Stereotactic radiosurgery for the treatment of brain metastases: impact of cerebral disease burden on survival.

Stereotactic radiosurgery (SRS) for brain metastases has been carried out at the Leeds Gamma Knife Centre since March 2009. The aim of this study was to examine the outcomes and toxicity in our initial cohort of patients. The medical records of patients with brain metastases referred to the Leeds Gamma Knife Centre between March 2009 and July 2010 were retrospectively reviewed. Data on survival, primary tumour, Karnofsky performance status, time from diagnosis to identification of brain metastases, previous treatment for brain metastases and results of staging prior to SRS were recorded. Patients were followed up with regular magnetic resonance imaging of the brain for a minimum of 6 months and data on toxicity and oral steroid dose were recorded. Statistical analysis was carried out using SPSS v14.0. Survival curves were compared using the Log Rank test. Fifty eight patients (19 male) had a median survival of 50.4 weeks (95% CI, 32.6-68.2 weeks). Lung (36%) and breast (27%) were the most common primary tumours. Patients with a total volume of metastases treated < 5000 mm(3) (p = 0.007) or between 5000 mm(3) and 10,000 mm(3) (p = 0.01) had significantly improved survival compared with patients with a total treated volume > 10,000 mm(3). In addition, largest treated lesion < 5000 mm(3) was a positive prognostic factor. Patients with a single metastasis did not survive significantly longer than those with multiple metastases. Steroid dose dropped significantly after SRS (p < 0.01) and was the same or less in 91% of patients. There were only three cases of grade 3 toxicity. Our study reports survival comparable with other series on radiosurgery and demonstrates a significant decrease in steroid dose following treatment. It also shows that the size of the largest treated metastasis and total volume of metastatic disease seemed a better predictor of outcome than number of metastases treated.

Comprehensive I-125 multi-seed comparison for prostate brachytherapy: dosimetry and visibility analysis.

PURPOSE: To compare the visibility of different manufacturers I-125, seeds, and to investigate the effect of differences in dosimetry on treatment planning. MATERIALS AND METHODS: Oncura Oncoseed, Oncura Echoseed, IBT Intersource, Bebig Isoseed and Nucletron Selectseed were investigated. The point dose at increasing distances from each seed type was calculated for three different angles; theta=0 degrees, 45 degrees and 90 degrees (where theta=0 degrees lies parallel to seed length). 10 patient plans were used to assess the effect of a change in dosimetry on treatment planning and quality of prostate and rectum implant indices such as Vp100, Vp200, Dp90, Vr100 and Vr69. All implant indices and dosimetry data were compared to Oncoseed. Visibility under X-ray, fluoroscopy, CT and MRI was investigated using prostate phantoms created in-house. Statistical significance was calculated using paired two-tailed t-tests. RESULTS: Dosimetric analysis was carried out for seeds of the same source strength. Differences in dose increase closer to the centre of each source, with the largest changes occurring for the angle theta=0 degrees. Selectseed and Isoseed seed types provide a consistently lower dose in all three directions. Changes to Vp100 are small and statistically insignificant for all seeds except Selectseed which shows a statistically significant decrease of 0.04% (p=0.02). Changes to Vp150 and Vp200 are statistically significant (p<0.01), with Intersource showing the greatest increase in both values. Selectseed shows a decrease in both Vp150 and Vp200. Echoseed shows an increase in both Vp150 and Vp200. Changes to D90 are statistically significant (p<0.01), with Intersource showing the greatest increase, followed by Isoseed then Echoseed. Selectseed shows a decrease in D90. For Vr100 there is no statistically significant change for any seed type. However, all seeds except Selectseed show a statistically significant increase in the value of Vr69, with Intersource showing the greatest increase. On fluoroscopy and X-ray images, Intersource seeds appear least visible, Echoseed and Oncoseed are similar, and Isoseed and Selectseed are most visible. Ultrasound greyscale beam profiles show that all seed images have a FWHM larger than the Oncoseed image. The CT greyscale beam profiles are similar for all seed images. The MRI signal voids are similar for all seed images except Intersource which shows a larger signal void. CONCLUSIONS: The greatest changes to point dose occur at very close distances to the seeds. Changing seed type may require a treatment replan to maintain satisfactory DVH criteria. Visibility on US and CT is similar, though it may vary on MRI, X-ray and fluoroscopy.

Side effects of permanent I125 prostate seed implants in 667 patients treated in Leeds.

