S. Junius

Hypofractionated intensity modulated irradiation for localized prostate cancer, results from a phase I/II feasibility study

BackgroundTo assess acute (primary endpoint) and late toxicity, quality of life (QOL), biochemical or clinical failure (secondary endpoints) of a hypofractionated IMRT schedule for prostate cancer (PC).Methods38 men with localized PC received 66 Gy (2.64 Gy) to prostate,2 Gy to seminal vesicles (50 Gy total) using IMRT.Acute toxicity was evaluated weekly during radiotherapy (RT), at 1–3 months afterwards using RTOG acute scoring system. Late side effects were scored at 6, 9, 12, 16, 20, 24 and 36 months after RT using RTOG/EORTC criteria.Quality of life was assessed by EORTC-C30 questionnaire and PR25 prostate module. Biochemical failure was defined using ASTRO consensus and nadir+2 definition, clinical failure as local, regional or distant relapse.ResultsNone experienced grade III-IV toxicity. 10% had no acute genito-urinary (GU) toxicity, 63% grade I; 26% grade II. Maximum acute gastrointestinal (GI) scores 0, I, II were 37%, 47% and 16%. Maximal acute toxicity was reached weeks 4–5 and resolved within 4 weeks after RT in 82%.Grade II rectal bleeding needing coagulation had a peak incidence of 18% at 16 months after RT but is 0% at 24–36 months. One developed a urethral stricture at 2 years (grade II late GU toxicity) successfully dilated until now. QOL urinary symptom scores reached a peak incidence 1 month after RT but normalized 6 months later. Bowel symptom scores before, at 1–6 months showed similar values but rose slowly 2–3 years after RT. Nadir of sexual symptom scores was reached 1–6 months after RT but improved 2–3 years later as well as physical, cognitive and role functional scales.Emotional, social functional scales were lowest before RT when diagnosis was given but improved later. Two years after RT global health status normalized.ConclusionThis hypofractionated IMRT schedule for PC using 25 fractions of 2.64 Gy did not result in severe acute side effects. Until now late urethral, rectal toxicities seemed acceptable as well as failure rates. Detailed analysis of QOL questionnaires resulted in the same conclusion.

Intrafractional prostate motion during online image guided intensity-modulated radiotherapy for prostate cancer

INTRODUCTION Intrafractional motion consists of two components: (1) the movement between the on-line repositioning procedure and the treatment start and (2) the movement during the treatment delivery. The goal of this study is to estimate this intrafractional movement of the prostate during prostate cancer radiotherapy. MATERIAL AND METHODS Twenty-seven patients with prostate cancer and implanted fiducials underwent a marker match procedure before a five-field IMRT treatment. For all fields, in-treatment images were obtained and then processed to enable automatic marker detection. Combining the subsequent projection images, five positions of each marker were determined using the shortest path approach. The residual set-up error (RSE) after kV-MV based prostate localization, the prostate position as a function of time during a radiotherapy session and the required margins to account for intrafractional motion were determined. RESULTS The mean RSE and standard deviation in the antero-posterior, cranio-caudal and left-right direction were 2.3±1.5 mm, 0.2±1.1 mm and -0.1±1.1 mm, respectively. Almost all motions occurred in the posterior direction before the first treatment beam as the percentage of excursions>5 mm was reduced significantly when the RSE was not accounted for. The required margins for intrafractional motion increased with prolongation of the treatment. Application of a repositioning protocol after every beam could decrease the 1cm margin from CTV to PTV by 2 mm. CONCLUSIONS The RSE is the main contributor to intrafractional motion. This RSE after on-line prostate localization and patient repositioning in the posterior direction emphasizes the need to speed up the marker match procedure. Also, a prostate IMRT treatment should be administered as fast as possible, to ensure that the pre-treatment repositioning efforts are not erased by intrafractional prostate motion. This warrants an optimized workflow with the use of faster treatment techniques.

A multi-institutional analysis comparing adjuvant and salvage radiation therapy for high-risk prostate cancer patients with undetectable PSA after prostatectomy.

BACKGROUND AND PURPOSE In men with adverse pathology at the time of radical prostatectomy (RP), the most appropriate timing to administer radiotherapy (RT) remains a subject for debate. To determine whether salvage radiotherapy (SRT) upon early prostate-specific antigen (PSA) relapse is equivalent to immediate adjuvant radiotherapy (ART) post RP. MATERIAL AND METHODS 130 patients receiving ART and 89 receiving SRT were identified. All had an undetectable PSA after RP. Homogeneous subgroups were built based on the status (±) of lymphatic invasion (LVI) and surgical margins (SM), to allow a comparison of ART and SRT. Biochemical disease-free survival (bDFS) was calculated from the date of surgery and from the end of RT. The multivariate analysis was performed using the Cox Proportional hazard model. RESULTS In the SM-/LVI- and SM+/LVI- groups, SRT was a significant predictor of a decreased bDFS from the date of surgery, while in the SM+/LVI+ group, there was a trend towards significance. From the end of RT, SRT was also a significant predictor of a decreased bDFS in three patient groups: SM-/LVI-, SM+/LVI- and SM+/LVI+. Gleason score >7 showed to be another factor on multivariate analysis associated with decreased bDFS in the SM-/LVI- group, from the date of surgery and end of RT. Preoperative PSA was a significant predictor in the SM-/LVI- group from the date of RP only. CONCLUSIONS Immediate ART post RP for patients with high risk features in the prostatectomy specimen significantly reduces bDFS after RP compared with early SRT upon PSA relapse.

