Loose Seeds Research Articles

SU‐FF‐T‐196: Effect of Stranded and Loose Seeds in Relation to Prostate Edema in Permanent I‐125 Prostate Brachytherapy

Objectives: The dosimetric evaluation of permanent I‐125 seed prostate implant is often based on the assumption that prostate is static throughout the treatment time which lasts for months. However, the prostate in general becomes edematous due to the surgical procedure, followed by resolution of edema post implantation. Such changes in prostate volume would have an impact on the dosimetry. The aim of this study is to investigate the effect of use of stranded and loose seeds on prostate swelling. Methods: Thirty‐six prostate patients were treated with I‐125 seed brachytherapy. Nineteen of them were treated with stranded seeds while 17 were with loose seeds. Pretreatment prostate volume was measured with transrectal ultrasound and MRI was used to quantify the post‐implant volume at day 1, 8, and 30. Results: The average percentage swelling on day 1, 8, and 30 was the same for both cohorts. Edema half‐life was found to be 15 days for the loose seed and 10 days for the stranded seed patients respectively. When the data were stratified based on the pre‐implant volume < 35 cc and >= 35 cc percentage swelling was found to be significantly higher (44.8 vs. 26.2, p=0.013) only on day one for the loose seed group compared to the stranded seed for pre‐implant volume <35 cc. No significant difference in swelling with respect to seed type was found for large prostate (V >=35 cc). Conclusions: This study shows that for small pre‐implant prostate volume (V<35cc), stranded seeds show significant reduction in amount of swelling relative to the loose seeds on day one of implant.

SU‐FF‐T‐249: Improved Homogeneity with Fourth Generation Prostate Brachytherapy Implants — A Revised I‐125 Seed Nomogram

Purpose: Fourth generation stranded implants permit periprostatic placement of seeds with improved homogeneity across the target volume. The purpose of this study was to compare Mick nomogram seed implants with fourth generation stranded implants and determine if a revision in the activity per volume nomogram is warranted. Methods and Materials: Eighty‐four patients who had undergone prostate brachytherapy were selected for this study and were split into two arms of forty‐two patients each. The first arm, were treated in the year 2000 with loose seeds. Treatment planning for these set of patients was performed intraoperatively using a nomogram based on the volume of the prostate. The second arm, were treated in the year 2006 with stranded seeds. Pre‐plans determining the number of seeds and needle loading were generated using Variseed treatment‐planning system. Approximately 20 – 25 % of the seeds were implanted within the PTV in the periprostatic tissue. The prescribed dose was 145 Gy for all eighty‐four patients. Also, all patients were implanted with I‐125 (Model 6711) seeds with an activity of 0.497 U/seed (0.391 mCi/seed). Results: The total implanted activity and the number of seeds used in our stranded seed prostate implants was significantly less than that used in our loose seeds implants. Mean V100 values for the stranded seeds were greater than those for loose seeds. The stranded seeds were also associated with higher mean D90 values and lower V150‐uretheral doses. Conclusions: We attribute this reduction in activity and the number of seeds to effectively treat the same prostate volume, to the efficient seed distribution of the stranded seeds. Loose seeds inside the prostate are subject to variable migration throughout the prostate resulting in a more heterogeneous dose distribution, while stranded seeds are systematically positioned inside the target volume resulting in a more homogeneous dose distribution.

SU-FF-T-280: LDR Brachytherapy for Low Risk Prostate Cancer with I-125 - a Comparison of the Results with Loose Seeds From Two Different Producers

