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Biomedical subjects

E H Tan

Publications and source records attributed to E H Tan.

At least 37 records · Page 2Linked to original sources
PubMed1997

Squamous cell head and neck cancer in nonsmokers.

Tobacco and alcohol abuse are the major known risk factors for the development of squamous cell head and neck cancer (SCHNC). Information about this disease in nonsmokers, however, is limited. We retrospectively studied a group of 59 tobacco nonusers with SCHNC, diagnosed since 1986 at the Cleveland Clinic Foundation (CCF). Two objectives were defined: (a) to characterize this nonsmoking population of patients and identify any significant differences compared with a control population consisting of all patients diagnosed with SCHNC at the CCF between 1986 and 1993 and (b) to determine the prevalence of exposure to environmental tobacco smoke in this nonsmoking group of patients with SCHNC and compare it with the environmental tobacco-smoke exposure in a second, control population of non-SCHNC, nonsmoking patients matched for age, race, sex, and alcohol use. The group of nonsmoking patients with SCHNC was notable for only rare alcohol abuse, a preponderance of whites, and relatively fewer laryngeal primary tumors. There were significantly more women and more tongue primaries. When compared with the control population without cancer, the nonsmoking patients had a significantly higher risk of exposure to environmental tobacco smoke both in the home and in the workplace. We conclude that the tobacco nonuser who develops SCHNC is likely to be female and white and to have a primary tongue cancer. A significant association with environmental tobacco smoke exposure is suggested by our data.

Age Factors↗
PubMed1997

Concurrent chemoradiotherapy for salvage in relapsed squamous cell head and neck cancer.

The results in 9 patients with unresectable recurrent squamous cell cancer of the head and neck who were treated with aggressive concurrent chemoradiotherapy are reported. Treatment consisted of one or two courses of chemotherapy with 5-fluorouracil 1000 mg/m2/day and cisplatin 20 mg/m2/day, both given as 4-day continuous intravenous infusions, concurrent with radiation therapy. Salvage radiation doses between 30 and 70 Gy were administered. Seven patients had previously undergone an attempt at curative surgery, and 7 had been treated with radiation doses between 52 and 72 Gy. The recurrent disease was locally confined in 3, locoregional in 5, and locoregional with metastases in 1 of the 9 patients. Treatment toxicity was significant and included mucositis, nausea/vomiting, and granulocytopenia, but there were no toxic deaths. Complete tumor clearance was possible in 6 of these 9 patients, and 5 patients remain disease-free at 41+, 43+, 45+, 47+, and 50+ months. Of these 5 patients, 4 had previously been treated with both surgery and radiation, while 1 had only undergone surgery. We conclude that aggressive chemotherapy and concurrent (re)irradiation can be given to patients with unresectable, recurrent, squamous cell cancer of the head and neck. Treatment is tolerable, and disease-free long-term survival is possible. Careful patient selection, however, is required.

Adult↗
PubMed1997

Burkholderia pseudomallei infection in the Singapore Armed Forces from 1987 to 1994--an epidemiological review.

Between 1987 and 1994, twenty-three cases of Burkholderia pseudomallei infection (melioidosis) were diagnosed in persons serving in the Singapore Armed Forces. There were four deaths resulting from complications of the infection. Unlike the situation in the general population, where the affected are mainly the elderly with underlying illness, the majority of cases in the Singapore Armed Forces were otherwise fit and healthy young servicemen. Serological surveys have shown the prevalence of the infection in Singapore to be 0.2% in the military as well as civilian population. As physical contact with soil is an unavoidable part of military training, military personnel continue to be at risk of exposure to this soil-related disease.

Adolescent↗
PubMed1996

Correlation between surfactant/micelle structure and the stability of bacteriorhodopsin in solution.

