Intensity-modulated radiation therapy (IMRT) for prostate cancer with the use of a rectal balloon for prostate immobilization: acute toxicity and dose-volume analysis

Towards real-time PGS range monitoring in proton therapy of prostate cancer

Proton therapy of prostate cancer (PCPT) was linked with increased levels of gastrointestinal toxicity in its early use compared to intensity-modulated radiation therapy (IMRT). The higher radiation dose to the rectum by proton beams is mainly due to anatomical variations. Here, we demonstrate an approach to monitor rectal radiation exposure in PCPT based on prompt gamma spectroscopy (PGS). Endorectal balloons (ERBs) are used to stabilize prostate movement during radiotherapy. These ERBs are usually filled with water. However, other water solutions containing elements with higher atomic numbers, such as silicon, may enable the use of PGS to monitor the radiation exposure of the rectum. Protons hitting silicon atoms emit prompt gamma rays with a specific energy of 1.78 MeV, which can be used to monitor whether the ERB is being hit. In a binary approach, we search the silicon energy peaks for every irradiated prostate region. We demonstrate this technique for both single-spot irradiation and real treatment plans. Real-time feedback based on the ERB being hit column-wise is feasible and would allow clinicians to decide whether to adapt or continue treatment. This technique may be extended to other cancer types and organs at risk, such as the oesophagus.

Clinical effects of rectal retractor application in prostate cancer radiotherapy

Background: Radiation-induced rectal toxicities remain as a major risk during prostate radiotherapy. One approach to the reduction of rectal radiation dose is to physically increase the distance between the rectal wall and prostate. Therefore, the aim of this study was to evaluate whether the application of the rectal retractor (RR) can reduce rectal dose and toxicity in prostate cancer 3-dimensional conformal radiotherapy (3D-CRT). Methods: Overall, 36 patients with localized prostate cancer were randomized into the 2 groups, 18 patients with RR in-place and 18 without RR. All patients underwent planning computed tomography (CT). Patients were treated with 70 Gy in 35 fractions of 3D-CRT. In the RR group, RR was used during cone-down 20 treatment fractions. Acute and late gastrointestinal (GI) toxicities were assessed using EORTC/RTOG scoring system weekly during radiotherapy, 3, and 12 months after treatment. Device-related events were recorded according to CTCAE version 4.0. Patient characteristics, cancer differences, and dosimetric data for the RR and non-RR groups were compared using a Man-Whitney U test for continuous variables, and Fisher exact test for categorical data. The EORTC/RTOG scores for the 2 groups were compared using Fisher exact test. A P value <0.05 was considered statistically significant. Results: A RR significantly reduced mean dose (Dmean) to the rectum as well as rectal volume receiving 50% to 95% (V50-95%) of prescribed dose. The absolute reduction of rectal Dmean was 10.3 Gy. There was no statistically significant difference in acute GI toxicity between groups during treatment or at 3 months. At 12 months, 2 patients in the RR group and 9 in the control group experienced late grade ≥ 1 GI toxicity (p=0.027). No patients in the RR group reported late grade ≥ 2 GI toxicity, whereas 3 patients in the control group experienced late grade 2 GI toxicity. In the RR group, 6 patients reported grade 1 rectal discomfort and pain according to CTCAE version 4.0. Conclusion: The application of the RR showed a significant rectum sparing effect, resulting in substantially reducing late GI toxicity.

Rectal Dose Is the Other Dosimetric Factor in Addition to Small Bowel for Prediction of Acute Diarrhea during Postoperative Whole-Pelvic Intensity-Modulated Radiotherapy in Gynecologic Patients

Simple Summary

Although the small bowel volume effect for acute diarrhea during radiotherapy has been investigated, no study has reported the influence of rectal dose. We analyzed 108 patients undergoing intensity-modulated radiotherapy after hysterectomy. Acute diarrhea was defined as onset during radiotherapy based on Common Terminology Criteria for Adverse Events (CTCAE) version 3. Both small bowel and rectum dosimetric parameters affected Grade 2 to 3 diarrhea. The high-dose volume effects on the small bowel still play an important role in postoperative intensity-modulated radiotherapy. This is the first large cohort study to demonstrate the role of both IMRT dosimetric factors of the rectum and the small bowel in acute diarrhea in gynecological patients with a previous hysterectomy. A small bowel volume of 39.6 Gy < 60 mL and a mean rectal dose of <32.75 Gy are suggested as constraints to treatment planning.

Abstract

We studied the association of rectal dose with acute diarrhea in patients with gynecologic malignancies undergoing whole-pelvic (WP) intensity-modulated radiotherapy (IMRT). From June 2006 to April 2019, 108 patients with previous hysterectomy who underwent WP IMRT were enrolled in this cohort study. WP irradiation of 39.6–45 Gy/22–25 fractions was initially delivered to the patients. Common Terminology Criteria for Adverse Events (CTCAE) version 3 was used to evaluate acute diarrhea during radiotherapy. Small bowel volume at different levels of isodose curves (Vn%) and mean rectal dose (MRD) were measured for statistical analysis. The multivariate analysis showed that the MRD ≥ 32.75 Gy (p = 0.005) and small bowel volume of 100% prescribed (V100%) ≥ 60 mL (p = 0.008) were independent factors of Grade 2 or higher diarrhea. The cumulative incidence of Grade 2 or higher diarrhea at 39.6 Gy were 70.5%, 42.2%, and 15.0% (p < 0.001) in patients with both high (V100% ≥ 60 mL and MRD ≥ 32.75 Gy), either high, and both low volume-dose factors, respectively. Strict constraints for the rectum/small bowel or image-guided radiotherapy to reduce these doses are suggested.

Dose escalation (81 Gy) with image-guided radiation therapy and volumetric-modulated arc therapy for localized prostate cancer: A retrospective preliminary result

Objectives:

The objective of the study is to report the acute and late toxicity and preliminary results of localized prostate cancer treated with high-dose radiation therapy (RT).

Materials and Methods:

Between March 2010 and October 2018, a total of 53 patients with clinically localized prostate cancer were treated with definitive RT at our institution. All patients were planned to receive a total dose of 81 Gy with the volumetric-modulated arc therapy technique. Patients were stratified by prognostic risk groups based on the National Comprehensive Cancer Network risk classification criteria. Acute and late toxicities were scored by the Radiation Therapy Oncology Group morbidity grading scales. The definition of biochemical failure was using the 2005 ASTRO Phoenix consensus definition. Median follow-up time was 46.5 months (range: 4.7–81.0 months).

Results:

The 3-year biochemical failure-free survival rates for low-, intermediate-, and high-risk group patients were 100%, 87.5%, and 84%, respectively. The 3- and 5-year overall survival rates were 83% and 62%, respectively. Three (5.6%) patients developed Grade II acute gastrointestinal (GI) toxicity. Four (7.5%) patients developed Grade II acute genitourinary (GU) toxicity, and none experienced Grade III or higher acute GI or GU symptoms. One (1.8%) patient developed Grade II or higher late GI toxicity. Six (11.3%) patients experienced Grade II late GU toxicity. No Grade III or higher late GI and GU complications have been observed.

Conclusions:

Data from the current study demonstrated the feasibility of dose escalation with image-guided and volumetric-modulated arc therapy techniques for the treatment of localized prostate cancer. Minimal acute and late toxicities were observed from patients in this study. Long-term prostate-specific antigen controls are comparable to previously published results of high-dose intensity-modulated RT for localized prostate cancer. Based on this favorable outcome, dose escalation (81 Gy) has become the standard treatment for localized prostate cancer at our institution.