Purpose: LDR brachytherapy is a well established treatment method for low risk prostate cancer. Different techniques and radioactive sources are used. In this study I-125 seeds from two different manufactures were compared regarding dosimetric properties and clinical outcome. Method: From 08/2000 to 04/2005 nearly 500 patients have been implanted with I-125 seeds. The first 201 patients were implanted with loose seeds from the first manufacturer the other patients have been implanted with loose seeds from a second manufacturer. Both kinds of seeds have the same geometric dimensions, the same application system and method can be used. To compare the clinical outcome two subgroups of 101 consecutive patients were defined. In all cases the same treatment method was performed always by the same operating team. In both groups clinical dosimetric parameters (intraoperative and postoperative) were investigated, morbidity of the patients was analyzed. Individual nomograms were calculated to compare physically differences. Results: Dosimetric and clinical data of 202 patients were analyzed. No significant differences could be found in the number of seeds, prostate volume or implanted activity comparing the two subgroups. The intraoperative and postoperative D90 of the prostate was the same in both groups as well as the D30 of the urethra and the V100 of the rectum. Our clinical data show a very low probability of side effects in both groups of patients. Looking to the correlation of implanted activity and intraoperative prostate volume for both groups we found a small difference for prostate size greater than 50cc. Conclusion: LDR brachytherapy with I-125 seeds is a well established treatment method. The quality of the implantation depends on the treatment method and the experience of the operating team. Different kinds of sources with the same isotope do not influence the clinical outcome and the quality of life for the patient significantly.

SU-DD-A1-06: Do Stranded Seeds Improve the Quality of Permanent Prostate Seed Implant?

Purpose: The aim of this study is to find out if the stranded seeds improve the quality of the permanent prostate seed implant by doing retrospective dosimetric analysis for patients with localized prostate cancer and have been treated using loose or stranded Iodine‐125 seeds in 2005 and 2006 at our center. Method and Materials: The dosimetric results reconstructed from patient CT scans at the same day of seed implant (day1) and the 21st day after implant (day21) were compared between 31 patients with loose seeds and 31 patients with stranded seeds. Treatment plans were all generated in real time by a single experienced medical physicist using a single planning system before the procedure of implant. Most of the implants were performed by a single experienced radiationoncologist with transrectal ultrasoundimage and x‐ray image guidance using preloaded needles. The needles with stranded seeds were loaded in real time using a special‐designed seed loader by putting seeds and spacers in plastic sleeves which are made of PGA and Lactide materials. Results: There is some improvement on the mean value of D90 at day21 for stranded seeds (95.7% vs. 93.4%) but it is not significant (p=0.247). And no significant difference was observed on the mean values of V100 and V150 at day21 (86.9% vs. 87.0% with p=0.485 and 53.7% vs. 53.4% with p=0.465). They also have a similar histogram distribution. The mean values of D90 and V100 at day1 show that patients with stranded seeds are even little bit worse than those with loose seeds, 80.5% vs. 87.4% with p=0.025 and 79.0% vs. 82.3% with p=0.063. Conclusion: Comparing the dosimetric parameters at day21 and day1, we conclude that the quality of prostate seed implant was not improved significantly by using stranded seeds which required more resources and manpower.

Dosimetric comparison of loose seeds and stranded seeds in I-125 permanent implant for low-risk prostate cancer

Dosimetric comparison of loose seeds and stranded seeds in I-125 permanent implant for low-risk prostate cancer

Penile Bulb Dosimetry — Impact of Prostate Brachytherapy Implant Technique

Introduction: Erectile dysfunction (ED) following prostate brachytherapy (BXT) has been reported to be related to dose received by the penile bulb. To minimise penile bulb dose, whilst preserving prostate dosimetry, we have developed a novel technique for I125 seed BXT using both stranded seeds and loose seeds delivered with a Mick applicator, and implanted via the sagittal plane on trans-rectal ultrasound.

Naturalising transgenics: Official seeds, loose seeds and risk in the decision matrix of Gujarati cotton farmers

Cotton farmers in Gujarat, western India, faced a novel decision matrix when Delhi gave provisional approval, in March 2002, to Mahyco–Monsanto Biotech Ltd. to release three Bt-cotton varieties. These varieties represented India's first legally commercialised transgenics: official seeds. Unofficial transgenic seeds were also available to farmers both as unpackaged, unbranded ‘loose seeds’ – mostly F2 progeny of a popular but banned transgenic variety – and as packaged, branded local gray-market Bt cultivars not approved by government. This essay utilises original field research to analyse the reasoning frame of farmers in choosing which seeds to plant. It finds that Bt cotton varieties were valued by farmers for reduction of pest damage, pesticide cost and thus improvement of yields and income. Second, choices among Bt varieties are complex, riding on seed-cost differentials between official and stealth cultivars and variable fit of varieties to local agronomic conditions. Third, some farmers chose non-Bt cultivars, for various reasons, including preference for organic cultivation – though some considered Bt cotton compatible with organic agriculture. Cotton farmers in Gujarat have in effect naturalised transgenic varieties, slotting them into familiar strategies to hedge risks.

