Simultaneous integrated boost of biopsy proven, MRI defined dominant intra-prostatic lesions to 95 Gray with IMRT: early results of a phase I NCI study

Focal Boost in Prostate Cancer Radiotherapy: A Review of Planning Studies and Clinical Trials

BACKGROUND

Focal boost radiotherapy was developed to deliver elevated doses to functional sub-volumes within a target. Such a technique was hypothesized to improve treatment outcomes without increasing toxicity in prostate cancer treatment.

PURPOSE

To summarize and evaluate the efficacy and variability of focal boost radiotherapy by reviewing focal boost planning studies and clinical trials that have been published in the last ten years.

METHODS

Published reports of focal boost radiotherapy, that specifically incorporate dose escalation to intra-prostatic lesions (IPLs), were reviewed and summarized. Correlations between acute/late ≥G2 genitourinary (GU) or gastrointestinal (GI) toxicity and clinical factors were determined by a meta-analysis.

RESULTS

By reviewing and summarizing 34 planning studies and 35 trials, a significant dose escalation to the GTV and thus higher tumor control of focal boost radiotherapy were reported consistently by all reviewed studies. Reviewed trials reported a not significant difference in toxicity between focal boost and conventional radiotherapy. Acute ≥G2 GU and late ≥G2 GI toxicities were reported the most and least prevalent, respectively, and a negative correlation was found between the rate of toxicity and proportion of low-risk or intermediate-risk patients in the cohort.

CONCLUSION

Focal boost prostate cancer radiotherapy has the potential to be a new standard of care.

Local Failure after Prostate SBRT Predominantly Occurs in the PI-RADS 4 or 5 Dominant Intraprostatic Lesion

BACKGROUND

A positive post-treatment prostate biopsy following definitive radiotherapy carries significant prognostic implications.

OBJECTIVE

To determine whether local recurrences after prostate stereotactic body radiation therapy (SBRT) are associated with the presence of and occur more commonly within the region of a PI-RADS 4 or 5 dominant intra-prostatic lesion (DIL) identified on pre-treatment multi-parametric magnetic resonance imaging (MRI).

DESIGN, SETTING, AND PARTICIPANTS

247 patients with localized prostate cancer treated with SBRT at our institution from 2009-2018 underwent post-treatment biopsies (median time to biopsy: 2.2 years) to evaluate local control.

INTERVENTIONS

Prostate SBRT (median 40 Gy in 5 fractions).

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

MRIs were read by a single diagnostic radiologist blinded to other patient characteristics and treatment outcomes. The DIL presence, size, location, and extent were then analyzed to determine associations with the post-treatment biopsy outcomes.

RESULTS AND LIMITATIONS

Among patients who underwent post-treatment biopsies, 39/247 (15.8%) were positive for Gleason-gradable prostate adenocarcinoma, of which 35/39 (90%) had a DIL initially present and 29/39 (74.4%) had a positive biopsy within the DIL. Factors independently associated with post-treatment biopsy outcomes included the presence of a DIL (OR 6.95; p = 0.001), radiographic T3 disease (OR 5.23, p < 0.001), SBRT dose ≥40 Gy (OR 0.26, p = 0.003), and use of androgen deprivation therapy (ADT; OR 0.28, p = 0.027). Among patients with a DIL (N = 149), the only factors associated with post-treatment biopsy outcomes included ≥50% percent cores positive (OR 2.4, p = 0.037), radiographic T3 disease (OR 4.04, p = 0.001), SBRT dose ≥40 Gy (OR 0.22, p < 0.001), and use of ADT (OR 0.21, p = 0.014).

CONCLUSIONS

Our results suggest that men with PI-RADS 4 or 5 DILs have a higher risk of local recurrence after prostate SBRT and that most recurrences are located within the DIL.

PATIENT SUMMARY

We found the presence of a dominant tumor on pre-treatment MRI was strongly associated with residual cancer within the prostate after SBRT and that most recurrences were within the dominant tumor.

Proton vs. photon radiotherapy for MR-guided dose escalation of intraprostatic lesions

BACKGROUND

Dose escalation has been associated with improved biochemical control for prostate cancer. Focusing the high dose on the MRI-defined intraprostatic lesions (IL) could spare the surrounding organs at risk and hence allow further escalation. We compare treatment efficacy between state-of-the-art focally-boosted proton and photon-based radiotherapy, and investigate possible predictive guidelines regarding individualized treatment prescriptions.

MATERIAL AND METHODS

Ten prostate cancer patients with well-defined ILs were selected. Multiparametric MRI was used to delineate ILs, which were transferred to the planning CT via image registration. Pencil beam scanning proton therapy and volumetric modulated arc therapy treatment plans, were created for each patient. Each modality featured 6 plans: (1) moderately hypofractionated dose: 70 Gy to the prostate in 28 fractions, (2)-(6) plan 1 plus additional simultaneous-integrated-boost to ILs to 75.6, 81.2, 86.6, 98 and 112 Gy in 28 fractions. Equivalent dose to 2 Gy-per-fraction (EqD2) was used to calculate tumor control (TCP) and normal tissue complication probabilities (NTCP) for ILs and organs-at-risk.

RESULTS

For both modalities, the maximum necessary dose to achieve TCP > 99% was 98 Gy for very high-risk ILs. For lower risk ILs lower doses were sufficient. NTCP was <25% and 35% for protons and photons at the maximum dose escalation, respectively. For the cases and beam characteristics considered, proton therapy was dosimetrically superior when IL was >4 cc or located <2.5 mm from the rectum.

CONCLUSION

This work demonstrated the potential role for proton therapy in the setting of prostate focal dose escalation. We propose that anatomical characteristic could be used as criteria to identify patients who would benefit from proton treatment.

Implementation of a real-time, ultrasound-guided prostate HDR brachytherapy program

This work presents a comprehensive commissioning and workflow development process of a real-time, ultrasound (US) image-guided treatment planning system (TPS), a stepper and a US unit. To adequately benchmark the system, commissioning tasks were separated into (1) US imaging, (2) stepper mechanical, and (3) treatment planning aspects. Quality assurance US imaging measurements were performed following the AAPM TG-128 and GEC-ESTRO recommendations and consisted of benchmarking the spatial resolution, accuracy, and low-contrast detectability. Mechanical tests were first used to benchmark the electronic encoders within the stepper and were later expanded to evaluate the needle free length calculation accuracy. Needle reconstruction accuracy was rigorously evaluated at the treatment planning level. The calibration length of each probe was redundantly checked between the calculated and measured needle free length, which was found to be within 1 mm for a variety of scenarios. Needle placement relative to a reference fiducial and coincidence of imaging coordinate origins were verified to within 1 mm in both sagittal and transverse imaging planes. The source strength was also calibrated within the interstitial needle and was found to be 1.14% lower than when measured in a plastic needle. Dose calculations in the TPS and secondary dose calculation software were benchmarked against manual TG-43 calculations. Calculations among the three calculation methods agreed within 1% for all calculated points. Source positioning and dummy coincidence was tested following the recommendations of the TG-40 report. Finally, the development of the clinical workflow, checklists, and planning objectives are discussed and included within this report. The commissioning of real-time, US-guided HDR prostate systems requires careful consideration among several facets including the image quality, dosimetric, and mechanical accuracy. The TPS relies on each of these components to develop and administer a treatment plan, and as such, should be carefully examined.

