Preliminary report of toxicity following 3D radiation therapy for prostate cancer on 3DOG/RTOG 9406

Evaluation approach for whole dose distribution in clinical cases using spherical projection and spherical harmonics expansion: spherical coefficient tensor and score method

Whole dose distribution results from well-conceived treatment plans including patient-specific (location, size and shape of tumor, etc.) and facility-specific (clinical policy and goal, equipment, etc.) information. To evaluate the whole dose distribution efficiently and effectively, we propose a method to apply spherical projection and real spherical harmonics (SH) expansion, thus leading to the expanded coefficients as a rank-2 tensor, SH coefficient tensor, for every patient-specific dose distribution. To verify the feature of this tensor, we introduce Isomap from the manifold learning method and multi-dimensional scaling (MDS). Subsequently, we obtained the MDS distance representing similarity, η, and the SH score, ζ, which is a Frobenius norm of the SH coefficient tensor. These were then validated in the intensity-modulated radiation therapy (IMRT) data sets of: (i) 375 mixing treated regions, (ii) 135 head and neck (HN), and (iii) 132 prostate cases, respectively. The MDS map indicated that the SH coefficient tensor enabled a quantitative feature extraction of whole dose distributions. In particular, the SH score systematically detected irregular cases as the deviation higher than +1.5 standard deviations (SD) from the average case, which matched up with clinically irregular case that required very complicated dose distributions. In summary, the proposed SH coefficient tensor is a useful representation of the whole dose distribution. The SH score from the SH coefficient tensor is a convenient and simple criterion used to characterize the entire dose distributions, which is not dependent on the data set.

Radiation toxicity in prostate cancer patients

Prostate cancer (PC) is the most frequent male tumor, accounting for about one-third of all cancers in men. Since survival is often favorable regardless of therapy, treatment decisions may depend on therapy-specific health outcomes. The majority of men initially diagnosed with localized PC ultimately die with, rather than of, their disease. As a result, men who are diagnosed will live many years with the treatment's sequelae. The major therapeutic strategies include radical prostatectomy or external beam radiotherapy. Radiotherapy is one of the curative treatment options. The tumor dose-response relationship has been studied and is widely accepted. The unsatisfactory local control with doses < 70 Gy led to dose escalation using highly precise radiotherapy techniques - three-dimensional conformal radiotherapy and intensity-modulated radiotherapy enabling the delivery of high radiation doses up to 74 - 78 Gy. Bowel, rectal and urinary toxicities are the principal limiting factors in delivering a high dose. Acute symptoms include a change in bowel habits, urgency, and fecal incontinence. The most commonly reported late toxicities were chronic diarrhea, proctitis, or rectal bleeding. Several factors have been associated with increased gastrointestinal toxicity such as larger bowel volume receiving high doses, the patient's age, diabetes, and concomitant use of androgen deprivation therapy. Bladder damage resulting from acute radiation toxicity is manifested as radiation cystitis (frequent urination and dysuric disorders). Smoking, previous abdominopelvic surgeries and the use of diuretics significantly affect the occurrence of acute genitourinary toxicity grade ≥ 2. Risk factors for the development of late genitourinary complications are higher radiation dose, previous urinary problems, transurethral interventions, and acute genitourinary complications. It is essential to strike a balance between the therapeutic benefits and radiotherapy side effects. Severe late complications significantly reduce the quality of life (QOL) of PC survivors. Early detection and proper evaluation of complications are especially important in increasing the patient's QOL.

Assessing the safety and feasibility of neoadjuvant hormone and radiation therapy followed by robot-assisted radical prostatectomy for treating locally advanced prostate cancer: protocol for an open-label, dose-escalation, single-centre, phase I clinical trial

INTRODUCTION

Patients with locally advanced prostate cancer are at high risk of recurrence after definitive treatment. There are emerging data that radical prostatectomy can delay the progression of castration resistance and potentially prolong survival. Neoadjuvant radiation therapy improves local control and has shown survival benefit with favourable toxicity profiles in several other malignancies. We have designed this trial to investigate whether this combination, which theoretically maximises local control, is a safe and feasible approach for treating locally advanced prostate cancer.

METHODS AND ANALYSIS

This study is a phase I, open-label study to investigate the safety and feasibility of neoadjuvant hormone and radiation therapy followed by robot-assisted radical prostatectomy by a traditional 3+3 dose-escalation design with four planned radiation dose levels (39.6 Gy/22F, 45 Gy/25F, 50.4 Gy/28F and 54 Gy/30F). Locally advanced prostate cancer patients with positive pelvic and/or retroperitoneal lymph nodes will be recruited. The primary objective is to determine the adverse events and maximal tolerable dose (MTD) of neoadjuvant radiotherapy. Toxicity will be assessed using the National Cancer Institute Common Toxicity Criteria V.5.0.

ETHICS AND DISSEMINATION

This protocol was approved by the Institutional Review Board of Shanghai Changhai Hospital (ref. CHEC2019-070 and CHEC2019-082). The study will be performed in compliance with applicable local legislation and in accordance with the ethical principles developed by the World Medical Association in the Declaration of Helsinki 2013. Study results will be disseminated through conferences and peer-reviewed scientific journals.

TRIAL REGISTRATION NUMBERS

ChiCTR1900022716; ChiCTR1900022754.

Prevention of acute radiation-induced Proctitis by Aloe vera: a prospective randomized, double-blind, placebo controlled clinical trial in Pelvic Cancer patients

Background

Acute radiation-induced proctitis (ARP) is the most common side effect following radiotherapy for malignant pelvic disease. This study evaluated the efficacy of Aloe vera ointment in prevention of ARP.

Methods

Forty-two patients receiving external-beam radiotherapy (RT) for pelvic malignancies were randomized to receive either Aloe vera 3% or placebo topical ointment during radiotherapy for 6 weeks. These patients were evaluated based on the severity (grade 0–4) of the following symptoms weekly: rectal bleeding, abdominal/rectal pain, diarrhea, or fecal urgency. RTOG acute toxicity criteria and psychosocial status of the patients were also recorded weekly. Lifestyle impact of the symptoms, and quantitative measurement of C-reactive protein (CRP), an indicator of systemic inflammation, were also measured.

Results

The results of present study demonstrated a significant preventive effect for Aloe vera in occurrence of symptom index for diarrhea (p < 0.001), rectal bleeding (p < 0.001), and fecal urgency (p = 0.001). The median lifestyle score improved significantly with Aloe vera during RT (p < 0.001). Intervention patients had a significant lower burden of systemic inflammation as the values for quantitative CRP decreased significantly over 6 weeks of follow-up (p = 0.009).

Conclusion

This study showed that Aloe vera topical ointment was effective in prevention of symptoms of ARP in patients undergoing RT for pelvic cancers.

Trial registration

IRCT201606042027N6. Registration date: 2016-09-04.

A Literature Review of Proton Beam Therapy for Prostate Cancer in Japan

Aim: Patients of proton beam therapy (PBT) for prostate cancer had been continuously growing in number due to its promising characteristics of high dose distribution in the tumor target and a sharp distal fall-off. Considering the large number of proton beam facilities in Japan, the further increase of patients undergoing this treatment is due to the emendations by Japanese National Health Insurance (NHI) and the development of medical equipment and technology, it is necessary to know what kind of research and advancements has been done on proton therapy for prostate cancer in the country. For these reasons, this literature review was conducted. The aim of this review is to identify and discuss research studies of proton beam therapy for prostate cancer in Japan. These include observational, interventional, and secondary data analysis of published articles. Method: A literature review on published works related to proton beam therapy for prostate cancer in Japan was conducted using articles that were gathered in the PubMed database of June 2018. We went through abstracts and manuscripts written in English with the keywords ‘proton beam therapy’, ‘prostate cancer’, and ‘Japan’. Results: A total of 23 articles were included. Fourteen articles were observational studies, most of which focused on the adverse effects of Proton Beam Therapy (PBT). Seven articles were interventional studies related on treatment planning, equipment parts, as well as target positioning. Two were secondary data analysis. The included studies were published in 13 different journals by different institutions using various equipment. Conclusion: Despite the favorable results of proton beam therapy, future research should include more patients and longer follow-up schedules to clarify the definitive role of PBT, yet, up to recent retrospective studies, included in this paper, concluded that PBT can be a suitable treatment option for localized prostate cancer. In addition, interventional studies were conducted by several institutions to further embellish proton therapy.

Risk factors for late bowel and bladder toxicities in NRG Oncology prostate cancer trials of high-risk patients: A meta-analysis of physician-rated toxicities

Purpose

A meta-analysis of sociodemographic variables and their association with late (>180 days from start of radiation therapy[RT]) bowel, bladder, and clustered bowel and bladder toxicities was conducted in patients with high-risk (clinical stages T2c-T4b or Gleason score 8-10 or prostate-specific antigen level >20) prostate cancer.