The rate of solubilization and isothermal bleaching of bacteriorhodopsin (bR) in a series of nine alkylammonium surfactants is studied by using time-resolved optical spectroscopy. The surfactant series RN(+)R'(3) covers a range in tail length (R = C(12)H(25), C(14)H(29), or C(16)H(33)) and headgroup size and hydrophobicity (R' = CH(3); C(2)H(5), or C(3)H(7)). The rate of bleaching increases initially with increasing surfactant concentration but decreases at higher concentrations. Possible explanations for this behavior are discussed. The kinetic data are consistent with the penetration of the surfactant into the protein interior. Interaction of the surfactants with the protein is a complicated, multistep process, and the rate curves are a function of at least four variables: 1) the micellar environment, 2) the length of the surfactant tail, 3) the size of the headgroup, and 4) the hydrophobicity of the headgroup. Our data provide new insights into the molecular characteristics that help define the performance of surfactants in the solubilization and denaturation of membrane-bound proteins.

Bacteriorhodopsins↗
PubMed1996

A phase II trial of etoposide, leucovorin and 5-fluorouracil (ELF) in patients with advanced gastric cancer.

Etoposide, leucovorin and 5-fluorouracil (ELF) chemotherapy has been reported to be less toxic yet effective (response rates of 50%) in patients with advanced gastric cancer. A phase II study of ELF in 25 patients (11 males, 14 females, median age 53 years) with advanced adenocarcinoma of the stomach is reported. Patients received outpatient intravenous etoposide 120mg/m2 over 2 hours, folinic acid 300 mg/m2 over 2 hours, 5-fluorouracil 500 mg/m2 boluses daily for 3 days every 21 days. Of 17 measurable patients, there was one complete response (CR), 4 partial responses (PR) for a total response rate of 29.4%. Non-hematologic toxicity was modest (grade 0 vomiting 11/21, stomatitis 16/21, diarrhea 17/21). Grade 3/4 neutropenia was seen in 14/23, thrombocytopenia in 2/23, anemia in 5/23 patients. Median progression-free and overall survival was 4.1 and 7.1 months, respectively. In conclusion, ELF chemotherapy shows only modest activity in patients with advanced gastric cancer and is associated with severe hematologic toxicity.

Adult↗
PubMed1996

Chemotherapy in non-small cell lung cancer: a review.

Lung cancer, of which non-small cell carcinoma is the most common, has been a significant therapeutic challenge for decades and will remain so for decades to come. Despite its prevalence, progress in the management of non-small cell lung cancer has been relatively slow. This is in part due to the pessimism of most physicians treating this disease, which has resulted in a relatively lackadaisical attitude with regards to clinical trials when compared to other solid tumours like breast or colorectal cancers. Nevertheless, the past decade has seen significant progress, specifically with regards to the management of locally advanced disease. Chemotherapy, though shown to be biologically active in non-small cell lung cancer, is considered an ineffective palliative tool in the setting of metastatic disease due to its toxicities and the "less than encouraging" response rates generated by the cisplatin-based combination regimen which is generally considered to be the most active currently available. The advent of new active agents such as paclitaxel and vinorelbine which are potentially less toxic may change this view. Conversely, the response rate of locally advanced disease to chemotherapy is significantly higher and this has resulted in numerous multimodality trials of neoadjuvant chemotherapy prior to surgery and/or radiation. To date, a number of randomised trials have shown that this approach can result in significant survival benefit for patients with locally advanced disease. An alternative approach makes use of the potential synergism between certain chemotherapeutic agents (such as cisplatin) and radiation when used concurrently. However, data on concurrent chemoradiotherapy in locally advanced disease have been largely based on single-arm studies and are inconclusive. Three randomised trials on concurrent chemoradiotherapy have been shown benefit for the use of combined modality in locally advanced disease. Hence, treatment of locally advanced disease should include chemotherapy as part of the combined modality approach. However, the optimal sequencing of these modalities would require well-designed randomised trials to determine.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1996

5-Fluorouracil continuous infusion in metastatic colorectal cancer.

