open access

Vol 23, No 6 (2018)
Special Issue Papers
Published online: 2018-11-01
Submitted: 2017-11-09
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Radiobiological considerations in combining doses from external beam radiotherapy and brachytherapy for cervical cancer

Ana M. Tornero-López, Damián Guirado
DOI: 10.1016/j.rpor.2018.05.007
·
Rep Pract Oncol Radiother 2018;23(6):562-573.

open access

Vol 23, No 6 (2018)
Special Issue Papers
Published online: 2018-11-01
Submitted: 2017-11-09

Abstract

The recommended radio-therapeutic treatment for cervix cancer consists of a first phase of external beam radiotherapy (EBRT) plus a second phase of brachytherapy (BT), the combined treatment being delivered within 8 weeks.

In order to assess a comprehensive dosimetry of the whole treatment, it is necessary to take into account that these two phases are characterized by different spatial and temporal dosimetric distributions, which complicates the task of the summation of the two contributions, EBRT and BT. Radiobiology allows to tackle this issue pragmatically by means of the LQ model and, in fact, this is the usual tool currently in use for this matter.

In this work, we describe the rationale behind the summation of the dosimetric contributions of the two phases of the treatment, EBRT and BT, for cervix cancer, as carried out with the LQ model.

Besides, we address, from a radiobiological point of view, several important considerations regarding the use of the LQ model for this task. One of them is the analysis of the effect of the overall treatment time in the result of the global treatment. Another important question considered is related to the fact that the capacity of LQ to predict the treatment outcomes is deteriorated when the dose per fraction of the radiotherapic scheme exceeds 6–10Gy, which is a typical brachytherapy fractionation. Finally, we analyze the influence of the uncertainty and the variability of the main parameters utilized in the LQ model formulation in the assessment of the global dosimetry.

Abstract

The recommended radio-therapeutic treatment for cervix cancer consists of a first phase of external beam radiotherapy (EBRT) plus a second phase of brachytherapy (BT), the combined treatment being delivered within 8 weeks.

In order to assess a comprehensive dosimetry of the whole treatment, it is necessary to take into account that these two phases are characterized by different spatial and temporal dosimetric distributions, which complicates the task of the summation of the two contributions, EBRT and BT. Radiobiology allows to tackle this issue pragmatically by means of the LQ model and, in fact, this is the usual tool currently in use for this matter.

In this work, we describe the rationale behind the summation of the dosimetric contributions of the two phases of the treatment, EBRT and BT, for cervix cancer, as carried out with the LQ model.

Besides, we address, from a radiobiological point of view, several important considerations regarding the use of the LQ model for this task. One of them is the analysis of the effect of the overall treatment time in the result of the global treatment. Another important question considered is related to the fact that the capacity of LQ to predict the treatment outcomes is deteriorated when the dose per fraction of the radiotherapic scheme exceeds 6–10Gy, which is a typical brachytherapy fractionation. Finally, we analyze the influence of the uncertainty and the variability of the main parameters utilized in the LQ model formulation in the assessment of the global dosimetry.

Get Citation

Keywords

Cervix cancer; Brachytherapy; Combined treatment; Radiobiology; LQ model; Overall treatment time

About this article
Title

Radiobiological considerations in combining doses from external beam radiotherapy and brachytherapy for cervical cancer

Journal

Reports of Practical Oncology and Radiotherapy

Issue

Vol 23, No 6 (2018)

Pages

562-573

Published online

2018-11-01

DOI

10.1016/j.rpor.2018.05.007

Bibliographic record

Rep Pract Oncol Radiother 2018;23(6):562-573.

Keywords

Cervix cancer
Brachytherapy
Combined treatment
Radiobiology
LQ model
Overall treatment time

Authors

Ana M. Tornero-López
Damián Guirado

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