Dosimetric consequences of using a surrogate urethra to estimate urethral dose after brachytherapy for prostate cancer

Evaluation of T2-Weighted MRI for Visualization and Sparing of Urethra with MR-Guided Radiation Therapy (MRgRT) On-Board MRI

Simple Summary

Stereotactic body radiation therapy (SBRT) has become a standard of care option for prostate cancer patients, utilizing large fractionated dose to shorten treatment times. However, genitourinary (GU) toxicity associated with urethral injury remains prevalent due to non-trivial urethra delineation and sparing at treatment planning and treatment delivery. The aim of our study was to evaluate two optimized urethral MRI sequences (3D HASTE and 3D TSE) with a 0.35T MR-guided radiotherapy (MRgRT) system for urethral visibility and delineation. Among 11 prostate cancer patients, a radiation oncologist qualitatively scored MRgRT 3D HASTE as having the best urethra visibility, superior to CT, clinical MRgRT 3D bSSFP, MRgRT 3D TSE, and similar to diagnostic 3T (2D/3D) T2-weighetd MRI. Moreover, urethra contours from different imaging and clinical workflows demonstrated significant urethra localization variability. Optimized 3D MRgRT HASTE can provide urethral visualization and delineation within an MRgRT workflow for urethral sparing, avoiding cross-modality/system registration errors.

Abstract

Purpose: To evaluate urethral contours from two optimized urethral MRI sequences with an MR-guided radiotherapy system (MRgRT). Methods: Eleven prostate cancer patients were scanned on a MRgRT system using optimized urethral 3D HASTE and 3D TSE. A resident radiation oncologist contoured the prostatic urethra on the patients’ planning CT, diagnostic 3T T2w MRI, and both urethral MRIs. An attending radiation oncologist reviewed/edited the resident’s contours and additionally contoured the prostatic urethra on the clinical planning MRgRT MRI (bSSFP). For each image, the resident radiation oncologist, attending radiation oncologist, and a senior medical physicist qualitatively scored the prostatic urethra visibility. Using MRgRT 3D HASTE-based contouring workflow as baseline, prostatic urethra contours drawn on CT, diagnostic MRI, clinical bSSFP and 3D TSE were evaluated relative to the contour on 3D HASTE using 95th percentile Hausdorff distance (HD95), mean-distance-to-agreement (MDA), and DICE coefficient. Additionally, prostatic urethra contrast-to-noise-ratios (CNR) were calculated for all images. Results: For two out of three observers, the urethra visibility score for 3D HASTE was significantly higher than CT, and clinical bSSFP, but was not significantly different from diagnostic MRI. The mean HD95/MDA/DICE values were 11.35 ± 3.55 mm/5.77 ± 2.69 mm/0.07 ± 0.08 for CT, 7.62 ± 2.75 mm/3.83 ± 1.47 mm/0.12 ± 0.10 for CT + diagnostic MRI, 5.49 ± 2.32 mm/2.18 ± 1.19 mm/0.35 ± 0.19 for 3D TSE, and 6.34 ± 2.89 mm/2.65 ± 1.31 mm/0.21 ± 0.12 for clinical bSSFP. The CNR for 3D HASTE was significantly higher than CT, diagnostic MRI, and clinical bSSFP, but was not significantly different from 3D TSE. Conclusion: The urethra’s visibility scores showed optimized urethral MRgRT 3D HASTE was superior to the other tested methodologies. The prostatic urethra contours demonstrated significant variability from different imaging and workflows. Urethra contouring uncertainty introduced by cross-modality registration and sub-optimal imaging contrast may lead to significant treatment degradation when urethral sparing is implemented to minimize genitourinary toxicity.

Visualising the proximal urethra by MRI voiding scan: results of a prospective clinical trial evaluating a novel approach to radiotherapy simulation for prostate cancer

Background:

Delineating the proximal urethra can be critical for radiotherapy planning but is challenging on computerised tomography (CT) imaging.

Materials and methods:

We trialed a novel non-invasive technique to allow visualisation of the proximal urethra using a rapid sequence magnetic resonance imaging (MRI) protocol to visualise the urinary flow in patients voiding during the simulation scan.