Methods and materials

Three NRG trials (RTOG 9202, RTOG 9413, and RTOG 9406) that accrued from 1992 to 2000 were used. Late toxicities were measured with the Radiation Therapy Oncology Group Late Radiation Morbidity Scale. After controlling for study, age, Karnofsky Performance Status, and year of accrual, sociodemographic variables were added to the model for each outcome variable of interest in a stepwise fashion using the Fine-Gray regression models with an entry criterion of 0.05.

Results

A total of 2432 patients were analyzed of whom most were Caucasian (76%), had a KPS score of 90 to 100 (92%), and received whole-pelvic RT+HT (67%). Of these patients, 13 % and 16% experienced late grade ≥2 bowel and bladder toxicities, respectively, and 2% and 3% experienced late grade ≥3 bowel and bladder toxicities, respectively. Late grade ≥2 clustered bowel and bladder toxicities were seen in approximately 1% of patients and late grade ≥3 clustered toxicities were seen in 2 patients (<1%). The multivariate analysis showed that patients who received prostate-only RT+HT had a lower risk of experiencing grade ≥2 bowel toxicities than those who received whole-pelvic RT+long-term (LT) HT (hazard ratio: 0.36; 95% confidence interval, 0.18-0.73; P = .0046 and hazard ratio: 0.43; 95% confidence interval, 0.23-0.80; P = .008, respectively). Patients who received whole-pelvic RT had similar chances of having grade ≥2 bowel or bladder toxicities no matter whether they received LT or short-term HT.

Conclusions

Patients with high-risk prostate cancer who receive whole-pelvic RT+LT HT are more likely to have a grade ≥2 bowel toxicity than those who receive prostate-only RT. LT bowel and bladder toxicities were infrequent. Future studies will need to confirm these findings utilizing current radiation technology and patient-reported outcomes.

Androgen Ablation Therapy Does not Increase the Risk of Late Morbidity following 3D-conformal Radiotherapy of Organ-confined Prostate Cancer: The Experience of the European Institute of Oncology

Aims and Background

Androgen ablation therapy in conjunction with radiotherapy-neoadjuvant and adjuvant – has consistently been shown to be associated with improved biochemical and local control, whereas controversy still remains as regards its benefit in terms of overall survival. The objective of this study is to determine the impact of androgen ablation in combination to 3D-conformal radiotherapy on late treatment-related toxicity.

Methods

236 patients were treated with 3D-conformal radiotherapy to a total dose ranging from 70 and 78.6 Gy. Fifty-six patients did not receive any form of androgen ablation whereas 176 were given at least 3 months of neoadjuvant androgen ablation. Of these, 64 stayed on androgen ablation for a median time of 6 months post-radiotherapy. Acute toxicity was evaluated weekly during the course of treatment. Late toxicity was assessed at 3-months intervals during the follow-up. Toxicity was scored according to the RTOG criteria.

Results

The median follow-up was 24.6 months (range, 12-62). The incidence of late genitourinary toxicity was: 3% G2, 3.5% G3, 0.5% G4. The incidence of late gastrointestinal toxicity was: 12% G2, 2% G3, 1% G4. No association was observed between the use of androgen ablation and late treatment-related toxicity. High-risk patients who continued on androgen ablation long-term were not found to have an increased risk of developing late toxicity with respect to those who never had any form of androgen ablation or those only treated neoadjuvantly.

Conclusions

In our experience, the use of androgen ablation does not impact on late toxicity following high dose 3D-conformal radiotherapy for prostate cancer.

Complications of curative radiation treatment for early prostate cancer

AIM

To report the incidence of urological complications following curative radiation treatment for early prostate cancer, including minimally invasive urological procedures (MUIP), hospital admissions and open surgical procedures. Second malignancies following radiation are also reported and compared with patients undergoing a prostatectomy.

METHODS

Included were patients receiving curative intent external beam radiation treatment for early prostate cancer between January 1, 2002, and December 31, 2009. Medical records were reviewed for baseline characteristics, treatment details and outcomes. Kaplan-Meier methods were used to derive the 5-year cumulative incidence of the urological outcomes and second malignancy.

RESULTS

There were 439 patients identified. The median follow-up was 6.96 years. The median age was 69. A total of 56 patients developed a radiation related urological complication, 25 requiring hospital admission. The 5-year cumulative incidence for an MIUP and admission was 3.95% (95% confidence interval (CI), 2.47-6.28) and 2.24% (95% CI, 1.17-4.27), respectively. There were no open surgical procedures. Further malignancy developed in 27 patients during the 5- to 9-year posttreatment period with a cumulative incidence of 10.7% (95% CI, 7.31-15.51). Of the comparator prostatectomy group, of the 265 eligible patients analyzed, 19 patients developed a second malignancy with a cumulative incidence of 9.92% (95% CI, 6.28-15.48). On log-rank testing, there was no difference in the cumulative incidence rates of second malignancy between 5 and 9 years, following respective treatments (P  =  0.8554).

CONCLUSIONS

The incidence of MUIP, hospital admissions and open surgical procedures following radiation is reassuringly low. The second malignancy rates are also low and similar to the rates in patients treated with a prostatectomy.

The comparison of 5-field conformal radiotherapy techniques for the treatment of prostate cancer: The best for femoral head sparing

External radiotherapy is a standard treatment procedure for localized prostate cancer. Given the relatively high long term survival treatment complications have been brought in center of attention. In this planning study, between 2012 and 2014, CT simulation data of 90 consecutive high-risk prostate cancer patients were collected. In the first phase, all were planned for whole pelvis irradiation up to 46Gy in 23 daily fractions. In the second phase, only the prostate gland was the target of radiation. Next, the subjects were divided randomly into three groups and each received a unique 5field conformal radiation plan including Plan A (Gantry angle: 0, 60, 120, 240, and 300), Plan B (Gantry angles: 0, 90, 120, 240, and 270) and Plan C (Gantry angles: 0, 60, 90, 270, and 300). The total dose was 70Gy. For each patient, the rectum, bladder, and both femoral heads were contoured as the at risk organs (OAR). From dose volume histograms, the proportional dose of PTV V100, the bladder and rectum V80 and V90 and femoral head V50 and V100 were calculated in all subjects and compared across plans. A statistically significant difference in the femoral head V50 and V100 was found between our studied 5field plans so that in Plan A (beam angles: 0, 60, 120, 240 and 300) less dose was received by both heads of femur. This study suggests that 5 field treatment planning including an anterior, two anterior oblique and two posterior oblique portals to be more proper for 3D conformal radiotherapy in order to spare femoral head with acceptable PTV coverage, and bladder and rectal doses.

Impact of 18F-Fluciclovine PET on Target Volume Definition for Postprostatectomy Salvage Radiotherapy: Initial Findings from a Randomized Trial

The purpose of this study was to evaluate the role of the synthetic amino acid PET radiotracer ¹⁸F-fluciclovine in modifying the defined clinical and treatment-planning target volumes in postprostatectomy patients undergoing salvage radiotherapy and to evaluate the resulting dosimetric consequences to surrounding organs at risk. Methods: Ninety-six patients were enrolled in a randomized, prospective intention-to-treat clinical trial for potential salvage radiotherapy for recurrent prostate cancer after prostatectomy. The initial treatment plan was based on the results from conventional abdominopelvic CT and MRI. The 45 patients in the experimental arm also underwent abdominopelvic ¹⁸F-fluciclovine PET/CT, and the images were registered with the conventional images to determine whether the results would modify the initial treatment plan. The 51 patients in the control arm did not undergo ¹⁸F-fluciclovine PET/CT. For each patient, the clinical and treatment-planning target volumes that would have been treated before ¹⁸F-fluciclovine registration were compared with those after registration. For organs at risk (rectum, bladder, and penile bulb), the volumes receiving 40 Gy and 65 Gy before registration were compared with those after registration. Statistical comparisons were made using the paired t test. Acute genitourinary and gastrointestinal toxicity as defined by the Radiation Therapy Oncology Group was compared between the control and experimental arms using the χ² test. Results: In 24 cases, radiotherapy was planned to a clinical target volume consisting of the prostate bed alone (CTV) (64.8-66.6 Gy). In 21 cases, radiotherapy was planned to a clinical target volume consisting of the pelvis (CTV1) (45.0 Gy) followed by a boost to the prostate bed (CTV2) (19.8-25.2 Gy). In each case, the respective treatment-planning target volume expansion (PTV, PTV1, or PTV2) was 0.8 cm (0.6 cm posterior). With the exception of PTV2, all postregistration volumes were significantly larger than the corresponding preregistration volumes. Analysis of the rectum, bladder, and penile bulb volumes receiving 40 Gy and 60 Gy demonstrated that only the penile bulb volumes were significantly higher after registration. No significant differences in acute genitourinary or gastrointestinal toxicity were observed. Conclusion: Including information from ¹⁸F-fluciclovine PET in the treatment-planning process led to significant differences in the defined target volume, with higher doses to the penile bulb but no significant differences in rectal or bladder dose or in acute genitourinary or gastrointestinal toxicity. Longer follow-up is needed to determine the impact of ¹⁸F-fluciclovine PET on cancer control and late toxicity endpoints.

