Auditing local methods for quality assurance in radiotherapy using the same set of predefined treatment plans.

BACKGROUND AND PURPOSE: Local implementation of plan-specific quality assurance (QA) methods for intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) treatment plans may vary because of dissimilarities in procedures, equipment and software. The purpose of this work is detecting possible differences between local QA findings and those of an audit, using the same set of treatment plans. METHODS: A pre-defined set of clinical plans was devised and imported in the participating institute's treatment planning system for dose computation. The dose distribution was measured using an ionisation chamber, radiochromic film and an ionisation chamber array. The centres performed their own QA, which was compared to the audit findings. The agreement/disagreement between the audit and the institute QA results were assessed along with the differences between the dose distributions measured by the audit team and computed by the institute. RESULTS: For the majority of the cases the results of the audit were in agreement with the institute QA findings: ionisation chamber: 92%, array: 88%, film: 76% of the total measurements. In only a few of these cases the evaluated measurements failed for both: ionisation chamber: 2%, array: 4%, film: 0% of the total measurements. CONCLUSION: Using predefined treatment plans, we found that in approximately 80% of the evaluated measurements the results of local QA of IMRT and VMAT plans were in line with the findings of the audit. However, the percentage of agreement/disagreement depended on the characteristics of the measurement equipment used and on the analysis metric.

In vivo dosimetry in gynecological applications-A feasibility study.

PURPOSE: To investigate the feasibility of in vivo dosimetry using microMOSFET dosimeters in patients treated with brachytherapy using two types of gynecological applicators. METHODS AND MATERIALS: In this study, a microMOSFET was placed in an empty needle of an Utrecht Interstitial Fletcher applicator or MUPIT (Martinez Universal Perineal Interstitial Template) applicator for independent verification of treatment delivery. Measurements were performed in 10 patients, with one to three microMOSFETs per applicator and repeated for one to four fractions, resulting in 50 in vivo measurements. Phantom measurements were used to determine characteristics of the microMOSFETs. RESULTS: Phantom measurements showed a linear relationship between dose and microMOSFET threshold voltage, and a calibration coefficient (mV/cGy) was determined. Reproducibility of repeated 50 cGy irradiations was 2% (1 standard deviation). Distance and angle dependencies were measured and correction factors were determined. Subsequently, three microMOSFETs were placed in a phantom to measure a validation plan. The difference between predicted and measured dose was less than the measurement uncertainty (±9%, 2 standard deviations). In vivo measurements were corrected for distance and angle dependencies. Differences between predicted and measured dose in the patients were smaller than the measurement uncertainty for the majority of the measurements. CONCLUSIONS: In vivo dosimetry using microMOSFETs in MUPIT and Utrecht Interstitial Fletcher applicators has proved to be feasible. Reimaging should be performed after detection of differences larger than 10% between predicted and measured dose to verify the applicator configuration. Movement of the applicator relative to the target or organs at risk is undetectable with this method.

Interstitial brachytherapy for bladder cancer with the aid of laparoscopy.

Since 2009, 40 patients with a T1/T2 bladder cancer have been treated at ARTI with interstitial brachytherapy via laparoscopy. Under general anaesthesia, the tumour area is implanted under cystoscopic control with the aid of a laparoscope, and instruments are attached to the Da Vinci robot. Mapping is then done via a simulator photo and a CT scan. With this method, the patient has fewer complications and the average hospitalization time is halved, while a consistent quality of implant is maintained. This method is also associated with a major reduction in the number of problems that can be attributed to the accessibility of the catheter.

Health-related quality of life up to six years after (125)I brachytherapy for early-stage prostate cancer.

PURPOSE: Health-related quality of life (HRQOL) after prostate brachytherapy has been extensively described in published reports but hardly any long-term data are available. The aim of the present study was to prospectively assess long-term HRQOL 6 years after (125)I prostate brachytherapy. METHODS AND MATERIALS: A total of 127 patients treated with (125)I brachytherapy for early-stage prostate cancer between December 2000 and June 2003 completed a HRQOL questionnaire at five time-points: before treatment and 1 month, 6 months, 1 year, and 6 years after treatment. The questionnaire included the RAND-36 generic health survey, the cancer-specific European Organization for Research and Treatment of Cancer core questionnaire (EORTCQLQ-C30), and the tumor-specific EORTC prostate cancer module (EORTC-PR25). A change in a score of >/=10 points was considered clinically relevant. RESULTS: Overall, the HRQOL at 6 years after (125)I prostate brachytherapy did not significantly differ from baseline. Although a statistically significant deterioration in HRQOL at 6 years was seen for urinary symptoms, bowel symptoms, pain, physical functioning, and sexual activity (p <.01), most changes were not clinically relevant. A statistically significant improvement at 6 years was seen for mental health, emotional functioning, and insomnia (p <.01). The only clinically relevant changes were seen for emotional functioning and sexual activity. CONCLUSION: This is the first study presenting prospective HRQOL data up to 6 years after (125)I prostate brachytherapy. HRQOL scores returned to approximately baseline values at 1 year and remained stable up to 6 years after treatment. (125)I prostate brachytherapy did not adversely affect patients' long-term HRQOL.