Results:

Of the seven patients enrolled, four were able to void during the MRI scan. For these four patients, direct visualisation of urinary flow through the proximal urethra was achieved. The average volume of the proximal urethra contoured on voiding MRI was significantly higher than the proximal urethra contoured on CT, 4·07 and 1·60 cc, respectively (p = 0·02). The proximal urethra location also differed; the Dice coefficient average was 0·28 (range 0–0·62).

Findings:

In this small, proof-of-concept prospective clinical trial, the volume and location of the proximal urethra differed significantly when contoured on a voiding MRI scan compared to that determined by a conventional CT simulation. The shape of the proximal urethra on voiding MRI may be more anatomically correct compared to the proximal urethra shape determined with a semi-rigid catheter in place.

A comparison of treatment planning techniques for low-dose-rate (LDR) prostate brachytherapy

PURPOSE

The purpose of this study was to compare low-dose-rate prostate brachytherapy treatment plans created using three retrospectively applied planning techniques with plans delivered to patients.

METHODS AND MATERIALS

Treatment plans were created retrospectively on transrectal ultrasound (TRUS) scans for 26 patients. The technique dubbed 4D Brachytherapy was applied, using TRUS and MRI to obtain prostatic measurements required for the associated webBXT online nomogram. Using a patient's MRI scan to create a treatment plan involving loose seeds was also explored. Plans delivered to patients were made using an intraoperative loose seed TRUS-based planning technique. Prostate V₁₀₀ (%), prostate V₁₅₀ (%), prostate D₉₀ (Gy), rectum D_0.1cc (Gy), rectum D_2cc (Gy), urethra D₁₀ (%), urethra D₃₀ (%), and prostate volumes were measured for each patient. Statistical analysis was used to assess and compare plans.

RESULTS

Prostate volumes measured by TRUS and MRI were significantly different. Prostate volumes calculated by the webBXT online nomogram using TRUS- and MRI-based measurements were not significantly different. Compared with delivered plans, TRUS-based 4D Brachytherapy plans showed significantly lower rectum D_0.1cc (Gy) values, MRI-based 4D Brachytherapy plans showed significantly higher prostate V₁₀₀ (%) values and significantly lower rectum D_0.1cc (Gy), urethra D₁₀ (%), and urethra D₃₀ (%) values, and loose seed MRI-based plans showed significantly lower prostate V₁₀₀ (%), prostate D₉₀ (Gy), rectum D_0.1cc (Gy), rectum D_2cc (Gy), urethra D₁₀ (%), and urethra D₃₀ (%) values.

CONCLUSIONS

TRUS-based 4D Brachytherapy plans showed similar dosimetry to delivered plans; rectal dosimetry was superior. MRI can be integrated into the 4D Brachytherapy workflow. The webBXT online nomogram overestimates the required number of seeds.

The urethral position may shift due to urethral catheter placement in the treatment planning for prostate radiation therapy

PURPOSE

To determine the best method to contour the planning organ at risk volume (PRV) for the urethra, this study aimed to investigate the displacement of a Foley catheter in the urethra with a soft and thin guide-wire.

METHODS

For each patient, the study used two sets of computed tomography (CT) images for radiation treatment planning (RT-CT): (1) set with a Foley urethral catheter (4.0 mm diameter) plus a guide-wire (0.46 mm diameter) in the first RT-CT and (2) set with a guide-wire alone in the second CT recorded 2 min after the first RT-CT. Using three fiducial markers in the prostate for image fusion, the displacement between the catheter and the guide-wire in the prostatic urethra was calculated. In 155 consecutive patients treated between 2011 and 2017, 5531 slices of RT-CT were evaluated.

RESULTS

Assuming that ≥3.0 mm of difference between the catheter and the guide-wire position was a significant displacement, the urethra with the catheter was displaced significantly from the urethra with the guide-wire alone in > 20% of the RT-CT slices in 23.2% (36/155) of the patients. The number of patients who showed ≥3.0 mm anterior displacement with the catheter in ≥20% RT-CT slices was significantly larger at the superior segment (38/155) than at the middle (14/155) and inferior segments (18/155) of the prostatic urethra (p < 0.0167).