5-Fluorouracil (5-FU) remains the most active therapeutic agent in advanced colorectal cancer. This drug has demonstrated differing levels of activity dependent on the schedule of administration in experimental and clinical models. Twenty-six patients were treated with prolonged continuous infusion of 5-FU at 250 mg/m2/day via a portable infusion pump and Hickman's central venous catheter in this study. Twelve patients (46%) experienced a major response (complete response-1, partial response-11). Median duration of response was 5 months. Seventeen patients were chemotherapy-naive on accrual to this study. Ten patients from this group had partial responses (59%) and four were minor responders (24%). Hence 82% of patients who had no prior chemotherapy showed tumour responses to 5-FU continuous infusion. Two of nine patients (22%) with prior chemotherapy achieved major response. Favourable toxicity profile was noted with this regimen. Two patients discontinued therapy due to treatment-related toxicities (severe palmar-plantar erythrodysesthesia and superior vena cava thrombosis secondary to the central venous catheter). Prolonged continuous infusion of 5-FU could well be the standard treatment of advanced colorectal cancer in view of its favourable activity and toxicity profile. The serial serum carcino-embryonic antigen (CEA) trend was shown to correlate well to the objective response; a decline of more than 50% from baseline CEA level correlated with a major response and a rise of more than 50% correlated with progressive disease. Hence the use of serum CEA is suitable for monitoring response to chemotherapy which is advantageous with respect to patient convenience and cost-effectiveness.

Adenocarcinoma↗
PubMed1996

Combination chemotherapy (dacarbazine, carmustine, cisplastin, and tamoxifen) in advanced melanoma.

Melanoma is rare in Singapore with an age-standardised rate (ASR) of 0.4-0.8 per 100,000 per year. Thirteen patients with metastatic or locally advanced melanoma were referred to the Department of Medical Oncology, Singapore General Hospital between Feb 1991 and Nov 1993. Ten patients were given combination chemotherapy comprising carmustine (BCNU), cisplatin, dacarbazine (DTIC) and tamoxifen. The remaining 3 patients either rejected chemotherapy or were too ill to receive chemotherapy. Patient characteristics were as follows: there were 6 males and 4 females; age range 29-75 years; all were Chinese; sites of primary disease: extremities 8, retroorbital 1, vagina 1; sites of metastases: lymph nodes 6, skin 2, pulmonary 3, liver 1. All received the same combination chemotherapy comprising iv BCNU 150 mg/m2 q8wk, iv DTIC 220 mg/m2 x 3 days q4 wk, iv cisplatin 25 mg/m2 x 3 days q4 wk and tab tamoxifen 40 mg daily. There were 6 partial responses and no complete responses, giving a response rate of 60% with a median survival of 11.5 months. Three patients with sites of disease in the vagina, retroorbital region and metastatic liver disease had progressive disease despite chemotherapy and one died of treatment related sepsis. The 6 responders include those with metastases to the skin, nodes and/or lung. Treatment was generally tolerable. Two patients experienced delays of their subsequent cycles of treatment by 1-2 weeks due either to neutropenia and/or thrombocytopenia. This regimen is a fairly active combination against metastatic melanoma, particularly those with metastases to the nodes, skin and the lung. Those with involvement of other sites tend to respond poorly.

Adult↗
PubMed1995

Oral acyclovir in the treatment of adult varicella.

An open study was conducted to evaluate the efficacy of oral acyclovir in a group of 295 Singapore Armed Forces male servicemen. The 148 patients who were willing to take acyclovir were given 800 mg orally five times per day for seven days. The other 147 who refused to take acyclovir were monitored as a control group. Each of these groups was further classified into two groups. Group A patients presented with rash within 24 hours of rash onset and Group B presented between 24 and 72 hours. Daily lesion counts, temperature, pruritus scores and laboratory tests were used to monitor disease progression. Early acyclovir intervention (Group A) reduced the time to 100% crusting from 7.19 to 5.71 days (P = 0.0001), decreased the maximum number of all lesions by 26% (P = 0.03) and the maximum number of vesicular lesions by 45% (P = 0.0004). Late therapy (Group B) was effective in reducing the maximum number of vesicular lesions by 38% (P = 0.003). The number of patients requiring antibiotics for suspected secondary skin infection, the duration of fever and paracetamol consumption were significantly reduced in both the early and late intervention groups. However, there were no effects in minimizing pruritus in either group. Serious complications such as pneumonia, encephalitis or death were not observed in this study. The most common adverse effect of acyclovir was mild diarrhoea occurring in 35% of patients treated with the drug. We conclude that early treatment with acyclovir was beneficial whereas late therapy had limited effect in reducing the severity of cutaneous lesions in patients with varicella.