Margin verification for hypofractionated prostate radiotherapy using a novel dose accumulation workflow and iterative CBCT

PURPOSE

Hypofractionated radiotherapy for prostate cancer reduces the inconvenience of an extended treatment course but the appropriate treatment margin to ensure tumor control while minimizing toxicity is not standardized. Using a novel dose accumulation workflow with iterative CBCT (iCBCT) images, we were able to validate treatment margins.

METHODS

Sixteen patients treated to the prostate on a hypofractionated clinical trial were selected. Prescription dose was 3625 cGy to > 95% of the PTV in 5 fractions with a boost to 4000 cGy to the high risk GTV (if applicable). PTV margin expansion was 5 mm isotropic except 3 mm posterior, no margin for the GTV. Daily iCBCT images were obtained while practicing strict bladder and rectal filling protocols. Using a novel adaptive dose accumulation workflow, synthetic CTs were created and the daily delivered dose was recalculated. The daily dose distributions were accumulated and target coverage and organ dose were assessed.

RESULTS

Although the PTV coverage dropped for the accumulated dose, the prostate coverage was not compromised. The differences in bladder and anorectum dose were not significantly different. Four patients received a boost to the GTV and a significant decrease in coverage was noted in the accumulated dose.

CONCLUSIONS

The novel dose accumulation workflow demonstrated that daily iCBCT images can be used for dose accumulation. We found that our clinical treatment margins resulted in adequate dose to the prostate while sparing OARs. If the goal is to deliver the full dose to an intra-prostatic GTV, a margin may be appropriate.

Non-rigid image registration of 4D-MRI data for improved delineation of moving tumors

BACKGROUND

To increase the image quality of end-expiratory and end-inspiratory phases of retrospective respiratory self-gated 4D MRI data sets using non-rigid image registration for improved target delineation of moving tumors.

METHODS

End-expiratory and end-inspiratory phases of volunteer and patient 4D MRI data sets are used as targets for non-rigid image registration of all other phases using two different registration schemes: In the first, all phases are registered directly (dir-Reg) while next neighbors are successively registered until the target is reached in the second (nn-Reg). Resulting data sets are quantitatively compared using diaphragm and tumor sharpness and the coefficient of variation of regions of interest in the lung, liver, and heart. Qualitative assessment of the patient data regarding noise level, tumor delineation, and overall image quality was performed by blinded reading based on a 4 point Likert scale.

RESULTS

The median coefficient of variation was lower for both registration schemes compared to the target. Median dir-Reg coefficient of variation of all ROIs was 5.6% lower for expiration and 7.0% lower for inspiration compared with nn-Reg. Statistical significant differences between the two schemes were found in all comparisons. Median sharpness in inspiration is lower compared to expiration sharpness in all cases. Registered data sets were rated better compared to the targets in all categories. Over all categories, mean expiration scores were 2.92 ± 0.18 for the target, 3.19 ± 0.22 for nn-Reg and 3.56 ± 0.14 for dir-Reg and mean inspiration scores 2.25 ± 0.12 for the target, 2.72 ± 215 0.04 for nn-Reg and 3.78 ± 0.04 for dir-Reg.

CONCLUSIONS

In this work, end-expiratory and inspiratory phases of a 4D MRI data sets are used as targets for non-rigid image registration of all other phases. It is qualitatively and quantitatively shown that image quality of the targets can be significantly enhanced leading to improved target delineation of moving tumors.

Volumetric and Voxel-Wise Analysis of Dominant Intraprostatic Lesions on Multiparametric MRI

Introduction: Multiparametric MR imaging (mpMRI) has shown promising results in the diagnosis and localization of prostate cancer. Furthermore, mpMRI may play an important role in identifying the dominant intraprostatic lesion (DIL) for radiotherapy boost. We sought to investigate the level of correlation between dominant tumor foci contoured on various mpMRI sequences. Methods: mpMRI data from 90 patients with MR-guided biopsy-proven prostate cancer were obtained from the SPIE-AAPM-NCI Prostate MR Classification Challenge. Each case consisted of T2-weighted (T2W), apparent diffusion coefficient (ADC), and K^trans images computed from dynamic contrast-enhanced sequences. All image sets were rigidly co-registered, and the dominant tumor foci were identified and contoured for each MRI sequence. Hausdorff distance (HD), mean distance to agreement (MDA), and Dice and Jaccard coefficients were calculated between the contours for each pair of MRI sequences (i.e., T2 vs. ADC, T2 vs. K^trans, and ADC vs. K^trans). The voxel wise spearman correlation was also obtained between these image pairs. Results: The DILs were located in the anterior fibromuscular stroma, central zone, peripheral zone, and transition zone in 35.2, 5.6, 32.4, and 25.4% of patients, respectively. Gleason grade groups 1-5 represented 29.6, 40.8, 15.5, and 14.1% of the study population, respectively (with group grades 4 and 5 analyzed together). The mean contour volumes for the T2W images, and the ADC and K^trans maps were 2.14 ± 2.1, 2.22 ± 2.2, and 1.84 ± 1.5 mL, respectively. K^trans values were indistinguishable between cancerous regions and the rest of prostatic regions for 19 patients. The Dice coefficient and Jaccard index were 0.74 ± 0.13, 0.60 ± 0.15 for T2W-ADC and 0.61 ± 0.16, 0.46 ± 0.16 for T2W-K^trans. The voxel-based Spearman correlations were 0.20 ± 0.20 for T2W-ADC and 0.13 ± 0.25 for T2W-K^trans. Conclusions: The DIL contoured on T2W images had a high level of agreement with those contoured on ADC maps, but there was little to no quantitative correlation of these results with tumor location and Gleason grade group. Technical hurdles are yet to be solved for precision radiotherapy to target the DILs based on physiological imaging. A Boolean sum volume (BSV) incorporating all available MR sequences may be reasonable in delineating the DIL boost volume.

