Trans-perineal implantation of radio-opaque treatment verification markers into the prostate: an assessment of procedure related morbidity, patient acceptability and accuracy

Soft-tissue prostate intrafraction motion tracking in 3D cine-MR for MR-guided radiotherapy

To develop a method to automatically determine intrafraction motion of the prostate based on soft tissue contrast on 3D cine-magnetic resonance (MR) images with high spatial and temporal resolution. Twenty-nine patients who underwent prostate stereotactic body radiotherapy (SBRT), with four implanted cylindrical gold fiducial markers (FMs), had cine-MR imaging sessions after each of five weekly fractions. Each cine-MR session consisted of 55 sequentially obtained 3D data sets ('dynamics') and was acquired over an 11 s period, covering a total of 10 min. The prostate was delineated on the first dynamic of every dataset and this delineation was used as the starting position for the soft tissue tracking (SST). Each subsequent dynamic was rigidly aligned to the first dynamic, based on the contrast of the prostate. The obtained translation and rotation describes the intrafraction motion of the prostate. The algorithm was applied to 6270 dynamics over 114 scans of 29 patients and the results were validated by comparing to previously obtained fiducial marker tracking data of the same dataset. Our proposed tracking method was also retro-perspectively applied to cine-MR images acquired during MR-guided radiotherapy of our first prostate patient treated on the MR-Linac. The difference in the 3D translation results between the soft tissue and marker tracking was below 1 mm for 98.2% of the time. The mean translation at 10 min were X: 0.0 [Formula: see text] 0.8 mm, Y: 1.0 [Formula: see text] 1.8 mm and Z: [Formula: see text] mm. The mean rotation results at 10 min were X: [Formula: see text], Y: 0.1 [Formula: see text] 0.6° and Z: 0.0 [Formula: see text] 0.7°. A fast, robust and accurate SST algorithm was developed which obviates the need for FMs during MR-guided prostate radiotherapy. To our knowledge, this is the first data using full 3D cine-MR images for real-time soft tissue prostate tracking, which is validated against previously obtained marker tracking data.

Feasibility of Image Registration for Ultrasound-Guided Prostate Radiotherapy Based on Similarity Measurement by a Convolutional Neural Network

Purpose:

Registration of 3-dimensional ultrasound images poses a challenge for ultrasound-guided radiation therapy of the prostate since ultrasound image content changes significantly with anatomic motion and ultrasound probe position. The purpose of this work is to investigate the feasibility of using a pretrained deep convolutional neural network for similarity measurement in image registration of 3-dimensional transperineal ultrasound prostate images.

Methods:

We propose convolutional neural network-based registration that maximizes a similarity score between 2 identical in size 3-dimensional regions of interest: one encompassing the prostate within a simulation (reference) 3-dimensional ultrasound image and another that sweeps different spatial locations around the expected prostate position within a pretreatment 3-dimensional ultrasound image. The similarity score is calculated by (1) extracting pairs of corresponding 2-dimensional slices (patches) from the regions of interest, (2) providing these pairs as an input to a pretrained convolutional neural network which assigns a similarity score to each pair, and (3) calculating an overall similarity by summing all pairwise scores. The convolutional neural network method was evaluated against ground truth registrations determined by matching implanted fiducial markers visualized in a pretreatment orthogonal pair of x-ray images. The convolutional neural network method was further compared to manual registration and a standard commonly used intensity-based automatic registration approach based on advanced normalized correlation.

Results:

For 83 image pairs from 5 patients, convolutional neural network registration errors were smaller than 5 mm in 81% of the cases. In comparison, manual registration errors were smaller than 5 mm in 61% of the cases and advanced normalized correlation registration errors were smaller than 5 mm only in 25% of the cases.

Conclusion:

Convolutional neural network evaluation against manual registration and an advanced normalized correlation -based registration demonstrated better accuracy and reliability of the convolutional neural network. This suggests that with training on a large data set of transperineal ultrasound prostate images, the convolutional neural network method has potential for robust ultrasound-to-ultrasound registration.