Acyclovir↗
PubMed1995

Prevalence of G6PD deficiency among recruits in the Singapore Armed Forces.

Between 1986 and 1990, 107,397 National Servicemen between the ages of 17 to 18 years were screened on enlistment for Glucose-6-Phosphate Dehydrogenase (G6PD) enzyme activity by fluorescent spot test. The overall prevalence rate was 1.6% with ethnic differences as follows: 1.62% for Chinese, 1.80% for Malay, 0.76% for Indian and 0.68% for other races. The majority had no prior knowledge of their G6PD deficiency status (89.9%), or of any significant haemolytic episode (93.3%). The rest gave a history of neonatal jaundice, non-neonatal jaundice, anaemia and haemoglobinuria. Maloprim, fava beans, sulphur drugs and aspirin were cited as triggering factors.

Adolescent↗
PubMed1995

Resolution of superior vena cava obstruction in small cell lung cancer patients treated with chemotherapy.

Small cell lung cancer is a highly chemo-sensitive malignancy. As it often presents with a central lesion, superior vena cava obstruction (SVCO) is not an uncommon manifestation. From January 1990 to December 1993, 161 patients with small cell lung carcinoma were seen at our institution. Twenty (12.4%) of these patients presented with symptoms and signs of SVCO. Initial therapy consisted of radiotherapy in 4 patients and chemotherapy in 16 patients. Of those treated with chemotherapy, patient characteristics included 13 males, median age of 62.5 years (range 51 to 78 years), Eastern Co-operative Oncology Group (ECOG) performance status of 3 to 4 in 7 patients; 1 to 2 in 9 patients, and limited stage disease in 8 patients. The median period of follow-up was 5 months. Nine patients received a combination of cisplatin and etoposide (EP), 5 had cyclophosphamide, doxorubicin and vincristine, 1 had cyclophosphamide, etoposide and vincristine and 1 had monotherapy with oral etoposide. Overall response to chemotherapy was 81% (with 31% complete responses). All responders had resolution of SVCO. Only 3 patients did not respond (1 patient defaulted, 1 patient died of neutropenic sepsis at week one and 1 patient had stable disease). Resolution of SVCO was noted within the first 2 weeks after the first cycle; the earliest being 3 days. The only patient given single-agent oral etoposide responded within 10 days after initiation of treatment. Of the 7 patients with poor performance status (ECOG 3 to 4), 3 died from treatment-related complications. Chemotherapy is highly effective as a primary treatment of small cell lung carcinoma despite presentation with SVCO. However, caution is advised in the use of combination chemotherapy for those presenting with poor performance status. Initial therapy with oral etoposide or radiotherapy should be considered as possible alternatives for these patients.

Aged↗
PubMed1994

In vivo evaluation of anterior cervical fusions with hydroxylapatite graft material.