The impact of acute urinary retention after iodine-125 prostate brachytherapy on health-related quality of life.

PURPOSE: To evaluate the impact of acute urinary retention (AUR) in patients treated with (125)I prostate brachytherapy on short- and long-term health-related quality of life (HRQOL); and to assess whether pretreatment HRQOL has additional value in the prediction of AUR. METHODS AND MATERIALS: For 127 patients treated with (125)I brachytherapy for localized prostate cancer between December 2000 and June 2003, toxicity and HRQOL data were prospectively collected. Patients received a HRQOL questionnaire at five time points: before and 1 month, 6 months, 1 year, and 6 years after treatment. The questionnaire included the RAND-36 generic health survey, the cancer-specific European Organization for Research and Treatment of Cancer core questionnaire (EORTC QLQ-C30), the tumor-specific EORTC prostate cancer module (EORTC QLQ-PR25), and the American Urological Association (AUA) symptom index. RESULTS: Of 127 patients, 13 (10.2%) developed AUR. Patients with AUR had a significantly worse urinary QOL at all time points compared with patients without AUR. The mean difference over time (6 years) between both groups for the EORTC QLQ-PR25 urinary symptom score was 13.0 points (p < 0.001) and for the AUA urinary symptom score was 15.7 points (p = 0.001). Global QOL scores (EORTC QLQ-C30) over time for patients who developed AUR were significantly worse compared with patients without AUR (mean difference 6.7 points; p = 0.043). In multivariate logistic regression analysis, pretreatment International Prostate Symptom Score (p = 0.004) and neoadjuvant hormonal treatment (p = 0.034) were predictors of AUR. Quality of life did not have added predictive value. CONCLUSION: Acute urinary retention after prostate brachytherapy has a significant negative impact on patient's HRQOL up to 6 years after treatment, in terms of both global QOL measures and urinary symptom scores. Furthermore, our results suggest limited value of pretreatment HRQOL measures for the prediction of AUR.

Quality of life of patients after permanent prostate brachytherapy in relation to dosimetry.

PURPOSE: To investigate changes in quality of life (QoL) after permanent prostate brachytherapy and to correlate these changes with postimplant dosimetry based on magnetic resonance (MR) images. METHODS AND MATERIALS: For this study, 127 patients with low-stage prostate cancer and treated with brachytherapy received a QoL questionnaire at five time points: before treatment and at 4 weeks, 6 months, 1 year, and 2 years after treatment. The questionnaire included the RAND-36 generic health survey, the cancer-specific European Organization for Research and Treatment of Cancer (EORTC) core questionnaire, the tumor-specific EORTC prostate cancer module, and the American Urological Association symptom index. Postimplant dosimetry was based on registered T1 spin echo transversal, T2 turbo spin echo transversal, and T2 turbo spin echo sagittal MR images and CT images taken 4 weeks after implantation of the iodine-125 seeds. Calculated parameters were prostate volume, prostate volume receiving 100% (V100) and 150% (V150) dose, dose to 90% of the prostate volume (D90), maximum dose in 1-, 2-, and 5-cm3 rectum volume, distance between prostate and anterior rectum wall, and the maximum dose in 1%, 2%, and 5% urethra volume. Analysis of variance for repeated measures was used for comparison of the means of all variables in the different questionnaires. Linear regression analysis (stepwise) was used to investigate the correlations between QoL parameters and dosimetry parameters. RESULTS: On average, only the QoL at 4 weeks after implant was significantly different from (worse than) the QoL at the other time points. Regression analysis showed a significant correlation between changes in bowel problems and the maximum dose in 2-cm3 rectum volume, between changes in urinary symptoms and prostate volume, and between changes in urinary problems and the D90 value of the prostate. CONCLUSIONS: The QoL for patients with permanent prostate implants was worse in the first months after treatment but returned to baseline values 1 year after implant. Significant correlations were found between dose distribution and QoL.

Quality of permanent prostate implants using automated delivery with seedSelectron versus manual insertion of RAPID Strands.