Dosimetric correlation of acute and late toxicities in high-risk prostate cancer patients treated with three-dimensional conformal radiotherapy followed by intensity modulated radiotherapy boost

Introduction:

In prostate cancer, higher radiation doses are often related to higher local control rates. However, the clinical effect of these higher doses on normal tissue toxicities is generally overlooked. We dosimetrically analyze sequential intensity modulated radiotherapy (IMRT) plans in high-risk prostate cancer patients and correlate them with acute and late normal tissue toxicities.

Materials and Methods:

Twenty-five high-risk prostate cancer patients were planned with three-dimensional conformal radiotherapy to a dose of 50 Gy delivered in 25 fractions in 5 weeks, followed by seven-field IMRT boost, to a dose of 24 Gy delivered in 12 fractions in 2.5 weeks, along with hormonal therapy. Acute and late toxicities were analyzed using Radiation Therapy Oncology Group toxicity criteria. Student's t-test was used for correlating doses received by normal tissues with toxicity grade. Five-year disease-free survival (DFS) and biochemical relapse-free survival (RFS) were evaluated using Kaplan–Meier analysis.

Results:

Median follow-up of patients was 65 months. Of 25 patients, two developed acute Grade 2 rectal toxicity. Only 1 patient developed acute Grade 2 bladder toxicity. Late Grade 2 and 3 rectal toxicity was seen in 2 and 1 patient, respectively. Late Grade 2 and 3 bladder toxicity was seen in 1 patient each. Grade 2 or more acute rectal toxicity correlated significantly with rectal volume receiving >70 Gy (P = 0.04). The 5-year DFS and biochemical RFS was 70.2% and 79.2%, respectively. One patient failed locally and seven failed at distant sites.

Conclusion:

Sequential IMRT with a dose of 74 Gy and maximum androgen blockade is well tolerated in high-risk patients in Indian setup with adequate control rates.

A comparative study based on image quality and clinical task performance for CT reconstruction algorithms in radiotherapy

CT image reconstruction is typically evaluated based on the ability to reduce the radiation dose to as‐low‐as‐reasonably‐achievable (ALARA) while maintaining acceptable image quality. However, the determination of common image quality metrics, such as noise, contrast, and contrast‐to‐noise ratio, is often insufficient for describing clinical radiotherapy task performance. In this study we designed and implemented a new comparative analysis method associating image quality, radiation dose, and patient size with radiotherapy task performance, with the purpose of guiding the clinical radiotherapy usage of CT reconstruction algorithms. The iDose4iterative reconstruction algorithm was selected as the target for comparison, wherein filtered back‐projection (FBP) reconstruction was regarded as the baseline. Both phantom and patient images were analyzed. A layer‐adjustable anthropomorphic pelvis phantom capable of mimicking 38–58 cm lateral diameter‐sized patients was imaged and reconstructed by the FBP and iDose4 algorithms with varying noise‐reduction‐levels, respectively. The resulting image sets were quantitatively assessed by two image quality indices, noise and contrast‐to‐noise ratio, and two clinical task‐based indices, target CT Hounsfield number (for electron density determination) and structure contouring accuracy (for dose‐volume calculations). Additionally, CT images of 34 patients reconstructed with iDose4 with six noise reduction levels were qualitatively evaluated by two radiation oncologists using a five‐point scoring mechanism. For the phantom experiments, iDose4 achieved noise reduction up to 66.1% and CNR improvement up to 53.2%, compared to FBP without considering the changes of spatial resolution among images and the clinical acceptance of reconstructed images. Such improvements consistently appeared across different iDose4 noise reduction levels, exhibiting limited interlevel noise (<5 HU) and target CT number variations (<1 HU). The radiation dose required to achieve similar contouring accuracy decreased when using iDose4 in place of FBP, up to 32%. Contouring accuracy improvement for iDose4 images, when compared to FBP, was greater in larger patients than smaller‐sized patients. Overall, the iDose4 algorithm provided superior radiation dose control while maintaining or improving task performance, when compared to FBP. The reader study on image quality improvement of patient cases shows that physicians preferred iDose4‐reconstructed images on all cases compared to those from FBP algorithm with overall quality score: 1.21 vs. 3.15, p=0.0022. However, qualitative evaluation strongly indicated that the radiation oncologists chose iDose4 noise reduction levels of 3–4 with additional consideration of task performance, instead of image quality metrics alone. Although higher iDose4 noise reduction levels improved the CNR through the further reduction of noise, there was pixelization of anatomical/tumor structures. Very‐low‐dose scans yielded severe photon starvation artifacts, which decreased target visualization on both FBP and iDose4 reconstructions, especially for the 58 cm phantom size. The iDose4 algorithm with a moderate noise reduction level is hence suggested for CT simulation and treatment planning. Quantitative task‐based image quality metrics should be further investigated to accommodate additional clinical applications.

PACS number(s): 87.57.C‐, 87,57.Q‐

Impact on Late Toxicity of using Transabdominal Ultrasound for Prostate Cancer Patients Treated with Intensity Modulated Radiotherapy

An analysis of the effects of using the B-mode ultrasound Acquisition and Targeting (BAT) system for positioning of prostate cancer patients receiving external beam radiotherapy (EBRT) on late gastrointestinal (GI) and genitourinary (GU) toxicity is provided. The records of 49 consecutive patients treated using the BAT were reviewed; additionally, a comparison (No-BAT) group treated in a similar manner was identified, consisting of 49 patients treated immediately prior to this BAT group. There were no other fundamental differences between the two groups. The daily BAT movements were charted and late toxicity was scored for all patients using established toxicity scales. The results demonstrated similar GU toxicity rates between the two groups, but slightly lower rates of GI toxicity in the BAT group vs. the No-BAT group. However, regression analyses revealed that no factors, including BAT use, were significantly correlated with late GI or GU toxicity. Further efforts, perhaps better undertaken in a multi-institutional setting, are needed to determine whether BAT use can significantly reduce late GI toxicity.

Clinical Implementation of Adaptive Helical Tomotherapy: A Unique Approach to Image-Guided Intensity Modulated Radiotherapy

Image-guided IMRT is a revolutionary concept whose clinical implementation is rapidly evolving. Methods of executing beam intensity modulation have included individually designed compensators, static multi-leaf collimators (MLC), dynamic MLC, and sequential (serial) tomotherapy. We have developed helical tomotherapy as an innovative solution to overcome some of the limitations of other IMRT systems. The unique physical design of helical tomotherapy allows the realization of the concepts of adaptive radiotherapy and conformal avoidance. In principle, these advances should improve normal tissue sparing and permit dose reconstruction and verification, thereby allowing significant biologically effective dose escalation.

Recent radiobiological findings can be translated into altered fractionation schemes that aim to improve the local control and long-term survival. This strategy is being tested at the University of Wisconsin using helical tomotherapy with its highly precise delivery and verification system along with meticulous and practical forms of immobilization. Innovative techniques such optical guidance, respiratory gating, and ultrasound assessments are being designed and tailored for helical tomotherapy use. The intrinsic capability of helical tomotherapy for megavoltage CT (MVCT) imaging for IMRT image-guidance is being optimized.

The unique features of helical tomotherapy might allow implementation of image-guided IMRT that was previously impossible or impractical. Here we review the technological, physical, and radiobiological rationale for the ongoing and upcoming clinical trials that will use image-guided IMRT in the form of helical tomotherapy; and we describe our plans for testing our hypotheses in a rigorous prospective fashion.