CONCLUSIONS

The urethral position with a Foley catheter is different from the urethral position with a thin and soft guide-wire in a significant proportion of the patients. This should be taken into account for the PRV of the urethra to ensure precise radiotherapy such as in urethra-sparing radiotherapy.

Multi-atlas-based segmentation of prostatic urethra from planning CT imaging to quantify dose distribution in prostate cancer radiotherapy

BACKGROUND AND PURPOSE

Segmentation of intra-prostatic urethra for dose assessment from planning CT may help explaining urinary toxicity in prostate cancer radiotherapy. This work sought to: i) propose an automatic method for urethra segmentation in CT, ii) compare it with previously proposed surrogate models and iii) quantify the dose received by the urethra in patients treated with IMRT.

MATERIALS AND METHODS

A weighted multi-atlas-based urethra segmentation method was devised from a training data set of 55 CT scans of patients receiving brachytherapy with visible urinary catheters. Leave-one-out cross validation was performed to quantify the error between the urethra segmentation and the catheter ground truth with two scores: the centerlines distance (CLD) and the percentage of centerline within a certain distance from the catheter (PWR). The segmentation method was then applied to a second test data set of 95 prostate cancer patients having received 78Gy IMRT to quantify dose to the urethra.

RESULTS

Mean CLD was 3.25±1.2mm for the whole urethra and 3.7±1.7mm, 2.52±1.5mm, and 3.01±1.7mm for the top, middle, and bottom thirds, respectively. In average, 53% of the segmented centerlines were within a radius<3.5mm from the centerline ground truth and 83% in a radius<5mm. The proposed method outperformed existing surrogate models. In IMRT, urethra DVH was significantly higher than prostate DVH from V74Gy to V79Gy.

CONCLUSION

A multi-atlas-based segmentation method was proposed enabling assessment of the dose within the prostatic urethra.

Acute Urinary Morbidity Following Stereotactic Body Radiation Therapy for Prostate Cancer with Prophylactic Alpha-Adrenergic Antagonist and Urethral Dose Reduction

BACKGROUND

Stereotactic body radiation therapy (SBRT) delivers high doses of radiation to the prostate while minimizing radiation to the adjacent critical organs. Large fraction sizes may increase urinary morbidity due to unavoidable treatment of the prostatic urethra. This study reports rates of acute urinary morbidity following SBRT for localized prostate cancer with prophylactic alpha-adrenergic antagonist utilization and urethral dose reduction (UDR).

METHODS

From April 2013 to September 2014, 102 patients with clinically localized prostate cancer were treated with robotic SBRT to a total dose of 35-36.25 Gy in five fractions. UDR was employed to limit the maximum point dose of the prostatic urethra to 40 Gy. Prophylactic alpha-adrenergic antagonists were initiated 5 days prior to SBRT and continued until resolution of urinary symptoms. Quality of life (QoL) was assessed before and after treatment using the American Urological Association Symptom Score (AUA) and the Expanded Prostate Cancer Index Composite-26 (EPIC-26). Clinical significance was assessed using a minimally important difference (MID) of one half SD change from baseline.

RESULTS

One hundred two patients underwent definitive prostate SBRT with UDR and were followed for 3 months. No patient experienced acute urinary retention requiring catheterization. A mean baseline AUA symptom score of 9.06 significantly increased to 11.83 1-week post-SBRT (p = 0.0024) and 11.84 1-month post-SBRT (p = 0.0023) but returned to baseline by 3 months. A mean baseline EPIC-26 irritative/obstructive score of 87.7 decreased to 74.1 1-week post-SBRT (p < 0.0001) and 77.8 1-month post-SBRT (p < 0.0001) but returned to baseline at 3 months. EPIC-26 irritative/obstructive score changes were clinically significant, exceeding the MID of 6.0. At baseline, 8.9% of men described their urinary function as a moderate to big problem, and that proportion increased to 37.6% 1 week following completion of SBRT before returning to baseline by 3 months.

CONCLUSION

Stereotactic body radiation therapy for localized prostate cancer with utilization of prophylactic alpha-adrenergic antagonist and UDR was well tolerated as determined by acute urinary function and bother, and symptoms were comparable to those observed following conventionally fractionated external beam radiation therapy (EBRT). Longer follow-up is required to assess long-term toxicity and efficacy following SBRT with UDR.