Fiducial markers implantation for prostate image-guided radiotherapy: a report on the transperineal approach

INTRODUCTION

In the external beam prostate cancer radiation therapy, daily gland displacement could lead to a target missing. The use of intra-prostatic gold fiducial markers for daily prostate position verification and correction before and during treatment delivery (image-guided radiotherapy, IGRT) is widely used in the radiation therapy centers to accurately target the prostate. Usually, the fiducial markers are implanted through the rectum, with complications such as infections and rectal bleeding. We report our experience in prostate fiducial markers implantation through a transperineal approach.

PATIENTS AND METHODS

Between September 2011 and January 2018 at our center, 101 patients underwent gold seed fiducial marker transperineal ultrasound-guided implantation for prostate IGRT. We retrospectively reviewed their features and outcome. Twenty-two (21.8%) patients had previously been subjected to a transurethral prostate resection (TURP) for obstructive urinary symptoms because of benign prostatic hypertrophy. No antibiotic prophylaxis was used.

RESULTS

The procedure was well tolerated. In one patient, a single episode of self-limiting urinary bleeding occurred just after it. No other complication was recorded. All the patients, at the evaluation before discharge, reported no pain or dysuria. No rectal bleeding, hematospermia, urinary obstruction or infection were reported in the next days. No markers lost or migration occurred.

DISCUSSION AND CONCLUSION

According to our experience, prostate fiducial markers implantation through a transperineal approach is safe and should be recommended to limit the use of antibiotic therapy and patients morbidity. A previous TURP was not related to a higher risk of loss of seeds.

Transperineal implantation of gold fiducial markers (gold seeds) for prostate image-guided radiation therapy: a feasible technique associated with a low risk of complications

Introduction

The purpose is to describe the method, safety and efficacy of transperineal gold seed placement for image‐guided radiation therapy.

Methods

An ethics committee approved database was used to review records of consecutive patients from October 2008 through December 2013, who underwent transperineal implantation of three gold markers into the prostate using staged local anaesthesia and transrectal ultrasound. Seeds were counted on radiographs from CT simulation, first treatment and last treatment. Retention and use of at least three markers for kV/kV matching was considered a successful implant. A visual analogue scale (VAS) pain assessment was performed. SAS was used for data analysis.

Results

Fiducial marker placement was successful for kV/kV matching in 556/581 patients (95.7%). The procedure was aborted due to pain in two patients. Additional sedation during the procedure was required in two patients. Complications include urinary infections (2 patients, <0.5%) and transient haematuria (2 patients, <0.5%). There were no recorded calls requesting additional pain medication or delays in radiation due to complications. The number of seeds identified at simulation: 4 (2 patients), 3 (554 patients), 2 (21 patients), 1 (1 patient), 0 (1 patient). One patient with three seeds and two patients with <2 seeds had cone beam CT instead of kV/kV imaging for image guidance. No seeds were lost after simulation. The mean visual analogue pain score associated with transperineal gold seed insertion met patients' expectations (respectively 4.1 vs. 4.4 P = 0.19).

Conclusion

Outpatient transperineal insertion of fiducials avoids the rectum, is effective, convenient, well tolerated and has few side effects.

Ultrasound Imaging in Radiation Therapy: From Interfractional to Intrafractional Guidance

External beam radiation therapy (EBRT) is included in the treatment regimen of the majority of cancer patients. With the proliferation of hypofractionated radiotherapy treatment regimens, such as stereotactic body radiation therapy (SBRT), interfractional and intrafractional imaging technologies are becoming increasingly critical to ensure safe and effective treatment delivery. Ultrasound (US)-based image guidance systems offer real-time, markerless, volumetric imaging with excellent soft tissue contrast, overcoming the limitations of traditional X-ray or computed tomography (CT)-based guidance for abdominal and pelvic cancer sites, such as the liver and prostate. Interfractional US guidance systems have been commercially adopted for patient positioning but suffer from systematic positioning errors induced by probe pressure. More recently, several research groups have introduced concepts for intrafractional US guidance systems leveraging robotic probe placement technology and real-time soft tissue tracking software. This paper reviews various commercial and research-level US guidance systems used in radiation therapy, with an emphasis on hardware and software technologies that enable the deployment of US imaging within the radiotherapy environment and workflow. Previously unpublished material on tissue tracking systems and robotic probe manipulators under development by our group is also included.

