Palliative radiotherapy for prostate cancer

Radiotherapy is an effective tool for the palliation of symptoms commonly caused by prostate cancer. The majority of painful bone metastases respond equally well to single or multiple fractions of external radiotherapy. Retreatment with a second course of radiation induces pain responses in approximately 50% of patients. For more diffuse metastases, either hemibody radiation or systemic radiopharmaceuticals can reduce pain, and radium-223 is associated with improved survival in men with castration-resistant prostate cancer. Hematuria, bladder outlet obstruction, and rectal compression are all improved with palliative radiotherapy. The ability of stereotactic body radiation therapy to reduce pain compared with standard external radiation is being investigated, as is its role in treating those with limited metastatic disease.

Can electronic web-based technology improve quality of life data collection? Analysis of Radiation Therapy Oncology Group 0828

PURPOSE

Missing data are a significant problem in clinical trials, particularly for quality of life (QOL), which cannot be obtained retrospectively. The purpose of this study was to evaluate the feasibility of an electronic web-based strategy for QOL data collection in a cooperative group radiation oncology trial setting.

METHODS AND MATERIALS

Radiation Therapy Oncology Group (RTOG) 0828 was a prospective National Cancer Institute cooperative group companion study of RTOG-0415, a randomized study of conventional versus hypofractionated radiation. Forty-nine English-speaking patients with favorable risk prostate cancer who enrolled on RTOG-0415 consented to using web-based technology for completing QOL. In RTOG-0415, using paper forms, the 6-month QOL compliance rate was 52%. The purpose of RTOG-0828 was to test the feasibility of a web-based strategy with the goal of increasing the 6-month QOL completion rate by 25% (from 52% to 77%) for a relative improvement of ~50%. The web-based tool used in this study was VisionTree Optimal Care (VTOC; VisionTree Software, Inc, San Diego, CA), a Health-Insurance-Portability-Accountability-Act secure, online technology that allows real-time tracking and e-mail reminders. The primary endpoint was the 6-month compliance rate for the validated QOL instrument, Expanded Prostate Index Composite.

RESULTS

The QOL completion rate at baseline was 98%. Compared with the prior 52% QOL completion rate at 6 months using paper forms, the QOL web-based completion rate at 6 months was 90% (2-sided P value < .001). At 12 months, the EPIC completion rate was 82% (compared with 36% using paper forms).

CONCLUSIONS

This RTOG study suggests that a web-based strategy to collect QOL appears to be feasible in the cooperative group radiation oncology trial setting and is associated with an increase in the 6-month QOL compliance rate compared with the prior method of using paper forms. The RTOG plans to further test this strategy in a head-and-neck cancer trial across all participating RTOG sites.

Single institution's dosimetry and IGRT analysis of prostate SBRT

BACKGROUND AND PURPOSE

To report single institution's IGRT and dosimetry analysis on the 37 Gy/5 fraction prostate SBRT clinical trial.

MATERIALS/METHODS

The IRB (Duke University Medical Center) approved clinical trial has treated 28 patients with stage T1-T2c prostate cancer with a regimen of 37 Gy in 5 fractions using IMRT and IGRT protocols since 2009. The clinical trial protocol requires CT/MRI imaging for the prostate delineation; a margin of 3 mm in posterior direction and 5 mm elsewhere for planning target volume (PTV); and strict dose constraints for primary organs-at-risks (OARs) including the bladder, the rectum, and the femoral heads. Rigid IGRT process is also an essential part of the protocol. Precise patient and prostate positioning and dynamic tracking of prostate motion are performed with electromagnetic localization device (Calypso) and on-board imaging (OBI) system. Initial patient and target alignment is performed based on fiducials with OBI imaging system and Calypso system. Prior to treatment, cone-beam CT (CBCT) is performed for soft tissue alignment verification. During treatment, per-beam corrections for target motion using translational couch movements is performed before irradiating each field, based on electromagnetic localization or on-board imaging localization. Dosimetric analysis on target coverage and OAR sparing is performed based on key DVH parameters corresponding to protocol guidance. IGRT analysis is focused on the average frequency and magnitude of corrections during treatment, and overall intra-fractional target drift. A margin value is derived using actual target motion data and the margin recipe from Van Herk et al., and is compared to the current one in practice. In addition, cumulative doses with and without per-beam IGRT corrections are compared to assess the benefit of online IGRT.