Urinary morbidity after permanent prostate brachytherapy - impact of dose to the urethra vs. sources placed in close vicinity to the urethra

BACKGROUND AND PURPOSE

The impact of the dose to the urethra and sources placed close to the urethra on urinary morbidity after permanent prostate brachytherapy (PPB) is not well known.

MATERIALS AND METHODS

Fifty-nine patients were surveyed prospectively before treatment (A), 1 month after (B) and > 1 year after PPB (C) using a validated questionnaire (Expanded Prostate Cancer Index Composite). Computed tomography (CT) postimplant scans were performed at days 1 (Foley catheter in situ) and 30 after PPB and sources within 5mm of the urethra at day 1 were identified.

RESULTS

As opposed to the urethral dose-volume histogram, a larger number of sources within 5mm of the urethra at day 1 predicted significantly larger urinary bother score changes at times B and C - with an impact on incontinence and frequency (e.g. moderate/big problem with leaking urine in 25% vs. 3%, p = 0.02; moderate/big problem with frequent urination in 33% vs. 7%, p < 0.01, at time C with vs. without ≥ 3 sources in a single strand placed close to the urethra).

CONCLUSIONS

Placement of sources with a minimum distance of a few mm to the urethra should be a major aim to avoid urinary morbidity irrespective of the urethral dose-volume histogram.

Factors associated with postoperative pulmonary morbidity after esophagectomy for cancer

BACKGROUND

Most studies analyzing risk factors for pulmonary morbidity date from the early 1990s. Changes in technology and treatment such as minimally invasive esophagectomy (MIE) and neoadjuvant treatment mandate analysis of more contemporary cohorts.

METHODS

Predictive factors for overall and specific pulmonary morbidity in 858 patients undergoing esophagectomy between 1998 and 2008 in five Australian university hospitals were analyzed by logistic regression models.

RESULTS

A total of 394 patients underwent open esophagectomy, and 464 patients underwent MIE. A total of 259 patients received neoadjuvant chemoradiotherapy, 139 preoperative chemotherapy alone, and 2 preoperative radiotherapy alone. In-hospital mortality was 3.5%. Smoking and the number of comorbidities were risk factors for overall pulmonary morbidity (odds ratio [OR] 1.47, P = 0.016; OR 1.35, P = 0.001) and pneumonia (OR 2.29, P = 0.002; 1.56, P = 0.005). The risk of respiratory failure was higher in patients with more comorbidities (OR 1.4, P = 0.035). Respiratory comorbidities (OR 3.81, P = 0.017) were strongly predictive of postoperative acute respiratory distress syndrome (ARDS). ARDS (4.51, P = 0.032) or respiratory failure (OR 8.7, P < 0.001), but not anastomotic leak (OR 2.22, P = 0.074), were independent risk factors for death. MIE (OR 0.11, P < 0.001) and thoracic epidural analgesia (OR 0.12, P = 0.003) decreased the risk of respiratory failure. Neoadjuvant treatment was not associated with an increased risk of pulmonary complications.

CONCLUSIONS

Preoperative comorbidity and smoking were risk factors for respiratory complications, whereas neoadjuvant treatment was not. MIE and the use of thoracic epidural analgesia decreased the risk of respiratory failure. Respiratory failure and ARDS were the only independent factors associated with an increased risk of in-hospital death, whereas anastomotic leakage was not.

Is the use of a surrogate urethra an option in prostate high-dose-rate brachytherapy?

PURPOSE

To investigate the accuracy and the dosimetric consequences of substituting a surrogate urethra assumed to be at the geometric center of the prostate, in place of the true urethra when using high-dose-rate (HDR) brachytherapy for the treatment of prostate cancer.

METHODS AND MATERIALS

One hundred prostate cancer patients treated with HDR brachytherapy constituted the study group. A pre-plan was made with the urethra visualized. The true urethra was defined, and a surrogate urethra was placed at the geometric center of the prostate. The distance between the two urethras was measured. The deviation was evaluated at the base, middle, and apex. To evaluate the dosimetric consequences for the true urethra when using a surrogate urethra, two different dose plans were made: one based on the true urethra and one based on the surrogate urethra. The dose-volume histograms for the true urethra were analyzed.