Fiducial Markers Implanted during Prostate Brachytherapy for Guiding Conformal External Beam Radiation Therapy

Prostate movement imposes limits on safe dose-escalation with external beam radiation therapy. If the precise daily location of the prostate is known, dose escalation becomes more feasible. We have developed an approach to dose escalation using a combination of prostate brachytherapy followed by external beam radiation therapy in which fiducial markers are placed along with125 I seeds during transperineal interstitial permanent prostate brachytherapy. These markers serve to verify daily prostate location during the subsequent external beam radiotherapy. Prior to implementing this approach, preliminary studies were performed to test visibility of the markers. Three different125 I seed models, as well as gold and silver marker seeds were placed within tissue-equivalent phantoms. Images were obtained with conventional x-rays (75–85 kV) and 6 MV photons from a linear accelerator. All125 I seed models were clearly visible on conventional x-rays but none were seen with 6 MV photons. The gold markers were visible with both energies. The silver markers were visible with conventional x-rays and 6 MV x-rays, but not as clearly as the gold seeds at 6 MV. Subsequently, conventional x-rays, CT scans, and 6 MV port films were obtained in 29 patients in whom fiducial gold marker seeds were implanted into the prostate during125 I prostate brachytherapy. To address the possibility of “seed migration” within the prostate, CT scans were repeated 5 weeks apart in 14 patients and relative positions of the gold seeds were evaluated. The repeated CT scans showed no change in intraprostatic gold marker location, suggesting minimal migration. The gold seeds were visible with conventional x-rays, CT, and 6 MV port films in all patients. During the course of external beam radiation therapy, the gold markers were visible on routine 6 MV port films and were seen in different locations from film to film suggesting prostate motion. Mean daily displacement was 4–5 mm in the anterior-posterior, and 4–5 mm in superior-inferior dimensions. Left-right displacement appeared less, averaging 2–3 mm. We conclude that implantation of gold marker seeds during prostate brachytherapy represents an easily implemented and practical means of prostate localization during subsequent image-guided external beam radiotherapy. With such markers, conformality of the external beam component can be confidently improved without expensive new equipment.

Planned versus 'delivered' bladder dose reconstructed using solid and hollow organ models during prostate cancer IMRT

BACKGROUND AND PURPOSE

All studies to date have evaluated the dosimetric effect of bladder deformation using an organ model that includes the dose to the urine. This research reconstructed bladder dose using both hollow and solid organ models, to determine if dose/volume differences exist.

MATERIALS AND METHODS

35 prostate IMRT patients were selected, who had received 78Gy in 39 fractions and full bladder instructions. Biomechanical modelling and finite element analysis were used to reconstruct bladder dose (solid and hollow organ model) using every third CBCT throughout the treatment course.

RESULTS

Reconstructed dose (ReconDose) was 11.3Gy greater than planned dose (planDose) with a hollow bladder model (p<0.001) and 12.3Gy greater with a solid bladder model (p<0.0001). Median reconstructed volumes within the 30Gy, 65Gy and 78Gy isodoses were 3-4 times larger with the solid organ model (p<0.0001). The difference between planning bladder volume and median treatment volume was associated with the difference between the planDose and reconDose below 78Gy (R(2)>0.61).

CONCLUSIONS

Substantial differences exist between planned and reconstructed bladder dose, associated with the differences in bladder filling between planning and treatment. Dose reconstructed using a solid bladder model over-reports the volume of bladder within key isodose levels and overestimates the differences between planned and reconstructed dose. Dose reconstruction with a hollow organ model is recommended if the goal is to associate that dose with toxicity.

Comparison of dosimetric parameters and acute toxicity after whole-pelvic vs prostate-only volumetric-modulated arc therapy with daily image guidance for prostate cancer

OBJECTIVE

To compare dosimetric parameters and acute toxicity rates between whole-pelvic (WP) and prostate-only (PO) volumetric-modulated arc therapy (VMAT) in patients with localized prostate cancer.

METHODS

A total of 224 consecutive patients treated with definitive VMAT to 78 Gy in 39 fractions were enrolled. Of these, 119 patients received initial WP VMAT at 46.8 Gy in 26 fractions using a simultaneous integrated boost technique, and 105 patients received PO VMAT. Image-guided radiotherapy was practised with daily cone beam CT.

RESULTS

The mean rectal dose, the rectal volume receiving ≥30 Gy (V30Gy), rectal V50Gy, the mean bladder dose, bladder V30Gy and bladder V50Gy were significantly increased in the WP group (p < 0.05 each); however, the rectal V70Gy did not differ between groups (p = 0.101), and the bladder V70Gy was significantly lower in the WP group (p = 0.029). The WP group experienced a significantly increased frequency of acute grade 2 diarrhoea relative to the PO group (5.9% vs 0%; p = 0.015). No differences were seen between the WP and PO groups in terms of acute grade 2 proctitis (10.1% vs 6.7%; p = 0.360) and genitourinary (GU) toxicity (12.6% vs 10.5%; p = 0.620).

CONCLUSION

Despite larger rectum and bladder volumes at low- and medium-dose levels, WP VMAT resulted in no significant increase in acute proctitis or GU toxicity when compared with PO VMAT.

ADVANCES IN KNOWLEDGE

This study demonstrates that whole-pelvic radiotherapy has comparable acute toxicity to those observed with prostate-only radiotherapy when VMAT with daily image guidance is used.

Breast cancer therapy-associated cardiovascular disease

Breast cancer treatments have evolved over the past decades, although several widely used treatments have adverse cardiac effects. Radiotherapy generally improves the survival of women with breast cancer, although its deleterious cardiovascular effects pose competing risks of morbidity and/or mortality. In the past, radiation-associated cardiovascular disease was a phenomenon considered to take more than a decade to manifest, but newer research suggests that this latency is much shorter. Knowledge of coronary anatomy relative to the distribution of the delivered radiation dose has improved over time, and as a result, techniques have enabled this risk to be decreased. Studies continue to be performed to better understand, prevent and mitigate against radiation-associated cardiovascular disease. Treatments such as anthracyclines, which are a mainstay of chemotherapy for breast cancer, and newer targeted agents such as trastuzumab both have established risks of cardiotoxicity, which can limit their effectiveness and result in increased morbidity and/or mortality. Interest in whether β-blockers, statins and/or angiotensin-converting enzyme (ACE)-inhibitors might have therapeutic and/or preventative effects in these patients is currently increasing. This Review summarizes the incidence, risks and effects of treatment-induced cardiovascular disease in patients with breast cancer and describes strategies that might be used to minimize this risk.

Urinary symptoms following external beam radiotherapy of the prostate: Dose-symptom correlates with multiple-event and event-count models

BACKGROUND AND PURPOSE

This study aimed to compare urinary dose-symptom correlates after external beam radiotherapy of the prostate using commonly utilised peak-symptom models to multiple-event and event-count models which account for repeated events.

MATERIALS AND METHODS

Urinary symptoms (dysuria, haematuria, incontinence and frequency) from 754 participants from TROG 03.04-RADAR trial were analysed. Relative (R1-R75 Gy) and absolute (A60-A75Gy) bladder dose-surface area receiving more than a threshold dose and equivalent uniform dose using exponent a (range: a ∈[1 … 100]) were derived. The dose-symptom correlates were analysed using; peak-symptom (logistic), multiple-event (generalised estimating equation) and event-count (negative binomial regression) models.

RESULTS

Stronger dose-symptom correlates were found for incontinence and frequency using multiple-event and/or event-count models. For dysuria and haematuria, similar or better relationships were found using peak-symptom models. Dysuria, haematuria and high grade (⩾ 2) incontinence were associated to high dose (R61-R71 Gy). Frequency and low grade (⩾ 1) incontinence were associated to low and intermediate dose-surface parameters (R13-R41Gy). Frequency showed a parallel behaviour (a=1) while dysuria, haematuria and incontinence showed a more serial behaviour (a=4 to a ⩾ 100). Relative dose-surface showed stronger dose-symptom associations.

CONCLUSIONS

For certain endpoints, the multiple-event and event-count models provide stronger correlates over peak-symptom models. Accounting for multiple events may be advantageous for a more complete understanding of urinary dose-symptom relationships.

Delineating the inner bladder surface using uniform contractions from the outer surface under variable bladder filling conditions

OBJECTIVE

To evaluate the methods to delineate the inner bladder (IB) surface using a uniform contraction from the outer bladder (OB) surface, assuming the bladder wall (BW) is either of constant thickness, constant volume or variable volume.

METHODS

14 prostate intensity-modulated radiotherapy patients with 2 planning CTs were identified. For both CTs, OB was delineated using model-based segmentation. IB was delineated manually. Then, using uniform contractions from OB, the position of IB was approximated using a: 2.5-mm contraction, patient-specific contraction, patient-specific constant wall volume method and variable wall volume method. The structures created using those strategies were compared against the manual IB contours using geometric and dosimetric indices.

RESULTS

In the presence of variable bladder filling, use of a generic or patient-specific constant contraction resulted in a significant overestimation of IB volume (+12 and +13 cm(3), respectively; p < 0.001) that was inversely correlated with the difference in urine volume between the scans (R(2) > 0.86). Mean differences across 95% of IB surfaces were ≤2 mm for methods using either constant or variable wall volume. Mean dose-volume histogram (DVH) differences were <1 cm(3) across the whole BW DVH when using the method that assumed a variable wall volume.

CONCLUSION

The variable volume BW model provided the best approximation of the IB surface position under varying filling conditions, based on geometric and dosimetric indices.