Proton therapy- the modality of choice for future radiation therapy management of Prostate Cancer?

BACKGROUND

Proton Therapy (PR) is an emerging treatment for prostate cancer (Pca) patients. However, limited and conflicting data exists regarding its ability to result in fewer bladder and rectal toxicities compared to Photon Therapy (PT), as well as its cost efficiency and plan robustness.

MATERIALS AND METHODS

An electronic literature search was performed to acquire eligible studies published between 2007 and 2018. Studies comparing bladder and rectal dosimetry or Gastrointestinal (GI) and Genitourinary (GU) toxicities between PR and PT, the plan robustness of PR relative to motion and its cost efficiency for Pca patients were assessed.

RESULTS

28 studies were eligible for inclusion in this review. PR resulted in improved bladder and rectal dosimetry but did not manifest as improved GI/GU toxicities clinically compared to PT. PR plans were considered robust when specific corrections, techniques, positioning or immobilisation devices were applied. PR is not cost effective for intermediate risk Pca patients; however PR may be cost effective for younger or high risk Pca patients.

CONCLUSION

PR offers improved bladder and rectal dosimetry compared to PT but this does not specifically translate to improved GI/GU toxicities clinically. The robustness of PR plans is acceptable under specific conditions. PR is not cost effective for all Pca patients.

Long-term outcome of a moderately hypofractionated, intensity-modulated radiotherapy approach using an endorectal balloon for patients with localized prostate cancer

BACKGROUND

Technical advances in radiotherapy delivery have simultaneously enabled dose escalation and enhanced bladder and rectal sparing. However, the optimal radiation fractionation regimen for localized prostate cancer is unclear. Laboratory and clinical evidence suggest that hypofractionation may improve the therapeutic ratio of radiotherapy. We report our institutional outcomes using moderately hypofractionated, intensity-modulated radiotherapy (IMRT), and an endorectal balloon, with emphasis on long-term biochemical control and treatment-related adverse events in patients with localized prostate cancer.

METHODS

Between January 1997 and April 2004, 596 patients with cT1-T3 prostate cancer underwent IMRT using a moderate hypofractionation regimen (76.70 Gy at 2.19 Gy/fraction) with an endorectal balloon. Using D'Amico classification, 226 (37.9%), 264 (44.3%), and 106 (17.8%) patients had low-, intermediate-, or high-risk disease, respectively. The majority of intermediate- and high-risk patients received androgen deprivation therapy. Biochemical relapse-free survival (bRFS) was evaluated using 2005 Phoenix criteria and estimated using the Kaplan-Meier method.

RESULTS

The median follow-up was 62 months. Overall 5- and 10-year bRFS rates were 92.7% and 87.7%. For low-, intermediate-, and high-risk patients, the 5-year bRFS rates were 96.9%, 93.3%, and 82.0%, respectively; the 10-year bRFS rates were 91.4%, 89.3%, and 76.2%, respectively. Prostate-specific antigen, Gleason score, and T stage were significant predictors of bRFS (all P < 0.01). The 5-year rates of severe (≥ Grade 3) adverse events were very low: 1.2% for gastrointestinal events and 1.1% for genitourinary events.

CONCLUSIONS

Long-term outcomes after moderately hypofractionated IMRT are encouraging. Moderate hypofractionation represents a safe, efficacious, alternative regimen in the treatment of localized prostate cancer.

Incidence and Dose-volume Analysis of Acute Bladder Toxicity following Pelvic Radiotherapy

Aims and Background

The authors performed this prospective study to evaluate the incidence of acute bladder toxicity following pelvic radiation therapy and to determine any dosimetric predictors for the toxicity.

Methods and Study Design

Acute bladder toxicity was evaluated weekly by physicians using the Common Terminology Criteria for Adverse Events (CTCAE version 4.0). At the same time, the International Prostate Symptom Score (IPSS) and Overactive Bladder Symptom Score (OABSS) were also assessed by each patient during radiation therapy. We contoured the bladder wall, solid bladder and trigone on the planning computed tomography and analyzed dose-volume histograms to determine which of these could be the most suitable dosimetric predictor.

Results

Of 92 eligible patients, 27 (29%) demonstrated CTCAE grade 2 acute bladder toxicity, with nocturia as the most frequently observed symptom. IPSS demonstrated better agreement with CTCAE than OABSS. In receiver-operating characteristic curve analysis, the largest area under the curve was observed for V20 of both the bladder wall and the bladder.

Conclusions

Acute bladder toxicity during pelvic radiation therapy is not a trivial complication and should be actively investigated. Dose-volume relationships demonstrate that both bladder wall V20 and bladder solid V20 are useful surrogates for identifying patients at high risk of toxicity. The roles of IPSS and OABSS need to be validated in a larger study.

[Doses to organs at risk for conformational and stereotactic radiotherapy: Bladder]

Bladder dose constraints in case of conformational radiotherapy/intensity-modulated radiotherapy and stereotactic radiotherapy are reported from the literature, in particular from the French radiotherapy society RECORAD recommendations, according to the treated pelvic tumor sites. The dose-volume effect on urinary toxicity is not clearly demonstrated, making difficult to establish absolute dose constraints for the bladder. In case of high-dose prostate cancer radiotherapy, the bladder dose constraints are: V60Gy<50% and maximum dose<80Gy for standard fractionation and V60Gy<5%, V48Gy<25% and V41Gy<50% for moderate hypofractionation (20 fractions of 3Gy). In case of prostate stereotactic radiotherapy (five fractions of 7.25Gy), the most frequent dose constraints in the literature are V37Gy<10cm³ and V18Gy<40%. In case of conformational radiotherapy of cervix cancer, postoperative endometrium, anal canal and rectum, the recommendations are V40Gy<40% and D2% lower than the prescribed dose.

Rectal/urinary toxicity after hypofractionated vs conventional radiotherapy in low/intermediate risk localized prostate cancer: systematic review and meta analysis

Purpose

The aim of this review was to compare radiation toxicity in Localized Prostate Cancer (LPC) patients who underwent conventional fractionation (CV), hypofractionated (HYPO) or extreme hypofractionated (eHYPO) radiotherapy. We analyzed the impact of technological innovation on the management of prostate cancer, attempting to make a meta-analysis of randomized trials.

Methods

PubMed database has been explored for studies concerning acute and late urinary/gastrointestinal toxicity in low/intermediate risk LPC patients after receiving radiotherapy. Studies were then gathered into 5 groups: detected acute and chronic toxicity data from phase II non randomized trials were analyzed and Odds Ratio (OR) was calculated by comparing the number of patients with G0-1 toxicity and those with toxicity > G2 in the studied groups. A meta-analysis of prospective randomized trials was also carried out.

Results

The initial search yielded 575 results, but only 32 manuscripts met all eligibility requirements: in terms of radiation-induced side effects, such as gastrointestinal and genitourinary acute and late toxicity, hypofractionated 3DCRT seemed to be more advantageous than 3DCRT with conventional fractionation as well as IMRT with conventional fractionation compared to 3DCRT with conventional fractionation; furthermore, IMRT hypofractionated technique appeared more advantageous than IMRT with conventional fractionation in late toxicities. Randomized trials meta-analysis disclosed an advantage in terms of acute gastrointestinal and late genitourinary toxicity for Hypofractionated schemes.