RESULTS

The deviation between the true urethra and the surrogate urethra was greatest at the base of the prostate. A statistically significant difference was seen between the dosimetric parameters for the true and the surrogate urethra when the dose plan was made using the surrogate urethra. In this situation the dose to the true urethra was increased above our defined maximum tolerance limit.

CONCLUSIONS

When using dose plans made according to a surrogate urethra the dose to the true urethra might be too high to be acceptable. If the true urethra is not visualized, severe damage could easily develop in a significant number of patients.

Comparison of urethral diameters for calculating the urethral dose after permanent prostate brachytherapy

PURPOSE

No studies have yet evaluated the effects of a dosimetric analysis for different urethral volumes. We therefore evaluated the effects of a dosimetric analysis to determine the different urethral volumes.

METHODS

This study was based on computed tomography/magnetic resonance imaging (CT/MRI) combined findings in 30 patients who had undergone prostate brachytherapy. Postimplant CT/MRI scans were performed 30 days after the implant. The urethra was contoured based on its diameter (8, 6, 4, 2, and 0 mm). The total urethral volume-in cubic centimeters [UrV150/200(cc)] and percent (UrV150%/200%), of the urethra receiving 150% or 200% of the prescribed dose-and the doses (UrD90/30/5) in Grays to 90%, 30%, and 5% of the urethral volume were measured based on the urethral diameters.

RESULTS

The UrV150(cc) and UrD30 were statistically different between the of 8-, 6-, 4-, 2-, and 0-mm diameters, whereas the UrD5 was statistically different only between the 8-, 6-, and 4-mm diameters. Especially for UrD5, there was an approximately 40-Gy difference between the mean values for the 8- and 0-mm diameters.

CONCLUSION

We recommend that the urethra should be contoured as a 4- to 6-mm diameter circle or one side of a triangle of 5-7 mm. By standardizing the urethral diameter, the urethral dose will be less affected by the total urethral volume.

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.

A simple technique for determining accurate urethral dosimetry after seed brachytherapy for prostate cancer

PURPOSE

To describe a simple technique to define the anatomically accurate urethral location in the postimplant CT scans, after permanent prostate seed implants, without the discomfort associated with use of a catheter.

METHODS AND MATERIALS

We perform preplanned, preloaded transperineal transrectal ultrasound-guided permanent seed implants for men with low-risk prostate cancer. In postimplant CT scans performed 4 weeks after the procedure we previously used a catheter to identify the urethra. We now use retrograde injection of contrast, followed by the retrograde injection of a mixture of contrast and aerated sterile lubricant jelly to opacify the urethra on our CT scans.

RESULTS

This technique is economical, simple, and more comfortable than the use of a catheter. It reliably allows identification of the urethra for the purposes of deriving dose-volume histogram statistics, for quality control. It provides a reference for more accurate determination of the prostate apex.

CONCLUSIONS

We recommend this technique to those performing prostate seed implants wishing to most accurately determine the precise urethral dose parameters in delayed postimplant CT scans, without the need for the discomfort associated with a urethral catheter.

Changes in the tumor microenvironment during low-dose-rate permanent seed implantation iodine-125 brachytherapy

PURPOSE

There is a lack of data regarding how the tumor microenvironment (e.g., perfusion and oxygen partial pressure [pO2]) changes in response to low-dose-rate (LDR) brachytherapy. This may be why some clinical issues remain unresolved, such as the appropriate use of adjuvant external beam radiation therapy (EBRT). The purpose of this work was to obtain some basic preclinical data on how the tumor microenvironment evolves in response to LDR brachytherapy.

METHODS AND MATERIALS

In an experimental mouse tumor, pO2 (measured by electron paramagnetic resonance) and perfusion (measured by dynamic contrast-enhanced magnetic resonance imaging) were monitored as a function of time (0-6 days) and distance (0-2 mm and 2-4 mm) from an implanted 0.5 mCi iodine-125 brachytherapy seed.

