Histopathological changes in human prostatic adenoma following neodymium:YAG laser ablation therapy

Re-epithelialization resulted from prostate basal cells in canine prostatic urethra may represent the ideal healing method after two-micron laser resection of the prostate

The purpose of this study is to characterize the re-epithelialization of wound healing in canine prostatic urethra and to evaluate the effect of this re-epithelialization way after two-micron laser resection of the prostate (TmLRP). TmLRP and partial bladder neck mucosa were performed in 15 healthy adult male crossbred canines. Wound specimens were harvested at 3 days, and 1, 2, 3, and 4 weeks after operation, respectively. The histopathologic characteristics were observed by hematoxylin and eosin staining. The expression of cytokeratin 14 (CK14), CK5, CK18, synaptophysin (Syn), chromogranin A (CgA), uroplakin, transforming growth factor-β₁(TGF-β₁), and TGF-β type II receptor in prostatic urethra wound were examined by immunohistochemistry and real-time polymerase chain reaction, respectively. Van Gieson staining was performed to determine the expression of collagen fibers in prostatic urethra and bladder neck would. The results showed that the re-epithelialization of the prostatic urethra resulted from the mobilization of proliferating epithelial cells from residual prostate tissue under the wound. The proliferating cells expressed CK14, CK5, but not CK18, Syn, and CgA and re-epithelialize expressed uroplakin since 3 weeks. There were enhanced TGF-β₁ and TGF-β type II receptor expression in proliferating cells and regenerated cells, which correlated with specific phases of re-epithelialization. Compared with the re-epithelialization of the bladder neck, re-epithelialization of canine prostatic urethra was faster, and the expression of collagen fibers was relatively low. In conclusion, re-epithelialization in canine prostatic urethra resulted from prostate basal cells after TmLRP and this re-epithelialization way may represent the ideal healing method from anatomic repair to functional recovery after injury.

Histological changes of minimally invasive procedures for the treatment of benign prostatic hyperplasia and prostate cancer: clinical implications

PURPOSE

Benign prostatic hyperplasia (BPH) is near universal in aging men, creating tremendous costs in morbidity and surgical treatment. In the last decade numerous nonsurgical minimally invasive methods have emerged for ablation of prostatic tissue.

MATERIALS AND METHODS

We reviewed the recently published English language literature on minimally invasive techniques for treating BPH and cancer with an emphasis on histopathological findings.

RESULTS

We compared the spectrum of contemporary minimally invasive treatments for BPH and cancer, with an emphasis on histopathological results. Clinical results were summarized briefly for each treatment method. These procedures ablate tissue by thermal, cryogenic, chemical or enzymatic injury. The 5-year results for some techniques were promising, although long-term durability is still uncertain, and other methods were in preclinical or early clinical stages. Invariably the treated tissue was devitalized with a thin border of granulation tissue and fibrosis. These procedures have applications for BPH and prostate cancer, although some studies are limited to only 1 disease.

CONCLUSIONS

Minimally invasive procedures show promise of a durable replacement for surgical resection.

A randomized prospective study of laser ablation of the prostate versus transurethral resection of the prostate in men with benign prostatic hyperplasia

OBJECTIVES

To compare the safety and efficacy of laser ablation of the prostate, one of the minimally invasive treatments available for men with benign prostatic hyperplasia, to transurethral resection of the prostate (TURP).

METHODS

A prospective randomized study of 100 men with benign prostatic hyperplasia, with 50 patients in each treatment arm, was conducted. All patients met the entry criteria: age older than 45 years, no history of carcinoma of the prostate, a peak flow rate less than 15 mL/s, medical therapy failure, and the ability to undergo regional or general anesthesia. All patients underwent a preoperative evaluation consisting of the American Urological Association (AUA) symptom score, uroflowmetry, pressure-flow study, transrectal ultrasound for prostate volume, and serum prostate-specific antigen determination. Patients underwent either TURP or laser ablation of the prostate using the potassium titanyl phosphate (KTP)/neodymium: yttrium-aluminum-garnet laser. Patients were seen for follow-up at 1, 3, 6, and 12 months.

RESULTS

The mean age was 68.2 years (range 45 to 90) for the laser group and 67.4 years (range 54 to 82) for the TURP group. The mean AUA symptom score was 22 for the laser group and 21 for the TURP group. The mean peak uroflow rate was 7.6 +/- 3.4 mL/s for the laser group and 6.5 +/- 4.0 mL/s for the TURP group. At 12 months of follow-up, the mean AUA symptom score had decreased to 7 (-69.5%) for the laser group and to 3 (-80.9%) for the TURP group. The mean peak uroflow rate increased to 15.4 mL/s (+ 107.8%) for the laser group and to 16.7 mL/s (+ 150.7%) for the TURP cohort. Seventy-five percent of the laser group had a 50% or greater decrease in their individual AUA symptom score compared with 93% of the TURP group. Sixty-five percent of the laser cohort had a 50% or greater increase in their peak uroflow rate compared with 75% of the TURP cohort.

CONCLUSIONS

Laser prostatectomy produced improvements in the peak flow rate and symptom score similar to those produced by TURP. The patients who underwent laser treatment required a longer period to reach maximum improvement, which probably reflects the lack of tissue debulking at the time of surgery. Further improvement in laser technology will be required to produce more immediate results.