Conclusions

Although our analysis pointed out a more favorable toxicity profile in terms of gastrointestinal acute side effects of conventional radiotherapy schemes compared to hypofractionated ones, prospective randomized trials are needed to better understand the real incidence of rectal and urinary toxicity in patients receiving radiotherapy for localized prostate cancer.

Versatility of the Novalis System to Deliver Image-Guided Stereotactic Body Radiation Therapy (SBRT) for Various Anatomical Sites

Stereotactic radiosurgery (SRS) and fractionated stereotactic radiotherapy (FSRT) programs to treat brain tumors were implemented when we first acquired the Brainlab Novalis system in 2003. Two years later, we started an extra-cranial stereotactic radio-ablation or more appropriately a stereotactic body radiation therapy (SBRT) program using the Brainlab Novalis image-guided system at The Methodist Hospital in Houston, Texas. We hereby summarize our initial experience with this system in delivering image-guided SBRT to a total of 80 patients during our first year of clinical implementation, from February 2005 to January 2006.

Over 100 lesions in more than 20 distinct anatomical sites were treated. These include all levels of spine from cervical, thoracic, lumbar, and sacral lesions. Spinal lesions encompass intramedullary, intradural, extradural, or osseous compartments. Also treated were lesions in other bony sites including orbit, clavicle, scapula, humerus, sternum, rib, femur, and pelvis (ilium, ischium, and pubis). Primary or metastatic lesions located in the head and neck, supraclavicular region, axilla, mediastinum, lung (both central and peripheral), abdominal wall, liver, kidney, para-aortic lymph nodes, prostate, and pelvis were also treated. In addition to primary radiotherapy, SBRT program using the Brainlab Novalis system allows re-irradiation for recurrence and “boost” after conventional treatment to various anatomical sites. Treating these sites safely and efficaciously requires knowledge in radiation tolerance, fraction size, total dose, biologically equivalent dose (BED), prior radiotherapy, detailed dose volume histograms (DVH) of normal tissues, and the radiosensitive/radioresistant nature of the tumor.

Placement of radio-opaque markers (Visicoil, Radiomed) in anatomical sites not in close proximity to bony landmarks (e.g., kidney and liver) helps in measuring motion and providing image guidance during each treatment fraction. Tumor/organ motion data obtained using 4D-CT while the patient is immobilized in the body cast aids in planning treatment margin and determining the need for respiratory motion control, e.g., abdominal compressor, gating, or active breathing control. The inclusion of PET/CT to the Brainlab treatment planning system further refines the target delineation and possibly guides differential fraction size prescription and delivery.

The majority of the patients tolerated the SBRT treatment well despite the longer daily treatment time when compared to that of conventional treatment. All patients achieved good pain relief after SBRT. Compared to conventional standard radiotherapy of lower daily fraction size, we observed that the patients achieved faster pain relief and possibly more durable symptom control. Very high local control with stable disease on imaging was observed post SBRT.

Our initial experience shows that the Brainlab Novalis system is very versatile in delivering image-guided SBRT to various anatomical sites. This SBRT approach can be applied to either primary or metastatic lesions in the primary, “boost,” or re-irradiation settings. The understanding of fraction size, total dose, BED, and DVH of normal tissues is very important in the treatment planning. Appropriate use of immobilization devices, radio-opaque markers for image-guidance, 4D-CT for tumor/organ motion estimates, and fusion of planning CT scans with biological/functional imaging will further improve the planning and delivery of SBRT, hopefully leading to better treatment outcome.

Single Course IMRT Plan to Deliver 45 Gy to Seminal Vesicles and 81 Gy to Prostate in 45 Fractions

We treat prostate and seminal vesicles (SV) to 45 Gy in 25 fractions (course 1) and boost prostate to 81 Gy in 20 more fractions (course 2) with Intensity Modulated Radiation Therapy (IMRT). This two-course IMRT with 45 fractions delivered a non-uniform dose to SV and required two plans and two QA procedures. We used Linear Quadratic (LQ) model to develop a single course IMRT plan to treat SV to a uniform dose, which has the same biological effective dose (BED) as that of 45 Gy in 25 fractions and prostate to 81 Gy, in 45 fractions. Single course IMRT plans were compared with two-course IMRT plans, retrospectively for 14 patients. With two-course IMRT, prescription to prostate and SV was 45 Gy in 25 fractions and to prostate only was 36 Gy in 20 fractions, at 1.8 Gy/fraction. With 45-fraction single course IMRT plan, prescription to prostate was 81 Gy and to SV was 52 or 56 Gy for a α/β of 1 and 3, respectively. 52 Gy delivered in 45 fractions has the same BED of 72 Gy3 as that of delivering 45 Gy in 25 fractions, and is called Matched Effective Dose (MED). LQ model was used to calculate the BED and MED to SV for α/β values of 1–10. Comparison between two-course and single course IMRT plans was in terms of MUs, dose-max, and dose volume constraints (DVC). DVC were: 95% PTV to be covered by at least 95% of prescription dose; and 70, 50, and 30% of bladder and rectum should not receive more than 40, 60, and 70% of 81 Gy. SV Volumes ranged from 2.9–30 cc. With two-course IMRT plans, mean dose to SV was non-uniform and varied between patients by 48% (54 to 80 Gy). With single-course IMRT plan, mean dose to SV was more uniform and varied between patients by only 9.6% (58.2 to 63.8 Gy), to deliver MED of 56 Gy for α/β − 1. Single course IMRT plan MUs were slightly larger than those for two-course IMRT plans, but within the range seen for two-course plans (549–959 MUs, n=51). Dose max for single-course plans were similar to two-course plans. Doses to PTV, rectum and bladder with single course plans were as per DVC and comparable to two-course plans. Single course IMRT plan reduces IMRT planning and QA time to half.

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.

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.

Saw Palmetto for Symptom Management During Radiation Therapy for Prostate Cancer

CONTEXT

Lower urinary tract symptoms (LUTSs) affect 75%-80% of men undergoing radiation therapy (RT) for prostate cancer.

OBJECTIVES

To determine the safety, maximum tolerated dose (MTD), and preliminary efficacy of Serenoa repens commonly known as saw palmetto (SP) for management of LUTS during RT for prostate cancer.

METHODS

The dose finding phase used the time-to-event continual reassessment method to evaluate safety of three doses (320, 640, and 960 mg) of SP. Dose-limiting toxicities were assessed for 22 weeks using the Common Terminology Criteria for Adverse Events for nausea, gastritis, and anorexia. The exploratory randomized controlled trial phase assessed preliminary efficacy of the MTD against placebo. The primary outcome of LUTS was measured over 22 weeks using the International Prostate Symptom Score. Additional longitudinal assessments included quality of life measured with the Functional Assessment of Cancer Therapy-Prostate.

RESULTS

The dose finding phase was completed by 27 men who reported no dose-limiting toxicities and with 20 participants at the MTD of 960 mg daily. The exploratory randomized controlled trial phase included 21 men, and no statistically significant differences in the International Prostate Symptom Score were observed. The prostate-specific concerns score of the Functional Assessment of Cancer Therapy-Prostate improved in the SP group (P = 0.03). Of 11 men in the placebo group, two received physician-prescribed medications to manage LUTS compared with none of the 10 men in the SP group.

CONCLUSION

SP at 960 mg may be a safe herbal supplement, but its efficacy in managing LUTS during RT needs further investigation.

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.

