Biomedical subjects

Stephen Yau

Publications and source records attributed to Stephen Yau.

7 recordsLinked to original sources

PubMed2006

Clustering DNA sequences by feature vectors.

We represent all DNA sequences as points in twelve-dimensional space in such a way that homologous DNA sequences are clustered together, from which a new genomic space is created for global DNA sequences comparison of millions of genes simultaneously. More specifically, basing on the contents of four nucleotides, their distances from the origin and their distribution along the sequences, a twelve-dimensional vector is given to any DNA sequence. The applicability of this analysis on global comparison of gene structures was tested on myoglobin, beta-globin, histone-4, lysozyme, and rhodopsin families. Members from each family exhibit smaller vector distances relative to the distances of members from different families. The vector distance also distinguishes random sequences generated based on same bases composition. Sequence comparisons showed consistency with the BLAST method. Once the new gene is discovered, we can compute the location of this new gene in our genomic space. It is natural to predict that the properties of this new gene are similar to the properties of known genes that are locating near by. Biologists can do various experiments to test these properties.

DNA↗

PubMed2006

Local and regional control in patients with papillary thyroid carcinoma: specific indications of external radiotherapy and radioactive iodine according to T and N categories in AJCC 6th edition.

To identify indications for external radiotherapy (EXT) and radioactive iodine (RAI) in papillary thyroid carcinoma (PTC), we conducted a retrospective study of local and regional control in 1297 patients diagnosed with PTC in a tertiary referral center. Managed by surgery alone, patients with bilateral thyroidectomy had a lower rate of local relapse compared with lobectomy (P=0.02). EXT improved locoregional (LR) failure-free survival (FFS) (P<0.001) and survival (P=0.01) in patients with gross postoperative LR residual disease. EXT also improved local FFS in patients with pathologically confirmed positive resection margins (P<0.001) and reduced local failures in patients with T4 disease (P=0.002). In patients with lymph nodes (LN) metastasis, more extensive surgery by functional or radical neck dissection resulted in less LN relapse compared with excision alone (P<0.001). EXT improved 10-year LN FFS in patients with N1b disease (P=0.005) and patients with LN metastasis of size>2 cm (P=0.02). RAI was effective in improving local control in patients with T2 to T4 diseases and LN control in patients with N0, N1a, and N1b categories. Local or LN relapses were associated with worse survival (P<0.001 and P<0.0001). The survival of patients with PTC could be improved by reducing local or LN relapses. RAI is indicated in patients with T2 to T4 disease. EXT is indicated in patients with gross postoperative disease, positive resection margins or T4 disease, N1b, or a LN size of >2 cm. LN relapse can be reduced by RAI in N0, N1a, and N1b disease.

Adolescent↗

PubMed2005

Overall survival after concurrent cisplatin-radiotherapy compared with radiotherapy alone in locoregionally advanced nasopharyngeal carcinoma.

This phase III randomized study compared concurrent cisplatin-radiotherapy (CRT) versus radiotherapy (RT) alone in patients with locoregionally advanced nasopharyngeal carcinoma. A total of 350 patients were randomly assigned to receive external RT alone or concurrently with cisplatin at a dosage of 40 mg/m(2) weekly. The primary endpoint was overall survival, and the median follow-up was 5.5 years. The 5-year overall survival was 58.6% (95% confidence interval [CI] = 50.9% to 66.2%) for the RT arm and 70.3% (95% CI = 63.4% to 77.3%) for the CRT arm. In Cox regression analysis adjusted for T stage, age, and overall stage, the difference in overall survival was statistically significantly in favor of concurrent CRT (P = .049, hazard ratio [HR] = 0.71 [95% CI = 0.5 to 1.0]). Subgroup analysis demonstrated that there was no difference between overall survival in the arms for T1/T2 stage (P = .74, HR = 0.93 [95% CI = 0.59 to 1.4]), whereas there was a difference between the arms for T3/T4 stage (P = .013, HR = 0.51 [95% CI = 0.3 to 0.88]), favoring the CRT arm. The regimen of weekly concurrent CRT is a promising standard treatment strategy for locoregionally advanced nasopharyngeal carcinoma patients.