Review of ultrasound image guidance in external beam radiotherapy: I. Treatment planning and inter-fraction motion management

In modern radiotherapy, verification of the treatment to ensure the target receives the prescribed dose and normal tissues are optimally spared has become essential. Several forms of image guidance are available for this purpose. The most commonly used forms of image guidance are based on kilovolt or megavolt x-ray imaging. Image guidance can also be performed with non-harmful ultrasound (US) waves. This increasingly used technique has the potential to offer both anatomical and functional information.This review presents an overview of the historical and current use of two-dimensional and three-dimensional US imaging for treatment verification in radiotherapy. The US technology and the implementation in the radiotherapy workflow are described. The use of US guidance in the treatment planning process is discussed. The role of US technology in inter-fraction motion monitoring and management is explained, and clinical studies of applications in areas such as the pelvis, abdomen and breast are reviewed. A companion review paper (O'Shea et al 2015 Phys. Med. Biol. submitted) will extensively discuss the use of US imaging for intra-fraction motion quantification and novel applications of US technology to RT.

Calypso® 4D Localization System: a review

Purpose

Calypso® 4D Localization System is a system based on electromagnetic transponders detection enabling precise 3D localisation and continuous tracking of tumour target. This review intended to provide information in order to (1) show how Calypso® 4D Localization System works, (2) to present advantages and disadvantages of this system, (3) to gather information from several clinical studies and, finally, (4) to refer Calypso® System as a tool in dynamic multileaf collimator studies for target motion compensation.

Methods

A structured search was carried out on B-On platform. The key words used in this research were ‘Calypso’, ‘Transponder’, ‘Electromagnetic Localization’, ‘Electromagnetic Tracking’, ‘Target Localization’, ‘Intrafraction Motion’ and ‘DMLC’.

Review

Treatment the implanted transponders are excited by an electromagnetic field and resonate back. These frequencies are detected and Calypso® software calculates the position of the transponders. If the movement detected is larger than the limits previously defined, irradiation can be stopped. The system has been proven to be submillimetre accurate.

Discussion

Calypso® System has been presented as an accurate tool in prostate radiotherapy treatments. The application of this system to other clinical sites is being developed.

Conclusion

The Calypso® System allows real-time localisation and monitoring of the target, without additional ionising radiation administration. It has been a very useful tool in prostate cancer treatment.

Postprostatectomy ultrasound-guided transrectal implantation of gold markers for external beam radiotherapy. Technique and complications rate

BACKGROUND AND PURPOSE

Postprostatectomy radiotherapy (RT) improves survival in adjuvant and salvage settings. The implantation technique and complications rate of gold markers in the prostate bed for high-precision RT were analyzed.

PATIENTS AND METHODS

Patients undergoing postprostatectomy RT for prostate-specific antigen (PSA) relapse or high-risk disease were enrolled in the study. Under transrectal ultrasound guidance, three fine gold markers were implanted in the prostate bed and the technical difficulties of insertion were documented. Patients received our self-designed questionnaires concerning complications and pain. The influence of anticoagulants and coumarins on bleeding was analyzed, as was the effect of potential risk factors on pain.

RESULTS

In 77 consecutive patients, failure of marker implantation or marker migration was seen in six cases. Rectal bleeding was reported by 10 patients and 1 had voiding complaints. No macroscopic hematuria persisting for more than 3 days was observed. Other complications included rectal discomfort (n = 2), nausea (n = 1), abdominal discomfort (n = 1), and pain requiring analgesics (n = 4). No major complications were reported. On a 0-10 visual analogue scale (VAS), the mean pain score was 3.7. No clinically significant risk factors for complications were identified.

