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David Y Chan

Publications and source records attributed to David Y Chan.

16 recordsLinked to original sources
PubMed2006

High concordance of gene methylation in post-digital rectal examination and post-biopsy urine samples for prostate cancer detection.

PURPOSE: We evaluated the concordance between post-digital rectal examination and post-prostate biopsy urine samples using conventional methylation specific polymerase chain reaction analysis of 3 gene promoters in patients with suspected or confirmed prostate cancer. MATERIALS AND METHODS: Voided urine specimens were collected from 17 men after 15-second digital rectal examination and again after transrectal ultrasound guided biopsy of the prostate for suspected malignancy or for followup biopsy as part of an expectant management protocol. Urine sediment DNA was isolated and subjected to bisulfite modification. Methylation of GSTP1, EDNRB and APC promoters was determined by conventional methylation specific polymerase chain reaction analysis in post-digital rectal examination and post-biopsy samples, and correlated with clinical information. RESULTS: Prostate cancer was detected on prostate biopsy in 12 of 17 patients (71%). Promoter methylation was detected in post-digital rectal examination urine specimens for GSTP1 (24%), APC (12%) and EDNRB (66%). Promoter methylation was detected in post-biopsy urine specimens for GSTP1 (18%), APC (18%) and EDNRB (77%). The concordance between post-digital rectal examination and post-biopsy urine samples was 94% for GSTP1 and APC, and 82% for EDNRB. Overall 100% of patients with biopsy proven prostate cancer had at least 1 gene methylated in urine vs 60% of those without evidence of prostate cancer on biopsy. CONCLUSIONS: Gene analysis using conventional methylation specific polymerase chain reaction is a reliable method for detecting abnormal DNA methylation in voided urine samples obtained following digital rectal examination or prostate needle biopsy. The concordance between post-digital rectal examination and post-biopsy urinary samples for promoter methylation is high (82% to 94%), suggesting that urine collected after digital rectal examination may be used for genetic analysis with results similar to those in post-biopsy urine samples.

Adenomatous Polyposis Coli Protein↗
PubMed2005

Percutaneous radio frequency ablation of renal masses: results at a 2-year mean followup.

PURPOSE: We describe our experience with and results of percutaneous computerized tomography guided radio frequency ablation (RFA) for small (less than 4 cm) renal tumors at a 2-year mean followup. MATERIALS AND METHODS: A total of 49 patients (60 renal tumors) with a mean age of 63.9 years underwent percutaneous RFA. Indications for RFA were severe comorbidities or previous abdominal surgery precluding operative management, or hereditary conditions predisposing to multiple tumor recurrence. Persistent enhancement on initial followup imaging was considered incomplete treatment and all such patients underwent biopsy and were offered repeat RFA. Enhancement or enlargement on subsequent imaging was considered tumor recurrence and these patients were counseled regarding further therapy. RESULTS: Three patients (4 tumors) were excluded from evaluation due to death from unrelated causes or loss to followup. A total of 46 patients (56 tumors) were available for evaluation at a mean followup of 27.5 months (range 12 to 48). Six tumors were incompletely treated with the first RFA and successfully treated with a second session. Recurrences after successful initial treatment were seen in 3 of 46 patients. These recurrences developed 24, 25 and 31 months following RFA, respectively, and all occurred in patients with a central tumor of 3.0 cm or greater. Overall local control was achieved in 94.6% of tumors (53 of 56). CONCLUSIONS: RFA is an emerging alternative treatment modality for small renal tumors. Larger (greater than 3.0 cm) central tumors represent unique technical challenges, making these tumors more prone to recurrence. Long-term followup is needed to establish the oncological durability of this technique.

Adult↗
PubMed2005

Long-term survival analysis after laparoscopic radical nephrectomy.

PURPOSE: This report assesses the long-term oncological efficacy of laparoscopic radical nephrectomy compared with open radical nephrectomy in patients with clinically localized renal cell carcinoma. MATERIALS AND METHODS: We analyzed the data from 121 patients who underwent radical nephrectomy between 1991 and 1999 for clinical tumor stage T1/2 N0M0. The medical records of all patients were retrospectively reviewed with emphasis on tumor recurrence and survival. Statistical comparison was performed using Kaplan-Meier analysis. RESULTS: The median followup was 73 months for the laparoscopic group and 80 months for the open group. Of the 67 patients who underwent laparoscopic surgery, 53 survived without any recurrence of disease, 2 are currently alive with metastasis, 2 died of metastatic disease in months 12 and 17, and 10 patients died without any disease recurrence. Laparoscopic port site metastasis did not develop in any patients. Of the 54 who underwent open surgery, 34 survived without any recurrence of disease, 1 currently has metastasis, 6 died of metastasis within 17 to 74 months, and 13 died without any disease recurrence. A comparison of the 5 and 10-year disease-free survival rates of the laparoscopic and open groups revealed no significant differences. In addition, the 5 and 10-year cancer specific and actuarial survival rates were not significantly different. CONCLUSIONS: Based on long-term followup, our evaluation confirmed for clinical tumor stage T1/2 N0M0 that laparoscopic radical nephrectomy is oncologically equivalent to open radical nephrectomy.

