Detailed urethral dosimetry in the evaluation of prostate brachytherapy-related urinary morbidity

The nature and extent of urinary morbidity in relation to prostate brachytherapy urethral dosimetry

PURPOSE

This study investigates whether the location and dose of urethral radiation received during transperineal interstitial permanent prostate brachytherapy determine the degree and type of urinary symptoms experienced subsequently.

METHODS AND MATERIALS

Data from a prospectively acquired database of 219 men treated with transperineal interstitial permanent prostate brachytherapy using (125)I (prescribed dose 145Gy) between May 2001 and June 2003 were reviewed. To assess the effect of regional urethral dosimetry, the prostate was divided into equal thirds (proximal, mid, and apical) with doses beyond this considered distal. Mean and peak doses for each region were correlated with total International Prostate Symptom Score (IPSS) and the irritative and obstructive components of the score. IPSS values at 1 month postimplant, time to resolution of IPSS, and the need for catheterization were used as outcome variables and analyzed with respect to dose using logistic and linear regression.

RESULTS

Peak and average doses with standard deviations to the proximal urethra were 168 (24) and 147 (24)Gy, mid prostatic urethra 192 (24) and 181 (21)Gy, and apical urethra 201 (28) and 192 (26)Gy. Catheterization was required for 28 men and was predicted by larger pretreatment transrectal ultrasound (TRUS) volume (OR 1.06 per unit change; 95% CI 1.03-1.10; p<0.001) and lower UV(150) (OR 0.30; 95% CI 0.13-0.68; p=0.004) in multivariate analysis. Greater IPSS at baseline (p<0.001) and preoperative TRUS volume (p=0.012) but conversely smaller D(30) doses (p=0.003) were predictive of IPSS outcomes at 1 month. IPSS returned to within two points of baseline for 72.2% of men by 1 year and 83.3% by 24 months. This was predicted by higher IPSS at baseline (OR 6.0; 95% CI 2.72-13.22; p<0.001), higher D(30) (OR 1.17; 95% CI 1.01-1.36; p=0.031), and lower V(100) (OR 0.39; 95% CI 0.22-0.70; p=0.002). Prostatic urethral segmental dosimetry failed to predict the need for catheterization, the nature of the urinary symptoms, or their time to resolution.

CONCLUSIONS

Previously identified factors of importance for urinary morbidity such as pretreatment prostate volume and baseline urinary function were reemphasized in this study. Regional urethral dosimetry within contemporary practice does not seem to influence the nature or extent of urinary symptoms after prostate brachytherapy. Consequently, region sparing dosimetric modifications are not warranted to alter symptomatic outcomes.

The influence of geometrical changes on the dose distribution after I-125 seed implantation of the prostate

PURPOSE

After prostate implantation, dose calculation is usually based on a single imaging session, assuming no geometrical changes occur during the months of dose accumulation. In this study, the effect of changes in anatomy and implant geometry on the dose distribution was investigated.

MATERIALS AND METHODS

One day, 1 month and 312 months after seed implantation, a combined TRUS-CT scan was made of 13 patients. Based on these scans changes in dose rate distribution were determined in prostate, urethra and bladder and a 'geometry corrected' dose distribution was estimated.

RESULTS

When based on the day-1 scan, parameters representing high dose volumes in prostate and urethra were largely underestimated: V150 of the prostate 18+/-10% and V120 of the urethra 47+/-32%. The dose to a 2cm(3) hotspot in the bladder wall (D2cc), however, was overestimated by 31+/-35%. Parameters based on scans 1 month post-implant or later were all within +/-5% of geometry corrected values.

CONCLUSION

Values meant to indicate the adequacy of dose coverage of the prostate, V100 and D90, were not influenced by geometrical changes and were independent of the post-implant scan date. Other parameters representing high dose volumes changed strongly within the first month after implantation.

Investigation of bladder dose and volume factors influencing late urinary toxicity after external beam radiotherapy for prostate cancer

BACKGROUND

We sought to identify the bladder dose-volume factors associated with an increased risk of late urinary toxicity among prostate cancer patients treated with radiotherapy.

METHODS AND MATERIALS

This retrospective analysis included data from 128 prostate cancer patients treated on protocol with 2 Gy/fraction to 46 Gy followed by a boost to 78 Gy. The endpoint for this analysis was Grade 1 or greater late genitourinary (GU) toxicity occurring within two years of treatment. The Lyman-Kutcher-Burman, mean dose, threshold dose, and hottest volume models were fitted to the toxicity data using the maximum likelihood method.