Evaluating a decision aid for patients with localized prostate cancer in clinical practice.

Aim: The aim of the study was to evaluate the usefulness of a decision aid regarding treatment options for patients with early-stage localized prostate cancer. Methods: 50 patients with newly diagnosed localized prostate cancer received the decision aid and were interviewed twice: before the decision-making consultation with the physicians and before treatment or, in case of watchful waiting, before the follow-up consultation. The physicians (radiation oncologists and urologists) were interviewed after the consultation. Results: The patients became more active partners in the decision-making process: They were better prepared for the consultation, asked more direct information, and were able to make a more deliberative choice. Generally, the use of the decision aid improved the quality of the consultation and resulted in a treatment decision agreed upon by both parties. Sometimes the consultation turned out to be more time-consuming. The decision aid did not only improve the patient-physician interaction but also helped patients to discuss the disease with their partner and family members. Conclusion: The use of the decision aid has a positive impact on the consultation and the decision-making process. The policy of involving patients more actively in the decision process should be further implemented in daily practice.

SU‐FF‐T‐147: Intra Fractional Motion in Clinical IMRT Prostate Treatments, Warrants the Use of Faster Treatment Techniques

Purpose: To estimate intrafracional motion of the prostate in a routine clinical setting and its impact on margin reduction and treatment time. Method and Materials: External beam treatment for cancer of the prostate using an IMRT technique was evaluated. Fifteen patients underwent a marker match procedure ensuring correct positioning at time of treatment. For all fields intra‐treatment images were obtained, yielding 5 to 7 images per fraction. IMRT was delivered using a dynamic sliding window technique. The obtained images were processed to remove IMRT information. The markers were detected in the image using an automated methodology. Every image was timestamped and chronologically adjacent images were backprojected to yield 3D marker coordinates. Allowing to calculate the position of the prostate during the treatment delivery at specific time instances. Using a Poisson model for the probability of movement we can determine the maximal allowable time frame within which to perform this treament. Results: The maximal treament time measured was 1460s, the shortest lasted 343s. The times were measured starting from the last image in the marker‐match procedure and includes the decision and adjustment process. Depending on the elapsed time we noticed an increase in positional confidence level from 5.8mm to 7.6mm. The delivery of the fields are of the order of 250s. Conclusion: We note a significant increase in probability of prostate movement in our treaments as time elapses. This limits the amount of margin reduction possible. There are two strategies possible to reduce this time. 1) Increase the marker match speed, or 2) increase the delivery speed. A good candidate to do this is the use of a volumetric Arc technique (VMAT) which is implemented in our department with RapidArc™. The latter is able to deliver the same or even better dose distribution in under 2 minutes (8 patients).

SU‐FF‐T‐133: RapidArcTM: Commissioning and Dose Escalation Possibilities

Purpose: This paper reports our experience in commissioning RapidArc™ for use in clinical practice. Additionally, we performed a dose escalation planning study using radiobiological parameters to compare the outcome of IMRT and RapidArc plans. Method and Materials: For commissioning we used a standard set of guidelines as outlined by C. Ling et al. This augmented with dosimetry checks, including absolute point measurements in phantom and relative comparisons in air. In addition, we introduced more automated methodologies for picket fence testing of the MLC during RapidArc delivery. Because of different couch systems than presumed in the implementation by the manufacturers a new parameterization of the couch was introduced. In a preliminary dose escalation study of 8 clinical patients we evaluated the treatment plans on a radiobiological basis. Results: For Commissioning: the measurements differed not more than 2% of the predicted values. For Dose Escalation: NTCP calculations for grade 2 rectal bleeding showed a significant reduction (p=0.03) of the mean NTCP from 2.6% to 1.9%, even in this small group of patients. TCP values did not differ significantly (TCP(IMRT)=75.5%, TCP(RA)=75.4%). Conclusion: Methods described in this report lead to successful implementation of RapidArc in clinical practice. At time of presentation we expect to increase the statistics to 25 patients. Conflict of Interest: Research sponsored by Varian Medical Systems, Palo Alto, California, USA