Improvements in prostate brachytherapy dosimetry due to seed stranding

Purpose Prostate brachytherapy with suture embedded seeds has emerged as a popular technique to reduce seed migration and to improve dosimetry. Various trials have shown improved dosimetry with seed fixity, whereas others have shown no benefit and possible detriment to suture embedded seeds. In order to contribute to the understanding of whether seed stranding improves dosimetry, we present retrospective data from our institution. Methods and materials We analyzed 80 patients treated between April 29, 2001 and June 19, 2006, receiving I-125 monotherapy for prostate cancer. Brachytherapy patients at the University of California, Los Angeles (UCLA) were initially treated using a transperineal approach with loose seeds. Subsequent to October 26, 2002, all patients were implanted using suture embedded seeds. Dosimetric quantifiers were calculated based on a CT obtained 1-month postimplantation. Results Dosimetry of patients treated with stranded seeds showed significant improvement. Specifically, the V100 (volume of the prostate receiving 100% of the prescribed dose) improved from 88% to 92% ( p <0.05), and the D90 (maximum dose received by 90% of the prostate) improved from 143 to 155 Gy ( p <0.05). Conclusions At UCLA, the use of suture embedded seeds resulted in a significant improvement in our dosimetric quantifiers. Based upon other published studies, this improvement in dosimetry may translate into improved patient outcomes.

2324: Comparison of Seed Migration to the Chest After Permanent Prostate Brachytherapy With Loose Seeds, Stranded Seeds, or Both

2324: Comparison of Seed Migration to the Chest After Permanent Prostate Brachytherapy With Loose Seeds, Stranded Seeds, or Both

A dosimetric analysis of unstranded seeds versus customized stranded seeds in transperineal interstitial permanent prostate seed brachytherapy

Purpose This study aimed to retrospectively analyze the dosimetric and toxicity results from 272 patients with localized prostate cancer treated consecutively using loose or stranded radioactive seeds by transrectal ultrasound-guided transperineal permanent prostate seed brachytherapy. Methods and materials Two hundred seventy-two patients with localized prostate cancer treated between February 2002 and June 2004 were analyzed. All patients were treated with radioactive iodine-125 or palladium-103 using unstranded or loose seeds (USS) (159 patients) or customized stranded seeds (CSS) at variable spacing (5–50 mm) (113 patients) (Vari-Strand™; BrachySciences, Oxford, CT). A single experienced brachytherapist performed all implants. Results There was a slight improvement in the dosimetric parameter D 90 between the CSS (101.9%) and USS (99.3%) groups ( p = 0.041). However, overall implant quality based on Radiation Therapy Oncology Group (RTOG) guidelines was similar between both groups. Conclusions We conclude that the D 90 value calculated for CSS is statistically improved when compared to the USS cohort, but without a clinically significant difference. There was no difference in the toxicity scores in either group. Overall quality between groups is comparable in our institution.

Modelling the quantitative effects of pre‐ and post‐dispersal seed predation in Pinus sylvestris L.