CONCLUSION

Transrectal implantation of gold markers in the prostate bed is feasible and safe. Alternatives like cone beam computed tomography (CBCT) should be considered, but the advantages of gold marker implantation for high-precision postprostatectomy RT would seem to outweigh the minor risks involved.

Interfraction rotation of the prostate as evaluated by kilovoltage X-ray fiducial marker imaging in intensity-modulated radiotherapy of localized prostate cancer

To quantify the daily rotation of the prostate during a radiotherapy course using stereoscopic kilovoltage (kV) x-ray imaging and intraprostatic fiducials for localization and positioning correction. From 2005 to 2009, radio-opaque fiducial markers were inserted into 38 patients via perineum into the prostate. The ExacTrac/Novalis Body X-ray 6-day image acquisition system (ET/NB; BrainLab AG, Feldkirchen, Germany) was used to determine and correct the target position. During the first period in 10 patients we recorded all rotation errors but used only Y (table) for correction. For the next 28 patients we used for correction all rotational coordinates, i.e., in addition Z (superior-inferior [SI] or roll) and X (left-right [LR] or tilt/pitch) according to the fiducial marker position by use of the Robotic Tilt Module and Varian Exact Couch. Rotation correction was applied above a threshold of 1° displacement. The systematic and random errors were specified. Overall, 993 software-assisted rotational corrections were performed. The interfraction rotation errors of the prostate as assessed from the radiodense surrogate markers around the three axes Y, Z, and X were on average 0.09, -0.52, and -0.01° with standard deviations of 2.01, 2.30, and 3.95°, respectively. The systematic uncertainty per patient for prostate rotation was estimated with 2.30, 1.56, and 4.13° and the mean random components with 1.81, 2.02, and 3.09°. The largest rotational errors occurred around the X-axis (pitch), but without preferring a certain orientation. Although the error around Z (roll) can be compensated on average by a transformation with 4 coordinates, a significant error around X remains and advocates the full correction with 6 coordinates. Rotational errors as assessed via daily stereoscopic online imaging are significant and dominate around X. Rotation possibly degrades the dosimetric coverage of the target volume and may require suitable strategies for correction.

Patient-reported complications from fiducial marker implantation for prostate image-guided radiotherapy

OBJECTIVES

To report on complications from transrectal ultrasound-guided insertion of fiducial markers for prostate image-guided radiotherapy.

METHODS

234 patients who underwent transrectal fiducial marker insertion for prostate cancer image-guided radiotherapy were assessed retrospectively by questionnaire with regard to the duration and severity of eight symptoms experienced following the procedure. Pain during the implantation procedure was assessed according to the Wong-Baker faces pain scale.

RESULTS

Of 234 patients, 32% had at least one new symptom after the procedure. The commonest new symptom following the procedure was urinary frequency affecting 16% of patients who had not been troubled by frequency beforehand. Haematuria, rectal bleeding, dysuria and haematospermia affected 9-13% of patients, mostly at Grade 1 or 2. Pain, obstruction, and fever and shivers affected 3-4% of patients. Grade 3 rectal bleeding, haematuria, fever and shivers, and urinary frequency affected 0.5-1.5% of patients. Only one patient had a Grade 4 complication (i.e. fever and shivers). Overall, 9% of patients had symptoms lasting more than 2 weeks. The commonest symptoms that lasted more than 2 weeks were frequency, dysuria, obstructive symptoms and rectal bleeding. Mean pain score during the procedure was 1.1 (range 0-5).

CONCLUSION

Transrectal ultrasound-guided fiducial marker insertion for image-guided radiotherapy is well tolerated in the majority of prostate cancer patients. Most symptoms were Grade 1 or 2 in severity. Symptoms in the majority of patients last under 2 weeks. The most serious complication was sepsis in our study.