RESULTS

For most of the experiments, including controls, tumors remained hypoxic at all times. At distances of 2-4 mm from radioactive seeds ( approximately 1.5 Gy/day), however, there was an early, significant increase in pO2 within 24 h. The pO2 in that region remained elevated through Day 3. Additionally, the perfusion in that region was significantly higher than for controls starting at Day 3.

CONCLUSION

It may be advantageous to give adjuvant EBRT shortly (approximately 1 to 2 days) after commencement of clinical LDR brachytherapy, when the pO2 in the spatial regions between seeds should be elevated. If chemotherapy is given adjuvantly, it may best be administered just a little later (approximately 3 or 4 days) after the start of LDR brachytherapy, when perfusion should be elevated.

Critical organ dosimetry in permanent seed prostate brachytherapy: Defining the organs at risk

PURPOSE

Although permanent seed prostate brachytherapy is associated with a low risk of serious morbidity, proctitis and prolonged irritative and obstructive urinary symptoms may occur. Data are accumulating to help establish thresholds or guidelines for minimizing toxicity, however, no uniform method of defining and calculating the dose to critical organs currently exists. We set out to examine the existing data and propose a uniform method of reporting such that results from different centers can more easily be compared.

METHODS AND MATERIALS

In preparation for a panel discussion at the American Brachytherapy Society 2004 Annual Meeting, four members with expertise in prostate dosimetry and critical organ assessment performed a literature search and, supplemented with their clinical experience, formulated a proposal for defining and reporting dose in a standardized fashion to the critical organs for permanent seed prostate brachytherapy.

RESULTS

As previously recommended by the American Brachytherapy Society, postimplant dosimetry should be performed on all patients undergoing permanent prostate brachytherapy. The standard imaging for postplan assessment is the CT scan. The interval between seed implantation and postplan assessment should be reported. For rectal and urinary morbidities, the critical organs are considered to be the anterior rectum and the prostatic urethra, respectively. For erectile dysfunction, both the neurovascular bundle and penile bulb have been implicated. The rectum should be contoured on all CT scan slices where radioactive seeds are visible. Both the inner and outer walls should be contoured. The dose should be reported as RV100 and RV150, the volumes in cubic centimeters of the rectal wall receiving 100% and 150% of the prescribed dose, respectively. The urethra should be contoured as a structure on each slice where seeds can be seen. The urethra should be identified by either catheterization or fusion with transrectal ultrasound. The dose should be reported as UrD5 and UrD30, which are, respectively, the dose to 5% and 30% of the urethra in Gray. As well, a UrV150 should be reported, which is the volume in cubic centimeters of the urethra receiving 150% of the prescribed dose. No recommendations can be made at this time for reporting neurovascular bundle or penile bulb doses.

CONCLUSIONS

It is essential that toxicity data be collected and reported in a uniform fashion. Thus, the critical organs for toxicity must be defined and the corresponding dosimetry reported in a standard fashion such that guidelines can be established in the future based on data from a cross-section of centers.

Image guided I125 prostate brachytherapy with Hybrid Interactive Mick technique in the community setting: How does it compare?

The aim of this study is to evaluate the target coverage, procedural techniques, and merits of Hybrid Interactive Mick (HIM) I125 transperineal permanent implantation (TPPI) of the prostate performed with 10 urologists in a community hospital. Detailed day 0 post-implant dosimetric evaluations of TPPI procedures were performed on 333 consecutive monotherapy patients treated between September 2000 and November 2003 at a single institution. All patients underwent TPPI with HIM. Pelvic and CXR films were obtained for a manual seed count at day 0 and again > day 90 on 175 patients. The HIM-prostate brachytherapy performed in a community hospital provided median D(90), V100, and V150 values of 157Gy, 94%, and 42.3%, respectively. 18% of patients had seed migration to the lungs while 2% had seed migration to the bladder. Only 7 patients (4%) had 2 or more seeds migrate to the lungs. Procedure times average 38 minutes and number of needles used averaged 18. The post-implant urinary retention rate was 2.1% Use of HIM-prostate brachytherapy in the community setting with multiple urologists reproducibly maintained excellent and consistent dosimetric coverage. Procedure times and number of needles used were minimized, and with careful attention to image-guided technique, seed migration to bladder and lung was also minimized.