Dosimetric impact of intrafraction motion on boosts on intraprostatic lesions: a simulation based on actual motion data from real time ultrasound tracking

Background

Intrafraction motion is particularly problematic in case of small target volumes and narrow margins. Here we simulate the dose coverage of intraprostatic lesions (IPL) by simultaneous integrated boosts (SIB). For this purpose, we use a large sample of actual intrafraction motion data.

Methods

Fifty-three h of intra-fraction motion of the prostate were recorded in real-time by 4D ultrasound (4DUS) during 720 fractions in 28 patients. We simulate spherical IPLs with 3, 5, and 7 mm radius and matching spherical SIBs with 0, 2, and 5 mm safety margins. The volumetric overlap between IPLs and SIBs is calculated. Dose volume histograms (DVH) are estimated by Monte Carlo simulation.

Results

On average, the distance of the prostate was 1.3 mm from its initial position over all fractions and patients. Average volumetric overlap was 73, 82, and 87% of IPL volume in case of 3, 5, and 7 mm IPLs and SIBs without safety margins. These improved to 95% or more in case of 2 mm safety margins and 98% or more in case of 5 mm safety margins. DVHs showed that 80% of the IPL volume received 60, 72, and 79% of maximum dose in case of 3, 5, and 7 mm IPLs and SIBs without safety margins. These improved to 94% or more given moderately sized safety margins of 2 mm.

Conclusions

On average over all fractions and patients, the dose coverage would have been acceptable even for small target volumes such as IPLs of radius 3 to 7 mm and narrow fields. Moderate safety margins of 2 mm could have ensured a delivery of 90% or more of the SIB dose to the IPL. In this case, SIB volume would have been considerably larger than IPL volume, but still considerably smaller than the overall PTV of the prostate.

Electronic supplementary material

The online version of this article (10.1186/s13014-019-1285-1) contains supplementary material, which is available to authorized users.

Resolution and registration in dual-plane co-RASOR MR

Magnetic resonance imaging (MRI) has superior soft tissue contrast and lower interobserver variability compared to computed tomography and advances in equipment and pseudo-CT estimation have allowed for MR-only radiation therapy planning. Dedicated MR sequences have been used to localize paramagnetic structures with positive contrast, and most implanted seeds are gold fiducial markers (GFMs). We used a fast, dual-plane co-RASOR sequence to localize implanted GFMs with positive contrast in phantom and tissue to assess their resolution and registration accuracy of registration to CT. Off-resonant reconstructions of co-RASOR images were able to resolve GFMs down to 5 mm apart at 12 cm FOV. No systematic biases were observed by comparing registration of co-RASOR and bSSFP to CT images in an MR-compatible Lego phantom with a set of highly visible known points. The standard deviations of the MR to CT distance errors were  <0.5 mm in all directions. We separated the component due to registration by comparing the two MR sequences, which had a maximum standard deviation of 0.36 mm in the SI-direction. Registration using the positive contrast points in a porcine sample phantom showed increased errors, but co-RASOR still performs acceptably with a target registration error of  <0.75 mm. The dual-plane co-RASOR sequence could then be used for both registration and image tracking when performing MR-only radiation therapy planning.

Dose Escalation with Simultaneous Integrated Boost (SIB) Using Volumetric Modulated Arc Therapy (VMAT) in Rectal Cancer

PURPOSE

Assess feasibility-rate of PCR, short-term toxicity after neoadjuvant concurrent chemoradiation (NACRT) delivered via simultaneous integrated boost (SIB) using volumetric modulated arc therapy (VMAT) technique for locally advanced rectal cancer.

METHODS

Retrospective evaluation of patients with locally advanced rectal cancer treated with VMAT-SIB technique preoperatively at an academic tertiary care center in Riyadh, Saudi Arabia between February 2013 and March 2017.

RESULTS

One hundred patients with depth of invasion staged as T3/T4 or T2 in 93 and seven patients, respectively. Lymph node metastasis was staged as N1/N2 or N0 in 87 and 13 patients, respectively. Circumferential radial margin (CRM) was involved radiologically prior to treatment in 50 patients. A dose of 55 or 50 Gy was given to 71 and 29 patients, respectively. All treatments were completed without interruption. Grade 3/4 toxicity was not observed. Low anterior resection and abdominoperineal resection were performed with negative proximal, distal, and radial margins in 72 and 28 patients, respectively. There were no immediate significant postoperative complications. Histologically, no residual tumor (grade 0) was noted in 20 patients (pCR). Regression grade 1, 2, and 3 were noted in 31, 34, and 15 patients. Average number of lymph nodes retrieved in the surgical specimen was 12 (range 6-22). Lymph nodes were negative for cancer in 80 patients.

CONCLUSION

Dose escalation with SIB-VMAT as NACRT for rectal cancer is feasible. Moreover, it can increase the rate of pathological complete response with a favorable toxicity profile. Clinical benefit of this approach needs to be validated in a larger cohort of patients with longer follow-up.

Prostate irradiation with focal dose escalation to the intraprostatic dominant nodule: a systematic review

Radiation therapy (RT) is a curative treatment option for localized prostate cancer. Prostate irradiation with focal dose escalation to the intraprostatic dominant nodule (IDN) is an emerging treatment option that involves the prophylactic irradiation of the whole prostate while increasing RT doses to the visible prostatic tumor. Because of the lack of large multicentre trials, a systematic review was performed in an attempt to get an overview on the feasibility and efficacy of focal dose escalation to the IDN.

A bibliographic search for articles in English, which were listed in MEDLINE from 2000 to 2016 to identify publications on RT with focal directed boost to the IDN, was performed. The review was completed following the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines.

Twenty-two articles describing 1,378 patients treated with RT using focal boost were identified and fulfilled the selection criteria. Intensity-modulated radiation therapy (IMRT) was used in 720 patients (52.3%), volumetric modulated arc therapy was used in 45 patients (3.3%), stereotactic body radiation therapy (SBRT) in 113 patients (8.2%), and low–dose rate and high–dose rate brachytherapy (BT) were used in 305 patients (22.1%) and 195 patients (14.1%), respectively. Use of androgen deprivation therapy varied substantially among series. Biochemical disease-free survival at 5 years was reported for a cohort of 812 (58.9%) patients. The combined median biochemical disease-free survival for this group of patients was 85% (range: 78.8–100%; 95% confidence interval: 77.1–82.7%).

The average occurrence of grade III or worse gastrointestinal and genitourinary late toxicity was, respectively, 2.5% and 3.1% for intensity-modulated RT boost, 10% and 6% for stereotactic body RT, 6% and 2% for low–dose rate BT, and 4% and 4.3% for high–dose rate BT.