Six-Dimensional Correction of Intra-Fractional Prostate Motion with CyberKnife Stereotactic Body Radiation Therapy

Large fraction radiation therapy offers a shorter course of treatment and radiobiological advantages for prostate cancer treatment. The CyberKnife is an attractive technology for delivering large fraction doses based on the ability to deliver highly conformal radiation therapy to moving targets. In addition to intra-fractional translational motion (left-right, superior-inferior, and anterior-posterior), prostate rotation (pitch, roll, and yaw) can increase geographical miss risk. We describe our experience with six-dimensional (6D) intra-fraction prostate motion correction using CyberKnife stereotactic body radiation therapy (SBRT). Eighty-eight patients were treated by SBRT alone or with supplemental external radiation therapy. Trans-perineal placement of four gold fiducials within the prostate accommodated X-ray guided prostate localization and beam adjustment. Fiducial separation and non-overlapping positioning permitted the orthogonal imaging required for 6D tracking. Fiducial placement accuracy was assessed using the CyberKnife fiducial extraction algorithm. Acute toxicities were assessed using Common Toxicity Criteria v3. There were no Grade 3, or higher, complications and acute morbidity was minimal. Ninety-eight percent of patients completed treatment employing 6D prostate motion tracking with intra-fractional beam correction. Suboptimal fiducial placement limited treatment to 3D tracking in two patients. Our experience may guide others in performing 6D correction of prostate motion with CyberKnife SBRT.

Clinical results from first use of prostate stent as fiducial for radiotherapy of prostate cancer

PURPOSE

A clinical feasibility study using a removable prostate stent as fiducial for image-guided radiotherapy (IGRT) of localized prostate cancer (PC).

MATERIAL AND METHODS

The study included patients with local or locally advanced PC. The clinical target volume (CTV) was outlined on magnetic resonance (MR) images co-registered to planning computer tomography (CT) images. Daily online IGRT was delivered using the stent as fiducial. Risk of migration was estimated using multiple MR. Acute urinary toxicity was scored using the international prostate symptom score (IPSS). Late gastro-intestinal (GI) and genito-urinary (GU) toxicity was scored using the Radio Therapy Oncology Group (RTOG) score, biochemical failure (BF) was defined as an elevation of prostate specific antigen (PSA) above nadir plus 2 ng/ml after radiotherapy.

RESULTS

One hundred men were enrolled in the study. Ninety completed radiotherapy with the stent as fiducial. No migration of the stent was seen, but three cases of dislocation of the stent to the bladder were observed. Acute urinary toxicity based on IPSS was comparable to toxicity in patients who had gold markers (GM) as fiducials. Removal of the stent was associated with a high frequency of urinary retention. Late GI and GU toxicity and BF were comparable to those of other studies, but longer observation time is needed.

CONCLUSIONS

This study reports the first clinical results of using a prostate stent as fiducial. No migration of the stent observed. Dislocation of the stent to the urinary bladder was observed in three cases, requiring removal of the stent and insertion of a new fiducial. Acute toxicity during radiotherapy evaluated from IPSS was comparable to toxicity in patients with GM. Removal of the stent was associated with a high frequency of post procedural urinary retention. Late toxicity and BF were comparable to those of other studies, though longer observation time is needed.

Residual translational and rotational errors after kV X-ray image-guided correction of prostate location using implanted fiducials

PURPOSE

To evaluate the residual errors and required safety margins after stereoscopic kilovoltage (kV) X-ray target localization of the prostate in image-guided radiotherapy (IGRT) using internal fiducials.

PATIENTS AND METHODS

Radiopaque fiducial markers (FMs) have been inserted into the prostate in a cohort of 33 patients. The ExacTrac/Novalis Body™ X-ray 6d image acquisition system (BrainLAB AG, Feldkirchen, Germany) was used. Corrections were performed in left-right (LR), anterior-posterior (AP), and superior-inferior (SI) direction. Rotational errors around LR (x-axis), AP (y) and SI (z) have been recorded for the first series of nine patients, and since 2007 for the subsequent 24 patients in addition corrected in each fraction by using the Robotic Tilt Module™ and Varian Exact Couch™. After positioning, a second set of X-ray images was acquired for verification purposes. Residual errors were registered and again corrected.