BACKGROUND AND PURPOSE: To compare the quality of manually inserted RAPID Strand implants with automatically inserted selectSeed implants using volumetric and dosimetric parameters. PATIENTS AND METHODS: Patients with T1 to T2 prostate carcinoma were treated with brachytherapy. The (125)I seeds were implanted in the prostate in three different ways: manual insertion of RAPID Strands (R); insertion of selectSeeds using the seedSelectron (S); a combination of both techniques: manual insertion of RAPID Strands in the left half of the prostate and insertion of selectSeeds with the seedSelectron in the right half of the prostate (RS). The comparison is based on implant and target specific parameters. The implant specific parameters, V(100), homogeneity index (HI), and natural dose ratio (NDR), were determined at the time of implantation and four weeks later. MR images taken four weeks after the implantation were used for the calculation of the target specific parameters: D(90), HI, external index (EI), and conformation number (CN). RESULTS: We found no significant difference between the groups of implants (R, S, RS) for the implant specific parameters V(100), HI, and NDR at t(0) and neither at t(4w). For each group, the V(100) values decreased significantly with time between t(0) and t(4w). The target specific parameters D(90), HI, EI and CN were not significantly different between the groups. For the group of patients with both RAPID Strands and selectSeeds, we found a significant difference in D(90) between both halves of the prostate. CONCLUSIONS: The dosimetry parameters of a newly introduced implant technique using an automatic seed afterloader were not significantly different from the parameters of a manual insertion technique using RAPID Strands. Since either technique has its advantages and disadvantages regarding seed migration, physics quality assurance, efficiency, logistics, and ease of use, it was decided to use both techniques and to continue evaluations.

MRI-guided prostate brachytherapy with single needle method--a planning study.

BACKGROUND AND PURPOSE: Magnetic resonance image (MRI)-guided prostate brachytherapy with a conventional closed MR scanner is hampered by the limited access to the prostate. To handle this problem, we have designed a new implantation method, based on a patient lying in a closed MR scanner, a robotic device to be placed between patient's legs, and one needle with one insertion point. MATERIALS AND METHODS: The MRI-guided robotic system inserts the needle into the prostate to deliver the seeds. Each time, the needle will be retracted to the rotation point (in the body), and the insertion angle can be changed. The possible angles of the needle are limited by the geometry of the closed MR scanner and the presence of the symphysis, rectum and urethra. We have done a planning study to investigate the feasibility of this single needle method. RESULTS: The treatment plans made with the single needle method showed the possibility to cover the prostate with the prescribed dose without piercing the urethra or rectum and without pubic bone interference. The plans were comparable to the plans made for the multi parallel needle method, and the 144Gy isodose enclosed the prostate with a margin of about 2 mm. The planned angles of the needle were within the range of possible angles. CONCLUSIONS: This planning study has shown the feasibility of adequate prostate coverage with the divergent single needle method within the limited space inside the closed MR scanner.

How low is the alpha/beta ratio for prostate cancer?

PURPOSE: Recently, low alpha/beta values of 1.2 and 1.5 Gy for prostate tumors have been derived from clinical results of external beam radiotherapy and of permanent implants of (125)I and (103)Pd. In the analyses the contributions of tumor repopulation, and edema as a result of inserting radioactive seeds in the prostate, have been ignored. In this paper we reanalyzed the clinical data and introduced the contribution of repopulation and edema. METHODS AND MATERIALS: The linear quadratic-biologically effective dose model was used for reanalysis. In this model, the influence of repopulation and edema has been taken into account. The biologically effective dose was calculated as a function of alpha/beta for 2 brachytherapy regimens with (125)I and (103)Pd and 2 fractionated treatments, and for different half-times for repair of sublethal damage for the brachytherapy regimens. RESULTS: We have found a plausible alpha/beta value of 3.1 to 3.9 Gy, an alpha value of 0.1 to 0.15 Gy(-1), and a half-time of repair of about 0.5 h. CONCLUSIONS: It seems now that the alpha/beta value is low, 3.1-3.9 Gy, but not as low as the 1.2 and 1.5 Gy reported earlier.

Biologically effective dose for permanent prostate brachytherapy taking into account postimplant edema.

PURPOSE: To study the influence of radiobiologic and physical parameters and parameters related to edema on the biologically effective dose (BED) for permanent prostate implants and to determine the optimal timing of seed reconstruction for BED calculation. METHODS AND MATERIALS: On the basis of the linear-quadratic model, an expression for the BED was derived, including the edema parameters. A set of parameter values was defined, and these parameter values were varied one at a time to examine the effect on the BED and the theoretically effective treatment time (t(eff)). A ratio epsilon was defined to investigate the optimal timing of seed reconstruction. RESULTS: The maximal BED decreases when the extent of lethal damage is smaller, the potential tumor doubling time is smaller, the half-life time of the seeds is shorter, and the magnitude of prostate volume increase is larger. For 125I, the optimal timing of seed reconstruction is 25 days after implantation. Seed reconstruction 1 day after the implantation results in an underestimation of the BED of at most 43%, depending on the magnitude and half-life of edema. An overestimation of the BED of at most 22% is calculated when seed reconstruction took place at the effective treatment time. CONCLUSION: The maximal BED depends strongly on the value of alpha, the potential tumor doubling time, and the choice of isotope. If prostate volume increase due to edema is not taken into account, the BED will be underestimated shortly after the implantation and overestimated if the calculations are based on images taken several months after implantation. The optimal timing of BED evaluation for 125I seed implants and typical prostate edema values is 25 days after implantation.