Summary Despite three decades of intensive research on seed predation, rather little is known about how important a role it plays in plant demography. Here a balance sheet of seed predation is drawn up for Pinus sylvestris, based on mortality caused by its main seed predators. This species is of special interest because trees carry seeds throughout the year and can therefore support specialist as well as generalist seed predators. Also, its regeneration in Scotland is weak and some of its main seed predators (red squirrels, crossbills, wood ants) are themselves threatened. Field data from two P. sylvestris forests were used to estimate rates of predation on seeds due to pre‐ and post‐dispersal predators, including both specialists and generalists. The rates of predation changed systematically over time and were fitted to time‐dependent functions. The resulting functions were incorporated into a model, which was solved numerically to determine the fate of a cohort of seeds. On average, approximately 20% of seeds in the cohort were consumed by pre‐dispersal seed predators, approximately 25% of seeds by post‐dispersal seed predators, and approximately 55% of seeds were still alive at the end of 2 years. This reduces the seed pool for regeneration of P. sylvestris, but is unlikely to be a serious problem for regeneration. Seed survival was most sensitive to the rate at which seeds became invulnerable to further seed predation, and to the rate of seed dispersal from cones on trees. Seed survival was less sensitive to seed predation. However, among seed predators, carabids feeding on loose seeds and birds eating seeds in open cones were the most important. Cones open as they dry out, and the timing of seed dispersal is therefore weather‐dependent. Late opening of cones had a deleterious effect on seed survival because it led to an increase in pre‐dispersal seed predation. Thus, in a period of climate change, patterns of seed predation would be expected also to change, altering the success of regeneration.

Prostate brachytherapy postimplant dosimetry: A comparison of suture-embedded and loose seed implants

Purpose To compare postimplant dosimetry and seed embolization rates for prostate brachytherapy implants using suture-embedded and loose seeds. Methods and materials Dosimetric analysis of the whole prostate, prostate quadrants, rectum, and surrogate urethra was performed on 54 loose seed and 81 RAPIDStrand (RS) patients. Seed embolization rates were determined from chest radiographs. Results Whole prostate V 100 and D 90 did not differ significantly for the loose seed ( V 100 = 90.5%, D 90 = 153.2 Gy) and RS groups ( V 100 = 91.5%, D 90 = 151.6 Gy) ( p = 0.43 and 0.65, respectively), but V 150, V 200, and contiguous V 200 were higher ( p ≤ 0.003) for the RS group (59.9%, 28.3%, and 23.2%, respectively) than the loose seed group (52.5%, 22.8%, and 16.1%, respectively). Extraprostatic measures (conformity index and external index) were also different at the p <0.05 level. The embolization rate was 40% in the loose seed group and 14% in the RS group. Conclusions The most significant difference between the two study groups was a decrease in the embolization rate. Although some statistically significant changes in postimplant dosimetry were observed, they were nevertheless small.

SU-FF-T-247: FIRST, the First Choice in the Management of Localised Prostate Cancer?

Purpose: To evaluate the clinical use of the FIRST system for the definitive treatment of localised prostate cancer.Method and Materials: From January 2003 through December 2005 a total of 634 patients were treated, either with the FIRST system (278) or with RAPID Strands (356). Patient characteristics were identical for both groups, but strands were more often used after TURP (19 vs. 3). We looked at implant data and side effects, also in relation to the use of loose spacers in the FIRST group. Results: Prostate volumes were similar (34 and 35.5 cc) as well as the number of seeds (mean 74 and 70). In total 20,526 Selectseeds and 24,866 stranded seeds were used. The number of loose spacers in the FIRST system was approximately the same as the number of active seeds. The number of seeds that disappeared from the body was the same (128 and 130), but migration within the body was higher with FIRST (48 vs. 0). Migration of spacers within the body cannot be detected. Toxicity according to the common toxicity criteria was similar for both techniques. Acute retention was found in 24 FIRST patients (8.6%) and 27 strand patients (7.5%). Infection was found in 3 patients in both groups. Erectile dysfunction was found in 32% after FIRST and 28% after strands, but not assessed in more than 50% of all patients. None of the patients died of prostate cancer; intercurrent death was encountered in 4 FIRST and 6 strand patients. Conclusion: We cannot favour one of the techniques. There is a higher incidence of migration with loose seeds as used in the FIRST system, but no detrimental effects were observed. The use of polylactide loose spacers in FIRST did not result in detectable adverse effects; neither did the polyglactin wires in the stranded patients.