RESULTS

Standard deviations (SD) of residual translational random errors in LR, AP, and SI coordinates were 1.3, 1.7, and 2.2 mm. Residual random rotation errors were found for lateral (around x, tilt), vertical (around y, table), and longitudinal (around z, roll) and of 3.2°, 1.8°, and 1.5°. Planning target volume (PTV)-clinical target volume (CTV) margins were calculated in LR, AP, and SI direction to 2.3, 3.0, and 3.7 mm. After a second repositioning, the margins could be reduced to 1.8, 2.1, and 1.8 mm.

CONCLUSION

On the basis of the residual setup error measurements, the margin required after one to two online X-ray corrections for the patients enrolled in this study would be at minimum 2 mm. The contribution of intrafractional motion to residual random errors has to be evaluated.

Potentials of on-line repositioning based on implanted fiducial markers and electronic portal imaging in prostate cancer radiotherapy

Background

To evaluate the benefit of an on-line correction protocol based on implanted markers and weekly portal imaging in external beam radiotherapy of prostate cancer. To compare the use of bony anatomy versus implanted markers for calculation of setup-error plus/minus prostate movement. To estimate the error reduction (and the corresponding margin reduction) by reducing the total error to 3 mm once a week, three times per week or every treatment day.

Methods

23 patients had three to five, 2.5 mm Ø spherical gold markers transrectally inserted into the prostate before radiotherapy. Verification and correction of treatment position by analysis of orthogonal portal images was performed on a weekly basis. We registered with respect to the bony contours (setup error) and to the marker position (prostate motion) and determined the total error. The systematic and random errors are specified. Positioning correction was applied with a threshold of 5 mm displacement.

Results

The systematic error (1 standard deviation [SD]) in left-right (LR), superior-inferior (SI) and anterior-posterior (AP) direction contributes for the setup 1.6 mm, 2.1 mm and 2.4 mm and for prostate motion 1.1 mm, 1.9 mm and 2.3 mm. The random error (1 SD) in LR, SI and AP direction amounts for the setup 2.3 mm, 2.7 mm and 2.7 mm and for motion 1.4 mm, 2.3 mm and 2.7 mm. The resulting total error suggests margins of 7.0 mm (LR), 9.5 mm (SI) and 9.5 mm (AP) between clinical target volume (CTV) and planning target volume (PTV). After correction once a week the margins were lowered to 6.7, 8.2 and 8.7 mm and furthermore down to 4.9, 5.1 and 4.8 mm after correcting every treatment day.

Conclusion

Prostate movement relative to adjacent bony anatomy is significant and contributes substantially to the target position variability. Performing on-line setup correction using implanted radioopaque markers and megavoltage radiography results in reduced treatment margins depending on the online imaging protocol (once a week or more frequently).

Globalization of the Radiation Therapy Oncology Group: implementation of a model for service expansion and public health improvement

The Radiation Therapy Oncology Group (RTOG) is part of the cooperative group network that is overseen by the National Cancer Institute (NCI). Although the NCI is a US-based group, it has empowered the cooperative groups to recruit foreign institutions to participate in collaborative clinical trials. The RTOG undertook the challenge of globalizing its efforts in 2004. This article describes the rationale for this decision and the tactics adopted by the first hospital outside of North America to enroll patients onto RTOG trials. The challenges confronted by foreign institutions seeking admission to the RTOG and the mechanism by which Tel Aviv Medical Center (TAMC) met these challenges are described. Shortly after its acceptance, TAMC emerged as one of the leading accruers of patients to RTOG studies. The public health implications of this accomplishment are discussed.

A comparison of the use of bony anatomy and internal markers for offline verification and an evaluation of the potential benefit of online and offline verification protocols for prostate radiotherapy

PURPOSE

To evaluate the utility of intraprostatic markers in the treatment verification of prostate cancer radiotherapy. Specific aims were: to compare the effectiveness of offline correction protocols, either using gold markers or bony anatomy; to estimate the potential benefit of online correction protocol's using gold markers; to determine the presence and effect of intrafraction motion.