This review shows encouraging results for focal dose escalation to the IDN with acceptable short- to medium-term side effects and biochemical disease control rates. However, owing to the heterogeneity of patient population and the short follow-up, the results should be interpreted with caution. Considering that the clinical endpoint in the studies was biochemical recurrence, the use and duration of androgen deprivation therapy administration should be carefully considered before driving definitive conclusions. Randomized trials with long-term follow-up are needed before this technique can be generally recommended.

Standard whole prostate gland radiotherapy with and without lesion boost in prostate cancer: Toxicity in the FLAME randomized controlled trial

PURPOSE

To compare toxicity rates in patients with localized prostate cancer treated with standard fractionated external beam radiotherapy (EBRT) with or without an additional integrated boost to the macroscopically visible tumour.

MATERIAL AND METHODS

FLAME is a phase 3 multicentre RCT (NCT01168479) of patients with pathologically confirmed localized intermediate or high-risk prostate cancer. The standard treatment arm (n = 287) received a dose to the entire prostate of 77 Gy in 35 fractions. The dose-escalated treatment arm (n = 284) received 77 Gy in 35 fractions to the entire prostate, with an integrated boost up to 95 Gy to the multi-parametric MRI-defined (macroscopic) tumour within the prostate. Treatment related toxicity was measured using the CTCAE version 3.0. Grade 2 or worse GU or GI events up to two years were compared between groups by presenting proportions and by Generalized Estimating Equations (GEE) analyses for repeated measures.

RESULTS

Ninety percent of the 571 men randomly assigned between September 2009 and January 2015 had high-risk disease (Ash 2000), of whom nearly 66% were prescribed hormonal therapy up to three years. Median follow-up was 55 months at the time of this analysis. Toxicity prevalence rates for both GI and GU increased until the end of treatment and regressed thereafter, with no obvious differences across treatment groups. Late cumulative GI toxicity rates were 11.1% and 10.2% for the standard and dose-escalated group, respectively. These rates were 22.6% and 27.1% for GU toxicity. GEE analyses showed that both GU toxicity and GI toxicity (≥grade 2) up to two years after treatment were similar between arms (OR 1.02 95%CI 0.78-1.33p = 0.81 and (OR 1.19 95%CI 0.82-1.73p = 0.38), respectively.

CONCLUSIONS

In intermediate- and high-risk prostate cancer patients, focal dose escalation integrated with standard EBRT did not result in an increase in GU and GI toxicity when compared to the standard treatment up to two years after treatment. This suggests that the described focal dose escalation technique is safe and feasible.

The delineation of intraprostatic boost regions for radiotherapy using multimodality imaging

Dose escalation to the prostate improves tumor control but at the expense of increased rectal toxicity. Modern imaging can be used to detect the most common site of recurrence, the intraprostatic lesion (IPL), which has led to the concept of focusing dose escalation to the IPL in order to improve the therapeutic ratio. Imaging must be able to detect lesions with adequate sensitivity and specificity to accurately delineate the IPL. This information must be carefully integrated into the radiotherapy planning process to ensure the dose is targeted to the IPL. This review will consider the role and challenges of multiparametric MRI and PET computed tomography in delineating a tumor boost to be delivered by external beam radiotherapy.

Evolving Paradigm of Radiotherapy for High-Risk Prostate Cancer: Current Consensus and Continuing Controversies

High-risk prostate cancer is an aggressive form of the disease with an increased risk of distant metastasis and subsequent mortality. Multiple randomized trials have established that the combination of radiation therapy and long-term androgen deprivation therapy improves overall survival compared to either treatment alone. Standard of care for men with high-risk prostate cancer in the modern setting is dose-escalated radiotherapy along with 2-3 years of androgen deprivation therapy (ADT). There are research efforts directed towards assessing the efficacy of shorter ADT duration. Current research has been focused on assessing hypofractionated and stereotactic body radiation therapy (SBRT) techniques. Ongoing randomized trials will help assess the utility of pelvic lymph node irradiation. Research is also focused on multimodality therapy with addition of a brachytherapy boost to external beam radiation to help improve outcomes in men with high-risk prostate cancer.

Quantification of the margin required for treating intraprostatic lesions

Advances in magnetic resonance imaging (MRI) sequences allow physicians to define the dominant intraprostatic lesion (IPL) in prostate radiation therapy treat-ments allowing for dose escalation and potentially increased tumor control. This work quantifies the margin required around the MRI-defined IPL accounting for both prostate motion and deformation. Ten patients treated with a simultaneous integrated intraprostatic boost (SIIB) were retrospectively selected and replanned with incremental 1 mm margins from 0-5 mm around the IPL to determine if there were any significant differences in dosimetric parameters. Sensitivity analysis was then performed accounting for random and systematic uncertainties in both prostate motion and deformation to ensure adequate dose was delivered to the IPL. Prostate deformation was assessed using daily CBCT imaging and implanted fiducial markers. The average IPL volume without margin was 2.3% of the PTV volume and increased to 11.8% with a 5 mm margin. Despite these changes in vol-ume, the only statistically significant dosimetric difference was found for the PTV maximum dose, which increased with increasing margin. The sensitivity analysis demonstrated that a 3.0 mm margin ensures > 95% IPL coverage accounting for both motion and deformation. We found that a margin of 3.0 mm around the MRI defined IPL is sufficient to account for random and systematic errors in IPL posi-tion for the majority of cases.

Dose escalation to dominant intraprostatic lesions with MRI-transrectal ultrasound fusion High-Dose-Rate prostate brachytherapy. Prospective phase II trial

BACKGROUND AND PURPOSE

To demonstrate the feasibility, safety and effectiveness of dose escalation to intraprostatic lesions with MRI-transrectal ultrasound fusion High-Dose-Rate (HDR) brachytherapy.

MATERIALS AND METHODS

15 patients with intermediate-high risk prostate cancer and visible dominant intra-prostatic nodule on mpMRI have been treated. The treatment consisted of combined MRI-TRUS fusion HDR-brachytherapy (1 fraction of 1500cGy) and hypofractionated external beam (3750cGy in 15 fractions). A dose of 1875Gy was delivered to at least 98% of the DIL volume.

RESULTS

Median prostate volume was 23.8cc; median number of needles was 16 (13-18). Dose escalation to DIL was feasible in 14/15 patients (93%) without violating dosimetric constraints and 1 patient presented a minimal deviation of dosimetric restrictions. With a median follow-up of 18months (17-24), none of the patients developed acute urinary retention or grade ⩾3 toxicity. In addition to standard PSA follow-up, response has been assessed by mpMRI at 12months. All patients presented adequate morphological responses on anatomical and functional sequences.