SBRT for prostate cancer: Challenges and features from a physicist prospective

Emerging data are showing the safety and the efficacy of Stereotactic Body Radiation Therapy (SBRT) in prostate cancer management. In this context, the medical physicists are regularly involved to review the appropriateness of the adopted technology and to proactively study new solutions. From the physics point of view there are two major challenges in prostate SBRT: (1) mitigation of geometrical uncertainty and (2) generation of highly conformal dose distributions that maximally spare the OARs. Geometrical uncertainties have to be limited as much as possible in order to avoid the use of large PTV margins. Furthermore, advanced planning and delivery techniques are needed to generate maximally conformal dose distributions. In this non-systematic review the technology and the physics aspects of SBRT for prostate cancer were analyzed. In details, the aims were: (i) to describe the rationale of reducing the number of fractions (i.e. increasing the dose per fraction), (ii) to analyze the features to be accounted for performing an extreme hypo-fractionation scheme (>6-7Gy), and (iii) to describe technological solutions for treating in a safe way. The analysis of outcomes, toxicities, and other clinical aspects are not object of the present evaluation.

The outcome and prognostic factors for lymph node recurrence after node-sparing definitive external beam radiotherapy for localized prostate cancer

Background

The prognostic factors for the recurrence of lymph node (LN) metastasis after dose-escalated radiotherapy (RT) in prostate cancer patients have not been well investigated. We report the prognostic factors and outcomes in patients receiving salvage treatment for LN recurrence after high-dose intensity-modulated RT (IMRT).

Methods

We studied a cohort of 419 patients with localized prostate adenocarcinoma undergoing definitive IMRT (78 Gy). LN recurrence was diagnosed by size criteria using computed tomography (CT) or magnetic resonance imaging, or abnormal uptake of ¹⁸F-fluorocholine by LNs on positron emission tomography/CT. Overall survival and LN recurrence-free survival (LNRFS) were calculated, and prognostic factors were evaluated.

Results

With a median follow-up of 60 months, 18 patients (4.3 %) had LN recurrence and a significantly lower 5-year overall survival rate (60 vs. 90 %, p = 0.003). Univariate analysis showed that T3/T4 stage (p = 0.003), Gleason score >7 (p < 0.001), and estimated risk of pelvic LN involvement of >30 % by the Roach formula (p = 0.029) were associated with significantly lower LNRFS. On multivariate analysis, high Gleason score (hazard ratio = 5.99, p = 0.007) was the only independent factor. The 1/2-year overall survivals after LN recurrence were 67/54 %. Patients with isolated LN recurrence (p = 0.003), prostate-specific antigen (PSA) doubling time >5 months (p = 0.009), interval between PSA nadir and biochemical failure >12 months (p = 0.035), and PSA <10 ng/ml at LN recurrence (p = 0.003) had significantly better survival. Patients with isolated LN recurrence had significantly better survival when treated with combined RT and hormones than when treated with hormones alone (p = 0.011).

Conclusions

Gleason score of >7 may predict LN recurrence in prostate cancer patients treated with definitive IMRT. Small number of patients limits the extrapolation of this risk with the primary treatment strategy. Combined RT and hormones may prolong survival in patients with isolated LN recurrence.

Superior target volume and organ stability with the use of endorectal balloons in post-prostatectomy radiotherapy

INTRODUCTION

We investigated the endorectal balloon (ERB) as a method to improve post-prostatectomy clinical target volume (CTV) stability.

METHODS

Seventy cone-beam CT (CBCT) obtained during radiotherapy treatment from seven patients treated with an ERB and 68 CBCT from seven patients treated without an ERB were contoured according to published guidelines. CTV was subdivided into superior and inferior CTV; whole rectal volume was subdivided into superior and inferior rectum and anal volume. Concordance index (CI) of CBCT treatment volumes compared with planning volumes was calculated and displacements were measured.

RESULTS

Whole rectal, superior and inferior rectum and anal CI were significantly improved with the ERB by 21%, 17%, 26% and 17% respectively (P < 0.0001). Overall CTV and inferior CTV CI was improved by 4% with the ERB (overall CTV P = 0.021; Inferior CTV P < 0.0001). In the ERB cohort, average displacement for superior CTV was 0.37 cm anterior-posterior (AP) and 0.10 cm left-right (LR). Average standard deviation was 0.27 cm AP and 0.11 cm LR. Inferior CTV average displacement was 0.11 cm AP and 0.02 cm LR. Average standard deviation was 0.11 cm AP and 0.02 cm LR. In the non-ERB cohort, average displacement for superior CTV was 0.43 cm AP and 0.10 mm left-right (LR). Average standard deviation was 0.45 cm AP and 0.13 cm LR. Inferior CTV average displacement was 0.16 cm AP and 0.01 cm LR. Average standard deviation was 0.17 cm AP and 0.03 cm LR. There was no statistically significant impact of bladder filling on CTV CI in ERB patients (P = 0.551) as opposed to non-ERB patients (P = 0.0421).

CONCLUSION

ERBs in the post-prostatectomy setting resulted in increased rectal and CTV stability while negating the effects of bladder filling on CTV stability.

Significance of image guidance to clinical outcomes for localized prostate cancer

Purpose. To compare toxicity profiles and biochemical tumor control outcomes between patients treated with image-guided intensity-modulated radiotherapy (IG-IMRT) and non-IGRT intensity-modulated radiotherapy (IMRT) for clinically localized prostate cancer. Materials and Methods. Between 2009 and 2012, 65 patients with localized prostate cancer were treated with IG-IMRT. This group of patients was retrospectively compared with a similar cohort of 62 patients who were treated between 2004 and 2009 with IMRT to the same dose without image guidance. Results. The median follow-up time was 4.8 years. The rectal volume receiving ≥40 and ≥70 Gy was significantly lower in the IG-IMRT group. Grade 2 and higher acute and late GI and GU toxicity rates were lower in IG-IMRT group, but there was no statistical difference. No significant improvement in biochemical control at 5 years was observed in two groups. In a Cox regression analysis identifying predictors for PSA relapse-free survival, only preradiotherapy PSA was significantly associated with biochemical control; IG-IMRT was not a statistically significant indicator. Conclusions. The use of image guidance in the radiation of prostate cancer at our institute did not show significant reduction in the rates of GI and GU toxicity and did not improve the biochemical control compared with IMRT.

Toxicity outcome in patients treated with modulated arc radiotherapy for localized prostate cancer

AIM

This study evaluates the acute toxicity outcome in patients treated with RapidArc for localized prostate cancer.

BACKGROUND

Modern technologies allow the delivery of high doses to the prostate while lowering the dose to the neighbouring organs at risk. Whether this dosimetric advantage translates into clinical benefit is not well known.

MATERIALS AND METHODS

Between December 2009 and May 2012, 45 patients with primary prostate adenocarcinoma were treated using RapidArc. All patients received 1.8 Gy per fraction, the median dose to the prostate gland, seminal vesicles, pelvic lymph nodes and surgical bed was 80 Gy (range, 77.4-81 Gy), 50.4 Gy, 50.4 Gy and 77.4 Gy (range, 75.6-79.2 Gy), respectively.

RESULTS

The time between the last session and the last treatment follow up was a median of 10 months (range, 3-24 months). The incidence of grade 3 acute gastrointestinal (GI) and genitourinary (GU) toxicity was 2.2% and 15.5%, respectively. Grade 2 acute GI and GU toxicity occurred in 30% and 27% of patients, respectively. No grade 4 acute GI and GU toxicity were observed. Older patients (>median) or patients with V60 higher than 35% had significantly higher rates of grade ≥2 acute GI toxicity compared with the younger ones.