ADVANCES IN KNOWLEDGE

Use of the equation derived in this research provides a quick and accurate method to delineate the hollow BW on serial imaging for the purposes of dose reconstruction.

Automatic CT simulation optimization for radiation therapy: A general strategy

PURPOSE

In radiation therapy, x-ray computed tomography (CT) simulation protocol specifications should be driven by the treatment planning requirements in lieu of duplicating diagnostic CT screening protocols. The purpose of this study was to develop a general strategy that allows for automatically, prospectively, and objectively determining the optimal patient-specific CT simulation protocols based on radiation-therapy goals, namely, maintenance of contouring quality and integrity while minimizing patient CT simulation dose.

METHODS

The authors proposed a general prediction strategy that provides automatic optimal CT simulation protocol selection as a function of patient size and treatment planning task. The optimal protocol is the one that delivers the minimum dose required to provide a CT simulation scan that yields accurate contours. Accurate treatment plans depend on accurate contours in order to conform the dose to actual tumor and normal organ positions. An image quality index, defined to characterize how simulation scan quality affects contour delineation, was developed and used to benchmark the contouring accuracy and treatment plan quality within the predication strategy. A clinical workflow was developed to select the optimal CT simulation protocols incorporating patient size, target delineation, and radiation dose efficiency. An experimental study using an anthropomorphic pelvis phantom with added-bolus layers was used to demonstrate how the proposed prediction strategy could be implemented and how the optimal CT simulation protocols could be selected for prostate cancer patients based on patient size and treatment planning task. Clinical IMRT prostate treatment plans for seven CT scans with varied image quality indices were separately optimized and compared to verify the trace of target and organ dosimetry coverage.

RESULTS

Based on the phantom study, the optimal image quality index for accurate manual prostate contouring was 4.4. The optimal tube potentials for patient sizes of 38, 43, 48, 53, and 58 cm were 120, 140, 140, 140, and 140 kVp, respectively, and the corresponding minimum CTDIvol for achieving the optimal image quality index 4.4 were 9.8, 32.2, 100.9, 241.4, and 274.1 mGy, respectively. For patients with lateral sizes of 43-58 cm, 120-kVp scan protocols yielded up to 165% greater radiation dose relative to 140-kVp protocols, and 140-kVp protocols always yielded a greater image quality index compared to the same dose-level 120-kVp protocols. The trace of target and organ dosimetry coverage and the γ passing rates of seven IMRT dose distribution pairs indicated the feasibility of the proposed image quality index for the predication strategy.

CONCLUSIONS

A general strategy to predict the optimal CT simulation protocols in a flexible and quantitative way was developed that takes into account patient size, treatment planning task, and radiation dose. The experimental study indicated that the optimal CT simulation protocol and the corresponding radiation dose varied significantly for different patient sizes, contouring accuracy, and radiation treatment planning tasks.

Preliminary toxicity analysis of 3-dimensional conformal radiation therapy versus intensity modulated radiation therapy on the high-dose arm of the Radiation Therapy Oncology Group 0126 prostate cancer trial

PURPOSE

To give a preliminary report of clinical and treatment factors associated with toxicity in men receiving high-dose radiation therapy (RT) on a phase 3 dose-escalation trial.

METHODS AND MATERIALS

The trial was initiated with 3-dimensional conformal RT (3D-CRT) and amended after 1 year to allow intensity modulated RT (IMRT). Patients treated with 3D-CRT received 55.8 Gy to a planning target volume that included the prostate and seminal vesicles, then 23.4 Gy to prostate only. The IMRT patients were treated to the prostate and proximal seminal vesicles to 79.2 Gy. Common Toxicity Criteria, version 2.0, and Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer late morbidity scores were used for acute and late effects.

RESULTS

Of 763 patients randomized to the 79.2-Gy arm of Radiation Therapy Oncology Group 0126 protocol, 748 were eligible and evaluable: 491 and 257 were treated with 3D-CRT and IMRT, respectively. For both bladder and rectum, the volumes receiving 65, 70, and 75 Gy were significantly lower with IMRT (all P<.0001). For grade (G) 2+ acute gastrointestinal/genitourinary (GI/GU) toxicity, both univariate and multivariate analyses showed a statistically significant decrease in G2+ acute collective GI/GU toxicity for IMRT. There were no significant differences with 3D-CRT or IMRT for acute or late G2+ or 3+ GU toxicities. Univariate analysis showed a statistically significant decrease in late G2+ GI toxicity for IMRT (P=.039). On multivariate analysis, IMRT showed a 26% reduction in G2+ late GI toxicity (P=.099). Acute G2+ toxicity was associated with late G3+ toxicity (P=.005). With dose-volume histogram data in the multivariate analysis, RT modality was not significant, whereas white race (P=.001) and rectal V70 ≥15% were associated with G2+ rectal toxicity (P=.034).

CONCLUSIONS

Intensity modulated RT is associated with a significant reduction in acute G2+ GI/GU toxicity. There is a trend for a clinically meaningful reduction in late G2+ GI toxicity with IMRT. The occurrence of acute GI toxicity and large (>15%) volumes of rectum >70 Gy are associated with late rectal toxicity.

Dosimetric evaluation of intensity modulated radiotherapy and 4-field 3-d conformal radiotherapy in prostate cancer treatment

OBJECTIVE

The purpose of this dosimetric study is the targeted dose homogeneity and critical organ dose comparison of 7-field Intensity Modulated Radiotherapy (IMRT) and 3-D 4-field conformal radiotherapy.

STUDY DESIGN

Cross sectional study.

MATERIAL AND METHODS

Twenty patients with low and moderate risk prostate cancer treated at Gülhane Military Medical School Radiation Oncology Department between January 2009 and December 2009 are included in this study. Two seperate dosimetric plans both for 7-field IMRT and 3D-CRT have been generated for each patient to comparatively evaluate the dosimetric status of both techniques and all the patients received 7-field IMRT.

RESULTS

Dose-comparative evaluation of two techniques revealed the superiority of IMRT technique with statistically significantly lower femoral head doses along with reduced critical organ dose-volume parameters of bladder V60 (the volume receiving 60 Gy) and rectal V40 (the volume receiving 40 Gy) and V60.

CONCLUSION

It can be concluded that IMRT is an effective definitive management tool for prostate cancer with improved critical organ sparing and excellent dose homogenization in target organs of prostate and seminal vesicles.

Dosimetric comparison of standard three-dimensional conformal radiotherapy followed by intensity-modulated radiotherapy boost schedule (sequential IMRT plan) with simultaneous integrated boost-IMRT (SIB IMRT) treatment plan in patients with localized carcinoma prostate

Aims:

Dosimeteric and radiobiological comparison of two radiation schedules in localized carcinoma prostate: Standard Three-Dimensional Conformal Radiotherapy (3DCRT) followed by Intensity Modulated Radiotherapy (IMRT) boost (sequential-IMRT) with Simultaneous Integrated Boost IMRT (SIB-IMRT).

Material and Methods:

Thirty patients were enrolled. In all, the target consisted of PTV P + SV (Prostate and seminal vesicles) and PTV LN (lymph nodes) where PTV refers to planning target volume and the critical structures included: bladder, rectum and small bowel. All patients were treated with sequential-IMRT plan, but for dosimetric comparison, SIB-IMRT plan was also created. The prescription dose to PTV P + SV was 74 Gy in both strategies but with different dose per fraction, however, the dose to PTV LN was 50 Gy delivered in 25 fractions over 5 weeks for sequential-IMRT and 54 Gy delivered in 27 fractions over 5.5 weeks for SIB-IMRT. The treatment plans were compared in terms of dose–volume histograms. Also, Tumor Control Probability (TCP) and Normal Tissue Complication Probability (NTCP) obtained with the two plans were compared.

Results:

The volume of rectum receiving 70 Gy or more (V > 70 Gy) was reduced to 18.23% with SIB-IMRT from 22.81% with sequential-IMRT. SIB-IMRT reduced the mean doses to both bladder and rectum by 13% and 17%, respectively, as compared to sequential-IMRT. NTCP of 0.86 ± 0.75% and 0.01 ± 0.02% for the bladder, 5.87 ± 2.58% and 4.31 ± 2.61% for the rectum and 8.83 ± 7.08% and 8.25 ± 7.98% for the bowel was seen with sequential-IMRT and SIB-IMRT plans respectively.

Conclusions:

For equal PTV coverage, SIB-IMRT markedly reduced doses to critical structures, therefore should be considered as the strategy for dose escalation. SIB-IMRT achieves lesser NTCP than sequential-IMRT.