CONCLUSIONS

HDR brachytherapy using MRI-transrectal ultrasound fusion for image guidance is a suitable technique for partial prostate dose escalation. Tolerance and toxicity profiles are excellent and results are encouraging in terms of biochemical, morphological and functional response.

Radiotherapy planning using MRI

The use of magnetic resonance imaging (MRI) in radiotherapy (RT) planning is rapidly expanding. We review the wide range of image contrast mechanisms available to MRI and the way they are exploited for RT planning. However a number of challenges are also considered: the requirements that MR images are acquired in the RT treatment position, that they are geometrically accurate, that effects of patient motion during the scan are minimized, that tissue markers are clearly demonstrated, that an estimate of electron density can be obtained. These issues are discussed in detail, prior to the consideration of a number of specific clinical applications. This is followed by a brief discussion on the development of real-time MRI-guided RT.

Effect on therapeutic ratio of planning a boosted radiotherapy dose to the dominant intraprostatic tumour lesion within the prostate based on multifunctional MR parameters

OBJECTIVE

To demonstrate the feasibility of an 8-Gy focal radiation boost to a dominant intraprostatic lesion (DIL), identified using multiparametric MRI (mpMRI), and to assess the potential outcome compared with a uniform 74-Gy prostate dose.

METHODS

The DIL location was predicted in 23 patients using a histopathologically verified model combining diffusion-weighted imaging, dynamic contrast-enhanced imaging, T2 maps and three-dimensional MR spectroscopic imaging. The DIL defined prior to neoadjuvant hormone downregulation was firstly registered to MRI-acquired post-hormone therapy and subsequently to CT radiotherapy scans. Intensity-modulated radiotherapy (IMRT) treatment was planned for an 8-Gy focal boost with 74-Gy dose to the remaining prostate. Areas under the dose-volume histograms (DVHs) for prostate, bladder and rectum, the tumour control probability (TCP) and normal tissue complication probabilities (NTCPs) were compared with those of the uniform 74-Gy IMRT plan.

RESULTS

Deliverable IMRT plans were feasible for all patients with identifiable DILs (20/23). Areas under the DVHs were increased for the prostate (75.1 ± 0.6 vs 72.7 ± 0.3 Gy; p < 0.001) and decreased for the rectum (38.2 ± 2.5 vs 43.5 ± 2.5 Gy; p < 0.001) and the bladder (29.1 ± 9.0 vs 36.9 ± 9.3 Gy; p < 0.001) for the boosted plan. The prostate TCP was increased (80.1 ± 1.3 vs 75.3 ± 0.9 Gy; p < 0.001) and rectal NTCP lowered (3.84 ± 3.65 vs 9.70 ± 5.68 Gy; p = 0.04) in the boosted plan. The bladder NTCP was negligible for both plans.

CONCLUSION

Delivery of a focal boost to an mpMRI-defined DIL is feasible, and significant increases in TCP and therapeutic ratio were found.

ADVANCES IN KNOWLEDGE

The delivery of a focal boost to an mpMRI-defined DIL demonstrates statistically significant increases in TCP and therapeutic ratio.

Early Outcome of Prostate Intensity Modulated Radiation Therapy (IMRT) Incorporating a Simultaneous Intra-Prostatic MRI Directed Boost

This study assessed the feasibility and outcomes of treating prostate cancer with intensity modulated radiotherapy (IMRT) incorporating a Magnetic Resonance Imaging (MRI) directed boost. Seventy-eight men received IMRT for localized prostate cancer. The entire prostate received 77.4Gy in 43 fractions and simultaneous intra-prostatic boosts (SIB) of 83Gy were administered to increase the dose to the MRI identified malignancy. In 16 (21%) patients, the MRI didn't detect a neoplasm and these patients received an SIB of 81Gy to the posterior prostate. Androgen Deprivation Therapy (ADT) was also administered to 32 (41%) patients. The 3-year rates of biochemical control, local control, distant control, and survival were 92%, 98%, 95%, and 95% respectively. While grade 1-2 toxicities were common, there were only 2 patients who suffered grade 3 toxicity. These patients developed strictures which were dilated resulting in improvement in symptoms such that both had grade 1-2 toxicity at last follow up examination. The results of this program of IMRT incorporating a MRI directed intra-prostatic boost suggest this technique is feasible and well tolerated. This technique appears to shift the therapeutic index favorably by boosting the malignancy to the highest dose without increasing the doses administered to the bladder and rectum.

Accurate prostate tumour detection with multiparametric magnetic resonance imaging: dependence on histological properties

BACKGROUND

To benefit most of focal treatment of prostate tumours, detection with high precision of all tumour voxels is needed. Although diffusion-weighted imaging (DWI) and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) have good diagnostic performance, perfect tumour detection is challenging. In this study, we investigated the variation in prostate tissue characteristics Gleason score (GS), cell density (CD) and microvessel density (MVD) to explain the limitations in tumour voxel detection with a MRI-based logistic regression model.

MATERIAL AND METHODS

Twelve radical prostatectomy patients underwent a pre-operative 3.0T DWI and DCE-MRI exam. The MRI scans were used to calculate voxel-wise tumour probability with a logistic regression model for the peripheral zone (PZ) of the prostate. Tumour probability maps were correlated and validated with whole-mount histology. Additionally, from the whole-mount histological sections CD, MVD and GS were retrieved for every single voxel. GS, CD and MVD of true- and false-positive voxels and of true- and false-negative voxels were compared using Mann-Whitney U-tests.

RESULTS

False-negative tumour voxels had significantly lower CD and MVD (p < 0.0001) and were similar to non-tumour PZ. True-positive detected tumour voxels had high CDs and MVDs (p < 0.0001). In addition, tumour voxels with higher GS showed a trend towards more frequent detection (p = 0.06). Tumour voxels with GS ≥ 3 + 4 showed higher CD and MVD compared to tumour voxels with GS 3 + 3 (p < 0.0001).

CONCLUSION

Tumour voxels with low CD and MVD resemble healthy tissue and are limiting tumour voxel detection using DWI and DCE-MRI. Nevertheless, the most aggressive tumour voxels, containing high CD, MVD and GS, are more likely to be detected and can therefore be treated with high dose using focal therapy or focal boosting.

3 Tesla multiparametric MRI for GTV-definition of Dominant Intraprostatic Lesions in patients with Prostate Cancer--an interobserver variability study

PURPOSE

To evaluate the interobserver variability of gross tumor volume (GTV) - delineation of Dominant Intraprostatic Lesions (DIPL) in patients with prostate cancer using published MRI criteria for multiparametric MRI at 3 Tesla by 6 different observers.

