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Biomedical subjects

C O Mok

Publications and source records attributed to C O Mok.

10 recordsLinked to original sources
PubMed2000

Nasopharyngectomy in the treatment of recurrent nasopharyngeal carcinoma: a twelve-year experience.

BACKGROUND: The incidence of recurrent nasopharyngeal carcinoma (NPC) after primary radiotherapy is considerable. The result of re-irradiation to the recurrent tumor is not satisfactory. METHODS: Thirty-one patients who received nasopharyngectomy for treatment of their recurrent nasopharyngeal carcinoma (NPC) (rT1 to rT3) at the Prince of Wales Hospital during the period 1986 to 1997 were reviewed retrospectively. Eleven patients had nasopharyngectomy performed by the transoropalatal approach, 9 patients by the maxillary swing approach, and 11 patients by the mandibular approach. RESULTS: Most recurrences (29 of 31) were rT1 and rT2 tumors. No hospital mortality occurred. The common complications of nasopharyngectomy were palatal defect (17 of 31), trismus (15 of 31), otitis media with effusion (20 of 31), dysphagia (12 of 31), and nasal regurgitation (8 of 31). Nine surgical specimens had microscopic invasion of the resection margins. The 5-year actuarial overall survival, actuarial disease-free survival, and tumor control were 47%, 42%, and 43%, respectively. The administration of postoperative radiotherapy significantly enhanced survival and tumor control after nasopharyngectomy. CONCLUSIONS: Nasopharyngectomy supplemented by postoperative radiotherapy achieved significant survival and tumor control with acceptable complications in selected recurrent NPC. It appears to be a better salvage treatment than re-irradiation alone for selected recurrent NPC.

Adenocarcinoma↗
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↗
PubMed1999

In vivo trial comparing patients' tolerance of Q-switched Alexandrite (QS Alex) and Q-switched neodymium:yttrium-aluminum-garnet (QS Nd:YAG) lasers in the treatment of nevus of Ota.

BACKGROUND AND OBJECTIVES: Different types of Q-switched lasers have been found to be effective in the treatment of nevus of Ota. However, a clinical trial involving in vivo comparison of the use of different laser systems has not been performed. The aim of the present study was to compare the patient tolerance of Q-switched Alexandrite (QS Alex) and Q-switched neodymium:yttrium-aluminum-garnet (QS Nd:YAG) lasers in the treatment of nevus of Ota. STUDY DESIGN/MATERIALS AND METHODS: Thirty-three patients (11 male, 22 female) were recruited for this study, and 45 treatment sessions were performed. Half of each lesion was treated with QS Alex and the other half with QS Nd:YAG laser. Patients were interviewed with a visual analog scale questionnaire immediately after treatment and 1 week later. Questions included the degree of pain, swelling, and bleeding. RESULTS: The immediate pain after treatment was more severe for QS Alex than for QS Nd:YAG laser. However, 1 week after laser therapy, most patients found QS Alex to be superior. CONCLUSION: Patients tolerate QS-Alex better than QS Nd:YAG. This finding is important because patients with nevus of Ota are often children, and multiple laser sessions are necessary for complete resolution of the lesion.

Activities of Daily Living↗
PubMed1999

MR imaging of thyroglossal duct cysts in adults.

AIM: To describe the magnetic resonance (MR) features of thyroglossal duct cysts (TDC) in adults. PATIENTS AND METHODS: Sixteen patients with TDC underwent MR imaging to obtain T1- and T2-weighted images and T2-weighted fat saturation images. In addition, contrast enhanced images were obtained in five patients. RESULTS: The signal intensity of TDC was of that of a simple cyst in seven (44%) patients, yielding high signal intensity on T2- and low signal intensity on T1-weighted images. In nine (56%), the signal intensity was either intermediate or high on T1-weighted images, the T2 signal intensity in these cases being high (7), intermediate (1) or low (1). Enhancement of the wall of the cyst was present in three of five (60%) patients. All 16 TDC were located at or just to one side of the midline and 12 were embedded in the strap muscles. All TDC were infrahyoid in location but 11 also extended superiorly to be directly related to the hyoid. At the hyoid the cystic component was immediately posterior (6) anterior (3) or anterior and posterior (2) to the bone. Intralaryngeal extension was present in eight (50%) patients. A suprahyoid tract was identified in three patients. The thyroid gland was in a normal location in all patients. CONCLUSION: Thyroglossal duct cysts are most commonly of high T1 signal intensity consistent with high protein content. The tract leading to the base of the tongue is infrequently seen, the diagnosis being determined by the intimate relationship to the hyoid and strap muscles. Intralaryngeal extension in adult patients with TDC is more frequent than reported previously.

Adult↗
PubMed1998

How successful is high-dose (> or = 60 Gy) reirradiation using mainly external beams in salvaging local failures of nasopharyngeal carcinoma?