CONCLUSIONS

RapidArc in the treatment of localized prostate cancer is tolerated well with no Grade >3 GI and GU toxicities. Older patients or patients with higher V60 had significantly higher rates of grade ≥2 acute GI toxicity. Further research is necessary to assess definitive late toxicity and tumour control outcome.

Reduced acute toxicity associated with the use of volumetric modulated arc therapy for the treatment of adenocarcinoma of the prostate

PURPOSE

Novel techniques to deliver intensity modulated radiation therapy (IMRT) have resulted in improved treatment efficiency and dosimetric endpoints. We aimed to compare acute gastrointestinal (GI) and genitourinary (GU) toxicity in patients treated for adenocarcinoma of the prostate (ACP) using volumetric modulated arc therapy (VMAT).

METHODS AND MATERIALS

A total of 122 (71 IMRT and 51 VMAT) ACP patients treated from 2004 to 2011 with definitive external beam radiation therapy were analyzed. Dose-volume histogram endpoints (V40, V65, V70, and V75 of the bladder and rectum) were collected for each patient. Median follow-up for patients treated with VMAT was 269 days versus IMRT was 1121 days. Acute Common Toxicity Criteria for Adverse Events (CTCAE) GI and GU toxicity scores, obtained during each weekly treatment check, were compared across cohorts. The univariate (UV) association between the covariates and outcomes was assessed and multivariable (MV) cumulative logit models were fit for each outcome.

RESULTS

Median patient age was 68 years and median prostate-specific antigen was 8.3. Both bladder and rectal V40, V65, V70, and V75 were all higher in the IMRT group versus the VMAT group (P < .05), which was likely influenced by larger planning target volumes in the IMRT group. The VMAT group had significantly lower rates of acute GU and acute GI CTCAE toxicity on UV association analysis. On MV analysis, VMAT remained independently associated with acute GU (odds ratio [OR], 0.18; 95% confidence interval [CI], 0.07-0.44; P < .001) and GI (OR, 0.16; 95% CI, 0.07-0.41; P < .001) toxicity.

CONCLUSIONS

VMAT appears to be independently associated with lower rates of acute GI and GU toxicity when compared with traditional IMRT. Further exploration of toxicity improvements associated with VMAT use in the definitive treatment of ACP is needed.

Effectiveness of a novel gas-release endorectal balloon in the removal of rectal gas for prostate proton radiation therapy

Endorectal balloons (ERBs) are routinely used in prostate proton radiation therapy to immobilize the prostate and spare the rectal wall. Rectal gas can distend the rectum and displace the prostate even in the presence of ERBs. The purpose of this work was to quantify the effects an ERB with a passive gas release conduit had on the incidence of rectal gas. Fifteen patients who were treated with a standard ERB and 15 with a gas-release ERB were selected for this retrospective study. Location and cross-sectional area of gas pockets and the fraction of time they occurred on 1133 lateral kilovoltage (kV) images were analyzed. Gas locations were classified as trapped between the ERB and anterior rectal wall, between the ERB and posterior rectal wall, or superior to the ERB. For patients using the standard ERB, gas was found in at least one region in 45.8% of fractions. Gas was trapped in the anterior region in 37.1% of fractions, in the posterior region in 5.0% of fractions, and in the sigmoid region in 9.6% of fractions. For patients using the ERB with the gas-release conduit, gas was found in at least one region in 19.7% of fractions. Gas was trapped in the anterior region in 5.6% of fractions, in the posterior region in 8.3% of fractions, and in the sigmoid region in 7.4% of fractions. Both the number of fractions with gas in the anterior region and the number of fractions with gas in at least one region were significantly higher in the former group than in the latter. The cross-sectional area of trapped gas did not differ between the two groups. Thus gas-release balloon can effectively release gas, and may be able to improve clinical workflow by reducing the need for catheterization.

Use of fractional dose-volume histograms to model risk of acute rectal toxicity among patients treated on RTOG 94-06

BACKGROUND AND PURPOSE

For toxicities occurring during the course of radiotherapy, it is conceptually inaccurate to perform normal-tissue complication probability analyses using the complete dose-volume histogram. The goal of this study was to analyze acute rectal toxicity using a novel approach in which the fit of the Lyman-Kutcher-Burman (LKB) model is based on the fractional rectal dose-volume histogram (DVH).

MATERIALS AND METHODS

Grade ≥2 acute rectal toxicity was analyzed in 509 patients treated on Radiation Therapy Oncology Group (RTOG) protocol 94-06. These patients had no field reductions or treatment-plan revisions during therapy, allowing the fractional rectal DVH to be estimated from the complete rectal DVH based on the total number of dose fractions delivered.

RESULTS

The majority of patients experiencing Grade ≥2 acute rectal toxicity did so before completion of radiotherapy (70/80=88%). Acute rectal toxicity depends on fractional mean rectal dose, with no significant improvement in the LKB model fit when the volume parameter differs from n=1. The incidence of toxicity was significantly lower for patients who received hormone therapy (P=0.024).

CONCLUSIONS

Variations in fractional mean dose explain the differences in incidence of acute rectal toxicity, with no detectable effect seen here for differences in numbers of dose fractions delivered.

Acute radiation-induced nocturia in prostate cancer patients is associated with pretreatment symptoms, radical prostatectomy, and genetic markers in the TGFβ1 gene

PURPOSE

After radiation therapy for prostate cancer, approximately 50% of the patients experience acute genitourinary symptoms, mostly nocturia. This may be highly bothersome with a major impact on the patient's quality of life. In the past, nocturia is seldom reported as a single, physiologically distinct endpoint, and little is known about its etiology. It is assumed that in addition to dose-volume parameters and patient- and therapy-related factors, a genetic component contributes to the development of radiation-induced damage. In this study, we investigated the association among dosimetric, clinical, and TGFβ1 polymorphisms and the development of acute radiation-induced nocturia in prostate cancer patients.

METHODS AND MATERIALS

Data were available for 322 prostate cancer patients treated with primary or postoperative intensity modulated radiation therapy (IMRT). Five genetic markers in the TGFβ1 gene (-800 G>A, -509 C>T, codon 10 T>C, codon 25 G>C, g.10780 T>G), and a high number of clinical and dosimetric parameters were considered. Toxicity was scored using an symptom scale developed in-house.

RESULTS

Radical prostatectomy (P<.001) and the presence of pretreatment nocturia (P<.001) are significantly associated with the occurrence of radiation-induced acute toxicity. The -509 CT/TT (P=.010) and codon 10 TC/CC (P=.005) genotypes are significantly associated with an increased risk for radiation-induced acute nocturia.

CONCLUSIONS

Radical prostatectomy, the presence of pretreatment nocturia symptoms, and the variant alleles of TGFβ1 -509 C>T and codon 10 T>C are identified as factors involved in the development of acute radiation-induced nocturia. These findings may contribute to the research on prediction of late nocturia after IMRT for prostate cancer.

Acute gastrointestinal and genitourinary toxicity of image-guided intensity modulated radiation therapy for prostate cancer using a daily water-filled endorectal balloon

Background

Our purpose was to report acute gastrointestinal (GI) and genitourinary (GU) toxicity rates for prostate cancer patients undergoing image-guided intensity modulated radiation therapy (IG-IMRT) with a daily endorectal water-filled balloon (ERB_H2O), and assess associations with planning parameters and pretreatment clinical characteristics.