RESULTS

Model fits based on dose-volume histograms tended to fit the toxicity data better than models based on dose-wall histograms. The hottest volume (hotspot) model was found to be the best-fitting model investigated. The best fit was for the hottest 2.9% of bladder (95% CI, 1.1-6.8%). This model has an area under the receiver operating characteristic curve of 0.74. The hotspot model separated the patients into clinically meaningful subgroups with approximately 25% of the patients who received <78 Gy to the hottest 2.9% of bladder had GU toxicity at eight years compared with approximately 50% when the dose was > or =78 Gy (p = 0.002).

CONCLUSION

This provides the first evidence supporting that bladder "hotspots" are related to GU toxicity within two years after external beam radiotherapy for prostate cancer. Confirming data are needed from other investigators. Particular attention should be given to hotspots higher than 78 Gy in bladder in radiation treatment planning.

Oncologic Emergencies

It has been estimated that genitourinary malignancies will account for 25% of new cancer diagnoses in the United States in 2005 (Jemal et al. 2005). While the incidence of many of these malignancies has increased over the past two decades, the mortality rates appear to be decreasing. Early cancer detection combined with improvements in surgical and nonsurgical oncologic therapy account for these trends. Although not common, newly diagnosed cancer patients occasionally present in an emergent, life-threatening manner that warrants immediate medical or surgical intervention. As the prevalence of genitourinary malignancies continues to expand, additional patients can be expected to develop disease or treatment-related complications. This chapter will serve to review the diagnosis and management of oncologic emergencies as they pertain to the urologist.

The pathophysiology of lower urinary tract symptoms after brachytherapy for prostate cancer

OBJECTIVES

To determine the spectrum of pathophysiology underlying the lower urinary tract symptoms (LUTS) persisting for > or = 6 months after brachytherapy for localized prostate cancer.

PATIENTS AND METHODS

A database of men from two practice settings was searched for men who developed LUTS persisting for > or = 6 months after completing brachytherapy for localized prostate cancer. Patients were evaluated with a structured history and physical examination, International Prostate Symptom Score (IPSS), 24-h voiding diary, noninvasive free-flow uroflowmetry, postvoid residual urine volume (PVR), cystoscopy and a video-urodynamic study. Specific data collected included symptoms, elapsed time since brachytherapy, Gleason score, IPSS, total number of voids/24 h, maximum voided volume, cystoscopic findings, and urodynamics findings (PVR, maximum urinary flow rate, Schaefer obstruction grade, Watts factor, incidence of detrusor overactivity (DO) urethral obstruction and low bladder compliance). These data were compared with those from a previous study of men with LUTS who did not have prostate cancer.

RESULTS

The study included 47 men (aged 54-88 years); the median (range) interval between brachytherapy and evaluation was 1.5 (0.5-13) years. Thirty-seven men complained of overactive bladder symptoms (79%), and 31 of incontinence (71%), 21 of obstructive symptoms (44%), and persistent dysuria in 12 (26%). Comparison of urodynamic findings in men with unselected causes of LUTS vs LUTS due to brachytherapy revealed the following comparisons: DO in 252 of 541 (47%) unselected vs 28 of 33 (85%) brachytherapy, (P < 0.001); and urethral obstruction in 374 of 541 (69%) unselected vs 24 of 33 (73%) brachytherapy (P = 0.85).

CONCLUSION

The pathophysiology and severity of persistent LUTS in men after brachytherapy differs from that of men with LUTS in the general population. Men after brachytherapy have a much higher incidence of DO, prostatic and urethral strictures and prostatic urethral stones.

Risk Factors for the Development of Prostate Brachytherapy Related Urethral Strictures

PURPOSE

We identified clinical, treatment and dosimetric parameters associated with the development of urethral strictures following permanent prostate brachytherapy.

MATERIALS AND METHODS

From April 1995 through April 2003, 1,186 consecutive patients underwent prostate brachytherapy for clinical stage T1b-T3a NxM0 (2002 American Joint Committee on Cancer) prostate cancer. The treatment plan included supplemental XRT in 625 patients (52.7%) and androgen deprivation therapy in 465 (39.2%). Median followup was 4.3 years. Multiple clinical, treatment and dosimetric parameters were evaluated in univariate and multivariate analyses to identify independent predictors for urethral stricture disease.

RESULTS

A total of 29 patients had brachytherapy related urethral strictures. All strictures involved the BM urethra with a 9-year actuarial risk of 3.6% and a median time to development of 2.4 years. The mean radiation dose to the BM urethra was significantly greater in patients with vs without stricture (p = 0.002). On multivariate analysis the BM urethral dose and supplemental XRT predicted urethral stricture. All except 3 patients were successfully treated with urethral dilation or internal optical urethrotomy.

CONCLUSIONS

Brachytherapy related urethral stricture disease correlates highly with the radiation dose to the BM urethra. Careful attention to brachytherapy preplanning and intraoperative execution along with the judicious use of supplemental XRT is essential to minimize the incidence of stricture disease.