Carcinoma, Renal Cell↗
PubMed2004

Laparoscopic radical nephrectomy in obese patients: outcomes and technical considerations.

OBJECTIVES: To review our technique and experience with laparoscopic radical nephrectomy (LRN) in the obese patient population. Obesity has been considered a potential risk factor for poor outcomes in a variety of surgical procedures and has been considered a relative contraindication to laparoscopy. Since 1996, with increased experience and technical modifications, obesity has not been considered a contraindication for laparoscopy at our institution. METHODS: Retrospective data were obtained for all patients who underwent LRN from January 1997 to December 2000. A body mass index (Quetelet's index) greater than 30 was used to define obese patients. Technical modifications included slightly greater insufflation pressures and a lateral shift in trocar sites. The obese laparoscopic group was compared with the nonobese laparoscopic group. RESULTS: Of 101 patients who underwent LRN, 69 were not obese and 32 were obese. No statistically significant differences were observed in any of the analyzed operative data between the nonobese laparoscopic group and obese laparoscopic group, including a mean operative time of 220 and 242 minutes, respectively. Other factors assessed were the time to ambulation, length of hospital stay, conversion rate to an open procedure, and complication rate, which also demonstrated no statistically significant difference. Only one conversion to an open procedure was required in both the obese and the nonobese laparoscopic groups. CONCLUSIONS: With minor technical modifications, LRN can be safely performed in obese patients. Proper trocar site selection and greater insufflation pressures were critical for success. The differences in the intraoperative and postoperative course of LRN in obese and nonobese patients were not statistically significant. Obesity should not be considered a contraindication to laparoscopic nephrectomy.

Aged↗
PubMed2004

An evaluation of the decreasing incidence of positive surgical margins in a large retropubic prostatectomy series.

PURPOSE: Positive surgical margins adversely affect biochemical recurrence-free survival after radical retropubic prostatectomy (RRP) for prostate cancer. We retrospectively reviewed a large series of men who underwent RRP at a single academic university urology program to define the change in the incidence of organ confined (OC) disease and positive surgical margin (SM+) during the last 2 decades. MATERIALS AND METHODS: Between 1982 and 2001, 9,035 men underwent RRP for clinically localized prostate cancer (T1 to T3a) at a single institution. We compared the incidences of OC disease and SM+ in this population. RESULTS: An increasing proportion of men presented with OC disease over time. The incidence of SM+ in the overall RRP population decreased dramatically over time. However, in men with nonorgan confined disease (pT3), the proportion with SM+ was stable and consistently elevated (22.7% to 27.8%), after the initial decrease from the early 1980s (53%). CONCLUSIONS: Widespread early detection programs for prostate cancer resulted in a downward stage migration in men presenting with clinically localized prostate cancer at our institution during the last 2 decades. The decrease in the percentage of men with SM+ was due to the increasing number of men with organ confined disease. These results imply that the decrease in surgical margin rates in the overall RRP population is most likely due to stage migration and improved patient selection, rather than major improvements in surgical technique. The stable percentage of SM+ among men with pT3 disease dictates the need for continued evaluation of surgical technique and the need for effective adjuvant therapy.

Adenocarcinoma↗
PubMed2004

Small renal cell carcinomas: correlation of size with tumor stage, nuclear grade, and histologic subtype.