PURPOSE: To evaluate the efficacy of high-dose (> or = 60 Gy) reirradiation using mainly external beams in salvaging local failures of nasopharyngeal carcinoma (NPC) after modern primary radical radiotherapy that delivered radical dose-to-target volumes defined by CT scan. METHODS AND MATERIALS: Nine hundred and three patients with nondisseminated NPC whose primary radical radiotherapy was administered between 1984 and 1989 inclusive were studied. One hundred and seventy-six had local failures comprising 9 persistences and 167 recurrences. In 10 patients the local failures were preceded or accompanied by (within 2 months) distant metastases, and these were given supportive treatment or palliative radiotherapy in low dose (< 60 Gy) if symptomatic. Most of the rest (123 of 166) were treated with either reirradiation to high dose (> or = 60 Gy) using mainly external photon beams (n = 103) or nasopharyngectomy with/without radical neck dissection with/without postoperative radiotherapy (n = 20). The remainder (n = 43) received only palliative treatments because of poor general condition and/or patients' refusal of radical treatments. The primary radiotherapy was planned on the basis of target volumes defined by CT scan and given to a standard nasopharyngeal dose of 62.5 Gy/29 fractions/6 weeks. In the presence of parapharyngeal involvement, an additional boost of 20 Gy/10 fractions/2 weeks was given via a posterior oblique photon beam. If local residual tumors were diagnosed at 4-6 weeks after the completion of external radiotherapy, an additional boost of 24 Gy/3 fractions/15 days was given by intracavitary intubation. For the local failures given high-dose reirradiation, the target volume was defined by CT scan and treated by a two-field or a three-field photon arrangement with or without additional dose supplement by intracavitary intubation. Nasopharyngectomy was performed via the transcervico-mandibulo-palatal approach or the maxillary swing approach. Radical neck dissection was only performed for the clinically evident nodal failures. RESULTS: With a median follow-up of 20 months (range 2.5-81 months) since the diagnosis of local failure, the actuarial 5-year overall survival, further relapse-free survival and free-from-local-tumor rates were 9.4, 11.5, and 18.7%, respectively, for the 123 patients treated by either high-dose reirradiation (n = 103) or nasopharyngectomy (n = 20). Palliatively treated patients (n = 43) had a survival comparable to patients whose local failures were preceded or accompanied by distant metastasis (n = 10). Reirradiation to high dose (> or = 60 Gy) mainly by external photon beams achieved a 5-year overall survival of 7.6% and 5-year local control of 15.2% with significant complications. Radiation-induced temporal lobe encephalopathy was radiologically evident in 21 patients (20.4%), and 13 of these 21 patients were symptomatic. It could have been the cause of death in three patients who also suffered from uncontrolled local tumor. Significant morbidity was also associated with the other frequent radiation complications, including xerostomia, trismus, and deafness. Uni- and multivariate analyses indicated that brief initial disease-free interval between completion of primary radiotherapy and diagnosis of local failures and advanced recurrent T-stage and recurrent N-stage were significant prognosticators predicting poor survival and/or further local failure after reirradiation. These patients were unlikely to benefit from the treatment. Nasopharyngectomy (+/- neck dissection +/- postoperative radiotherapy) was associated with earlier recurrent T-stages (mostly rT1 and rT2) and better survival and local control than reirradiation. However, restricting the comparison to rT1 and rT2 still demonstrated the superior results in favor of nasopharyngectomy, which could not be explained by the selection of less advanced lesions or patients with better performance status for surgery. (ABSTRACT TRUNCATED)

Adult↗
PubMed1997

Obturator hernia revisited: a review of 12 cases in 7 years.

Twelve patients with obturator hernia seen over a 7-year period were reviewed retrospectively. All were elderly females presenting with small bowel obstruction. The median body weight was 35 kg. A significant proportion of patients (33%) came from homes for elderly people and were either bed-ridden or wheel chair-bound. All 12 patients were classified as high-risk-patients in pre-operative assessment. Only one patient (8.8%) had a history of previous abdominal operation. Clinical signs such as Howship-Romberg sign and palpable groin mass were absent in these patients. Contrast radiography was performed in three patients and was not helpful in the diagnosis. A correct pre-operative diagnosis was suspected in only one case. The medium treatment delay was 1.5 days and the gut resection rate was 75%. The overall mortality rate was high (25%). A high index of clinical suspicion is important in the diagnosis and obturator hernia should be suspected whenever an elderly thin female with no previous abdominal surgery developed small bowel obstruction. Early laparotomy is recommended in such patients.

Aged↗
PubMed1996

Role of high frequency ultrasonography in the evaluation of palpable breast masses in Chinese women: alternative to mammography?

We prospectively assessed the accuracy of high resolution breast ultrasonography in the diagnosis of palpable breast masses in comparison to clinical palpation and x-ray mammography. Four hundred and eight Chinese women with palpable breast lumps had clinical assessment followed by ultrasonography of the breast, mammography (for women over 35 years), and fine needle aspiration cytology. Excisional biopsy or surgery was performed for suggestive lesions. The clinical, mammographic and ultrasound diagnoses were compared with the final pathologic diagnosis. In the determination of whether a lesion was malignant, the sensitivity, specificity, and positive predictive values were 97%, 97%, and 85%, respectively, for ultrasonography; 92%, 94%, and 84%, respectively, for mammography; and 88%, 92%, and 67%, respectively, for clinical evaluation. The specificity for combined clinical palpation and ultrasonography was higher (99%) than that for combined clinical palpation and mammography (96%). Addition of ultrasonography to combined clinical palpation and mammography increased specificity. Mammography in addition to combined clinical palpation and ultrasonography did not significantly improve the sensitivity, specificity, or positive predictive value. This limited usefulness raises the question as to whether it should be eliminated in the workup of a palpable mass in the average Chinese patient. Its main advantage is the detection of extended foci of carcinoma in situ related to a palpable mass, which often is undetected by ultrasonography.

Adult↗
PubMed1995

Ultrasound of Kimura's disease.

Kimura's disease is found almost exclusively in Orientals. It commonly affects the head and neck region and mainly involves the major salivary glands and regional lymph nodes. Its appearances can be mistaken for malignant disease. We present two patients with Kimura's disease. In one patient the disease involved the soft tissues and parotid gland, and in another the submandibular gland. Both patients demonstrated lymphadenopathy in the submandibular, submental areas and upper cervical region. Both patients had ultrasound examination of the salivary glands and neck. One of the patients also had contrast-enhanced CT and MRI. The clinical, pathological and imaging findings of Kimura's disease are discussed.

Aged↗