Factors predicting for urinary incontinence after prostate brachytherapy

PURPOSE

To define risk factors that predict for urinary incontinence after (125)I prostate brachytherapy.

METHODS AND MATERIALS

Urinary incontinence after (125)I prostate brachytherapy was evaluated using a patient self-assessment questionnaire based on the NCI Common Toxicity Criteria (version 2). Grade 0 is defined as no incontinence; Grade 1 incontinence occurs with coughing, sneezing, or laughing; Grade 2 is spontaneous incontinence with some control; and Grade 3 is no control. One hundred fifty-three patients received monotherapy (145 Gy) (125)I implants between October 1996 and December 2001, and 112 (75%) responded to our survey. Median follow-up was 47 months (range, 14-74 months). Patient characteristics included a preimplant prostate-specific antigen < or =10, Gleason score < or =6, and stage < or =T2b. CT-based postimplant dosimetry was analyzed approximately 30 days after the procedure, and dose-volume histograms of the prostate and the prostatic urethra were generated based on contoured volumes. Dosimetric parameters evaluated as predictive factors for incontinence included the prostate volume; total activity implanted; number of needles; number of seeds; seed activity; urethral D(5), D(10), D(25), D(50), D(75), and D(90) doses; prostate D(90) doses; and prostate V(100), V(200), and V(300). Clinical parameters evaluated included age, Gleason score, prostate-specific antigen, preimplant International Prostate Symptom Score (I-PSS), and length of follow-up.

RESULTS

Urethral D(10) dose and preimplant I-PSS predicted for urinary incontinence on multivariate analysis (p = 0.002 and p = 0.003, respectively). Twenty-eight patients reported Grade 1 incontinence (26%), and 5 patients reported Grade 2 (5%). Patients with Grade 1 and 2 incontinence were analyzed together, because of the small number of patients who experienced Grade 2. No patients reported Grade 3 incontinence. Mean urethral D(10) was 314 +/- 78 Gy in patients with Grade 0 compared with 394 +/- 147 Gy in patients with Grades 1, 2 incontinence (p = 0.002). The incidence of incontinence doubled as the urethral D(10) dose increased above 450 Gy. Patients with Grade 0 had a mean preimplant I-PSS score of 6.6 +/- 4.5 compared with 10.0 +/- 6.4 for Grades 1, 2 (p = 0.003). A significant increase in the incidence of incontinence was noted when the preimplant I-PSS was greater than 15. No relationship was noted between incontinence and prostate volume, total activity implanted, or the number of needles used (p = 0.83, p = 0.89, p = 0.36, respectively).

CONCLUSION

Urethral D(10) dose and preimplant I-PSS are predictive for patients at higher risk of urinary incontinence. To decrease the risk of this complication, an effort should be made to keep the urethral D(10) dose as close to the prescribed dose as possible, and the preimplant I-PSS should be thoroughly evaluated in an attempt to select patients with scores less than 15.

Head and neck tumors other than squamous cell carcinoma

PURPOSE OF REVIEW

This review deals with classification and treatment of some rare nonsquamous cell carcinomas of the head and neck.

RECENT FINDINGS

Paranasal sinus tumor classification is under evaluation. Contrary to the past, the recent tendency is to build stage classifications on prognostic factors that mainly reflect limitations for adequate surgery, and not simply on dimensional criteria, which are more frequently used in TNM. Among sinonasal tract tumors new pathologic entities have been described. So far, little is known about their natural history and about the need to use pathologic classification to differentiate treatment. Recent advances in radiotherapeutic techniques, such as intensity-modulated radiotherapy, will probably have an impact on future treatment of paranasal sinus tumors. Several molecular targets (c-kit, HER-2/neu, androgen receptors) have been identified in salivary gland cancer. It is interesting to note that among different histotypes there is a trend toward a consistent expression of specific markers in specific cancers, suggesting a possible implication of them in the disease histogenesis. Not surprisingly these findings prompted clinical research with molecular targeted drugs.

SUMMARY

Nonsquamous cell carcinomas of the head and neck are rare neoplasms. A multidisciplinary team treatment plan is needed, in particular for skull base-located tumors. Salivary gland cancer displays several molecular targets that need to be investigated further.