OBJECTIVE: Our goal was to correlate the size of renal cell carcinoma with tumor stage, nuclear grade, and histologic subtype in patients treated using partial or radical nephrectomy. MATERIALS AND METHODS: We retrospectively reviewed 213 consecutive renal cell carcinomas resected at our institution from 1995 through 1999. Three groups of lesions stratified by size (< or = 3 cm, > 3-5 cm, > 5 cm) were compared with regard to pathologic findings. Statistical significance was assessed using Fisher's exact test. RESULTS: Of 50 lesions 3 cm or smaller, 19 (38%) had extension outside the renal capsule (T3 or T4) and 14 (28%) were a high nuclear grade (Fuhrman grade 3 or 4). Lesions 3 cm or smaller and those greater than 3 cm to 5 cm did not differ statistically with regard to T stage or nuclear grade. Lesions larger than 5 cm showed a statistically higher T stage (p < 0.001) and nuclear grade (p = 0.001) than the other smaller lesions. More non-clear cell tumors were found in the two groups of smaller lesions (p = 0.105) but without statistical significance. The majority (58%) of the tumors were asymptomatic and had been detected incidentally on cross-sectional imaging. Lesions larger than 5 cm were significantly more likely to be symptomatic (p < 0.001). Seventy-nine percent of the tumors 3 cm or smaller were incidental, and these lesions did not differ significantly from the symptomatic lesions with regard to stage, grade, or histology. CONCLUSION: In our study population, renal cell carcinomas up to 3 cm, including asymptomatic lesions, showed a significant incidence of high nuclear grade and tumor extension beyond the renal capsule; these findings support aggressive management of small lesions. Symptomatic status was not an adequate discriminator to guide management. A longitudinal study is necessary to further evaluate the efficacy of current patterns of therapy.

Aged↗
PubMed2003

Percutaneous computed tomography-guided radiofrequency ablation of renal masses in high surgical risk patients: preliminary results.

This article evaluates the safety and efficacy of percutaneous radiofrequency ablation (RFA) delivered by computed tomography (CT) fluoroscopic guidance for the treatment of small, solitary renal lesions in high risk surgical and anesthetic patients. In total, 29 patients with 35 small (</=4 cm) renal lesions underwent a total of 37 CT fluoroscopically guided RFA treatments using a dry RFA technique. Because of medical comorbidities, 26 patients were considered high surgical risk candidates, and 3 patients had von Hippel-Lindau disease. Procedures were performed percutaneously, under intravenous sedation and on an outpatient basis. Renal lesions were monitored on a 3-month basis using precontrast- and postcontrast-enhanced CT imaging to assess for the presence of growth or residual lesion enhancement. Of 37 RFA treatments, 35 (95%) were successfully performed under intravenous sedation and 32 (86%) treatments were performed on an outpatient basis. Over a mean radiographic follow-up period of 9 months, 33 of 35 (94%) renal lesions have required only a single RFA treatment, and 2 patients required a second, successful retreatment for small regions of residual enhancement on follow-up CT imaging. Of 13 renal lesions with a >/=12-month radiographic follow-up interval, 11 (85%) have demonstrated no residual enhancement or growth after RFA. Percutaneous RFA of small, solitary renal lesions is well tolerated in high surgical risk patients. Although early results are encouraging, longer-term follow-up time is necessary to determine the precise role of RFA in this patient population. high resolution video, medium resolution video, low resolution video

Aged↗
PubMed2003

Endoscopic basket extraction of a urethral foreign body.

The presence of a foreign body in the genitourinary tract represents a urologic challenge that often requires prompt intervention. We describe an endoscopic approach that was used for removal of a foreign body located in the prostatic urethra of a schizophrenic man. A nitinol stone basket was used as an effective means for extraction of a large metal screw from the urethra of this patient.

Endoscopy↗
PubMed2003

Interstitial photon radiation.

Most minimally invasive ablative techniques utilize thermal energies for tissue destruction. However, the heat-sink phenomenon may limit the efficacy of radiofrequency ablation and cryotherapy of tissue near blood vessels. One alternative non-temperature-dependent ablative technique is photon radiation. This radiation is dependent on energy and intensity, and its effects are influenced only by the density of the surrounding tissue. Photon radiation therapy may offer a unique alternative for ablating tissue surrounding vascular structures.

Animals↗
PubMed2003

Histologic evolution of high-intensity focused ultrasound in rabbit muscle.

RATIONALE AND OBJECTIVES: The purpose of this study was to examine the histologic evolution over time of rabbit skeletal muscle thermally ablated with high-intensity focused ultrasound. The objectives included determining the extent and focality of damage created by this noninvasive, transcutaneous ablative technology. METHODS: Transcutaneous, thermal ablation with an external focused ultrasound transducer was applied to the paraspinous muscles of 19 rabbits. At varying times, up to 100 days after therapy, single sonications were examined histologically. RESULTS: Initially, only subtle staining changes were identified within lesions. In the chronic phase (day 51-100), the muscle was replaced or infiltrated by variable amounts of scar and fat similar to degenerative muscle disorders. Histologic changes were limited to the tissue within the intensity focus of the transducer and were not seen in intervening tissues. DISCUSSION: The current study took a systematic approach to study the long term, in vivo histologic effects of single HIFU lesions in a nonregenerative tissue. This experience in muscle tissue will provide a basis for understanding ultrasound effects for clinical applications such as treatment of uterine fibroids, cardiac tissue, and sarcomas.

