Development of a standardized method for contouring the lumbosacral plexus

A preliminary dosimetric analysis of this organ at risk among 15 patients treated with intensity-modulated radiotherapy for lower gastrointestinal cancers and the incidence of radiation-induced lumbosacral plexopathy

Sun K. Yi, Walter Mak, Claus C. Yang, Tianxiao Liu, Jing Cui, Allen M. Chen, James A. Purdy, Arta M Monjazeb, Ly Do

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Abstract

Purpose: To generate a reproducible step-wise guideline for the delineation of the lumbosacral plexus (LSP) on axial computed tomography (CT) planning images and to provide a preliminary dosimetric analysis on 15 representative patients with rectal or anal cancers treated with an intensity-modulated radiotherapy (IMRT) technique. Methods and Materials: A standardized method for contouring the LSP on axial CT images was devised. The LSP was referenced to identifiable anatomic structures from the L4-5 interspace to the level of the sciatic nerve. It was then contoured retrospectively on 15 patients treated with IMRT for rectal or anal cancer. No dose limitations were placed on this organ at risk during initial treatment planning. Dosimetric parameters were evaluated. The incidence of radiation-induced lumbosacral plexopathy (RILSP) was calculated. Results: Total prescribed dose to 95% of the planned target volume ranged from 50.4 to 59.4 Gy (median 54 Gy). The mean (±standard deviation [SD]) LSP volume for the 15 patients was 100 ± 22 cm 3 (range, 71-138 cm 3). The mean maximal dose to the LSP was 52.6 ± 3.9 Gy (range, 44.5-58.6 Gy). The mean irradiated volumes of the LSP were V40Gy = 58% ± 19%, V50Gy = 22% ± 23%, and V55Gy = 0.5% ± 0.9%. One patient (7%) was found to have developed RILSP at 13 months after treatment. Conclusions: The true incidence of RILSP in the literature is likely underreported and is not a toxicity commonly assessed by radiation oncologists. In our analysis the LSP commonly received doses approaching the prescribed target dose, and 1 patient developed RILSP. Identification of the LSP during IMRT planning may reduce RILSP. We have provided a reproducible method for delineation of the LSP on CT images and a preliminary dosimetric analysis for potential future dose constraints.

Original languageEnglish (US)
Pages (from-to)376-382
Number of pages7
JournalInternational Journal of Radiation Oncology Biology Physics
Volume84
Issue number2
DOIs
StatePublished - Oct 1 2012

Fingerprint

Lumbosacral Plexus
Organs at Risk
Intensity-Modulated Radiotherapy
Gastrointestinal Neoplasms
organs
radiation therapy
incidence
cancer
Radiation
dosage
Incidence
radiation
planning
delineation
tomography
Anus Neoplasms
Tomography
Rectal Neoplasms
nerves
toxicity

Keywords

  • Contouring atlas
  • IMRT
  • Incidence
  • Lumbosacral plexus
  • Radiation-induced lumbosacral plexopathy

ASJC Scopus subject areas

  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Radiation
  • Cancer Research

Cite this

@article{a4e50980283640e8b0d161f119f61c61,
title = "Development of a standardized method for contouring the lumbosacral plexus: A preliminary dosimetric analysis of this organ at risk among 15 patients treated with intensity-modulated radiotherapy for lower gastrointestinal cancers and the incidence of radiation-induced lumbosacral plexopathy",
abstract = "Purpose: To generate a reproducible step-wise guideline for the delineation of the lumbosacral plexus (LSP) on axial computed tomography (CT) planning images and to provide a preliminary dosimetric analysis on 15 representative patients with rectal or anal cancers treated with an intensity-modulated radiotherapy (IMRT) technique. Methods and Materials: A standardized method for contouring the LSP on axial CT images was devised. The LSP was referenced to identifiable anatomic structures from the L4-5 interspace to the level of the sciatic nerve. It was then contoured retrospectively on 15 patients treated with IMRT for rectal or anal cancer. No dose limitations were placed on this organ at risk during initial treatment planning. Dosimetric parameters were evaluated. The incidence of radiation-induced lumbosacral plexopathy (RILSP) was calculated. Results: Total prescribed dose to 95{\%} of the planned target volume ranged from 50.4 to 59.4 Gy (median 54 Gy). The mean (±standard deviation [SD]) LSP volume for the 15 patients was 100 ± 22 cm 3 (range, 71-138 cm 3). The mean maximal dose to the LSP was 52.6 ± 3.9 Gy (range, 44.5-58.6 Gy). The mean irradiated volumes of the LSP were V40Gy = 58{\%} ± 19{\%}, V50Gy = 22{\%} ± 23{\%}, and V55Gy = 0.5{\%} ± 0.9{\%}. One patient (7{\%}) was found to have developed RILSP at 13 months after treatment. Conclusions: The true incidence of RILSP in the literature is likely underreported and is not a toxicity commonly assessed by radiation oncologists. In our analysis the LSP commonly received doses approaching the prescribed target dose, and 1 patient developed RILSP. Identification of the LSP during IMRT planning may reduce RILSP. We have provided a reproducible method for delineation of the LSP on CT images and a preliminary dosimetric analysis for potential future dose constraints.",
keywords = "Contouring atlas, IMRT, Incidence, Lumbosacral plexus, Radiation-induced lumbosacral plexopathy",
author = "Yi, {Sun K.} and Walter Mak and Yang, {Claus C.} and Tianxiao Liu and Jing Cui and Chen, {Allen M.} and Purdy, {James A.} and Monjazeb, {Arta M} and Ly Do",
year = "2012",
month = "10",
day = "1",
doi = "10.1016/j.ijrobp.2011.11.074",
language = "English (US)",
volume = "84",
pages = "376--382",
journal = "International Journal of Radiation Oncology Biology Physics",
issn = "0360-3016",
publisher = "Elsevier Inc.",
number = "2",