Histomorphological changes after neodymium: YAG laser-coagulation of the human prostate with the Side Focus fiber. Effect of power setting and time

The objective of our study was to determine optimal treatment parameters and appropriate methods of examination for neodymium:yttrium-aluminum-garnet (Nd:YAG) high-power laser coagulation of the human prostate in relation to power setting and time. Transurethral free-beam laser coagulation was performed with the Side Focus side-firing laser fiber in ten patients prior to planned radical surgery, of whom six underwent transperitoneal laparoscopic lymphadenectomy and laser coagulation 4-9 days prior to open surgery. Depth and volume of coagulated prostatic tissue were measured at power setting/time combinations of 40 W/90 s and 60 W/60 s, respectively, while holding total energy delivery constant. Microscopic examination in the early phase showed that epithelial cells had become loose from the basal-cell membrane. By 4-9 days there was evidence of conspicuous squamous epithelial metaplasia with a high proliferation rate as a sign of re-epithelialization. Using the Side Focus side-firing laser fiber, both treatment modalities showed comparable volume coagulation. In contrast there was a significant difference between those prostates removed at 4-9 days and those removed at 60-210 min after laser coagulation. We conclude that laser-induced changes in the human prostate are conclusively discernible only after 4 days.

Mechanism of healing of the human prostatic urethra following thermal injury

OBJECTIVES

To characterize histopathologically the healing response of the prostatic urethra after laser thermal coagulation and standard transurethral resection of the prostate (TURP).

METHODS

The study included 31 patients who underwent radical prostatectomy because of malignancy. Twenty-two (first group) had laser radiation either at the time of surgery (18 patients) or from 1 to 12 weeks prior to prostatectomy (4 patients). Nine patients (second group) had TURP from 6 to 96 weeks prior to prostatectomy.

RESULTS

Coagulation necrosis followed by sloughing was observed during the first 10 weeks after laser radiation. After the first 10 weeks, the healing response was otherwise stereotypical and comparable for both groups of patients. Re-epithelialization was prominent and resulted from migration of proliferating epithelial cells from the remaining acinar and ductal epithelium. Squamous metaplasia was conspicuous and present indefinitely. Development of inflammatory reaction followed by granulation tissue and well-organized fibroblastic stroma were sequentially recognized, but less prominent. Complete re-epithelialization and wound sealing was not observed before the first 12 weeks of healing.

CONCLUSIONS

Our study suggests that laser thermal coagulation and TURP are partial-thickness injuries. Because of the abundant germinal epithelium in the remaining prostatic glands and ducts, the healing response of the prostatic urethra is relatively unimpeded and free of contractures, analogous to second-degree skin burns.

Healing response of the canine prostate to Nd:YAG laser radiation

The objective of the study was to characterize the healing response of the canine prostate to laser thermal injury. The study included 20 canine prostates that underwent transurethral laser radiation. The prostates were retrieved 1 hr after laser radiation in 7 dogs (acute group), and from 3 days to 9 weeks in 13 dogs (chronic group). Two distinct features were observed. First, reepithelialization of the prostate urethra resulted from mobilization of proliferating epithelial cells from acinar and ductal prostatic epithelium into the cavity surface, and not from the edges of the wound at the bladder neck. Squamous cell metaplasia was a prominent feature of reepithelialization. Second, the healing process in the canine prostate was relatively unimpeded. The large glandular component provided abundant germinal epithelial growth, and the absence of stromal elements allowed for complete sloughing of necrotic tissue without residual eschars. Further, the lesions in the chronic group had a tendency to be larger than those in the acute group, suggesting that extended delayed necrosis may occur at deep prostatic tissue layers.

Further evaluation of transurethral laser ablation of the prostate in patients treated with anticoagulant therapy

Transurethral Nd:YAG laser ablation of the prostate gland was used to treat benign prostatic hyperplasia (BPH) in 20 patients on Warfarin anticoagulant therapy, and in two patients with abnormal coagulation parameters secondary to haematologic disorders. Preliminary results for the first 10 of these patients has been reported previously. The mean pre-operative international normalized ratio (INR) was 2.6 (range 1.19 to 5.25) and the mean prostate volume was 56 cc (13.6-112 cc). All patients had significant subjective and objective indicators of prostatic obstruction and six patients were in urinary retention. Postoperative improvement in symptom score, maximum flow rate and post-void residual was noted in 82% of patients at 3 months, 89% at 6 months and 75% at 1 year. Two patients have required revision laser or transurethral resection of the prostate (TURP) for persistent obstruction, while one patient required revision TURP for intractable haematuria. Three patients developed haematuria requiring transfusion while four patients had mild haematuria requiring no intervention. Laser ablation of the prostate can be used successfully and safely to treat prostatic obstruction in patients with abnormal coagulation parameters, or in those who are fully anticoagulated. Anticoagulation can be maintained during surgery in this group unlike TURP where pre-operative reversal is necessary with reinstitution of therapy several days postoperatively. Other authors report at least a 50% blood transfusion rate in this group. Laser prostatectomy appears the more appealing surgical option in these patients.