METHODS AND MATERIALS

Thirty patients with three gold markers inserted had pretreatment and posttreatment images acquired and were treated using an offline correction protocol and gold markers. Retrospectively, an offline protocol was applied using bony anatomy and an online protocol using gold markers.

RESULTS

The systematic errors were reduced from 1.3, 1.9, and 2.5 mm to 1.1, 1.1, and 1.5 mm in the right-left (RL), superoinferior (SI), and anteroposterior (AP) directions, respectively, using the offline correction protocol and gold markers instead of bony anatomy. The subsequent decrease in margins was 1.7, 3.3, and 4 mm in the RL, SI, and AP directions, respectively. An offline correction protocol combined with an online correction protocol in the first four fractions reduced random errors further to 0.9, 1.1, and 1.0 mm in the RL, SI, and AP directions, respectively. A daily online protocol reduced all errors to <1 mm. Intrafraction motion had greater impact on the effectiveness of the online protocol than the offline protocols.

CONCLUSIONS

An offline protocol using gold markers is effective in reducing the systematic error. The value of online protocols is reduced by intrafraction motion.

Ultrasound-Guided Transrectal Implantation of Gold Markers for Prostate Localization During External Beam Radiotherapy: Complication Rate and Risk Factors

PURPOSE

To report the complication rate and risk factors of transrectally implanted gold markers, used for prostate position verification and correction procedures.

METHODS AND MATERIALS

In 209 consecutive men with localized prostate cancer, four gold markers (1 x 7 mm) were inserted under ultrasound guidance in an outpatient setting, and the toxicity was analyzed. All patients received a questionnaire regarding complications after marker implantation. The complications and risk factors were further evaluated by reviewing the medical charts.

RESULTS

Of the 209 men, 13 (6.2%) had a moderate complication, consisting of pain and fever that resolved after treatment with oral medication. In 1.9% of the men, minor voiding complaints were observed. Other minor transient complications, defined as hematuria lasting >3 days, hematospermia, and rectal bleeding, occurred in 3.8%, 18.5%, and 9.1% of the patients, respectively. These complications were seen more often in patients with advanced tumor stage, younger age, and shorter duration of hormonal therapy.

CONCLUSION

Transrectal gold marker implantation for high-precision prostate radiotherapy is a safe and well-tolerated procedure.

Imaging and alignment for image-guided radiation therapy

Image-guided radiation therapy is an exciting new area that focuses heavily on the potential benefit of advanced imaging and image registration to improve precision, thus limiting morbidity and potentially allowing for safe delivery of increased dose. This review explores the issues surrounding the use of imaging and image registration for treatment planning and verification, with emphasis on the underlying patient model and alignment algorithms.

3-D Conformal radiotherapy of localized prostate cancer within an Austrian-German multicenter trial: a prospective study of patients' acceptance of the rectal balloon during treatment

PURPOSE

Patients with localized prostate cancer are treated with 3D radiotherapy using a rectal balloon catheter for internal immobilization of the prostate, thereby reducing the radiation dose to the dorsal rectal wall. The purpose of the study was to investigate clinical feasibility and the influence of acute rectal side effects and pre-existing hemorrhoids on patients' acceptance of the rectal balloon catheter.

METHODS AND MATERIALS

442 patients who underwent primary radiation therapy for localized prostate cancer were included in this prospective Austrian-German multicenter trial. The total radiation dose was either 70 Gy or 74 Gy. Acute rectal side effects were documented using the EORTC/RTOG grading score (European Organisation for Research and Treatment of Cancer/Radiation Therapy 225 Oncology Group) at weeks 2, 4 and 7 of radiation treatment. Within the same time intervals patients were interviewed about their tolerance of the rectal balloon catheter, evaluating five categories of acceptance (1 = no major complaints, 2 = pain at/during application, 3 = signs of blood at the balloon catheter after application but without any pain, 4 = signs of blood at the balloon catheter after application and pain, 5 = balloon application had to be stopped). Voluntary rectoscopy prior to radiotherapy was performed in 310 patients.

