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Vol 18, No 5 (2013)
Original research articles
Published online: 2013-09-01
Submitted: 2012-04-20
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Radiobiological comparison of two radiotherapy treatment techniques for high-risk prostate cancer

Trinitat García Hernández, Aurora Vicedo González, Jorge Pastor Peidro, Juan V. Ferrando, Luis Brualla González, Domingo Granero Cabañero, José López Torrecilla
DOI: 10.1016/j.rpor.2012.12.006
·
Rep Pract Oncol Radiother 2013;18(5):265-271.

open access

Vol 18, No 5 (2013)
Original research articles
Published online: 2013-09-01
Submitted: 2012-04-20

Abstract

Background

To make a radiobiological comparison, for high risk prostate cancer (T3a, PSA[[ce:hsp sp="0.25"/]]>[[ce:hsp sp="0.25"/]]20[[ce:hsp sp="0.25"/]]ng/ml or Gleason[[ce:hsp sp="0.25"/]]>[[ce:hsp sp="0.25"/]]7) of two radiotherapy treatment techniques. One technique consists of a treatment in three phases of the pelvic nodes, vesicles and prostate using a conventional fractionation scheme of 2[[ce:hsp sp="0.25"/]]Gy/fraction (SIMRT). The other technique consists of a treatment in two phases that gives simultaneously different dose levels in each phase, 2[[ce:hsp sp="0.25"/]]Gy/fraction, 2.25[[ce:hsp sp="0.25"/]]Gy/fraction and 2.5[[ce:hsp sp="0.25"/]]Gy/fraction to the pelvic nodes, vesicles and prostate, respectively (SIBIMRT).

Materials and methods

The equivalent dose at fractionation of 2[[ce:hsp sp="0.25"/]]Gy (EQD2), calculated using the linear quadratic model with α/βprostate[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]1.5[[ce:hsp sp="0.25"/]]Gy, was the same for both treatment strategies. For comparison the parameters employed were D95, mean dose and Tumour Control Probabilities for prostate PTV and D15, D25, D35, D50, mean dose and Normal Tissue Complication Probabilities for the rectum and bladder, with physical doses converted to EQD2. Parameters were obtained for α/βprostate[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]1.5, 3 and 10[[ce:hsp sp="0.25"/]]Gy and for α/βoar[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]1, 2, 3, 4, 6 and 8.

Results

For prostate PTV, both treatment strategies are equivalent for α/βprostate[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]1.5[[ce:hsp sp="0.25"/]]Gy but for higher α/βprostate, EQD2 and TCP, decrease for the SIBIMRT technique. For the rectum and bladder when α/βoar[[ce:hsp sp="0.25"/]]≤[[ce:hsp sp="0.25"/]]2[[ce:hsp sp="0.25"/]]Gy, EQD2 and NTCP are lower for the SIMRT technique or equal in both techniques. For α/βoar[[ce:hsp sp="0.25"/]]≥[[ce:hsp sp="0.25"/]]2–3[[ce:hsp sp="0.25"/]]Gy, EQD2 and NTCP increase for the SIMRT treatment.

Conclusions

A comparison between two radiotherapy techniques is presented. The SIBIMRT technique reduces EQD2 and NTCP for α/βoar from 2 to 8[[ce:hsp sp="0.25"/]]Gy.

Abstract

Background

To make a radiobiological comparison, for high risk prostate cancer (T3a, PSA[[ce:hsp sp="0.25"/]]>[[ce:hsp sp="0.25"/]]20[[ce:hsp sp="0.25"/]]ng/ml or Gleason[[ce:hsp sp="0.25"/]]>[[ce:hsp sp="0.25"/]]7) of two radiotherapy treatment techniques. One technique consists of a treatment in three phases of the pelvic nodes, vesicles and prostate using a conventional fractionation scheme of 2[[ce:hsp sp="0.25"/]]Gy/fraction (SIMRT). The other technique consists of a treatment in two phases that gives simultaneously different dose levels in each phase, 2[[ce:hsp sp="0.25"/]]Gy/fraction, 2.25[[ce:hsp sp="0.25"/]]Gy/fraction and 2.5[[ce:hsp sp="0.25"/]]Gy/fraction to the pelvic nodes, vesicles and prostate, respectively (SIBIMRT).

Materials and methods

The equivalent dose at fractionation of 2[[ce:hsp sp="0.25"/]]Gy (EQD2), calculated using the linear quadratic model with α/βprostate[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]1.5[[ce:hsp sp="0.25"/]]Gy, was the same for both treatment strategies. For comparison the parameters employed were D95, mean dose and Tumour Control Probabilities for prostate PTV and D15, D25, D35, D50, mean dose and Normal Tissue Complication Probabilities for the rectum and bladder, with physical doses converted to EQD2. Parameters were obtained for α/βprostate[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]1.5, 3 and 10[[ce:hsp sp="0.25"/]]Gy and for α/βoar[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]1, 2, 3, 4, 6 and 8.

Results

For prostate PTV, both treatment strategies are equivalent for α/βprostate[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]1.5[[ce:hsp sp="0.25"/]]Gy but for higher α/βprostate, EQD2 and TCP, decrease for the SIBIMRT technique. For the rectum and bladder when α/βoar[[ce:hsp sp="0.25"/]]≤[[ce:hsp sp="0.25"/]]2[[ce:hsp sp="0.25"/]]Gy, EQD2 and NTCP are lower for the SIMRT technique or equal in both techniques. For α/βoar[[ce:hsp sp="0.25"/]]≥[[ce:hsp sp="0.25"/]]2–3[[ce:hsp sp="0.25"/]]Gy, EQD2 and NTCP increase for the SIMRT treatment.

Conclusions

A comparison between two radiotherapy techniques is presented. The SIBIMRT technique reduces EQD2 and NTCP for α/βoar from 2 to 8[[ce:hsp sp="0.25"/]]Gy.

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Keywords

Radiobiology; Simultaneous integrated boost; NTCP; Equivalent dose at fractionation of 2[[ce:hsp sp=" 0.25" /]]Gy (EQD2); Prostate

About this article
Title

Radiobiological comparison of two radiotherapy treatment techniques for high-risk prostate cancer

Journal

Reports of Practical Oncology and Radiotherapy

Issue

Vol 18, No 5 (2013)

Pages

265-271

Published online

2013-09-01

DOI

10.1016/j.rpor.2012.12.006

Bibliographic record

Rep Pract Oncol Radiother 2013;18(5):265-271.

Keywords

Radiobiology
Simultaneous integrated boost
NTCP
Equivalent dose at fractionation of 2[[ce:hsp sp="0.25"/]]Gy (EQD2)
Prostate

Authors

Trinitat García Hernández
Aurora Vicedo González
Jorge Pastor Peidro
Juan V. Ferrando
Luis Brualla González
Domingo Granero Cabañero
José López Torrecilla

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