}

TY - JOUR

T1 - Development of a standardized method for contouring the lumbosacral plexus

T2 - A preliminary dosimetric analysis of this organ at risk among 15 patients treated with intensity-modulated radiotherapy for lower gastrointestinal cancers and the incidence of radiation-induced lumbosacral plexopathy

AU - Yi, Sun K.

AU - Mak, Walter

AU - Yang, Claus C.

AU - Liu, Tianxiao

AU - Cui, Jing

AU - Chen, Allen M.

AU - Purdy, James A.

AU - Monjazeb, Arta M

AU - Do, Ly

PY - 2012/10/1

Y1 - 2012/10/1

N2 - Purpose: To generate a reproducible step-wise guideline for the delineation of the lumbosacral plexus (LSP) on axial computed tomography (CT) planning images and to provide a preliminary dosimetric analysis on 15 representative patients with rectal or anal cancers treated with an intensity-modulated radiotherapy (IMRT) technique. Methods and Materials: A standardized method for contouring the LSP on axial CT images was devised. The LSP was referenced to identifiable anatomic structures from the L4-5 interspace to the level of the sciatic nerve. It was then contoured retrospectively on 15 patients treated with IMRT for rectal or anal cancer. No dose limitations were placed on this organ at risk during initial treatment planning. Dosimetric parameters were evaluated. The incidence of radiation-induced lumbosacral plexopathy (RILSP) was calculated. Results: Total prescribed dose to 95% of the planned target volume ranged from 50.4 to 59.4 Gy (median 54 Gy). The mean (±standard deviation [SD]) LSP volume for the 15 patients was 100 ± 22 cm 3 (range, 71-138 cm 3). The mean maximal dose to the LSP was 52.6 ± 3.9 Gy (range, 44.5-58.6 Gy). The mean irradiated volumes of the LSP were V40Gy = 58% ± 19%, V50Gy = 22% ± 23%, and V55Gy = 0.5% ± 0.9%. One patient (7%) was found to have developed RILSP at 13 months after treatment. Conclusions: The true incidence of RILSP in the literature is likely underreported and is not a toxicity commonly assessed by radiation oncologists. In our analysis the LSP commonly received doses approaching the prescribed target dose, and 1 patient developed RILSP. Identification of the LSP during IMRT planning may reduce RILSP. We have provided a reproducible method for delineation of the LSP on CT images and a preliminary dosimetric analysis for potential future dose constraints.

AB - Purpose: To generate a reproducible step-wise guideline for the delineation of the lumbosacral plexus (LSP) on axial computed tomography (CT) planning images and to provide a preliminary dosimetric analysis on 15 representative patients with rectal or anal cancers treated with an intensity-modulated radiotherapy (IMRT) technique. Methods and Materials: A standardized method for contouring the LSP on axial CT images was devised. The LSP was referenced to identifiable anatomic structures from the L4-5 interspace to the level of the sciatic nerve. It was then contoured retrospectively on 15 patients treated with IMRT for rectal or anal cancer. No dose limitations were placed on this organ at risk during initial treatment planning. Dosimetric parameters were evaluated. The incidence of radiation-induced lumbosacral plexopathy (RILSP) was calculated. Results: Total prescribed dose to 95% of the planned target volume ranged from 50.4 to 59.4 Gy (median 54 Gy). The mean (±standard deviation [SD]) LSP volume for the 15 patients was 100 ± 22 cm 3 (range, 71-138 cm 3). The mean maximal dose to the LSP was 52.6 ± 3.9 Gy (range, 44.5-58.6 Gy). The mean irradiated volumes of the LSP were V40Gy = 58% ± 19%, V50Gy = 22% ± 23%, and V55Gy = 0.5% ± 0.9%. One patient (7%) was found to have developed RILSP at 13 months after treatment. Conclusions: The true incidence of RILSP in the literature is likely underreported and is not a toxicity commonly assessed by radiation oncologists. In our analysis the LSP commonly received doses approaching the prescribed target dose, and 1 patient developed RILSP. Identification of the LSP during IMRT planning may reduce RILSP. We have provided a reproducible method for delineation of the LSP on CT images and a preliminary dosimetric analysis for potential future dose constraints.

KW - Contouring atlas

KW - IMRT

KW - Incidence

KW - Lumbosacral plexus

KW - Radiation-induced lumbosacral plexopathy

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DO - 10.1016/j.ijrobp.2011.11.074

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