STUDY DESIGN: The efficacy of solid hydroxylapatite (HA) blocks for obtaining cervical interbody fusion was studied in a canine model. Each of 21 adult colony-reared hounds received a hydroxylapatite implant and an autogenous bone graft in the C3-C4 and C5-C6 disc interspaces. Seven dogs each were killed at 6, 12, and 26 weeks postoperation. OBJECTIVE: This study determined the rate, mechanical strength, and histologic characteristics of cervical interbody fusions achieved using a hydroxylapatite (HA) block and compared the results to those obtained with autogenous iliac crest bone graft. SUMMARY OF BACKGROUND DATA: The use of corticocancellous autograft has been successful in a high percentage of anterior cervical interbody fusions. Calcium phosphate ceramics may provide an alternative to autogenous and allogenous tissue. These materials are biocompatible and capable of direct intimate bonding with bone because of their chemical similarity to bone mineral. METHODS: Radiographic evaluation including plain radiographs, computed tomography (CT), and magnetic resonance imaging (MRI) studies were used to determine fusion quality. Specimens were also subjected to mechanical testing to determine bending and torsional stiffness as well as ultimate load to failure. Histologic evaluation included integrity and incorporation of the graft materials and interface characterization. RESULTS: The CT images were well correlated with plain radiographs and demonstrated progressive incorporation of the graft materials with time. Magnetic resonance images were of little value in evaluating quality of fusion; the autograft sites demonstrated progressive disc height loss with time. Minimal disc height loss was observed with HA blocks. There was no statistical difference in torsional stiffness for the HA blocks and autogenous bone grafts at any time period. In bending, the HA block sites were significantly stiffer at 6 weeks (P < 0.005). There was no statistical difference in the ultimate failure load for the HA and autogenous bone grafts. Histologically, the HA blocks demonstrated areas of direct bone apposition with increased bone appositions and implant incorporation with time. At 6 and 12 weeks postoperation, the autograft sites demonstrated areas of graft resorption and some new bone formations. By 26 weeks, new bone was continuous with the vertebral endplates. CONCLUSIONS: The results indicate that HA blocks may provide an alternative to autogenous graft materials for anterior cervical interbody fusion. Block slippage and/or fracture may occur in a small number of patients but is primarily related to insertion technique and does not appear to significantly alter the final result.

Animals↗
PubMed1994

In vivo evaluation of recombinant human osteogenic protein (rhOP-1) implants as a bone graft substitute for spinal fusions.

STUDY DESIGN: Posterior spinal fusion segments were evaluated in adult mongrel dogs at 6, 12, and 26 weeks post-implantation. Four sites on each animal received implants consisting of recombinant human osteogenic protein-1 on a bone collagen carrier, bone collagen carrier alone, autogenous iliac crest bone, or no implant material. OBJECTIVE: To determine the efficacy of recombinant human osteogenic protein-1 as a bone graft substitute in achieving posterior spinal fusion and compare the results to those obtained using autogenous bone graft. SUMMARY OF BACKGROUND DATA: Posterior spinal fusion generally includes onlay grafting of autogenous or allogeneic bone after decortication of bony surfaces of the vertebral elements. The search for an acceptable bone graft substitute material has in recent years centered upon proteins capable of inducing bone in vivo. Recombinant human osteogenic protein-1 has demonstrated efficacy in healing large segmental osteoperiosteal defects in rabbits, dogs, and monkeys and appears ideally suited as a bone graft substitute for spinal fusions. METHODS: The quality of fusion and new bone formation was evaluated using plain films, computed tomography, and magnetic resonance imaging. RESULTS: Radiographic and histologic studies demonstrated that recombinant human osteogenic protein-1-treated fusion segments attained a stable fusion by 6 weeks post-implantation and were completely fused by 12 weeks. The autograft sites demonstrated fusion at 26 weeks post-implantation. CONCLUSIONS: The results indicated that recombinant human osteogenic protein-1 is an effective bone graft substitute for achieving stable posterior spinal fusions in a significantly more rapid fashion than can be achieved with autogenous bone graft.

Animals↗
PubMed1994

Control of emesis by intravenous granisetron in breast cancer patients treated with 5-FU, epirubicin and cyclophosphamide.