Adult↗

PubMed2004

Pregnancy outcome after diagnosis of differentiated thyroid carcinoma: no deleterious effect after radioactive iodine treatment.

PURPOSE: Thyroid carcinoma is the second most common malignancy in young women, after breast cancer, aged 15-34 years in Hong Kong. Radioiodine or (131)I (RAI) has been confirmed as a useful treatment in the management of differentiated thyroid carcinoma (DTC). Serious concerns have been raised of the potential risks on subsequent pregnancies. METHODS AND MATERIALS: We conducted a single-institute, retrospective analysis of the gestational history of 104 patients who became pregnant after the diagnosis of DTC. The patients were interviewed for pregnancy outcome, and the data were supplemented by a review of the medical records in the Department of Clinical Oncology, Queen Elizabeth Hospital, Hong Kong. RESULTS: Of 263 pregnancies observed, the prior RAI administration in 153 (scanning dose or ablative dose) did not adversely affect the pregnancy outcome as determined by the rate of successful delivery, mode of delivery, live birth demographics (e.g., birth weight, gender distribution). In all live births, neither congenital malformations nor first year neonatal mortality was observed. Of 116 pregnancies in 68 patients who received an ablative dose (mean, 96.6 mCi) of RAI, 78 live births were reported. The updated information on these children at age 1 month to 30.8 years (mean, 7.9 years; SD 7.3) showed that they had no abnormal development. The incidence of miscarriages was not different in those with prior RAI administration. However, the incidence of preterm delivery was greater in those with a history of RAI (p = 0.03). A higher ablative dose (>80 mCi) and shorter interval between RAI and conception (<1 year) did not significantly alter the pregnancy outcome. Two patients were inadvertently given an RAI scanning dose during pregnancy. One decided to continue the pregnancy; a healthy 6-year-old boy was reported at the last update. Fifteen patients had DTC diagnosed during pregnancy; 2 terminated the pregnancy and 13 decided to continue their pregnancy. All children were born in good health. For DTC diagnosed during the first trimester of pregnancy, the deferral of thyroid surgery to the second trimester is a good compromise for earlier treatment of the malignancy while continuing the pregnancy. CONCLUSION: Radioiodine in young women with DTC did not have deleterious effects on subsequent pregnancies. Proper education and instruction for avoiding conception within 1 year after RAI is a prudent recommendation, allowing for RAI clearance and hormonal stabilization.

Adult↗

PubMed2004

Differentiated thyroid carcinoma in childhood and adolescence-clinical course and role of radioiodine.

BACKGROUND: Differentiated thyroid carcinoma (DTC) in childhood has a good prognosis despite a high incidence of relapse. The use of radioactive iodine (RAI) has not been well established. PROCEDURE: This is a review of 60 patients less than 21 years of age; mean follow-up was 14 years. RESULTS: Patients had a higher relapse rate with papillary thyroid carcinoma (PTC) than with follicular thyroid carcinoma (FTC): 24.5 vs. 9.1%. Compared with 997 patients with age > or = 21, patients <21 years of age had a higher female to male ratio (7.6 vs. 3.9), higher incidence of nodal metastasis (45 vs. 28%), and lung metastasis (15 vs. 7.8%), and improved 10-year cause-specific survival (CSS) (98.3 vs. 89.5%). The 10-year rates of CSS, local-regional failure-free survival (LRFFS), and distant metastasis failure-free survival (DMFFS) for the young patients were 98.3, 79.3, and 90.7%, respectively. In patients with no distant metastasis at presentation, RAI improved 10-year LRFFS (71.9 vs. 86.5%; P = 0.04). At last follow-up, 10 of 12 patients (80%) with local-regional (LR) relapse and five of nine patients (55.6%) with distant metastasis were rendered disease-free. No patient has experienced a second malignancy. CONCLUSIONS: Prognosis of DTC in young patients was good. Patients with LR relapse and distant metastasis had a high rate of remission after treatment. RAI treatment can reduce the rate of LR relapse in patients with no distant metastasis and result in complete remission in half of those with distant metastasis. No patient experienced a second malignancy.