MATERIAL AND METHODS

90 GTV-datasets based on 15 multiparametric MRI sequences (T2w, diffusion weighted (DWI) and dynamic contrast enhanced (DCE)) of 5 patients with prostate cancer were generated for GTV-delineation of DIPL by 6 observers. The reference GTV-dataset was contoured by a radiologist with expertise in diagnostic imaging of prostate cancer using MRI. Subsequent GTV-delineation was performed by 5 radiation oncologists who received teaching of MRI-features of primary prostate cancer before starting contouring session. GTV-datasets were contoured using Oncentra Masterplan® and iplan® Net. For purposes of comparison GTV-datasets were imported to the Artiview® platform (Aquilab®), GTV-values and the similarity indices or Kappa indices (KI) were calculated with the postulation that a KI > 0.7 indicates excellent, a KI > 0.6 to < 0.7 substantial and KI > 0.5 to < 0.6 moderate agreement. Additionally all observers rated difficulties of contouring for each MRI-sequence using a 3 point rating scale (1 = easy to delineate, 2 = minor difficulties, 3 = major difficulties).

RESULTS

GTV contouring using T2w (KI-T2w = 0.61) and DCE images (KI-DCE = 0.63) resulted in substantial agreement. GTV contouring using DWI images resulted in moderate agreement (KI-DWI = 0.51). KI-T2w and KI-DCE was significantly higher than KI-DWI (p = 0.01 and p = 0.003). Degree of difficulty in contouring GTV was significantly lower using T2w and DCE compared to DWI-sequences (both p < 0.0001). Analysis of delineation differences revealed inadequate comparison of functional (DWI, DCE) to anatomical sequences (T2w) and lack of awareness of non-specific imaging findings as a source of erroneous delineation.

CONCLUSIONS

Using T2w and DCE sequences at 3 Tesla for GTV-definition of DIPL in prostate cancer patients by radiation oncologists with knowledge of MRI features results in substantial agreement compared to an experienced MRI-radiologist, but for radiotherapy purposes higher KI are desirable, strengthen the need for expert surveillance. DWI sequence for GTV delineation was considered as difficult in application.

Boosting imaging defined dominant prostatic tumors: a systematic review

INTRODUCTION

Dominant cancer foci within the prostate are associated with sites of local recurrence post radiotherapy. In this systematic review we sought to address the question: "what is the clinical evidence to support differential boosting to an imaging defined GTV volume within the prostate when delivered by external beam or brachytherapy".

MATERIALS AND METHODS

A systematic review was conducted to identify clinical series reporting the use of radiation boosts to imaging defined GTVs.

RESULTS

Thirteen papers describing 11 unique patient series and 833 patients in total were identified. Methods and details of GTV definition and treatment varied substantially between series. GTV boosts were on average 8 Gy (range 3-35 Gy) for external beam, or 150% for brachytherapy (range 130-155%) and GTV volumes were small (<10 ml). Reported toxicity rates were low and may reflect the modest boost doses, small volumes and conservative DVH constraints employed in most studies. Variability in patient populations, study methodologies and outcomes reporting precluded conclusions regarding efficacy.

CONCLUSIONS

Despite a large cohort of patients treated differential boosts to imaging defined intra-prostatic targets, conclusions regarding optimal techniques and/or efficacy of this approach are elusive, and this approach cannot be considered standard of care. There is a need to build consensus and evidence. Ongoing prospective randomized trials are underway and will help to better define the role of differential prostate boosts based on imaging defined GTVs.

Dosimetric benefit of DMLC tracking for conventional and sub-volume boosted prostate intensity-modulated arc radiotherapy

This study investigated the dosimetric impact of uncompensated motion and motion compensation with dynamic multileaf collimator (DMLC) tracking for prostate intensity modulated arc therapy. Two treatment approaches were investigated; a conventional approach with a uniform radiation dose to the target volume and an intraprostatic lesion (IPL) boosted approach with an increased dose to a subvolume of the prostate. The impact on plan quality of optimizations with a leaf position constraint, which limited the distance between neighbouring adjacent MLC leaves, was also investigated. Deliveries were done with and without DMLC tracking on a linear acceleration with a high-resolution MLC. A cylindrical phantom containing two orthogonal diode arrays was used for dosimetry. A motion platform reproduced six patient-derived prostate motion traces, with the average displacement ranging from 1.0 to 8.9 mm during the first 75 s. A research DMLC tracking system was used for real-time motion compensation with optical monitoring for position input. The gamma index was used for evaluation, with measurements with a static phantom or the planned dose as reference, using 2% and 2 mm gamma criteria. The average pass rate with DMLC tracking was 99.9% (range 98.7-100%, measurement as reference), whereas the pass rate for untracked deliveries decreased distinctly as the average displacement increased, with an average pass rate of 61.3% (range 32.7-99.3%). Dose-volume histograms showed that DMLC tracking maintained the planned dose distributions in the presence of motion whereas traces with >3 mm average displacement caused clear plan degradation for untracked deliveries. The dose to the rectum and bladder had an evident dependence on the motion direction and amplitude for untracked deliveries, and the dose to the rectum was slightly increased for IPL boosted plans compared to conventional plans for anterior motion with large amplitude. In conclusion, optimization using a leaf position constraint had minimal dosimetric effect, DMLC tracking improved the target and normal tissue dose distributions compared to no tracking for target motion >3 mm, with the DMLC tracking distributions showing generally good agreement between the planned and delivered doses.

Using manual prostate contours to enhance deformable registration of endorectal MRI

BACKGROUND

Endorectal MRI provides detailed images of the prostate anatomy and is useful for radiation treatment planning. Here we describe a Demons field-initialized B-spline deformable registration of prostate MRI.

MATERIAL AND METHODS

T2-weighted endorectal MRIs of five patients were used. The prostate and the tumor of each patient were manually contoured. The planning MRIs and their segmentations were simulated by warping the corresponding endorectal MRIs using thin plate spline (TPS). Deformable registration was initialized using the deformation field generated using Demons algorithm to map the deformed prostate MRI to the non-deformed one. The solution was refined with B-Spline registration. Volume overlap similarity was used to assess the accuracy of registration and to suggest a minimum margin to account for the registration errors.

