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Technical and dosimetric aspects of iodine-125 seed reimplantation in suboptimal prostate implants.

ABSTRACT: OBJECTIVE: Brachytherapy employing iodine-125 seeds is an established treatment for low-risk prostate cancers. Post-implant dosimetry (PID) is an important tool for identifying suboptimal implants. The aim of this work was to improve suboptimal implants by a subsequent iodine-125 seed top-up (reimplantation), based on the PID results. METHODS: Of 255 patients treated between 2009 and 2012, 6 were identified as having received suboptimal implants and were scheduled for seed top-up. Needle configurations and the number of top-up seeds were determined based on post-implant CT images as well as a reimplantation treatment plan. An average of 14 seeds per patient were implanted during each top-up. Dosimetric outcome was assessed via target parameters and doses received by organs at risk. RESULTS: All six patients had a successful top-up, with a 67% increase in the mean dose delivered to 90% of the prostate volume and a 40% increase in the volume that receives 100% of the prescribed dose. However, the final dosimetric assessment was based on the same seed activity, as the planning system does not account for the decay of the initially implanted seeds. Although physical dosimetry is not influenced by different seed activities (doses are calculated to infinity), the radiobiological implications might be slightly different from the situation when optimal implantation is achieved with one treatment only. CONCLUSION: Seed reimplantation in suboptimal prostate implants is feasible and leads to successful clinical outcomes. ADVANCES IN KNOWLEDGE: Suboptimal prostate implants can occur for various reasons. This work shows that seed reimplantation as salvage therapy can lead to an optimal dosimetric outcome with manageable normal tissue effects.

SUBMITTER: Marcu LG

PROVIDER: S-EPMC3664978 | biostudies-other | 2013 Jun

REPOSITORIES: biostudies-other

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Project description:Purpose:To investigate chronological changes in lower urinary tract symptoms (LUTS) in patients who received iodine-125 brachytherapy (BT) for prostate cancer. Methods:We enrolled 706 patients who received BT. Of these, 265 (38%) received BT combined with external beam radiation therapy (EBRT). An International Prostate Symptom Score (IPSS), IPSS quality of life (IPSS-QOL) score, and overactive bladder symptom score (OABSS) were recorded before BT (baseline, BL), and 1, 3, 6, 12, 24, 36, 48, and 60?months after BT. The sum of frequency (2), urgency (4) and nocturia (7) of the IPSS questionnaire was defined as the storage symptoms score, whereas the sum of emptying (1), intermittency (3), weak stream (5), and hesitancy (6) was defined as the voiding symptom score. Results:Total IPSS significantly increased at 3?months following BT compared with BL (mean score: 17.1 vs. 7.99, P?<?0.001) and returned to BL by 36?months. The storage symptom score did not return to BL 36?months after BT. Total OABSS significantly increased 3?months after BT compared with BL (mean score: 6.52 vs. 3.45, P?<?0.001), and returned to BL 48?months after BT. The IPSS-QOL score was the highest score (mean score: 2.46 vs. 3.9, P?<?0.001) 3?months after BT and returned to BL 48?months after BT, however the IPSS-QOL score was lower than BL (mean score: 2.01 vs 2.46, P?<?0.001) at 60?months. The risk factors for LUTS within 1?year after BT were BL IPSS (P?<?0.001) and PV (P?<?0.001). Patients who received combined EBRT experienced transient storage symptoms 24 and 36?months after BT, whereas those who received BT alone did not. However, the storage symptom score of the patients who received combined EBRT was improving 48?months after BT and eventually showed no significant difference compared with those treated with BT alone. Conclusion:Three months after BT, LUTS, including storage symptoms, deteriorated the most but improved with time. The urinary symptom in patients who received combined EBRT can potentially flare again in 24 and 36?months after BT. Knowledge of changes in LUTS associated with BT may influence treatment recommendations and enable patients to make better-informed decisions.

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Technical and dosimetric aspects of iodine-125 seed reimplantation in suboptimal prostate implants.

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