The contribution of the cone beam Kv CT (CBKvCT) to the reduction in toxicity of prostate cancer treatment with external 3D radiotherapy

OBJECTIVE

Show that verification through cone beam Kv CT (CBKvCT) in a series of patients treated with 3D external radiotherapy (3DRT) for prostate cancer (PC) is related to a reduction in acute and late toxicity levels.

MATERIALS AND METHOD

A retrospective, non-randomized study of two homogeneous groups of patients treated between 2005 and 2008, 46 were verified using electronic portal devices (EPIDs) and 48 through CBKvCT. They received 3DRT for localized PC (T1-T3N0M0) and were prescribed the same doses. Treatment was simulated and planned with the same criteria with the same equipment with a median follow-up time of 24 months (12-54 months). Urinary and gastrointestinal toxicity was determined using Common Toxicity Criteria scale, version 4 and RTOG scales. Statistical analysis of data was performed where p < 0.005 being significative.

RESULTS AND DISCUSSION

With an overall median follow-up time of 24 months, the levels of proctitis were, respectively, 19.56, 15.21 and 15.2 % in the first group, compared with 4.17, 2.08 and 8.33 % in the second. Statistically, less total and late proctitis, late rectal bleeding, anal fissure, total and acute haematuria, total and acute urinary frequency and total urinary incontinence was observed. No statistically significant evidence of a lowering in toxicity neither in terms of acute and late dysuria nor of a relationship to the TNM, Gleason or PSA or in the grade of stability.

CONCLUSION

Verification through CBKvCT in this series is associated with a statistically significant lowering toxicity. This justifies its use. Greater monitoring would be necessary to assess the impact of verification at the level of biochemical control.

Clinical outcome of patients treated with 3D conformal radiation therapy (3D-CRT) for prostate cancer on RTOG 9406

PURPOSE

Report of clinical cancer control outcomes on Radiation Therapy Oncology Group (RTOG) 9406, a three-dimensional conformal radiation therapy (3D-CRT) dose escalation trial for localized adenocarcinoma of the prostate.

METHODS AND MATERIALS

RTOG 9406 is a Phase I/II multi-institutional dose escalation study of 3D-CRT for men with localized prostate cancer. Patients were registered on five sequential dose levels: 68.4 Gy, 73.8 Gy, 79.2 Gy, 74 Gy, and 78 Gy with 1.8 Gy/day (levels I-III) or 2.0 Gy/day (levels IV and V). Neoadjuvant hormone therapy (NHT) from 2 to 6 months was allowed. Protocol-specific, American Society for Therapeutic Radiation Oncology (ASTRO), and Phoenix biochemical failure definitions are reported.

RESULTS

Thirty-four institutions enrolled 1,084 patients and 1,051 patients are analyzable. Median follow-up for levels I, II, III, IV, and V was 11.7, 10.4, 11.8, 10.4, and 9.2 years, respectively. Thirty-six percent of patients received NHT. The 5-year overall survival was 90%, 87%, 88%, 89%, and 88% for dose levels I-V, respectively. The 5-year clinical disease-free survival (excluding protocol prostate-specific antigen definition) for levels I-V is 84%, 78%, 81%, 82%, and 82%, respectively. By ASTRO definition, the 5-year disease-free survivals were 57%, 59%, 52%, 64% and 75% (low risk); 46%, 52%, 54%, 56%, and 63% (intermediate risk); and 50%, 34%, 46%, 34%, and 61% (high risk) for levels I-V, respectively. By the Phoenix definition, the 5-year disease-free survivals were 68%, 73%, 67%, 84%, and 80% (low risk); 70%, 62%, 70%, 74%, and 69% (intermediate risk); and 42%, 62%, 68%, 54%, and 67% (high risk) for levels I-V, respectively.

CONCLUSION

Dose-escalated 3D-CRT yields favorable outcomes for localized prostate cancer. This multi-institutional experience allows comparison to other experiences with modern radiation therapy.

Patient positioning variations to reduce dose to normal tissues during 3D conformal radiotherapy for high-risk prostate cancer

BACKGROUND AND PURPOSE

The goal of this work was to assess optimal treatment positioning of 3D conformal radiotherapy (3DCRT) for high-risk prostate cancer patients.

PATIENTS AND METHODS

Treatment plans of 25 patients in different patient positions were evaluated: with knee and ankle support (KAS) in the supine position and with a belly board (BB) in the prone position both with full (FB) and empty bladder (EB). Planning target volumes (PTVs) for pelvis, prostate and vesicles, prostate, and organs at risk (OARs) were delineated. Dose and overlapping volumes were evaluated.

RESULTS

Overlapping volumes were significantly smaller with a FB than with an EB. No significant differences were found in overlapping volumes with respect to patient fixation systems, but the percentage values of dose to the OARs showed significantly better results employing KAS than a BB. A FB reduced the dose volumes to the OARs. Comparison with respect to circumference of abdomen (CA) showed significantly smaller overlapping at large CA in most of the cases.

CONCLUSION

Supine position is suggested with KAS combined with a FB (especially in cases of larger CA) when using 3DCRT with planning technique modification for high-risk prostate cancer patients to reduce the dose of OARs, based on our results.

Rectal planning risk volume correlation with acute and late toxicity in 3-dimensional conformal radiation therapy for prostate cancer

The purpose of this study was to evaluate rectum motion during 3-Dimensional conformal radiation therapy (3D-CRT) in prostate cancer patients, to derive a planning volume at risk (PRV) and to correlate the PRV dose-volume histograms (DVH) with treatment complications.This study was conducted in two phases. Initially, the PRV was defined prospectively in 50 consecutive prostate cancer patients (Group 1) who received a radical course of 3-D CRT. Then, the obtained PRV was used in the radiotherapy planning of these same 50 patients plus another 59 prostate cancer patients (Group 2) previously treated between 2004 and 2008. All these patients' data, including the rectum and PRV DVHs, were correlated to acute and late complications, according to the Common Toxicity Criteria (CTC) v4.0.The largest displacement occurred in the anterior axis. Long-term gastrointestinal (GI) complications grade ≥ 2 were seen in 9.2% of the cases. Factors that influenced acute GI reactions were: doses at 25% (p 5 0.011) and 40% (p 5 0.005) of the rectum volume and at 40% of the PRV (p 5 0.012). The dose at 25% of the rectum volume (p 5 0.033) and acute complications ≥ grade 2 (p 5 0.018) were prognostic factors for long-term complications. The PRV DVH did not correlate with late toxicity. The rectum showed a significant inter-fraction motion during 3D-CRT for prostate cancer. PRV dose correlated with acute gastrointestinal complications and may be a useful tool to predict and reduce their occurrence.

Do intermediate radiation doses contribute to late rectal toxicity? An analysis of data from radiation therapy oncology group protocol 94-06

PURPOSE

To investigate whether the volumes of rectum exposed to intermediate doses, from 30 to 50 Gy, contribute to the risk of Grade ≥ 2 late rectal toxicity among patients with prostate cancer receiving radiotherapy.

METHODS AND MATERIALS

Data from 1009 patients treated on Radiation Therapy Oncology Group protocol 94-06 were analyzed using three approaches. First, the contribution of intermediate doses to a previously published fit of the Lyman-Kutcher-Burman (LKB) normal tissue complication probability (NTCP) model was determined. Next, the extent to which intermediate doses provide additional risk information, after taking the LKB model into account, was investigated. Third, the proportion of rectum receiving doses higher than a threshold, VDose, was computed for doses ranging from 5 to 85 Gy, and a multivariate Cox proportional hazards model was used to determine which of these parameters were significantly associated with time to Grade ≥ 2 late rectal toxicity.

RESULTS

Doses <60 Gy had no detectable impact on the fit of the LKB model, as expected on the basis of the small estimate of the volume parameter (n = 0.077). Furthermore, there was no detectable difference in late rectal toxicity among cohorts with similar risk estimates from the LKB model but with different volumes of rectum exposed to intermediate doses. The multivariate Cox proportional hazards model selected V75 as the only value of VDose significantly associated with late rectal toxicity.

CONCLUSIONS

There is no evidence from these data that intermediate doses influence the risk of Grade ≥ 2 late rectal toxicity. Instead, the critical doses for this endpoint seem to be ≥ 75 Gy. It is hypothesized that cases of Grade ≥ 2 late rectal toxicity occurring among patients with V75 less than approximately 12% may be due to a "background" level of risk, likely due mainly to biological factors.

Physical and clinical implications of radiotherapy treatment of prostate cancer using a full bladder protocol

PURPOSE

To assess the dosimetric and clinical implication when applying the full bladder protocol for the treatment of the localized prostate cancer (PCA).

PATIENTS AND METHODS

A total of 26 consecutive patients were selected for the present study. Patients underwent two series of CT scans: the day of the simulation and after 40 Gy. Each series consisted of two consecutive scans: (1) full bladder (FB) and (2) empty bladder (EB). The contouring of clinical target volumes (CTVs) and organs at risk (OAR) were compared to evaluate organ motion. Treatment plans were compared by dose distribution and dose-volume histograms (DVH).