RESULTS

Initialization using Demons algorithm took about 15 min on a computer with 2.8 GHz Intel, 1.3 GB RAM. Refinement B-spline registration (200 iterations) took less than 5 min. Using the synthetic images as the ground truth, at zero margin, the average (S.D.) 98 (±0.4)% for prostate coverage was 97 (±1)% for tumor. The average (±S.D.) treatment margin required to cover the entire prostate was 1.5 (±0.2)mm. The average (± S.D.) treatment margin required to cover the tumor was 0.7 (±0.1)mm. We also demonstrated the challenges in registering an in vivo deformed MRI to an in vivo non-deformed MRI.

DISCUSSION

We here present a deformable registration scheme that can overcome large deformation. This platform is expected to be useful for prostate cancer radiation treatment planning.

Development and Evaluation of an Actuated MRI-Compatible Robotic System for MRI-Guided Prostate Intervention

This paper reports the design, development, and magnetic resonance imaging (MRI) compatibility evaluation of an actuated transrectal prostate robot for MRI-guided needle intervention in the prostate. The robot performs actuated needle MRI-guidance with the goals of providing (i) MRI compatibility, (ii) MRI-guided needle placement with accuracy sufficient for targeting clinically significant prostate cancer foci, (iii) reducing interventional procedure times (thus increasing patient comfort and reducing opportunity for needle targeting error due to patient motion), (iv) enabling real-time MRI monitoring of interventional procedures, and (v) reducing the opportunities for error that arise in manually actuated needle placement. The design of the robot, employing piezo-ceramic-motor actuated needle guide positioning and manual needle insertion, is reported. Results of a MRI compatibility study show no reduction of MRI signal-to-noise-ratio (SNR) with the motors disabled. Enabling the motors reduces the SNR by 80% without RF shielding, but SNR is only reduced by 40% to 60% with RF shielding. The addition of radio-frequency shielding is shown to significantly reduce image SNR degradation caused by the presence of the robotic device. An accuracy study of MRI-guided biopsy needle placements in a prostate phantom is reported. The study shows an average in-plane targeting error of 2.4 mm with a maximum error of 3.7 mm. These data indicate the system's needle targeting accuracy is similar to that obtained with a previously reported manually actuated system, and is sufficient to reliably sample clinically significant prostate cancer foci under MRI-guidance.

Functional MRI for radiotherapy dose painting

Modern radiation therapy techniques are exceptionally flexible in the deposition of radiation dose in a target volume. Complex distributions of dose can be delivered reliably, so that the tumor is exposed to a high dose, whereas nearby healthy structures can be avoided. As a result, an increase in curative dose is no longer invariably associated with an increased level of toxicity. This modern technology can be exploited further by modulating the required dose in space so as to match the variation in radiation sensitivity in the tumor. This approach is called dose painting. For dose painting to be effective, functional imaging techniques are essential to identify regions in a tumor that require a higher dose. Several techniques are available in nuclear medicine and radiology. In recent years, there has been a considerable research effort concerning the integration of magnetic resonance imaging (MRI) into the external radiotherapy workflow motivated by the superior soft tissue contrast as compared to computed tomography. In MRI, diffusion-weighted MRI reflects the cell density of tissue and thus may indicate regions with a higher tumor load. Dynamic contrast-enhanced MRI reflects permeability of the microvasculature and blood flow, correlated to the oxygenation of the tumor. These properties have impact on its radiation sensitivity. New questions must be addressed when these techniques are applied in radiation therapy: scanning in treatment position requires alternative solutions to the standard patient setup in the choice of receive coils compared to a diagnostic department. This standard positioning also facilitates repeated imaging. The geometrical accuracy of MR images is critical for high-precision radiotherapy. In particular, when multiparametric functional data are used for dose painting, quantification of functional parameters at a high spatial resolution becomes important. In this review, we will address these issues and describe clinical developments in MRI-guided dose painting.

Dose-escalated simultaneous integrated-boost treatment of prostate cancer patients via helical tomotherapy

PURPOSE

The goal of this work was to assess the feasibility of moderately hypofractionated simultaneous integrated-boost intensity-modulated radiotherapy (SIB-IMRT) with helical tomotherapy in patients with localized prostate cancer regarding acute side effects and dose-volume histogram data (DVH data).

METHODS

Acute side effects and DVH data were evaluated of the first 40 intermediate risk prostate cancer patients treated with a definitive daily image-guided SIB-IMRT protocol via helical tomotherapy in our department. The planning target volume including the prostate and the base of the seminal vesicles with safety margins was treated with 70 Gy in 35 fractions. The boost volume containing the prostate and 3 mm safety margins (5 mm craniocaudal) was treated as SIB to a total dose of 76 Gy (2.17 Gy per fraction). Planning constraints for the anterior rectal wall were set in order not to exceed the dose of 76 Gy prescribed to the boost volume. Acute toxicity was evaluated prospectively using a modified CTCAE (Common Terminology Criteria for Adverse Events) score.

RESULTS

SIB-IMRT allowed good rectal sparing, although the full boost dose was permitted to the anterior rectal wall. Median rectum dose was 38 Gy in all patients and the median volumes receiving at least 65 Gy (V65), 70 Gy (V70), and 75 Gy (V75) were 13.5%, 9%, and 3%, respectively. No grade 4 toxicity was observed. Acute grade 3 toxicity was observed in 20% of patients involving nocturia only. Grade 2 acute intestinal and urological side effects occurred in 25% and 57.5%, respectively. No correlation was found between acute toxicity and the DVH data.

CONCLUSION

This institutional SIB-IMRT protocol using daily image guidance as a precondition for smaller safety margins allows dose escalation to the prostate without increasing acute toxicity.

Pathologic validation of a model based on diffusion-weighted imaging and dynamic contrast-enhanced magnetic resonance imaging for tumor delineation in the prostate peripheral zone

PURPOSE

For focal boost strategies in the prostate, the robustness of magnetic resonance imaging-based tumor delineations needs to be improved. To this end we developed a statistical model that predicts tumor presence on a voxel level (2.5×2.5×2.5 mm3) inside the peripheral zone. Furthermore, we show how this model can be used to derive a valuable input for radiotherapy treatment planning.

METHODS AND MATERIALS

The model was created on 87 radiotherapy patients. For the validation of the voxelwise performance of the model, an independent group of 12 prostatectomy patients was used. After model validation, the model was stratified to create three different risk levels for tumor presence: gross tumor volume (GTV), high-risk clinical target volume (CTV), and low-risk CTV.

RESULTS

The model gave an area under the receiver operating characteristic curve of 0.70 for the prediction of tumor presence in the prostatectomy group. When the registration error between magnetic resonance images and pathologic delineation was taken into account, the area under the curve further improved to 0.89. We propose that model outcome values with a high positive predictive value can be used to define the GTV. Model outcome values with a high negative predictive value can be used to define low-risk CTV regions. The intermediate outcome values can be used to define a high-risk CTV.

