RESUMEN
INTRODUCTION: We report the first 100 patients who underwent prostate brachytherapy as monotherapy with 125I at an institution with moderate volume radical prostatectomy but low volume brachytherapy (<2 cases per month). Learning curve and quality improvement was assessed by way of achieving prescription dose targets. MATERIALS AND METHODS: From May 2002 to August 2006, 100 patients underwent prostate 125I brachytherapy monotherapy via preplanned approach. Preoperative planned dose to 100% of prostate gland (D100) was 145 Gy and postoperative confirmed dose was assessed by computed tomography. The cohort was divided into quartiles and recurrence was assessed using Kaplan-Meier analysis. RESULTS: Patient quartiles were of similar age and Gleason grade, while PSA was slightly higher in the first group. Postoperative D90 increased after the first quartile (p = < 0.0001) reaching targeted values. Kaplan-Meier survival analysis revealed that 5 year recurrence-free survivals by Phoenix definition was 96%-100% in all groups while by ASTRO definition there was a decrease in recurrence for later cases. CONCLUSIONS: At our low volume institution during the first 100 brachytherapy cases, a learning curve for radiation dosimetry was evident, which improved after 25 patients. Preplanned dose-volume parameters were adjusted, enabling the achievement of post-implant goals emphasizing the importance of continuous quality improvement. Although recurrence data is limited by sample size and moderate follow up, there was a discrepancy between the Phoenix and ASTRO definition when evaluating recurrence.
Asunto(s)
Braquiterapia/métodos , Hospitales de Bajo Volumen/tendencias , Curva de Aprendizaje , Neoplasias de la Próstata/radioterapia , Mejoramiento de la Calidad/tendencias , Anciano , Estudios de Cohortes , Relación Dosis-Respuesta en la Radiación , Humanos , Estimación de Kaplan-Meier , Masculino , Persona de Mediana Edad , Neoplasias de la Próstata/mortalidad , Mejoramiento de la Calidad/normas , Calidad de la Atención de Salud/normas , Calidad de la Atención de Salud/tendencias , Estudios Retrospectivos , Tasa de Supervivencia , Resultado del TratamientoRESUMEN
PURPOSE: Determine the degree of interfraction prostate motion and its components measured by using daily megavoltage (MV) cone beam computed tomography (CBCT) imaging. METHODS AND MATERIALS: A total of 984 daily MV CBCT images from 24 patients undergoing definitive intensity-modulated radiotherapy for localized prostate cancer were analyzed retrospectively. Pretreatment couch shifts, based on physician registration of MV CBCT to planning CT data sets, were used as a measure of daily interfraction motion. Off-line bony registration was performed to separate bony misalignment from internal organ motion. Interobserver and intraobserver variation studies were performed on 20 MV CBCT images. RESULTS: Mean interfraction prostate motion was 6.7 mm, with the greatest single-axis deviation in the anterior-posterior (AP) direction. The largest positional inaccuracy was accounted for by systematic deviations in bony misalignment, whereas random deviations occurred from bony misalignment and internal prostate motion. In the aggregate, AP motion did not correlate with days elapsed since beginning therapy or on average with rectal size at treatment planning. Interobserver variation was greatest in the AP direction, decreased in experienced observers, and further decreased in intraobserver studies. Mean interfraction motion during the first 6 days of therapy, when used as a subsequent offset, reduced acceptable AP planning target volume margins by 50%. CONCLUSION: The MV CBCT is a practical direct method of daily localization that shows significant interfraction motion with respect to conventional three-dimensional conformal and intensity-modulated radiotherapy margins, similar to that measured in other modalities.