Methodology of dose calculation for external beam radiation combined with high dose rate brachytherapy in the era of 3-dimensional treatment planning system.

Intracavitary application of brachytherapy (BT) sources followed by external beam radiation is essential for the local treatment of carcinoma of the cervix, postate, and nasopharynx. Dose distribution of external beam radiation plus BT can be challenging for the planning system because of their dose calculation by 2 different treatment planning system (TPS). The aims of this study were to introduce a novel iterative method of dose calculation preformed in the Pinnacle plan and evaluate a combined dose distribution for external beam radiation and BT.Because it is often the goal of the planner to produce plan with uniform dose throughout the target volume and normal tissue, we present an Iridium-192 calculation program using American Association of Physicists in Medicine Task Group 43 formula and export it to other commercialized TPS though the combined dose distribution of external beam radiation and BT can be shown. To illustrate such an improved procedure, we present the treatment plans of 2 patients treated with external beam radiation plus BT.Dose distribution of the single BT source were calculated with the Plato post loading TPS and the program model, and the results of 2 methods were similar. A nasopharyngeal case and a cervical case were shown in Pinnacle with this program. The total dose distribution of BT combined with EBRT was showed in compute tomography images. And the corresponding dose volume histogram figures could be displayed correctly in Pinnacle TPS.We demonstrated a novel iterative method of dose calculation preformed in the Pinnacle plan to produce a combined dose distribution for external beam radiation and BT. We used it to evaluate the dose of target volume and normal tissues in the treatment of external beam radiation plus BT.

Braquiterapia como trataminto del cáncer de próstata clinicamente localizado: selección óptima de pacientes / Brachytherapy for clinically localized prostate cancer: optimal patient selection

En la última década, la braquiterapia de próstata se ha convertido en una modalidad curativa cada vez más utilizada para el cáncer de próstata clínicamente localizado; el 25% de todos los tumores en la primera fase son ahora tratados en Estados Unidos de esta forma (1). La popularidad de esta estrategia de tratamiento se encuentra en la naturaleza de la dosis de radiación (altamente conformada), baja morbilidad, comodidad del paciente, y altos índices de eficacia. La braquiterapia de próstata puede ser administrada bien por un implante intersticial permanente de semillas radiactivas (dosis de baja tasa [LDR]) o una inserción intersticial temporal de iridio-192 (Ir192). El objetivo de ambas técnicas es administrar una alta dosis de radiación a la glándula prostática, al mismo tiempo que la exposición de los tejidos normales circundantes a la dosis de radiación es mínima. Las técnicas de braquiterapia son ideales para lograr este objetivo, dada la cercanía de la fuente de radiación al tumor y alejado de la nube de la dosis de radiación próxima a la fuente. La braquiterapia es un buen método para administrar el aumento de dosis por encima y más allá de lo alcanzable con solamente la radioterapia de haz externo de intensidad modulada. Sin embargo, es fundamental para optimizar los resultados relacionados con la enfermedad y la toxicidad relativa al tratamiento, una cuidadosa selección de pacientes adecuados para estos tratamientos. El objetivo de esta revisión es presentar una visión general de cada modalidad y definir la forma de seleccionar mejor a los pacientes que son candidatos óptimos para estos enfoques de tratamiento(AU)

The objective of this review is to present an overview of each modality and delineate how to best select patients who are optimal candidates for these treatment approaches. Prostate brachytherapy as a curative modality for clinically localized prostate cancer has become increasingly utilized over the past decade; 25% of all early cancers are now treated this way in the United States (1). The popularity of this treatment strategy lies in the highly conformal nature of radiation dose, low morbidity, patient convenience, and high efficacy rates. Prostate brachytherapy can be delivered by either a permanent interstitial radioactive seed implantation (low dose rate [LDR]) or a temporary interstitial insertion of iridium-192 (Ir192) after loading catheters. The objective of both of these techniques is to deliver a high dose of radiation to the prostate gland while exposing normal surrounding tissues to minimal radiation dose. Brachytherapy techniques are ideal to achieve this goal given the close proximity of the radiation source to tumor and sharp fall off of the radiation dose cloud proximate to the source. Brachytherapy provides a powerful means of delivering dose escalation above and beyond that achievable with intensity-modulated external beam radiotherapy alone. Care full selection of appropriate patients for these therapies, however, is critical for optimizing both disease-related outcomes and treatment-related toxicity(AU)

Increased tumour response of a murine fibrosarcoma to low temperature hyperthermia and low dose rate brachytherapy.

The present animal tumour study was carried out to determine the effectiveness of low temperature hyperthermia combined with low dose rate radiation based on the cell culture studies of our laboratory and others that demonstrated a significant radiosensitization obtained by low temperature hyperthermia and low dose rate radiation. Well-oxygenated murine fibrosarcoma Meth-A tumours growing in Balb/c mice were treated with heat (41 degrees C tumour temperature) by immersion of the tumour-bearing leg in a waterbath concurrently with low dose rate radiation. Radiation was delivered using 192Ir interstitial implantation at absolute dose rates of 0.416-0.542 Gy/h. The effect of heat alone on tumour growth and normal tissue was minimal. Tumour growth delay following 30 Gy radiation was 4.9 days. Significant delay in tumour growth was observed with the addition of low temperature hyperthermia delivered concurrently. Enhancement in radiation response was seen with increasing duration of heat treatment; tumour growth delays were 9.5 days following 4 h heat (41 degrees C) treatment and 16 days following 6 h treatment. Three sessions of fractionated hyperthermia 4 h/day during the course of low dose-rate radiation significantly delayed tumour growth to 18.6 days. The results indicate that fractionated heat treatment in conjunction with low dose rate radiation has potential for improving tumour response without adversely affecting normal tissue reaction. This in vivo study represents an extension of the cell culture data and provides further radiobiological basis for the combined use of low temperature hyperthermia and low dose rate radiation.