PURPOSE: To report the side effects and complications after I-125 seeds prostate implant after 8.5 years experience. METHODS AND MATERIALS: Six hundred and sixty seven (667) patients were treated between March 1995 and December 2001. The median follow up is 31 months with a maximum of 98.2 months. Morbidity data were collected from a review of patient case-notes. Patients also provided prospective data on urinary symptoms using the International Prostate Symptom Score (IPSS) scoring chart before treatment and at regular follow up. Patients were also sent a questionnaire detailing symptoms and side effects following their brachytherapy. This enabled them to record urinary, bowel and sexual function side effects independently. Logistic regression analysis was carried out to identify the risk of catheterisation in relation to the pre-implant prostate volume and potential implant factors such as the number of seeds and needles and implant dose. RESULT: The urinary symptom score rises in the first few months after implantation and returns to within one or two points of the pre-treatment score within one year. Nine patients reported incontinence prior to treatment and 15, 12 and 10 patients reported incontinence 6, 12 and 24 months after treatment, respectively. Catheterisation was reported in 97 (14.5%) patients. At six months 84.9% of patients reported no change in bowel function and 78.9% at 12 months. 6.4% of patients complained of some increased bowel frequency at 6 months and 5.7% at 12 months. 402 (77.2%) patients reported being fully potent before treatment and that this fell to 32.4% after treatment. Logistic regression showed that the most significant factors which correlate with the probability of catheterisation are the pre-treatment prostate volume and the number of seeds and needles implanted. CONCLUSION: The side effects and complications after prostate brachytherapy as reported here and elsewhere confirm that the treatment is not only convenient but also has a low risk of serious long term side effects.

A study of a pretreatment method to predict the number of I-125 seeds required for prostate brachytherapy.

PURPOSE: Prediction of the number of iodine seeds (I-125) required for prostate implantation is an important tool to reduce the number of unused seeds for brachytherapy. This study was designed to investigate the relationship between the number of seeds implanted vs. prostate volume. This can produce a tool to accurately estimate the number of seeds required for a given target volume. In addition, total cost of treatment, personal radiation risks during storage and handling, and errors in accounting for seeds can be reduced. METHODS AND MATERIALS: Data from two groups of patients who had I-125 seed prostate implants (Oncura/Amersham RAPIDStrand model 6711 I-125) have been separately analyzed: (A) The relationship between prostate volume vs. number of seeds implanted was based on 401 patients treated between 1999 and 2002 who were implanted with seeds of air kerma strength (AKS) of 0.459 microGy h(-1) @ 1 m per seed. (B) The relationship between prostate volume vs. total seed AKS was analyzed. This was based on 628 patients treated between 1999 and 2002 who were implanted with a range of seed strengths from 0.381 to 0.521 U. Both patient groups were subdivided into integer prostate volume bins. For each bin, the mean and 95% confidence intervals (CI) for the implanted number of seeds or total AKS implanted were calculated. The upper 95% CI was used to investigate the relationship between the number of seeds implanted and total AKS implanted vs. prostate volume. RESULTS: The new method of predicting the number of seeds shows valid and accurate results. The required number of seeds can be predicted, which helps to reduce the number of leftover seeds to 3% of the total number of seeds ordered. CONCLUSION: The number of I-125 seeds or the total activity that is required to deliver the prescribed dose for the target volume can be predicted. This could reduce the overall treatment cost by accurate seed ordering before implantation.

Impact of selection of post-implant technique on dosimetry parameters for permanent prostate implants.

PURPOSE: To investigate the variability of prostate implant quality indices between three different methods of calculating the post-implant dose distribution. METHODS AND MATERIALS: In a study of 9 permanent prostate implant patients, post-implant dosimetry was carried out using three methods of identifying seed positions within the prostate volume: (1) prostate volumes defined by transrectal ultrasound (TRUS) immediately following implant were registered with shift-film defined seed positions, (2) seeds were identified directly from the post-implant TRUS images, and (3) CT was used to define seed positions and prostate volumes from images acquired at 41-65 days post-implant. For each method, the volume of prostate receiving 90%, 100%, and 150% of the prescribed dose (V90, V100, V150) and the dose delivered to 90% of the prostate volume (D90) were calculated. RESULTS: Post-implant TRUS volumes were within 15% of the preimplant TRUS volumes in 8 of the 9 patients investigated. The post-implant CT volume was within 15% of the preimplant (TRUS) volume in only 3 of the 9 cases. The value of the dosimetry parameters was dependent on the method used and varied by 5-25% for V90, 5-30% for V100, 42-134% for V150, and 9-60% for D90. No simple relationship was found between change in volume and the resultant change in dosimetry parameter. Differences in dosimetry parameters due to source localization uncertainties was found to be small (< or = 10% for V100) when comparing methods (1) and (2). CONCLUSIONS: There are many uncertainties in the calculation of parameters that are commonly used to describe the quality of a permanent prostate implant. Differences in the parameters calculated were most likely a result of a combination of factors including uncertainties in delineating the prostate with different imaging modalities, differences in source identification techniques, and intraobserver variability.