Granisetron, a potent and selective 5-hydroxytryptamine receptor (5-HT3) antagonist was reported to be an effective antiemetic agent both in animal studies and in patients given highly emetogenic chemotherapy. A sample of 43 patients with breast cancer was accrued from September to November 1992 in a phase II study to assess the efficacy of granisetron in patients receiving FEC (5-FU, epirubicin, cyclophosphamide). Each patient received 3 mg intravenous granisetron as a single dose just prior to chemotherapy. Oral metoclopromide was prescribed to each patient as a rescue anti-emetic. The emetic episodes and degree of nausea were evaluated on a daily basis. Good control of emesis (0-2 episodes of vomiting) and nausea (mild or no nausea) was in the range 77%-98% and 77%-93% respectively. There was a complete response (no emetic episodes throughout the 6-day period) in 16 patients (37.2%). Onset of emesis tends to occur on day 1 and tend to subside after day 3; 85% of patients had onset of emesis in the first 2 days after chemotherapy. Control of emesis and nausea tends to improve after day 3, which could be the result of the reduced emetogenicity of the combination FEC with time. Altogether, 77% had good control of acute emesis; control of delayed emesis was better with 84% achieving a major response on day 2 after chemotherapy, which improved to more than 90% after day 4. Granisetron was generally tolerated with headache being the most common side-effect followed by constipation and flushing. This study suggests that granisetron is an effective and well-tolerated anti-emetic agent, which deserves randomised trials to elucidate its efficacy further.

Administration, Oral↗
PubMed1994

The effect of a 5-month supervised program of physical activity on anthropometric indices, fat-free mass, and resting energy expenditure in obese male military recruits.

Studies using mainly dietary restriction have shown that weight loss is associated with a decrease in fat-free mass (FFM) and resting energy expenditure (REE). The aim of this study was to investigate the effects of a weight-loss program relying solely on increased physical activity on FFM and REE. Forty-two overweight male military recruits (12 with initial body mass index [BMI] between 25.0 and 29.9 kg/m2, group 1; 14 with BMI between 30.0 and 34.9 kg/m2, group 2; and 16 with BMI of at least 35 kg/m2, group 3) completed a 5-month program of supervised physical activity that included both aerobic and muscle-strengthening components. All subjects lost significant amounts of weight (group 1, 8.6 kg; group 2, 15.7 kg; group 3, 22.0 kg). This weight loss was accompanied by a significant reduction in the waist to hip ratio (WHR) in all groups. FFM was maintained in all groups. REE tended to decline in all groups (group 1, from 1,595.0 +/- 46.9 to 1,511.7 +/- 53.2 kcal/d; group 2, from 1,751.4 +/- 56.0 to 1,680.0 +/- 63.1 kcal/d; group 3, from 1,901.9 +/- 93.7 to 1,740.0 +/- 67.3 kcal/d), but this decline reached statistical significance only when all 42 subjects were considered. REE normalized for FFM did not decrease except in group 1. Furthermore, differences between the slopes and intercepts of the regression lines relating REE with FFM before and at completion of the 5-month program were not statistically significant, suggesting that the relationship between REE and FFM was maintained after weight loss.(ABSTRACT TRUNCATED AT 250 WORDS)

Anthropometry↗
PubMed1994

Melanoma metastatic to the bronchus: radiologic features in two patients.

Two patients with cutaneous melanoma metastatic to the bronchus are described. Chest radiographs revealed only indirect signs of bronchial obstruction. Computed tomography (CT) clearly demonstrated the intraluminal lesion. Magnetic resonance (MR) imaging signal characteristics were not specific for melanoma.

Aged↗
PubMed1991

Prevention of heat disorders in the Singapore Armed Forces--1984-1989.

A review of the incidence of heat disorders in the Singapore Armed Forces was done in relation to the preventive and corrective measures applied. Data was compiled and analysed from records kept by the SAF Medical Services. A thorough review was made into all the preventive measures carried out thus far and the effectiveness was evaluated. There was a rise in the incidence of heat strokes from eight cases in 1984 to a peak of 46 cases in 1986. Subsequently, aggressive measures were adopted and the incidence fell significantly in 1988 and 1989. The main strategy involved a comprehensive health education programme, regulations, active surveillance and aggressive treatment. However, the incidence has not fallen to the pre-1984 levels. Therefore, a strict vigilance must be constantly maintained to prevent further mortality and morbidity.

Heat Exhaustion↗