RESULTS

CTV shifts were negligible in the laterolateral and superior-inferior directions (the maximum shift was 1.85 mm). Larger shifts were recorded in the anterior-posterior direction (95% CI, 0.83-4.41 mm). From the dosimetric point of view, shifts are negligible: the minimum dose to the CTV was 98.5% (median; 95%CI, 95-99%). The potential advantage for GU toxicity in applying the FB treatment protocol was measured: the ratio between full and empty bladder dose-volume points (selected from our protocol) is below 0.61, excluding the higher dose region where DVHs converge.

CONCLUSION

Having a FB during radiotherapy does not affect treatment effectiveness, on the contrary it helps achieve a more favorable DVH and lower GU toxicities.

The effect of delineation method and observer variability on bladder dose-volume histograms for prostate intensity modulated radiotherapy

PURPOSE

To quantify the effect of delineation method on bladder DVH, observer variability (OV) and contouring time for prostate IMRT plans.

MATERIALS AND METHODS

Planning CT scans and IMRT plans of 30 prostate cancer patients were anonymized. For 20 patients, 1 observer delineated the bladder using 9 methods. The effect of delineation method on the DVH curve, discrete dose levels and delineation time was quantified. For the 10 remaining CTs, 6 observers delineated bladder wall using 4 methods. Observer-based volume variation and intraclass correlation coefficient (ICC) were used to describe the dosimetric effects of OV.

RESULTS

Manual delineation of the bladder wall (BW_m) was significantly slower than any other method (mean: 20 min vs. ≤ 13 min) and the dosimetric effect of OV was significantly larger (V70 Gy ICC: 0.78 vs. 0.98). Only volumes created using a 2.5mm contraction from the outer surface, and a method providing a consistent wall volume, showed no notable dosimetric differences from BW_m in both absolute and relative volume.

CONCLUSIONS

Automatic contractions from the outer surface provide quicker, more reproducible and reasonably accurate substitutes for BW_m. The widespread use of automatic contractions to create a bladder wall volume would assist in the consistent application of IMRT dose constraints and the interpretation of reported dose.

Reirradiation of prostate cancer with rectum preservation: eradicative high-dose-rate brachytherapy with natural type hyaluronate injection

INTRODUCTION

Reirradiation of locally recurrent prostate cancer after radiotherapy is limited because of its toxicity to the rectum that is closely adjacent to the prostate. To solve geometric anatomic constraints, including rectal size and distance from the prostate, we developed a technique that modifies the geometry by noninvasive direct intervention.

METHODS AND MATERIALS

In a patient with local recurrence of prostate cancer at 18 months after initial radiotherapy of 61.8 GyE(LQ2,3) (gray equivalent in 2 Gy/fraction at α/β=3 calculated with linear quadratic [LQ] model) to the prostate, we prescribed 16 Gy (60.8 GyE(LQ2,3) or 78.2 GyE(LQ2,1.6)) of reirradiation by high-dose-rate brachytherapy, using a bolus injection of native-type hyaluronate to create and maintain a distance between the prostate and the rectum and decrease rectal size during treatment.

RESULTS

The procedure was achieved in 10min, without complications. Rectal D(2cc) of the reirradiation was 5.58 Gy (9.58 GyE(LQ2,3)). Compared with the initial radiation, the gel injection resulted in an improved therapeutic ratio. The patient was regularly followed up at our clinic; at over 3.5 years after reirradiation, there was no evidence of recurrence or radiation-related toxicities greater than Grade 2, maintaining a nadir prostate-specific antigen level of 0.03 ng/mL without hormonal therapy.

CONCLUSION

We consider that this technique is useful for achieving safe and curative reirradiation of prostate cancer.

Low-dose rate brachytherapy for men with localized prostate cancer

BACKGROUND

Localized prostate cancer is a slow growing tumor for many years for the majority of affected men. Low-dose rate brachytherapy (LDR-BT) is short-distance radiotherapy using low-energy radioactive sources. LDR-BT has been recommended for men with low risk localized prostate cancer.

OBJECTIVES

To assess the benefit and harm of LDR-BT compared to radical prostatectomy (RP), external beam radiotherapy (EBRT), and no primary therapy (NPT) in men with localized prostatic cancer.

SEARCH STRATEGY

The Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (from 1950), and EMBASE (from 1980) were searched in June 2010 as well as online trials registers and reference lists of reviews.

SELECTION CRITERIA

Randomized, controlled trials comparing LDR-BT versus RP, EBRT, and NPT in men with clinically localized prostate cancer.

DATA COLLECTION AND ANALYSIS

Data on study methods, participants, treatment regimens, observation period and outcomes were recorded by two reviewers independently.

MAIN RESULTS

We identified only one RCT (N = 200; mean follow up 68 months). This trial compared LDR-BT and RP. The risk of bias was deemed high. Primary outcomes (overall survival, cause-specific mortality, or metastatic-free survival) were not reported. Biochemical recurrence-free survival at 5 years follow up was not significantly different between LDR-BT (78/85 (91.8%)) and RP (81/89 (91.0%)); P = 0.875; relative risk 0.92 (95% CI: 0.35 to 2.42).For severe adverse events reported at 6 months follow up, results favored LDR-BT for urinary incontinence (LDR-BT 0/85 (0.0%) versus RP 16/89 (18.0%); P < 0.001; relative risk 0) and favored RP for urinary irritation (LDR-BT 68/85 (80.0%) versus RP 4/89 (4.5%); P < 0.001; relative risk 17.80, 95% CI 6.79 to 46.66). The occurrence of urinary stricture did not significantly differ between the treatment groups (LDR-BT 2/85 (2.4%) versus RP 6/89 (6.7%); P = 0.221; relative risk 0.35, 95% CI: 0.07 to 1.68). Long-term information was not available.We did not identify significant differences of mean scores between treatment groups for patient-reported outcomes function and bother as well as generic health-related quality of life.

AUTHORS' CONCLUSIONS

Low-dose rate brachytherapy did not reduce biochemical recurrence-free survival versus radical prostatectomy at 5 years. For short-term severe adverse events, low-dose rate brachytherapy was significantly more favorable for urinary incontinence, but radical prostatectomy was significantly more favorable for urinary irritation. Evidence is based on one RCT with high risk of bias.

Single-arc volumetric-modulated arc therapy can provide dose distributions equivalent to fixed-beam intensity-modulated radiation therapy for prostatic irradiation with seminal vesicle and/or lymph node involvement

OBJECTIVES

Volumetric-modulated arc therapy (VMAT) is becoming an increasingly utilised modality for treating a variety of anatomical sites. However, the efficacy of single-arc VMAT to treat prostate cancer suspicious for extraprostatic extension was heretofore unknown. In this work, we report our institutional experience with single-arc VMAT and fixed-beam intensity-modulated radiation therapy (IMRT) for prostate cancer patients treated for seminal vesicle and/or lymph node involvement.

METHODS

Single-arc VMAT and 7- or 9-field IMRT treatment plans were compared for 10 prostate cancer patients treated for seminal vesicle involvement and/or lymph node involvement. All treatment plans were constructed using the Philips Pinnacle treatment planning system (v.9.0, Fitchburg, WI) and delivered on an Elekta Infinity radiotherapy accelerator (Crawley, UK). Resulting plans were compared using metrics that characterised dosimetry and delivery efficiency.

RESULTS

No statistically significant differences in target coverage, target homogeneity or normal tissue doses were noted between the plans (p>0.05). For prostate patients treated for seminal vesicle involvement, VMAT plans were delivered in 1.4±0.1 min (vs 9.5±2.4 min for fixed-beam IMRT) (p<0.01) and required approximately 20% fewer monitor units (p=0.01). For prostate patients treated for lymph node involvement, VMAT plans were delivered in 1.4±0.1 min (vs 11.7±1.3 min for fixed-beam IMRT) (p<0.01) and required approximately 45% fewer monitor units (p<0.01).

CONCLUSION

Single-arc VMAT plans were dosimetrically equivalent to fixed-beam IMRT plans with significantly improved delivery efficiency.

Rectal dose constraints for intensity modulated radiation therapy of the prostate

Prostate dose escalation appears to have resulted in increased cancer control. Such escalation has been made possible by the ability to deliver more conformal treatment that spares normal tissue from the higher radiation doses. The supposition is that this has enabled higher doses, but without an increase in toxicity. The most disabling toxicity in prostate cancer radiotherapy is rectal. We evaluated the current status of conformal radiation and late rectal toxicity with the goal of determining whether reasonable rectal dose and volume constraints can be determined. Although the literature is inexact, we believe that some generalized constraints can be recommended and show that those recommendations are consistent with what is being used at experienced centers.

