Australasian Gastrointestinal Trials Group (AGITG) Contouring Atlas and Planning Guidelines for Intensity-Modulated Radiotherapy in Anal Cancer

doi:10.1016/j.ijrobp.2011.12.058

International Journal of Radiation OncologyBiologyPhysics

Volume 83, Issue 5, 1 August 2012, Pages 1455-1462

https://doi.org/10.1016/j.ijrobp.2011.12.058 Get rights and content

Purpose

To develop a high-resolution target volume atlas with intensity-modulated radiotherapy (IMRT) planning guidelines for the conformal treatment of anal cancer.

Methods and Materials

A draft contouring atlas and planning guidelines for anal cancer IMRT were prepared at the Australasian Gastrointestinal Trials Group (AGITG) annual meeting in September 2010. An expert panel of radiation oncologists contoured an anal cancer case to generate discussion on recommendations regarding target definition for gross disease, elective nodal volumes, and organs at risk (OARs). Clinical target volume (CTV) and planning target volume (PTV) margins, dose fractionation, and other IMRT-specific issues were also addressed. A steering committee produced the final consensus guidelines.

Results

Detailed contouring and planning guidelines and a high-resolution atlas are provided. Gross tumor and elective target volumes are described and pictorially depicted. All elective regions should be routinely contoured for all disease stages, with the possible exception of the inguinal and high pelvic nodes for select, early-stage T1N0. A 20-mm CTV margin for the primary, 10- to 20-mm CTV margin for involved nodes and a 7-mm CTV margin for the elective pelvic nodal groups are recommended, while respecting anatomical boundaries. A 5- to 10-mm PTV margin is suggested. When using a simultaneous integrated boost technique, a dose of 54 Gy in 30 fractions to gross disease and 45 Gy to elective nodes with chemotherapy is appropriate. Guidelines are provided for OAR delineation.

Conclusion

These consensus planning guidelines and high-resolution atlas complement the existing Radiation Therapy Oncology Group (RTOG) elective nodal ano-rectal atlas and provide additional anatomic, clinical, and technical instructions to guide radiation oncologists in the planning and delivery of IMRT for anal cancer.

Introduction

With the advent of computed tomography (CT) planning and conformal radiation techniques including intensity-modulated radiotherapy (IMRT), comes the prerequisite for accurate and consistent contouring of target volumes.

Conformal radiotherapy for anal cancer allows the ability to spare surrounding organs at risk (OAR). Normal tissues such as small bowel, femoral heads, perineum, and external genitalia often receive high doses of radiation with more conventional techniques, which can result in significant acute and late toxicity. The use of IMRT provides an opportunity to spare OAR and to reduce toxicity in anal cancer patients.

The implementation of IMRT requires a clear understanding of target volume definition for the complex elective nodal regions in anal cancer. During the early conduct of the Radiation Therapy Oncology Group (RTOG) 0529 Phase II study investigating IMRT for anal cancer, it became necessary to create an atlas because many initial target volumes submitted for quality assurance required contouring revision (1). However, this atlas provided contouring guidance for elective nodal volumes only and did not provide instruction in the contouring of gross disease and OAR.

As such, an international workshop was convened at the 2010 Australasian Gastrointestinal Trials Group (AGITG) annual meeting to develop detailed contouring and planning guidelines for the IMRT treatment of anal cancer, supplemented by a high-resolution atlas. This article reports the AGITG recommendations.

Section snippets

Methods and Materials

The AGITG is a national cooperative trials group that consists of radiation oncologists, surgeons, and medical oncologists who conduct clinical trials in gastrointestinal malignancies. In 2010, the Radiation Oncology Committee of AGITG organized a contouring workshop with member radiation oncologists to discuss radiotherapy target and OAR volume delineation for anal cancer, with the aim of developing consensus guidelines. Dr. Lisa Kachnic (L.K.), principal investigator of the RTOG 0529 study of

Elective nodal volumes

Mesorectum

The mesorectum is not well visualized on CT, and if fat-saturated T2 magnetic resonance imaging cannot be obtained, neighboring structures can be used to delineate this volume.

Cranial: The level of the recto-sigmoid junction; best identified where the rectum runs anteriorly to join the sigmoid colon (Atlas 4b).

Caudal: The ano-rectal junction, defined by where the levator muscles fuse with the external sphincter muscles, where mesorectal fat/space is no longer seen tapering inferiorly

Discussion

The implementation of IMRT in anal cancer requires accurate CT contouring of clinical target volumes. Roels et al. originally highlighted the need for guidelines in contour delineation in radiotherapy for rectal cancer (3). Subsequently, the RTOG released an atlas and guidelines for ano-rectal cancer that was driven by the need to improve contouring quality in the RTOG 0529 trial (2). With the early implementation of IMRT in Australia, the AGITG meeting provided a unique opportunity for GI

Conclusion

IMRT for anal cancer has significant potential to benefit patients. These detailed guidelines, supplemented with a high-resolution atlas, aim to improve the understanding of target volume definition and IMRT planning for anal cancer.

References (13)

L.A. Kachnic et al.
RTOG 0529: A phase II evaluation of dose-painted IMRT in combination with 5-fluorouracil and mitomycin-C for reduction of acute morbidity in carcinoma of the anal canal
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R.J. Myerson et al.
Elective clinical target volumes for conformal therapy in anorectal cancer: A Radiation Therapy Oncology Group consensus panel contouring atlas
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S. Roels et al.
Definition and delineation of the clinical target volume for rectal cancer
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J.J. Nuyttens et al.
The variability of the clinical target volume for rectal cancer due to internal organ motion during adjuvant treatment
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There are more references available in the full text version of this article.

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: Conflict of interest: none.

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Clinical InvestigationAustralasian Gastrointestinal Trials Group (AGITG) Contouring Atlas and Planning Guidelines for Intensity-Modulated Radiotherapy in Anal Cancer

Purpose

Methods and Materials

Results

Conclusion

Introduction

Section snippets

Methods and Materials

Elective nodal volumes

Discussion

Conclusion

Int J Radiat Oncol Biol Phys

Int J Radiat Oncol Biol Phys

Int J Radiat Oncol Biol Phys

Int J Radiat Oncol Biol Phys

Int J Radiat Oncol Biol Phys

Cancer Radiother

Clinical Investigation
Australasian Gastrointestinal Trials Group (AGITG) Contouring Atlas and Planning Guidelines for Intensity-Modulated Radiotherapy in Anal Cancer