Severity categories of the International Prostate Symptom Score before, and urinary morbidity after, permanent prostate brachytherapy

OBJECTIVE

To determine if the International Prostate Symptom Score (IPSS) before seed implantation, stratified into mild (0-7), moderate (8-19) and severe (>20) categories, predicts brachytherapy-related morbidity in terms of IPSS resolution, catheter dependency and the need for surgical intervention after brachytherapy.

PATIENTS AND METHODS

From January 1998 to September 2003, 1034 consecutive patients had permanent interstitial brachytherapy for clinical stage T1b-T3a NXM0 (2002 system) prostate cancer. Of the 1034 patients, 739 (71.5%) presented with an IPSS of 0-7, 287 (27.7%) of 8-19, and eight (0.8%) of > or = 20. The IPSS 8-19 cohort was further stratified into 8-14 (237 men) and 15-19 (50 men) subgroups. The median follow-up was 38.2 months. In all patients, an alpha-blocker was initiated before brachytherapy and continued at least until the IPSS normalized, the latter defined as a return to within 1 point of that before implantation. A median of 21 IPSS questionnaires were obtained per patient. Several clinical, treatment and dosimetric variables were evaluated as predictors of urinary morbidity.

RESULTS

For the entire cohort, the IPSS peaked at a mean of 0.5 months after implantation and resolved at a mean of 1.7 months. At 5 years after brachytherapy, 90.1% of patients at risk (88.8%, 95.5%, and four of eight patients with a pre-implant IPSS of 0-7, 8-19 and > or = 20, respectively) were within the IPSS 0-7 category. Compared to the pre-implant IPSS, 13 patients (8%) were assigned to a higher IPSS severity category. Neither prolonged urinary catheter dependency (>5 days; 16 patients, 1.5%) or transurethral resection of the prostate (TURP, 17 patients, 1.6%) depended on the pre-implant IPSS subgroup. In Cox regression analysis, IPSS resolution was best predicted by pre-implant IPSS, prolonged catheter dependency by patient age, and TURP by any catheter dependency, the maximum IPSS increase and the maximum urethral dose.

CONCLUSIONS

The IPSS before implantation predicted the resolution of IPSS after brachytherapy, but did not correlate with substantial urinary morbidity, including catheter dependency or the need for TURP. At 5 years after brachytherapy, 90.1% of patients at risk were assigned to the IPSS 0-7 category.

The influence of isotope and prostate volume on urinary morbidity after prostate brachytherapy

PURPOSE

To evaluate the influence of isotope and prostate size on International Prostate Symptom Score (IPSS) normalization, catheter dependency, and the need for surgical intervention secondary to bladder outlet obstruction after prostate brachytherapy.

METHODS AND MATERIALS

Between January 1998 and June 2003, 976 consecutive patients underwent brachytherapy for clinical stage T1b-T3a (2002 American Joint Committee on Cancer) prostate cancer. Seven hundred eighty-nine (80.8%) were implanted with 103Pd and 187 (19.2%) with 125I. The median follow-up was 41.2 months. Patients were stratified into size cohorts < or = 25 cm3, 25.1-35 cm3, 35.1-45 cm3, and >45 cm3. Four hundred eighteen patients (42.8%) received androgen deprivation therapy (ADT). Four hundred eighty-six patients (49.7%) received supplemental external-beam radiation therapy (XRT). In all patients, an alpha blocker was initiated before implantation and continued at least until the IPSS returned to baseline. IPSS resolution was defined as a return to within one point of baseline. The median number of IPSS determinations per patient was 21. Clinical, treatment, and dosimetric parameters evaluated included patient age, pretreatment PSA, Gleason score, clinical T stage, percent positive biopsies, preimplant IPSS, ultrasound volume, planning volume, isotope, V(100/150/200), D(90), urethral dose (average and maximum), supplemental XRT, ADT, and the duration of ADT (< or = 6 months vs. >6 months). Catheter dependency and the need for postsurgical intervention were also evaluated.

RESULTS

For both isotopes and all prostate size cohorts, IPSS peaked 1 month after implantation and returned to baseline at a mean of 1.9 months. Stratification of prostate size cohorts by isotope demonstrated no significant differences in prolonged catheter dependency (> or = 5 days), IPSS resolution, or postimplant surgical intervention. In Cox regression analysis, IPSS normalization was best predicted by preimplant IPSS, XRT, and any need for a catheter after brachytherapy. Catheter dependency correlated with prostate size and ADT, whereas the need for surgical intervention was most closely related to any catheter dependency, maximum urethral dose, ADT, and maximum IPSS increase.

CONCLUSIONS

Regardless of prostate size, isotope did not impact IPSS resolution, catheter dependency, or the need for postbrachytherapy surgical intervention. Although prostate size did predict for short-term (<5 days) catheter dependency, it did not influence IPSS resolution or the need for surgical intervention.