Methods

The first 100 patients undergoing prostate and proximal seminal vesicle IG-IMRT with indexed-lumen 100 cc ERB_H2O to 79.2 Gy in 1.8 Gy fractions at our institution from 12/2008- 12/2010 were assessed. Pretreatment characteristics, organ-at-risk dose volume histograms, and maximum GU and GI toxicities (CTCAE 3.0) were evaluated. Logistic regression models evaluated univariate association between toxicities and dosimetric parameters, and uni- and multivariate association between toxicities and pretreatment characteristics.

Results

Mean age was 68 (range 51–88). Thirty-two, 49, and 19 patients were low, intermediate, and high-risk, respectively; 40 received concurrent androgen deprivation. No grade 3 or greater toxicities were recorded. Maximum GI toxicity was grade 0, 1, and 2 in 69%, 23%, and 8%, respectively. Infield (defined as 1 cm above/below the CTV) rectal mean/median doses, D75, V30, and V40 and hemorrhoid history were associated with grade 2 GI toxicity (Ps < 0.05). Maximum acute GU toxicity was grade 0, 1, and 2 for 17%, 41%, and 42% of patients, respectively. Infield bladder V20 (P = 0.03) and pretreatment International Prostate Symptom Scale (IPSS) (P = 0.003) were associated with grade 2 GU toxicity.

Conclusion

Prostate IG-IMRT using a daily ERB_H2O shows low rates of acute GI toxicity compared to previous reports of air-filled ERB IMRT when using stringent infield rectum constraints and comparable GU toxicities.

Localization of a portion of an endorectal balloon for prostate image-guided radiation therapy using cone-beam tomosynthesis: a feasibility study

PURPOSE

To assess the feasibility of using cone-beam tomosynthesis (CBTS) to localize the air-tissue interface for the application of prostate image-guided radiation therapy using an endorectal balloon for immobilization and localization.

METHODS AND MATERIALS

A Feldkamp-David-Kress-based CBTS reconstruction was applied to selected sets of cone-beam computed tomography (CBCT) projection data to simulate volumetric imaging achievable from tomosynthesis for a limited range of scan angles. Projection data were calculated from planning CT images of 10 prostate cancer patients treated with an endorectal balloon, as were experimental CBCT projections for a pelvic phantom in two patients. More than 50 points at the air-tissue interface were objectively identified by an intensity-based interface-finding algorithm. Using three-dimensional point sets extracted from CBTS images compared with points extracted from corresponding CBCT images, the relative shift resulting from a reduced scan angle was determined. Because the CBCT and CBTS images were generated from the same projection data set, shift identified was presumed to be due to distortions introduced by the tomosynthesis technique.

RESULTS

Scans of ≥60° were shown to be able to localize an air-tissue interface near the isocenter with accuracy on the order of a millimeter. The accuracy was quantified in terms of the mean discrepancy as a function of reconstruction angle.

CONCLUSION

This work provides an understanding of the effect of scan angle used in localization of a portion of an endorectal balloon by means of CBTS. CBTS with relatively small scan angles is capable of accurately localizing an extended interface near the isocenter and may provide clinically relevant measurements to guide IGRT treatments while reducing imaging radiation to the patient.

[Radiotherapy of prostate cancer]

With the development of modern radiation techniques, such as intensity-modulated radiotherapy (IMRT), a dose escalation in the definitive radiotherapy of prostate cancer and a consecutive improvement in biochemical recurrence-free survival (BFS) could be achieved. Among others, investigators at the Memorial Sloan-Kettering Cancer Center (MSKCC) saw 5-year BFS rates of up to 98%. A further gain in effectiveness and safety is expected of hypofractionation schedules, as suggested by data published by Kupelian et al., who saw a low 5-year rate of grade ≥2 rectal side-effects of 4.5%. However, randomized studies are just beginning to mature. Patients with intermediate or high-risk tumors should receive neoadjuvant (NHT) and adjuvant (AHT) androgen deprivation. Bolla et al. could show an increase in 5-year overall survival from 62-78%. The inclusion of the whole pelvis in the treatment field (WPRT) is still controversial. The RTOG 94-13 study showed a significant advantage in disease-free survival after 60 months but long-term data did not yield significant differences between WPRT and irradiation of the prostate alone.The German Society of Urology strongly recommends adjuvant radiotherapy of the prostate bed for pT3 N0 tumors with positive margins. In a pT3 N0 R0 or pT2 N0 R+ situation, adjuvant radiotherapy should at least be considered. So far, no randomized data on NHT and AHT have been published, so androgen deprivation remains an individual decision in the postoperative setting. In a retrospective analysis Spiotto et al. reported a positive effect for adjuvant WPRT and biochemical control.This article summarizes the essential publications on definitive and adjuvant radiotherapy and discusses the additional use of androgen deprivation and WPRT.

Endorectal balloon reduces anorectal doses in post-prostatectomy intensity-modulated radiotherapy

BACKGROUND AND PURPOSE

To investigate the effect of an endorectal balloon (ERB) on anal wall (Awall) and rectal wall (Rwall) doses in high-dose post-prostatectomy intensity-modulated radiotherapy (IMRT).

MATERIALS AND METHODS

For 20 patients, referred for salvage IMRT after prostatectomy for prostate cancer, two planning CT-scans were performed: one with and one without an air-filled ERB. A planning target volume (PTV) was defined, using international guidelines. Furthermore, the Awall and Rwall were delineated. In both the scans, IMRT plans were generated with a prescribed dose of 70 Gy. The mean dose (D(mean)), maximum dose, minimum dose, and volumes exposed to doses ranging from ≥ 20 to ≥ 70 Gy (V(20)-V(70)) to the Awall and Rwall were calculated. Finally, inner Rwall surface areas exposed to doses ranging from ≥ 20 to ≥ 70 Gy (A(20)-A(70)) were calculated. Dose-parameters were compared between plans with and without ERB.

RESULTS

All Awall parameters, except V(70), were significantly reduced by the ERB with an overall D(mean) reduction of 6 Gy. Absolute reductions in dose-volume parameters varied from 5% to 11%. Significantly reduced Rwall V(30), V(40), and A(40) were observed with ERB, irrespective of the target volume size.

CONCLUSION

ERB application significantly reduces Awall and to a lesser degree Rwall doses in high-dose post-prostatectomy IMRT.

Introducing an on-line adaptive procedure for prostate image guided intensity modulate proton therapy

With on-line image guidance (IG), prostate shifts relative to the bony anatomy can be corrected by realigning the patient with respect to the treatment fields. In image guided intensity modulated proton therapy (IG-IMPT), because the proton range is more sensitive to the material it travels through, the realignment may introduce large dose variations. This effect is studied in this work and an on-line adaptive procedure is proposed to restore the planned dose to the target. A 2D anthropomorphic phantom was constructed from a real prostate patient's CT image. Two-field laterally opposing spot 3D-modulation and 24-field full arc distal edge tracking (DET) plans were generated with a prescription of 70 Gy to the planning target volume. For the simulated delivery, we considered two types of procedures: the non-adaptive procedure and the on-line adaptive procedure. In the non-adaptive procedure, only patient realignment to match the prostate location in the planning CT was performed. In the on-line adaptive procedure, on top of the patient realignment, the kinetic energy for each individual proton pencil beam was re-determined from the on-line CT image acquired after the realignment and subsequently used for delivery. Dose distributions were re-calculated for individual fractions for different plans and different delivery procedures. The results show, without adaptive, that both the 3D-modulation and the DET plans experienced delivered dose degradation by having large cold or hot spots in the prostate. The DET plan had worse dose degradation than the 3D-modulation plan. The adaptive procedure effectively restored the planned dose distribution in the DET plan, with delivered prostate D(98%), D(50%) and D(2%) values less than 1% from the prescription. In the 3D-modulation plan, in certain cases the adaptive procedure was not effective to reduce the delivered dose degradation and yield similar results as the non-adaptive procedure. In conclusion, based on this 2D phantom study, by updating the proton pencil beam energy from the on-line image after realignment, this on-line adaptive procedure is necessary and effective for the DET-based IG-IMPT. Without dose re-calculation and re-optimization, it could be easily incorporated into the clinical workflow.