RESULTS

1. No deviation has been found in 10 of 14 dosimetric constraints, with minor deviations in the rest 4 constraints.2. Online IGRT techniques including Calypso, OBI and CBCT supplement each other to create an effective and reliable system on tracking target and correcting intra-fractional motion.3. On average ½ corrections have been performed per fraction, with magnitude of (0.22 ± 0.11) cm. Average target drift magnitude is (0.7 ± 1.3) mm in one direction during each fraction.4. Benefit from per-beam correction in overall review is small: most differences from no correction are < 0.1 Gy for PTV D1cc/Dmean and < 1%/1.5 cc for OAR parameters. Up to 1.5 Gy reduction was seen in PTV D99% without online correction. Largest differences for OARs are -4.1 cc and +1.6 cc in the V50% for the bladder and the rectum, respectively. However, online IGRT helps to catch unexpected significant target motion.5. Margin derived from actual target motion is 2.5 mm isotropic, consist with current practice.

CONCLUSIONS

Clinical experience of the 37 Gy/5-fraction prostate SBRT from a single institution is reported. Dosimetric analysis demonstrated excellent target coverage and OAR sparing for our first 28 patients in this trial. Online IGRT techniques implemented are both effective and reliable. Per-beam correction in general provides a small benefit in dosimetry. Target motion measured by online localization devices confirms that current margin selection is adequate.

Development of frequency modulation reflectometer for Korea Superconducting Tokamak Advanced Research tokamak

Frequency modulation reflectometer has been developed to measure the plasma density profile of the Korea Superconducting Tokamak Advanced Research tokamak. Three reflectometers are operating in extraordinary polarization mode in the frequency range of Q band (33.6-54 GHz), V band (48-72 GHz), and W band (72-108 GHz) to measure the density up to 7 × 10(19) m(-3) when the toroidal magnetic field is 2 T on axis. The antenna is installed inside of the vacuum vessel. A new vacuum window is developed by using 50 μm thick mica film and 0.1 mm thick gold gasket. The filter bank of low pass filter, notch filter, and Faraday isolator is used to reject the electron cyclotron heating high power at attenuation of 60 dB. The full frequency band is swept in 20 μs. The mixer output is directly digitized with sampling rate of 100 MSamples/s. The phase is obtained by using wavelet transform. The whole hardware and software system is described in detail and the measured density profile is presented as a result.

Phase 1 trial of neoadjuvant radiation therapy before prostatectomy for high-risk prostate cancer

PURPOSE

To evaluate, in a phase 1 study, the safety of neoadjuvant whole-pelvis radiation therapy (RT) administered immediately before radical prostatectomy in men with high-risk prostate cancer.

METHODS AND MATERIALS

Twelve men enrolled and completed a phase 1 single-institution trial between 2006 and 2010. Eligibility required a previously untreated diagnosis of localized but high-risk prostate cancer. Median follow-up was 46 months (range, 14-74 months). Radiation therapy was dose-escalated in a 3 × 3 design with dose levels of 39.6, 45, 50.4, and 54 Gy. The pelvic lymph nodes were treated up to 45 Gy with any additional dose given to the prostate and seminal vesicles. Radical prostatectomy was performed 4-8 weeks after RT completion. Primary outcome measure was intraoperative and postoperative day-30 morbidity. Secondary measures included late morbidity and oncologic outcomes.

RESULTS

No intraoperative morbidity was seen. Chronic urinary grade 2+ toxicity occurred in 42%; 2 patients (17%) developed a symptomatic urethral stricture requiring dilation. Two-year actuarial biochemical recurrence-free survival was 67% (95% confidence interval 34%-86%). Patients with pT3 or positive surgical margin treated with neoadjuvant RT had a trend for improved biochemical recurrence-free survival compared with a historical cohort with similar adverse factors.

CONCLUSIONS

Neoadjuvant RT is feasible with moderate urinary morbidity. However, oncologic outcomes do not seem to be substantially different from those with selective postoperative RT. If this multimodal approach is further evaluated in a phase 2 setting, 54 Gy should be used in combination with neoadjuvant androgen deprivation therapy to improve biochemical outcomes.

A knowledge-based approach to improving and homogenizing intensity modulated radiation therapy planning quality among treatment centers: an example application to prostate cancer planning

PURPOSE

Intensity modulated radiation therapy (IMRT) treatment planning can have wide variation among different treatment centers. We propose a system to leverage the IMRT planning experience of larger institutions to automatically create high-quality plans for outside clinics. We explore feasibility by generating plans for patient datasets from an outside institution by adapting plans from our institution.

METHODS AND MATERIALS

A knowledge database was created from 132 IMRT treatment plans for prostate cancer at our institution. The outside institution, a community hospital, provided the datasets for 55 prostate cancer cases, including their original treatment plans. For each "query" case from the outside institution, a similar "match" case was identified in the knowledge database, and the match case's plan parameters were then adapted and optimized to the query case by use of a semiautomated approach that required no expert planning knowledge. The plans generated with this knowledge-based approach were compared with the original treatment plans at several dose cutpoints.