RESULTS

429/442 patients (97 %) were treated with the balloon catheter. No major complaints were reported in 79 % of the patients and no acute rectal side effects were seen in 52 % of the patients. Grade 1 side effects were seen in 31 % patients, Grade 2 in 17 % and Grade 3 in 0.5 %. Balloon use had to be stopped in only 4 % of the patients. There was significant correlation between balloon discomfort and rectal side effects (p < 0.01). The presence of hemorrhoids in 36 % patients prior to irradiation had no influence on balloon tolerance.

CONCLUSIONS

The rectal balloon can be used in 3D radiotherapy of localized prostate cancer with a high degree of acceptance by the patients. Use of the balloon is safe within daily clinical treatment. Patients reporting acute rectal side effects experienced significantly more balloon discomfort, but the presence of hemorrhoids was not found to influence acceptance of the balloon.

Clinical application of a repositioning scheme, using gold markers and electronic portal imaging

BACKGROUND AND PURPOSE

To implement an on-line correction scheme based on implanted markers to reduce treatment margins in external beam radiation therapy (EBRT) of carcinoma of the prostate. In turn reduction in treatment margins reduces irradiated volumes and offers the possibility of reduced normal tissue complications or escalated target dose.

PATIENTS AND METHODS

Five or six gold markers were implanted in 10 patients treated for prostate carcinoma using EBRT. All patients were enlisted in an IRB-approved protocol. Before each fraction two portal images were obtained using a low dose (2MU). Positions of the markers were calculated from these images using an in-house developed program. Corrections were applied with a threshold of 2mm displacement. After correction the procedure was repeated.

RESULTS

Overall systematic errors were reduced from 7.45, 1.29, and 5.12 mm to 0.65, 0.11, and 0.46 mm in, respectively, the antero-posterior, lateral, and cranio-caudal directions. Likewise, the overall SD were reduced from 5.99, 5.34, and 4.44 mm to 2.82, 2.64, and 2.22 mm, respectively. All reductions were highly significant (P < 0.01) using a t-test for systematic and an F-test for random errors. On an individual level all but three patients showed significant improvements in all directions for the random errors. All patients improved in at least one direction. Systematic errors were significantly lower in all patients. Simulated correction schemes using this data suggest that margin reduction using off-line reduction does not benefit substantially from on-line corrections in the first few fractions.

CONCLUSIONS

Use of marker-based correction improves the patient position. Factors influencing the accuracy were: (1) number of seeds usable for correction, (2) distribution of markers throughout the volume of interest, and (3) objective instructions for patient realignment.

Radiotherapeutic techniques for prostate cancer, dose escalation and brachytherapy

There is evidence to confirm a dose-response relationship in prostate cancer. The relative benefit is dependent on the clinical prognostic risk factors (T stage, Gleason score and presenting prostate-specific antigen [PSA]) being more favourable for intermediate-risk patients. Refinement of prognostic groups and clinical threshold parameters is ongoing. Escalation of dose in prostate radiotherapy using conventional techniques is limited by rectal tolerance. Substantial advances have been made in radiotherapy practice, such as the development of conformal radiotherapy (CFRT) and intensity-modulated radiotherapy (IMRT). Randomised data support the value of CFRT in reducing rectal toxicity. IMRT can permit higher-dose escalation while still respecting known rectal tolerance thresholds. Brachytherapy is a recognised alternative for low-risk prostate cancer subgroups. New radiotherapeutic strategies for prostate cancer include pelvic nodal irradiation, exploiting the presumed low alpha/beta ratio in prostate cancer for hypofractionation and combining external beam with high-dose-rate brachytherapy boosts. New image-guided methodologies will enhance the therapeutic ratio of any radiotherapy technique or dose escalation programme by enabling more reliable and accurate treatment delivery for improved patient outcomes.