CONCLUSIONS

We developed a logistic regression with a high diagnostic performance for voxelwise prediction of tumor presence. The model output can be used to define different risk levels for tumor presence, which in turn could serve as an input for dose planning. In this way the robustness of tumor delineations for focal boost therapy can be greatly improved.

Single blind randomized phase III trial to investigate the benefit of a focal lesion ablative microboost in prostate cancer (FLAME-trial): study protocol for a randomized controlled trial

Background

The treatment results of external beam radiotherapy for intermediate and high risk prostate cancer patients are insufficient with five-year biochemical relapse rates of approximately 35%. Several randomized trials have shown that dose escalation to the entire prostate improves biochemical disease free survival. However, further dose escalation to the whole gland is limited due to an unacceptable high risk of acute and late toxicity. Moreover, local recurrences often originate at the location of the macroscopic tumor, so boosting the radiation dose at the macroscopic tumor within the prostate might increase local control. A reduction of distant metastases and improved survival can be expected by reducing local failure. The aim of this study is to investigate the benefit of an ablative microboost to the macroscopic tumor within the prostate in patients treated with external beam radiotherapy for prostate cancer.

Methods/Design

The FLAME-trial (Focal Lesion Ablative Microboost in prostatE cancer) is a single blind randomized controlled phase III trial. We aim to include 566 patients (283 per treatment arm) with intermediate or high risk adenocarcinoma of the prostate who are scheduled for external beam radiotherapy using fiducial markers for position verification. With this number of patients, the expected increase in five-year freedom from biochemical failure rate of 10% can be detected with a power of 80%. Patients allocated to the standard arm receive a dose of 77 Gy in 35 fractions to the entire prostate and patients in the experimental arm receive 77 Gy to the entire prostate and an additional integrated microboost to the macroscopic tumor of 95 Gy in 35 fractions. The secondary outcome measures include treatment-related toxicity, quality of life and disease-specific survival. Furthermore, by localizing the recurrent tumors within the prostate during follow-up and correlating this with the delivered dose, we can obtain accurate dose-effect information for both the macroscopic tumor and subclinical disease in prostate cancer. The rationale, study design and the first 50 patients included are described.

Trial registration

This study is registered at ClinicalTrials.gov: NCT01168479

An MRI-compatible robotic system with hybrid tracking for MRI-guided prostate intervention

This paper reports the development, evaluation, and first clinical trials of the access to the prostate tissue (APT) II system-a scanner independent system for magnetic resonance imaging (MRI)-guided transrectal prostate interventions. The system utilizes novel manipulator mechanics employing a steerable needle channel and a novel six degree-of-freedom hybrid tracking method, comprising passive fiducial tracking for initial registration and subsequent incremental motion measurements. Targeting accuracy of the system in prostate phantom experiments and two clinical human-subject procedures is shown to compare favorably with existing systems using passive and active tracking methods. The portable design of the APT II system, using only standard MRI image sequences and minimal custom scanner interfacing, allows the system to be easily used on different MRI scanners.

Parameters favorable to intraprostatic radiation dose escalation in men with localized prostate cancer

PURPOSE

To identify , within the framework of a current Phase I trial, whether factors related to intraprostatic cancer lesions (IPLs) or individual patients predict the feasibility of high-dose intraprostatic irradiation.

METHODS AND MATERIALS

Endorectal coil MRI scans of the prostate from 42 men were evaluated for dominant IPLs. The IPLs, prostate, and critical normal tissues were contoured. Intensity-modulated radiotherapy plans were generated with the goal of delivering 75.6 Gy in 1.8-Gy fractions to the prostate, with IPLs receiving a simultaneous integrated boost of 3.6 Gy per fraction to a total dose of 151.2 Gy, 200% of the prescribed dose and the highest dose cohort in our trial. Rectal and bladder dose constraints were consistent with those outlined in current Radiation Therapy Oncology Group protocols.

RESULTS

Dominant IPLs were identified in 24 patients (57.1%). Simultaneous integrated boosts (SIB) to 200% of the prescribed dose were achieved in 12 of the 24 patients without violating dose constraints. Both the distance between the IPL and rectum and the hip-to-hip patient width on planning CT scans were associated with the feasibility to plan an SIB (p = 0.002 and p = 0.0137, respectively).

CONCLUSIONS

On the basis of this small cohort, the distance between an intraprostatic lesion and the rectum most strongly predicted the ability to plan high-dose radiation to a dominant intraprostatic lesion. High-dose SIB planning seems possible for select intraprostatic lesions.

Image-guided radiotherapy for prostate cancer: a prospective trial of concomitant boost using indium-111-capromab pendetide (ProstaScint) imaging

PURPOSE

To evaluate, in a prospective study, the use of (111)In-capromab pendetide (ProstaScint) scan to guide the delivery of a concomitant boost to intraprostatic region showing increased uptake while treating the entire gland with intensity-modulated radiotherapy for localized prostate cancer.

METHODS AND MATERIALS

From September 2002 to November 2005, 71 patients were enrolled. Planning pelvic CT and (111)In-capromab pendetide scan images were coregistered. The entire prostate gland received 75.6 Gy/42 fractions, whereas areas of increased uptake in (111)In-capromab pendetide scan received 82 Gy. For patients with T3/T4 disease, or Gleason score ≥8, or prostate-specific antigen level >20 ng/mL, 12 months of adjuvant androgen deprivation therapy was given. In January 2005 the protocol was modified to give 6 months of androgen deprivation therapy to patients with a prostate-specific antigen level of 10-20 ng/mL or Gleason 7 disease.

RESULTS

Thirty-one patients had low-risk, 30 had intermediate-risk, and 10 had high-risk disease. With a median follow-up of 66 months, the 5-year biochemical control rates were 94% for the entire cohort and 97%, 93%, and 90% for low-, intermediate-, and high-risk groups, respectively. Maximum acute and late urinary toxicities were Grade 2 for 38 patients (54%) and 28 patients (39%) and Grade 3 for 1 and 3 patients (4%), respectively. One patient had Grade 4 hematuria. Maximum acute and late gastrointestinal toxicities were Grade 2 for 32 patients (45%) and 15 patients (21%), respectively. Most of the side effects improved with longer follow-up.

CONCLUSION

Concomitant boost to areas showing increased uptake in (111)In-capromab pendetide scan to 82 Gy using intensity-modulated radiotherapy while the entire prostate received 75.6 Gy was feasible and tolerable, with 94% biochemical control rate at 5 years.