TH‐B‐224C‐01: Permanent Prostate Brachytherapy Using Plastic Palladium‐103 Seeds

Purpose: A new model of palladium‐103 (Pd‐103) seeds with plastic encapsulation (OptiSeed103 Model 1032P, International Brachytherapy, Norcross, Georgia) is commercially available. The abstract reports the investigation of using the plastic Pd‐103 seeds in prostate brachytherapy. Method and Materials: The RTOG criteria were adopted in patient selection. A real‐time transrectal‐ultrasound (TRUS) guided transperineal implant technique was employed. A Foley catheter was used to localize the urethra. The seed placement followed a modified uniform loading protocol. At the completion of an implant, TRUS images were recorded. Post CT dosimetry was accomplished in the patient's 30‐day follow‐up visit and a seed migration survey was also performed. Results: Three prostate cancer patients underwent the Pd‐103 seed implantation. 386 loose seeds with total activity of 656.1 U were implanted. The patients tolerated the procedure. No abnormal symptoms have been reported in the first half‐year follow‐up, except the detection of 3 migrated seeds to the lungs in a patient. The seed appearances in the pelvic radiographs and CT images were similar to that of the metallic seeds. A significant seed enhancement was observed in the post‐implant TRUS images. Phantom studies showed similar results. A post plan for each patient was generated on the post‐implant TRUS images where 97% of the seeds were identified with confidence. The patterns of the seed distribution in the TRUS and CT images were similar although the GTVs were different due to implant edema. Conclusion: Regarding the dosimetry and implant process, there are no differences between the plastic and metallic seeds. A superior property of the plastic seeds is its appearance in TRUS images. The seed distribution can be immediately displayed in the TRUS images at the completion of an implant. Cold spots can be identified in real time and additional seeds may be added so as to improve the implant quality.

Effect of post-implant edema on prostate brachytherapy treatment margins

To determine if postimplant prostate brachytherapy treatment margins calculated on Day 0 differ substantially from those calculated on Day 30. Thirty patients with 1997 American Joint Commission on Cancer clinical stage T1-T2 prostatic carcinoma underwent prostate brachytherapy with I-125 prescribed to 144 Gy. Treatment planning methods included using loose seeds in a modified peripheral loading pattern and treatment margins (TMs) of 5-8 mm. Postimplant plain radiographs, computed tomography scans, and magnetic resonance scans were obtained 1-4 hours after implantation (Day 0). A second set of imaging studies was obtained at 30 days after implantation (Day 30) and similarly analyzed. Treatment margins were measured as the radial distance in millimeters from the prostate edge to the 100% isodose line. The TMs were measured and tabulated at 90 degrees intervals around the prostate periphery at 0.6-cm intervals. Each direction was averaged to obtain the mean anterior, posterior, left, and right margins. The mean overall TM increased from 2.6 mm (+/-2.3) on Day 0 to 3.5 mm (+/-2.4) on Day 30. The mean anterior margin increased from 1.2 mm on Day 0 to 1.8 mm on Day 30. The posterior margin increased from 1.2 mm on Day 0 to 2.8 mm on Day 30. The lateral treatment margins increased most over time, with mean right treatment margin increasing from 3.9 mm on Day 0 to 4.7 mm on Day 30. Treatment margins appear to be durable in the postimplant period, with a clinically insignificant increase from Day 0 to Day 30.

Avaliação do vigor de sementes de alface nuas e peletizadas

As sementes de alface são de tamanho pequeno, pouca massa e formato irregular, por isso a peletização é a forma utilizada para facilitar sua distribuição e manuseio. Embora a técnica seja conhecida há muitos anos, pouco se estudou sobre os métodos para avaliação da qualidade fisiológica das sementes, após este tratamento. O objetivo do trabalho foi comparar a eficiência de alguns testes para avaliar o vigor em sementes nuas e peletizadas de alface. Utilizaram-se seis lotes de sementes nuas e peletizadas de alface das cultivares Regina e Vera, nos quais se aplicaram os testes de germinação, primeira contagem, envelhecimento acelerado, solução osmótica e índice de velocidade de germinação. O delineamento experimental utilizado foi inteiramente casualizado, com quatro repetições, realizando-se comparação de médias pelo teste de Tukey a 5% de probabilidade de erro. As sementes peletizadas apresentaram menor vigor do que as sementes nuas. Os testes de envelhecimento acelerado, solução osmótica (-0,25 MPa) e o índice de velocidade de germinação foram eficientes para estratificar lotes de sementes nuas de alface, quanto ao vigor, sendo recomendados, também, para uso em sementes peletizadas. Entretanto, a peletização pode exercer influência nos resultados, necessitando adaptações na metodologia para utilização na comparação entre sementes nuas e peletizadas.