Comparison of three-dimensional conformal irradiation techniques for prostate cancer using a low-energy (6 MV) photon beam

Purpose: To evaluate composite coplanar and non-coplanar three-dimensional conformal techniques (3D-CRT) for external-beam prostate radiotherapy using a low-energy (6 MV) photon beam.

Methods and Materials: For treatment-planning purposes, three different planning target volumes (PTV) were defined for ten patients with prostate cancer and as follows: PTV1 (pelvis), PTV2 (prostate + seminal vesicles + 1 cm margin) and PTV3 (prostate + 1 cm margin). Conformal techniques of 2, 3, 4, 5 (coplanar) and 6 (non-coplanar) field techniques have been considered and combined to produce five different plan combinations (i.e. techniques A, B, C, D and E). Treatment plans were generated with a prescription dose of 75 Gy to PTV3, 65 Gy to PTV2 and 45 Gy to PTV1 and were assessed on the basis of 3D dose distributions and dose-volume histograms (DVHs). Normal tissue-dose constraints for the relevant organs at risk (OARs), that is, rectum, bladder and femoral heads, were also considered.

Results: Findings show that all five treatment-plan combinations result in adequate PTV coverage and acceptable OAR irradiated volumes. The greatest rectal spacing in the high-dose region is achieved by technique C; all techniques achieve this, except for technique A, and give approximately the same fraction of volume (of rectum) that receives a dose of 50 Gy (V50) and 60 Gy (V60). When considering the bladder, techniques B, D and E give the best bladder sparing with small absolute differences, whereas technique A results in the lowest dose for femoral heads. Technique E appears to give the best compromise for all three considered OARs, provided the PTV is adequately covered.

Conclusions: Even though the optimum photon-beam energy for conformal prostate radiotherapy is greater than 10 MV, our study shows that a good sparing of OAR can be achieved even with a lower-energy beam (6 MV) and the appropriate plan combination and that the dose to prostate can be as high as 75 Gy.

Rectal bleeding after high-dose-rate brachytherapy combined with hypofractionated external-beam radiotherapy for localized prostate cancer: the relationship between dose-volume histogram parameters and the occurrence rate

PURPOSE

To determine the predictive risk factors for Grade 2 or worse rectal bleeding after high-dose-rate brachytherapy (HDR-BT) combined with hypofractionated external-beam radiotherapy (EBRT) for prostate cancer using dose-volume histogram analysis.

METHODS AND MATERIALS

The records of 216 patients treated with HDR-BT combined with EBRT were analyzed. The treatment protocols for HDR-BT were 5 Gy × five times in 3 days or 7 Gy × three, 10.5 Gy × two, or 9 Gy × two in 2 days. The EBRT doses ranged from 45 to 51 Gy with a fractional dose of 3 Gy.

RESULTS

In 20 patients Grade 2 or worse rectal bleeding developed, and the cumulative incidence rate was 9% at 5 years. By converting the HDR-BT and EBRT radiation doses into biologic effective doses (BED), the BED(3) at rectal volumes of 5% and 10% in the patients who experienced bleeding were significantly higher than those in the remaining 196 patients. Univariate analysis showed that a higher rectal BED(3-5%) and the use of fewer needles in brachytherapy were correlated with the incidence of bleeding, but BED(3-5%) was found to be the only significant factor on multivariate analysis.

CONCLUSIONS

The radiation dose delivered to small rectal lesions as 5% is important for predicting Grade 2 or worse rectal bleeding after HDR-BT combined with EBRT for prostate cancer.

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.

Estimation of α/β for late rectal toxicity based on RTOG 94-06

PURPOSE

To estimate α/β, the parameter ratio from the linear-quadratic (LQ) model, for Grade ≥2 late rectal toxicity among patients treated on Radiation Therapy Oncology Group (RTOG) protocol 94-06; and to determine whether correcting the rectal dose-volume histogram (DVH) for differences in dose per fraction, based on the LQ model, significantly improves the fit to these data of the Lyman-Kutcher-Burman (LKB) normal-tissue complication probability (NTCP) model.

METHODS AND MATERIALS

The generalized LKB model was fitted to the Grade ≥2 late rectal toxicity data in two ways: by using DVHs representing physical dose to rectum, and by using a modified approach in which dose bins in the rectal DVH were corrected for differences in dose per fraction using the LQ model, with α/β estimated as an additional unknown parameter. The analysis included only patients treated with the same treatment plan throughout radiotherapy, so that the dose per fraction to each voxel of rectum could be determined from the DVH. The likelihood ratio test was used to assess whether the fit of the LQ-corrected model was significantly better than the fit of the LKB model based on physical doses to rectum.

RESULTS

The analysis included 509 of the 1,084 patients enrolled on RTOG 94-06. The estimate of α/β from the LQ-corrected LKB model was 4.8 Gy, with 68% confidence interval 0.6 Gy to 46 Gy. The fit was not significantly different from the fit of the LKB model based on physical dose to rectum (p = 0.236).

CONCLUSIONS

The estimated fractionation sensitivity for Grade ≥2 late rectal toxicity is consistent with values of α/β for rectum found previously in human beings and in rodents. However, the confidence interval is large, and there is no evidence that LQ correction of the rectal DVH significantly changes the fit or predictions of the LKB model for this endpoint.

Emerging Technologies in Prostate Cancer Radiation Therapy: Improving the Therapeutic Window

Background

Radiation therapy is a standard of care in the treatment of prostate cancer. Relatively recent advances in technologies in the delivery of radiation therapy are altering our current approach to treatment of prostate cancer.

Methods

This review discusses the results of retrospective, prospective, and randomized clinical trials that have evaluated clinical outcomes in prostate cancer treated with newer radiation therapy technologies.

Results

Randomized trials have demonstrated that higher doses of radiation therapy improve clinical outcomes but with increased toxicity to normal tissue. The introduction of more conformal radiation therapy techniques such as intensity-modulated radiation therapy, proton therapy, stereotactic body radiotherapy, and brachytherapy have allowed for further dose escalation with simultaneous reduction in toxicity. However, use of more conformal treatments requires a better understanding of prostate motion and the ability to track prostate movements in real time.

Conclusions

Technological advancements have improved radiation dose delivery to the prostate and have reduced normal tissue toxicity. Randomized trials are warranted to ultimately evaluate clinical benefit and outcomes.

Dosimetric comparison between 3D conformal and intensity-modulated radiation therapy for prostate cancer

Background and Purpose: Intensity-modulated radiation therapy (IMRT) is considered by many to be the standard of care in the delivery of external-beam radiotherapy treatments to the prostate. The purpose of this study is to assess the validity of the purported benefits of IMRT.

Materials and Methods: Treatment plans were produced for 10 patients using both 3D conformal radiation therapy (3D-CRT) and IMRT, utilising the dose constraints recommended by the Radiation Therapy Oncology Group (RTOG) 0415 protocol. Three IMRT modalities used in this study were linear accelerator based IMRT, helical tomotherapy, and serial tomotherapy. The prescription to the target, 76 Gy, was the same for all plans.

Results: In general the 3D-CRT plans satisfied the RTOG criteria for planning target volume (PTV) coverage, and met or bettered the dose criteria for the organs at risk. PTV coverage was more homogeneous for the IMRT plans than the 3D-CRT plans but not significantly improved.

Conclusions: Technically, because the IMRT plans required greater effort for the optimisation, longer treatment times and higher monitor units, the use of IMRT for the fulfilment of the protocol’s dosimetric goals was not justified using these constraints.

A systematic methodology review of phase I radiation dose escalation trials

BACKGROUND AND PURPOSE

The purpose of this review is to evaluate the methodology used in published phase I radiotherapy (RT) dose escalation trials. A specific emphasis was placed on the frequency of reporting late complications as endpoint.

MATERIALS AND METHODS

We performed a systematic literature review using a predefined search strategy to identify all phase I trials reporting on external radiotherapy dose escalation in cancer patients.

RESULTS

Fifty-three trials (phase I: n = 36, phase I-II: n = 17) fulfilled the inclusion criteria. Of these, 20 used a modified Fibonacci design for the RT dose escalation, but 32 did not specify a design. Late toxicity was variously defined as > 3 months (n = 43) or > 6 months (n = 3) after RT, or not defined (n = 7). In only nine studies the maximum tolerated dose (MTD) was related to late toxicity, while only half the studies reported the minimum follow-up period for dose escalation (n = 26).

CONCLUSION

In phase I RT trials, late complications are often not taken into account and there is currently no consensus on the methodology used for radiation dose escalation studies. We therefore propose a decision-tree algorithm which depends on the endpoint selected and whether a validated early surrogate endpoint is available, in order to choose the most appropriate study design.