Animals↗
PubMed2002

Laparoscopic pyeloplasty: the first 100 cases.

PURPOSE: Laparoscopic pyeloplasty was developed as a minimally invasive alternative to an open procedure for the treatment of ureteropelvic junction obstruction. Long-term followup has not yet been reported. We present experience with the first 100 consecutive cases of laparoscopic pyeloplasty performed at our institution. MATERIALS AND METHODS: A retrospective review of 100 consecutive laparoscopic pyeloplasties in 99 patients (means age 37.3 years) between August 1993 and January 1999 was performed. All patients had radiographic evidence of obstruction with signs, symptoms or deterioration of renal function. Repair was for primary ureteropelvic junction obstruction in 83 patients and secondary obstruction in 17. The 4 types of repairs performed were Anderson-Hynes dismembered (71 cases), Y-V plasty (20), Heineke-Mirhulicz (8) and Davis intubated ureterotomy (1). Type of repair used was dictated by intraoperative findings. Twenty patients had nonobstructing renal stones and underwent concomitant pyelolithotomy. All patients were assessed for symptoms and radiographic evaluation for anatomical obstruction. RESULTS: Average operating room time was 4.2 hours, which decreased with surgeon experience. Average blood loss was 181 cc and hospital stay was 3.3 days. Two patients required blood transfusion. A crossing vessel was found in 57 patients. With a mean clinical and radiographic followup of 2.7 and 2.2 years, respectively, 96% of the patients were free of obstruction on followup radiographic imaging. Of the patients who underwent concomitant pyelolithotomy, 18 (90%) were stone-free at last followup. All failures occurred within the first postoperative year. There were 12 complications in this series. CONCLUSIONS: In experienced hands laparoscopic pyeloplasty is an effective alternative treatment for symptomatic ureteropelvic junction obstruction. The results appear durable and comparable to open pyeloplasty with decreased postoperative morbidity.

Adolescent↗
PubMed2002

Prediction of outcome after radical prostatectomy in men with organ-confined Gleason score 8 to 10 adenocarcinoma.

OBJECTIVES: Most adenocarcinomas of the prostate with a Gleason score greater than 8 at radical prostatectomy have extraprostatic extension and a high risk of progression. With prostate-specific antigen screening, we have seen some cases of earlier detected, organ-confined, high-grade adenocarcinoma. Few data are available as to the likelihood of cure in these cases. METHODS: We reviewed 27 cases of pathologically organ-confined adenocarcinoma with a prostatectomy Gleason score of 8 to 10. To exclude cases with a significant proportion of Gleason pattern 3, we excluded cases of Gleason score 3+5=8 and Gleason score 5+3=8. All cases of Gleason score 8 at radical prostatectomy were Gleason score 4+4. The prognostic value of the clinical parameters (clinical stage, serum prostate-specific antigen level, age) and pathologic factors (biopsy Gleason score, radical prostatectomy Gleason score, prostatectomy tumor volume) were tested to predict postoperative progression. RESULTS: The mean age at diagnosis was 59.7 years (range 46 to 69) with preoperative serum prostate-specific antigen levels ranging from 1.4 to 28 ng/mL (mean 7.8). All tumors were classified as pathologic Stage T2N0Mx. Fifteen patients (55.6%) had a Gleason score of 8, 11 patients (40.7%) had a Gleason score of 9, and 1 had a Gleason score of 10 (3.7%). Tumor volumes ranged from 0.02 to 1.44 cm(3) (mean 0.56). Follow-up information was available for all men. The mean follow-up for those without progression was 30.6 months (range 7 to 73) and for those with progression was 23.6 months (range 9 to 44). The 33-month actuarial risk of progression was 32%, with 10 men developing progression during the study. None of the preoperative or postoperative variables predicted progression. CONCLUSIONS: Even when high-grade tumor is organ confined, it is associated with a relatively unfavorable short-term outcome that is not predictable on the basis of either preoperative clinicopathologic data or postoperative pathologic information obtained from the radical prostatectomy specimen.

Adenocarcinoma↗
PubMed2002

Laparoscopic pyeloplasty with concomitant pyelolithotomy.