Radioactive seed migration to the chest after transperineal interstitial prostate brachytherapy: Extraprostatic seed placement correlates with migration: Eshleman JS, Davis BJ, Pisansky TM, Wilson TM, Haddock MG, King BF, Darby CH, Lajoie WN, Oberg AL, Division of Radiation Oncology, Mayo Clinic, Rochester, MN. Int J Radiat Oncol Biol Phys 2004;59:419–25

To examine the incidence of seed migration detected on chest X-ray and to identify the predictors associated with its occurrence. Between May 1998 and April 2000, 102 patients underwent permanent prostate brachytherapy at our institution and 100 were eligible for the study. Chest X-rays obtained at follow-up were examined for the number and location of seeds. The patient and treatment variables potentially associated with the occurrence and number of seed migrations were analyzed. One or more seeds were identified on the chest X-rays of 55 (55%) of 100 patients. The mean number of intrathoracic seeds in patients with migration was 2.2 (range, 1–10), and the proportion of seeds that migrated to the thorax was 0.98%. The rate of extraprostatic seeds planned was 43.9%, and postimplant CT identified 37.9% in such a location. The number of seeds planned for extraprostatic placement and below the apex were statistically significant (alpha = 0.05) predictors in univariate logistic analysis. Multivariate analysis revealed the planned number of extraprostatic seeds as the only statistically significant predictor (p = 0.04). Extraprostatic placement of loose seeds is associated with an increased likelihood for, and frequency of, seed migration to the thorax. Nonetheless, the small proportion of implanted seeds that migrated (⩽1%) is highly unlikely to have significant dosimetric consequences.

Rapid strand™ vs. loose (iodine-125 seeds): A prospective randomized trial

Cure rates in the treatment of early stage prostate cancer with permanent interstitial brachytherapy are dependent on the delivery of adequate radiation doses to the prostate planned target volume. Successful post-implantation dosimetry is reliant upon the accuracy of seed placement and the ability to prevent seed migration and seed loss. The use of stranded radioactive seeds may decrease seed loss and migration in comparison to loose radioactive seeds. Fifty patients with 1997 AJCC clinical stage T1c-T2a prostate carcinoma were prospectively randomized to implantation with RAPID Strand I125 seeds (RS) (Amersham, Chicago, IL) vs. loose I125 seeds (LS) (Amersham, Chicago, IL). Isotope implantation was performed with standard techniques, using a preplanned modified peripheral loading pattern. CT and MR imaging, and anterior pelvic plain films were obtained on postimplant day 0 (D0) and day 30 (D30). Post-implant dosimetry was performed with a Varian treatment planning system on day 0 and day 30, with manual seed identification and redundancy check. Prostate volumes were contoured using CT and MR fusion. Seed loss and standard dosimetric parameters were compared on day 0 and day 30 between patients treated with RAPID Strand seeds to those treated with loose seeds. Patient characteristics were similar in both treatment groups. A statistically significant difference occurred in patients loosing seeds between RAPID Strand and loose seeds 16% vs. 48% respectively (p = 0.02). A significant difference occurred in patients loosing > 1 seed, 32% (LS) and 4% (RS) (p = 0.03), and in >2 seed loss 24% (LS) and 0% (RS) (p = 0.01). Of patients loosing seeds a statistically significant difference occurred in the number of seeds lost with a mean 2.5 seeds lost (LS) vs. 1.3 (RS) (p = 0.03). The mean D0 V100 was 96% (LS) and 94% for (RS) (p = 0.5). The mean D30 V100 was 94% (LS) and 91% (RS) (p = 0.2). In patients loosing seeds the mean D0 V100 was 94% (LS) and 97% for (RS) (p = 0.09). The mean D30 V100 was 93% (LS) and 94% (RS) (p = 0.9). RAPID Strand I125 seeds demonstrated a statistically significant lower rate of seed loss in comparison to loose seeds in patients undergoing interstitial transperineal prostate brachytherapy. Additionally stranded seeds resulted in a statistically significant decrease in the number of seeds lost per patient when seed loss occurred. Although no statistically significant overall difference was seen in dosimetric parameters between the treatment groups, an increase in day 0 and day 30 V100 was seen in patients loosing seeds favoring (RS).

