molecular forms of PSA is one approach to improve the sensitivity and specificity of the PSA assay. Patients with prostate cancer have a greater percentage of PSA bound to alpha1-antichymotripsin (ACT) than those without cancer. Measurement of the free to total PSA ratio in the diagnostic gray zone (usually 4-10 micrograms/liter of total PSA), where prostate cancer and benign prostatic hyperplasia (BPH) overlap, has been shown to eliminate between 16 and 79% of unnecessary biopsies. Free to total PSA cutoffs are influenced by the sensitivity and specificity values chosen, the reflex range for total PSA used, differences in free PSA assays, differences in populations studied, and factors such as total PSA concentrations, age, and prostate gland size. In addition to the molecular forms of PSA, age-specific reference ranges, rate of change of PSA concentrations (PSA velocity), ratio of serum PSA to prostate volume (PSA density), and neural network derived indices have been employed to improve the clinical utility of PSA measurements.

Humans↗
PubMed1997

Detection of T-cell receptor delta gene rearrangement by clonal specific polymerase chain reaction.

A sensitive and specific technique to detect minimal residual disease for T-cell malignancies was explored. Southern analysis and polymerase chain reaction (PCR) were used to detect the rearranged V-D-J segment of T-cell receptor delta (TCR delta) gene from malignant cell specimens of patients with leukemia and lymphoma of T-cell lineage. The PCR product was sequenced and from the DNA sequences of the V-D-J region, a 3' antisense primer was designed and synthesized for clonal specific PCR (CS-PCR). Seven of the 22 T-ALL (32%) and 5 of 18 (28%) T-cell lymphoma showed clonal rearrangement by Southern analysis. Six of the 7 (86%) T-ALL and 4 of the 5 (80%) T-cell lymphoma which were Southern positive were also positive by TCR delta PCR. The PCR products of four cases of T-ALL showing clonal pattern by TCR delta PCR amplification were successfully sequenced and CS-PCR amplification performed. CS-PCR detected with confidence specific clonal rearrangement in a mixture containing 0.003% of malignant cells. Marrow specimens obtained at diagnosis and subsequent follow-ups from the 4 T-ALL patients were studied by Southern analysis, TCR delta PCR and CS-PCR. The first patient was in continuous morphological complete remission for more than 3 years and had persistently negative Southern, TCR delta PCR and CS-PCR results on follow-up. Initial follow-up marrow samples from the second patient had persistently positive CS-PCR results while they were still morphologically and TCR delta PCR negative and the patient had a frank leukemic relapse at 18 months. The other two patients had persistent disease by conventional morphological examination, Southern analysis, TCR delta PCR and CS-PCR studies were all positive as expected. CS-PCR is a highly specific and sensitive technique in detecting minimal residual disease for T-cell malignancies. Its potential applications warrant further clinical evaluation and correlation.

Base Sequence↗
PubMed1997

The effects of modifying proficiency testing materials on thyroid function test results. A College of American Pathologists Ligand Assay Survey Study.

OBJECTIVE: To gain insight on the matrix effects, and possible clinical implications, resulting from diluting and concentrating proficiency testing survey material used for the measurement of thyroid function tests. DESIGN: To the standard set of five proficiency survey samples, three supplementary "Wildcard" samples were added. These additional samples were manufactured by overfilling and underfilling vials prior to lyophilization so as to vary the thyroxine-binding protein concentrations. Survey participants measured thyroxine, free thyroxine, and the triiodothyronine uptake and related tests on the Wildcard samples. In addition, free thyroxine indices were calculated. SETTING: The first mailing of the 1995 College of American Pathologists (CAP) Ligand Assay--Series 1 Survey. MAIN OUTCOME MEASURES: Results obtained from the regular set of survey samples and the Wildcard set were compared to values expected by the laws of conservation of matter and mass action. PARTICIPANTS: The approximately 2000 participants of the first mailing of the 1995 CAP Ligand Assay--Series 1 Survey. RESULTS: Numerous assays systems did not give the predicted results, including all of the single-step radioimmunoassays for free thyroxine and over three quarters of free thyroxine index determinations. CONCLUSIONS: Varying the dilution of proficiency survey material produced results that were not predicted by the laws of conservation of matter and of mass action. Although these observations may have been the result of matrix effects, one cannot rule out the possibility that certain thyroid assays may not work in clinical situations having abnormal thyroxine-binding protein concentrations.

Data Collection↗
PubMed1996

Interleukin-1 beta-converting enzyme-like protease cleaves DNA-dependent protein kinase in cytotoxic T cell killing.

Cytotoxic T cells (CTL) represent the major defense mechanism against the spread of virus infection. It is believed that the pore-forming protein, perforin, facilitates the entry of a series of serine proteases (particularly granzyme B) into the target cell which ultimately leads to DNA fragmentation and apoptosis. We demonstrate here that during CTL-mediated cytolysis the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs), an enzyme implicated in the repair of double strand breaks in DNA, is specifically cleaved by an interleukin (IL)-1 beta-converting enzyme (ICE)-like protease. A serine protease inhibitor, 3,4-dichloroisocoumarin (DCl), which is known to block granzyme B activity, inhibited CTL-induced apoptosis and prevented the degradation of DNA-PKcs in cells but failed to prevent the degradation of purified DNA-PKcs by CTL extracts. However, Tyr-Val-Ala-Asp-CH2Cl (YVAD-CMK) and other cysteine protease inhibitors prevented the degradation of purified DNA-PKcs by CTL extracts. Furthermore, incubation of DNA-PKcs with granzyme B did not produce the same cleavage pattern observed in cells undergoing apoptosis and when this substrate was incubated with either CTL extracts or the ICE-like protease, CPP32. Sequence analysis revealed that the cleavage site in DNA-PKcs during CTL killing was the same as that when this substrate was exposed to CPP32. This study demonstrates for the first time that the cleavage of DNA-PKcs in this intact cell system is exclusively due to an ICE-like protease.

Amino Acid Sequence↗
PubMed1996

DNA-dependent protein kinase catalytic subunit: a target for an ICE-like protease in apoptosis.

Radiosensitive cell lines derived from X-ray cross complementing group 5 (XRCC5), SCID mice and a human glioma cell line lack components of the DNA-dependent protein kinase, DNA-PK, suggesting that DNA-PK plays an important role in DNA double-strand break repair. Another enzyme implicated in DNA repair, poly(ADP-ribose) polymerase, is cleaved and inactivated during apoptosis, suggesting that some DNA repair proteins may be selectively targeted for destruction during apoptosis. Here we demonstrate that DNA-PKcs, the catalytic subunit of DNA-PK, is preferentially degraded after the exposure of different cell types to a variety of agents known to cause apoptosis. However, Ku, the DNA-binding component of the enzyme, remains intact. Degradation of DNA-PKcs was accompanied by loss of DNA-PK activity. One cell line resistant to etoposide-induced apoptosis failed to show degradation of DNA-PKcs. Protease inhibitor data implicated an ICE-like protease in the cleavage of DNA-PKcs, and it was subsequently shown that the cysteine protease CPP32, but not Mch2alpha, ICE or TX, cleaved purified DNA-PKcs into three fragments of comparable size with those observed in cells undergoing apoptosis. Cleavage sites in DNA-PKcs, determined by antibody mapping and microsequencing, were shown to be the same for CPP32 cleavage and for cleavage catalyzed by extracts from cells undergoing apoptosis. These observations suggest that DNA-PKcs is a critical target for proteolysis by an ICE-like protease during apoptosis.

Animals↗