Postoperative intensity modulated radiation therapy in high risk prostate cancer: a dosimetric comparison

The aim of this study was to compare intensity-modulated radiation therapy (IMRT) with 3D conformal technique (3D-CRT), with respect to target coverage and irradiation of organs at risk for high dose postoperative radiotherapy (PORT) of the prostate fossa. 3D-CRT and IMRT treatment plans were compared with respect to dose to the rectum and bladder. The dosimetric comparison was carried out in 15 patients considering 2 different scenarios: (1) exclusive prostate fossa irradiation, and (2) pelvic node irradiation followed by a boost on the prostate fossa. In scenario (1), a 3D-CRT plan (box technique) and an IMRT plan were calculated and compared for each patient. In scenario (2), 3 treatment plans were calculated and compared for each patient: (a) 3D-CRT box technique for both pelvic (prophylactic nodal irradiation) and prostate fossa irradiation (3D-CRT only); (b) 3D-CRT box technique for pelvic irradiation followed by an IMRT boost to the prostatic fossa (hybrid 3D-CRT and IMRT); and (c) IMRT for both pelvic and prostate fossa irradiation (IMRT only). For exclusive prostate fossa irradiation, IMRT significantly reduced the dose to the rectum (lower Dmean, V50%, V75%, V90%, V100%, EUD, and NTCP) and the bladder (lower Dmean, V50%, V90%, EUD and NTCP). When prophylactic irradiation of the pelvis was also considered, plan C (IMRT only) performed better than plan B (hybrid 3D-CRT and IMRT) as respect to both rectum and bladder irradiation (reduction of Dmean, V50%, V75%, V90%, equivalent uniform dose [EUD], and normal tissue complication probability [NTCP]). Plan (b) (hybrid 3D-CRT and IMRT) performed better than plan (a) (3D-CRT only) with respect to dose to the rectum (lower Dmean, V75%, V90%, V100%, EUD, and NTCP) and the bladder (Dmean, EUD, and NTCP). Postoperative IMRT in prostate cancer significantly reduces rectum and bladder irradiation compared with 3D-CRT.

Acute and late toxicity in a randomized trial of conventional versus hypofractionated three-dimensional conformal radiotherapy for prostate cancer

PURPOSE

To compare the toxicity between hypofractionation vs. conventional fractionation schedules in patients with high-risk prostate cancer.

METHODS AND MATERIALS

Between January 2003 and December 2007, 168 patients were randomized to receive either hypofractionated (62 Gy in 20 fractions within 5 weeks, 4 fractions/wk) or conventionally fractionated (80 Gy in 40 fractions within 8 weeks) three-dimensional conformal radiotherapy to the prostate and seminal vesicles. All patients had undergone a 9-month course of total androgen deprivation, with radiotherapy starting 2 months after initiation of the total androgen deprivation.

RESULTS

The median follow-up was 32 and 35 months in the hypofractionation and conventional fractionation arms, respectively. For the patients developing acute toxicity, no difference between the two fractionation groups was found in either severity or duration of gastrointestinal or genitourinary toxicity. Also, no difference was found in the incidence and severity of late gastrointestinal and genitourinary toxicity between the two treatment schedules, with a 3-year rate of Grade 2 or greater toxicity of 17% and 16% for the hypofractionation arm and 14% and 11% for the conventional fractionation arm, respectively. A statistically significant correlation between acute and late gastrointestinal toxicity was found only in the conventional fractionation group.

CONCLUSION

Our findings suggest that the hypofractionation regimen used in our study is safe, with only a slight, nonsignificant increase in tolerable and temporary acute toxicity compared with the conventional fractionation schedule. The severity and frequency of late complications was equivalent between the two treatment groups.

Acute toxicity of image-guided hypofractionated radiotherapy for prostate cancer: nonrandomized comparison with conventional fractionation

OBJECTIVES

To compare acute toxicity of prostate cancer image-guided hypofractionated radiotherapy (hypo-IGRT) with conventional fractionation without image-guidance (non-IGRT). To test the hypothesis that the potentially injurious effect of hypofractionation can be counterbalanced by the reduced irradiated normal tissue volume using IGRT approach.

MATERIALS AND METHODS

One hundred seventy-nine cT1-T2N0M0 prostate cancer patients were treated within the prospective study with 70.2 Gy/26 fractions (equivalent to 84 Gy/42 fractions, α/β 1.5 Gy) using IGRT (transabdominal ultrasound, ExacTrac X-Ray system, or cone-beam computer tomography). Their prospectively collected data were compared with data of 174 patients treated to 80 Gy/40 fractions with non-IGRT. The difference between hypo-IGRT and non-IGRT cohorts included fractionation (hypofractionation vs. conventional fractionation), margins (hypo-IGRT margins: 7 mm and 3 mm, for all but posterior margins; respectively; non-IGRT margins: 10 and 5 mm, for all but posterior margins, respectively), and use of image-guidance or not. Multivariate analysis was performed to define the tumor-, patient-, and treatment-related predictors for acute toxicity.

RESULTS

All patients completed the prescribed radiotherapy course. Acute toxicity in the hypo-IGRT cohort included rectal (G1: 29.1%; G2: 11.2%; G3: 1.1%) and urinary events (G1: 33.5%; G2: 39.1%; G3: 5%). Acute toxicity in the non-IGRT patients included rectal (G1: 16.1%; G2: 6.3%) and urinary events (G1: 36.2%; G2: 20.7%; G3: 0.6%). In 1 hypo-IGRT and 2 non-IGRT patients, radiotherapy was temporarily interrupted due to acute toxicity. The incidence of mild (G1-2) rectal and bladder complications was significantly higher for hypo-IGRT (P = 0.0014 and P < 0.0001, respectively). Multivariate analysis showed that hypo-IGRT (P = 0.001) and higher PSA (P = 0.046) are correlated with higher acute urinary toxicity. No independent factor was identified for acute rectal toxicity. No significant impact of IGRT system on acute toxicity was observed.

CONCLUSIONS

The acute toxicity rates were low and similar in both study groups with some increase in mild acute urinary injury in the hypo-IGRT patients (most probably due to the under-reporting in the retrospectively analyzed non-IGRT cohort). The higher incidence of acute bowel reactions observed in hypo-IGRT group was not significant in the multivariate analysis. Further investigation is warranted in order to exclude the bias due to the nonrandomized character of the study.

Positional reproducibility and effects of a rectal balloon in prostate cancer radiotherapy

Despite the increasing use of the rectal balloon in prostate cancer radiotherapy, many issues still remain to be verified objectively including its positional reproducibility and relevance to treatment morbidity. We have developed a custom rectal balloon that has a scale indicating the depth of insertion and dilates symmetrically ensuring positional reproducibility. Fifty patients with prostate cancer treated by definitive 3D-conformal radiotherapy (3D-CRT) or intensity-modulated radiotherapy (IMRT) with rectal balloon were analyzed. Each of first five patients undergone computed tomography (CT) three times with a rectal balloon. The positional reproducibility was tested by Intraclass Correlation Coefficient (ICC) from the CT-to-CT fusion images. Planning variables and clinical acute toxicities were compared between when or not applying balloon. An ICC of greater than 0.9 in all directions revealed an excellent reproducibility of the balloon. Rectal balloon improved considerably the mean dose and V(45Gy)-V(65Gy) in plan comparison, and especially in 3D-CRT the rectal volume exposed to more than 60 Gy dropped from 41.3% to 19.5%. Clinically, the balloon lowered acute toxicity, which was lowest when both the balloon and IMRT were applied simultaneously. The rectal balloon carries excellent reproducibility and reduces acute toxicity in 3D-CRT and IMRT for prostate cancer.