Radioactive seed migration to the chest after transperineal interstitial prostate brachytherapy: extraprostatic seed placement correlates with migration

Purpose To examine the incidence of seed migration detected on chest X-ray and to identify the predictors associated with its occurrence. Methods and materials Between May 1998 and April 2000, 102 patients underwent permanent prostate brachytherapy at our institution and 100 were eligible for the study. Chest X-rays obtained at follow-up were examined for the number and location of seeds. The patient and treatment variables potentially associated with the occurrence and number of seed migrations were analyzed. Results One or more seeds were identified on the chest X-rays of 55 (55%) of 100 patients. The mean number of intrathoracic seeds in patients with migration was 2.2 (range, 1–10), and the proportion of seeds that migrated to the thorax was 0.98%. The rate of extraprostatic seeds planned was 43.9%, and postimplant CT identified 37.9% in such a location. The number of seeds planned for extraprostatic placement and below the apex were statistically significant (α = 0.05) predictors in univariate logistic analysis. Multivariate analysis revealed the planned number of extraprostatic seeds as the only statistically significant predictor ( p = 0.04). Conclusion Extraprostatic placement of loose seeds is associated with an increased likelihood for, and frequency of, seed migration to the thorax. Nonetheless, the small proportion of implanted seeds that migrated (≤1%) is highly unlikely to have significant dosimetric consequences.

A comparison of the precision of seeds deposited as loose seeds versus suture embedded seeds: a randomized trial

Purpose Brachytherapy for prostate cancer with permanent low–dose-rate seeds has been shown to be an effective treatment for early stage prostate cancer. Due to the rapid falloff of dose, accurate seed placement is critical for optimal dosimetry. One approach to achieve optimal dosimetry is the use of seeds embedded in suture material. Seeds embedded in suture may not move after implantation as much as loose seeds. This would improve implant dosimetry. To evaluate this hypothesis a formal study was conducted in which half the gland was implanted with seeds embedded in suture and half with loose seeds. Final dosimetry is compared between both halves of the prostate. Methods and materials Patients entered this Investigational Review Board approved prospective trial after completion of informed consent. At time of implant, the side of the gland to be implanted with loose as opposed to suture embedded seeds was randomly assigned. The patients then underwent intraoperative preplanned implantation. None of the preplans directed seed locations outside the prostate. Both the seeds embedded in suture and the loose seeds were implanted using needles with stylettes. At 4–6 weeks post implant, seed location was determined with CT. Both sides of the gland on CT were contoured and used for final dosimetric calculations. A cost function analysis was used to determine individual seed position deviation from intended to actual seed location. Results Eight patients were enrolled in the study. A total of 549 seeds were implanted; 240 seeds embedded in suture and 309 loose seeds. Prostate volumes ranged from 24.0–45.5 cc with a mean of 38.6 cc. The average radial deviation of the loose seeds from planned position was determined to be 3.1 mm compared with the average radial deviation of the suture embedded seeds of 3.7 mm. There was no improvement in the final dosimetry when suture embedded seeds where used. The D90 and V100 values for the half of the prostate implanted with suture embedded seeds were 71–140 (mean, 92.1) and 80.2–99.5 (mean, 89.6), respectively, for the half of the prostate implanted with loose seeds. (All D90, V100 values are % of prescription dose.) Conclusion Seeds embedded in suture material do not lead to superior precision in seed deposition when compared with loose seeds, when implanted inside the prostate.