PURPOSE: We present our experience with laparoscopic pyeloplasty plus pyelolithotomy in patients in whom stones were not the cause of ureteropelvic junction obstruction. MATERIALS AND METHODS: A transperitoneal approach was used for laparoscopic pyeloplasty and pyelolithotomy in 19 patients (20 renal units). Before ureteropelvic junction repair stones were extracted through a small pyelotomy that was eventually incorporated into the final pyeloplasty incision. Stones in the renal pelvis were removed with rigid graspers under direct laparoscopic vision. A flexible cystoscope introduced through a port was used to extract stones in the calices. The renal pelvis was reconstructed based on the anatomy of the ureteropelvic junction. RESULTS: A median of 1 stone (range 1 to 28) was recovered. In 11, 8 and 1 patients the Anderson-Hynes dismembered pyeloplasty, Y-V plasty and the Heinecke Mickulicz procedure were performed, respectively. At 3 months 2 patients had residual calculi for a procedural stone-free rate of 90%. There was no evidence of obstruction in 18 of the 20 cases (90%), as confirmed by negative diuretic scan or radiological improvement of hydronephrosis. At a mean followup of 12 months (range 3 to 57) 2 additional patients had recurrent stones for an overall long-term stone-free rate of 80% (16 of 20). CONCLUSIONS: Laparoscopic pyelolithotomy is feasible when combined with pyeloplasty. Our results are comparable to those of stone removal during open pyeloplasty or percutaneous endopyelotomy. The advantages of open surgery appear to be maintained in this minimally invasive approach.

Adult↗
PubMed2002

High intensity focused ultrasound ablation of the vas deferens in a canine model.

PURPOSE: High intensity focused ultrasound is an ablative technology capable of producing thermal coagulative necrosis of sub-surface structures without injuring intervening tissues. We assessed the feasibility of using high intensity focused ultrasound to produce occlusion of the canine vas deferens. MATERIALS AND METHODS: A high intensity focused ultrasound transducer was incorporated into a hand held clip specially designed to grasp the vas deferens transcutaneously. Slots within the jaws of the clip ensured that the vas deferens and high intensity focused ultrasound target zone were properly co-located. We ablated 10 vasa using a range of power and time parameters. At 2 weeks after ablation each vas, epididymis and testis was surgically harvested en bloc. Retrograde vasography was performed to assess vasal occlusion, followed by pathological analysis. RESULTS: High intensity focused ultrasound occlusion of the vas deferens was confirmed in 4 specimens ablated with parameters at the upper end of the parameter range, 2 of the 2 ablated with 7 W. for 60 seconds and 2 of the 4 ablated with 7 W. for 30 seconds. Histological injury was noted in 8 of the 10 ablated specimens. Skin burns that developed over 4 of the targeted vasa were conservatively managed. Bilateral sham procedures in a control dog resulted in patent vasa and no associated skin burns. CONCLUSIONS: We demonstrated the feasibility of noninvasive, transcutaneous high intensity focused ultrasound occlusion of the vas deferens with ablation powers at the upper end of the tested range, that is 7 W. Modifications of the hand held clip and optimization of ablation parameters would likely improve the success rate of this procedure. Refinement of this technology may provide a rapid noninvasive alternative to conventional vasectomy.

Animals↗
PubMedDate not supplied

Laparoscopic radical nephrectomy: long-term outcomes.

BACKGROUND: Although more than a decade of experience with laparoscopic radical nephrectomy indicates it is an alternative to open surgery for localized renal-cell carcinoma (RCC), the long-term oncologic effectiveness of this procedure remains to be established. MATERIALS AND METHODS: A thorough MEDLINE and PubMed literature research on long-term outcomes of laparoscopic radical nephrectomy was performed, and all pertinent articles were reviewed in detail. This review was formulated on the current cancer indication, the oncologic basis, the oncologic efficacy, and the longterm oncologic effectiveness of the procedure, including laparoscopic cytoreductive nephrectomy, with regard to metastasis, port-site tumor recurrence, and the relation to laparoscopic partial nephrectomy. Furthermore, the authors' previous report on the intermediate-term efficacy of laparoscopic radical nephrectomy was updated. RESULTS: With increasing experience, the indications for laparoscopic radical nephrectomy continue to expand. There were many reports of intermediate-term, two reports of long-term, and our up-to-date outcomes analyzing the management of localized RCC that showed effective cancer control with no statistically significant difference between laparoscopic and open radical nephrectomy in the true 5- and 10-year survival analysis. CONCLUSION: Long-term data, critical in the evaluation of any treatment for cancer, are currently available with respect to laparoscopic radical nephrectomy for localized RCC.

Adult↗