Adenocarcinoma, Follicular↗

PubMed2003

Papillary microcarcinoma of the thyroid-Prognostic significance of lymph node metastasis and multifocality.

BACKGROUND: It is known that patients with papillary microcarcinoma (PMC) of the thyroid gland have a very favorable prognosis. The rising incidence of PMC among papillary thyroid carcinoma (PTC) necessitates the identification of prognostic factors and the formulation of treatment protocols. METHODS: The authors conducted a retrospective analysis of 203 patients with PMC who were diagnosed on or before 1999 and were treated at the Department of Clinical Oncology, Queen Elizabeth Hospital, Hong Kong. RESULTS: The cause specific survival, locoregional (LR) failure free survival, and distant metastases failure free survival rates at 10 years were 100%, 92.1%, and 97.1%, respectively. Five patients had lung metastases; 2 patients died of their metastases 12.9 years and 14.8 years after diagnosis, and 3 patients achieved clinical remission after radioiodine (RAI) treatment. Twelve patients had LR recurrences. Patients with LR recurrence were highly salvageable with a combination of surgery, RAI treatment, and external radiotherapy; all but one (who refused treatment) were alive without disease at last follow-up. Multivariate analyses did not reveal any independent prognostic factor for survival. The risk of cervical lymph node (LN) recurrence increased 6.2-fold (P = 0.01) and 5.6-fold (P = 0.02) when LN metastases and multifocal disease were present at diagnosis. RAI ablation reduced the LN recurrence rate to 0.27 (P = 0.04). The presence of LN metastasis increased the rate of distant metastasis 11.2-fold (P = 0.03). Age was not a significant factor in predicting disease recurrence or survival. Subdivision by tumor sizes </= 5 mm and > 5 mm did not affect the outcome, but no patient with tumors <or= 5 mm had mortality related to PMC. CONCLUSIONS: Despite the overall excellent prognosis for patients with PMC, PMC was associated with a 1.0% disease-related mortality rate, a 5.0% LN recurrence rate, and a 2.5% distant metastasis rate. Therefore, the treatment of patients with PMC should be no different from the treatment of patients with conventional PTC: i.e., complete surgery with consideration for RAI and/or external radiation therapy if poor prognostic factors are present.

Adolescent↗

PubMed2002

Follicular thyroid carcinoma: prognostic factors and the role of radioiodine.

BACKGROUND: The objective of this study was to investigate the patterns of recurrence, various prognostic factors, and the role of radioiodine in the treatment of patients with follicular thyroid carcinoma (FTC). METHODS: The clinical outcomes of 215 patients with FTC who were treated at a single institution were analyzed retrospectively. The mean follow-up was 10.8 years. RESULTS: The actuarial rates of cause specific survival (CSS), locoregional (LR) control, and freedom from distant metastasis (DM) at 10 years were 81%, 83%, and 72.3%, respectively. The independent prognostic factors for survival were metastasis at presentation (relative risk [RR], 47.7), radioiodine (RAI) treatment (RR, 0.25), extrathyroidal extension (RR, 3.8), and the postoperative absence of macroscopic disease in the neck region (RR, 0.06). In patients who were treated with RAI, both the LR failure rate (RR, 0.24) and the mortality rate (RR, 0.25) were reduced to about 25%. Subgroup analysis revealed that RAI improved the survival of patients with DM at presentation (RR, 0.17) and improved the LR control rate in patients who had no DM at presentation (RR, 0.13). For patients who underwent total thyroidectomy with negative resection margins, RAI significantly reduced the rate of LR recurrence (RR, 0.05). Patients with the minimally invasive type of FTC had a good prognosis. The 10-year rates for CSS, LR control, and freedom from DM were 97.6%, 100%, and 90.6%, respectively. The prognosis of patients with frankly invasive FTC was much poorer. The 10-year rates for CSS, LR control, and freedom from DM were 66.7%, 100%, and 45%, respectively. CONCLUSIONS: RAI is an effective treatment for patients with FTC. It was associated with improved survival rates and fewer recurrences.

Adenocarcinoma, Follicular↗