Patient's specific integration of OAR doses (D2 cc) from EBRT and 3D image‐guided brachytherapy for cervical cancer

Abstract

The objective of this study was to assess the recommended DVH parameter (e.g., D2 cc) addition method used for combining EBRT and HDR plans, against a reference dataset generated from an EQD2‐based DVH addition method. A revised DVH parameter addition method using EBRT DVH parameters derived from each patient's plan was proposed and also compared with the reference dataset. Thirty‐one biopsy‐proven cervical cancer patients who received EBRT and HDR brachytherapy were retrospectively analyzed. A parametrial and/or paraaortic EBRT boost were clinically performed on 13 patients. Ten IMRT and 21 3DCRT plans were determined. Two different HDR techniques for each HDR plan were analyzed. Overall D2 cc and D0.1 cc OAR doses in EQD2 were statistically analyzed for three different DVH parameter addition methods: a currently recommended method, a proposed revised method, and a reference DVH addition method. The overall D2 ccEQD 2 values for all rectum, bladder, and sigmoid for a conformal, volume optimization HDR plan generated using the current DVH parameter addition method were significantly underestimated on average −5 to −8% when compared to the values obtained from the reference DVH addition technique (P < 0.01). The revised DVH parameter addition method did not present statistical differences with the reference technique (P > 0.099). When PM boosts were considered, there was an even greater average underestimation of −8~−10% for overall OAR doses of conformal HDR plans when using the current DVH parameter addition technique as compared to the revised DVH parameter addition. No statistically significant differences were found between the 3DCRT and IMRT techniques (P > 0.3148). It is recommended that the overall D2 cc EBRT doses are obtained from each patient's EBRT plan.

Dosimetry of the bowel as a risk organ in intracavitary gynecologic image guided 3D brachytherapy

“…The second method he describes involves obtaining the D2cc specific value of each organ at risk in external radiotherapy initial planning and adding it to the D2cc of each brachytherapy application. In his study, said author compared both methods in the rectum, sigmoid and bladder, and concluded that there is a D2cc underestimation ranging from 4.7 to 8.3% when the method of assuming that all the external radiotherapy prescribed dose was received is used, but that there is no significant difference when compared with the method of obtaining the D2cc of each external radiotherapy planning, to conclude that, due to this underestimation, obtaining the D2cc of each external radiation therapy plan is preferable 18 .…”

Dosimetría del intestino delgado como órgano de riesgo en la braquiterapia ginecológica intracavitaria 3D guiada por imagen

“…El segundo método que describe es obtener el valor específico de la D2cc de cada órgano de riesgo en la planeación inicial de la radioterapia externa y sumarlo a la D2cc de cada aplicación de braquiterapia. En su estudio, dicho autor comparó ambos métodos en recto, sigmoides y vejiga, concluyendo que existe una subestimación de la D2cc que va del 4.7 al 8.3% cuando se utiliza el método de asumir que en la radioterapia externa se recibió la totalidad de la dosis prescrita, pero que no existe diferencia significativa cuando se compara con el método de obtener la D2cc de cada planeación de radioterapia externa concluyendo que, debido a esta subestimación es preferible obtener la D2cc de cada plan de radioterapia externa 18 . En nuestro caso, debido a que ordinariamente no se realiza el contorneo del intestino delgado en los planes de radioterapia externa a pelvis, se optó por utilizar el método de integración de la D2cc, que asume el recibir la totalidad de la dosis prescrita en la radioterapia externa para luego sumarle los valores de la D2cc de cada aplicación de braquiterapia tasa alta de dosis y así obtener la D2cc final del intestino delgado (integración radioterapia externa + braquiterapia).…”

Comparative analysis of image-guided adaptive interstitial brachytherapy and intensity-modulated arc therapy versus conventional treatment techniques in cervical cancer using biological dose summation

“…The fundamental reasons are the foreign body (plastic or metal applicator) in situ and the deformation of organs due to application. Other authors added BT and EBRT DVHs directly [ 15 ] or used rigid image registration [ 16 ] instead of DIR. We mimicked DIR ‘in mind’ by defining the most exposed 2 cc of critical organs in BT CT, and then delineating this volume on EBRT CT.…”

“…Gelover et al . [ 15 ] did not find statistically significant differences between EQD2 doses of OARs in conformal and IMRT EBRT techniques by adding EBRT and BT DVHs; however, they did not add the dose of the same volumes of OARs. In our analysis, D 2 (EQD2) of the rectum was significantly lower by 9 Gy (on average) in IMAT than in CONF EBRT plans.…”

“…In the intensity-modulated radiotherapy (IMRT) technique, the most exposed 2 cc of the OARs is not a disjunct volume, since its voxels are dispersed in the organ, as we showed earlier [ 14 ]. In previous investigations, authors added BT and EBRT dose-volume histogram (DVH) of EQD2 doses [ 15 ] or made rigid image registration of BT and EBRT CT or MR images [ 16 ]. It was also shown before that the most exposed part of the OARs in the integrated plans evolves in the region where the maximum dose is in BT.…”