RESULTS

Compared with the original plan, the knowledge-based plan had a significantly more homogeneous dose to the planning target volume and a significantly lower maximum dose. The volumes of the rectum, bladder, and femoral heads above all cutpoints were nominally lower for the knowledge-based plan; the reductions were significantly lower for the rectum. In 40% of cases, the knowledge-based plan had overall superior (lower) dose-volume histograms for rectum and bladder; in 54% of cases, the comparison was equivocal; in 6% of cases, the knowledge-based plan was inferior for both bladder and rectum.

CONCLUSIONS

Knowledge-based planning was superior or equivalent to the original plan in 95% of cases. The knowledge-based approach shows promise for homogenizing plan quality by transferring planning expertise from more experienced to less experienced institutions.

Image guidance for post-prostatectomy radiotherapy: Are we missing the mark?

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Background: Image-guided radiation therapy (IGRT) has been widely adopted for both definitive and post-operative prostate radiotherapy. In the postoperative setting, numerous studies of prostate bed motion have recommended tight planning margins (<10mm) if IGRT is used daily. The purpose of this analysis is to determine the effect of IGRT on the efficacy and toxicity of post-operative prostate radiotherapy. Methods: Between 1998 and 2010, 286 patients received radiation therapy after prostatectomy at Duke. Recurrent disease following radiation therapy was defined as PSA >0.2 ng/ml and rising or initiation of salvage ADT. CTCAE v 4.0 and the RTOG/LENT late morbidity scores were used to grade acute and late toxicities. Risk for biochemical failure and late Grade 2+ GI toxicity were compared between IGRT (N = 113) and non-IGRT (N = 173) patients using multivariable adjusted Cox regression controlling for age, treatment technique (3D vs IMRT), radiation dose, androgen suppression, pathologic Gleason Score, margin status, pathologic stage, and pre-radiotherapy PSA level. Results: The median margin size for patients with IGRT was 7mm (IQR 6-10mm) and 15mm (IQR 7-15mm) for those without IGRT (p < 0.001). Median follow up was 21 months (IQR 15-33 mo) for patients with IGRT and 49 months (IQR 30-73 mo) for those without IGRT (p < 0.001). On multivariate analysis, patients treated with IGRT had a greater risk of progression versus non-daily imaging (HR = 2.51, p < 0.001), as did patients who received salvage versus adjuvant radiotherapy (HR = 2.41, p = 0.005). Higher pathologic Gleason Score (HR = 1.96, p = 0.026) and pathologic stage (HR = 1.93, p = 0.003) conferred increased risk of progression, while positive margin status was protective (HR = 0.53, p = 0.002). Age, radiation dose, androgen suppression, and treatment technique did not affect biochemical outcome (p > 0.1). There were no differences in acute or late GI toxicity according to treatment technique or use of IGRT (both p > 0.1). Conclusions: The use of IGRT was associated with increased biochemical recurrence for patients receiving post-operative prostate radiotherapy. For these patients, we recommend using treatment margins of at least 10mm to address subclinical disease and organ motion.

Quantitative analysis of the factors which affect the interpatient organ-at-risk dose sparing variation in IMRT plans

PURPOSE

The authors present an evidence-based approach to quantify the effects of an array of patient anatomical features of the planning target volumes (PTVs) and organs-at-risk (OARs) and their spatial relationships on the interpatient OAR dose sparing variation in intensity modulated radiation therapy (IMRT) plans by learning from a database of high-quality prior plans.

METHODS

The authors formulized the dependence of OAR dose volume histograms (DVHs) on patient anatomical factors into feature models which were learned from prior plans by a stepwise multiple regression method. IMRT plans for 64 prostate, 82 head-and-neck (HN) treatments were used to train the models. Two major groups of anatomical features were considered in this study: the volumetric information and the spatial information. The geometry of OARs relative to PTV is represented by the distance-to-target histogram, DTH. Important anatomical and dosimetric features were extracted from DTH and DVH by principal component analysis. The final models were tested by additional 24 prostate and 24 HN plans.