Physiologic reactions after proton beam therapy in patients with prostate cancer: significance of urinary autoactivation

PURPOSE

Proton therapy is a sophisticated treatment modality for prostate cancer. We investigated how physiologic factors affected the distribution of autoactivation as detected by positron emission tomography (PET) after proton beam therapy.

METHODS AND MATERIALS

Autoactivation was evaluated in 59 patients treated with a 210-MeV proton beam. Data acquisition for autoactivation by PET started 5 minutes after proton irradiation to assess activation. In the first 29 patients, five regions of interest were evaluated: planning target volume (PTV) center, urinary bladder inside the PTV, urinary bladder outside the PTV, rectum (outside the PTV), and contralateral femoral bone head (outside the PTV). In the remaining 30 patients, urine activity was measured directly. In a phantom study autoactivation and its diffusion after proton beam irradiation were evaluated with water or an ice block.

RESULTS

Mean activities calculated by use of PET were 629.3 Bq in the PTV center, 555.6 Bq in the urinary bladder inside the PTV, 332.5 Bq in the urinary bladder outside the PTV, 88.4 Bq in the rectum, and 23.7 Bq in the femoral bone head (p < 0.001). Mean urine activity was 679.4 Bq, recorded 10 minutes after therapy completion, and the half-life for urine autoactivation was 4.5 minutes.

CONCLUSIONS

Urine is a major diffusion mediator of autoactivation after proton beam therapy. Our results indicate that physiologic factors can influence PET images of autoactivation in the context of proton beam therapy verification.

Prostate-specific antigen bounce after intensity-modulated radiotherapy for prostate cancer

OBJECTIVES

To report prostate-specific antigen (PSA) bounce in patients treated with intensity-modulated radiotherapy (IMRT) alone. Previous studies have reported PSA bounce in prostate cancer patients treated with conventional radiotherapy, 3D conformal radiotherapy, and permanent seed brachytherapy.

METHODS

From January 1997 to July 2002, 102 patients with clinically localized prostate cancer were treated with IMRT alone. No patients received androgen ablation. PSA bounce was defined as a PSA increase of at least 0.4 ng/mL, followed by any PSA decrease. Biochemical failure was defined by both the American Society for Therapeutic Radiology and Oncology 1996 and 2006 consensus definitions.

RESULTS

The median follow-up was 76 months. The median length of time until the first PSA bounce was 13.6 months. Thirty-three patients (32.4%) had at least 1 PSA bounce, with 25 (24.5%) having 1 bounce; 6 (5.9%), 2 bounces; and 2 (2.0%), 4 bounces. PSA bounce was not significantly associated with biochemical no evidence of disease survival, clinical stage, pretreatment PSA, Gleason combined score, prostate planning target volume, PSA nadir, or mean dose to the prostate. The rate of PSA bounce in patients aged ≤ 70 and > 70 years was 44.4% and 22.8%, respectively (P = .032).

CONCLUSIONS

Our patient series is the first report on PSA bounce in patients treated with IMRT. Our study confirms that the majority of patients with a bouncing PSA remain biochemically and clinically free of disease with extended follow-up.

Evaluation of Inter-fractional Setup Shifts for Site-specific Helical Tomotherapy Treatments

This paper proposes to summarize and analyze the daily patient setup shifts based on megavoltage computed tomography (MVCT) image registration results for Helical TomoTherapy® (HT) treatment. One hundred and fifty-five consecutive treatment plans for a total of 137 patients delivered by the HT unit through one year were collected in this study. The patient data included pelvis (26%), abdomen (23%), lung (21%), head and neck (10%), prostate (8%), and others (12%). All the translational and roll rotational shifts made via auto MVCT and kilovoltage computed tomography (kVCT) image registration were recorded at each fraction. Manual fine-tuning was followed if automatic registration result was not satisfactory. The mean shift ± one standard deviation (1 SD) was calculated for each patient based on the entire treatment course. For each treatment site, the average shift was analyzed as well as displacement in 3D vector. Statistical tests were performed to analyze the relationship of patient-specific, tumor site-specific, and fraction number association with the patient setup shifts. For all the treatment sites, the largest average shift was found in the anterior-posterior direction. The population standard deviations were between 1.2 and 5.6 mm for the X, Y, and Z directions and ranged from 0.2 to 0.6 degrees for the roll rotational correction. The largest standard deviations of the setup reproducibility in X, Y, and Z directions were found in lung patients (4.2 mm), abdomen, lung and spine patients (4.4 mm), and prostate patients (5.6 mm), respectively. The maximum 3D displacement was 10.9 mm for prostate patients' setup. ANOVA tests demonstrated the setup shifts were statistically different between patients even for those that were treated at the same tumor site in the translational directions. No strong correlation between the setup and the fraction number was found. In conclusion, the MVCT guided function in the HT treatment enables us to generate relatively accurate daily setup through registration with KVCT data sets. Our results indicate that lung, prostate, and abdominal patients are more prone to setup uncertainty and should be carefully evaluated.

Endo-rectal balloon cavity dosimetry in a phantom: performance under IMRT and helical tomotherapy beams

BACKGROUND AND PURPOSE

The use of endo-rectal balloons as immobilisation devices in external beam radiotherapy for prostate cancer has led to improved target position reproducibility and a decrease in rectal toxicity. The air cavity created by an endo-rectal balloon in photon radiotherapy perturbs the dose distribution. In this study, the effect of the balloon cavity on the dose distribution and the accuracy to which two treatment planning systems calculate the dose distribution were investigated.

MATERIALS AND METHODS

Single beams as well as 3D conformal, conventional IMRT and helical tomotherapy treatment plans were investigated using a specifically constructed phantom. Radiochromic film was used to measure the cavity wall doses and cavity wall DVHs.

RESULTS

For a 70 Gy prescription dose both the Pinnacle and TomoTherapy TPSs over-predicted the anterior cavity wall dose by 1.43 Gy, 3.92 Gy and 2.67 Gy for 3D conformal, conventional IMRT and helical tomotherapy, respectively. The posterior cavity wall dose was under-predicted by 2.62 Gy, 2.01 Gy and 4.79 Gy for 3D conformal, conventional IMRT and helical tomotherapy, respectively. An over-prediction by the Pinnacle RTPS of the V50, V60, V65 and V70 values for the cavity wall DVH was measured for the 3D conformal and conventional IMRT cases. These reductions may lead to a less than expected rectal toxicity. The TomoTherapy RTPS under-predicted the V50, V60, V65 and V70 values which may lead to higher rectal toxicity than predicted.

CONCLUSION

Calculation of dose around an air cavity created by an endo-rectal balloon provides a challenge for radiotherapy planning systems. Various electronic disequilibrium situations exist due to the cavity, which can lead to a lower anterior rectal wall and higher posterior rectal wall dose than that calculated by planning systems. This has consequences for comparisons of dose volume constraints between different modalities.