RESULTS

Significant patient anatomical factors contributing to OAR dose sparing in prostate and HN IMRT plans have been analyzed and identified. They are: the median distance between OAR and PTV, the portion of OAR volume within an OAR specific distance range, and the volumetric factors: the fraction of OAR volume which overlaps with PTV and the portion of OAR volume outside the primary treatment field. Overall, the determination coefficients R(2) for predicting the first principal component score (PCS1) of the OAR DVH by the above factors are above 0.68 for all the OARs and they are more than 0.53 for predicting the second principal component score (PCS2) of the OAR DVHs except brainstem and spinal cord. Thus, the above set of anatomical features combined has captured significant portions of the DVH variations for the OARs in prostate and HN plans. To test how well these features capture the interpatient organ dose sparing variations in general, the DVHs and specific dose-volume indices calculated from the regression models were compared with the actual DVHs and dose-volume indices from each patient's plan in the validation dataset. The dose-volume indices compared were V99%, V85%, and V50% for bladder and rectum in prostate plans and parotids median dose in HN plans. The authors found that for the bladder and rectum models, 17 out of 24 plans (71%) were within 6% OAR volume error and 21 plans (85%) were within 10% error; For the parotids model, the median dose values for 30 parotids out of 48 (63%) were within 6% prescription dose error and the values in 40 parotids (83%) were within 10% error.

CONCLUSIONS

Quantitative analysis of patient anatomical features and their correlation with OAR dose sparing has identified a number of important factors that explain significant amount of interpatient DVH variations in OARs. These factors can be incorporated into evidence-based learning models as effective features to provide patient-specific OAR dose sparing goals.

Radiotherapy following radical prostatectomy

Radiotherapy following radical prostatectomy has been controversial and no consensus has developed on the most appropriate use of radiotherapy after radical prostatectomy. In the last decade the results of three randomized controlled trials examining the effects of early radiotherapy after radical prostatectomy in patients with high-risk features (positive surgical margins, extracapsular extension and seminal vesical involvement) have been published. The results of these trials indicate that early radiotherapy changes the natural history of high-risk prostate cancer. Specifically, early radiotherapy reduces the risk of biochemical recurrence, improves clinical disease-free survival, decreases the utilization of salvage androgen suppression and, in the study with longest follow-up, early radiotherapy improves overall survival. This article will review the evidence, provide a commentary on the existing evidence, and describe key issues going forward (timing of radiotherapy, androgen suppression and radiotherapy techniques).

Evaluation of Adherence to Quality Measures for Prostate Cancer Radiotherapy in the United States: Results from the Quality Research in Radiation Oncology (QRRO) Survey

PURPOSE

To test the feasibility of using proposed quality indicators to assess radiotherapy quality in prostate cancer management based on a 2007 stratified random survey of treating academic and non-academic US institutions.

METHODS AND MATERIALS

414 patients with clinically localized prostate cancer treated with external beam radiotherapy (EBRT) or brachytherapy were selected from 45 institutions. Indicators used as specific measurable clinical performance measures to represent surrogates for quality of radiotherapy delivery included established measures, such as the use of prescription doses ≥75 Gy for intermediate- and high-risk EBRT patients and androgen-deprivation therapy (ADT) in conjunction with EBRT for patients with high-risk disease, and emerging measures, including daily target localization (image-guidance) to correct for organ motion for EBRT patients.

RESULTS

167 patients (47%) were treated with 6 MV photons, 31 (9%) were treated with 10 MV, 65 (18%) received 15 MV, and the remaining 90 (26%) 16-23 MV. For intermediate- plus high-risk patients (n=181), 78% were treated to ≥75 Gy. Among favorable-risk patients, 72% were treated to ≥75 Gy. Among high-risk EBRT patients, 60 (87%) were treated with ADT in conjunction with EBRT and 13% (n=9) with radiotherapy alone. Among low- and intermediate-risk patients, 10% and 42%, respectively, were treated with ADT plus EBRT. For 24% of EBRT patients (85/354), weekly electronic portal imaging was obtained as verification films without daily target localization and the remaining 76% were treated with daily localization of the target using various methods.

CONCLUSIONS

Adherence to defined quality indicators was observed in a majority of patients. ≈90% of high-risk patients are treated with ADT plus EBRT and ≈80% of intermediate- and high-risk patients receive prescription doses >=75 Gy, consistent with the published results of randomized trials.

Synchronized operation by field programmable gate array based signal controller for the Thomson scattering diagnostic system in KSTAR

The Thomson scattering diagnostic system is successfully installed in the Korea Superconducting Tokamak Advanced Research (KSTAR) facility. We got the electron temperature and electron density data for the first time in 2011, 4th campaign using a field programmable gate array (FPGA) based signal control board. It operates as a signal generator, a detector, a controller, and a time measuring device. This board produces two configurable trigger pulses to operate Nd:YAG laser system and receives a laser beam detection signal from a photodiode detector. It allows a trigger pulse to be delivered to a time delay module to make a scattered signal measurement, measuring an asynchronous time value between the KSTAR timing board and the laser system injection signal. All functions are controlled by the embedded processor running on operating system within a single FPGA. It provides Ethernet communication interface and is configured with standard middleware to integrate with KSTAR. This controller has operated for two experimental campaigns including commissioning and performed the reconfiguration of logic designs to accommodate varying experimental situation without hardware rebuilding.